ALBERT

Description: Ba x Sr 1− x Fe 12 O 19 /Fe 3 O 4 /polyacrylic acid/polythiophene (Ba x Sr 1− x Fe 12 O 19 /Fe 3 O 4 /PAA/PTh) nanocomposites with multi-core–shell structure were successfully synthesized by four steps. The samples were characterized by FTIR, X-ray diffraction (XRD), transmission electron microscope (TEM), vibrating sample magnetometer, and radar absorbing material reflectivity far-field radar cross-section method, respectively. XRD and TEM results indicated that the obtained nanoparticles have multi-core–shell morphology. The magnetic properties and microwave absorption analyses reveal that there are interphase interactions at the interface of Ba x Sr 1− x Fe 12 O 19 , Fe 3 O 4 , PAA, and PTh, which can affect the magnetic properties and microwave absorption properties of the samples. The microwave-absorbing properties of nanocomposites were investigated at 8–14 GHz. A typical layer absorber exhibited an excellent microwave absorption with a −26 dB maximum absorption at 14 GHz. Compared with core material, the coercivity and saturation magnetization of multi-core–shell nanocomposites decrease obviously, but the microwave absorption properties of nanocomposites are improved greatly. The results show that these composite could be used as advancing absorption and shielding materials due to their favorable microwave-absorbing properties.

Description: This paper presents a simplified model of a terminal mobile where a monopole antenna is associated with three different metamaterials: artificial magnetic conductor (AMC), electromagnetic band gap and resistive high-impedance surface (RHIS). The objective is to evaluate what is the metamaterial which is the best solution to reduce exposure. The exposure has been evaluated using a simplified phantom model. Results show that both AMC and RHIS reduce the exposure preserving the antenna performances. A reduction of 23 % of specific absorption rate 10 g has been obtained when the monopole is associated with an optimized RHIS structure. Antenna with and without metamaterials has been realized. The experimental results confirm the performances given by simulation in terms of impedance matching and radiation.

Description: The annealing effects of c -plane sapphire (α-Al 2 O 3 ) substrate with a vicinal-cut angle of α  = 0.25° toward the a -plane \(\left( {11\overline{2} 0} \right)\) on the quality of epitaxial ZnO films grown by metal organic chemical vapor deposition were studied. The atomic steps formed on sapphire substrate surface by annealing at high temperature were analyzed by atomic force microscopy (AFM). The annealing effects of sapphire substrate on the microstructural and optical properties of the ZnO films were examined by high-resolution X-ray diffraction, scanning electron microscopy, AFM and photoluminescence spectroscopy. Experimental results indicate that the film quality is strongly affected by annealing treatment of the sapphire substrate. X-ray diffraction study revealed that ZnO films deposited on c -plane sapphire substrate annealed at T  ≥ 1050 °C exhibit a wurtzite phase and have a c -axis orientation. The decrease in FWHM for (0004) and \(\left( {10\overline{1} 4} \right)\) ZnO peak confirms the improvement of the crystalline quality of ZnO thin film as increasing annealing substrate temperature. Sapphire annealing at 1100 °C for 3 h under oxygen prior to ZnO film growth is the best to achieve ZnO film with good structural and optical quality.

Description: Determination of phosphorus and boron concentrations in Czochralski-grown silicon wafer-thick samples has been examined by means of low-temperature high-resolution far-infrared transmission measurements with p -polarized light incident at Brewster angle. The measurements were taken at about 8.7 K with a spectral resolution of 0.5 cm −1 under halogen light illumination. Linear correlations are clearly obtained between the absorption coefficients of several phosphorus and boron transitions and their concentrations, which are approximately in the range of 7.7 × 10 13 –1.6 × 10 15  atoms cm −3 for phosphorus and of 2.5 × 10 14 –7.6 × 10 14  atoms cm −3 for boron. The correlations are obtained regardless of the surface processing conditions of the samples. These are because interference fringes due to internal multiple reflections in wafer-thick silicon samples are almost suppressed using this incidence. The detection limit of phosphorus is about 1.2 × 10 13  atoms cm −3 and that of boron is about 4.2 × 10 13  atoms cm −3 . P -polarized Brewster angle incidence has made it possible to determine phosphorus and boron concentrations in wafer-thick samples.

Description: Nanocrystalline CeO 2 /C 3 N 4 was synthesized via a one-step solution combustion method using urea as fuel for the first time. The effects of the molar ratio of urea to cerium chloride on the photocatalytic activity of the synthesized samples were investigated. The synthesized nanocrystalline CeO 2 /C 3 N 4 shows small size and large surface exposure area. Photocatalytic degradation of methylene blue demonstrates that the synthesized nanocrystalline CeO 2 /C 3 N 4 possesses enhanced photocatalytic activity. It is proposed that the enhanced photocatalytic activity might be related to the favorable morphology and structure, and the effective charge separation between C 3 N 4 and CeO 2 in the photocatalytic process.

Description: Vertical MBE- and MOCVD-grown \({n}^{+}/{n}\hbox {-GaAs}/\hbox {Al}_{0.25}\hbox {Ga}_{0.75}\hbox {As}\) structures used for microwave electronics have been studied with continuous wave and time-correlated single photon counting dynamic photoluminescence technique. The photoluminescence spectra and light emission lifetimes are used to explain the recombination mechanisms of the excited carriers. This paper presents results showing the differences in recombination characteristics of \({n}^{+}\hbox {-Al}_{0.25}\hbox {Ga}_{0.75}\hbox {As}\) layers grown using MBE process compared with MOCVD process. One of these differences is that the PL spectrum of the MOCVD-grown layer is shifted towards the forbidden energy gap region, as well as the characteristic recombination time is longer than for the MBE-grown sample. This peculiarity can be attributed to the formation of the localised band tails in the \({n}^{+}\hbox {-Al}_{0.25}\hbox {Ga}_{0.75}\hbox {As}\) MOCVD-grown sample. The proposed analytical model explains the differences in microwave detection properties of the samples grown by MBE and MOCVD processes.

Description: Hybrid nanocomposites of II–VI semiconductor nanoparticles are gaining great interest in nonlinear optoelectronic devices. Present work includes the characterization of CdSe polymer nanocomposite prepared by chemical in situ technique. From X-ray diffraction, the hexagonal wurtzite structure of nanoparticles has been confirmed with spherical morphology from transmission electron microscopy. Ag–CdSe hybrid polymer nanocomposite has been prepared chemically at different Ag concentrations. The presence of Ag in hybrid nanocomposite has been confirmed with energy-dispersive X-ray spectroscopy. The effect of varying Ag concentration on the linear and nonlinear optical properties of the nanocomposites has been studied. In linear optical parameters, the linear absorption coefficient, refractive index, extinction coefficient and optical conductivity have been calculated. The third-order nonlinear optical properties have been observed with open- and closed-aperture Z-scan technique. The large nonlinear refractive index ~10 −5  cm 2 /W with self-focusing behaviour is due to the combined effect of quantum confinement and thermo-optical effects. The enhanced nonlinearity with increasing Ag content is due to the surface plasmon resonance, which enhances the local electric field near the nanoparticle surface. Thus, Ag–CdSe hybrid polymer nanocomposite has favourable nonlinear optical properties for various optoelectronic applications.

Description: The effect of doping palladium (Pd) at the Cu site of CaCu 3 Ti 4 O 12 powders (CCPTO) synthesized by sol–gel technique on electrical properties was studied. XRD analysis revealed the formation of CCTO and CCPTO ceramics with some minor quantities of impurities. SEM micrographs revealed that the grain size decreased with Pd doping. TEM micrographs of CCPTO powder showed the formation of irregular-shaped particles of ~40 nm. The dielectric constant and dielectric loss showed a significant enhancement with Pd doping. A significant decrease in grain-boundary resistance with Pd doping was ascertained by impedance spectroscopy study.

Description: This work focuses on the composition and microstructure of the lead white pigment employed in a set of paintworks, using a combination of µ-XRD and 2D scanning XRF, directly applied on five drapery studies attributed to Leonardo da Vinci (1452–1519) and conserved in the Département des Arts Graphiques , Musée du Louvre and in the Musée des Beaux - Arts de Rennes . Trace elements present in the composition as well as in the lead white highlights were imaged by 2D scanning XRF. Mineral phases were determined in a fully noninvasive way using a special µ-XRD diffractometer. Phase proportions were estimated by Rietveld refinement. The analytical results obtained will contribute to differentiate lead white qualities and to highlight the artist’s technique.

Description: Easel paintings on canvas are subjected to alteration mechanisms triggered or accelerated by moisture. For the study of the spatial distribution and kinetics of such interactions, a moisture exposure chamber was designed and built to perform neutron radiography experiments. Multilayered sized and primed canvas samples were prepared for time-resolved experiments in the ICON cold neutron beamline. The first results show that the set-up gives a good contrast and sufficient resolution to visualise the water uptake in the layers of canvas, size and priming. The results allow, for the first time, real-time visualisation of the interaction of water vapour with such layered systems. This offers important new opportunities for relevant, spatially and time-resolved material behaviour studies and opens the way towards numerical modelling of the process. These first results show that cellulose fibres and glue sizing have a much stronger water uptake than the chalk–glue ground. Additionally, it shows that the uptake rate is not uniform throughout the thickness of the sized canvas. With prolonged moisture exposure, a higher amount of water is accumulating at the lower edge of the canvas weave suggesting a decrease in permeability in the sized canvas with increased water content.

Description: Titanium dioxide thin films were coated on soda-lime glass substrates using spray pyrolysis method with a thickness of 152 ± 10 nm. The films were irradiated with hydrogen ions at room temperature at various beam energies and fluences. Optimized incident beam energy and beam fluence were obtained to improve photocatalytic and hydrophilicity properties of TiO 2 thin films by narrowing the band gap. Samples were characterized by scanning electron microscopy to study the surface morphology and by UV–Vis absorption spectroscopy to measure the band gap. The optical band gap of H-doped anatase TiO 2 thin films irradiated with hydrogen beam with energies of 2 and 4 keV and a fluence of 10 15 ions/cm 2 was narrowed from 3.34 eV (before irradiation) to 3.04 and 2.92 eV (after irradiation), respectively. The irradiated sample with energy of 4 keV with a fluence of 10 15 ions/cm 2 has the best improvement. This is attributed to the contraction of the band gap and to the increase in surface active site. Furthermore, it was observed that photocatalytic and hydrophilicity properties of this sample were improved, as well.

Description: In this paper, nanocrystalline ZnO film with porous structure was successfully prepared on alumina substrate by the technology of screen printing and the subsequent heat treatment. The fundamental characteristics of the as-prepared sample were examined through XRD, FE-SEM, EDX and PL spectra measurements. Meanwhile, photoelectric responses of it were tested under UV and white light irradiation, respectively. Different photocurrent curves were obtained. Under UV light, the photocurrent with comparatively high amplitude of each cycle could mostly recover upon the light off. While for white light, the photocurrent with low amplitude just partially recovered when the light was turned off. This phenomenon indicated that, after the white light off, a large number of free electrons still remained within the materials. To calculate the amount of the remained free electrons, three photocurrent parameters, which are related to the density of free electrons in ZnO, were defined for the first time. Furthermore, the explanations for the different photoelectric responses of ZnO based on the double Schottky barrier model were also proposed.

Description: The evolution of the microstructure and texture of Cu-2.7Be alloys during hot rolling was investigated and related to the mechanical properties of the resulting sheets. Hot cross-rolling is shown to be an effective way to refine the hard and brittle secondary-phase particles in Cu-2.7Be alloys. The Cu- and brass-type textures increase and decrease in prevalence, respectively, during the rolling process. The yield strengths along the first and second rolling directions, and 45° to the former, are all enhanced because the corresponding Schmid factors decrease as the sheets are rolled thinner. The ductility anisotropy of the as-rolled sheets is related to the distribution and shape of the secondary-phase particles therein.

Description: Novel In 2 O 3 /BiVO 4 heterojunction composite photocatalysts with tunable In 2 O 3 content were prepared using a mild hydrothermal method. The structure, composition, and optical properties of the In 2 O 3 /BiVO 4 composites were determined by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, UV–Vis diffuse reflectance spectroscopy, Brunauer–Emmett–Teller surface analysis, and X-ray photoelectron spectroscopy. Furthermore, photocatalytic activities of the as-prepared composites were investigated by studying the degradation of methylene blue (MB) solutions under simulated visible light irradiation ( λ  〉 420 nm). It was found that the 50 % proportion of In 2 O 3 in the In 2 O 3 /BiVO 4 composite exhibited the highest photocatalytic performance, leading to 91 % decomposition of MB within 240 min of irradiation.

Description: Photovoltaic Cu 2 ZnSnS 4 (CZTS) thin films have been deposited on the glass substrate by a simple and low-cost spray pyrolysis technique without sulfurization treatment in a toxic atmosphere. The influence of the substrate temperatures on the structural, compositional, morphological, optical and electrical properties of the CZTS films was investigated. The formation of kesterite structure in the films was confirmed using X-ray diffraction measurements. The improved crystallinity of the CZTS with a (112) orientation was observed with increasing the substrate temperature. The band gap of all films was found to be in the range from 1.44 to 1.56 eV which is close to the ideal band gap for the highest theoretical conversion efficiency of solar cell. AFM analysis revealed a smooth, compact and crack-free morphology. The electrical studies showed that all these samples had a p-type conductivity, and the free hole density and mobility increased with increasing the substrate temperature.

Description: The various Co 2 MnSi films, from chemical ordered L 2 1 state to completely disordered amorphous state, were prepared on glass substrates with different deposition/annealing temperatures. The influence of deposition/annealing temperature on the crystallographic defects and atomic disorders, and further on the magnetic and transport properties of the Co 2 MnSi films were investigated in detail. The decrease in crystallinity leads to the structure disorder, spin disorder and further the reduction of magnetization as well as the increase of residual resistivity. The dominant source in anomalous Hall effect for the polycrystalline samples is the skew scattering, while the skew scattering coefficient a becomes larger with the increasing deposition temperature, due to the increase of skew scattering center introduced by the increasing structure disorder.

Description: The luminescence of a nitrogen-vacancy (NV) center in a nanodiamond (ND) is of great interest because of its features, especially in the field of nanophotonics. When an NV center in an ND is located in the vicinity of the surface, the emission is often disturbed by any surface defects, resulting in non-radiative recombination. In this work, we performed dressed photon–phonon (DPP) etching of the NDs, and found that the size of the NDs decreased, while the cathodoluminescence (CL) intensity increased. We assume that this increase in the CL intensity originates from the removal of the surface protrusions and/or defects by DPP etching.

Description: This paper has investigated the dynamic behavior of a cylindrically shaped DNA nanoparticle during its displacement on a rough substrate by an atomic force microscope. Due to the cylindrical geometry of the DNA nanoparticle, two multi-asperity models have been considered for the adhesion between nanoparticle and rough substrate. The two selected models for the contact between smooth and rough surfaces have been further developed for cylindrical geometries. One of these models is analytical and based on uniform asperities and the other one is based on random asperities. Also, in each of these models, the real area of contact between particle and rough substrate has been calculated based on the number of asperities in contact. Then, a 3D dynamic model for the manipulation of cylindrical nanoparticle on rough substrate has been developed and simulated. The maximum difference between the results obtained from the two multi-asperity models is 〈5 %, indicating a good agreement between the two models. The comparison of critical forces indicates that the critical force necessary for moving a particle is smaller for rough substrates than for smooth substrates and larger compared to the critical force obtained from the Rabinovich model, which is single-asperity model. Finally, the surface roughness parameters were estimated from the topographic images, and the manipulation process was simulated for these substrates by developing the relevant equations. The obtained results indicated that the critical force for a substrate with a higher root-mean-square roughness is smaller and particles can be moved easier on such a substrate.

Description: Electropulsing treatment is a practical method to arrest crack propagation. The microstructure characterization and research on the forming mechanism are difficult due to the small affected area (0.01–1 mm 2 ), high-temperature gradient (10 2  K/mm) and change rate (10 4 –10 7  K/s). In this paper, the 1045 steel plate with a preexisting crack subjected to high-voltage pulses was investigated. The surface morphologies and microstructure around the crack tip were observed using optical microscopy and scanning electron microscopy. Experimental results showed that the material around the tip melted, splashed and blunted under electropulsing treatment. The microstructure around the molten hole was divided into four distinct regions. An electro-thermal coupled model considering material ejection, cavity formation, current oscillation and temperature-dependent material properties was proposed to investigate the dynamic formation process of molten hole and gradient microstructure. The uneven temperature distribution, high cooling rate and insufficient carbon diffusion led to the formation of gradient microstructure.

Description: Nanostructured metallic backside reflectors (BSRs) are crucial for enhanced optical absorption in thin-film amorphous silicon solar cells. The structural fabrication based on rapid aluminum (Al) anodization has a potential for roll-to-roll processes, which are promising for low-cost and large-scale fabrication of BSRs. In this regard, the short fabrication time via appropriate choice of acid, acid concentration, temperature, and time-dependent voltage control is very important. In addition, we first demonstrate the trimming of structural height by using conventional Al anodization, so the best pore size of BSRs with the same structural height can be determined. According to integrated external quantum efficiency (IEQE) calculations, the nanostructured BSR with 430-nm pore size shows 51.6 % IEQE improvement compared with the value of the flat BSR. Moreover, it is interesting that the absorption spectra of a -Si:H on nanostructured Al BSRs with and without the 100-nm Ag coating are highly similar even if the optical properties of Al and Ag are different.

Description: The nature of charge transport mechanism in poly(3,4-ethylenedioxythiophene) nanofiber bundles has been studied as a function of temperature, magnetic field and AC electric field. High-resolution transmission electron micrographs show the formation of nanofibers with an average diameter of 14 nm. X-ray diffraction analysis depicts the enhancement of polymer chains ordering with increasing dopant concentration. Analysis of the temperature dependence of resistivity reveals a three-dimensional variable range hopping electrical conduction mechanism in the synthesized nanofibers system. A large positive magnetoresistance has been observed at low temperature, which shows a decreasing trend with increasing temperature as well as dopant concentration. The high value of positive magnetoresistance at low temperature has been explained by the wave function shrinkage model. The decrease in frequency exponent s with increasing temperature suggests that the AC conduction takes place through correlated barrier hopping mechanism.

Description: The Roman invasion introduces new alloys and metallurgical practices in Iberian Peninsula. The southwestern end of this region has many evidences of connections with the Roman World, but there are no studies about the manufacture and use of copper-based artefacts during this period. Therefore, a set of about 20 ornaments, tools and small attachments recovered at the Roman sites of Monte Molião and Cidade das Rosas was studied by an analytical approach combining micro-EDXRF, optical microscopy, SEM–EDS and Vickers microhardness testing. The artefact composition shows a good correlation with function, namely pure copper for nails and rivets, low-tin bronze (2–6 wt% Sn) for basic tools, high-tin bronze (14 wt% Sn) for fibulae and high-lead bronze (19 wt% Pb) for a decorated jug handle. The manufacture also depends on function because most artefacts were subjected to thermomechanical processing, except the ornaments that would not benefit from post-casting work. Brass and gunmetal were only present in the site with a later chronology. A metallurgy visibly ruled by economical, aesthetical and technological concerns reinforces the evidences about the total integration of Southwestern Iberian Peninsula in the Roman World, but further studies will be essential to determine the evolution of copper-based alloys in Lusitania under Roman influence.

Description: Rapid thermal annealing effects on the electrical, structural and surface morphological properties of a fabricated Ti/p-GaN Schottky diode (SD) have been investigated. The AFM results showed that the surface morphology of the Ti/p-GaN SD is reasonably smooth at different annealing temperatures. The estimated Schottky barrier height (SBH) of the as-deposited and 200 °C annealed Ti/p-GaN SDs is found to be 0.88 eV ( I – V )/1.02 eV ( C – V ) and 0.91 eV ( I – V )/1.11 eV ( C – V ). Results showed that the SBH increases to 0.98 eV ( I – V )/1.26 eV ( C – V ) upon annealing at 300 °C for 1 min in N 2 ambient. However, the SBH slightly decreases to 0.94 eV ( I – V )/1.17 eV ( C – V ) after annealing at 400 °C. Using Norde method and Cheung’s functions, the series resistance, SBH and ideality factor of the Ti/p-GaN SD are estimated and discussed at various annealing temperatures. Also, the difference between the SBHs calculated by I – V and C – V methods are discussed. Further, the interface state density N ss of the Ti/p-GaN SD is calculated and it is found to be decreases upon annealing at 300 °C and then slightly increases after annealing at 400 °C. Experimental electrical results are also correlated with the interfacial microstructure of the Ti/p-GaN SD. The SIMS and XRD results revealed that the increase or decrease in the SBHs of the Ti/p-GaN SD upon annealing could be attributed to the formation of Ti–N and Ga–Ti interfacial phases at the interface.

Description: Artificial intelligence models have the capacity to eliminate the need for expensive experimental investigation in various areas of manufacturing processes, including the material science. This study investigates the applicability of adaptive neuro-fuzzy inference system (ANFIS) approach for modeling the performance parameters of thermal expansion coefficient (TEC) of perovskite oxide for solid oxide fuel cell cathode. Oxides (Ln = La, Nd, Sm and M = Fe, Ni, Mn) have been prepared and characterized to study the influence of the different cations on TEC. Experimental results have shown TEC decreases favorably with substitution of Nd 3+ and Mn 3+ ions in the lattice. Structural parameters of compounds have been determined by X-ray diffraction, and field emission scanning electron microscopy has been used for the morphological study. Comparison results indicated that the ANFIS technique could be employed successfully in modeling thermal expansion coefficient of perovskite oxide for solid oxide fuel cell cathode, and considerable savings in terms of cost and time could be obtained by using ANFIS technique.

Description: The depth-to-width aspect ratio of pattern engineering by surface plasmons is limited for its field intensity exponential attenuation property. We here report a method to enhance patterns’ aspect ratio with a mask–photoresist–dielectric–metal four-layer metallic waveguide structure. The parameters, index and thickness, of the dielectric layer are discussed and analyzed to illustrate their affection to the patterns’ resolution and aspect ratio. A small thickness of dielectric with its index higher than photoresist will enhance the resolution and aspect ratio of pattern by these proposed structures. Numerical simulation results show that 40 nm half-pitch and 100 nm depth patterns could be performed by a chromium mask with period of 160 nm at the wavelength of 365 nm.

Description: The welding of transparent materials with ultrashort laser pulse at high repetition rates has attracted much attention due to its potential applications in fields such as optics, microfluidics, optofluidics and precision machinery. One demanding issue is the stable and reliable welding of different materials without the utilization of an intermediate layer or an optical contact. In this work, we maximized the size of the molten volume in order to generate a large pool of molten material which is able to fill an existing gap between the samples. To this end, we used bursts of ultrashort laser pulses with an individual pulse energy of up to \(10\,\upmu \hbox {J}\) . The laser-induced welding seams exhibit a base area with a size of up to \(450\,\upmu \hbox {m}\,\times 160\,\upmu \hbox {m}\) . Using these large modifications, we are able to overcome the requirement of an optical contact and weld even gaps with a height of about \(3\,\upmu \hbox {m}\) . Bulging of the sample surface and ejection of molten material in the gap between the two samples allow to bridge the gap and enable successful welding. We also determined the breaking strength of laser-welded fused silica samples without an optical contact by a three-point bending test. The determined value of up to 73 MPa is equivalent to 85 % of stability of the pristine bulk material.

Description: The welded joints of dissimilar materials have been widely used in automotive, ship and space industries. The joint quality is often evaluated by weld seam geometry, microstructures and mechanical properties. To obtain the desired weld seam geometry and improve the quality of welded joints, this paper proposes a process modeling and parameter optimization method to obtain the weld seam with minimum width and desired depth of penetration for laser butt welding of dissimilar materials. During the process, Taguchi experiments are conducted on the laser welding of the low carbon steel (Q235) and stainless steel (SUS301L-HT). The experimental results are used to develop the radial basis function neural network model, and the process parameters are optimized by genetic algorithm. The proposed method is validated by a confirmation experiment. Simultaneously, the microstructures and mechanical properties of the weld seam generated from optimal process parameters are further studied by optical microscopy and tensile strength test. Compared with the unoptimized weld seam, the welding defects are eliminated in the optimized weld seam and the mechanical properties are improved. The results show that the proposed method is effective and reliable for improving the quality of welded joints in practical production.

Description: Heating of conductive materials by electric current is used in many technological processes. Application of electric pulses to metallic glasses induces their fast crystallization, which is an interesting and complex phenomenon. In this work, crystallization of the Fe 83 B 17 amorphous alloy induced by pulses of electric current produced has been studied using X-ray diffraction and transmission electron microscopy. Ribbons of the alloy were directly subjected to single pulses of electric current 250 µs long formed by a capacitor discharge. As the value of \(\smallint I^{2} {\text{d}}t\) was increased from 0.33 to 2.00 A 2  s, different crystallization stages could be observed. The crystallization began through the formation of the nuclei of α-Fe. At high values of \(\smallint I^{2} {\text{d}}t\) , α-Fe and tetragonal and orthorhombic Fe 3 B and Fe 23 B 6 were detected in the crystallized ribbons with crystallites of about 50 nm. Thermal annealing of the ribbons at 600 °C for 2 min resulted in the formation of α-Fe and tetragonal Fe 3 B. It was concluded that pulses of electric current produced by a capacitor discharge induced transformation of the Fe 83 B 17 amorphous phase into metastable crystalline products.

Description: Iron dendritic micropines are synthesized by a hydrogen reduction, where the hematite dendritic micropines prepared by a hydrothermal method are used as starting materials. The as-obtained dendritic iron exhibits enhanced coercivity and remanent magnetization at room temperature and high complex permittivity at 2–18 GHz due to the peculiar shape anisotropy and good crystallinity. The negative imaginary permeability is observed at 14.5–18.0 GHz, suggesting it has a potential as a left-handed material. The paraffin-based composites containing 30 wt% dendritic irons show large permittivity resulting from the charge polarization and the conductivity and have a minimal reflection loss (RL) of −37.4 dB at 7.4 GHz when the thickness ( d ) is 2.0 mm. The RL values less than −20 dB are obtained in the frequency range of 5.5–12.9 GHz when d increases from 0.9 to 3.0 mm.

Description: This paper reports on a study carried out on patinas covering copper-based Greek and Roman coins found in the archaeological excavation of Regio VIII.7.1-15 in Pompeii (Italy). Since in cultural heritage ancient artefacts should not be damaged, non-destructive and micro-destructive techniques have been used to identify typical and uncommon compounds and to characterize the surface morphology. The chlorine content of light green patinas and the presence of typical minerals allowed us to identify the bronze disease. Coins from the same stratigraphic unit have shown different morphologies of corrosion, probably due to different micro-environmental conditions.

Description: Li(Ni 1/3 Co 1/3 Mn 1/3 )O 2 as a cathode material for lithium batteries is synthesized by the precursor solid-phase method. Firstly, the precursor Ni 1/3 Co 1/3 Mn 1/3 (OH) 2 is prepared. And then, Li(Ni 1/3 Co 1/3 Mn 1/3 )O 2 is synthesized. In order to improve the electrochemical performance of the material, the Li(Ni 1/3 Co 1/3 Mn 1/3 )O 2 is coated with a carbon layer. Electrochemical performance shows that the as-prepared pristine Li(Ni 1/3 Co 1/3 Mn 1/3 )O 2 exhibits a high initial discharge capacity of 189.7 mAh g −1 , and the specific capacity increases to 219.6 mAh g −1 modified by carbon coating. Moreover, it exhibits excellent cycling maintaining 95.04 % of its initial discharge capacity after 100 charge–discharge cycles, which is much higher than the pristine Li(Ni 1/3 Co 1/3 Mn 1/3 )O 2 . Moreover, when cycles at 1 C, the discharge of Li(Ni 1/3 Co 1/3 Mn 1/3 )O 2 is only 132.5 mAh g −1 , it increases to 211.3 mAh g −1 due to the appropriate carbon layer. All the tests show that Li(Ni 1/3 Co 1/3 Mn 1/3 )O 2 /C has excellent electrochemical performance, which is attributed to avoid the core material direct contact with the acidic electrolyte and suppression of Mn + dissolution into electrolyte via carbon layer and greatly improve the electronic and ionic conductivities.

Description: In this paper, the vibration motions of multi-layered piezoelectric microcantilevers (MCs) are analyzed in which these MCs are able to perform both actuating and sensing of tip deflection simultaneously. With respect to the presence of piezoelectric layers, these MCs modeled in several structures such as two layers and two segments. The governing equations of motion for these MCs are obtained using Hamilton’s principle. It should be noted that the microcantilever (MC) is modeled as a continuous beam based on Euler–Bernoulli beam theory. Then, the obtained differential equation is solved by finite element method and the time response is obtained using Newmark method. In simulation of the vibrating behavior of MCs in contact mode, the flexible beam model includes attractive, adhesive and repulsive forces, as well as the interaction of the capillary fluid layers. In order to study vibrating motion of MC, the effect of air moisture and the tip–sample equilibrium distance as environmental parameters on the amplitude and current output are investigated, and also, a sensitivity analyses are conducted on the amplitude and current output of sensor in terms of the geometrical parameters of the MC layers and the results are analyzed.

Description: Hybrid solar cells (HSCs) based on pristine ZnO nanorod array (ZnO-NRA) and conjugated polymer with ordinary inverted device architecture normally perform low open-circuit voltage ( V oc ) and short-circuit current density ( J sc ). This paper compares three improved device architectures for preparation of efficient polymer/ZnO-NRA HSCs by incorporating ZnO quantum dots (ZnO-QDs) into device with different engineering. It is found that when growth of ZnO-QDs on ZnO nanorod surface to formation of homostructured ZnO core–shell array (ZnO-CSA) instead of pristine ZnO-NRA can significantly increase the device V oc , while blending ZnO-QDs into MEH-PPV between nanorods can significantly increase the device J sc . The best photovoltaic performance is realized in the architecture consisting of ZnO-CSA as well as blends of MEH-PPV and ZnO-QDs, in which the V oc and J sc can be significant enhanced simultaneously. The present study reports the architecture-related device performances in polymer/ZnO-NRA solar cells, which will help to guide the design of HSCs or related optoelectronic devices.

Description: The Faraday rotation influence factors in tellurite-based glass and fibers were studied by experiments and simulations. TeO 2 –ZnO–Na 2 O–BaO glass family was fabricated and characterized in terms of the thermal and magneto-optical properties. Two core–cladding pairs for two fibers were selected from fabricated glasses. The Verdet constants of the glasses and fibers were measured at different wavelengths using a homemade optical bench, and the Verdet constant of fiber was close to that of the bulk glass. The influence from external factors (wavelength, laser power and magnetic field) and internal factors (thermal expansion coefficient difference, refractive index and Verdet constant of core and cladding) on Faraday rotation in fibers was investigated and discussed, and the purpose of this study is to improve the Faraday rotation in tellurite fibers for MO device applications both from internal material property match and external parameter configuration in measurement.

Description: We demonstrated the synthesis of a new ternary semiconductor nanoparticle Cd 1− x In x Te, as a sensitizer for solar cell devices via a one-pot mixed precursor solution. The Cd 1− x In x Te nanoparticles (NPs) were prepared using the chemical bath deposition process and coated onto a TiO 2 photoelectrode. A tetragonal structure of Cd 1− x In x Te NPs was constituted on the TiO 2 photoelectrode with a diameter range ∼25–30 nm, and the atomic percentages of the chemical elements showed that the structure could be Cd 0.1 In 0.9 Te incorporated with the CdIn 2 Te 4 structure. When the dipping cycle increased, the energy gaps became narrower from 1.2 to 0.6 eV due to the increasing amount and the larger size of nanoparticles. The photovoltaic properties of various cycles were investigated, and the best power conversion efficiency ( η ) of 0.49 % under full 1 sun illumination (100 mW/cm 2 , AM 1.5G) was obtained for the seven-cycle-Cd 1− x In x Te NPs with a current density ( J sc ) of 2.64 mA/cm 2 , an open-circuit voltage ( V oc ) of 638 mV, and a fill factor ( FF ) of 0.29. The efficiency of this material can be further improved for higher potential solar cell devices.

Description: The chemical and physical alterations of cadmium yellow (CdS) paints in Henri Matisse’s The Joy of Life (1905–1906, The Barnes Foundation) have been recognized since 2006, when a survey by portable X-ray fluorescence identified this pigment in all altered regions of the monumental painting. This alteration is visible as fading, discoloration, chalking, flaking, and spalling of several regions of light to medium yellow paint. Since that time, synchrotron radiation-based techniques including elemental and spectroscopic imaging, as well as X-ray scattering have been employed to locate and identify the alteration products observed in this and related works by Henri Matisse. This information is necessary to formulate one or multiple mechanisms for degradation of Matisse’s paints from this period, and thus ensure proper environmental conditions for the storage and the display of his works. This paper focuses on 2D full-field X-ray Near Edge Structure imaging, 2D micro-X-ray Diffraction, X-ray Fluorescence, and Fourier Transform Infra-red imaging of the altered paint layers to address one of the long-standing questions about cadmium yellow alteration—the roles of cadmium carbonates and cadmium sulphates found in the altered paint layers. These compounds have often been assumed to be photo-oxidation products, but could also be residual starting reagents from an indirect wet process synthesis of CdS. The data presented here allow identifying and mapping the location of cadmium carbonates, cadmium chlorides, cadmium oxalates, cadmium sulphates, and cadmium sulphides in thin sections of altered cadmium yellow paints from The Joy of Life and Matisse’s Flower Piece (1906, The Barnes Foundation). Distribution of various cadmium compounds confirms that cadmium carbonates and sulphates are photo-degradation products in The Joy of Life , whereas in Flower Piece , cadmium carbonates appear to have been a [(partially) unreacted] starting reagent for the yellow paint, a role previously suggested in other altered yellow paints.

Description: In this paper, we introduce the use of the atomic force microscope (AFM) and of the pulsed laser ablation as methods for morphological diagnostic with nanoscale precision of archeological artifacts and corrosive patina removal from stone artifacts. We test our methodology on stone artifacts extracted from the Church of Sotterra (located in Calabria, South Italy). The AFM microscopy was compared with different petrographic, chemical, optical and morphological analysis methods for identifying the textural characteristics, evaluating the state of preservation and formulating some hypotheses about the provenance and composition of the impurity patina located on the artifact surfaces. We demonstrate that with the nanometric precision obtained with AFM microscopy, it is possible to distinguish the different states of preservation, much better than using conventional petrographic methods. The surface’s roughness is evaluated from very small artifact’s fragments, reducing the coring at micrometric scale with a minimal damage to the artworks. After the diagnosis, we performed restoration tests using the pulsed laser ablation (PLA) method and compared it with the more common micro-sandblasting under dry conditions. We find that the PLA is highly effective for the removal of the surficial patina, with a control of a few hundreds of nanometers in the cleaning of surface, without introducing chemical or morphological damages to the artifacts. Moreover, PLA can be easily implemented in underwater conditions; this has the great advantage that stone and pottery artifacts for marine archeological sites do not need to be removed from the site.

Description: Structural, optical and polarization properties were investigated in different batches of ZnO synthesized by sol–gel method at varying sintering temperature. The structural visualization and charge scattering density analysis on the basis of X-ray diffraction data indicate polarized nature of sample. The structure- and polarization-related parameters were determined from Raman and Fourier transformed infrared spectroscopy data. Urbach energies and band gap were calculated using UV–visible spectroscopy. We observed increase in polarization, decrease in optical activity and band gap with increasing grain size without any increase in defects. Distortion in ZnO tetrahedra resulted in nonlinear optical behaviour above band edges. The results show direct correlation between grain size, band gap, optical behaviour and polarization. Low band gap and high polarization in ZnO can be employed for the production of opto-electronic devices.

Description: Nanostructured zinc oxide material is usable in electronic device applications such as light-emitting diodes, heterojunction diode, sensors, solar cell due to its interesting electrical conductivity and optical properties. Magnesium-doped zinc oxide nanorod (NR)–nanotube (NT) films were grown by microwave-assisted chemical bath deposition to fabricate ZnO-based heterojunction diode. It is found that ZnO hexagonal nanorods turn into hexagonal nanotubes when the Mg doping ratio is increased from 1 to 10 %. The values of the optical band gap for 1 % Mg-doped ZnO NR and 10 % Mg-doped ZnO NT films are found to be 3.14 and 3.22 eV, respectively. The n-ZnO:Mg/p-Si heterojunction diodes were fabricated. The diodes exhibited a rectification behavior with ideality factor higher than unity due to the presence of surface states in the junction and series resistance. The obtained results indicate that Mg doping improves the electrical and optical properties of ZnO.

Description: LaFe 11.6 Si 1.4 alloy has been synthesized in polycrystalline form using both arc melting and spark plasma sintering (SPS). The phase formation, hysteresis loss and magnetocaloric properties of the LaFe 11.6 Si 1.4 alloys synthesized using the two different techniques are compared. The annealing time required to obtain the 1:13 phase is significantly reduced from 14 days (using the arc melting technique) to 30 min (using the SPS technique). The magnetic entropy change (Δ S M ) for the arc-melted LaFe 11.6 Si 1.4 compound, obtained for a field change of 5 − 0 T (decreasing field), was estimated to be 19.6 J kg −1  K −1 . The effective RCP at 5 T of the arc-melted LaFe 11.6 Si 1.4 compound was determined to be 360 J kg −1 which corresponds to about 88 % of that observed in Gd. A significant reduction in the hysteretic losses in the SPS LaFe 11.6 Si 1.4 compound was observed. The Δ S M , obtained for a field change of 5 − 0 T (decreasing field), for the SPS LaFe 11.6 Si 1.4 compound decreases to 7.4 J kg −1  K −1 . The T C also shifts from 186 (arc-melted) to 230 K (SPS) and shifts the order of phase transition from first to second order, respectively. The MCE of the SPS LaFe 11.6 Si 1.4 compound spreads over a larger temperature range with the RCP value at 5 T reaching 288 J kg −1 corresponding to about 70 % of that observed in Gd. At low fields, the effective RCP values of the arc-melted and spark plasma-sintered LaFe 11.6 Si 1.4 compounds are comparable, thereby clearly demonstrating the potential of SPS LaFe 11.6 Si 1.4 compounds in low-field magnetic refrigeration applications.

Description: The crystalline structure, morphology, composition, electrical transport, and optical properties of aluminum-doped zinc oxide (AZO) films are studied for applications in transparent electronics and optoelectronic devices. AZO thin films of c -axis-oriented growth and with different thickness were deposited on PET flexible plastic substrates at room temperature by rf magnetron sputtering. A larger grain size with a decreased strain ε value is observed in a thicker film, while changes in composition for films with different thicknesses are insignificant. Moreover, the resistivity of film decreases with increasing thickness, and the low-temperature electrical transport properties can be described by the scenario of quantum corrections to conductivity. With the room-temperature growth conditions, the resistivity of 4.5 × 10 −4  Ω cm, carrier concentration of 6.4 × 10 20  cm −3 , and transmittance of 80 % for the 1100-nm-thick film are obtained. In addition, the optical bandgap energy decreases with increasing film thickness, which can be attributed to the bandgap renormalization and crystallite size effects.

Description: Guanidinium cinnamate (GUCN), a single crystal, was grown by slow evaporation technique. Single-crystal X-ray diffraction study revealed that GUCN crystal belongs to monoclinic crystal system with the space group P2 1 /c. Thermal studies revealed that the GUCN is thermally stable up to 238 °C. The optical transmittance studies were carried out for the crystal, and the lower cutoff wavelength of the grown crystal was observed at 322 nm. The luminescent study showed that the GUCN crystal has high degree of luminescence. Third-order nonlinear refractive index n 2 , nonlinear absorption coefficient β and susceptibility χ (3) parameters were estimated by Z-scan technique. The four independent tensor coefficients ε 11 , ε 22 , ε 33 and ε 13 of dielectric permittivities for monoclinic GUCN were calculated. The mechanical properties of the grown crystals were studied using Vickers micro-hardness tester at different planes.

Description: In this study, a generalized inverse-pole-figure (IPF) method has been suggested to analyze domain switching in polycrystalline ferroelectrics including composition of morphotropic phase boundary (MPB). Using the generalized IPF method, saturated domain orientation textures of single-phase polycrystalline ferroelectrics with tetragonal and rhombohedral symmetry have been analytically calculated and the results have been confirmed by comparison with the results from preceding studies. In addition, saturated domain orientation textures near MPBs of different multiple-phase polycrystalline ferroelectrics have been also analytically calculated. The results show that the generalized IPF method is an efficient method to analyze not only domain switching of single-phase polycrystalline ferroelectrics but also MPB of multiple-phase polycrystalline ferroelectrics.

Description: Microfluidic devices have not yet evolved into commercial off-the-shelf products. Although highly integrated microfluidic structures, also known as lab-on-a-chip (LOC) and micrototal-analysis-system (µTAS) devices, have consistently been predicted to revolutionize biomedical assays and chemical synthesis, they have not entered the market as expected. Studies have identified a lack of standardization and integration as the main obstacles to commercial breakthrough. Soft microfluidics, the utilization of a broad spectrum of soft materials (i.e., polymers) for realization of microfluidic components, will make a significant contribution to the proclaimed growth of the LOC market. Recent advances in polymer science developing novel stimulus-active soft-matter materials may further increase the popularity and spreading of soft microfluidics. Stimulus-active polymers and composite materials change shape or exert mechanical force on surrounding fluids in response to electric, magnetic, light, thermal, or water/solvent stimuli. Specifically devised actuators based on these materials may have the potential to facilitate integration significantly and hence increase the operational advantage for the end-user while retaining cost-effectiveness and ease of fabrication. This review gives an overview of available actuation concepts that are based on functional polymers and points out promising concepts and trends that may have the potential to promote the commercial success of microfluidics.

Description: The preparation and characteristics of ZnSnLiO thin film transistors were studied in this work. The ZnSnLiO films, as the channel layers with thickness varied from 20 to 60 nm, were deposited on SiO 2 /p-type Si substrates by radio frequency magnetron sputtering. The effect of channel layer thickness on the device characteristics of ZnSnLiO TFTs has been investigated to establish optimal channel layer thickness. The transistor with 40-nm-thick ZnSnLiO film shows the best performance with a field-effect mobility of 47 cm 2 /V s, a threshold voltage of 4.9 V, and an on/off ratio of 7.2 × 10 6 .

Description: We calculated the connection probability, P C , between electrodes on the basis of the triangular lattice percolation model for investigating the effect of distance variation between electrodes and the electrode width on fabricated capacitively coupled single-electron transistors. Single-electron devices were fabricated via the dispersion of gold nanoparticles (NPs). The NPs were dispersed via the repeated dropping of an NP solution onto a chip. The experimental results were fitted to the calculated values, and the fitting parameters were compared with the occupation probability, P O , which was estimated for one drop of the NP solution. On the basis of curves of the drain current versus the drain-source voltage ( I D − V DS ) measured at 77 K, the current was suppressed at approximately 0 V.

Description: Ultrananocrystalline diamond (UNCD)/nonhydrogenated amorphous carbon (a-C) composite (UNCD/a-C) films were deposited on cemented carbide containing Co by coaxial arc plasma deposition. With decreasing substrate temperature, the hardness was enhanced accompanied by an enhancement in the sp 3 /(sp 2  + sp 3 ). Energy-dispersive X-ray and secondary ion mass spectrometry spectroscopic measurements exhibited that the diffusion of Co atoms from the substrates into the films hardly occurs. The film deposited at room temperature exhibited the maximum hardness of 51.3 GPa and Young’s modulus of 520.2 GPa, which evidently indicates that graphitization induced by Co in the WC substrates, and thermal deformation from sp 3 to sp 2 bonding are suppressed. The hard UNCD/a-C films can be deposited at a thickness of approximately 3 μm, which is an order larger than that of comparably hard a-C films. The internal compressive stress of the 51.3-GPa film is 4.5 GPa, which is evidently smaller than that of comparably hard a-C films. This is a reason for the thick deposition. The presence of a large number of grain boundaries in the film, which is a structural specific to UNCD/a-C films, might play a role in releasing the internal stress of the films.

Description: The potentials of carbon nanotubes (CNTs) as mechanical resonators for atomic-scale mass sensing are presented. To this aim, a nonlocal continuum-based model is proposed to study the dynamic behavior of bridged single-walled carbon nanotube-based mass nanosensors. The carbon nanotube (CNT) is considered as an elastic Euler–Bernoulli beam with von Kármán type geometric nonlinearity. Eringen’s nonlocal elastic field theory is utilized to model the interatomic long-range interactions within the structure of the CNT. This developed model accounts for the arbitrary position of the deposited atomic-mass. The natural frequencies and associated mode shapes are determined based on an eigenvalue problem analysis. An atom of xenon (Xe) is first considered as a specific case where the results show that the natural frequencies and mode shapes of the CNT are strongly dependent on the location of the deposited Xe and the nonlocal parameter of the CNT. It is also indicated that the first vibrational mode is the most sensitive when the mass is deposited at the middle of a single-walled carbon nanotube. However, when deposited in other locations, it is demonstrated that the second or third vibrational modes may be more sensitive. To investigate the sensitivity of bridged single-walled CNTs as mass sensors, different noble gases are considered, namely Xe, argon (Ar), and helium (He). It is shown that the sensitivity of the single-walled CNT to the Ar and He gases is much lower than the Xe gas due to the significant decrease in their masses. The derived model and performed analysis are so needed for mass sensing applications and particularly when the detected mass is randomly deposited.

Description: The conformation and dynamic of surfactant in graphite oxide (GO) was investigated by solid-state 13 C magic-angle-spinning NMR and 1 H– 13 C cross-polarization/magic-angle-spinning NMR spectra. The conformation ordering of the alkyl chains in the confined system shows strong dependence on its orientation. While the alkyl chains parallel to the GO layer in lateral monolayer arrangement are in gauche conformation in addition to a small amount of all-trans conformation, those with orientation radiating away from the GO in paraffin bilayer arrangement is in all-trans conformation in addition to some gauche conformation even though high-order diffraction peaks appears. NMR results suggest that the least mobile segment is located at the GO-surfactant interface corresponding to the N-methylene group. Further from it, the mobility of the alkyl chain increases. The terminal methyl and N-methyl carbon groups have the highest mobile. The chains in all-trans conformational state are characterized as more rigid than chains with gauche conformation; each segment of the confined alkyl chains with the lateral monolayer arrangement exhibits less mobility as compared to that with the paraffin bilayer arrangement.

Description: This study proposes an ablation enhancement approach to fabricate microgrooves in PMMA by femtosecond laser irradiation assisted with a microtorch. The influences of pulse energy and scanning speed on the groove depth and removal area of groove are investigated. It is demonstrated that the improvement of groove depth has a close relationship with the scanning speed. When the scanning speed was less than 50 µm/s, the ablated groove depth is considerably improved with various pulse energies, up to 100 %. Moreover, the removal area of groove has significant enhancements of up to 250 % in various processing parameters. It is suggested that the ablation enhancement of microgrooves fabrication is related to the status of plasma plume and substrate heating. With the assistance of the microtorch, laser-induced plasma plume is confined and its density at center region is raised, which results in the increment of the central plasma’s temperature and more energy deposited on the PMMA surface, ultimately leading to the ablation enhancement. Meanwhile, the instantaneous substrate heating also plays a crucial role on enhanced microgrooves fabrication.

Description: The Zn 1− x Cd x O ( x  = 0.5) thin film was grown on quartz by the direct current reactive magnetron sputtering and post-annealing techniques. The influence of annealing temperature ( T a ) on the structure and optical properties of Zn 1− x Cd x O thin film was investigated by using X-ray diffraction (XRD), photoluminescence and optical absorbance measurements. The XRD results indicate that the as-grown Zn 1− x Cd x O thin film is of highly (002)-preferred orientation and possessing the hexagonal wurtzite structure of pure ZnO, as the T a increases up from 300 to 600 °C, the phase segregation as cubic CdO was observed. The detailed microstructures of the Zn 1− x Cd x O thin film were investigated by transmission electron microscopy. Moreover, with the increase of T a , the optical band gap of the Zn 1− x Cd x O thin films increased from 2.08 to 3.14 eV. Correspondingly, the near-band-edge photoluminescence was tuned in a wide visible region from ~588 to 403 nm.

Description: This study aimed to investigate a new dioxime compound as a corrosion inhibitor for copper. The compound (4,6-dihydroxy benzene-1,3-dicarbaldehyde dioxime) was synthesized and characterized by nuclear magnetic resonance spectroscopy. Electrochemical impedance spectroscopy and potentiodynamic polarization measurements were used to compare the dioxime compound with benzotriazole for their effectiveness as corrosion inhibitors for copper in 0.1 M HCl solution. Fourier transform infrared (FTIR) spectroscopy and scanning electron microscopy (SEM) were used to investigate the bonding mechanisms and morphological changes of the two inhibitors on the copper surface. The electrochemical techniques showed that the new dioxime compound was more effective than benzotriazole in inhibiting copper corrosion in the acidic chloride medium. The FTIR and SEM results indicated that the dioxime compound was able to coordinate with copper ions and formed a protective film on the copper surface. It was concluded that the new dioxime compound proved effectiveness to be used as a corrosion inhibitor for the protection and conservation of copper.

Description: In this paper, we propose a novel printed antenna for 1.8 GHz band applications. The proposed antenna is made of silver nanoparticle-based radiating element and 0.04-mm thin, transparent and flexible polyethylene terephthalate (PET) substrate. The proposed antenna is designed and simulated by finite-element-method-based high-frequency structure simulator (HFSS). We obtain reflection coefficient of −23 dB, gain of 2.72 dBi and efficiency of 93.33 %. The resonance frequency of the antenna is also verified through national instrument (NI) Multisim simulation on the proposed equivalent circuit. We realize the antenna in a single process by commercial Dimatix material inkjet printer (DMP-3000) at ambient condition and characterize it by using vector network analyzer and spectrum analyzer. The measured reflection coefficient and −10 dB bandwidth are −32.2 dB and 190.5 MHz, respectively, which shows good agreement with HFSS and NI Multisim results. The proposed compact and optimum antenna printed on thin, transparent and fully bendable PET substrate becomes very attractive since it can overcome the limits of cost and size. These results suggest that the proposed antenna is well suitable for electronic devices operating over 1.8 GHz band such as Telos-B and other wearable printed devices.

Description: In the present work, the microcrystalline characteristics of KBr thin films have been investigated by evaluating the breadth of diffraction peak. The Williamson–Hall, the Size-Strain plot and the single-line Voigt methods are employed to deconvolute the finite crystallite size and microstrain contribution from the broaden X-ray profile. The texture coefficient and dislocation density have been determined along each diffraction peak. Other relevant physical parameters such as stress, Young’s modulus and energy density are also estimated using uniform stress deformation and uniform deformation energy density approximation of Williamson–Hall method.

Description: Atomic force microscopy (AFM) has been known as an innovative tool in the fields of surface topography, determination of different mechanical properties and manipulation of particles at the micro- and nanoscales. This paper has been concerned with advanced modeling and dynamic simulation of AFM micro-cantilever (MC) in the amplitude mode in the air environment. To increase the accuracy of the governing equations, modified couple stress theory appropriate in micro- and nanoscales has been utilized based on Timoshenko beam theory in the air environment near the sample surface. Also, to discretize the equations, differential quadrature method has been recommended. In modeling, geometric discontinuities due to the presence of a piezoelectric layer enclosed between two electrode layers and the change in MC cross section when connected to the MC have been considered. In addition to the effect of MC modeling on the accuracy of modeling and vibration amplitude during surface topography, understanding and modeling the environmental forces in the air environment, including van der Waals, capillary and contact forces, are important. This paper has been provided more accurate environmental forces modeling and has been investigated the vibration behavior of piezoelectric MC in the humid environment. Moreover, this paper has been examined the maximum and minimum MC amplitude in the air environment close to the surface with different kinds of topography. The results illustrate that kind of surfaces has effect on the maximum and minimum amplitude due to the decrease or increase in equilibrium MC distance.

Description: Iron gall inks (IGI) were largely used for writing until the nineteenth century. Under certain circumstances, they provoke a substantial degradation of their cellulosic support. It was shown in a previous works that combination of oxygen and iron largely impacts cellulose chain breaking occurring in acidic conditions (pH 3–4). The present study aims to study the kinetic of this degradation. It assesses the validity of Arrhenius law between 20 and 90 °C taking advantage of the fast depolymerization of IGI impregnated papers at room temperature and using two complementary tools: DP measurements and zero-span tensile strength. The first one is sensitive enough to measure degradation at its very beginning, while the second is more appropriate for advanced stage of degradation. Similar activation energies (97 ± 2 kJ mol −1 ) were found via DP and zero-span measurements, and reaction rates of IGI impregnated papers were 1–2 orders of magnitude above available data related to lignin-free acidic papers. These observations suggest a dominant hydrolytic mechanism that involves directly or indirectly oxygen and iron.

Description: The performance of N-face AlGaN-based deep ultraviolet light-emitting diodes (UV LEDs) with superlattice electron blocking layer (EBL) is investigated by using two-dimensional numerical simulation. The simulated results demonstrate that the adoption of N-face UV LED with superlattice EBL is critical to improve the device’s performance. In comparison with the Ga-face UV LEDs with superlattice and conventional EBL, the N-face device structure with superlattice EBL possesses numerous advantages. By detailedly analyzing the profiles of energy band diagrams, distribution of carrier concentration, and radiative recombination rate, the advantages of N-face UV LED with superlattice EBL are attributed to the higher barrier for electron leakage, and simultaneously reduced barrier for hole injection compared with conventional Ga-face UV LEDs.

Description: Rapid prototyping based on molten metal droplets deposition is an additive process in which parts are produced from molten materials in a single operation without the use of any mold or other tooling. Near-net shaped parts are fabricated by sequentially depositing molten droplets layer by layer. This paper presents a systematic numerical and experimental investigation of the transient transport phenomenon during the droplets impinging onto a substrate surface. The 3D models based on a volume of fluid (VOF) method were developed to investigate the deposition of molten metal droplets on a horizontally aluminum substrate surface. Based on the above research, a semiquantitative relationship between external morphology and internal microstructure was proposed, which was further certified by investigating the piled vertical columns and the three-dimensional parts. The works should be helpful for the process optimization and non-destructive detection of drop-based rapid prototyping techniques.

Description: This work reports a large controllability of domain evolution in BaTiO 3 ferroelectric nanodot by isotropic surface charge screening (SCS). The phase field simulations show that the nanodot can exhibit fruitful domain patterns and evolution paths as functions of temperature and screening factor and changing direction of these two variables. Four typical types of experimental processes have been simulated, including the cooling-down and heating-up processes under fixed SCS conditions, and the processes of increasing and decreasing SCS under fixed temperatures. During these processes, the nanodot exhibits up to 13 different kinds of domain patterns, among which some are either polar or toroidal and some are both polar and toroidal. We summarized the phase diagrams as functions of temperature and charge screening factor, and also analyzed the typical domain evolution paths.

Description: The nanoparticles of zinc oxide (ZnO) doped with various concentrations of cobalt (Co) were synthesized by chemical precipitation method in the presence of capping agent polyvinylpyrrolidone (PVP). The effect of doping concentration on structural and morphological properties has been studied by X-ray diffraction (XRD) and scanning electron microscope (SEM). Cell volume, bond length, texture coefficient, lattice constants and dislocation density are also studied. Here, we also compared the interplaner spacing and relative peak intensities from their standard values with different angles. Crystallite sizes have been calculated by Debye–Scherrer’s formula whose values are decreasing with increase in cobalt content up to 3 %. It has been seen that the growth orientation of the prepared ZnO nanorods was (101). The XRD analysis also ensures that ZnO has a hexagonal (wurtzite) crystal structure. The electroluminescence (EL) cells were prepared by placing pure and cobalt-doped ZnO nanoparticles between ITO-coated conducting glass plate and aluminium foil. Alternating voltage of various frequencies was applied, and EL brightness at different voltages was measured and corresponding current was also recorded. The voltage dependence of electroluminescence (EL) brightness of the ZnO:Co shows exponential increase. The linear voltage–current characteristic indicates ohmic nature. The EL brightness at a particular voltage is found to increase by increasing Co doping, but for higher percentage of Co the EL brightness is reduced. It is also seen that Co does not influence the threshold voltage. The brightness is also affected by increasing the frequency of AC signal.

Description: We study the sound absorption of the reinforced polyvinylpyrrolidone nanofibers with graphene oxide. It is shown that reinforced nanofibers can acquire impedance-matched surface to airborne sound at special frequencies. To obtain such surface, nanofibers were spun with polyvinylpyrrolidone polymer that was doped by graphene oxide with concentrations of 0, 6 and 12 wt%. It was found that fibers without graphene oxide were spun continuously and randomly, whereas by doping with graphene oxide, the mode of fibers is changed and some nodes form on the fibers coating. The sound absorption coefficient was measured by an impedance tube based on 105341-1 ISO standard. Measurements in the frequency range from 700 to 1600 Hz show that use of graphene oxide as a reinforcing phase increases sound absorption coefficient of the samples at a frequency ~1500 Hz up to ~40 %. Angular eigenfrequency and dissipation coefficient of the samples were obtained by impedance measurement for the prepared samples. Results show that doping the polymer with graphene oxide causes an increase in the angular eigenfrequency and the dissipation coefficient.

Description: V 2 O 5 was synthesized by four different procedures employing thermal decomposition, sol–gel, and hydrothermal methods which were subsequently introduced into dye-sensitized solar cells (DSCs) as counter electrode (CE) catalysts for the regeneration of traditional iodide/triiodide (I − /I 3 − ) redox couple. The catalytic activities of as-prepared V 2 O 5 were significantly affected by the synthetic routes as evidenced by cyclic voltammetry, electrochemical impedance spectroscopy, and Tafel polarization curve. Power conversion efficiency (PCE) of the DSCs employing V 2 O 5 CE, fabricated by thermal decomposition method, was observed to be 3.80 % by using citric acid as an additive, while the PCE of the DSCs using V 2 O 5 CE prepared by hydrothermal and thermal decomposition methods without additive, as well as by a sol–gel procedure, was determined to be 2.13, 2.08, and 2.04 %, respectively.

Description: The back-illuminated separate absorption and multiplication AlGaN avalanche photodiodes (APDs) with a p -type graded AlGaN layer have been designed to investigate the polarization engineering on the performance of the devices. The calculated results show that the APD with p-graded AlGaN layer exhibits lower avalanche breakdown voltage and increased maximum multiplication gain compared to the structure with conventional p -type AlGaN layer. The improved performance of the designed APD is numerically explained by the polarization-assisted enhancement of the ionization electric field in the multiplication region and polarization doping effect caused by the p -type graded layer.

Description: Bulk prismatic lithium sulfate monohydrate (LSMH) single crystals were grown by seed rotation with slow heating method from aqueous solution. Small FWHM obtained from high-resolution X-ray diffraction spectrum shows that the crystals grown by this method have less defects and absence of low-angle grain boundaries. The high transmittance and low reflectance nature of the grown crystal was observed using UV–Vis–NIR spectrometer. The principal refractive indices of a LSMH crystal have been measured by a prism coupling method for the wavelengths of 0.407, 0.532, 0.828, 1.064 and 1.551 µm at room temperature, and Sellmeier equations are determined from the fitting of the data point. The refractive index data confirm that LSMH crystal is negative biaxial and the optic axis lies in YZ plane with an angle (2 V y ) of 51.74° with respect to y axis at 532 nm wavelength. The thermo-optic coefficients were determined from the temperature-dependent refractive indices measured in the range of 30–125 °C for the wavelengths of 532 and 1064 nm. The surface laser damage threshold studies reveal the higher optical radiation stability against 532-nm laser. The pyroelectric coefficients and pyroelectric figure of merit were determined from the pyroelectric current measurement by the Byer and Roundy method.

Description: Thermoelectric (TE) devices that produce electric power from heat are driven by a temperature gradient ( \(\Delta T = T_{\text{hot}} - T_{\text{cold}}\) , T hot : hot side temperature, T cold : cold side temperature) with respect to the average temperature ( T ). While the resistance of TE devices changes as \(\Delta T\) and/or T change, the current–voltage ( I – V ) characteristics have consistently been shown to remain linear, which clips generated electric power ( P gen ) within the given open-circuit voltage ( V OC ) and short-circuit current ( I SC ). This P gen clipping is altered when an appropriate nonlinearity is introduced to the I – V characteristics—increasing P gen . By analogy, photovoltaic cells with a large fill factor exhibit nonlinear I – V characteristics. In this paper, the concept of a unique TE device with nonlinear I – V characteristics is proposed and experimentally demonstrated. A single TE device with nonlinear I – V characteristics is fabricated by combining indium phosphide (InP) and silicon (Si) semiconductor nanowire networks. These TE devices show P gen that is more than 25 times larger than those of comparable devices with linear I – V characteristics. The plausible causes of the nonlinear I – V characteristics are discussed. The demonstrated concept suggests that there exists a new pathway to increase P gen of TE devices made of semiconductors.

Description: A binary liquid crystalline mixture of a monotropic polar compound 4-cyanophenyl 4′- n -pentyl benzoate (CPPB) and an enantiotropic non-polar compound 4- n -hexyl phenyl 4- n ′-pentyloxy benzoate (ME5O.6) shows the presence of an induced smectic A phase in the region 0.1 ≤  x CPPB  ≤ 0.82, where x CPPB is the mole fraction of CPPB. The results of texture study, density study and refractive index measurements of the eutectic mixture along with those of the pure samples are reported in this paper. The density values of the eutectic mixture are found to be much higher than that of the pure samples. The determination of order parameters of the pure samples and eutectic mixture has been carried out. In order to determine the order parameters of the samples, we have used different methods, Vuks’, Neugebauer’s, modified Vuks’ and direct extrapolation method. The results of order parameters obtained from the different approaches are compared and analysed in detail.

Description: The new mixed compound Tl 1.89 K 0.11 (SO 4 ) 0.9 (SeO 4 ) 0.1 Te(OH) 6 which is crystallized in the monoclinic system with space group P 2 1 / c was analyzed at room temperature using X-ray diffractometer data. The unit cell parameters are a  = 12.3308(7), b  = 7.2011(4), c  = 12.0298(8) Å, β  = 110.755(4)°, V  = 998.87(11) Å 3 and Z  = 4. The final refinement led to R  = 0.035 and Rw  = 0.038. The main feature of these atomic arrangements is the coexistence of three and different anions (SO 4 2− , SeO 4 2− and TeO 6 6− groups) in the unit cell, connected by hydrogen bonds (O–H···O) which make the building of the crystal. The Tl + and K + cations, occupying the same positions, are located between these polyhedral. The crystals of Tl 1.89 K 0.11 (SO 4 ) 0.9 (SeO 4 ) 0.1 Te(OH) 6 underwent three endothermic peaks at 377, 466 and 472 K. These transitions were detected by DSC and analyzed by dielectric measurements using the impedance and modulus spectroscopy techniques. The IR and Raman spectra recorded at room temperature in the frequency ranges (50–1200) and (400–4000) cm −1 , respectively, have confirmed the presence of TeO 6 6− , SO 4 2− and SeO 4 2− groups in the crystal.

Description: We have studied the structural, electronic and half-metallic ferromagnetic properties of Ga 1− x Cr x As compounds at dopant concentrations x  = 0.25, 0.125 and 0.0625. First principle calculations based on density functional theories as implemented in SIESTA code using LDA +  U (local density approximation +  U ) as exchange correlation potential have been used to study the properties of these compounds. Here, U is the Hubbard’s parameter. The calculated results predict that Cr-doped GaAs diluted magnetic semiconductors exhibit half-metallic properties at different concentrations, in which Cr atoms form deep levels in forbidden energy gap. The results also predict that with increase of fraction of Cr atoms, half-metallic energy band gap of Ga 1− x Cr x As decreases. Total magnetic moment of these compounds is due to Cr states, and also p–d hybridization between Ga-p and Cr-d induces small magnetic moment on nonmagnetic atoms (Ga and As) for all concentrations.

Description: Anodizing of aluminum is used for producing porous insulating films suitable for different applications in electronics and microelectronics. Porous-type aluminum films are most simply realized by galvanostatic anodizing in aqueous acidic solutions. The improvement in application of anodizing technique is associated with a substantial reduction of the anodizing voltage at appropriate current densities as well as to the possibility to carry out the synthesis process at room temperature in order to obtain a self-planarizing dielectric material incorporated in array of super-narrow metal lines. In this work, the anodizing of aluminum to obtain porous oxide was carried out, at room temperature, on three different substrates (glass, stainless steel and aluminum), using an oxalic acid-based electrolyte with the addition of a relatively low amount of 0.4 % of HF. Different surface morphologies, from nearly spherical to larger porous nanostructures with smooth edges, were observed by means of scanning electron microscopy. These evidences are explained by considering the formation, transport and adsorption of the fluorine species which react with the Al 3+ ions. The behavior is also influenced by the nature of the original substrate.

Description: Bandgap-tailored NiO nanospheres were successfully synthesized by facile precipitation method for the first time and characterized by XRD, EDX, SEM, TEM, FTIR, UV and PL. Interestingly, the modification of the band gap was observed using UV–Vis (DRS) spectroscopy, and the observed band gap is 3.31 eV. The morphology of the materials was analysed by SEM and TEM which show the sphere like structures of NiO with the particle size of ~20 nm. The efficiency of the materials was examined by the degradation of crystal violet dye under UV light illumination. The complete degradation was achieved within 60 min, and the mechanism of the degradation were also been proposed. In addition, the degradation of rhodamine B (RhB) and methylene blue dye solution was also carried out to extend the practical applications of NiO nanospheres. The involvement of reactive oxidative species (ROS) was found out by trapping experiment, and the ROS is superoxide radical anion.

Description: This study focused on the characterization and properties of transparent and conductive indium tin oxide (ITO) thin films deposited in argon atmosphere. ITO thin films were coated onto glass substrates by radio frequency (RF) magnetron sputtering technique at 75 and 100 W RF powers. Structural characteristics of producing films were investigated through X-ray diffraction analysis. UV–Vis spectrophotometer and interferometer were used to determine transmittance, absorbance and reflectance values of samples. The surface morphology of the films was characterized by atomic force microscope. The calculated band gaps were 3.8 and 4.1 eV for the films at 75 and 100 W, respectively. The effect of RF power on crystallinity of prepared films was explored using mentioned analysis methods. The high RF power caused higher poly crystallinity in the produced samples. The thickness and refractive index values for all samples increased respect to an increment of RF power and were calculated as 20, 50 nm and 1.71, 1.86 for samples at 75 and 100 W, respectively. Finally, the estimated grain sizes for all prepared films decreased with increasing of 2 θ degrees, and the number of crystallite per unit volume was calculated. It was found that nearly all properties including sheet resistance and resistivity depend on the RF power.

Description: Ca 3 NbGa 3 Si 2 O 14 (CNGS), a five-component crystal of lanthanum-gallium silicate group, was grown by the Czochralski method. The parameters of the elementary unit cell of the crystal were measured by powder diffraction. The independent piezoelectric strain coefficients \(d{}_{11}\) and \(d_{14}\) were determined by the triple-axis X-ray diffraction in the Bragg and Laue geometries. Excitation and propagation of surface acoustic waves (SAW) were studied by high-resolution X-ray diffraction at BESSY II synchrotron radiation source. The velocity of SAW propagation and power flow angles in the \(Y\) -, \(X\) - and \(yxl/{+}36^\circ\) -cuts of the CNGS crystal were determined from the analysis of the diffraction spectra. The CNGS crystal was found practically isotropic by its acoustic properties.

Description: We describe the application of electron spin resonance (ESR) and magnetic susceptibility methods to study the magnetic properties and valence state of transition metal ions in Li 2 Mn 2 (MoO4) 3 polyanion compound previously studied for its cathode-active properties in lithium containing batteries. ESR measurements of Li 2 Mn 2 (MoO 4 ) 3 have shown the presence of Mn 2+ ions in the octahedral environment of oxygen ions. It is found that the part of manganese ions occupy the anti-site positions in lithium sublattice. The absence of the ESR signal from molybdenum ions indicates that they are non-magnetic and adopt the 6 + valence state. Considerable overlapping between 3d orbitals of transition metal and 2p oxygen orbitals has been experimentally established. This leads to the indirect exchange interaction and antiferromagnetic ordering of manganese ions at 1.4 K.

Description: The absorbing composite filled with the flaky carbonyl iron particles (CIPs) were prepared using a three-dimensional (3D) forming process, in which the forming powder was fabricated using a milling process. The surface morphology was characterized by the scanning electron microscopy, the static magnetic property was evaluated on a vibrating sample magnetometer, and X-ray diffraction (XRD) patterns were done to analyze the particle crystal grain structure. The complex permittivity and permeability were measured using a vector network analyzer in the frequency range of 4–18 GHz. With the variable thickness was set, the reflection loss (RL) was simulated to analyze the absorbing property of the composite. The results showed that the forming powder was uniformly dispersed in the absorber, and the saturation magnetization and the grain structure of the CIPs in the forming powder nearly did not change in the milling process. With the same volume content CIPs added, the average permittivity and the imaginary permeability of the samples added the powder was smaller than the directly mixing sample due to the aggregation effect. The RL results showed that the absorbing composites using the 3D forming process with thickness 6 or 8 mm had an better absorbing property (minimum RL −13.58 and −21.85 dB) in 4–18 GHz.

Description: In this work, we report for the first time, the nonlinear optical absorption properties of vanadium pentoxide (V 2 O 5 ) nanoparticles in the femtosecond excitation regime. V 2 O 5 nanoparticles were synthesized through solution combustion technique. The as-synthesized samples were further characterized using XRD, FESEM, EDAX, TEM and UV–visible spectroscopy. X-ray diffraction results revealed the crystalline nature of the nanoparticles. Electron microscopy studies showed the size of the nanoparticles to be ~200 nm. Open-aperture z-scan technique was employed to study the nonlinear optical absorption behavior of the synthesized samples using a 100-fs laser pulses at 800 nm from a regeneratively amplified Ti: sapphire laser. The mechanism of nonlinear absorption was found to be a three-photon absorption process which was explained using the density of states of V 2 O 5 obtained using density functional theory. These nanoparticles exhibit strong intensity-dependent nonlinear optical absorption and hence could be considered for optical-power-limiting applications.

Description: In this paper, a tunable broadband unidirectional acoustic transmission (UAT) device composed of a bended tube and a superlattice with square columns is proposed and numerically investigated by using finite element method. The UAT is realized in the proposed UAT device within two wide frequency ranges. And the effectiveness of the UAT device is demonstrated by analyzing the sound pressure distributions when the acoustic waves are incident from different directions. The unidirectional band gaps can be effectively tuned by mechanically rotating the square columns, which is a highlight of this paper. Besides, a bidirectional acoustic isolation (BAI) device is obtained by placing two superlattices in the bended tube, in which the acoustic waves cannot propagate along any directions. The physical mechanisms of the proposed UAT device and BAI device are simply discussed. The proposed models show potential applications in some areas, such as unidirectional sonic barrier or noise insulation.

Description: Chalcogenide Se 50 Te 20 S 30 thin film of different thickness was deposited using thermal evaporation technique. The thermogram of the chalcogenide bulk Se 50 Te 20 S 30 was obtained using a differential scanning calorimetry (DSC) with heating rate of 7.5 K/min. The glass transition temperature T g , crystallization temperature T c and peak crystallization temperature T p were identified. The X-ray diffraction (XRD) examination indicates the amorphous nature of the as-deposited film and polycrystalline structure of the thermal annealed ones. The dark electrical resistivity ( ρ ) measurements were taken in temperature range (300–500 K) and thickness range (200–450 nm). Analysis of the electrical resistivity results revealed two types of conduction mechanisms: conduction due to extended states in the temperature range ( T  〉  T c ) and variable range hopping in the temperature range ( T  〈  T c ). The effect of the heat treatment and thickness on the density of localized states at the Fermi level N ( E F ) and hopping parameters were studied.

Description: Thermal evaporation technique was used to deposit 263 nm of TiO 2 films on a quartz substrate. XRD of powder TiO 2 reveals anatase phase characterized by nanostructure with crystallite size within a range of 4–10 nm. The increase in annealing temperature (400–800 °C) increases the crystallite size up to 43.1 nm. SEM micrograph shows grains of annealed TiO 2 films within nanoscale. Optical gap, refractive index, dielectric constants, porosity, ratio of carrier concentration to the effective mass, dispersion, and oscillation energy were determined as well as optical conductivity and energy loss function. All parameters are affected by annealing. Current theoretical ideas were used to discuss the obtained results.

Description: An intermediate-valence compound, Yb 2 MgSi 2 , has been prepared using a spark plasma sintering method. The magnetic susceptibility and thermoelectric properties of Yb 2 MgSi 2 are measured in the temperature range from 5 to 300 K. From the magnetic susceptibility results, Yb valence of the Yb 2 MgSi 2 is evaluated. As compared with YbAl 3 , which is one of the promising thermoelectric materials that can be used at low temperatures, Yb 2 MgSi 2 exhibits a lower absolute value of Seebeck coefficient, higher electrical resistivity, and lower thermal conductivity over the measured temperature range. A maximum dimensionless figure of merit, ZT , of 0.0018 is achieved at around 200 K.

Description: Although the role of ion bombardment on electrical conductivity and optical reflectivity of transition metal nitrides films was reported previously, the results were controversial and the mechanism was not yet well explored. Here, we show that proper ion bombardment, induced by applying the negative bias voltage ( V b ), significantly improves the electrical conductivity and optical reflectivity in rocksalt hafnium nitride films regardless of level of stoichiometry (i.e., in both near-stoichiometric HfN 1.04 and over-stoichiometric HfN 1.17 films). The observed improvement arises from the increase in the concentration of free electrons and the relaxation time as a result of reduction in nitrogen and hafnium vacancies in the films. Furthermore, HfN 1.17 films have always much lower electrical conductivity and infrared reflectance than HfN 1.04 films for a given V b , owing to more hafnium vacancies because of larger composition deviation from HfN exact stoichiometry (N:Hf = 1:1). These new insights are supported by good agreement between experimental results and theoretical calculations.

Description: Thin films based on polymer poly(isobutyl methacrylate) (PIBMA), doped with carbon black particles deposited on steel plate substrates are proposed as dirt reference standards for cleanliness accreditation methods, particularly for instruments based on laser ablation. The films were made with the spin-coating method, obtaining layers with thickness between 4 and 17 μm. Carbon black particles with sizes smaller than 100 nm and concentrations between 1 and 27.6 mgr/cm 3 were used. Characterization of the films was made by using absorbance measurements and laser ablation-induced photoacoustic.

Description: The analysis of the electrical properties of Au/n-Ge 15 In 5 Se 80 /p-Si/Al heterojunction is examined. I – V characteristics show diode-like behavior. The series resistance is found to decrease with increasing the temperature in three different methods of calculations. The thermionic emission mechanism is found to be the operating mechanism at relatively low forward voltages ( V  〈 0.25). While, at relatively high forward voltage, the space charge limited conduction is the operating mechanism. The rectification ratio, ideality factor, barrier height, total trap concentration and built-in voltage are determined. The capacitance–voltage ( C – V ) characteristics of Au/n-Ge 15 In 5 Se 80 /p-Si/Al heterojunction are also investigated. The I – V curve of the Au/n-Ge 15 In 5 Se 80 /p-Si/Al heterojunction in the dark and after illumination is clarified.

Description: The oxygen-deficient strontium iron oxide SrFeO 3− δ (SFO) exhibits richness in the phase diagram over a broad range of temperatures and for other external parameters. Room-temperature X-ray diffraction and Raman spectrum reveals that the structure of synthesized SFO system consists of two mixed phases, i.e., major orthorhombic and minor tetragonal phases. The low-temperature Raman and vibrating sample magnetometer measurements indicated a structural transition below 253 K. The magnetic property of the synthesized SFO for various external magnetic field (up to 5 T) reveals possible variation in oxygen stoichiometry. Also, the application of external H increases Neel transition temperature ( T N ), suppresses the hysteresis width ( W H ), and thus weakens the first-order nature of the transition. Our analysis revealed the vanishing of hysteresis and the first-order antiferromagnetic transition becomes a crossover above a critical magnetic field H CR  ≈ 5 T. Possible switching of magnetic ordering and oxidation state observed in same system enhances interest in related compounds which may be used in magnetic sensors and other magnetic switching devices.

Description: Coherent thermal phonons (CTPs) play an important role in thermal transport in superlattice (SL) structures. To have a profound understanding of CTP transport in SL, direct measurement of CTP properties is necessary. In this study, coherent phonon spectroscopy has been utilized to generate and detect CTP in Bi 2 Te 3 /Sb 2 Te 3 SL. Phonon lifetimes have been extracted from experimental data, with which mode-wise thermal conductivities have been calculated. Comparing with bulk Bi 2 Te 3 , the estimated mode-wise thermal conductivity of longitudinal acoustic phonons shifts to higher frequencies, due to constructive coherent phonon interference. Our results suggest that it is possible to use SL structure to manipulate coherent phonon propagation and to tailor thermal conductivity.

Description: Despite valuable electrical characteristics, the use of pure aluminum in different applications has been limited due to its low strength. Non-equal channel angular pressing (NECAP) is a recently proposed severe plastic deformation process with greater induced plastic strain and, consequently, better grain refinement in the product, compared with the well-known equal channel angular pressing technique. This research is concerned with the effects of the process temperature and ram velocity on the mechanical, workability and electrical properties of AA1060 aluminum alloy. Increasing the process temperature can concurrently increase the workability, ductility and electrical conductivity, while it has a reverse influence on the strength of the NECAPed specimen, although the strengths of all the products are higher than the as-received alloy. The influence of the ram speed on the mechanical properties of the processed samples is lower than the process temperature. Finally, a compromised process condition is introduced in order to attain a good combination of workability and strength with well-preserved electrical conductivity for electrical applications of components made of pure aluminum.

Description: In the present article, effect of charge compensator ions (R +  = Li + , Na + and K + ) on dysprosium-doped di-calcium magnesium di-silicate (Ca 2 MgSi 2 O 7 :Dy 3+ ) phosphors were investigated. The Ca 2 MgSi 2 O 7 :Dy 3+ and Ca 2 MgSi 2 O 7 :Dy 3+ , R + phosphors, were prepared by solid-state reaction method. The crystal structures of sintered phosphors were an akermanite-type structure which belongs to the tetragonal crystallography. The peaks of mechanoluminescence (ML) intensity were increased linearly with increasing impact velocity of the moving piston. Thus, present investigation indicates that the piezoelectricity was responsible to produce ML in prepared phosphors. The time of the peak ML intensity and the decay rate did not change significantly with respect to increasing impact velocity. Addition of charge compensator ions enhances the luminescence intensity of prepared Ca 2 MgSi 2 O 7 :Dy 3+ phosphors, because they neutralize the charge generated by Dy 3+ substitution for Ca 2+ ions. The role of Li + ions among all charge compensator ions (Na + or K + ) used was found to be most effective for enhanced Dy 3+ ion emission. These ML materials can be used in the devices such as stress sensor, fracture sensor, impact sensor, damage sensors, safety management monitoring system and fuse system for army warheads.

Description: Photoelectron spectroscopy has been employed to analyze the content and chemical states of the elements on the surface of AlN films with different thickness, which are synthesized by metalorganic chemical vapor deposition on the n-type SiC substrates under low pressure. It is found that, besides the carbon and gallium on the AlN surface, the atom percentage of surface oxygen increases from 4.9 to 8.4, and the electron affinity also increases from 0.36 to 0.97 eV, when the thickness of AlN films increase from 50 to 400 nm. Furthermore, accompanying with the high-resolution XPS spectra of the O 1s, it is speculated that surface oxygen may be the major influence on the electron affinity, where the surface oxygen changes the surface chemical states through replacing N to form Al–O bond and Ga–O bond, although there are also a few of Ga and C contaminations in the chemical sate of Ga–O and C–C, respectively.

Description: Yttria-stabilized zirconia (YSZ) consists of zirconia and yttria and oxygen vacancies appear in accordance with the ratio of yttria. The oxygen vacancy would sometimes give annoyance, but it would be beneficial on other occasions, depending on its applications. Photoluminescence (PL) due to oxygen vacancies induced by photons with energies around 5.5 eV exhibits two decay time constants. As a possible reason for this, an oxygen vacancy changes its charging state from neutral to positive monovalent by losing an electron when YSZ is irradiated by ultraviolet photons. The PL decays either in a ms range or in a ns range, depending on whether the oxygen vacancies are neutral or positive monovalent.

Description: We present here a small-angle neutron scattering investigation on typical limestone widely used in the Baroque architecture of Modica (eastern Sicily). The aim was to correlate the salt weathering and, after that, consolidating (using nanolime as consolidant product) behaviour of the mesoscopic features observed in the experiment, with particular regard to the pore structure, which determines the interaction between surface and environmental/consolidating agents. Experimental results have been interpreted in terms of a fractal model that revealed successful in characterizing physical properties induced by treatment, in order to predict the behaviour of consolidated stone against salt weathering.

Description: Laser-induced periodic surface structures (LIPSS) were processed on the TiO 2 bulk surface under the irradiation of 248 nm unpolarized KrF excimer laser pulses in air. Spatial LIPSS periods ranging from 2 to 3.5 μm are ascribed to the capillary wave. These microstructures were analyzed at different laser pulse numbers with the laser energy from 192 to 164 mJ. The scanning electron microscopy results indicated eventually stripes that have been disrupted as the increase in the laser pulse numbers, which is reasonably explained by the energy accumulating effect. In addition, investigations were concentrated on the surface modifications at pre-focal plane, focal plane and post-focal plane in the same defocusing amount. Compared with condition at pre-focal plane, in addition to the plasma produced at target, the air was also breakdown for the situation of post-focal plane. So it was reasonable that stripes appeared at pre-focal plane but not at post-focal plane.

Description: The electrical characteristics of atomic-layer-deposited Al 2 O 3 /TiO 2 /Al 2 O 3 on (NH 4 ) 2 S-treated InP MOS capacitor and related MOSFET were studied. The electrical characteristics were improved from the reduction of native oxides and sulfur passivation on InP by (NH 4 ) 2 S treatment. The high bandgap Al 2 O 3 on TiO 2 can reduce the thermionic emission, and the Al 2 O 3 under TiO 2 improves the interface-state density by self-cleaning. The high dielectric constant TiO 2 is used to lower the equivalent oxide thickness. The leakage currents can reach 2.3 × 10 −8 and 2.2 × 10 −7  A/cm 2 at ±2 MV/cm, respectively. The lowest interface-state density is 4.6 × 10 11  cm −2  eV −1 with a low-frequency dispersion of 15 %. The fabricated enhancement-mode n-channel sulfur-treated InP MOSFET exhibits good electrical characteristics with a maximum transconductance of 146 mS/mm and effective mobility of 1760 cm 2 /V s. The subthreshold swing and threshold voltage are 117 mV/decade and 0.44 V, respectively.