ALBERT

Description: 〈p〉Publication date: August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Solar Energy, Volume 188〈/p〉 〈p〉Author(s): Naser Abdi, Yaser Abdi, Zahra Alemipour〈/p〉

Description: 〈p〉Publication date: August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Solar Energy, Volume 188〈/p〉 〈p〉Author(s): Smajil Halilovic, Jamie M. Bright, Wiebke Herzberg, Sven Killinger〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Knowledge of horizontal solar irradiance is crucial for the nowcasting and forecasting of generated photovoltaic (PV) power. High quality irradiance measurement devices, however, are typically not collocated with PV systems. The lack of measurements can be compensated by numerical weather models or satellite-derived products, but they provide only limited temporal and spatial resolutions. Another possibility is to directly use PV systems as irradiance sensors, since the measured PV power is a good indicator of incoming solar irradiance. The challenging part in this procedure is the computation of the global horizontal irradiance 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si233.svg"〉〈mrow〉〈msub〉〈mrow〉〈mi〉G〈/mi〉〈/mrow〉〈mrow〉〈mi〉h〈/mi〉〈/mrow〉〈/msub〉〈/mrow〉〈/math〉 from the global tilted irradiance 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si234.svg"〉〈mrow〉〈msub〉〈mrow〉〈mi〉G〈/mi〉〈/mrow〉〈mrow〉〈mi〉c〈/mi〉〈/mrow〉〈/msub〉〈/mrow〉〈/math〉, because a combination of decomposition and transposition models is not analytically invertible. Hence, the majority of existing solutions to this problem are numerical procedures. In this paper, an analytical approach to compute 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si235.svg"〉〈mrow〉〈msub〉〈mrow〉〈mi〉G〈/mi〉〈/mrow〉〈mrow〉〈mi〉h〈/mi〉〈/mrow〉〈/msub〉〈/mrow〉〈/math〉 from 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si236.svg"〉〈mrow〉〈msub〉〈mrow〉〈mi〉G〈/mi〉〈/mrow〉〈mrow〉〈mi〉c〈/mi〉〈/mrow〉〈/msub〉〈/mrow〉〈/math〉 is presented. The comparison of the proposed approach with one of the existing iterative (numerical) approaches shows promising results. When applied to 1-min data at four different locations, the new approach outperforms the iterative procedure by up to 9% in terms of the relative root mean square error (rRMSE) for east/west module’s orientations, and performs slightly better with the south orientation. Moreover, the new approach provides results in less than 1 s, whereas the iterative procedure requires more than 20 min for a one year of data. An open source R-script of the new approach is also publicly available and provided as supplementary material.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials, Volume 490〈/p〉 〈p〉Author(s): Ram Kumar, Jyoti Sharma, Kartik K. Iyer, E.V. Sampathkumaran〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉We report temperature (〈em〉T〈/em〉) dependence (2–300 K) of DC and AC magnetization (〈em〉M〈/em〉), isothermal remnant magnetization (〈em〉M〈sub〉IRM〈/sub〉〈/em〉), heat-capacity (〈em〉C〈/em〉), electrical resistivity (ρ), and magnetoresistance (MR) of a ternary intermetallic compound, Gd〈sub〉4〈/sub〉PtAl, crystallizing in a cubic (space group 〈em〉F〈/em〉〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si1.svg"〉〈mrow〉〈mover〉〈mn〉4〈/mn〉〈mo〉-〈/mo〉〈/mover〉〈/mrow〉〈/math〉3〈em〉m〈/em〉) structure. In this structure, there are three sites for the rare-earth. The magnetization data reveal that, in addition to a magnetic transition at 64 K, there is another magnetic feature below 20 K. The 〈em〉C〈/em〉(〈em〉T〈/em〉) data reveal an upturn below 64 K, shifting to a lower temperature with increasing field, which establishes that the onset of magnetic order is of an antiferromagnetic type. However, there is no worthwhile feature near 20 K in the 〈em〉C(T)〈/em〉 curve. Ac susceptibility peak undergoes an observable change with frequency and, in particular the peak around 20 K gets suppressed with the application of a dc magnetic field; in addition, 〈em〉M〈sub〉IRM〈/sub〉〈/em〉 undergoes a slow decay with time and isothermal 〈em〉M〈/em〉 exhibits low-field hysteresis below 20 K only, which are typical of spin-glasses. The results overall suggest that this compound is a reentrant spin-glass in zero field. There are experimental signatures pointing to the existence of both antiferromagnetic and ferromagnetic components, competing with the variation of temperature and magnetic field, as a result of which electrical and magnetoresistance behaviors are peculiar. The results overall suggest that this compound exhibits interesting magnetic and transport properties.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials, Volume 490〈/p〉 〈p〉Author(s): N. Leuning, S. Steentjes, M. Heller, S. Korte-Kerzel, K. Hameyer〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In material models for the finite-element simulation of electrical machines and the preceding magnetic measurements, the magnetic anisotropy of non-grain oriented electrical steel is usually considered in an oversimplified way, if at all. The magnetization behavior between rolling and transverse direction is not linear and varies with magnetic polarization, a relation that comes in addition to the complexity of the effect. In this paper, the magnetization anisotropy of five industrial non-grain oriented electrical steels is measured with a 1-D single-sheet-tester. The results are evaluated and correlated to the crystallographic texture of the studied materials. An approach to model magnetization curves at 50 Hz in arbitrary directions of the sheet plane is presented. The model is parametrized by measured magnetization curves along three different spatial directions and by macro-texture data in form of an orientation distribution function. This approach leads to a model that replicates the crossing of magnetization curves of different orientations with adequate quantitative accuracy for the application in FE magnetic field simulations.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials, Volume 490〈/p〉 〈p〉Author(s): E. Saavedra, J. Escrig, J.L. Palma〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The magnetization reversal process of interconnected pentagonal spin ice systems was investigated using micromagnetic simulations and experimental measurements. Five different systems were investigated, beginning with the interconnected Shakti lattice and introducing deformations with the idea of obtaining pentagonal tiling (belonging to the P4 group) until reaching an interconnected square lattice. In all pentagonal lattices, ferromagnetic domains are pinned, acting as isolated domains in an antiferromagnetic lattice, with Cairo tiling being the lattice that allows pinning more domains. Experimental measurements on a Cairo lattice of larger dimensions show that the shape of the hysteresis curve is invariant to the size of the bars that make up the interconnected pentagonal spin ice systems.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Solar Energy, Volume 188〈/p〉 〈p〉Author(s): Dazhi Yang〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Previously in “SolarData: An R package for easy access of publicly available solar datasets” [Sol. Energy 171 (2017) A3–A12], the R package 〈code〉SolarData〈/code〉 was built for easy access of five publicly available solar datasets. In this update, code for reading data from the Baseline Surface Radiation Network (BSRN), the largest research-grade solar radiation monitoring network, is added to the package. BSRN comprises 66 stations (as of 2019-02) around the globe, which collect 1-min or 3-min radiation data since 1992. These data are stored in the so-called “station-to-archive” files, each containing records from one month and one station, and can be downloaded via ftp. The functions in 〈code〉SolarData v1.1〈/code〉 directly interact with these station-to-archive files, without using the BSRN-Toolbox. It should however be noted that 〈code〉SolarData〈/code〉 is not a replacement of BSRN-Toolbox. Instead, it gives R users improved accessibility and freedom in BSRN data manipulation. Like the previous release, all contents herein described are made available on GitHub.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 European Polymer Journal, Volume 118〈/p〉 〈p〉Author(s): Payam Mokhtari, Mehrorang Ghaedi〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In this study, facile and green method for synthesis of imprinted material was introduced which subsequently applied for efficient delivery of Riboflavin (vitamin B〈sub〉2〈/sub〉). Characterization of the prepared polymer was carried out by the Fourier Transform Infrared (FT-IR) spectroscopy and Scanning Electron Microscopy (SEM). The weight ratio of functional monomer to template over 5–20 W/W% was evaluated in order to find the best loading condition and subsequent release into synthetic biomimetic media namely simulated body fluid (SBF) and media including 1% NaCl solution, simulated gastric fluid (SGF) solution at pH 1.5 and the solution of 1% W/W Na〈sub〉2〈/sub〉SO〈sub〉4〈/sub〉. Under optimized condition, the highest value of released riboflavin was achieved at 1:20 ratio of riboflavin to polymer in NaCl (55.07%) media which providing that the body requirement about 5 days of this vitamin between minimum effective concentration (MEC) and maximum safe concentration (MSC) of Riboflavin in short release time (45 min). Moreover, the experimental data were fitted to Higuchi model in order to calculate Higuchi solubility constant.〈/p〉〈/div〉 〈/div〉 〈div xml:lang="en"〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S001430571930518X-ga1.jpg" width="367" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 European Polymer Journal, Volume 118〈/p〉 〈p〉Author(s): Marcin Mackiewicz, Jan Romanski, Pamela Krug, Maciej Mazur, Zbigniew Stojek, Marcin Karbarz〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Nanogels are promising carriers for drug delivery, especially when they degrade under conditions typical for cancer cells to release a drug. By using the precipitation polymerization we synthesized a biocompatible and degradable nanogel based on poly(ethylene glycol) methyl ether methacrylate (OEGMA) and di(ethylene glycol) methyl ether methacrylate (MEO〈sub〉2〈/sub〉MA) cross-linked with a redox-sensitive linker, 〈em〉N,N′〈/em〉-bis(methacryloyl)cystine – (mBISS). The application of appropriate proportions of monomers during the nanogel synthesis allowed us to set its volume-phase-transition temperature to the body temperature while the aggregation of the nanogel in physiological conditions was eliminated. The presence of carboxylic groups in mBISS made the nanogel sensitive to pH, gave it stability under conditions of high ionic strength and allowed it to bind the anticancer drug – doxorubicin (DOX). The degradation of nanogel was examined by using electron microscopies. In the presence of a high concentration of glutathione (a reducing agent for the -S-S- bridges) which is the case for most cancer cells, the spherical shape of the nanogel and correspondingly its structure were destroyed. The obtained profiles for the release of DOX from the nanogel revealed that the smallest amount of DOX was released from the nanogel at pH 7.4, while under conditions present in most cancer cells, this is at pH 5.0 and c〈sub〉GSH〈/sub〉 = 40 mM, the highest cumulative release of DOX was observed. The DOX loaded nanogels were cytotoxic against MCF-27 and HT-29 cancer cells similarly to DOX alone. The unloaded gel nanoparticles did not inhibit proliferation of the cells.〈/p〉〈/div〉 〈/div〉 〈div xml:lang="en"〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0014305719306299-ga1.jpg" width="498" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 European Polymer Journal, Volume 118〈/p〉 〈p〉Author(s): Andrea Dodero, Lara Pianella, Silvia Vicini, Marina Alloisio, Massimo Ottonelli, Maila Castellano〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Alginate-based hydrogels can be obtained by the simple addition of bivalent ions to aqueous polysaccharide solutions without the use of toxic chemicals; however, the hydrogels prepared by this way result inhomogeneous and irreproducible due to the extremely fast crosslinking reaction. To overcome such limitations, in the present work a novel preparation approach is proposed and optimized; the method is based on the use of agar moulds rich of bivalent ions as diffusing system to modulate the release of Ca〈sup〉2+〈/sup〉, Sr〈sup〉2+〈/sup〉, and Ba〈sup〉2+〈/sup〉 cations in order to guarantee a better control of the crosslinking process. A full factorial experimental design was applied to assess the effects and the mutual interactions of three selected parameters (sodium alginate concentration, crosslinking agent concentration within the agar moulds, crosslinking time) on the gelation process. The swelling and mechanical properties of the prepared hydrogels were investigated both in deionized water and in a saline environment; furthermore, the hydrogels were characterized by means of thermogravimetric analysis and field-emission scanning electron microscopy. The obtained results demonstrated that both the experimental variables and the environmental conditions have a significant influence on the structure and the performances of the resulting hydrogels. In particular, the use of high polymer concentration and crosslinking agent amount leads to strong hydrogels corresponding to a superior crosslinking degree; more in detail, Ba〈sup〉2+〈/sup〉 ions show a great affinity for alginate leading to the hydrogels with the highest mechanical properties. Moreover, the ion-exchange occurring in saline environment seems to strongly reduce the effective crosslinking degree of alginate hydrogels with a consequential loss of mechanical properties and stability. The collected data were finally elaborated through statistical analysis combined with response surface methodology to develop theoretical models successfully able to correlate the crosslinking degree to the experimental conditions, thus opening the way of designing and fabricating alginate-based hydrogels with tailored morphology and mechanical properties.〈/p〉〈/div〉 〈/div〉 〈div xml:lang="en"〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0014305719306986-ga1.jpg" width="370" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Solar Energy, Volume 188〈/p〉 〈p〉Author(s): B. Sri Revathi, Prabhakar Mahalingam, Francisco Gonzalez-Longatt〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In this paper, a novel non-isolated DC-DC converter topology is proposed for solar photovoltaic (PV) application. The proposed converter is constructed from an interleaved boost converter (IBC) to reduce the input current ripple. Voltage gain is extended by (i) using voltage lift technique, (ii) replacing the conventional inductors of the IBC by coupled inductors (CIs) with appropriate turns ratio and (iii) connecting a voltage multiplier cell (VMC) across the secondary windings of the CIs. As the voltage gain is extended mainly at the secondary side of the CIs, the switches are subjected to low voltage stress which is only 12.63% of the output voltage. The converter yields a high voltage conversion ratio of 15.83. Experimental results obtained from a 24 V/380 V, 225 W prototype converter operating at 91.6% efficiency serves as a proof of the presented concept which has been employed to achieve high voltage conversion ratio (15.83) with low input current ripple (20%).〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Solar Energy, Volume 188〈/p〉 〈p〉Author(s): Sebastian Müller, Federico Giovannetti, Rolf Reineke-Koch, Oliver Kastner, Bernd Hafner〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉We present a comparative simulative study to evaluate the efficiency and stagnation behavior of commercially available absorber coatings for solar thermal flat-plate collectors. A market survey has revealed different absorber coatings, which exhibit solar absorptances of α 〉 90% and thermal emittances ε of 5–90%. All these coatings can be classified as wet-chemically electroplated coatings on the basis of black chrome, highly selective sputtered PVD coatings, solar paints and novel thermochromic coatings. We calculated the annual solar collector energy output by means of collector simulations with the tool ScenoCalc and compared the collector efficiency of several absorber coatings. We have carried out TRNSYS simulations both with systems for solar domestic hot water preparation and solar-assisted space heating. In a solar domestic hot water system with a daily tapping volume of 100 L we report an increase in the auxiliary energy demand of up to 6% with black chrome, 7% with thermochromic and 21% with solar paint coatings compared to sputtered PVD coatings. In a solar combisystem the increase in the auxiliary energy demand does not exceed 1.4% for thermochromic and black chrome coatings and 6.1% for solar paints. The stagnation period can be reduced from 178 h per year (PVD coatings) to 118 h, 62 h and 11 h for black chrome, thermochromic and solar paint coatings, respectively. The maximum absorber temperatures decrease from 175 °C (PVD coatings) to 165 °C for black chrome, 145 °C for thermochromic and 135 °C for solar paint coatings.〈/p〉〈/div〉 〈/div〉 〈div xml:lang="en"〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0038092X19306383-ga1.jpg" width="493" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Solar Energy, Volume 188〈/p〉 〈p〉Author(s): S. Marikkani, J. Vinoth Kumar, V. Muthuraj〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In past days, the occurrence of toxic heavy metal ions into the water and soil environment causes a major health risk to the living organisms. In this work, we mainly focused on the photoreduction of hexavalent chromium (Cr〈sup〉6+〈/sup〉) using novel sponge-like Fe〈sub〉2〈/sub〉V〈sub〉4〈/sub〉O〈sub〉13〈/sub〉 photocatalyst under visible light irradiation. The sponge-like Fe〈sub〉2〈/sub〉V〈sub〉4〈/sub〉O〈sub〉13〈/sub〉 was tailored through hydrothermal process using ferric chloride and sodium metavanadate precursors without the addition of any templates. The surface morphology, elemental analysis and various physical properties are characterized by numerous spectroscopic techniques. Interestingly, the sponge-like Fe〈sub〉2〈/sub〉V〈sub〉4〈/sub〉O〈sub〉13〈/sub〉 demonstrated proficient photocatalytic performances towards the reduction of Cr〈sup〉6+〈/sup〉 into Cr〈sup〉3+〈/sup〉. The obtained UV–visible spectroscopy results portrayed that sponge-like Fe〈sub〉2〈/sub〉V〈sub〉4〈/sub〉O〈sub〉13〈/sub〉 could reduce above of Cr〈sup〉6+〈/sup〉 solution within 40 min. The effect of operational reaction parameters such as catalyst dosage, initial Cr〈sup〉6+〈/sup〉 concentration and pH of the solution was optimized. Moreover, the sponge-like Fe〈sub〉2〈/sub〉V〈sub〉4〈/sub〉O〈sub〉13〈/sub〉 holds very good stability even after five consecutive cycles. This study could open new insights for the design novel nanostructured binary metal oxides for environmental applications.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Solar Energy, Volume 188〈/p〉 〈p〉Author(s): Muhammad Qamaruddin, Ibrahim Khan, Oluwole Olagoke Ajumobi, Saheed Adewale Ganiyu, Ahsanulhaq Qurashi〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In this work the synthesis of sulfur-doped cerium-titania based nanocomposites is carried out for photoelectrochemical (PEC) water splitting applications. Pristine ceria (CeO〈sub〉2〈/sub〉), titania (TiO〈sub〉2〈/sub〉) and S-CeTiO〈sub〉4−x〈/sub〉 nanohybrid have been synthesized via facile hydrothermal technique. Additionally, sulfur doping is performed at 350 °C to achieve sulfidized-CeTiO〈sub〉4−x〈/sub〉 (S-CeTiO〈sub〉4−x〈/sub〉) nanohybrid with improved optoelectronic properties. The energy disperse x-ray spectrometer (EDS) spectra and elemental mapping of S-CeTiO〈sub〉4−x〈/sub〉 showed the presence of sulfur. The X-Ray Photoelectron Spectroscopy (XPS) and X-ray diffraction (XRD) analysis further confirm sulfur doping and composite formation. Additionally, the XRD patterns of S-CeTiO〈sub〉4−x〈/sub〉 suggest the anatase phase of TiO〈sub〉2〈/sub〉, which is slightly mitigated with sulfidation. The Brunauer–Emmett–Teller (BET) isotherms indicate the average pore size decreases from 20.82 nm to 18.35 nm after sulfidation, which confirms successful sulfur incorporation in the pores. The Kubelka-Munk plots acquired from UV/Vis-diffuse reflectance spectroscopy (DRS) displayed a substantial red shift in the bandgap with sulfidization from 3.00 eV to 2.50 eV. The photoelectrochemical (PEC) water splitting of S-CeTiO〈sub〉4−x〈/sub〉 photoanode in terms of photocurrent density suggesting more than 3-times increase as compared to pristine TiO〈sub〉2〈/sub〉 nanoparticles. These results affirm the photoelctrocatalytic nature of ceria-based nanostructures for PEC water splitting.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Solar Energy, Volume 188〈/p〉 〈p〉Author(s): Seung-Ho Yoo〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The solar architecture is defined as a kind of building integrated photovoltaic (BIPV) which the Photovoltaic (PV) modules are deployed to passive solar concepts, to minimize the heating & cooling load, to upgrade the indoor environmental quality and to be adjustable for regional weather and to continuously succeed architectural culture and history. The most ideal form of a BIPV is a multi-functional and ecological convergence through a passive concept application of a photovoltaic module for a building. The solar architecture needs to consider the architectural culture and history of the region through an ecological convergence which is applicable to a passive concept if the environment, energy and comfort problems will be effectively mitigated. The evaluation standard is needed to fulfill these requirements of solar architecture. The renewable energy sources are getting very hot issues, due to the environmental pollution, global warming, and energy shortage, etc. It is reasonable to disseminate the representative energy systems which could be ecologically convergent with the regional architecture. Most renewable energy systems including PV could not be activate or not be environmentally friendly if the systems are planned simply without multi-functional and ecological convergence. This paper describes the ecological criteria to optimize solar architecture through an ecological convergence of a passive solar architecture and photovoltaic system.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Solar Energy, Volume 188〈/p〉 〈p〉Author(s): L. Salgado-Conrado, Areli Lopez-Montelongo〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In this study, we identify and describe the barriers that limit the installation of solar water heating (SWH) systems in Mexico and the manner in which the Mexican government has been working toward overcoming these challenges. Data regarding architectural, technical, economic, marketing, social, and political barriers were collected from official governmental publications, Mexican journals, and articles, and compared with results from similar research articles. Our results revealed that the governmental programmes have positively motivated the adoption of SWH systems. However, issues related to the structural conditions of buildings, low income, and access to water limit their use. Therefore, these issues should be included in the governmental strategies.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Solar Energy, Volume 188〈/p〉 〈p〉Author(s): Mahmood Mastani Joybari, Fariborz Haghighat, Saeid Seddegh, Yanping Yuan〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In this study, a method to track the melting front of phase change materials (PCMs) is developed under simultaneous charging and discharging (SCD) inside horizontal triplex tube heat exchangers. For SCD, the heat transfer mode of internal heating and external cooling is investigated. According to the heat transfer mechanism within the PCMs, two models of pure conduction (PC) and combined conduction and natural convection (CCNC) are developed and solved using ANSYS Fluent (version 17.2). Generally, during charging (i.e. melting), the buoyancy forces induce the liquid PCM to move upwards; therefore, the upper section of the storage is affected. However, this motion is limited during SCD due to the simultaneous cooling from the outer tube. Therefore, a front tracking method is developed assuming that natural convection only contributes melting to the upper section of the storage unit. On the other hand, it is assumed that the melting front for the lower section behaves similar to the PC model. In this study, three PCMs are used in three geometries to develop the correlations using two dimensionless numbers; i.e. liquid fraction of the PC model and the storage radius ratio. Another PCM is then used to verify the method. The correlations can provide results in the range of ±15% discrepancy.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Solar Energy, Volume 188〈/p〉 〈p〉Author(s): Mahmoud Samadpour, Hieng Kiat Jun, Parisa Parand, M.N. Najafi〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉 〈p〉Here we report a general study on the effect of various semiconductor sensitizers i.e. CdS, CdSe, CdS/CdSe, and PbS/CdS on the performance of quantum dot sensitized solar cells (QDSCs). The electron life time in the cells is investigated by applied bias voltage decay method. We clearly indicate that the electron life time could be considerably enhanced by CdS pre-deposition in CdS/CdSe QD sensitized cells.〈/p〉 〈p〉The charge transfer properties of cells are investigated by impedance spectroscopy and it is shown that a clear downward shift in TiO〈sub〉2〈/sub〉 conduction band take place through CdS QDs sensitizer pre-deposition. According to the results, type and the sequence of QDs deposition has a clear effect on the recombination resistance in cells. Here the efficiency of solar cells was improved to 3.63% by CdS pre-deposition which is more than 25% improvement in comparison to CdSe sensitized cells (2.84%). This general study indicates that tuning the sensitizer type can be systematically used in QDSCs to increase the electron life time and consequently the cells’ performance in a simple and cost effective way.〈/p〉 〈/div〉 〈/div〉

Description: 〈p〉Publication date: August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Solar Energy, Volume 188〈/p〉 〈p〉Author(s): Yu Xie, Manajit Sengupta, Chenxi Wang〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The Fast All-sky Radiation Model for Solar applications with Narrowband Irradiances on Tilted surfaces (FARMS-NIT) reported in Part I of this study is enhanced to include the requirements for cloudy-sky conditions. Surface radiances in 2002 narrow-wavelength bands from 0.28 to 4.0 μm are analytically computed by solving the radiative transfer equation for five independent photon paths accounting for clear-sky absorption, Rayleigh scattering, and cloud absorption and scattering. The Simple Model of the Atmospheric Radiative Transfer of Sunshine (SMARTS) is used to provide the optical thickness of the clear-sky atmosphere. Unlike Part I, which approximates the computation of aerosol scattering using the single-scattering phase function, the cloud transmittance and reflectance are efficiently retrieved from a comprehensive look-up table pre-computed by a 32-stream DIScrete Ordinates Radiative Transfer (DISORT) model for possible cloud conditions as well as solar and viewing geometries. A resolution analysis is performed to assess the optimal balance between the computational efficiency and accuracy in the development of the look-up table. Model simulations by DISORT and TMYSPEC are used to evaluate the performance of FARMS-NIT under cloudy-sky conditions. Compared to DISORT, FARMS-NIT yields 2–3% uncertainties on average, but it substantially reduces the computational time because of the independent computation of cloud properties and the implementation of the look-up table. In contrast to TMYSPEC, which uses successive steps to empirically compute plane-of-array (POA) irradiances and spectral irradiances, FARMS-NIT directly solves spectral radiances from the radiative transfer equation, which profoundly increases the accuracy in surface irradiances, especially over inclined photovoltaics (PV) panels.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials, Volume 490〈/p〉 〈p〉Author(s): H.X. Zeng, Q.X. Wang, J.S. Zhang, X.F. Liao, X.C. Zhong, H.Y. Yu, Z.W. Liu〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Different from many previous reports, La-Al-Cu alloys with different Al/Cu ratios containing only high abundant rare earth element La were employed for grain boundary diffusion treatment for sintered NdFeB permanent magnets. It is found that Al and Cu contents should be optimized to achieve coercivity enhancement. The coercivity of the magnet was enhanced from 1000 to 1006, 1077 and 1156 kA/m after La〈sub〉70〈/sub〉Al〈sub〉10〈/sub〉Cu〈sub〉20〈/sub〉, La〈sub〉70〈/sub〉Al〈sub〉15〈/sub〉Cu〈sub〉15〈/sub〉 and La〈sub〉70〈/sub〉Al〈sub〉20〈/sub〉Cu〈sub〉10〈/sub〉 alloys diffusion, at 800 °C for 1 h followed by 500 °C for 3 h. The coercivity stability was also improved, indicated by the enhanced temperature coefficient of β from −0.63 to −0.61, −0.61 and −0.60%/K. Microstructure investigation indicates that the formation of continuous grain boundary phase after diffusion reduces the magnetic exchange interaction and contributes to the enhanced coercivity. After diffusion, the La〈sub〉2〈/sub〉O〈sub〉3〈/sub〉 phase was observed in both the triple junction and strip grain boundary. La, Al and Cu elements showed different distributions in the magnets. The diffusion coefficients obtained from Fick’s second law indicate that La diffuses faster than Al and Cu at 800 °C, which explains the various effects of the diffusion sources and different coercivity enhancements by the alloys with different Al/Cu ratios. Although the process should be further optimized, the current results demonstrate that the grain boundary diffusion using low cost La-Al-Cu alloys can improve the microstructure and enhance the coercivity of NdFeB magnets.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Solar Energy, Volume 188〈/p〉 〈p〉Author(s): Sebastijan Seme, Klemen Sredenšek, Bojan Štumberger, Miralem Hadžiselimović〈/p〉

Description: 〈p〉Publication date: 15 September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Solar Energy, Volume 190〈/p〉 〈p〉Author(s): Fahad Mateen, Mumtaz Ali, Sae Youn Lee, Sung Hoon Jeong, Min Jae Ko, Sung-Kyu Hong〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In this study, we demonstrate the simultaneous use of carbon quantum dots and organic dyes as highly emissive luminescent material in high performance tandem luminescent solar concentrator (LSC). The top LSC layer is based on carbon quantum dots (CQDs), while the bottom one is based on organic dye. The role of förster resonance energy transfer (FRET) is demonstrated in organic dyes in a bottom LSC. Moreover, the CQDs layer which has the capability to harvest ultraviolet (UV) and near-UV photons acts as a protective layer to improve the photo-stability of the organic dyes contained in bottom waveguide. The electrical measurements showed that the optical conversion efficiency (η〈sub〉opt〈/sub〉) and power conversion efficiency (η〈sub〉PCE〈/sub〉) of CQDs based single LSC are 5.62% and 1.03% respectively. While, η〈sub〉opt〈/sub〉, and η〈sub〉PCE〈/sub〉 the dye-LSC are 13.42% and 2.72% respectively. However, in the tandem LSC, overall η〈sub〉opt〈/sub〉 and η〈sub〉PCE〈/sub〉 are 16.32% and 3.2% respectively. Our results showed that tandem structured CQDs and dye based luminescent solar concentrators make the practical use of LSCs more feasible because of the unique properties such as good photostability and high efficiency.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Solar Energy, Volume 190〈/p〉 〈p〉Author(s): Vladimir Potemkin, Nadezhda Palko, Maria Grishina〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Electronic properties of benzothiadiazole (BTD) unit containing dyes adsorbed on TiO〈sub〉2〈/sub〉 nano-particles have been estimated using Quantum Theory of Atoms in Molecules (QTAIM). We found that short circuit photocurrent density 〈em〉J〈sub〉sc〈/sub〉〈/em〉 and open circuit photovoltage 〈em〉V〈sub〉oc〈/sub〉〈/em〉 of the studied DSSCs are well related to the electronic properties of dyes, namely charges of BTD atomic basins of nitrogens, summary isodensity surface area and summary volume of hydrogen basins. Analysis of deviations of predicted and observed photovoltaic properties allowed to reveal device fabrication details influencing positively and negatively on device efficiency. Found relationships have been used for design of new promising dyes and recommendation of the better fabrication details of DSSCs with significantly higher photovoltaic properties as compared to the studied and published. For newly designed metal-free BTD-unit containing dyes, 〈em〉J〈sub〉sc〈/sub〉〈/em〉 is expected to reach 20.7–25.8 mA/cm〈sup〉2〈/sup〉, 〈em〉V〈sub〉oc〈/sub〉〈/em〉 – 0.858–1.029 V and power conversion efficiency 〈em〉η〈/em〉 – 10.6–16.3%.〈/p〉〈/div〉 〈/div〉 〈div xml:lang="en"〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0038092X1930828X-ga1.jpg" width="402" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Solar Energy, Volume 188〈/p〉 〈p〉Author(s): Christian Camus, Pascal Offermann, Martin Weissmann, Claudia Buerhop, Jens Hauch, Christoph J. Brabec〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉This work demonstrates the capability of meteorological reanalysis data for estimating mechanical stresses due to wind gusts on photovoltaic modules. Besides the immediate power loss caused by the inactive solar cell areas within the module, the influence of cracks induced by such mechanical loads on the ageing and degradation behavior of PV modules is in the focus of current PV reliability research. To choose and/or design the optimum module for a given deployment site at the most economical cost, the mechanical loads the module will be exposed to during its service life need to be estimated. Hence, this paper introduces a new methodology for assessing and deducing site-specific mechanical load scenarios which are expected to be imposed on photovoltaic modules by wind gusts for a given location. The approach presented here is based on the linear calibration of meteorological reanalysis data with publicly available and standardized high-quality surface weather station data of local weather services. In this fashion, site-specific mechanical load scenarios can be deduced for virtually any site covered by the respective reanalysis data set. These scenarios can be used for developing site-specific module qualification tests, thereby providing a methodology enabling climate-specific module designs or specifications. This methodology can also be transferred to virtually any location and other climate and weather parameters such as snow loads, UV dose, etc. Hence a complete assessment of all weather-related degradation scenarios could be deduced eventually.〈/p〉〈/div〉 〈/div〉 〈div xml:lang="en"〉 〈h5〉Graphical abstract〈/h5〉 〈div〉 〈p〉(a) Comparison of wind gust data collected at a DWD station in Dresden and data obtained from ERA interim and COSMO reanalysis data. (b) Electroluminescence image of a photovoltaic module damaged by mechanical loads. Black areas comprise electrically weakly connected areas which cannot contribute to power production anymore and result from the damage caused by the load. (c) Mechanical load set up at the ZAE Bayern, which can be used for simulating wind and snow loads with simultaneous detection of the generation and evolution of solar cell cracks in-situ by means of electroluminescence.〈/p〉 〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0038092X19306516-ga1.jpg" width="500" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉 〈/div〉 〈/div〉

Description: 〈p〉Publication date: August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Solar Energy, Volume 188〈/p〉 〈p〉Author(s): A.A. Yousefi, A.R. Mohebbi, S. Falahdoost Moghadam, S.A. Poursamar, L. Hao〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The present work, reports on combination of precise positioning ability of 3D printers with near field electro spinning (NFES) as a low-cost and scalable approach to generate well-aligned, evenly distributed microfiber mask upon flexible substrates coated with metal thin film. Using a combination of annealing thermal treatment and the wet chemical etching of metal layer a flexible transparent electrode is prepared. Using this high speed and large-area printing technique we can overcome the drawbacks of conventional electrospinning such as fiber structural inhomogeneity, random orientation, and non-reproducible results. In addition, the application of more complicated and expensive methods such as lithography or e-beam lithography or nanoimprint lithography can be avoided using this technique. The most important advantage of the reported fabrication method relative to electro-spinning process is the ability to have a special control on the distribution pattern of the electrodes on the surface which can lead to better control over the ratio of conductivity and transparency of the surface.〈/p〉〈/div〉 〈/div〉 〈div xml:lang="en"〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0038092X19306619-ga1.jpg" width="359" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 22 August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials〈/p〉 〈p〉Author(s): Chang-Wei Wu, Dao-Xin Yao〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Two-dimensional (2D) ferromagnetic semiconductors with robust magnetism are urgently desired for nanoscale spintronics applications. However, it remains a challenge to realize them experimentally. In this work, we proposed intriguing 2D p-orbital ferromagnetic semiconductors 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si29.svg"〉〈mrow〉〈msub〉〈mrow〉〈mi mathvariant="normal"〉X〈/mi〉〈/mrow〉〈mrow〉〈mn〉2〈/mn〉〈/mrow〉〈/msub〉〈msub〉〈mrow〉〈mi mathvariant="normal"〉NO〈/mi〉〈/mrow〉〈mrow〉〈mn〉2〈/mn〉〈/mrow〉〈/msub〉〈/mrow〉〈/math〉 (〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si30.svg"〉〈mrow〉〈mi〉X〈/mi〉〈mo〉=〈/mo〉〈mi mathvariant="italic"〉Ca〈/mi〉〈mo〉,〈/mo〉〈mi mathvariant="italic"〉Sr〈/mi〉〈/mrow〉〈/math〉) monolayer with 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si31.svg"〉〈mrow〉〈mn〉3〈/mn〉〈msub〉〈mrow〉〈mi〉μ〈/mi〉〈/mrow〉〈mrow〉〈mi〉B〈/mi〉〈/mrow〉〈/msub〉〈/mrow〉〈/math〉 magnet per unit under O surface termination using first-principles calculations. The 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si32.svg"〉〈mrow〉〈msub〉〈mrow〉〈mi mathvariant="normal"〉Ca〈/mi〉〈/mrow〉〈mrow〉〈mn〉2〈/mn〉〈/mrow〉〈/msub〉〈msub〉〈mrow〉〈mi mathvariant="normal"〉NO〈/mi〉〈/mrow〉〈mrow〉〈mn〉2〈/mn〉〈/mrow〉〈/msub〉〈/mrow〉〈/math〉 monolayer is bipolar magnetic material (BMS) with spin-flip gap 0.24 eV, and the 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si33.svg"〉〈mrow〉〈msub〉〈mrow〉〈mi mathvariant="normal"〉Sr〈/mi〉〈/mrow〉〈mrow〉〈mn〉2〈/mn〉〈/mrow〉〈/msub〉〈msub〉〈mrow〉〈mi mathvariant="normal"〉NO〈/mi〉〈/mrow〉〈mrow〉〈mn〉2〈/mn〉〈/mrow〉〈/msub〉〈/mrow〉〈/math〉 is half-semiconductor (HSC) with spin-flip gap 0.31 eV, which is large enough to prevent the spin-flip transition. The Curie temperature can reach to 206 and 239 K, respectively, due to the superexchange interaction between 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si34.svg"〉〈mrow〉〈msup〉〈mrow〉〈mi〉N〈/mi〉〈/mrow〉〈mrow〉〈mo〉-〈/mo〉〈/mrow〉〈/msup〉〈/mrow〉〈/math〉 ions. The values are much higher than the boiling point of liquid nitrogen (77 K) and comparable to that of the reported 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si35.svg"〉〈mrow〉〈mi mathvariant="normal"〉ScCl〈/mi〉〈/mrow〉〈/math〉 monolayer. Moreover, the half metals are obtained via carrier doping for both the 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si36.svg"〉〈mrow〉〈msub〉〈mrow〉〈mi mathvariant="normal"〉Ca〈/mi〉〈/mrow〉〈mrow〉〈mn〉2〈/mn〉〈/mrow〉〈/msub〉〈msub〉〈mrow〉〈mi mathvariant="normal"〉NO〈/mi〉〈/mrow〉〈mrow〉〈mn〉2〈/mn〉〈/mrow〉〈/msub〉〈/mrow〉〈/math〉 and 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si37.svg"〉〈mrow〉〈msub〉〈mrow〉〈mi mathvariant="normal"〉Sr〈/mi〉〈/mrow〉〈mrow〉〈mn〉2〈/mn〉〈/mrow〉〈/msub〉〈msub〉〈mrow〉〈mi mathvariant="normal"〉NO〈/mi〉〈/mrow〉〈mrow〉〈mn〉2〈/mn〉〈/mrow〉〈/msub〉〈/mrow〉〈/math〉 monolayers. In addition, the half-metallic completely spin-polarized direction of BMS 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si38.svg"〉〈mrow〉〈msub〉〈mrow〉〈mi mathvariant="normal"〉Ca〈/mi〉〈/mrow〉〈mrow〉〈mn〉2〈/mn〉〈/mrow〉〈/msub〉〈msub〉〈mrow〉〈mi mathvariant="normal"〉NO〈/mi〉〈/mrow〉〈mrow〉〈mn〉2〈/mn〉〈/mrow〉〈/msub〉〈/mrow〉〈/math〉 monolayer can be controlled by carrier doping type. Furthermore, the magnetism of 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si39.svg"〉〈mrow〉〈msub〉〈mrow〉〈mi mathvariant="normal"〉X〈/mi〉〈/mrow〉〈mrow〉〈mn〉2〈/mn〉〈/mrow〉〈/msub〉〈msub〉〈mrow〉〈mi mathvariant="normal"〉NO〈/mi〉〈/mrow〉〈mrow〉〈mn〉2〈/mn〉〈/mrow〉〈/msub〉〈/mrow〉〈/math〉 monolayer is derived from p orbital, without the involvement of conventional transition metals or rare earth atoms. This is advantageous for high-speed and long-distance spin-polarization transport. These results suggest that the 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si40.svg"〉〈mrow〉〈msub〉〈mrow〉〈mi mathvariant="normal"〉X〈/mi〉〈/mrow〉〈mrow〉〈mn〉2〈/mn〉〈/mrow〉〈/msub〉〈msub〉〈mrow〉〈mi mathvariant="normal"〉NO〈/mi〉〈/mrow〉〈mrow〉〈mn〉2〈/mn〉〈/mrow〉〈/msub〉〈/mrow〉〈/math〉 monolayer can develop spin field effect transistor for information processing and storage, and open opportunities for designing new ferromagnetic semiconductors.〈/p〉〈/div〉 〈/div〉 〈div xml:lang="en"〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0304885319322772-ga1.jpg" width="160" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 European Polymer Journal, Volume 119〈/p〉 〈p〉Author(s): Maria Toplishek, Ema Žagar, David Pahovnik〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉A synthetic approach to the dicyano-substituted ε-caprolactone was developed. It consists of a cyclohexanone ring assembly through the Diels-Alder reaction followed by the Baeyer-Villiger oxidation. Ring-opening polymerization of the synthesized monomer, catalyzed by the aluminum alkoxides, was performed in a well-controlled manner and provided the nitrile-polyester homopolymers of various molar masses. The synthesized nitrilePCL homopolymers are amorphous with a significantly higher glass transition temperature (66–69 °C) compared to the unsubstituted PCL. The dicyano-substituted ε-caprolactone monomer was copolymerized with the unsubstituted ε-caprolactone to prepare the statistical and block copolymers. Furthermore, the cyano groups of the nitrilePCL homopolymers were transformed into the amide groups by post-polymerization modification under anhydrous conditions using the Wilkinson’s catalyst. The resulting amide-functionalized polyesters are water-soluble when the degree of transformation is higher than 80%.〈/p〉〈/div〉 〈/div〉 〈div xml:lang="en"〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S001430571931225X-ga1.jpg" width="339" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 European Polymer Journal, Volume 119〈/p〉 〈p〉Author(s): Ander Reizabal, José Manuel Laza, José María Cuevas, Luis Manuel León, José Luis Vilas-Vilela〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Different polycyclooctene (PCO) and linear low-density polyethylene (LLDPE) blends were crosslinked with 2 wt% of dicumyl peroxide (DCP) in order to obtain thermoresponsive shape memory materials with transition temperatures close to bodýs external temperature. These polymeric blends allow tailoring properties by the synergic combination of shape-memory capability of PCO and effective mechanical and processing performance of polyethylene. Thermal stability of these materials was characterised by thermogravimetric analysis (TGA), whereas mechanical performance was measured by dynamic mechanical analysis (DMA) and tensile tests. Besides, thermal properties were measured by differential scanning calorimetry (DSC), where the melting temperature of crystalline PCO phase around 40–50 °C were observed. Considering this shape memory triggering temperature, the shape memory capabilities of the samples were studied by thermo-mechanical analysis (TMA), and outstanding shape recovery ratios were obtained. Finally, water contact angle (WCA) and water vapour transmission rate (WVTR) were measured above and below that transition temperature to assess moisture permeability changes. In this case, observed increase by an order of magnitude in vapour permeability with temperature offers promising opportunities in developing thermo-active membranes for textile applications with these PCO-LLDPE blends.〈/p〉〈/div〉 〈/div〉 〈div xml:lang="en"〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0014305719309899-ga1.jpg" width="365" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Solar Energy, Volume 190〈/p〉 〈p〉Author(s): R. Fazai, K. Abodayeh, M. Mansouri, M. Trabelsi, H. Nounou, M. Nounou, G.E. Georghiou〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In this paper, we consider a machine learning approach merged with statistical testing hypothesis for enhanced fault detection performance in photovoltaic (PV) systems. The developed method makes use of a machine learning based Gaussian process regression (GPR) technique as a modeling framework, while a generalized likelihood ratio test (GLRT) chart is applied to detect PV system faults. The developed GPR-based GLRT approach is assessed using simulated and real PV data through monitoring the key PV system variables (current, voltage, and power). The computation time, missed detection rate (MDR), and false alarm rate (FAR) are computed to evaluate the fault detection performance of the proposed approach.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Solar Energy, Volume 190〈/p〉 〈p〉Author(s): Zhiyong Liu, Ning Wang, Weiliang Zheng〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉One of the challenges facing the fabrication of high-performance conventional structure polymer solar cells (PSCs) is the development of new interface materials that have better air stability and charge carrier collection and transport ability. In this study, the mixture thin films of polyethylenimine ethoxylated (PEIE) and TiO〈sub〉X〈/sub〉 are developed as the electron extraction layer (EEL) and Ag as the cathode for the application in PSCs, replacing the Ca/Al composite cathode. Ultraviolet photoelectron spectroscopy (UPS) and space-charge-limited current (SCLC) measurements demonstrate that PEIE:TiO〈sub〉X〈/sub〉/Ag shows appropriate energy levels, substantially reduced barrier potential, weakened charge carrier recombination and enhanced electron mobility. As a result, the PEIE:TiO〈sub〉X〈/sub〉-based PSCs demonstrate not only an enhanced power conversion efficiency (PCE) of 10.94% but also the photovoltaic performance insensitive to the storage time, yielding an aged PCE that is 92% of the fresh PCE. This result can be further explained by the dependence of the charge carrier mobility on storage time. Our work suggests exploiting the PEIE:TiO〈sub〉X〈/sub〉/Ag composite thin films as the composite cathode replacing Ca/Al thin films for successfully enhancing the photovoltaic performance and improving the stability of PSCs.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Solar Energy, Volume 190〈/p〉 〈p〉Author(s): Ahmad Azmin Mohamad〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The electrolyte is a critical component of dye-sensitised solar cells (DSSCs). Among them, quasi-solid state (QSS) electrolytes are considered as one of the most prospective substitutes for liquid electrolytes to DSSCs. To entirely understand and optimise the performance and stability of QSS, comprehensive characterisation is needed to design new materials, comprehend and optimise the QSS. This review summarises the characterisations of QSS beginning from 2010. Emphasis is placed on the physical characterisations such as viscosity, morphology, thermal, infrared spectroscopy, nuclear magnetic resonance, Raman, ultraviolet-visible, and X-ray diffraction. All parts of the characterisation process are divided into the introduction, the objective of testing, main outcomes and finally, the selected examples. A summary of recent and important measurements on QSS are mentioned at the end.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Solar Energy, Volume 190〈/p〉 〈p〉Author(s): Shuijia Li, Wenyin Gong, Xuesong Yan, Chengyu Hu, Danyu Bai, Ling Wang〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Parameter estimation of photovoltaic (PV) models plays an important role in the simulation, evaluation, and control of PV systems. In the past decade, although many meta-heuristic methods have been devoted to parameter estimation of PV models and achieved satisfactory results, they may suffer from consuming large computational resources to get promising performance. In order to fast and accurately estimate the parameters of PV models, in this paper, a memetic adaptive differential evolution, namely MADE, is developed. The proposed MADE can be featured as: (i) the success-history based adaptive differential evolution is used for the global search; (ii) the Nelder-Mead simplex method is employed for the local search to refine the solution; and (iii) the ranking-based elimination strategy is proposed to maintain the promising solutions in the external archive. To verify the performance of our approach, it is applied to estimate the unknown parameters of different PV models, 〈em〉i.e.,〈/em〉 the single diode model, the double diode model, and the PV module. Experimental results obtained by MADE are compared with several state-of-the-art methods reported in the literature. Comparison analysis demonstrates that the proposed MADE exhibits remarkable performance on accuracy and reliability. It also consumes less computational resources than other compared methods.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Solar Energy, Volume 188〈/p〉 〈p〉Author(s): Hyeon-Seok Lee, Bongkoo Kang, Wook-Sung Kim, Sang-Jin Yoon〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉This paper describes a boost half-bridge DC-DC converter for photovoltaic system that reduces the input voltage and current ripples by using a 1:1 transformer and an auxiliary capacitor. The 1:1 transformer replaces the boost inductor in a previous boost half-bridge converter. The auxiliary capacitor is connected serially to the secondary coil of the 1:1 transformer, and resonates with the leakage inductance of the 1:1 transformer. The input voltage and current ripples are reduced by setting the switching frequency equal to the resonance frequency between the auxiliary capacitor and the leakage inductance, and by coupling the resonance current to the primary coil of the 1:1 transformer. The proposed converter had input voltage ripple less than 0.2 V〈sub〉p.p〈/sub〉, input current ripple less than 0.81 A〈sub〉p.p〈/sub〉, and power-conversion efficiency higher than 94.5% when the converter was operated at input voltage of 30–50 V, output voltage of 400 V, output power of 30–300 W, and switching frequency of 46 kHz. These experimental results show that the proposed converter is well suited for photovoltaic micro-inverter applications that require a small input capacitor, low input voltage, high input current, high output voltage, and high power-conversion efficiency.〈/p〉〈/div〉 〈/div〉 〈div xml:lang="en"〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0038092X19306450-ga1.jpg" width="284" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Solar Energy, Volume 188〈/p〉 〈p〉Author(s): Mohammad A. Alim, Zhong Tao, Md Kamrul Hassan, Ataur Rahman, Baolin Wang, Chunwei Zhang, Bijan Samali〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Buildings consume a large quantity of energy. In May 2010, the European Union (EU) reported that around 40% of their energy consumption was related to building sectors, which is similar to the proportion of 39% in the United States. In Australia, buildings count 20% of its total energy consumption. Experts across the globe have been working in the development of new technologies, which not only reduce the building energy consumption but also harness energy from renewable sources. Building integrated photovoltaic (BIPV) system is one of the most popular techniques towards constructing a net-zero energy building through the utilisation of solar energy. In this review, we focus on the BIPV applications in Australia, where BIPV has not been prevailed as widely as might be expected despite the high solar irradiation in the country. This paper discusses recent advancements in BIPV systems and challenges that Australia is facing in order to adopt this technology. In addition, the current carbon emission issues in Australia are presented to build awareness among people, which will contribute towards adopting this technology. A range of experimental and numerical studies have been reviewed to identify the effectiveness of BIPV on building performances. This study also reports on the sustainability and economic feasibility of BIPV systems in terms of energy payback time and economical payback time, respectively. Based on this review, it is argued that BIPV is technically and economically feasible for Australia and its implementation might be started with solar roof tiles.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 January 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials, Volume 493〈/p〉 〈p〉Author(s): Chicheng Ma, Kai Liu, Xingqi Han, Sheng Yang, Nan Ye, Jiancheng Tang〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The martensitic transformation (MT) and magnetocaloric properties are investigated in melt-spun Mn〈sub〉50〈/sub〉Ni〈sub〉31.5〈/sub〉Co〈sub〉8.5〈/sub〉Ti〈sub〉10〈/sub〉 all-3〈em〉d〈/em〉-metal alloy ribbons fabricated at different wheel speeds (WSs), 15, 20, and 25 m/s. All these ribbon samples reveal a coexistence of the predominant 5-layer modulated (5 M) (monoclinic, space group 〈em〉P〈/em〉2/〈em〉m〈/em〉) martensite and a small amount of non-modulated (NM) 〈em〉L〈/em〉1〈sub〉0〈/sub〉 structure (tetragonal, space group 〈em〉P〈/em〉4/〈em〉mmm〈/em〉) martensite at room temperature (RT), implying the MT temperature is above RT. With the increase of WSs from 15 to 25 m/s, the structural and magnetic parameters, such as average grain size, unit cell volume, MT temperature, and magnetic entropy change, decrease. However, it is worth noting that from 20 to 25 m/s, the reduction becomes much more sluggish or even almost stagnate in comparison with that from 15 to 20 m/s. Large effective refrigeration capacity ~79.4 J kg〈sup〉−1〈/sup〉 is obtained in sample with 20 m/s under 〈em〉μ〈/em〉〈sub〉0〈/sub〉Δ〈em〉H〈/em〉 = 0–5 T, indicating that these ribbons could be the potential candidate for magnetic refrigeration. The origins of manipulation in MT by WSs in these ribbon samples are discussed.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 January 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials, Volume 493〈/p〉 〈p〉Author(s): Xiao Zhou, Ruirui Liu, Haitao Zhou〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The microstructures and soft magnetic properties of Co〈sub〉66〈/sub〉Fe〈sub〉4〈/sub〉Mo〈sub〉2〈/sub〉Si〈sub〉16〈/sub〉B〈sub〉12〈/sub〉 amorphous tape wound core were systematically investigated. The phase composition and corresponding structure evaluation of Co〈sub〉66〈/sub〉Fe〈sub〉4〈/sub〉Mo〈sub〉2〈/sub〉Si〈sub〉16〈/sub〉B〈sub〉12〈/sub〉 amorphous ribbon after annealing at various temperatures were identified firstly. In particular, at 758 K the microstructure of the ribbon is primarily composed of Co〈sub〉2〈/sub〉B, Fe〈sub〉2〈/sub〉B and β-Co phases. With the temperature approaching to 768 K, the new phases α-Co and CoSi appears. When the temperature increases to 778 K, the mixed phase combination of α(Co) + β(Co) + Co〈sub〉2〈/sub〉B + Fe〈sub〉2〈/sub〉B + CoSi exists along with an apparent nano-crystallization. The soft magnetic properties of tape wound core assembled by Co〈sub〉66〈/sub〉Fe〈sub〉4〈/sub〉Mo〈sub〉2〈/sub〉Si〈sub〉16〈/sub〉B〈sub〉12〈/sub〉 amorphous ribbon were then studied at annealed temperature from 713 K to 753 K. At 723 K, we found the permeability is highest with a maximum value of 〈em〉μ〈sub〉m〈/sub〉〈/em〉 = 1.675 × 10〈sup〉3〈/sup〉, and the coercive force is lowest with a minimum value of 0.134 Oe. The magnetization curve and the hysteresis loop of established tape would core annealed at 713–753 K remain almost unchanged. Finally, the relation between frequency and magnetic permeability and quality factor were carefully examined at different annealing temperatures.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 21 August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials〈/p〉 〈p〉Author(s): Rihab Jabbar, Sabah H. Sabeeh, Awham M. Hameed〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Manganese (Mn〈sup〉+2〈/sup〉) doped spinel cobalt ferrites nanoparticles (NPs) having composition (Mn〈sub〉x〈/sub〉Co〈sub〉1-x〈/sub〉Fe〈sub〉2〈/sub〉O〈sub〉4〈/sub〉 where x = 0.2, 0.4, 0.6 and 0.8) were synthesized by sol-gel precipitation method. The structural, dielectric and magnetic properties were characterized via X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), LCR meter, and vibrating sample magnetometer (VSM). The average crystallite size (D) was found to increase from 10.79 nm to 14.18 nm with increasing the Mn〈sup〉+2〈/sup〉 doping ratio from (0.2 to 0.6) then decrease to 9.95 nm with further increasing of Mn〈sup〉+2〈/sup〉 to (0.8). FTIR spectrum confirmed the formation of the spinal structure of ferrite, where the main observed bands (416.64 – 459.07 cm〈sup〉-1〈/sup〉) assigned to the octahedral complexes and (513.08 – 574.81 cm〈sup〉-1〈/sup〉) assigned to tetrahedral complexes. The dielectric properties of samples found to be decreased with increasing the doping ratio. While the hysteresis loop obtains from VSM indicated the formation of soft magnetic material and the saturation magnetization decrease from 56 emu g〈sup〉-1〈/sup〉 (Mn〈sup〉+2〈/sup〉 = 0.2) to 38 emu g〈sup〉-1〈/sup〉 (Mn〈sup〉+2〈/sup〉 = 0.8).〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 European Polymer Journal, Volume 119〈/p〉 〈p〉Author(s): Busra Tugce Duymaz, Fatma Betul Erdiler, Tugba Alan, Mehmet Onur Aydogdu, Ahmet Talat Inan, Nazmi Ekren, Muhammet Uzun, Yesim Muge Sahin, Erdi Bulus, Faik Nüzhet Oktar, Sinem Selvin Selvi, Ebru ToksoyOner, Osman Kilic, Muge Sennaroglu Bostan, Mehmet Sayip Eroglu, Oguzhan Gunduz〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Poly(ε-caprolactone) (PCL), gelatin (GT) and different concentrations of low molecular weight 〈em〉Halomonas〈/em〉 levan (HLh) were combined and examined to develop physical networks serving as tissue scaffolds to promote cell adhesion for biocompatibility. Three-dimensional bioprinting technique (3D bioprinting) was employed during manufacturing the test samples and their comprehensive characterization was performed to investigate the physicochemical properties and biocompatibility. Physical properties of the printing materials such as viscosity, surface tension, and density were measured to determine optimal parameters for 3D bioprinting. The scanning electron microscope (SEM) was used to observe the morphological structure of scaffolds. Fourier-Transform Infrared Spectroscopy (FT-IR) and differential scanning calorimetry (DSC) were used to identify the interactions between the components. 〈em〉In-vitro〈/em〉 cell culture assays using standard human osteoblast (Hob) cells showed increased biocompatibility of the printing materials with increasing HLh content. Thus, the formulations including the HLh are expected to be a good candidate for the production of 3D printed materials.〈/p〉〈/div〉 〈/div〉 〈div xml:lang="en"〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0014305719313862-ga1.jpg" width="500" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 European Polymer Journal, Volume 119〈/p〉 〈p〉Author(s): Maria A. Murcia Valderrama, Robert-Jan van Putten, Gert-Jan M. Gruter〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉 〈p〉Plastic materials are indispensable in everyday life because of their versatility, high durability, lightness and cost-effectiveness. As a consequence, worldwide plastic consumption will continue to grow from around 350 million metric tons per annum today to an estimated 1 billion metric tons per annum in 2050. For applications where polymers are applied in the environment or for applications where polymers have a bigger chance of ending up in the environment, (bio)degradable polymers need to be developed to stop endless accumulation of non-degradable polymers irreversibly littering our planet.〈/p〉 〈p〉As monomers and polymers represent more than 80% of the chemical industry’s total production volume, a transition from fossil feedstock today (99% of the current feedstock for polymers is fossil-based) to a significantly larger percentage of renewable feedstock in the future (carbon that is already “above the ground”) will be required to meet the greenhouse gas reduction targets of the Paris Agreement (〉80% CO〈sub〉2〈/sub〉 reduction target for the European Chemical Industry sector in 2050).〈/p〉 〈p〉The combination of the predicted polymer market growth and the emergence of new feedstocks creates a fantastic opportunity for novel sustainable polymers. To replace fossil based feedstock, there are only three sustainable alternative sources: biomass, CO〈sub〉2〈/sub〉 and existing plastics (via recycling). The ultimate circular feedstock would be CO〈sub〉2〈/sub〉: it can be electrochemically reduced to formic acid derivatives that can subsequently be converted into useful monomers such as glycolic acid and oxalic acid. In order to assess the future potential for these polyester building blocks, we will review the current field of polyesters based on these two monomers. Representative synthesis methods, general properties, general degradation mechanisms, and recent applications will be discussed in this review. The application potential of these polyesters for a wide range of purposes, as a function of production cost, will also be assessed. It is important to note that polymers derived from CO〈sub〉2〈/sub〉 do not necessarily always lead to lower net overall CO〈sub〉2〈/sub〉 emissions (during production of after use, e.g. degradation in landfills). This needs to be evaluated using robust LCA’s and this information is currently not available for the materials discussed in this review.〈/p〉 〈/div〉 〈/div〉 〈div xml:lang="en"〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0014305719309164-ga1.jpg" width="260" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Solar Energy, Volume 190〈/p〉 〈p〉Author(s): Yanli Song, Mingyin Zou, Xin Chen, Junyu Deng, Tao Du〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉A model that could ensure the lowest energy consumption and optimize all possible performance parameters simultaneously was proposed based on experiments that run the ground source heat pump passive heat supply tower at given conditions. By studying the relationship between the range, approach, tower characteristic ratio, effectiveness, air condensation rate of the passive heat supply tower and water-air ratio, a multi-objective optimization model and its objective function are proposed. With the target of reducing power consumption to the greatest extent, the unconstrained optimization of all objective functions was performed using the Elite Non-dominated Sorting Genetic Algorithm (NSGA-II), in which five performance parameters were adopted to estimate the air flow via decision making at a given water flow rate. The results show that the heat transfer is independent of the water flow. An optimal water-air ratio of 0.48 is determined according to comprehensive analysis of the parameter weights. Under constant water flow rate, the optimal air flow rate and water flow rate is 108.5 g/s and 47.2 g/s, respectively, as observed by comparing the Decision Matrix Score (DMS) value. According to the multi-objective optimization method and the NSGA-II algorithm, optimizations of the performance of supplementary tower are more effective and reasonable as the Decision Making Matrix (DMM) can reasonably allocate parameters expected by users to occupy a larger weight.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Solar Energy, Volume 190〈/p〉 〈p〉Author(s): Matteo Valentini, Claudia Malerba, Luca Serenelli, Massimo Izzi, Enrico Salza, Mario Tucci, Alberto Mittiga〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Earth abundant Cu〈sub〉2〈/sub〉ZnSnS〈sub〉4〈/sub〉 (CZTS) semiconductor can find a promising application as wide-bandgap top cell absorber in CZTS/Silicon tandem devices. The coupling between the top and the bottom cells in a monolithic device requires the development of a proper intermediate connection able to ensure: (i) high transparency in the infrared region (ii) good electric contacts and (iii) good chemical stability under thermal treatments used for the CZTS growth, in order to prevent elements interdiffusion and silicon degradation. To this purpose, some multilayered structures based on MoS〈sub〉2〈/sub〉 and different Transparent Conductive Oxides (TCOs) were tested as intermediate connection in CZTS/Silicon tandem devices. The first working monolithic tandem cell, with open circuit voltage of about 950 mV and an efficiency of 3.5%, was obtained using a MoS〈sub〉2〈/sub〉/FTO/ZnO trilayer structure as intermediate contact between the top and the bottom cells. Some limiting factors of this device were addressed and investigated in order to increase the tandem cell efficiency.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Solar Energy, Volume 190〈/p〉 〈p〉Author(s): Yujie Wu, Jérôme H. Kämpf, Jean-Louis Scartezzini〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The bidirectional transmittance distribution function (BTDF), which is used to characterize the light transmission of a complex fenestration system (CFS), commonly involves bulky volume of data that can be a challenge to data storage and transmission in lighting simulation tools and on compact platforms. This paper introduces a compression scheme that is based on planar wavelet transforms with three levels of decomposition to efficiently compress the BTDF data of CFSs and maintain fidelity in daylighting simulation. The root-mean-square error (RMSE) and transmittance error (TE) of compressed medium-resolution BTDF data using three different wavelet bases were evaluated for five different CFS samples at various compression ratio. Based on the results, the generic error from compression did not exceed 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si1.svg"〉〈mrow〉〈mn〉20〈/mn〉〈mo〉%〈/mo〉〈/mrow〉〈/math〉 with CDF9.7 basis for compression ratio up to 200. In the case of rendering an image of a scene in which a CFS was installed at the upper daylighting section of an unilateral façade, errors began to be noticeable at a compression ratio above 70. The uniformity factor 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si2.svg"〉〈mrow〉〈mi mathvariant="normal"〉g〈/mi〉〈mn〉1〈/mn〉〈/mrow〉〈/math〉 was discovered to be relatively sensitive to compression (below 15% error), while the average horizontal illuminance and daylight glare probability (below 10% error) were immune to compression ratio below 100. Compression was also evaluated for a high-resolution BTDF data of external Venetian blinds in the simulation of work-plane illuminance (WPI). With a HDR imaging technique based sky luminance map, the WPI simulation had unnoticeable errors for compressed BTDF data within a compression ratio of 100.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Solar Energy, Volume 190〈/p〉 〈p〉Author(s): Rok Stropnik, Rok Koželj, Eva Zavrl, Uroš Stritih〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Prudent and efficient utilization of renewable energy sources is needed in order to achieve clean energy transition. Since energy use in buildings represents around 40% of total energy use in European Union the reduction of energy use in this sector is most definitely needed. One of the great challenges in this sector represents retrofit of residential buildings where 〈sup〉3〈/sup〉/〈sub〉4〈/sub〉 of buildings in Europe are residential. To reduce energy consumption and increase the use of renewables in existing residential buildings to achieve nearly zero energy buildings (nZEB) a holistic approach of retrofit with interconnected technological system is needed. In the first part of this paper the nZEB and thermal energy storage are introduced for further implementation of the phase change material (PCM) into storage tank. Furthermore energy toolkit based on the synergetic interaction between technologies integrated in the system for holistic retrofit of residential buildings, which is under development within HEART project (HORIZON 2020), is presented. In this project step towards self-sufficient heating and cooling of building is made with increase in on-site consumption of self-produced energy from solar energy and interconnection between PV, electrical storage, heat pump, thermal energy storage, fan coil heat pump, cloud based decision support and building energy management system. With such a smart energy system the almost zero-energy buildings will be possible to decrease energy use in residential sector. Improvement of sensible thermal energy storage with implemented cylindrical modules filled with PCM is investigated experimentally. The results from experiment show that thermal energy storage unit with integrated modules filled with PCM can supply desired level of water temperature for longer period of time. The advantage of PCM in thermal energy storage is in applications that needs narrow temperature range of supplying and storing thermal energy what is the subject matter of consideration in the case of HEART project.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Solar Energy, Volume 189〈/p〉 〈p〉Author(s): 〈/p〉

Description: 〈p〉Publication date: October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 European Polymer Journal, Volume 119〈/p〉 〈p〉Author(s): Kunshan Ding, Yajie Zhang, Zhihao Huang, Baolei Liu, Qiunan Shi, Lihua Hu, Nianchen Zhou, Zhengbiao Zhang, Xiulin Zhu〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Digital polymers with precise arrangements of units acting as the 0- or 1-bit, have shown bright promise for the data storage media. The easiness of encoding and decoding these polymers is essential when putting them into practical applications. Herein, the concept of utilizing sequence building block and sequencing indicator to generate easily encodable and decodable digital polymers is proposed. With the thiol-maleimide Michael coupling for digital chain growth, the dithiosuccinimide (DTS) motifs generated from the succinimide thioether linkages are used as the sequence building block. The DTS can be equipped with different groups, thus greatly enabling the modular encoding process. Importantly, the tandem mass spectrometry (MS/MS) results unveil the relatively abundant DTS-induced MS signal, which facilitates the decoding process with DTS acting as the sequencing indicator. The synergetic MS/MS induced cleavages of the two C〈img src="https://sdfestaticassets-eu-west-1.sciencedirectassets.com/shared-assets/16/entities/sbnd"〉S bonds on DTS are responsible for the relatively abundant MS signal. Finally, the work exemplifies the quantitatively decoding of a digital polymer with DTS as the sequence building block and sequencing indicator. This study demonstrates the concept of sequence building block and sequencing indicator, which advances the digital polymers for practical applications.〈/p〉〈/div〉 〈/div〉 〈div xml:lang="en"〉 〈h5〉Graphical abstract〈/h5〉 〈div〉 〈p〉The easily encodable and decodable digital polymer using dithiosuccinimide as sequence building block and sequencing indicator was proposed.〈/p〉 〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0014305719310225-ga1.jpg" width="253" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉 〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Solar Energy, Volume 190〈/p〉 〈p〉Author(s): Magd N. DinAli, Ibrahim Dincer〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉A novel renewable energy based integrated system for dimethyl-ether (DME) production and electricity generation is proposed, analyzed thermodynamically and evaluated energetically and exergetically. The DME is produced in a unique way through carbon hydrogenation process to produce pure methanol, and then DME is synthesized from methanol through methanol dehydration process. The hydrogen required for the process is produced using solid oxide steam electrolyzer (SOSE) which is powered by the thermal energy provided by solar heliostat field to generate steam and generate electricity through a steam turbine. The carbon dioxide is captured from steel furnace exhaust gas using chemical absorption method. The present system is modeled and simulated using both Aspen plus process simulation software and Engineering Equation Solver (EES), and assessed according to energy and exergy performance evaluations. The overall system energy and exergy efficiencies are then found to be 28.75% and 32.54% respectively.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Solar Energy, Volume 188〈/p〉 〈p〉Author(s): Y. Chaibi, A. Allouhi, M. Malvoni, M. Salhi, R. Saadani〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Various works investigated different photovoltaic (PV) cell equivalent-circuit models and several techniques were proposed to extract their unknown parameters. The present paper analyzes the current/voltage (I-V) characteristics for Si-crystalline PV modules under non-standard conditions of irradiance and temperature, by using single-diode and double-diode models. The Chaibi and Ishaque methods are employed to determine the parameters for each equivalent-circuit model. Then, the I-V curves provided by the manufacturers and the calculated I-V characteristics are compared at different levels of irradiance and temperature. The comparison suggests prioritizing one of the two equivalent-circuit models according to the prevailing meteorological inputs. As such, a hybrid approach is proposed in order to select the most appropriate model depending on the relevant climatic conditions. The presented approach accuracy is evaluated using real weather data of two PV plants located in two different climatic zones (Mediterranean and Semi-Continental). Results show that the double-diode model is more reliable for low-irradiance levels; however, the single-diode model performs well with low-temperature fluctuations. An error reduction of 53.93% and 21.04% can be reached for the cloudy weather and for the sunny days, respectively. Accordingly, this approach can be easily implemented as a computing tool to achieve more accurate prediction in the PV systems simulations.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Solar Energy, Volume 188〈/p〉 〈p〉Author(s): K. Murugaperumal, P. Ajay D Vimal Raj〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉This paper validates the optimal design and techno-economic feasibility of hybrid renewable energy system (HRES) for rural area electrifying applications. Plan to a design of improved performance electrification system through village owned renewable resources, such as solar irradiations, wind speed and bio mass etc. The selected HRE system has to meet out electrical needs in optimum performance manner. Hear conducted a case study on remote village Korkadu is located in Union Territory of Pondicherry, India. The expected village demand of 179.32 Kwh/day and peak of 19.56 Kw was met with proposed HRE structure, which is consists of solar PV array, wind turbine, Bio mass power generator and Battery backup system in effectively. Load growth of the village was predicted through artificial neural network (ANN-BP) feed-back propagation and Levenberg-Marguardt (LM) data training optimum technique. Encounter the optimum performance of different HRE configuration was evaluated over by HOMER software. System’s economic dispatch was analysed through various dispatch strategy and come across the proposing companied dispatch strategy has more economical and performance benefits as total NPC of system as INR 1.21 million, one unit energy generation cost as INR 13.71 and annual battery throughput as 36.648 KWh/yr. This study also expresses the comparison analysis between proposed HRES structure performance with basic utility grid extension. The consequence of the proposed work shows the HRES in remote location can be a cost effective solution for sustainable development of rural regions.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 January 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials, Volume 493〈/p〉 〈p〉Author(s): Yanan Zhang, Lu Li, Shunqun Liu, Diangang Pan, Lei Chen, Hong Chang〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The nonmagnetic In〈sup〉3+〈/sup〉 doping in the hexagonal SrFe〈sub〉12−〈/sub〉〈em〉〈sub〉x〈/sub〉〈/em〉In〈em〉〈sub〉x〈/sub〉〈/em〉O〈sub〉19〈/sub〉 (〈em〉x〈/em〉 = 0, 0.1, 0.2, 0.3, 0.4, 0.5, 1 and 2) permanent magnet increases the saturation magnetization at 300 K with the highest value up to 73.87 emu/g at 〈em〉x〈/em〉 = 0.5, and decreases it with 〈em〉x〈/em〉 〉 0.5. The coercive field keeps almost the same for 〈em〉x〈/em〉 ≤ 0.2, but it decreases with 〈em〉x〈/em〉 〉 0.2. The Curie temperature linearly decreases from 740 K for 〈em〉x〈/em〉 = 0 to 610 K for 〈em〉x〈/em〉 = 1.0, and decreases at a much lower rate to 592 K for 〈em〉x〈/em〉 = 2.0. The XPS, FT-IR and UV–vis spectra are carried out to characterize the relations between the magnetic properties and the structure. The In〈sup〉3+〈/sup〉 ions preferentially occupy the tetragonal 4f1 site, deduced from the xrd refinement and the FT-IR spectra. It is consistent with the increasing magnetization by the In〈sup〉3+〈/sup〉 doping. Oxygen vacancies exist in the compounds. The In〈sup〉3+〈/sup〉 doping and oxygen vacancies deteriorate the coercivity, while Fe〈sup〉2+〈/sup〉 ions are in favor of a high magnetocrystalline anisotropy. The energy band gap of SrFe〈sub〉12−〈/sub〉〈em〉〈sub〉x〈/sub〉〈/em〉In〈em〉〈sub〉x〈/sub〉〈/em〉O〈sub〉19〈/sub〉 increases with the increasing In〈sup〉3+〈/sup〉 doping from 1.75 eV for 〈em〉x〈/em〉 = 0 to 1.87 eV for 〈em〉x〈/em〉 = 1.0, but that of 〈em〉x〈/em〉 = 2.0 decreases to 1.79 eV. It reflects that oxygen vacancies in 〈em〉x〈/em〉 = 2.0 play a function on the energy band gap.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Solar Energy, Volume 190〈/p〉 〈p〉Author(s): Mustapha Errouha, Aziz Derouich, Babak Nahid-Mobarakeh, Saad Motahhir, Abdelaziz El Ghzizal〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉This paper presents a simple standalone photovoltaic (PV) water pumping system (PVWPS) based on an induction motor (IM) without the use of chemical energy storage. The aim of this paper is improving the control performance of pumping system. The proposed method is based on an indirect field-oriented control (IFOC) which consists of operating the motor at optimum flux by minimizing the induction motor losses. Perturb ad observe (P&O) algorithm is used to extract the maximum possible power from the PV panel. The performance of the proposed approach is proved by real time implementation using a dSpace DS1005 system and compared with conventional IFOC without losses minimization. Results show that using the proposed method, the losses are reduced and the efficiency is increased by 12%, 2.5% and 5% under 375 W/m〈sup〉2〈/sup〉, 750 W/m〈sup〉2〈/sup〉 and daily profile respectively.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Solar Energy, Volume 190〈/p〉 〈p〉Author(s): Miroslav Kocifaj, Jaromír Petržala〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉 〈p〉Light diffusing modules with improved optical properties could usefully facilitate the quest to achieve smart daylight harvesting in office buildings without detrimentally affecting visual comfort in building interiors. However, direct sunlight and sky light may cause discomfort glare. And a use of optically dense diffusers to reduce this effect and produce more uniform indoor light fields is not an efficient solution because of a concomitant loss of luminous energy. Hence, the need for more environment and people sensitive solutions is pressing in order to improve combined optical efficiency, efficacy and ergonomy of work-place luminance.〈/p〉 〈p〉That design aspiration is addressed and involves semitransparent apertures with the directional distribution of luminous intensity approaching that required. Methods for targeted shaping of an illuminance pattern are certainly advantageous for visual comfort, while supporting more demanding visual work and more flexible visual orientation. The numerical experiments we have conducted have proved that retrieval of optimum optical properties of a diffusing medium is possible through minimizing the differences between theoretical and required illuminance patterns. The inverse transform has been successfully validated for sensitivity, specificity and convergence. Our solution is augmented by the proposal for a possible realization of the diffusing aperture in the form of a particle-doped transparent medium which mimics, thus can personalize, the illuminance patterns desired.〈/p〉 〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Solar Energy, Volume 190〈/p〉 〈p〉Author(s): Jitendra Bahadur, Amir H. Ghahremani, Sunil Gupta, Thad Druffel, Mahendra K. Sunkara, Kaushik Pal〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Rapid growth within performance and stability of organic-inorganic halide-based perovskite solar cells (PSCs) has made this emerging photovoltaics a great potential for further research towards successful commercialization. However, two major issues of: (i) 〈em〉Structural ambient stability〈/em〉, and (ii) 〈em〉Toxicity〈/em〉, caused by the presence of Pb content, are the pivotal obstacles for the commercialization of environmental friendly PSC. In this regard, we are introducing a highly ambient stable PSC through the incorporation of barium (Ba) with successful ultrashort annealing through intense pulsed light (IPL). The ambient stability of Ba doped perovskite thin films was explored in the humidity range of 35–68%. The power conversion efficiency (PCE) of fabricated devices were found to be 8.99, 7.39, 6.94, 6.60, 5.98 and 3.82% for pristine, 1, 2, 5, 10, and 20 mol% Ba doping, respectively. Afterwards, fabricated devices were kept in ambient environment under dark for 20 days. With systematic photovoltaic analysis, it was observed that the 2.0 mol% Ba doped PSC exhibited 8.0% efficiency drop (from 6.94 to 6.38%), whereas the PCE of pristine based devices decreased from 8.99 to 2.60%, demonstrating an almost 71.0% drop. Our photovoltaic results demonstrated a great improvement within the ambient stability of PSC without any encapsulation which can indicate Ba doping as highly promising approach for the fabrication of PSC with higher ambient stability.〈/p〉〈/div〉 〈/div〉 〈div xml:lang="en"〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0038092X19308138-ga1.jpg" width="476" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Solar Energy, Volume 190〈/p〉 〈p〉Author(s): A. Vega, V. Valiño, E. Conde, A. Ramos, P. Reina〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The good performance of solar photovoltaic energy facilities implies the previous evaluation of the electrical behaviour of the solar modules used. Among other ways, this evaluation can be done by means of the static voltage-current characteristic (I-V curve), but also through a real-time electrical parameters monitoring. This paper proposes the design of an I-V curve tracer with electronic load. The main advantages of the prototype are its reduced cost, scalability, wireless control and sampling rate. A PIC18F46K80 microprocessor was used for the design and construction of the prototype. The development of an Android app allows the control of the prototype and the data acquisition from any mobile or tablet device. Additionally, the tracer can be configured for a continuous monitoring of the electrical parameters, temperature and irradiance.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Solar Energy, Volume 190〈/p〉 〈p〉Author(s): Mi Zhong, Wei Zeng, Hua Tang, Long-Xiang Wang, Fu-Sheng Liu, Bin Tang, Qi-Jun Liu〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Using first- principles calculations, we investigate the electronic properties of the inorganic-organic hybrid perovskite CH〈sub〉3〈/sub〉NH〈sub〉3〈/sub〉PbI〈sub〉3〈/sub〉, covering band structures, effective masses and exciton binding energies. For the first time, this study offers a comparison between perovskite polymorphs of CH〈sub〉3〈/sub〉NH〈sub〉3〈/sub〉PbI〈sub〉3〈/sub〉 with GGA and HSE06 functionals. It is verified that the standard DFT-GGA is a reliable methodology for calculating the band gaps of Pb-based perovskites. Effective masses of cubic CH〈sub〉3〈/sub〉NH〈sub〉3〈/sub〉PbI〈sub〉3〈/sub〉 are rather lighter than that of the orthorhombic and tetragonal polymorphs. And this characteristic echoes the lightest effective masses in the cubic CH〈sub〉3〈/sub〉NH〈sub〉3〈/sub〉PbI〈sub〉3〈/sub〉. The reduced mass (0.05 〈em〉m〈/em〉〈sub〉0〈/sub〉) and binding energy (15.9 meV) are obtained for the cubic phase, providing direct evidence for the high efficiency of cubic polymorphs in solar energy applications. Besides, it is found that the phase transformation from orthorhombic to tetragonal phase leads to the reduction of the band gap.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 January 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials, Volume 493〈/p〉 〈p〉Author(s): D.A. Petrov, R.D. Ivantsov, S.M. Zharkov, D.A. Velikanov, M.S. Molokeev, C.-R. Lin, C.-T. Tso, H.-S. Hsu, Y.-T. Tseng, E.-S. Lin, I.S. Edelman〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Effect of Ag inclusions on magnetic properties and magnetic circular dichroism (MCD) of Fe〈sub〉3〈/sub〉O〈sub〉4〈/sub〉 nanoparticles (NPs) in the mixed system of Fe〈sub〉3〈/sub〉O〈sub〉4〈/sub〉 and Ag NPs in dependence on the relative concentration of the components is presented. The samples were synthesized by the thermal decomposition of the mixture of constant concentration of Fe(NO〈sub〉3〈/sub〉)〈sub〉3〈/sub〉·9H〈sub〉2〈/sub〉O and varied concentration of AgNO〈sub〉3〈/sub〉. The synthesized powdered samples consisted of Fe〈sub〉3〈/sub〉O〈sub〉4〈/sub〉 and Ag NPs located very close with each other, and in the most cases the Fe〈sub〉3〈/sub〉O〈sub〉4〈/sub〉 NPs were bordered with the Ag nanocrystals. The Ag introducing in the samples does not effect, practically, in the Fe〈sub〉3〈/sub〉O〈sub〉4〈/sub〉 NPs morphology and size distribution. At the same time, Ag NPs in the powdered samples cause a decrease in the Fe〈sub〉3〈/sub〉O〈sub〉4〈/sub〉 NPs magnetization and shift of the blocking temperature to lower temperatures, both approximately proportional to the Ag concentration. Most significant changes are revealed in the MCD spectra in the energy region of 1.2–2.2 eV. We have discussed the influence of the Ag NPs on the MCD spectra features in terms of the charge-transfer electron transitions.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 21 August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials〈/p〉 〈p〉Author(s): Sanae Zriouel〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Based on our works [1], [2], [3], [4], we report the magnetic and hysteretic properties of graphene-based Janus materials namely, pure and doped zigzag graphone nanoribbons, hexagonal core/shell graphene-like nanoribbon, and graphyne core/shell nanoparticle, within the framework of both Monte Carlo calculations and mean field theory. We have reported the effects of the Hamiltonian parameters on the magnetic and the thermodynamic quantities of the systems. The total magnetization, the susceptibility, the specific heat, and the hysteresis curves, as well as the critical temperature and the compensation behavior, that is of crucial importance for technological applications such as thermo-optical recording, are studied. A number of characteristic behaviors are found, such as the existence of two new and non-classified magnetization profiles in addition to the 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si80.svg"〉〈mrow〉〈mi〉Q〈/mi〉〈mo〉-〈/mo〉〈mo〉,〈/mo〉〈mi〉P〈/mi〉〈mo〉-〈/mo〉〈/mrow〉〈/math〉, and 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si81.svg"〉〈mrow〉〈mi〉N〈/mi〉〈mo〉-〈/mo〉〈/mrow〉〈/math〉types of compensation behavior and the occurrence of square, single, and triple hysteresis loops which exhibit different step effects and various shapes.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 22 August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials〈/p〉 〈p〉Author(s): M. Zarifi, P. Kameli, T. Raoufi, A. Ghotbi Varzaneh, D. Salazar, M.I. Nouraddini, L. Kotsedi, M. Maaza〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The magnetocaloric properties in La〈sub〉0.5〈/sub〉Ca〈sub〉0.5-x〈/sub〉Pb〈sub〉x〈/sub〉MnO〈sub〉3〈/sub〉 (0≤x≤0.2) manganites are considered by both direct and indirect measurement techniques. The ac susceptibility shows that the compounds with low Pb doping exhibit mixture of CE-type AFM ordering and FM phase, while at high Pb doping FM phase is dominated. For samples x=0 and 0.05, the M-H curves at different temperatures exhibit the magnetization first increases and then decreases with decreasing temperature, indicating the growth of the AFM phase below T〈sub〉N〈/sub〉. In the curves for samples x=0.1 and 0.2, with decreasing temperature the magnetization increases and the FM phase is overcoming at low temperature. The magnetic entropy change (ΔS〈sub〉M〈/sub〉) is enhanced continuously with increasing Pb concentration up to x=0.1, then slightly decreases. The magnetocaloric effect in the vicinity of T〈sub〉C〈/sub〉 for x= 0.1 and 0.2 was investigated by the direct field-induced adiabatic temperature change (ΔT〈sub〉ad〈/sub〉). The results of the direct method show the absolute values of obtained ΔT〈sub〉ad〈/sub〉 are almost the same for both samples (0.62 and 0.53 K under 1.96 T for x=0.1 and 0.2, respectively). The outcomes demonstrate that doping by Pb is a promising material for the magnetic refrigeration.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 January 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials, Volume 493〈/p〉 〈p〉Author(s): Shabir Ahmad Mir, Dinesh C. Gupta〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Ba〈sub〉2〈/sub〉MUO〈sub〉6〈/sub〉 (M = Co, Ni) alloys are investigated to understand their electronic structure, magnetic character together with thermoelectric behavior using 〈em〉ab-initio〈/em〉 formulism. The variations in physical properties by changing M-site atom are analyzed. The crystal structure of Ba〈sub〉2〈/sub〉MUO〈sub〉6〈/sub〉 (M = Co, Ni) alloys is found to be face-centered cubic (〈em〉Fm-3m〈/em〉) with lattice constant of 0.845 nm for Ba〈sub〉2〈/sub〉CoUO〈sub〉6〈/sub〉 and 0.841 nm for Ba〈sub〉2〈/sub〉NiUO〈sub〉6〈/sub〉. The band structure and density of states convey half-metallic ferromagnetic character of Ba〈sub〉2〈/sub〉CoUO〈sub〉6〈/sub〉, while Ba〈sub〉2〈/sub〉NiUO〈sub〉6〈/sub〉 exhibit ferromagnetic semiconducting nature. The electron filling in the 〈em〉d〈/em〉-orbitals of Co and Ni determines the overall electronic and magnetic character of alloys. The obtained structural parameters and magnetic moment are consistent with experimental results. The variation in various thermoelectric parameters with temperature is also examined. The highest value of power factor obtained for Ba〈sub〉2〈/sub〉NiUO〈sub〉6〈/sub〉 and Ba〈sub〉2〈/sub〉CoUO〈sub〉6〈/sub〉 is 54.92 μW cm〈sup〉−1〈/sup〉 K〈sup〉−2〈/sup〉 and 9.25 μW cm〈sup〉−1〈/sup〉 K〈sup〉−2〈/sup〉, respectively. The semiconducting nature in both spin orientations favors Ba〈sub〉2〈/sub〉NiUO〈sub〉6〈/sub〉 for thermoelectric applications. The computed elastic constants along with other elastic parameters suggest that these alloys are mechanically stable and possess ductile character.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Solar Energy, Volume 190〈/p〉 〈p〉Author(s): Mohamed Dardir, Mohamed El Mankibi, Fariborz Haghighat, Lubomir Klimes〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Earlier applications of phase change material (PCM)-to-air heat exchangers (PAHXs) reported the insufficient cooling charging energy needed for complete solidification of the PCM in free cooling systems. Also, the prediction of PAHX performance under low airflow regimes is a system limitation for free cooling applications. Besides, the implementation of the long wave thermal radiation cooling concept has not gained much attention in the free cooling design of PAHX units. This paper reports the development of PAHX system for building envelope applications that promotes the thermal radiation loss to the sky during night-time to maximize the cooling potential. A 2D numerical model has been developed considering the PCM thermal behavior, short and long wave radiation, and convection phenomena. New thermal boundaries of long-wave radiation have been proposed between system elements and the sky temperature. In addition, the model considered various forms of convective heat transfer phenomena. The apparent heat capacity method was used to simulate the thermal storage process. Experimentally obtained data and inter-model comparison were used to validate the proposed model. Two full-scale prototypes of the developed PAHX system were designed and tested under real conditions using two different types of PCMs. A parametric analysis was conducted to investigate the system thermal behavior under various air velocity profiles in the air channel and various inlet air temperature conditions. The results indicate that the building envelope integrated PAHX can use the sky radiation as a cooling source.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Solar Energy, Volume 190〈/p〉 〈p〉Author(s): P.D. Sreedevi, R. Vidya, P. Ravindran〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Direct band gap semiconductors with high optical absorption, high electrical conductivity, high carrier mobility, low reflectance and low recombination rate of charge carriers are needed for a variety of applications in solar energy conversion and optoelectronics. We have identified three ternary semiconductors Ca〈sub〉3〈/sub〉PN, NaBaP and ZrOS which have direct-band gap and other promising properties for solar energy applications. The prime novelty of this work mainly projects a detailed information on the electronic structure and optical properties for the three materials. From the first principles computational work and analysis, we have found that all the three materials with optimum band gap (~1.52 eV) value are having suitable absorption coefficient, extinction coefficient, optical conductivity and low reflectance in the visible region. Moreover, these materials are found to have low charge carrier effective masses and low recombination rates which can enhance carrier mobility and electrical conductivity. As a result, we will have three best non-silicon based direct band gap materials consisting of earth-abundant and non-toxic elements in the photovoltaic (PV) industry.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Solar Energy, Volume 190〈/p〉 〈p〉Author(s): Yanqing Wang, Xingze Chen, Junjie Shao, Shihao Pang, Xinlai Xing, Ziyu Dong, Shuang Liu, Zhendong Cui, Xinlian Deng, Chengwu Shi〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The synthesis and characterization of a series of hole transporting materials (HTMs) based on carbazole core and dimethoxytriphenylamine (TPA) groups are reported. By modifying the number of TPA components in the HTMs, the influence of the structure of HTMs molecules on the photovoltaic performance of CH〈sub〉3〈/sub〉NH〈sub〉3〈/sub〉PbI〈sub〉3〈/sub〉 perovskite solar cells are investigated. 〈strong〉TPA〈sub〉2〈/sub〉C〈/strong〉, in which two TPA units are incorporated onto the carbazole core, exhibited higher photovoltaic performance than 〈strong〉TPA〈sub〉1〈/sub〉C〈/strong〉, 〈strong〉TPA〈sub〉3〈/sub〉C〈/strong〉 and 〈strong〉TPA〈sub〉4〈/sub〉C〈/strong〉, which contain one, three and four TPAs, respectively. The introduction of TPA group from one to two can improve the device result, however, additional branches introduced to the carbazole core did not led to higher efficiency.〈/p〉〈/div〉 〈/div〉 〈div xml:lang="en"〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0038092X19308151-ga1.jpg" width="500" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 European Polymer Journal, Volume 119〈/p〉 〈p〉Author(s): Fatemeh Zarei, Azam Marjani, Roozbeh Soltani〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉To capture heavy metals in aqueous solution, it is imperative to develop viable and safe heavy metals uptake techniques. Herein, we report polymer matrix nanocomposite adsorbents with 2 and 5 wt.% nanofiller contents based on functionalised mesoporous fibrous silica KCC-1, chitosan, and oleic acid (abbreviated as TA-KCC-1/Chi-OLA NC). TA-KCC-1/Chi-OLA NCs relying on physicochemical adsorption are potential candidates for heavy metals removal because of their facile fabrication procedure, low toxicity, biodegradability, and high affinity toward heavy metals. The adsorption of Pb(II) cations onto green TA-KCC-1/Chi-OLA 5 wt.% adsorbent was studied in the batch system. Langmuir and pseudo-second-order models were found to be the best fit models to predict isotherms and kinetics of adsorption, respectively. The maximum adsorption capacity according to the Langmuir model was 168 mg g〈sup〉−1〈/sup〉 (adsorption conditions: pH: 9.0, adsorbent dose: 20.0 mg; contact time: 100 min; initial concentration: 100 mg L〈sup〉−1〈/sup〉).〈/p〉〈/div〉 〈/div〉 〈div xml:lang="en"〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0014305719312339-ga1.jpg" width="399" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 European Polymer Journal, Volume 119〈/p〉 〈p〉Author(s): Benjámin Gyarmati, Béla Pukánszky〈/p〉

Description: 〈p〉Publication date: September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 European Polymer Journal, Volume 118〈/p〉 〈p〉Author(s): 〈/p〉

Description: 〈p〉Publication date: 15 September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Solar Energy, Volume 190〈/p〉 〈p〉Author(s): Sabrina N. Rabelo, Tiago F. Paulino, Willian M. Duarte, Antônio A.T. Maia, Luiz Machado〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In a Direct Expansion Solar Assisted Heat Pump (DX-SAHP), a valuable part of the energy is provided from solar radiation. The solar radiation can fluctuate during the day affecting the performance of the system. The impact of a fixed opening in the expansion device on the system performance is not well known, especially for a small-size solar assisted heat pump. In this context, it is presented an experimental analysis of the influence of the expansion valve opening on the performance of a CO〈sub〉2〈/sub〉 DX-SAHP. Experimental tests were carried out considering different solar radiations conditions. The value of the expansion device opening that leads to the maximum COP was almost the same, regardless of solar radiation. In consequence, it was concluded that, for a small CO〈sub〉2〈/sub〉 DX-SAHP, using a basic cycle configuration a static expansion device as a capillary tube would be suitable, reducing the costs of this equipment.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 January 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials, Volume 493〈/p〉 〈p〉Author(s): Haitao Zhou, Desheng Pan, Yong Li, Da Li, C.J. Choi, Zhidong Zhang〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In this work, we report the magnetic properties of metal–organic frameworks (MOF) of perovskite-like [(CH〈sub〉3〈/sub〉)〈sub〉2〈/sub〉NH〈sub〉2〈/sub〉]M(HCOO)〈sub〉3〈/sub〉 (M = Fe〈sup〉II〈/sup〉, Co〈sup〉II〈/sup〉) and niccolite-like [(CH〈sub〉3〈/sub〉)〈sub〉2〈/sub〉NH〈sub〉2〈/sub〉]Fe〈sup〉III〈/sup〉Fe〈sup〉II〈/sup〉(HCOO)〈sub〉6〈/sub〉 synthesized by a solvothermal route. The [(CH〈sub〉3〈/sub〉)〈sub〉2〈/sub〉NH〈sub〉2〈/sub〉]Fe〈sup〉II〈/sup〉(HCOO)〈sub〉3〈/sub〉 exhibits two magnetic transitions at the temperatures of ~19 K for the canted weak ferromagnetic ordering and of ~10 K for the blocking of single-ion quantum magnet due to phase separation, while the [(CH〈sub〉3〈/sub〉)〈sub〉2〈/sub〉NH〈sub〉2〈/sub〉]Co〈sup〉II〈/sup〉(HCOO)〈sub〉3〈/sub〉 shows one magnetic transition at the Curie temperature (T〈sub〉C〈/sub〉) of 14.9 K for the canted weak ferromagnetic ordering. Below the T〈sub〉C〈/sub〉 values, spin-flop transition is observed in the magnetization curves of the [(CH〈sub〉3〈/sub〉)〈sub〉2〈/sub〉NH〈sub〉2〈/sub〉]M(HCOO)〈sub〉3〈/sub〉 crystals with the critical magnetic field of about 104 kOe and 90 kOe at 10 K, respectively. Multistep-like jumping magnetization transitions induced by high magnetic field are observed in the [(CH〈sub〉3〈/sub〉)〈sub〉2〈/sub〉NH〈sub〉2〈/sub〉]Fe〈sup〉III〈/sup〉Fe〈sup〉II〈/sup〉(HCOO)〈sub〉6〈/sub〉 in a temperature range between 10 and 25 K, indicating a complex spin configuration different from that in the [(CH〈sub〉3〈/sub〉)〈sub〉2〈/sub〉NH〈sub〉2〈/sub〉]M(HCOO)〈sub〉3〈/sub〉 MOFs.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 January 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials, Volume 493〈/p〉 〈p〉Author(s): B. Gokul, P. Saravanan, P. Matheswaran, M. Pandian, R. Sathyamoorthy, K. Asokan, V.T.P. Vinod, Miroslav Černík〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉We herein investigate the novel magnetic interactions, such as exchange bias (EB), memory effect (ME) and magnetic relaxation dynamics (MRD) in NiO and 10 wt% Gd doped NiO nanoparticles synthesized by hydrothermal process. X-ray diffraction studies showed crystallization of face-centered-cubic structure for both NiO and Gd-doped NiO nanoparticles. Transmission electron microscopy analysis revealed a spherical morphology for both samples and their mean particle sizes were estimated as 24.5 and 10.3 nm for the pure and Gd-doped NiO nanoparticles, respectively. SQUID magnetic measurements demonstrated the occurrence of large EB coupling: 1.04 and 0.767 kOe; and enhanced coercive fields: 1.75 and 1.27 kOe, for the pure and Gd-doped NiO nanoparticles, respectively. The size-dependent magnetic properties such as, EB, ME and MRD is found to vanish at the average blocking temperature and interestingly, these properties set-in on cooling the samples at 5 K under applied field of 5 kOe. The surface defects such as oxygen vacancies and the Gd〈sub〉2〈/sub〉O〈sub〉3〈/sub〉 impurity phase played a significant role in determining the EB and ME characteristics of NiO nanoparticles.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 January 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials, Volume 493〈/p〉 〈p〉Author(s): S. Sadeghi, S.M. Hamidi〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉We numerically examine the role of Fano resonance for enhanced magneto-optical effect in an arrayed magneto-plasmonic core-shell structure composed of Bi:YIG cores as a magneto-optical active medium and Au sells as plasmonic ones. The optical and magneto-optical behavior of the magneto-plasmonic core-shell grating structure sustaining Fano resonance is investigated by means of Lumerical software based on the finite-difference time-domain solver. In the proposed structure, Fano resonance arises from the interplay between the guided mode and the surface plasmon resonance which results in enhanced magneto-optical Faraday effect. In addition, the Fano resonance and correspond enhanced magneto-optical effect can be tuned by changing the array period of the structure. The obtained results can be of interest in miniaturized and advanced magneto-optical devices.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 January 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials, Volume 493〈/p〉 〈p〉Author(s): Muhammad Waqas〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Heat transfer in ferromagnetic stretching flow by moving surface considering a magnetic dipole is elaborated in current research. Rheological relations of non-Newtonian (Williamson) fluid are taken into account for modeling and analysis. Chemical reactions (homogeneous and heterogeneous) are considered for elaboration of mass transportation characteristics. Governing flow expressions are reduced to ODEs by implementing transformation procedure. The well-known bvp4c scheme is used for nonlinear systems computation. Influences of sundry parameters like ferrohydrodynamic interaction parameter, Weissenberg number, homogeneous-heterogeneous reaction parameters, Prandtl number and heat generation parameter on velocity, thermal and solutal fields in addition to coefficient of skin-friction and Nusselt number are displayed via graphs and tabular values. It is revealed that velocity and thermal fields have opposite behavior for ferrohydrodynamic interaction parameter. Besides the heat transportation rate is improved subjected to larger Prandtl number.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 December 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials, Volume 492〈/p〉 〈p〉Author(s): Viktor Ivashko, Oleg Angelsky, Petro Maksimyak〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Ferromagnetism of nano-graphene layer within Ising model was studied. All results were obtained by using Monte Carlo simulation based on Metropolis algorithm. By applying external magnetic field at room temperature, a gradual transition between ferromagnetic and paramagnetic phases was obtained. This indicates to a potentiality of such a monolayer to be used as a magnetic field sensor. The existence of hysteresis, was established, which strongly depends on the type and magnitude of the interaction strength between the nearest neighbor lattice nodes (spins). Gradual two-step transition between ferromagnetic and paramagnetic phases near absolute zero temperature, was obtained. The results of numerical simulations are in agreement with the available experimental works of other authors.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 January 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials, Volume 493〈/p〉 〈p〉Author(s): L.S. Paixão, G. Rangel, E.O. Usuda, W. Imamura, J.C.G. Tedesco, J.C. Patiño, A.M. Gomes, C.S. Alves, A.M.G. Carvalho〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Since the discovery of the giant magnetocaloric effect in the compound Gd〈sub〉5〈/sub〉Si〈sub〉2〈/sub〉Ge〈sub〉2〈/sub〉, rare earth based intermetallics of the form R〈sub〉5〈/sub〉(Si,Ge)〈sub〉4〈/sub〉 have been largely investigated in their structural and magnetic properties. From the parent compounds Gd〈sub〉5〈/sub〉Si〈sub〉4〈/sub〉 and Nd〈sub〉5〈/sub〉Si〈sub〉4〈/sub〉, the present paper reports the magnetic and magnetocaloric properties of the series 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si23.svg"〉〈mrow〉〈msub〉〈mrow〉〈mi mathvariant="normal"〉Gd〈/mi〉〈/mrow〉〈mrow〉〈mn〉5〈/mn〉〈mo〉-〈/mo〉〈mi〉x〈/mi〉〈/mrow〉〈/msub〉〈/mrow〉〈/math〉〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si24.svg"〉〈mrow〉〈msub〉〈mrow〉〈mi mathvariant="normal"〉Nd〈/mi〉〈/mrow〉〈mrow〉〈mi〉x〈/mi〉〈/mrow〉〈/msub〉〈/mrow〉〈/math〉Si〈sub〉4〈/sub〉. Our results indicate that the magnetic moments of the Gd and Nd sublattices are antiparallel, where the moment of each sublattice has almost the same magnitude near 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si25.svg"〉〈mrow〉〈mi〉x〈/mi〉〈mo linebreak="goodbreak" linebreakstyle="after"〉=〈/mo〉〈mn〉4〈/mn〉〈/mrow〉〈/math〉. The antiparallel alignment of the sublattices is detrimental to the magnetocaloric properties of the samples. The end members of the series present larger entropy changes, while for the compound 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si26.svg"〉〈mrow〉〈mi〉x〈/mi〉〈mo linebreak="goodbreak" linebreakstyle="after"〉=〈/mo〉〈mn〉4〈/mn〉〈/mrow〉〈/math〉 such quantity is much lower when compared to all other samples.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 January 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials, Volume 493〈/p〉 〈p〉Author(s): P. Lampen-Kelley, E.M. Clements, B. Casas, M.H. Phan, H. Srikanth, J. Marcin, I. Skorvanek, H.T. Yi, S.W. Cheong〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉We have recently applied the magnetic field and temperature dependence of magnetic entropy change as a probe of the magnetic states of a single crystal of Ca〈sub〉3〈/sub〉Co〈sub〉2〈/sub〉O〈sub〉6〈/sub〉 to establish a more comprehensive magnetic phase diagram for this exotic system. The results are consistent with the spin-density wave description of the ground state and indicate the suppression of the modulated state in favor of a ferrimagnetic up-up-down arrangement of the spin chains with the application of a moderate field. We demonstrate, in this study, that the features of the static magnetic phase diagram are preserved when the grain size of Ca〈sub〉3〈/sub〉Co〈sub〉2〈/sub〉O〈sub〉6〈/sub〉 is reduced to 440 nm (below the maximum 〈em〉c〈/em〉-axis correlation length of ~550 nm in Ca〈sub〉3〈/sub〉Co〈sub〉2〈/sub〉O〈sub〉6〈/sub〉), although the polycrystalline materials show a non-saturating behavior, rounded steps, and reduced magnetization when compared to the single crystal. Our new finding of the multiple low-temperature magnetization steps in the 440 nm sample, together with conflicting reports concerning such steps in nanostructured samples, suggests that correlations in the 〈em〉ab〈/em〉 plane are more important than correlations along the 〈em〉c〈/em〉-axis in the appearance of the plateaus. The relaxation processes in the system are studied through the decay of remanent magnetization, ac susceptibility, and Argand diagrams. The introduction of grain boundaries in Ca〈sub〉3〈/sub〉Co〈sub〉2〈/sub〉O〈sub〉6〈/sub〉 weakens the slow-dynamic state, widens the low-temperature distribution of relaxation times, and lowers activation energies within the Arrhenius-like relaxation regime.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 January 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials, Volume 493〈/p〉 〈p〉Author(s): Baoshan Cui, Hao Wu, Meixia Chang, Jijun Yun, Yalu Zuo, Meizhen Gao, Kang L. Wang, Li Xi〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Domain wall (DW) motion via current induced spin-orbit torque (SOT) and/or a magnetic field in ferromagnet/heavy metal heterostructure has attracted abundant interests due to its potential applications in magnetic memories and logic devices. In this work, we study the influence of the depinning energy barrier on DW motion in the creep regime using the polar magneto-optical Kerr microscopy in the Cr layer decorated Pt/Co/Ta structure. We find that although the SOT efficiency shows a significant enhancement in the Pt/Co/Cr/Ta system, but the current-induced DW motion efficiency still shows an attenuation. We confirm that this unexpected result is caused by the enhanced pinning energy barrier, extracted from the relationship between the cumulative depinning probability (〈em〉P〈/em〉〈sub〉d〈/sub〉) and the depinning time (〈em〉t〈/em〉). Moreover, the relationship between 〈em〉P〈/em〉〈sub〉d〈/sub〉 and 〈em〉t〈/em〉 exhibits preferred exponential distribution, indicating that a single energy barrier governs the depinning behavior in our systems. We also reveal that the energy barrier depends on the interface between the ferromagnet and heavy metal. Our study suggests that the current-induced DW motion efficiency is not only determined by the SOT efficiency, but also the depinning energy barrier.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 January 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials, Volume 493〈/p〉 〈p〉Author(s): Ricardo Francisco Alves, Marcio Assolin Correa, Ramon Alves Torquato, Tibério Andrade dos Passos, Felipe Bohn, Rodolfo Bezerra da Silva, Rodinei Medeiros Gomes, Danniel Ferreira de Oliveira〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Heusler alloy composed by NiMnIn was prepared by induction melting in Argon atmosphere. The thermal martensitic and magnetic transitions of the sample were identified by differential scanning calorimetry. The quasi-static magnetic properties were observed by field-colled, zero-field-colled, and isothermal magnetization curves in a wide range of temperature. Moreover, AC susceptibility measurements were employed to analyze the low-frequency magnetization dynamics. The martensitic state of the sample leads to magnetic disturbances of quasi-diamagnetism and exchange bias behavior. The exchange bias field presented a transition from negative values to positive values with the temperature increasing. Therefore, the results open a way for technological applications of the NiMnIn Heusler alloy, with potential perspectives for the development of spintronic devices.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 December 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials, Volume 492〈/p〉 〈p〉Author(s): Krzysztof Tadyszak, Katarzyna Chybczyńska, Paweł Ławniczak, Alina Zalewska, Bogumił Cieniek, Michał Gonet, Marek Murias〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Complex magnetic behavior of pristine, partially reduced graphene oxide aerogel with C/O ratio of 2.35 (EDS) with full analysis of oxygen rich groups attached to the surface is reported. Purity of the system was confirmed by three techniques: elemental analysis, EDS, EPR at 4.2 K none of them detected traces of transition metal ions, especially iron and manganese. Computer tomography reviled the inside foam structure, showing different stacking inside and at the surface, as well as some structural defects. The foams morphology was confirmed by SEM. Electric measurements show linear voltage current relationship and temperature dependences which could be described in the framework of variable range hopping model. Magnetic susceptibility measurements exhibit very weak ferromagnetic behavior modified by antiferromagnetic interactions and paramagnetism. EPR study confirms two component paramagnetism of Curie and Pauli type.〈/p〉〈/div〉 〈/div〉 〈div xml:lang="en"〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0304885318321899-ga1.jpg" width="424" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 January 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials, Volume 493〈/p〉 〈p〉Author(s): Yuichi Ishida, Kenji Kondo〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉We investigate the skyrmion Hall effect using the Landau-Lifshitz-Gilbert (LLG) equation and the Thiele equation, respectively. Then, we find that these methods give different values for the ratio of in-plane skyrmion velocity components when the Gilbert damping constant is relatively small. Since the Thiele equation is derived from the LLG equation by assuming that the skyrmion structure does not change and behaves like a rigid body, the above result suggests that this assumption does not hold when the Gilbert damping constant is relatively small. Therefore, we conclude that the Thiele equation can not describe the systems precisely under the relatively small Gilbert damping constant due to the distortion of the skyrmion structure and that it is mandatory to solve the LLG equation numerically in order to investigate the skyrmion Hall effect accurately. This result is very important since the Gilbert damping constants of metal materials are generally very small.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 January 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials, Volume 493〈/p〉 〈p〉Author(s): D. Wang, Yan Zhou〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Spin-orbit torque in magnetic domain walls was studied by solving the Pauli-Schrödinger equation for the itinerant electrons. The Rashba interaction considered is derived from the violation of inversion symmetry at interfaces between ferromagnets and heavy metals. In equilibrium, the Rashba spin-orbit interaction gives rise to a torque corresponding to the Dzyaloshinskii-Moriya interaction. When there is a current flowing, the spin-orbit torque experienced by the itinerant electrons in short domain walls has both field-like and damping-like components. However, when the domain wall width is increased, the damping-like component, which is the counterpart of the non-adiabatic spin transfer torque, decreases rapidly at the domain wall center. In contrast to the non-adiabatic spin transfer torque, the damping-like spin-orbit torque does not approach to zero far away from the domain wall center, even in the adiabatic limit. The scattering of spin-up and spin-down wave functions, which is caused by the Rashba spin-orbit interaction and the spatial variation of magnetization profile in the domain walls, gives rise to the finite damping-like spin-orbit torque.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 December 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials, Volume 492〈/p〉 〈p〉Author(s): Hayato Masumitsu, Soshi Yoshinaga, Yoshifuru Mitsui, Rie Y. Umetsu, Masahiko Hiroi, Yoshiya Uwatoko, Keiichi Koyama〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Substitution effects on weak itinerant electron ferromagnetism in Cr-based ternary alloy CrAlGe were investigated. It was found that substitution of Cr by 3〈em〉d〈/em〉 transition metal with more electrons than Cr enhanced the spontaneous magnetization and Curie temperature. In addition, the itinerancy of CrAlGe was suppressed with the increase of electrons. The ferromagnetism of CrAlGe was related to electron number rather than lattice parameters. The origin of change of itinerancy was suggested to be Coulomb force caused by effective nuclear charge.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 January 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials, Volume 493〈/p〉 〈p〉Author(s): Jun Zhou, Xiangfeng Shu, Yueqin Wang, Jialin Ma, Yin Liu, Ruiwen Shu, Lingbing Kong〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉(1−x)CoFe〈sub〉2〈/sub〉O〈sub〉4〈/sub〉/xCoFe composites with x = 0.3, 0.4, 0.5, 0.6 were synthesized by using a hydrothermal method. The face-centered cubic structure CoFe〈sub〉2〈/sub〉O〈sub〉4〈/sub〉 adheres to the polyhedral CoFe surface due to strong magnetic interaction to form a composite material. The effects of compositions of the CoFe〈sub〉2〈/sub〉O〈sub〉4〈/sub〉/CoFe composites on their microwave absorption properties were studied. The sample with a composition of 0.4CoFe〈sub〉2〈/sub〉O〈sub〉4〈/sub〉/0.6Co〈sub〉4〈/sub〉Fe〈sub〉6〈/sub〉 showed optimal reflection loss (RL) −58.22 dB at 12.96 GHz, and the matching thickness was 1.45 mm. Meanwhile, it had an effective absorption frequency range of 11.12–15.28 GHz (RL 〈 −10 dB), with a bandwidth of 4.16 GHz, covering the X-band and Ku-band. The enhanced microwave absorption properties of the composites, as compared with the two components, are attributed to the strengthened natural resonance and the increased impedance matching. Most importantly, by adjusting their composition, the CoFe〈sub〉2〈/sub〉O〈sub〉4〈/sub〉/CoFe composites can be used as microwave absorbers at C, X or Ku bands. Consequently, these CoFe〈sub〉2〈/sub〉O〈sub〉4〈/sub〉/CoFe composites are promising candidates that can be used to design effective microwave absorbers over wide frequency bands.〈/p〉〈/div〉 〈/div〉 〈div xml:lang="en"〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S030488531932013X-ga1.jpg" width="500" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 12 August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials〈/p〉 〈p〉Author(s): M.D. Hossain, M.A. Hossain, M.N.I Khan, S.S. Sikder, M.A. Hakim〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Doping of rare earth (RE) ions can influence the magnetic properties in spinel ferrites, whereas the phase formation plays an important role. Therefore, it is important to choose the RE ions for doping content to get more benefit. In this work, synthesis of Yttrium doped Co-Zn ferrites were carried out by the method of solid state reaction. Co〈sub〉0.25〈/sub〉Zn〈sub〉0.75〈/sub〉Y〈sub〉x〈/sub〉Fe〈sub〉2-x〈/sub〉O〈sub〉4〈/sub〉 (CZYF) is the general formula of the studied ferrites where x = 0.00, 0.02, 0.04, 0.06 and 0.08. The structural properties of CZYF ferrites were studied by X-ray diffraction (XRD) technique and further refined by Rietveld method. XRD and Rietveld refinement approved that all the CZYF samples are cubic spinel structure and the lattice parameters were increased with increasing Y content. The variation of grain growth and surface morphology of CZYF samples were studied from SEM images indicated that the average grain size increased from 1.412 µm to 2.341 µm. Frequency dependent magnetic properties (complex permeability, loss factor) were observed in the range of 100 Hz to 120 MHz at 300 K (room temperature). The initial permeability of CZYF ferrites are found to decrease with the increase in Y content. This decrease nature of permeability is related to the increase of porosity and average grain size. At three different temperatures (80 K, 200 K and 300 K), we measured saturation magnetization, coercivity and remanent magnetization. The mentioned properties make CZYF ferrites applicable for use as a soft ferrite.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 December 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials, Volume 492〈/p〉 〈p〉Author(s): S. Divya, K. Jeyadheepan, J. Hemalatha〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Magnetoelectric (ME) nanocomposite flexible films composed of electroactive poly(vinylidene fluoride-hexafluoropropylene) (P(VDF-HFP)) and ferromagnetic cobalt ferrite (CoFe〈sub〉2〈/sub〉O〈sub〉4〈/sub〉) are fabricated. Single-phase nano CoFe〈sub〉2〈/sub〉O〈sub〉4〈/sub〉 with cubic spinel structure, synthesized by sol-gel auto combustion technique, is reinforced in different weight percentages to fabricate P(VDF-HFP)-CoFe〈sub〉2〈/sub〉O〈sub〉4〈/sub〉 films through spin coating technique. Effect of CoFe〈sub〉2〈/sub〉O〈sub〉4〈/sub〉 on structural, morphological, magnetic, ferroelectric, magnetoelectric properties, and giant magnetoresistance (GMR) behavior has been investigated. It is observed that the reinforcement of CoFe〈sub〉2〈/sub〉O〈sub〉4〈/sub〉 in P(VDF-HFP) matrix has strongly influenced the formation of β-phase conformation and the degree of structural order. The co-existence of ferroelectric and ferromagnetic orderings in the films has been demonstrated by the P-E and M-H plots. The variations in the polarization effects in the presence of a magnetic field provide the evidence for magnetoelectric cross-coupling in P(VDF-HFP)-CoFe〈sub〉2〈/sub〉O〈sub〉4〈/sub〉. The films exhibit a GMR effect from 7% to 100%. In order to demonstrate the use of ME induced GMR in magnetic field sensing, P(VDF-HFP)-CoFe〈sub〉2〈/sub〉O〈sub〉4〈/sub〉 film (10 wt%) is used in a prototype sensor circuit. A good sensing ability and linear response obtained prove that the prepared film can be used as field sensor.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 January 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials, Volume 493〈/p〉 〈p〉Author(s): Ya-nan Zhang, Naisi Zhu, Peng Gao, Yong Zhao〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉A highly-sensitive magnetic field sensor based on magnetic fluid (MF) infiltrated ring whispering gallery mode (WGM) resonator was proposed and demonstrated in experiment. The resonator was fabricated by attaching a corrosive hollow-core fiber (HCF) to a tapering fiber, which could generate a WGM resonance spectrum. It was firstly demonstrated in theory and experiment that resonance wavelength of the WGM resonator is sensitive to refractive index of medium that infiltrated in the HCF, and the refractive index sensitivity is related to the wall thickness of the HCF. Then, coupling and packaging of the HCF and the tapering fiber were realized by using a simple method, making the sensor robust and portable. When MF was infiltrated in the HCF, since the refractive index of the MF changed with external magnetic field, the WGM resonance valley shifted in wavelength as a function of the magnetic field, which could be used for magnetic field sensing. Experimental results demonstrated that a high sensitivity of 32.4 pm/Gs could be obtained for magnetic field measurement with good linearity. Besides, the proposed sensor behaved simple and robust structure, simple preparation process, low cost, and compact size.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 January 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials, Volume 493〈/p〉 〈p〉Author(s): Mustafa Akyol, Nazan Demiryurek, Onur Iloglu, Kutluhan Utku Tumen, Faruk Karadag, Ahmet Ekicibil〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Y〈sub〉3〈/sub〉Fe〈sub〉5〈/sub〉O〈sub〉12〈/sub〉 shortly named YIG thin film and various form of Au and YIG thin film stacks have been grown on quartz substrate using both spin-coating and sputtering methods. The films are crystallized in cubic phase after heat treatments process that is optimized to avoid cracks on the surface. The thickness of the YIG layer measured by cross-section electron microscope imaging technique are found as about 80 nm for all samples. While the root-mean-square surface roughness of the YIG film is in sub-nanometer scale, it increases up to 2.86 nm by adding Au layer in the film structure. All films exhibit in-plane easy axis and low coercive field at room temperature. But, the saturation magnetization values of films decrease with Au layer. Whereas the optical transmission value is around 80% for YIG samples above 400 nm, it decreases dramatically with Au in the film stacks. The highest absorption coefficient value is found as ~20 × 10〈sup〉4〈/sup〉 cm〈sup〉−1〈/sup〉 in Q/Au/YIG structure. This strong absorption might come from the localized surface plasmon polaritons of Au noble metals in YIG structure because it enhances the electronic transition from crystal field splitting. As a result of these measurements, it is seen that the Au layer reduces the magnetization of the films, while increases the absorption rate significantly. Due to considerably low production cost of YIG in this work, it might open to commonly use of them in the magneto-optical devices.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 January 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials, Volume 493〈/p〉 〈p〉Author(s): Chuangye Yao, Muhammad Ismail, Aize Hao, Santhosh Kumar Thatikonda, Wenhua Huang, Ni Qin, Dinghua Bao〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Oxygen vacancies derived resistive and magnetic switching, was demonstrated in facile solution-processed Au-Co〈sub〉3〈/sub〉O〈sub〉4〈/sub〉 nanocomposite thin films, in terms of optimum Au content. The metal element introduced is a unique way to create the optimum amount of oxygen vacancies in the dielectric films even in the absence of electrochemically active electrodes. Compared with pure Co〈sub〉3〈/sub〉O〈sub〉4〈/sub〉 based device, the RRAM device with Au additives showed bipolar switching behavior with uniform Set/Reset voltages, enhanced endurance of 〉10〈sup〉3〈/sup〉 cycles, and stable time-dependent resistances up to 10〈sup〉4〈/sup〉 s. The introduction of Au nanoparticles caused the oxygen vacancies based confined filament growth for optimum switching uniformity and stability. Results showed that Ohmic conduction was dominant at LRS and Schottky emission was dominated at HRS of the devices. Temperature dependence and magnetization change of various resistance states revealed that resistive and magnetic switching was due to the formation and rupture of conductive filaments of Au atoms confined oxygen vacancies with the conversion of cation valence states (Co〈sup〉2+〈/sup〉 and Co〈sup〉3+〈/sup〉). The present study suggests that Au-Co〈sub〉3〈/sub〉O〈sub〉4〈/sub〉 nanocomposite thin films have a potential for future multifunctional electromagnetic integrated device applications.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 January 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials, Volume 493〈/p〉 〈p〉Author(s): Kai Sun, Shuai Feng, Qian Jiang, Xiaofeng Li, Yaping Li, Runhua Fan, Yan An, Jiaqi Wang〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉 〈p〉The soft magnetic composites (SMCs) with high saturation magnetic flux density (〈em〉B〈/em〉〈sub〉s〈/sub〉) and low core loss (〈em〉P〈/em〉〈sub〉s〈/sub〉) have great potential in power electronics. In this work, the insulating SiO〈sub〉2〈/sub〉-Al〈sub〉2〈/sub〉O〈sub〉3〈/sub〉 layer was prepared by a hydro-thermal method to coat on the surface of the carbonyl iron powders (CIPs). Then, the coated CIPs were heterogeneously distributed in the reduced iron powders (RIPs) to fabricate the intergranular insulated SMCs. The scanning electron microscope (SEM) images and elements analysis confirmed that the surface of the CIPs was covered by a thin insulating layer forming a core-shell structure, and the Si-O-Al bond was detected by FTIR spectra. The resulting samples were annealed at 450 °C in N〈sub〉2〈/sub〉 atmosphere to eliminate the residual stress and improve magnetic properties. The annealed.〈/p〉 〈p〉SMCs containing 25 wt% CIPs@SiO〈sub〉2〈/sub〉-Al〈sub〉2〈/sub〉O〈sub〉3〈/sub〉 have optimum magnetic properties with a low 〈em〉P〈/em〉〈sub〉s〈/sub〉 of 106.9 W/kg and a highly approximate 〈em〉B〈/em〉〈sub〉s〈/sub〉 of 1.28 T (measured at 500 Hz). Compared with the conventional SMCs, the addition of the coated CIPs can suppress the adverse effect of the nonmagnetic coating layer on magnetic properties; meanwhile, the coated CIPs distributed in the RIPs can reduce the 〈em〉P〈/em〉〈sub〉s〈/sub〉. This work provides a promising approach to the development of SMCs with low hysteresis loss and optimum magnetic properties at low frequency.〈/p〉 〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 January 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials, Volume 493〈/p〉 〈p〉Author(s): Shyamaldas, M. Bououdina, C. Manoharan〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Pure cobalt ferrite nanoparticles were synthesised by hydrothermal method. Cubic spinel structure and improved crystallinity was confirmed by X-ray diffraction analysis. Morphology and average particle size within thenanorange were identified by SEM and TEM. EDX confirmed the presence of Fe, Co, and O elements without any impurities. FT-IR analysis confirmed the presence of vibrational bands in the range of 581–590 cm〈sup〉−1〈/sup〉 and 424–468 cm〈sup〉−1〈/sup〉 ascribed to Fe〈img src="https://sdfestaticassets-eu-west-1.sciencedirectassets.com/shared-assets/16/entities/sbnd"〉O and Co〈img src="https://sdfestaticassets-eu-west-1.sciencedirectassets.com/shared-assets/16/entities/sbnd"〉O bonds, respectively. The presence of five Raman active modes confirmed the cubic spinel-type structure. Optical study revealed the influence of higher annealing temperature on the band gap; it decreases from 2.60 to 1.53 eV. The dielectric constant, dielectric loss and ac-conductivity were found to varywith increasing frequency range. The shifting of cations between tetrahedral (A) to octahedral (B) sites and vice versa was revealed by Mossbauer spectroscopy. The observed sextets proposed that CoFe〈sub〉2〈/sub〉O〈sub〉4〈/sub〉 nanoparticles are highly crystalline and magnetically ordered. With increasing annealing temperature, both saturation magnetization and remanence increased, while the coercivity was reduced, which is due to the transition from single domain to multidomain on crossing the critical size of ~40 nm. The Cyclic Voltammetry (CV) test of nanoparticles annealed at 800 °C (S3) revealed excellent specific capacitance at low scan rate.〈/p〉〈/div〉 〈/div〉 〈div xml:lang="en"〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0304885319317615-ga1.jpg" width="299" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 January 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials, Volume 493〈/p〉 〈p〉Author(s): Xiangxia Wei, Yinhua Liu, Dongjie Zhao, Xuewei Mao, Wanyue Jiang, Shuzhi Sam Ge〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Net-shaped hexagonal barium and strontium ferrites with desirable shapes have been successfully fabricated by the extrusion-based three-dimensional (3D) printing. The influence of milling and calcination conditions on magnetic properties of as-printed hexaferrites are systematically investigated by vibrating sample magnetometry (VSM). The typical ferromagnetic hysteresis loops are observed, revealing that the resulting bulk ferrites derived from the preliminary milled powders are prefect hard magnetic materials. In particular, it is clear that the saturation magnetization is very close to the theoretical values after calcinations. Moreover, the coercivity can be effectively enhanced in the range of 4–6 kOe upon thermal treatment, which is a much higher value compared to ferrites prepared by the conventional ceramic processing. More importantly, the maximum energy product can be significantly improved to as high as around 2.5 MGOe for the 3D-printed strontium ferrites. This is attributed not only to fine precursor powders subjected to mechanical milling, but also to the optimized annealing for grain growth with sizes near the critical single domain limit. Overall, the fabrication of bulk ferrites derived from milled powders using the 3D printing is attractive for the large-scale applications, and may also pave the way for some specific applications, for instance, magnetic separation for nanoparticles.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Solar Energy, Volume 190〈/p〉 〈p〉Author(s): Vikash Kumar〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Thermal and thermohydraulic performance characteristics for 3-sides concave dimple roughened collector has been investigated and presented here. The geometrical parameter of roughness element covers relative dimple pitch, height and depth 8–15, 0.018–0.045 and 1–2 respectively along with flow Reynolds number 2500–13,500. Thermal performance of artificially roughened SAH doesn’t include a frictional loss that is generated while the air is propelled through the roughened ducts. Three sides roughened ducts have high thermal efficiency compared to 1-side roughened duct but that hike should not come at the cost of tremendous rise in frictional losses. The present investigation is aimed at determining the optimum roughness parameters at which maximum possible efficiency is obtained at minimum frictional losses. The optimum roughness parameter yielding the maximum thermal efficiency is ‘p/e’ = 12, ‘e/D〈sub〉h〈/sub〉’ = 0.036 & ‘e/d’ = 1.5 for both ducts. 3-sides concave dimple roughened SAH were having 44–67% more thermal efficiency than 1-side roughened duct under similar flow condition. Maximum effective (thermohydraulic) efficiency at varying ‘e/D〈sub〉h〈/sub〉’ obtained was 0.78 and 0.49 and that at varying ‘p/e’ obtained was 0.74 and 0.47 in the case of 3-sides and 1-side roughened ducts respectively.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Solar Energy, Volume 190〈/p〉 〈p〉Author(s): Hai Yang, Jingge Song, Boshu He, Guangchao Ding〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The charging characteristics of a cylindrical Encapsulated Phase Change Material (EPCM) capsule with embedded heat pipe (HP) is investigated numerically for latent heat storage. For the heat pipe-assisted capsule, called EPCM-HP unit, a 3-D transient thermal storage model is implemented combining Lumped Thermal Resistance Network (LTRN) as the heat pipe model with conventional enthalpy-porosity approach as phase change model. The effects of flow conditions (laminar and turbulent), heat pipe condenser length and types of HTFs (Therminol/VP-1 and air) on thermal characteristics of the EPCM-HP unit are simulated, respectively. Results show that embedding heat pipe can reduce the total charging time by 11.26%. The charging process under turbulent flow is more than 10 times faster than that under laminar flow. Increasing the condenser length of heat pipe cannot effectively reduce the charging time of ECPM-HP unit since the thermal resistance also increases and the starting time of convection is delayed. The results also reveal that Therminol/VP-1 (high 〈em〉Pr〈/em〉 HTFs) can charge thermal energy faster than air (low 〈em〉Pr〈/em〉 HTFs), while the enhancement effect of heat pipe is more significant when using air (low 〈em〉Pr〈/em〉 HTFs).〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Solar Energy, Volume 190〈/p〉 〈p〉Author(s): Thomas Baumann, Hartmut Nussbaumer, Markus Klenk, Andreas Dreisiebner, Fabian Carigiet, Franz Baumgartner〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉 〈p〉Dependent on the specific conditions flat roofs can be well suited for the installation of large photovoltaic systems in urban areas. For urban designers also other aspects, such as the insulation of buildings, cooling, air purification and water retention play an important role besides the ecological energy generation. The combination of photovoltaics and roof greening can therefore be an interesting fusion. It combines the advantages of a green roof with the local electrical energy production at the place of consumption.〈/p〉 〈p〉However, using a conventional photovoltaic system with tilted modules in south or east-west direction on a green roof causes problems, as typical low tilt angels and high ground coverage rates result in an almost complete coverage of the roof surface. Plants, growing in between the covered areas provoke undesirable shading of the collector surface. Only a frequent maintenance procedure, complicated by dense PV system layouts, can avoid a reduction of the energy yield in the course of time.〈/p〉 〈p〉Vertically mounted specially designed bifacial modules are an option to realize photovoltaic power generation in combination with a functional green roof at low maintenance costs. In this paper, we report on the layout and the energy yield of a corresponding system. Custom-made bifacial modules with 20 cells were produced and vertically installed in landscape orientation. The narrow layout of the modules lowers the wind load and reduces the visibility. The enhanced power in the morning and evening of vertically east-west installed modules can additionally lead to higher self-consumptions rates.〈/p〉 〈p〉Despite having some shading and undergrounds with albedo factors of less than 0.2, the bifacial installation with a rated power of 9.09 kWp achieved a specific yield of the 942 kWh/kWp in one year (11.08.2017–10.08.2018). This is close to typical values of 1000 kWh/kWp achieved for south-facing PV systems in the same region.〈/p〉 〈p〉The impact of the greening on the albedo and the system performance is investigated in more detail with two smaller sub-systems. The energy yields of the two bifacial sub-systems are compared to a monofacial, south-facing reference module. The use of silver-leaved plants in this system resulted in higher albedo values and a more resilient roof greening.〈/p〉 〈/div〉 〈/div〉 〈div xml:lang="en"〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0038092X19307844-ga1.jpg" width="300" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 December 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials, Volume 491〈/p〉 〈p〉Author(s): Aquil Ahmad, S.K. Srivastava, A.K. Das〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The generalized gradient approximation (GGA) scheme in the first-principles calculations is used to study the effect of L2〈sub〉1〈/sub〉 and XA ordering on the phase stability, half-metallicity and magnetism of Co〈sub〉2〈/sub〉FeAl (CFA) Heusler alloy. Various possible hypothetical structures: L2〈sub〉1〈/sub〉-I, L2〈sub〉1〈/sub〉-II, XA-I, and XA-II are prepared under the conventional L2〈sub〉1〈/sub〉 and inverse XA phases by altering the atomic occupancies at their Wyckoff sites. It is found that the XA-II phase of CFA is the most stable phase energetically among all the structures. The electronic structure calculations without U show the presence of half-metallic (HM) ground state only in L2〈sub〉1〈/sub〉-I structure and the other structures are found to be metallic. However, the electronic structures of CFA are significantly modified in the presence of U, although the total magnetic moments per cell remained the same and consistent with the Slater-Pauling (SP) rule. The metallic ground states of CFA in L2〈sub〉1〈/sub〉-II and XA-II structures are converted into the half-metallic ground states in presence of U but remained the same (metallic) in XA-I structure. The results indicate that the electronic structures are not only dependent on the L2〈sub〉1〈/sub〉 and XA ordering of the atoms but also depend on the choice of U values. So experiments may only verify the superiority of GGA + U to GGA.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Solar Energy, Volume 190〈/p〉 〈p〉Author(s): Hanbing Ling, Rui Zhang, Xiaoqin Ye, Zhiyue Wen, Jiangbin Xia, Xing Lu〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Here, an organic-inorganic hybrid thin film of PEDOT/V〈sub〉2〈/sub〉O〈sub〉5〈/sub〉 complex was successfully obtained via an in-situ synthesis method. In detail, PEDOT buffer layer was prepared by in-situ oxidative polymerization. Then, a layer of V〈sub〉2〈/sub〉O〈sub〉5〈/sub〉 nanoparticles was deposited on it. V〈sub〉2〈/sub〉O〈sub〉5〈/sub〉 nanoparticles can closely combine with PEDOT and modifying the surface defects of PEDOT. For the control polymer solar cells (PSCs) with a PEDOT:PSS hole transport layer (HTL), a power conversion efficiency (PCE) of 3.50% is obtained. Encouragingly, a higher PCE of 3.76% is achieved for the cell using the as-prepared PEDOT/V〈sub〉2〈/sub〉O〈sub〉5〈/sub〉 as the HTL, which increased by 8% than that of the control device. Furthermore, the devices with PEDOT/V〈sub〉2〈/sub〉O〈sub〉5〈/sub〉 show a better stability than the control devices using PEDOT:PSS as HTL. The results indicate that PEDOT/V〈sub〉2〈/sub〉O〈sub〉5〈/sub〉 is an excellent HTL for efficient and stable PSCs.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Solar Energy, Volume 190〈/p〉 〈p〉Author(s): Nelson Sommerfeldt, Hatef Madani〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The electrification of buildings is a promising pathway to the decarbonization of cities. This is a parametric study of the technical and economic performance of ground source heat pump (GSHP) systems with series connected solar PV/thermal (PVT) collectors. The focus is on multi-family houses (MFH) in the heating dominated climate of Sweden, where land restrictions for boreholes or noise restrictions on air heat exchangers limit the heat pump market. System efficiency and lifecycle cost results are generated using a holistic and detailed systems model in TRNSYS with 20 year simulations. The results show that PVT can reduce borehole length by 18% or spacing by 50% while maintaining an equivalent seasonal performance factor to systems without PVT. The cost for PVT+GSHP systems is higher than a traditionally designed PV+GSHP, however this does not take into account the value of the land area saved by PVT, which can be up to 89%. The reduction in land enabled by PVT has the potential to increase penetration of GSHP in MFH and promote solar energy diffusion in high latitude markets.〈/p〉〈/div〉 〈/div〉 〈div xml:lang="en"〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0038092X19307510-ga1.jpg" width="334" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 January 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials, Volume 493〈/p〉 〈p〉Author(s): I.V. Kozlov, G.N. Elmanov, K.E. Prikhodko, L.V. Kutuzov, B.A. Tarasov, V.V. Mikhalchik, R.D. Svetogorov, V.S. Mashera, E.S. Gorelikov, S.A. Gudoshnikov〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Amorphous Co〈sub〉69〈/sub〉Fe〈sub〉4〈/sub〉Cr〈sub〉4〈/sub〉Si〈sub〉12〈/sub〉B〈sub〉11〈/sub〉 glass-coated microwires after heat treatment in the temperature range of 250–600 °C during 30 min were investigated. Changes of microstructure, phase composition, fracture morphology, and giant magnetoimpedance (GMI) properties were shown. It is confirmed that a significant increase in the GMI effect was possible not only due to the structural relaxation, but also as a result of phase transformations at the temperature close to the onset of crystallization. It is shown that at the very initial stage of the nucleation of Co nanocrystals, a sharp increase in circumferential diagonal GMI component was observed, a further increase in the amount of the crystalline Co phase was accompanied by degradation of this effect. The most significant GMI ratio was obtained for microwires annealed at 430 °C. At 450 °C and above, an irreversible decrease of the GMI ratio took place. It was caused by the formation of Co crystals, decrease in amount and composition change of the amorphous phase during primary and secondary crystallization. At the final stage of the Co crystals segregation the secondary crystallization of the residual amorphous phase occurred with formation of a metastable τ-phase with a Me〈sub〉23〈/sub〉B〈sub〉6〈/sub〉 type structure. Thermal stability of the τ-phase was analyzed.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 December 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials, Volume 492〈/p〉 〈p〉Author(s): S. Pütter〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The thickness-driven spin-reorientation transition of Co/Au(1 1 1) is studied via 〈em〉in situ〈/em〉 Kerr microscopy. On varying the premagnetization conditions in external field of in-plane or normal orientation, the magnetic switching into a final remanent state from an in-plane field is investigated. The quantitative analysis of the Kerr rotation derived from Kerr microscopy images allows the determination of the population of different magnetic phases as a function of thickness. Coexisting magnetic phases with preferred in-plane and out-of-plane magnetization orientation are identified. The overall switching behaviour is explained by thermal activation of magnetic domains. We show that there is a population of orthogonal bistable magnetic domains, which can be remanently switched between out-of-plane and in-plane orientation by the appropriate magnetic field. This quantity is related to the intersection of the population of states for in-plane and out-of-plane magnetization.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 December 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials, Volume 492〈/p〉 〈p〉Author(s): R. Peña-Garcia, Y. Guerra, F.E.P. Santos, L.C. Almeida, E. Padrón-Hernández〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉We present a study about the structural and magnetic properties of Ni-doped yttrium iron garnet nanopowders synthesized by sol-gel. The Rietveld refinement of the X-ray diffractograms indicates the replacement of Fe by Ni in the tetrahedral (〈em〉d〈/em〉) and octahedral (〈em〉a〈/em〉) sites of yttrium iron garnet (YIG) structure. The lattice parameter showed variation associated to the effects of Ni inclusion and structural defects, such as, oxygen vacancies. The morphological analysis evidence particles with a cylindrical shape and the Energy Dispersive Spectroscopy results corroborate the presence of Ni. The average porosity suggests that the replacement of Fe by Ni does not substantially change the textural properties of the particles. The Fourier transform infrared and Raman spectroscopies showed the characteristic absorption bands of YIG and confirmed the substitution in the 〈em〉a〈/em〉-sites and 〈em〉d〈/em〉-sites. The saturation magnetization was studied from the hysteresis loops measurements and present variations with the dopant concentration, associated to the replacement of Fe by Ni and to the oxygen vacancies occurrence. Changes in the coercive field for different dopant concentration were associated to the particle size and pinning centers existence.〈/p〉〈/div〉 〈/div〉 〈div xml:lang="en"〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0304885318328610-ga1.jpg" width="379" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 3 August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials〈/p〉 〈p〉Author(s): Michał Kozanecki, Czesław Rudowicz〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Recent developments in high-magnetic field/high-frequency electron magnetic resonance (HMF-EMR) techniques offer improved capabilities for determination of the spin Hamiltonian (SH) parameters, including the fourth-rank zero field splitting (ZFS) parameters (ZFSPs) for spin 〈em〉S̃〈/em〉 = 2 systems. However, the density functional theory (DFT) and ab-initio methods provide predictions of the ZFS energies from which usually only the second-rank ZFSPs are obtained. Here we present an analytical method for determination of the fourth-rank ZFSPs from the ZFS energy levels for 〈em〉S̃〈/em〉 = 2 ions at orthorhombic sites. This enables assessment of their significance and determination of the dominant parameters. Applications of this method for Fe〈sup〉2+〈/sup〉 in [Fe(H〈sub〉2〈/sub〉O)〈sub〉6〈/sub〉](NH〈sub〉4〈/sub〉)〈sub〉2〈/sub〉(SO4)〈sub〉2〈/sub〉, Fe〈sup〉2+〈/sup〉 in forsterite (Fe〈sup〉2+〈/sup〉:Mg〈sub〉2〈/sub〉SiO〈sub〉4〈/sub〉), and Cr〈sup〉2+〈/sup〉 ions in (ND〈sub〉4〈/sub〉)〈sub〉2〈/sub〉Cr(D〈sub〉2〈/sub〉O)〈sub〉6〈/sub〉(SO〈sub〉4〈/sub〉)〈sub〉2〈/sub〉 and Rb〈sub〉2〈/sub〉Cr(D〈sub〉2〈/sub〉O)〈sub〉6〈/sub〉(SO〈sub〉4〈/sub〉)〈sub〉2〈/sub〉 indicate important role the fourth-rank ZFSPs. The analytical formulas derived by us may be applied to other 3d〈sup〉6〈/sup〉 and 3d〈sup〉4〈/sup〉 (〈em〉S̃〈/em〉 = 2) ions at orthorhombic sites in various hosts for better modeling of spectroscopic and magnetic properties of these systems.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 December 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials, Volume 492〈/p〉 〈p〉Author(s): Kingshuk Mallick, Aditya A. Wagh, P.S. Anil Kumar〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉We observe an exchange bias at low temperatures in polycrystalline ferrimagnetic MgFe〈sub〉2〈/sub〉O〈sub〉4〈/sub〉 (MFO) films grown on Si(100), emerging from Antiferromagnetic (AFM)-like interactions at defect sites, concentrated predominantly at the grain boundaries. In this report, we show it is possible to utilize these AFM interactions to get enhanced spin transport utilizing the spin Seebeck effect (SSE). The temperature dependence of the SSE signal in two films with different defect densities allowed us to identify a unique temperature window for both films where an enhanced SSE signal was observed. Such enhancement has been reported in different Ferromagnet (FM)/AFM bilayer systems, but its observation in a single layer hosting both FM-AFM interactions makes our results attractive. Temperature dependent SQUID magnetometry revealed two distinct regions of strong and weak coupling for the FM-AFM interactions. The weak coupling region is characterized by a distribution of AFM energy barriers (〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si7.svg"〉〈mrow〉〈mi mathvariant="normal"〉Δ〈/mi〉〈/mrow〉〈/math〉E), which can modify the spin conductance across the FM-AFM boundary and hence, affect the spin transport. Indeed, we find that the same functional form fits both the 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si8.svg"〉〈mrow〉〈mi mathvariant="normal"〉Δ〈/mi〉〈/mrow〉〈/math〉E distribution and the SSE temperature evolution for both films. This study should aid in the understanding of SSE in the large class of polycrystalline materials with inherent growth induced defect densities and illustrate the significance of magnetically disordered phases in spin transport.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 December 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials, Volume 492〈/p〉 〈p〉Author(s): Takahide Kubota, Zhenchao Wen, Koki Takanashi〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉A half-metal is an ideal spin source to realize extremely large magnetoresistance effects because of the completely spin-polarized density of states at the Fermi level, and Heusler alloy is a material class for which several compositions are known to exhibit half-metallic properties. Current perpendicular-to-plane (CPP) giant magnetoresistance (GMR) effect is a resistance change that depends upon the relative angle of the magnetization vectors in magnetic layers separated by thin non-magnetic layer(s), which can be utilized for magnetic sensor applications. Over the last decade, the resistance change of CPP-GMR has been found to enhance greatly when using half-metallic Heusler alloys. In this article, the history of Heusler alloy based CPP-GMR is briefly reviewed, including the authors’ recent results on the analysis of the spin asymmetry coefficients based on the Valet-Fert model. Finally, the degradation of half-metallic spin polarization at interfaces is discussed and a future prospect is described.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 3 August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Magnetism and Magnetic Materials〈/p〉 〈p〉Author(s): M. Ozcan, S. Ozen, M. Yagmurcukardes, H. Sahin〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Novel stable ultra-thin phases of europium oxide are investigated by means of state-of-the-art first principles calculations. Total energy calculations show that single layers of EuO〈sub〉2〈/sub〉 and Eu(OH)〈sub〉2〈/sub〉 can be stabilized in an octahedrally coordinated (1T) atomic structure. However, phonon calculations reveal that although both structures are energetically feasible, only the 1T-EuO〈sub〉2〈/sub〉 phase has dynamical stability. The phonon spectrum of 1T-EuO〈sub〉2〈/sub〉 displays three Raman active modes; a non-degenerate out-of-plane 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si1.svg"〉〈mrow〉〈msub〉〈mrow〉〈mi mathvariant="normal"〉A〈/mi〉〈/mrow〉〈mrow〉〈mn〉1〈/mn〉〈mi〉g〈/mi〉〈/mrow〉〈/msub〉〈/mrow〉〈/math〉 mode at 353.5 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si2.svg"〉〈mrow〉〈msup〉〈mrow〉〈mtext〉cm〈/mtext〉〈/mrow〉〈mrow〉〈mo〉-〈/mo〉〈mn〉1〈/mn〉〈/mrow〉〈/msup〉〈/mrow〉〈/math〉 and two doubly-degenerate in-plane 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si3.svg"〉〈mrow〉〈msub〉〈mrow〉〈mi mathvariant="normal"〉E〈/mi〉〈/mrow〉〈mrow〉〈mi〉g〈/mi〉〈/mrow〉〈/msub〉〈/mrow〉〈/math〉 modes at 304.3 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si4.svg"〉〈mrow〉〈msup〉〈mrow〉〈mtext〉cm〈/mtext〉〈/mrow〉〈mrow〉〈mo〉-〈/mo〉〈mn〉1〈/mn〉〈/mrow〉〈/msup〉〈/mrow〉〈/math〉. Furthermore, magnetic ground state and electronic band dispersion calculations show that the single layer EuO〈sub〉2〈/sub〉 is a metal with net magnetic moment of 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si5.svg"〉〈mrow〉〈msub〉〈mrow〉〈mn〉5〈/mn〉〈/mrow〉〈mrow〉〈mi〉μ〈/mi〉〈mi〉B〈/mi〉〈/mrow〉〈/msub〉〈/mrow〉〈/math〉 per unitcell resulting in a half-metallic ferrimagnetic behavior. Moreover, robustness of the half-metallic ferrimagnetic characteristics of EuO〈sub〉2〈/sub〉 is confirmed by the application of electric field and charging. Single layer 1T-EuO〈sub〉2〈/sub〉, with its stable ultra-thin structure and half-metallic ferrimagnetic feature, is a promising novel material for nanoscale electronic and spintronic applications.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 European Polymer Journal, Volume 119〈/p〉 〈p〉Author(s): Andrés Felipe Chamorro Rengifo, Natalia Marcéli Stefanes, Jessica Toigo, Cassiana Mendes, Débora Fretes Argenta, Marta Elisa Rosso Dotto, Maria Cláudia Santos da Silva, Ricardo José Nunes, Thiago Caon, Alexandre Luis Parize, Edson Minatti〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Intact carboxymethyl-hexanoyl chitosan/dodecyl sulfate nanoparticles loaded with pyrazoline H3TM04 were dispersed in biodegradable PEO-chitosan nanofiber mats (PEOChNps) for application in skin cancer treatment. The nanomaterial was formed by co-electrospinning in aqueous solution. The structural and morphological properties of the PEOChNps were investigated by FEG-SEM, TEM, AFM, FTIR, DSC and TGA. The PEOChNps nanofibers showed a narrow size distribution (197.8 ± 4.1 nm) with a homogenous distribution of the nanoparticles inside the nanofibers, promoting the controlled release of H3TM04 from both diffusion and erosion processes over a period of 120 h. An increased transport rate of H3TM04 through the epidermis was also found when PEOChNps was used as the carrier. In 〈em〉in vitro〈/em〉 cytotoxicity assays, the incorporation of H3TM04 into the nanocarriers increased its cytotoxic effect toward B16F10 melanoma cells. These findings suggest that the proposed nanofiber mats could be used for controlled drug release in local chemotherapy treatment for skin cancer.〈/p〉〈/div〉 〈/div〉 〈div xml:lang="en"〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0014305719311279-ga1.jpg" width="500" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉 〈/div〉