ALBERT

Description: 〈p〉Publication date: September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Vacuum, Volume 167〈/p〉 〈p〉Author(s): Bo Yong, Tian Yang, Bin Yang, Bao-Qiang Xu, Da-Chun Liu, Wei Zhang〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Lead acid batteries are often used, and they produce an abundant amount of lead acid battery waste, which is a source of lead carbonate. Lead oxide was manufactured via thermal decomposition in a vacuum from recycled lead carbonate that was extracted from lead acid battery waste. The decomposed products were characterized by X-ray diffraction and decomposition rate. The impact of the decomposition conditions, including temperature, preservation time, particle size and system pressure, on the lead carbonate decomposition rate were evaluated. The results show that the newly developed lead carbonate vacuum decomposition technique does a good job, and that the decomposition conditions strongly affect the lead carbonate decomposition rate and phase compositions. For instance, at a temperature range of 310–580 °C, a pressure ranging from 10 to 60 Pa, and a preservation time of 30 min, decomposition rates reached as high as 95.77%. At the temperature of 310 °C, when the preservation time increased from 30 min to 180 min, the decomposition rate increased from 29.62% to 78.40%. In terms of the effect of particle size, the mixed particles (≤20 mesh and ≤400mesh) worked best. Furthermore, the lower pressure can explain the lower temperature obtained, and the vacuum system is suited for decomposition, coinciding with a higher decomposition rate.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Vacuum, Volume 167〈/p〉 〈p〉Author(s): Wenbin Zuo, Vasiliy O. Pelenovich, Alexander B. Tolstogouzov, Alexei E. Ieshkin, Xiaomei Zeng, Zhenguo Wang, Gennady Gololobov, Dmitriy Suvorov, Chuansheng Liu, Dejun Fu, Donghong Hu〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉We have developed a solid electrolyte ion source (SEIS) with CsAg〈sub〉4〈/sub〉Br〈sub〉2.68〈/sub〉I〈sub〉2.32〈/sub〉 film deposited on a silver tip. In the paper, Ag〈sup〉+〈/sup〉 ion emission was significantly enhanced and the ion current of 1.6 μA was obtained at 168 °C temperature and 20 kV accelerating voltage. 〈em〉I-T〈/em〉 and 〈em〉I-U〈/em〉 characteristics were well described by the field evaporation (FEV) model, and the surface potential barrier was estimated to be 0.19 eV. Experimental investigations of the Ag〈sup〉+〈/sup〉 ion emission mechanisms revealed that the solid electrolyte film plays an important role of ion-transport system, and the emitted Ag〈sup〉+〈/sup〉 ions were compensated by the ions diffusing from the silver reservoir (Ag-tip). The developed SEIS was exploited for the synthesis of Ag nanoparticles on Si surface. The average size of these nanoparticles was estimated 15.5 ± 0.3 nm, and the projected range 〈em〉R〈/em〉〈sub〉〈em〉p〈/em〉〈/sub〉 of the low-energy high-dose Ag〈sup〉+〈/sup〉 ions implanted Si sample was found to be less than 5 nm using TOF-SIMS depth profiling. The future application of SEISs in ion propulsion systems of miniature spacecraft with limited on-board payloads was discussed, and the thrust was estimated within μN range.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Vacuum, Volume 167〈/p〉 〈p〉Author(s): Junqiang Xu, Jun Zhu, Jikang Fan, Qi Zhou, Yong Peng, Shun Guo〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Electron beam freeform fabrication (EBF〈sup〉3〈/sup〉) has drawn increasing attention over the past decade due to its potential for time and cost savings. The microstructure and mechanical properties of EBF〈sup〉3〈/sup〉- fabricated Ti–6Al–4V block have been investigated and discussed in this work. The microstructure of the as-fabricated block was found to be dominated by columnar grains and equiaxed grains. The phase constitutions were identified by X-ray diffraction and transmission electron microscopy. The results reveal that the as-fabricated Ti–6Al–4V samples consist of lamellar structure, basketweave structure and Widmanstätten structure. The graded Ti–6Al–4V microstructure was observed which mainly arise from the complex thermal cycles. The average width of lamellar α phase and element content of Al are decreased with the increasing of the building height. Graded mechanical properties of Ti–6Al–4V with microhardness and tensile strength were found. The microhardness and ultimate tensile strength increase while decreasing elongation as the increasing of build height. This work provides a better understanding of microstructural evolution during the EBF〈sup〉3〈/sup〉 process, which will be conducive process control, improvement, and optimization.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Vacuum, Volume 167〈/p〉 〈p〉Author(s): Shaohua Zhang, Lifeng Hou, Huayun Du, Huan Wei, Baosheng Liu, Yinghui Wei〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The electrochemical study on the effect of HCO〈sub〉3〈/sub〉〈sup〉−〈/sup〉 on the corrosion behaviour of carbon steel in CO〈sub〉2〈/sub〉 saturated NaCl solutions was investigated through mathematical calculation of impedance plots and potentiodynamic polarization. Results reveal that a competitive adsorption between HCO〈sub〉3〈/sub〉〈sup〉−〈/sup〉/Cl〈sup〉−〈/sup〉 exists, and HCO〈sub〉3〈/sub〉〈sup〉−〈/sup〉 is able to reduce and/or replace the adsorption of Cl〈sup〉−〈/sup〉 on carbon steel surfaces with the elevation of HCO〈sub〉3〈/sub〉〈sup〉−〈/sup〉 concentration. In addition, at the certain condition (CO〈sub〉2〈/sub〉-saturated solution containing 0.1 M Cl〈sup〉−〈/sup〉), carbon steel tends to passivate when HCO〈sub〉3〈/sub〉〈sup〉−〈/sup〉 concentration reaches 0.5 M. However, pitting can be triggered in 0.2 M HCO〈sub〉3〈/sub〉〈sup〉−〈/sup〉 concentration. The findings of this work spot light on the understanding of many parameters related to this process, which is of great significance to prevent the underlying corrosion failure and prolong the lifespan of carbon steel pipelines in the service environment.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Vacuum, Volume 167〈/p〉 〈p〉Author(s): Y. Pan, C. Jing, Y.P. Wu〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Tungsten disilicide (WSi〈sub〉2〈/sub〉) is an attractive advanced functional material, which is regarded as the potential thermoelectric devices, energy storage system and aerospace etc. However, the correlation between structure and the related performances of WSi〈sub〉2〈/sub〉 is not well understood. To solve those problems, we apply first-principles calculations to study crystal structure, electronic properties, elastic properties and electronic structure of four possible WSi〈sub〉2〈/sub〉. We demonstrate the WSi〈sub〉2〈/sub〉 with C54 TiS〈sub〉2〈/sub〉-type orthorhombic structure (〈em〉Fddd〈/em〉, No.70) is a dynamically stable. These results show that MoSi〈sub〉2〈/sub〉-type C11〈sub〉b〈/sub〉 tetragonal structure is more thermodynamically stable than that of the other structures. Importantly, MoSi〈sub〉2〈/sub〉-type C11〈sub〉b〈/sub〉, TiSi〈sub〉2〈/sub〉-type C49 and HfSi〈sub〉2〈/sub〉-type C54 structures show electronic properties because of band overlap between the valence band and the conduction band near the Fermi level. However, NbSi〈sub〉2〈/sub〉-type C40 structure shows a semiconductor property with a band gap of 0.049 eV. We further find that MoSi〈sub〉2〈/sub〉-type C11〈sub〉b〈/sub〉 structure shows the strong shear deformation resistance and high elastic stiffness due to the pyramidal bonding state. WSi〈sub〉2〈/sub〉 with TiSi〈sub〉2〈/sub〉-type C54 structure exhibits better ductile in comparison to the other structures.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Vacuum, Volume 167〈/p〉 〈p〉Author(s): Fan Li, Xin Zhang, Jiuxing Zhang〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Mayenite-derived electride [Ca〈sub〉24〈/sub〉Al〈sub〉28〈/sub〉O〈sub〉64〈/sub〉]〈sup〉4+〈/sup〉(4e〈sup〉−〈/sup〉) has been successfully synthesized via an aluminothermic reaction of Ca〈sub〉3〈/sub〉Al〈sub〉2〈/sub〉O〈sub〉6〈/sub〉 (C3A), Al〈sub〉2〈/sub〉O〈sub〉3〈/sub〉, and Al powders at 1070 °C for 10 min using spark plasma sintering (SPS) process in a vacuum. The C3A precursors were directly derived from high temperature calcinating in an ambient atmosphere. The as-synthesized C12A7:e〈sup〉−〈/sup〉 exhibits an electron density of ∼2.3 × 10〈sup〉21〈/sup〉cm〈sup〉−3〈/sup〉, a spin concentrations of ∼6.7 × 10〈sup〉19〈/sup〉cm〈sup〉−3〈/sup〉 and optical absorption bands of 0.5eV and 2.48ev at room temperature. Electronic structure was also evaluated by electron paramagnetic resonance (EPR). The appearance of Dysonian characteristic, a typical feature of good electronic conductors, strongly suggested the formation of conductive mayenite structure. This developed and efficient route not only proposes an modified precursor for the synthesis of high-quality C12A7:e〈sup〉−〈/sup〉 but also provide more comprehensive insights into mayenite research.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Vacuum, Volume 167〈/p〉 〈p〉Author(s): Cheng Lu, Yingying Fu, Junhong Jia, Gewen Yi, Erqing Xie, Hongjian Guo〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Nanocomposite Mo–V–Ag–O films were deposited on Inconel 718 by pulsed laser deposition (PLD) technique with self-prepared composite target. The effects of substrate temperatures on the growth characteristics, mechanical and tribological properties of nanocomposite films were investigated. The phase transformation, micro-structure and element content of target and films were investigated by XRD and FESEM equipped with EDS, respectively. The chemical and phase changes in wear tracks were measured by Raman spectrometer. The results showed that the high ingredient uniformity of target and onset of crystallization of film occurred at substrate temperature of 400 °C. Higher substrate temperature could reduce defects and improve the crystallization and micro-hardness of the composite films. Furthermore, the composite film showed the lowest friction coefficient about 0.24 at 500 °C which could be ascribed to the synergistic lubricating effect of vanadium oxide (V〈sub〉n〈/sub〉O〈sub〉2n±1〈/sub〉), molybdenum oxide (MoO〈sub〉3〈/sub〉) and silver vanadate (AgVO〈sub〉3〈/sub〉) and the formation of lubrication glaze on the worn surfaces.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Vacuum, Volume 167〈/p〉 〈p〉Author(s): H. Pai, Sajad Ali, S. Rajbanshi, Prithwijita Ray, Subinit Roy, A. Goswami〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Technical details of the preparation of an ingot of 〈sup〉112〈/sup〉Sn from metallic powder is discussed in details. The prepared ingot is used to fabricate the self-supporting and 〈sup〉208〈/sup〉Pb-backed 〈sup〉112〈/sup〉Sn targets, which are successfully used in two in-beam 〈em〉γ〈/em〉-ray spectroscopy experiments to study the structure of 〈sup〉114〈/sup〉Te and 〈sup〉142〈/sup〉Tb nuclei.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Vacuum, Volume 169〈/p〉 〈p〉Author(s): Chun Shang, Chenyang Wang, Guojian Xu, Changfu Li, Junhua You〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉High quality fabricating of the bimetallic structure of TA15 and Inconel 718 (IN718) is widely used in the aerospace filed. In this study, we have used laser additive manufacturing (LAM) technology to fabricate the bimetallic structure and to prevent the formation of brittle phases via Nb/Cu multi-interlayer. The results of this study showed that Nb/Cu multi-interlayer was very effective in preventing the generation of brittle Ti–Ni and Ti–Cu phases. The good metallurgical bonds were presented at these interfaces between TA15 and IN718. Mechanical properties of the bimetallic structure revealed that the tensile strength reached that of the weakest metal, Cu.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 22 August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Vacuum〈/p〉 〈p〉Author(s): Dexue You, Yongjian Wang, Zhenhua Yu, Yan Zhao, Zhenhua Xi, Yongjun Cheng, Lichen Sun, Donghui Meng, Xudi Wang〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉A new technique to measure the volume of the metal container based on dynamic differential pressure decay by using anodic aluminum oxide (AAO) leak element is presented. The AAO is chosen as the leak element because its conductance remains constant from vacuum to atmosphere. The container to be measured is connected to the vacuum system via the AAO leak element. The dynamic differential pressure decay with time between the inlet and outlet of AAO leak assembly was measured and fitted by an exponential function, followed by volume calculation. The volume of two different containers has been obtained using this method with nitrogen, helium, and argon, respectively. The influence of temperature fluctuation on experimental results under vacuum and atmospheric pressure outlet conditions was discussed. For vacuum outlet conditions, the temperature change caused by pressure decay in one single experiment is small enough to satisfy the isothermal hypothesis, which makes the influence of temperature fluctuation on the experimental results negligible. The preliminary results compared with the static expansion method demonstrate that this novel volume measurement technique is accurate, simple and efficient.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Vacuum, Volume 167〈/p〉 〈p〉Author(s): V.S. Rudnev, I.V. Lukiyanchuk, M.S. Vasilyeva, T.A. Kaidalova〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The functional properties of oxide coatings on metals depend on the composition and structure of their surface. In this work, the change with temperature of air annealing of the surface of NiO + CuO/TiO〈sub〉2〈/sub〉/Ti composites formed by the combination of plasma electrolytic oxidation of titanium in the phosphate-borate-tungstate electrolyte containing nickel and copper acetates and impregnation in the solution of nickel and copper nitrates was studied. It has been shown that varying the annealing temperature allows one to form the ensembles of micro- and nano-sized crystals of different composition and structure on the surface. CuO crystals are formed on the surface at annealing temperature T = 500 ÷ 700 °C, NiWO〈sub〉4〈/sub〉 crystals are present at T = 750 ÷ 850 °C, and Ni〈sub〉2.62〈/sub〉Ti〈sub〉0.69〈/sub〉O〈sub〉4〈/sub〉 whiskers - at T ≥ 900 °C. The data obtained suggest that the remaining electrolyte and impregnating solution accumulated on the surface and in the pores, as well as the transport of titanium from the coating depth to the surface, play an important role in the formation of crystals. It was summarized that air annealing at given temperatures of complex oxide coatings can be effective for controlling their architecture and surface composition at the micro- and nanolevels and, therefore, their functional properties.〈/p〉〈/div〉 〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0042207X1930822X-fx1.jpg" width="150" alt="Image 1" title="Image 1"〉〈/figure〉〈/p〉〈/div〉

Description: 〈p〉Publication date: September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Vacuum, Volume 167〈/p〉 〈p〉Author(s): M. Sukumar, L. John Kennedy, J. Judith Vijaya, B. Al-Najar, M. Bououdina, Gopinath Mudhana〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Ca〈sup〉2+〈/sup〉 substituted La〈sub〉2〈/sub〉CuO〈sub〉4〈/sub〉 (LCC) perovskite nanostructures have been prepared by microwave combustion. X-ray diffraction analysis indicates that the undoped La〈sub〉2〈/sub〉CuO〈sub〉4〈/sub〉 (LCC0) crystallizes within a single perovskite-type phase with an orthorhombic crystal structure. For smaller Ca〈sup〉2+〈/sup〉 doping of 0.1 (LCC1), a minor impurity was observed, while for concentrations 0.2 (LCC2) and 0.3 (LCC3), orthorhombic-to-tetragonal phase transformation occurs. In contrast, the tetragonal phase disappears at 0.4 and 0.5 (LCC4 and LCC5) as confirmed by XRD and Rietveld refinements. The orthorhombic and tetragonal perovskite phases have an average crystallite size in range 34.2–54.3 nm and 39.8–39.4 nm, respectively. Fourier transform infrared spectroscopy study established the characteristic absorption bands of La〈sub〉2〈/sub〉CuO〈sub〉4〈/sub〉 perovskite orthorhombic structure; the correlated bands are observed at 683 cm〈sup〉−1〈/sup〉 for La-O and 516 cm〈sup〉−1〈/sup〉 for Cu-O stretching modes. The optical band gap as determined by diffuse reflectance spectroscopy (DRS) increases then decreases with increasing Ca〈sup〉2+〈/sup〉 content due to the quantum confinement effect. The surface morphology observations using scanning electron microscopy display nano-sized pores and pore walls are fused grain boundaries. Magnetization-field curves exhibit a ferro-/paramagnetic behavior for undoped La〈sub〉2〈/sub〉CuO〈sub〉4〈/sub〉 while Ca-doped system has only a paramagnetic behavior due to the exchange of A and B sites within La〈sub〉2〈/sub〉CuO〈sub〉4〈/sub〉 host lattice.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Vacuum, Volume 169〈/p〉 〈p〉Author(s): Y.A. Odusote, J.M. Jabar, H.S. Bolarinwa, A.B. Akinbisehin〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The separating effects of Al from Ti-Al alloys were investigated via the molecular interaction volume model in vacuum distillation. The vapour-liquid equilibrium (VLE) composition and the activity coefficients of Ti-Al alloys at 1773 K–2273 K were predicted using only the properties of pure components. The calculated values of components activities are in good agreement with the corresponding FactSage data used for comparison. Predicted results of VLE show that the content of Ti in vapour and liquid phases increases with increasing distillation temperature. At 1873 K, in the vapour phase, the content of Ti was 0.000379 and 0.001353, while in the liquid phase it was 20 and 70 (all in wt %), respectively. The predicted separation coefficients indicate that Al can be separated from Ti completely by vacuum distillation. This study verified that FactSage Thermo-Chemical Software and Databases could serve as suitable source of experimental data for binary liquid alloys.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Vacuum, Volume 169〈/p〉 〈p〉Author(s): Fan Li, Xin Zhang, Hongliang Liu〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉[Ca〈sub〉24〈/sub〉Al〈sub〉28〈/sub〉O〈sub〉64〈/sub〉]〈sup〉4+〈/sup〉(4e〈sup〉−〈/sup〉) has great application prospects in electron emission and catalyst support, but suffers prolonged synthesis time and complicated multistep process. In this work, a direct and efficient calciothermic reaction was utilized for the rapid fabrication of subnanoporous electride ~ [Ca〈sub〉24〈/sub〉Al〈sub〉28〈/sub〉O〈sub〉64〈/sub〉]〈sup〉4+〈/sup〉(4e〈sup〉−〈/sup〉) directly from a novel mixture of CaAl〈sub〉2〈/sub〉O〈sub〉4〈/sub〉 (CA), CaO, and Ca powders under milder conditions (e.g., sintered at 1070 °C for 10 min in a vacuum). Phase-pure CA derived from calcinating was for the first time used as a precursor for the synthesis of dense C12A7:e〈sup〉−〈/sup〉 ceramic. The as-prepared C12A7:e〈sup〉−〈/sup〉 exhibited an electron density of ~2.3 × 10〈sup〉21〈/sup〉 cm〈sup〉−3〈/sup〉, covering the metal-insulator transition. The electron injection in the as-sintered C12A7:e〈sup〉−〈/sup〉 was verified by electron paramagnetic resonance analyses. Moreover, thermionic emission began to occur at 700 K and increased to 1.8 A/cm〈sup〉2〈/sup〉 at 1373 K when an extraction electrical field of 3.5 × 10〈sup〉4〈/sup〉 V/cm was applied. This demonstration shines new light on studies of formation avenues of polycrystalline C12A7:e〈sup〉−〈/sup〉 structure.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Vacuum, Volume 169〈/p〉 〈p〉Author(s): Dongzhi Li, Xudong Zhang, Jun Li, Lijun Zhao, Feng Wang, Xiaoquan Chen〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The first-principle method was used to investigate the elastic anisotropy and thermodynamic properties of Tantalum borides (B–Ta) compounds. The anisotropic indexes, the 3D surface constructions and 2D projections of Young's modulus indicate that B–Ta compounds are anisotropic. The order of elastic anisotropy is B〈sub〉2〈/sub〉Ta 〉 BTa〈sub〉2〈/sub〉〉 BTa 〉 B〈sub〉2〈/sub〉Ta〈sub〉3〈/sub〉〉B〈sub〉4〈/sub〉Ta〈sub〉3〈/sub〉〉B〈sub〉6〈/sub〉Ta〈sub〉5〈/sub〉. Dynamical and thermodynamic properties indicate that B–Ta compounds can keep the dynamical stability at ground state and high temperature. The calculated Debye temperatures of the various B–Ta compounds predict the good mechanical strength at elevated temperatures.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Vacuum, Volume 169〈/p〉 〈p〉Author(s): DongXu Wen, JiaKai Wang, Kang Wang, YiBo Xiong, Liang Huang, ZhiZhen Zheng, JianJun Li〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The hot tensile deformation and fracture behaviors of a typical ultrahigh strength steel are investigated by isothermal uniaxial tensile experiments over the tensile temperatures of 900–1150 °C and strain rates of 0.01–10 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si1.svg"〉〈mrow〉〈msup〉〈mrow〉〈mtext〉s〈/mtext〉〈/mrow〉〈mrow〉〈mo〉-〈/mo〉〈mn〉1〈/mn〉〈/mrow〉〈/msup〉〈/mrow〉〈/math〉. By combining the results of tensile tests and microstructural observation, the effects of deformation processing parameter (strain rate and tensile temperature) on the macroscopic plastic deformation behaviors, microscopic fracture morphologies and microstructural evolution are clarified. The studies indicate that the hot tensile behavior of the studied steel is greatly influenced by the competition of damage evolution, work hardening, and dynamic softening. With the increased strain rate, the strain rate sensitivity coefficients decrease, but the value of elongation to fracture increase from 0.38 to 0.50. The variations of microvoids or cracks in amounts and sizes show an increasing trend with the increased strain rate or the decreased tensile temperature. At the low tensile temperature (900 °C), the poor capability of necking diffusion hardly prevents the strain localization, and the mesoscopic damages easily take place. As the strain rate increases from 0.01 to 10 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si1.svg"〉〈mrow〉〈msup〉〈mrow〉〈mtext〉s〈/mtext〉〈/mrow〉〈mrow〉〈mo〉-〈/mo〉〈mn〉1〈/mn〉〈/mrow〉〈/msup〉〈/mrow〉〈/math〉, the neat fracture morphologies gradually change to the serrated. The main ductile fracture mechanisms transform from the intergranular fracture at the high tensile temperature and low strain rate to the transgranular fracture at the low tensile temperature and high strain rate.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Vacuum, Volume 168〈/p〉 〈p〉Author(s): Xuan Vuong Le, Thi Lan Anh Luu, Huu Lam Nguyen, Cong Tu Nguyen〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Nanocomposite materials of stoichiometric WO〈sub〉3〈/sub〉 nanobricks and commercial carbon nanotubes (CNTs) with different contents (0.5, 1.0 and 1.5 wt%) were simply fabricated by dispersing precursors in dimethylformamide. Stoichiometric WO〈sub〉3〈/sub〉 nanobricks were directly synthesised by a hydrothermal method without any post-annealing treatment. At low temperatures, the nanocomposite-based sensors showed synergistically enhanced ammonia gas-sensing properties in comparison with CNT-based and WO〈sub〉3〈/sub〉 nanobrick-based sensors. The 1.0 wt%-CNT-based sensor showed the most effective enhancement with 28-time higher response and 2-time shorter recovery times than the pristine CNT-based sensor. The limit of detection of the 1.0 wt%-CNT-based sensor could reach sub-ppm level detection (i.e. 150 ppb). The mechanism of this synergistic enhancement in composite materials was assigned to the hole transfer between the CNT surface and the inversion layer on stoichiometric WO〈sub〉3〈/sub〉 nanobricks.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Vacuum, Volume 168〈/p〉 〈p〉Author(s): Jitendra Pal Singh, Sangsul Lee, Keun Hwa Chae〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In the present work, zinc ferrite thin films on glass substrates were grown using radio-frequency sputtering method in oxygen environment at base pressure of 2 × 10〈sup〉−6〈/sup〉 Torr. As-grown films were annealed at 200 °C for 1, 3 and 5 h. X-ray diffraction study envisaged the existence of peaks corresponding to (311) and (440) planes of cubic spinel structure. Both the lattice parameter and crystallite size increased with annealing time leading to crystal perfection with annealing time. Fourier transform infrared spectroscopic study showed presence of bands corresponding to metal-oxygen vibrations in the spinel lattice. Fe 〈em〉K〈/em〉-edge extended X-ray absorption fine structure (EXAFS) measurements revealed that the tetrahedral site occupancy of Fe〈sup〉3+〈/sup〉 ions are 1.2 for as-grown zinc ferrite thin film. This occupancy is 1.18, 1.12 and 1.09 for annealing times of 1, 3 and 5 h, respectively. These observations were supported by Zn 〈em〉K〈/em〉-edge EXAFS investigations. X-ray magnetic circular dichroism measurements performed for these films show negative exchange interaction among the Fe〈sup〉3+〈/sup〉 ions situtated at different sites. Thus, zinc ferrite thin films having excess occupancy at tetrahedral site was successfully designed on glass substrate.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Vacuum, Volume 168〈/p〉 〈p〉Author(s): Bing Xu, Xinyu Yang, Hefa Cheng, Jingjing Zhao, Yan Wang, Ertao Zhu, Jiuxing Zhang〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉A high-quality LaB〈sub〉6〈/sub〉 single crystal with 2–10.24 mm in the diameter was prepared by the optical floating zone melting technique. The angular deviation from theoretical (100) crystal plane for LaB〈sub〉6〈/sub〉 single crystal was decreased from 6° to 0° through improving the quality of the seed and optimizing the growth process. When the growth rate was increased from 8 mm/h to 12 mm/h, the minimum value of X-ray rocking curve with the full width at half-maximum (FWHM) for LaB〈sub〉6〈/sub〉 single crystal obtained at V = 10 mm/h was only 0.068°, indicating that the single crystal had a high quality. The highest current density of J〈sub〉1kV〈/sub〉 = 46.8 A/cm〈sup〉2〈/sup〉 and the minimum work function of Φ〈sub〉e〈/sub〉 = 2.66 eV at T = 1873 K belongs to the LaB〈sub〉6〈/sub〉 single crystal with 2 mm in the diameter grown at V = 10 mm/h.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Vacuum, Volume 168〈/p〉 〈p〉Author(s): Y.J. Fang, X.S. Jiang, D.F. Mo, T.F. Song, Z.P. Luo〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The joining of 4J29 kovar alloy and 316L stainless steel with a Co interlayer was successfully accomplished by vacuum diffusion bonding in a temperature range of 855–945 °C, and an axial load of 10 MPa was employed to acquire diffusion-bonded joints. Interfacial microstructures of vacuum diffusion-bonded joints were analyzed using scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDS), X-ray diffraction (XRD) and transmission electron microscopy (TEM). The mechanical properties of bonded joints were evaluated by tensile strength and micro-hardness tests. The results showed that bonding temperature had significant effects on microstructures and mechanical properties of diffusion-bonded joints. The microstructures of diffusion layer at kovar alloy side and stainless steel side were comprised of Co solid solution of Fe–Co–Ni and solid solution + FeCo, respectively. In addition, a Kirkendall effect was found near Co interlayer. The diffusion behavior of various atoms was evaluated by Fick's law and Arrhenius relationship, and growth kinetics and activation energy of diffusion layer were also investigated. If bonding temperature was 945 °C, bonded joints would fracture at kovar alloy side, and maximum tensile strength of 516 MPa was acquired. In addition, the bonding mechanism of 4J29/Co/316L vacuum diffusion-bonded joints was also analyzed.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Vacuum, Volume 169〈/p〉 〈p〉Author(s): Qimeng Xia, Kan Xie, Ningfei Wang〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉This paper focuses on the main factors affecting the electron emission current–bias voltage (〈em〉I〈/em〉–〈em〉V〈/em〉) characteristics of cathodic hollow-cathode contactors and similarity conditions that should be satisfied in ground-based simulation experiments. These issues are of crucial importance for ensuring the reliability and credibility of the 〈em〉I〈/em〉–〈em〉V〈/em〉 data obtained in ground experiments, improving the 〈em〉I〈/em〉–〈em〉V〈/em〉 characteristics, and for reducing the mass flow consumption and dependence on the space environment. In this study, a 1-D spherically-symmetric model is first applied and compared with experimental data. We explore the influence of ion current, electron temperature, ion energy at the contactor exit, and environmental plasma density on the 〈em〉I〈/em〉–〈em〉V〈/em〉 curves, potential structure, and size of the plume area. The influence of the diameter of the vacuum chamber on the experimental 〈em〉I〈/em〉–〈em〉V〈/em〉 characteristics is investigated and the necessary conditions required for the diameter of the vacuum chamber is proposed. Moreover, an analysis is conducted of the effect of the background plasma source on the experimental 〈em〉I〈/em〉–〈em〉V〈/em〉 curves. The results suggest that the 〈em〉I〈/em〉–〈em〉V〈/em〉 behavior is sensitive to the exit ion current and flow rates. Another model is further employed to predict the exit ion-beam current for different net electron-emission currents and consumption flow rates at a given clamping current. The calculations show that a single-cathode contactor presents an extremely low utilization ratio. The exit ion current and utilization ratio should be effectively enhanced to improve the 〈em〉I〈/em〉–〈em〉V〈/em〉 characteristics.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 17 August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Vacuum〈/p〉 〈p〉Author(s): Nguyen Van Hung, Nguyen Ba Duc, Dinh Quoc Vuong, Nguyen Cong Toan, Tong Sy Tien〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉This paper presents the advances in EXAFS studies of the thermodynamic properties and anharmonic effects based on Debye-Waller factors presented in terms of cumulant expansion. The advances are succeeded based on the generalized anharmonic correlated Einstein model (GACEM) derived for all material structures including complex systems and separated for each structure by its anharmonic effective potential parameters contained in the derived analytical expressions of three first EXAFS cumulants and thermal coefficient. Many-body effects are accounted in the present one-dimensional model based on the first-shell near-neighbor contributions to the vibrations between absorber and backscatterer atoms. Morse potential is assumed to describe single-pair atomic interaction. The method created in this GACEM has the advantage of using it all considered quantities are provided based on only the calculation or measurement of second cumulants. The advanced studies are successfully applied to semiconductors. The results calculated using the present theory and those obtained by the created method for Ge and Si having diamond structure are found to be in good and reasonable agreement with experiment and with those of other theories.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Vacuum, Volume 169〈/p〉 〈p〉Author(s): Hyeong-Seop Im, Su-Kyung Kim, Tae-Ju Lee, Tae-Yeon Seong〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The opto-electrical properties of plasma-treated ITO films were investigated as functions of oxygen pressures (3.33 and 26.66 Pa) and radio-frequency (RF) plasma powers (50 and 150 W). The plasma-treated samples showed higher transmittance than the untreated sample. After the low-oxygen treatment, the carrier concentration increased with increasing plasma RF power and the figure of merit (FOM) also increased from 1.17 × 10〈sup〉−3〈/sup〉 to 1.65 × 10〈sup〉−3〈/sup〉 Ω〈sup〉−1〈/sup〉. This was not the case for the high-oxygen treatment. The ITO surfaces became smoother with increasing RF power. It was shown that unlike the high-oxygen treated samples, the In 3〈em〉d〈/em〉 and Sn 3〈em〉d〈/em〉 core levels for the low-oxygen-treated ITO films were shifted to higher energies compared to that of the untreated sample. ITO films of ITO/Ag/ITO multilayers (IAI) were plasma-treated at different conditions. Their transmittance maxima were in the range of 91.58–92.32% at 492–501 nm. The bottom-ITO-treated sample gave 23.1% higher mobility and 19% lower sheet resistance than the untreated IAI. The wetting characteristics of deionized (DI) water on the ITO films showed that the surface energy of ITO films increased from 34.22 to 71.14 mJ/m〈sup〉2〈/sup〉 when the oxygen pressures increased from 0 to 26.66 Pa.〈/p〉〈/div〉 〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0042207X19313521-fx1.jpg" width="381" alt="Image 1" title="Image 1"〉〈/figure〉〈/p〉〈/div〉

Description: 〈p〉Publication date: November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Vacuum, Volume 169〈/p〉 〈p〉Author(s): J.A. Borrego Pérez, Maykel Courel, Rocío Castañeda Valderrama, I. Hernández, Mou Pal, F. Paraguay Delgado, N.R. Mathews〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉TiO〈sub〉2〈/sub〉 thin films doped with low percentages (3, 7, and 10 at.%) of Er〈sup〉3+〈/sup〉 have been synthesized by sol gel spin coating technique. The influence of erbium concentration on the physical properties was analyzed using different characterization techniques such as X-ray diffraction, Raman spectroscopy, TEM analysis, EDS-SEM, AFM, UV–Visible transmittance spectroscopy, photoresponse and photoluminescence. The doped films exhibited significant modifications on the structural, optical and electrical properties due to the incorporation of erbium ions. The band gap energy was red shifted by Er doping indicating an improvement in visible light absorption. Intense Er〈sup〉3+〈/sup〉-based emission peaks in the range 520–560 nm were observed for all samples. It was observed that Er-dopant concentration had direct impact on photoluminescence intensity.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 17 August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Vacuum〈/p〉 〈p〉Author(s): L.K. Wang, J.J. Chen, J.Y. Yu, H.L. Zhao, J.K. Yang〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Highly textured F-doped SnO〈sub〉2〈/sub〉 (FTO) films with appropriate haze, high transparency and low resistance have been deposited on quartz glass substrates by spray pyrolysis technique at different substrate temperatures from 380 °C to 630 °C. The results show that all FTO films with pyramidal-shape grains are polycrystalline with cassiterite tetragonal structure and exhibit an obviously (200) preferred orientation. When the substrate temperature is 530 °C, the dislocation density of FTO films reaches a minimum value of 1.90 × 10〈sup〉15〈/sup〉 line/m〈sup〉2〈/sup〉, while the film thickness and root-mean-square roughness reach the maximum values of 613 nm and 32.3 nm, respectively. Highly textured FTO films sprayed at 530 °C exhibit the lowest turn on voltage of 1.95 eV and the optimal comprehensive optoelectrical performance with the high transmittance of 83.78%, low sheet resistance of 8.4 Ω/□ and high haze of 12.69%, which are the promising candidates as the transparent conductive oxide front electrode for film solar cells.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Vacuum, Volume 169〈/p〉 〈p〉Author(s): Mohammad Javad Sohrabi, Hamed Mirzadeh〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉To study the precipitation reactions, homogenization of the as-cast structure, thermomechanical processing, and high-temperature creep of superalloys, understanding the interdiffusion parameters of alloying elements is a vital requirement. This requires consistent diffusion parameters, which should be obtained by one technique. Accordingly, in the present work, based on the concept of residual segregation index during homogenization treatment of as-cast Inconel 718 superalloy, the activation energy (〈em〉Q〈/em〉) for interdiffusion of Nb, Mo, Cr, Ti, and Fe were determined as ~ 232, 286, 276, 256, and 280 kJ/mol, respectively. Moreover, the pre-exponential constant (〈em〉D〈/em〉〈sub〉0〈/sub〉) for Nb, Mo, Cr, Ti, and Fe were determined as 0.0037, 0.288, 0.283, 0.0430, and 0.31 cm〈sup〉2〈/sup〉/s, respectively. Based on these results, the diffusion coefficient of Mo in austenite was found to be the lowest value, which was consistent with the fact that the diffusion of Mo is the controlling micro-mechanism of homogenization.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Vacuum, Volume 169〈/p〉 〈p〉Author(s): T. Motomura, T. Tabaru〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉A unique magnetron sputtering cathode with a pinhole-centered permanent magnet has been developed for an inward enlargement of doughnut-shaped plasma discharge. Both a pinhole-centered permanent magnet and a tilt of magnetization vector to the normal to the top surface of the target play an important role for the inward enlargement of the plasma discharge area. The radial differentiated radial component of magnetic field strength, 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si1.svg"〉〈mrow〉〈mi〉d〈/mi〉〈mo〉|〈/mo〉〈mi〉B〈/mi〉〈mi〉r〈/mi〉〈mo〉|〈/mo〉〈mo linebreak="badbreak"〉/〈/mo〉〈mi〉d〈/mi〉〈mi〉r〈/mi〉〈/mrow〉〈/math〉, near the center is useful to explain the inward enlargement of the plasma discharge area. By the means of the tilt of magnetic field lines at 45° to the normal to the target surface, the magnetic field lines are compressed near the target center compared with conventional magnetron cathodes, and which also provides strong magnetic mirror configuration near the target center. The target utilization efficiency by volume ratio was 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si2.svg"〉〈mrow〉〈mo〉~〈/mo〉〈/mrow〉〈/math〉50 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si3.svg"〉〈mrow〉〈mtext〉%〈/mtext〉〈/mrow〉〈/math〉 in the use of proposed magnetron cathode. An aluminum deposition rate of 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si2.svg"〉〈mrow〉〈mo〉~〈/mo〉〈/mrow〉〈/math〉6.7 nm/min was obtained under experimental conditions with a target-substrate distance of 150 mm, Ar gas pressure of 0.2 Pa, and DC input power of 100 W.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Vacuum, Volume 168〈/p〉 〈p〉Author(s): Krzysztof Aniołek, Marian Kupka, Grzegorz Dercz〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The purpose of the paper was to determine the influence of cyclic oxidation parameters on oxidation kinetics, morphology, thickness and phase composition of oxide layers formed on Ti–6Al–7Nb alloy. The value of the activation energy of the process of cyclic oxidation of Ti–6Al–7Nb alloy was determined based on Arrhenius diagram. The result was 175.4 kJ/mol. The paper demonstrates that cyclic oxidation of Ti–6Al–7Nb alloy allows the formation of good-quality oxide layers, which, depending on the oxidation temperature, differed significantly in surface morphology. After oxidation at 600 °C, the obtained oxide layer was characterised by the presence of fine oxide particles, which often formed into shapes resembling grains. Oxidation at 700 °C led to the formation of larger agglomerated oxide particles. The cyclic oxidation process made it possible to obtain oxide layers of higher thickness compared to the isothermal oxidation method. After cyclic oxidation at 600 °C an oxide layer twice as thick (0.44 μm) was obtained. However, after oxidation at 700 °C, the obtained layer was approximately 55% (1.63 μm) thicker. Examinations of the phase composition of the oxide layers obtained at 600 and 700 °C showed the presence of three phases: α-Ti, TiO〈sub〉2〈/sub〉 (rutile) and Al〈sub〉2〈/sub〉O〈sub〉3〈/sub〉.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Vacuum, Volume 168〈/p〉 〈p〉Author(s): L.W. Xu, N. Lin, L.B. Zhao, C. Ma, Z.Y. Wang, Y.H. He〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The effects of AlN addition on mechanical properties, wear resistance and corrosion resistance of Ti(C,N)-based cermets are investigated by scanning electron microscope, X-ray diffraction, mechanical properties testing, abrasion testing and Tafel extrapolation. The results show that the appearance of Al element in binder phase may reinforce the binder phase of cermet. With increasing AlN additions, the Vickers hardness of cermet increases from 16.34 GPa to 17.60 GPa, and transverse rupture strength of cermet increases firstly and then decreases. Moreover, the extra AlN additions in cermet may reduce the friction coefficient of cermet, improve the wear resistance of materials and extend the service life of cutting tools during machining Inconel 718 nickel-based superalloy. Additionally, the existence of Al element in cermet may enhance the corrosion resistant of materials by inhibiting the corrosion process of binder phase in sodium hydroxide solution.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Vacuum, Volume 169〈/p〉 〈p〉Author(s): Nan Wang, Yang Qi〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The Bi film with well preferential orientation deposited on glass 〈em〉via〈/em〉 molecular beam epitaxy (MBE) method exhibits the magnetoresistance (MR) ratio greater than 125% with the temperature range from 2 K to 300 K in 9 T. The MR remains constant with the tilt angle less than 30° at room temperature. The transport properties of (00〈em〉l〈/em〉) preferred orientation Bi film with in-plane high-density low angle grain boundaries are similar to those of the single-crystal film. Meanwhile, the Bi film can be conversed from 〈em〉n〈/em〉-type to 〈em〉p〈/em〉-type by adjusting the temperature. Therefore, the low-cost polycrystalline Bi film is demonstrated to achieve large MR.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Vacuum, Volume 169〈/p〉 〈p〉Author(s): Zhengtao Wu, Peng Tang, Yiming Wu, Qimin Wang, Zhengbing Qi〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉AlCrSiVN coatings were deposited on cemented carbides substrates by a hybrid configuration of high-power impulse magnetron sputtering (HiPIMS) and cathode-arc-evaporation. The effect of varying V content on microstructure, hardness, and wear resistance of AlCrSiVN at RT–700 °C was investigated. Indentation hardness of AlCrSiVN coating decreases from 34.0 ± 1.1 to 26.3 ± 2.4 GPa with increasing V content from 0 to 7.5 at.%. However, elastic modulus of coating changes slightly. In addition, adhesion strength of AlCrSiVN to cemented carbide substrates first increases and then declines as the V addition content is increased. At RT, all friction coefficients of coatings are nearly the same, independent of V addition content. AlCrSiVN coating with 7.5 at.% V possesses the lowest wear rate at RT–600 °C. Lubricative V〈sub〉2〈/sub〉O〈sub〉5〈/sub〉 oxide scale forms on coating surface at 600 °C, providing self-lubrication during high-temperature wear. This favors to produce reduction of both friction coefficient and wear rate at 600 °C. At RT–600 °C, abrasive wear is responsible for the wear of AlCrSiVN coatings. However, the decrease of oxidation resistance induced by V addition produces a serious oxidation wear of coating at 700 °C.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Vacuum, Volume 169〈/p〉 〈p〉Author(s): Y.C. Lin, Guo-Dong Pang, Yu-Qiang Jiang, Xin-Gang Liu, Xiao-Yong Zhang, Chao Chen, Ke-Chao Zhou〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The hot deformation behavior and microstructural evolution of a Ti-55511 alloy in α+β region are investigated by uniaxial compressive tests at elevated temperatures. Transmission Electron Microscope (TEM) and Electron Backscattered Diffraction (EBSD) are employed to observe the microstructures. The spheroidization of lamellate α phases and the dynamic recrystallization (DRX) of β grains are analyzed. It is observed that the flow characteristics are prominently affected by deformation parameters, i.e., the flow stress, peak stress and flow softening stress decrease with the reduced strain rate or the increased deformation temperature. When the deformation temperature is slightly raised or the strain rate is properly reduced, the fraction of spheroidized α phase greatly increases. The substructures are formed in the lamellate α phase, and the β phase wedges into the lamellate α phase. Then, the lamellate α phase is fragmentized and spheroidized. The DRX of β grains is promoted with the raised strain rate or the reduced deformation temperature. Additionally, the higher dislocation density and obvious dislocation pile-ups can be noticed at the α/β interface, which induces the DRX nucleation of β grains at the α/β interface.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Vacuum, Volume 169〈/p〉 〈p〉Author(s): Tuba Yener, Azmi Erdoğan, Mustafa Sabri Gök, Sakin Zeytin〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Ti–TiAl〈sub〉3〈/sub〉 in-situ composites containing different percentages of Nb and B were effectively produced from Ti, Al, Nb and B powders by electric current assisted sintering (ECAS) technique which is a powder metallurgy processing method. Samples are sintered for 90 s with 2000 A current. The effect of B and Nb on the hardness, fracture toughness and wear resistance of samples were studied. The microstructure properties of the sintered samples were analysed with scanning electron microscopes (SEM), the phases in the samples were determined with XRD and their hardness and fracture toughness values were measured with a Vickers hardness tester with a load of 0.98 N and 98 N respectively. The highest fracture toughness value has been obtained with wt %10 Nb addition as 5.23 MPa m〈sup〉1/2〈/sup〉, whereas the highest hardness was determined as 965 HV for wt%5 B reinforced in situ-Ti-TiAl〈sub〉3〈/sub〉 composite. Best wear resistance was obtained in the 47.5Ti-47.5Al–5B sample. While Nb additive had a negatory effect on wear resistance, additive B had a positive effect on wear resistance.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Vacuum, Volume 169〈/p〉 〈p〉Author(s): Peng Deng, Hui Ren, Qingjie Jiao〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Ammonium perchlorate-based molecular perovskite (DAP)/graphene energetic composite was prepared and characterized. Molecule perovskite DAP was synthesized by the one-pot reaction of ammonium perchlorate, perchloric acid, and triethylenediamine, and DAP/graphene energetic composite was fabricated by physical mixing. The results suggested functionalized graphene can contribute to the improvement of combustion properties of DAP effectively. The energetic composite have high sustained exothermic capacity as well as good self-propagating combustion performance. Synergistic catalysis combustion mechanism of the composite system was provided based on relay-domino-like reactions, which enhanced heat and mass transfer between each component and promoted energy release. This work maybe offer a new idea for design and fabrication of high performance graphene-based energetic composite.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Vacuum, Volume 169〈/p〉 〈p〉Author(s): Qihui Wang, Shengbo Yang, Hebin Bao, Qianyu Wang, Xueming Li, Wenjing Yang〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Si is considered as a promising fuel for energetic materials and has received increasing attention. In this study, a novel core‒shell structure Si@CuO energetic material was successfully synthesized by self‒assembly method. Poly(4‒vinylpyridine) was used as cross linker to coat nano‒CuO on the surface of nano‒Si to form core‒shell structure Si@CuO energetic material. The morphology and composition of the nano‒Si, nano‒CuO and Si@CuO energetic materials were investigated in detail by scanning electron microscopy, transmission electron microscopy and X‒ray diffraction. The results demonstrate that the maximum actual heat release of Si@CuO with core‒shell structure is 1061.4 J/g when the equivalent ratio is 1.0, which is greater than 532.8 J/g of Si/CuO energetic materials prepared by ultrasonic mixing method. These results provide a helpful and practical strategy for the preparation of energetic materials with long‒term storage stability.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Vacuum, Volume 169〈/p〉 〈p〉Author(s): Bo Zhang, Jian-Tang Jiang, Li Liu, Guo-Ai Li, Wen-Zhu Shao, Liang Zhen〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Shear localization, which might result in the formation of shear bands in materials, is considered as a dominating deformation mechanism in materials under dynamic loading. In the present study, the microstructures of twin-induced ASBs in a Mg–Al–Mn alloy under ballistic impact were studied using scanning electron microscope and transmission electron microscope to investigate the localized shear deformation behavior of Mg alloys under high strain rate deformation. The results show that highly localized shear deformation mainly occurs at the boundary regions of deformed twins, resulting in the formation of narrow shear bands. The twin-induced ASBs composed of fine recrystallized grains and Mg〈sub〉17〈/sub〉Al〈sub〉12〈/sub〉 precipitates, while the internal part of twins shows the microstructure with elongated grains. The initiation of ASBs at the twin boundary regions is mainly attributed to the stress concentration at twin boundaries due to the dislocation pile-up. These results can contribute to further understanding of the shear deformation behavior of Mg alloys under dynamic loading.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Vacuum, Volume 169〈/p〉 〈p〉Author(s): N. Abharana, A. Biswas, P. Sarkar, S. Rai, S. Singh, S. Kumar, S.N. Jha, D. Bhattacharyya〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Interface roughness and interface diffusion are two very crucial parameters in determining the performances of thin film multilayer devices for applications in X-ray optics, neutron optics, giant magneto resistance devices etc. Preparation of these thin film multilayers with sharp interfaces is a technological challenge and researchers are using different methods to reduce the interface imperfections. It has been observed that by mixing nitrogen with argon in sputtering ambience during deposition of Ni layers, neutron reflectivity of Ni/Ti neutron supermirrors can be improved significantly.To elucidate the physical mechanism behind this observation, two sets of Ni/Ti periodic multilayers have been prepared using an indigenously built in-line magnetron sputtering system, in one set pure Ar has been used in sputtering ambience and in the other set a mixed ambience of Ar + N〈sub〉2〈/sub〉 has been used for deposition of Ni layers. Both the sets of multilayers have been thoroughly characterized by specular and diffused Grazing Incidence X-ray Reflectivity, Nuclear Resonance Reaction, X-ray diffraction and Grazing Incidence Extended X-ray Absorption Fine Structure measurements using synchrotron radiation. All the above complementary measurements unambiguously establish that the reason for improved performance of the supermirror deposited with Ar + N〈sub〉2〈/sub〉 ambience is the reduction of interface diffusion at Ti-on-Ni interfaces.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Vacuum, Volume 169〈/p〉 〈p〉Author(s): Niklas Hellgren, Jimmy Thörnberg, Igor Zhirkov, Maurico A. Sortica, Ivan Petrov, J.E. Greene, Lars Hultman, Johanna Rosen〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Titanium boride, TiB〈sub〉x〈/sub〉, thin films are grown in pure Ar discharges by high-power impulse magnetron sputtering (HiPIMS) from a compound TiB〈sub〉2〈/sub〉 target. Film compositions are determined by time-of-flight elastic recoil detection analysis and Rutherford backscattering spectrometry as a function of deposition temperature (〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si1.svg"〉〈mrow〉〈msub〉〈mrow〉〈mi〉T〈/mi〉〈/mrow〉〈mrow〉〈mi〉s〈/mi〉〈/mrow〉〈/msub〉〈/mrow〉〈/math〉 = 25–900 °C) and Ar pressure (〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si2.svg"〉〈mrow〉〈msub〉〈mrow〉〈mi〉p〈/mi〉〈/mrow〉〈mrow〉〈mi〉A〈/mi〉〈mi〉r〈/mi〉〈/mrow〉〈/msub〉〈/mrow〉〈/math〉 = 0.67–2.67 Pa, 5–20 mTorr). For reference, films are also grown by direct current magnetron sputtering (dcMS) under similar conditions. The HiPIMS waveform, average target power 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si3.svg"〉〈msub〉〈mi mathvariant="script"〉P〈/mi〉〈mi〉T〈/mi〉〈/msub〉〈mo〉,〈/mo〉〈/math〉 and resulting film compositions are strongly dependent not only on 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si2.svg"〉〈mrow〉〈msub〉〈mrow〉〈mi〉p〈/mi〉〈/mrow〉〈mrow〉〈mi〉A〈/mi〉〈mi〉r〈/mi〉〈/mrow〉〈/msub〉〈/mrow〉〈/math〉, but also on 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si1.svg"〉〈mrow〉〈msub〉〈mrow〉〈mi〉T〈/mi〉〈/mrow〉〈mrow〉〈mi〉s〈/mi〉〈/mrow〉〈/msub〉〈/mrow〉〈/math〉. At high pressures the effect of varying 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si1.svg"〉〈mrow〉〈msub〉〈mrow〉〈mi〉T〈/mi〉〈/mrow〉〈mrow〉〈mi〉s〈/mi〉〈/mrow〉〈/msub〉〈/mrow〉〈/math〉 on 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si3.svg"〉〈mrow〉〈msub〉〈mrow〉〈mi mathvariant="script"〉P〈/mi〉〈/mrow〉〈mrow〉〈mi〉T〈/mi〉〈/mrow〉〈/msub〉〈/mrow〉〈/math〉 is minimal, while at lower 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si2.svg"〉〈mrow〉〈msub〉〈mrow〉〈mi〉p〈/mi〉〈/mrow〉〈mrow〉〈mi〉A〈/mi〉〈mi〉r〈/mi〉〈/mrow〉〈/msub〉〈/mrow〉〈/math〉 the effect of 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si1.svg"〉〈mrow〉〈msub〉〈mrow〉〈mi〉T〈/mi〉〈/mrow〉〈mrow〉〈mi〉s〈/mi〉〈/mrow〉〈/msub〉〈/mrow〉〈/math〉 is more pronounced, due to substrate-temperature-induced gas rarefaction. Films grown by HiPIMS at 0.67 Pa are understoichiometric, with B/Ti 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si4.svg"〉〈mrow〉〈mo〉=〈/mo〉〈/mrow〉〈/math〉 1.4–1.5, while at 2.67 Pa, B/Ti decreases from 2.4 to 1.4 as 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si1.svg"〉〈mrow〉〈msub〉〈mrow〉〈mi〉T〈/mi〉〈/mrow〉〈mrow〉〈mi〉s〈/mi〉〈/mrow〉〈/msub〉〈/mrow〉〈/math〉 increases from 25 to 900 °C. dcMS-deposited films are overstoichiometric (B/Ti 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si5.svg"〉〈mrow〉〈mo〉≃〈/mo〉〈/mrow〉〈/math〉 3) when grown at low pressures, and near-stoichiometric (B/Ti 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si5.svg"〉〈mrow〉〈mo〉≃〈/mo〉〈/mrow〉〈/math〉 1.9–2.2) for higher 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si2.svg"〉〈mrow〉〈msub〉〈mrow〉〈mi〉p〈/mi〉〈/mrow〉〈mrow〉〈mi〉A〈/mi〉〈mi〉r〈/mi〉〈/mrow〉〈/msub〉〈/mrow〉〈/math〉. All experimental results are explained by differences in the ionization potentials of sputtered Ti and B atoms, together with 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si2.svg"〉〈mrow〉〈msub〉〈mrow〉〈mi〉p〈/mi〉〈/mrow〉〈mrow〉〈mi〉A〈/mi〉〈mi〉r〈/mi〉〈/mrow〉〈/msub〉〈/mrow〉〈/math〉- and 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si1.svg"〉〈mrow〉〈msub〉〈mrow〉〈mi〉T〈/mi〉〈/mrow〉〈mrow〉〈mi〉s〈/mi〉〈/mrow〉〈/msub〉〈/mrow〉〈/math〉 -dependent gas-phase scattering.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Vacuum, Volume 168〈/p〉 〈p〉Author(s): Sihong Wu, Gangqiang Zha, Kun Cao, Jinghua Fu, Yang Li, Yawei Wang, Wanqi Jie, Tingting Tan〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉High quality CdZnTe epitaxial thick films with thickness of about 1.1 mm were grown on GaAs (001) substrates by close spaced sublimation method (CSS). The dislocation density of the CdZnTe epitaxial films were found to be approximately 1.05 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si1.svg"〉〈mrow〉〈mo〉×〈/mo〉〈/mrow〉〈/math〉 10〈sup〉5〈/sup〉 cm〈sup〉−2〈/sup〉, and the full width at half maximum intensity of X-ray rocking curve is 166 arcsec. The mobility-lifetime (μτ) product and mobility (μ) of electrons were measured to be 1.0 × 10〈sup〉−3〈/sup〉 cm〈sup〉2〈/sup〉V〈sup〉−1〈/sup〉 and 750 cm〈sup〉2〈/sup〉 V〈sup〉−1〈/sup〉s〈sup〉−1〈/sup〉, respectively. The CdZnTe thick film detector has an energy resolution of 2.2% for 〈sup〉241〈/sup〉Am@5.49 MeV alpha particles and 31% for 〈sup〉241〈/sup〉Am@59.5 KeV gamma-ray.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Vacuum, Volume 168〈/p〉 〈p〉Author(s): Jian-lei Zhu, Li-sheng Zhong, Yun-hua Xu, Shao-xiong zhang, Zheng-xin Lu〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉NbTi-(NbTi)C Fe-based composites are fabricated by 〈em〉in-situ〈/em〉 diffusion reaction. The locally reinforced (NbTi)C cermet layer formed by carrying out the reaction of C + β-NbTi → (NbTi)C, which resulted in the formation of the core-annular shell structure with a ductile core (NbTi) and high hardness annular shell (cermet layer). The (NbTi)C cermet layer is composed of two zones, where ZoneⅠ, near the GCI, is composed of micron and sub-micron-sized particles; and ZoneⅡ, near the remnant β-NbTi, is composed of sub-micron-sized particles. The detailed microstructural, elemental and morphological analysis has been carried out to unveil the phase distribution and microstructural changes in the (NbTi)C cermet layer. The results reveal that the cermet layer consists of (NbTi)C particles with different Ti/(Ti + Nb) ratios, ranging from 0.6308 to 0.8330, which have different morphology: the fusiform particles and near spherical or cubic particles. Moreover, the nanoindentation results of (NbTi)C layer indicate that the maximum hardness and elastic modulus is 31.43 GPa and 473.11 GPa, respectively. It is worth mention that the remnant β-NbTi and α-Fe phases, surrounding the (NbTi)C cermet layer, render high plasticity. Therefore, the combination of β-NbTi, α-Fe and (NbTi)C phases can effectively improve the hardness and plasticity of as-prepared composites.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Vacuum, Volume 168〈/p〉 〈p〉Author(s): Di Xiang, Lei Yang, Ying Hou, Jiaqi Zhu, Ming Yang〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Metal-semiconductor nanohybrids are desirable composite materials for improving light utilization efficiency thanks to their configurable geometries and interfaces. In this paper, CdS nanochains derived from Cd(OH)〈sub〉2〈/sub〉 nanofibers are uniformly decorated by Au nanoparticles using a facile solution reduction method. The resultant one-dimensional hybrid nanostructures show enhanced photocurrents under visible light irradiation. The photoelectrochemical enhancement is dependent on the size of Au nanoparticles, which may be tuned by varying the compositions of reductants. It is found that Au nanoparticles may not only serve as electron sinks for improving charge carrier separation efficiency but also increase the visible light absorption. Optical spectroscopies and FDTD calculations indicate that larger Au nanoparticles can result in more obvious plasmonic enhancement with a greater impact of localized surface plasmon resonance on interfacial coupling.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Vacuum, Volume 168〈/p〉 〈p〉Author(s): Dongzhi Li, Xudong Zhang, Cong Liu, Feng Wang, Hongwei Zhang, Ming Tian〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The structural stability, elastic properties and elastic anisotropy of cubic sesquioxides Sc〈sub〉2〈/sub〉O〈sub〉3〈/sub〉, Y〈sub〉2〈/sub〉O〈sub〉3〈/sub〉 and In〈sub〉2〈/sub〉O〈sub〉3〈/sub〉 under pressure are systematically investigated using the first-principles calculations. For three materials, the pressure dependent behaviors of the structural stability and mechanical properties are investigated from 0 to 15 GPa. The formation enthalpy, volume change, phonon frequencies and mechanical stability confirm that cubic Sc〈sub〉2〈/sub〉O〈sub〉3〈/sub〉, Y〈sub〉2〈/sub〉O〈sub〉3〈/sub〉 and In〈sub〉2〈/sub〉O〈sub〉3〈/sub〉 exhibit the structural stability at ground state and high pressure. The elastic constants, elastic moduli and anisotropy increase with the increasing pressure. The pressure promotes that the ductile ability and the anisotropic degree increase with the increasing pressure.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: June 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Vacuum, Volume 164〈/p〉 〈p〉Author(s): Xiao Zuo, Rende Chen, Dong Zhang, Peiling Ke, Aiying Wang〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Modification of micro-particle size during cathodic arc deposition is an important issue for the preparation of hard coatings and nanomaterials. In this work, a coil winding and permanent magnets were applied to adjust the magnetic field of a cathodic arc source. The motion of luminous group spots was investigated through high speed imaging method. The average size of the spots was reduced with the decrease of arc current. When the arc current was higher than 80 A, the size probability distributions of the spots presented as bimodal functions. But it turned into unimodal functions at lower arc currents. By changing the coil current three kinds of spots position distributions were observed, such as centered distribution, intermediate and periphery annulus distributions. Their corresponding spots movements were stochastic, spiral and circular motion dominated. The influence of magnetic field on the spots motion was discussed. Although the average spots size was reduced with the increase of coil current to 2.5 A. Further increasing the coil current leaded to a gathering of spots towards the periphery region of the cathode surface, and an increase of the spots size. Finally, a relationship between the spots size and micro-particles size was established.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: June 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Vacuum, Volume 164〈/p〉 〈p〉Author(s): Ramesh Paudel, Jingchuan Zhu〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The structural, electronic, magnetic, elastic and phonon properties of bulk and electronic and magnetic properties of (111)-surfaces of AlCu〈sub〉2〈/sub〉Mn-type Fe〈sub〉2〈/sub〉MnP Heusler alloy have been investigated by using density functional theory based on the generalized gradient approximation scheme. The cohesive energy confirmed the stability of the alloy considered at an equilibrium lattice constant of 5.5628 Å. We observed a half-metallic nature in the bulk alloy with energy band gaps of 0.34 eV and spin-flip gaps of 0.09 eV with 100% spin-polarization in the minority spin electrons. The computed magnetic moments for the Fe〈sub〉2〈/sub〉MnP alloy are found to be 4 μ〈sub〉B〈/sub〉/f.u. The investigated elastic constants, phonon dispersion and density phonon states showed that the Fe〈sub〉2〈/sub〉MnP alloy is mechanically and dynamically stable. We also found that the alloy is ductile from the Poisson's and B/G ratios. The half-metallic ferromagnetic nature is preserved in the P (111)-terminated slab among all terminations with 100% spin-polarization which is a crucial property of spin devices, since it can be optimize their performance. The spin-polarization clearly decreases by nearly 75% for Fe (111) and Mn (111)-terminated slabs due to surface states located below the Fermi level. Moreover, the computed atomic magnetic moments of (111)-slabs of the Fe〈sub〉2〈/sub〉MnP Heusler alloy are extremely close to the atomic bulk values.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: June 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Vacuum, Volume 164〈/p〉 〈p〉Author(s): Songbin Li, Chuanbin Wang, Qiang Shen, Lianmeng Zhang〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉This paper carries out a detailed study on magnetic and electrical transport properties of La〈sub〉0·67〈/sub〉Ca〈sub〉0·33〈/sub〉MnO〈sub〉3〈/sub〉 (LCMO) thin films deposited on SrTiO〈sub〉3〈/sub〉 substrates with different orientations, which provide varying degrees of in-plane tensile strain. As confirmed by the structure and morphology analyses, the homogeneous LCMO thin films with columnar grains are epitaxially grown along the orientations of the substrates, and the suffered tensile strain in the film is increasing from (100) LCMO to (111) LCMO. The obtained data suggest that the magnetic and electrical transport properties of the thin films are sensitive to the substrate-induced tensile strain. The resistivity, temperature coefficient of resistivity (TCR) and magnetoresistance (MR) of the thin films were in ascending order of (1 0 0) 〈 (1 1 0) 〈 (1 1 1), while the ferromagnetic-paramagnetic transition temperature (T〈sub〉C〈/sub〉), magnetization and metal-insulator transition temperature (T〈sub〉IM〈/sub〉) were in descending order of (1 0 0) 〉 (1 1 0) 〉 (1 1 1).〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: June 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Vacuum, Volume 164〈/p〉 〈p〉Author(s): Y.X. Zhou, Y.L. Xue, K. Zhou〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Tungsten-copper (WCu) contact materials are the core components of high-voltage electrical switches. However, significant arc ablation effect at high voltage and high current often leads to connection interruption and mechanical loss, which seriously affects the safe operation of appliances. In this paper, the failure mechanisms of tungsten-copper contact materials caused by significant arc ablation in the sulfur hexafluoride (SF〈sub〉6〈/sub〉) atmosphere were investigated. Results showed that the arc ablation of contact materials is mainly caused by the evaporation and splashing of copper component which has a low melting point, followed by the ablation and spallation of the tungsten (W) skeleton structure. All of these have roughened the surface of contact materials and then further accelerated the volatilization of copper (Cu) component and the reactions between the contact materials and arc extinguishing medium of SF〈sub〉6〈/sub〉. Finally, the contact materials lost their functions of arc extinguishing and current switching. Simulated experimental work has also been performed and it verified the above observed failure mechanisms of contact materials. Due to the instantaneously high temperature and high voltage generated during the arcing, both the Cu and W phases in the WCu alloy have suffered significant evaporation and mass losses.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: June 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Vacuum, Volume 164〈/p〉 〈p〉Author(s): R. Baby Suneetha, P. Selvi, C. Vedhi〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Nanocomposite of Zinc doped Iron oxide/Graphene Oxide/Chitosan was prepared using optimized quantity of the components by simple solution mixing-evaporation method. The structure of the composite was studied by UV–Vis, FTIR, XRD, SEM, HRTEM and AFM. The results obtained from these analyses showed the formation of homogeneous mixture with strong interaction between the constituents and evidenced by the shift in peak position in both UV–Vis and FTIR spectra. Band gap calculated was found to be 2.28eV which indicates the conducting nature of the composite. The formation of composite in nano dimensions of around 20 nm was proved by XRD, SEM and HRTEM studies. Thermal stability of the sample was investigated by TG/DTA and DSC techniques and showed improved thermal stability with the increase in glass transition temperature of chitosan by 78°c. Electrochemical characteristics of the composite was studied by cyclic voltammetry and capacitative behavior was studied by impedance studies (EIS). These electrochemical investigations revealed good adherent nature of the composite on electrode surface at pH1 and greater electrochemical stability with well defined redox peaks. EIS showed that the nanocomposite modified electrode exhibited good capacitance behavior with the bode phase angle of 87° which proves it to be a very good candidate for supercapacitor applications.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: June 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Vacuum, Volume 164〈/p〉 〈p〉Author(s): Xiaohui Zhang, Yi Zhang, Baohong Tian, Yanlin Jia, Yong Liu, Kexing Song, Alex A. Volinsky〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Al〈sub〉2〈/sub〉O〈sub〉3〈/sub〉-Cu/25W5Cr and Al〈sub〉2〈/sub〉O〈sub〉3〈/sub〉-Cu/35W5Cr composites were fabricated by vacuum hot-pressing sintering and internal oxidation process. The electrical conductivity, relative density and Brinell hardness were measured. The effects of the nano-Al〈sub〉2〈/sub〉O〈sub〉3〈/sub〉 and tungsten on the Al〈sub〉2〈/sub〉O〈sub〉3〈/sub〉-Cu/(W, Cr) composites hot deformation were investigated through the isothermal compression tests using the Gleeble-1500D thermo-mechanical simulator ranging from 650 °C to 950 °C and 0.001–10 s〈sup〉−1〈/sup〉 strain rate. The deformed microstructure was characterized and analyzed by optical and transmission electron microscopy. The interaction of work hardening, dynamic recovery and dynamic recrystallization was illustrated. It is demonstrated that Cr particles were extruded into strips; W particles underwent a slight deformation during the hot compression. Besides, the higher tungsten content composite had higher flow stress. Nano-Al〈sub〉2〈/sub〉O〈sub〉3〈/sub〉 particles pinned dislocations and inhibited the dynamic recovery and dynamic recrystallization. In addition, it is still in the stage of sub-crystals formation at 850 °C, 0.01s〈sup〉−1〈/sup〉. Consequently, the Al〈sub〉2〈/sub〉O〈sub〉3〈/sub〉-Cu/35W5Cr composite has typical dynamic recovery characteristic. Hence, Al〈sub〉2〈/sub〉O〈sub〉3〈/sub〉-Cu/(W, Cr) composites demonstrate outstanding high temperature performance.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: June 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Vacuum, Volume 164〈/p〉 〈p〉Author(s): Nima Barri, Amir Reza Salasel, Alireza Abbasi, Hamed Mirzadeh, Massoud Emamy, Mehdi Malekan〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The effects of nickel addition on the microstructure and phase formation in the magnesium-silicon alloy were studied. Besides the primary and eutectic in-situ formed Mg〈sub〉2〈/sub〉Si phase in the Mg〈img src="https://sdfestaticassets-eu-west-1.sciencedirectassets.com/shared-assets/16/entities/sbnd"〉Si alloys, a new intermetallic phase was identified in the Ni-containing alloys. Based on energy-dispersive spectroscopy (EDS) and X-ray diffraction analyses, it was shown that this phase contains Mg, Ni, and Si elements, which contradicts the presence of the expected Mg〈sub〉2〈/sub〉Ni phase. Through rigorous EDS analysis, the new in-situ formed phase was identified as (Mg,Ni)〈sub〉3〈/sub〉Si or more accurately as Mg〈sub〉8〈/sub〉Ni〈sub〉7〈/sub〉Si〈sub〉5〈/sub〉 intermetallic compound, called χ-phase, which has not been reported so far in the Mg〈img src="https://sdfestaticassets-eu-west-1.sciencedirectassets.com/shared-assets/16/entities/sbnd"〉Si〈img src="https://sdfestaticassets-eu-west-1.sciencedirectassets.com/shared-assets/16/entities/sbnd"〉Ni ternary space. Finally, the properties of the studied Mg〈img src="https://sdfestaticassets-eu-west-1.sciencedirectassets.com/shared-assets/16/entities/sbnd"〉Si〈img src="https://sdfestaticassets-eu-west-1.sciencedirectassets.com/shared-assets/16/entities/sbnd"〉Ni alloys were also briefly discussed.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: December 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Vacuum, Volume 158〈/p〉 〈p〉Author(s): Shuai Sun, Lei Wang, Chengyang Wang, Yang Zhang〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Coal tar pitch with a softening point (SP) of 78 °C is mixed with divinylbenzene (DVB) and then spheroidized by suspension method in dimethyl silicone oil for 1 h. During the spheroidization process, the mixtures of pitch and DVB are copolymerized due to vinyl in DVB. After vacuum-assisted heat treatment, the copolymer spheres can be stabilized completely and then carbonized directly at high temperature under Ar atmosphere without melting and deformation. After activation using steam at 850 °C for 1.5 h, spherical activated carbon (SAC) with smooth surface and specific surface area S〈sub〉BET〈/sub〉 = 520 m〈sup〉2〈/sup〉 g〈sup〉−1〈/sup〉 can be prepared. Further studies show that mesopore volume of the SAC is 0.29 cm〈sup〉3〈/sup〉 g〈sup〉−1〈/sup〉, which accounts for 72.5% of the total pore volume. The good spherical morphology, smooth surface and rich pores (micropores and mesopores) can be attributed to appropriate copolymerization and vacuum-assisted treatment.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 16 May 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Vacuum〈/p〉 〈p〉Author(s): Yuki Murayama, Kazuma Ueno, Yuya Oshio, Hideyuki Horisawa, Ikkoh Funaki〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The Magnetic sail (MagSail) is a space propulsion system utilizing an interaction between the solar wind particles and the artificial magnetic field generated by the coil on the spacecraft. The thrust is proportional to the magnetospheric size. In order to improve an efficiency of capturing the solar wind, a multi-coil magnetic sail, using several coils, is proposed. In this research, to evaluate the magnetospheric size of multi-coil magnetic sail, multi-coil magnetic sail consisted of three-small coils was developed and the magnetic field strength was characterized by the magnetic field probes. As a result, a 330 mm-magnetosphere was found in the normalized magnetic field distribution. In space, the ion Larmor radius at the magnetospheric boundary 〈em〉r〈/em〉〈sub〉〈em〉Li〈/em〉〈/sub〉 is about 72 km at 1 AU from the sun, and a magnetospheric size in space 〈em〉L〈/em〉〈sub〉space〈/sub〉 = 1.6 km is obtained by substitution 〈em〉r〈/em〉〈sub〉〈em〉Li〈/em〉〈/sub〉 = 72 km for the non-dimensional parameter 〈em〉r〈/em〉〈sub〉Li〈/sub〉/〈em〉L〈/em〉 = 4.5, then, MagSail produce 82 mN thrust.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: December 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Vacuum, Volume 158〈/p〉 〈p〉Author(s): M. Jaroš, J. Musil, R. Čerstvý, S. Haviar〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The article reports on the effect of the energy ℰ delivered into the growing film on its macrostress, microstructure, mechanical properties and resistance to cracking of Ti(Al,V)N films. The Ti(Al,V)N films were deposited on Si(111) and Mo substrates by magnetron sputtering in a mixture Ar + N〈sub〉2〈/sub〉 gases using a dual magnetron with closed magnetic field and equipped with TiAlV (6 at.% Al, 4 at.% V) alloy targets. It is shown that the compressive macrostress σ in sputtered films can be reduced either by the pulsed bipolar bias voltage U〈sub〉sp〈/sub〉 with alternating negative and positive pulses or the electron and ion bombardment during overshoots in the pulsed magnetron sputtering. All sputtered films with high ratio H/E〈sup〉∗〈/sup〉 ≥ 0.1, compressive macrostress (σ 〈 0), and non-columnar microstructure exhibit an enhanced resistance to cracking; here H is the hardness and E〈sup〉∗〈/sup〉 is the effective Young's modulus. The high compressive macrostress in the film is not the necessary condition for the formation of the films with an enhanced resistance to cracking.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: January 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Vacuum, Volume 159〈/p〉 〈p〉Author(s): S. Balamurugan, A.R. Balu, J. Srivind, K. Usharani, V. Narasimman, M. Suganya, V.S. Nagarethinam〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The present work aims to synthesize CdO〈img src="https://sdfestaticassets-eu-west-1.sciencedirectassets.com/shared-assets/16/entities/sbnd"〉Al〈sub〉2〈/sub〉O〈sub〉3〈/sub〉 nanocomposite and to study its visible light activated photocatalytic performance against metanil yellow dye. Precipitation method was employed to synthesize pure CdO, Al〈sub〉2〈/sub〉O〈sub〉3〈/sub〉 and CdO〈img src="https://sdfestaticassets-eu-west-1.sciencedirectassets.com/shared-assets/16/entities/sbnd"〉Al〈sub〉2〈/sub〉O〈sub〉3〈/sub〉 nanoparticles. Diffraction peaks related to cubic CdO and monoclinic θ-Al〈sub〉2〈/sub〉O〈sub〉3〈/sub〉 were observed in the XRD pattern of the composite. XPS spectrum confirmed the presence of Cd, Al and O in the composite. Peaks related to Cd〈img src="https://sdfestaticassets-eu-west-1.sciencedirectassets.com/shared-assets/16/entities/sbnd"〉O and O〈img src="https://sdfestaticassets-eu-west-1.sciencedirectassets.com/shared-assets/16/entities/sbnd"〉Al〈img src="https://sdfestaticassets-eu-west-1.sciencedirectassets.com/shared-assets/16/entities/sbnd"〉O bonds were observed from the FTIR spectrum of the composite. Photocatalytic activity confirmed that the CdO〈img src="https://sdfestaticassets-eu-west-1.sciencedirectassets.com/shared-assets/16/entities/sbnd"〉Al〈sub〉2〈/sub〉O〈sub〉3〈/sub〉 nanocomposite exhibits a maximum degradation efficiency of 82.09% against MY dye which was found to be better than pure CdO and Al〈sub〉2〈/sub〉O〈sub〉3〈/sub〉 nanoparticles due to the synergistic effect, high surface area and the formation of p-n junction at the interface of CdO and Al〈sub〉2〈/sub〉O〈sub〉3〈/sub〉. The CdO〈img src="https://sdfestaticassets-eu-west-1.sciencedirectassets.com/shared-assets/16/entities/sbnd"〉Al〈sub〉2〈/sub〉O〈sub〉3〈/sub〉 composite catalyst synthesized via precipitation method seems to be more stable and definitely it will be a potential candidate in photocatalysis related field.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: December 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Vacuum, Volume 158〈/p〉 〈p〉Author(s): A. Kozlovskiy〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The paper presents the results of studying the effect of irradiation of Fe〈sup〉7+〈/sup〉 ions with an energy of 1.5 MeV/nucleon on structural properties of AlN ceramics at an irradiation temperature of 300, 500, 700 and 1000 K. The choice of ion type and irradiation conditions was made by studying the processes of defect formation as a result of particles effect with energies close to fission fragments of nuclear fuel (≤90–100 MeV) and temperatures 0.1–0.3 T〈sub〉melt〈/sub〉, typical for annealing defects. From the data obtained by the XRD, SEM, EDX methods, it is established that an increase in irradiation temperature above 500 K leads to a reduction in distortions and deformation of the crystal lattice under irradiation. It was found that with an increase in the irradiation dose, amorphous-like grains with a high oxygen content are formed in the structure, which are characteristic for the impurity phase of Al〈sub〉2〈/sub〉O〈sub〉3〈/sub〉, the content of which in the ceramic structure does not exceed 5%. In this case, an increase in the irradiation temperature leads to a decrease in impurity phase concentration in the structure. It has been established that for samples irradiated at high temperatures 700–1000 K, the decrease in strength properties is less than for samples irradiated at a temperature of 300 and 500 K. Such a difference can be explained by partial annealing and annihilation of defects as a result of elevated temperatures. The decrease in thermal conductivity coefficient in irradiated samples is due to an increase in defects concentration in structure, as well as a decrease in their mobility.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: December 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Vacuum, Volume 158〈/p〉 〈p〉Author(s): R.Z. Xu, H. Li, Y.X. Hou, Z.C. Wei, F.S. Li, S.L. Cui, X.H. Liu〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The characteristics of vacuum electron beam welding (VEBW) of AZ31 Mg alloy (2.4 mm) to Q235 steel (2.0 mm) were investigated. The results showed that AZ31 and noncoated Q235 could not be joined together after VEBW. With an addition of Al-Zn coating, the lap joint of AZ31 and Q235 was obtained successfully. Firstly, the high amount of Al in the Al–Zn coating decreased the excessive vaporization of Zn. Secondly, the reasonable vaporization of Zn element and diffusion into the AZ31 of Al element in the coating improved the wettability of Mg/steel faying surface during the EBW process in vacuum conditions. Thirdly, the pre-existing Al–Fe intermetallic compound (IMC) was molten and kept at the Mg-steel interface, preventing a direct contact between molten Mg and steel during EBW. Subsequently, it formed an Al〈sub〉5〈/sub〉Fe〈sub〉2〈/sub〉 IMC layer, realizing the metallurgical bonding of AZ31 to Q235. The hardness testing indicated that the Al-Fe interface zone exhibited a peak in the hardness values. The average load of the AZ31/Al-Zn-coated Q235 joint with a width of 10 mm could reach 2.2 kN and the lap joint fractured at the faying surface between Al〈sub〉5〈/sub〉Fe〈sub〉2〈/sub〉 IMC layer and AZ31 substrate after tensile-shear testing.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 23 August 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Vacuum〈/p〉 〈p〉Author(s): R. Sitek〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The article discusses the effect of high temperature aluminizing processes on microstructure and corrosion resistance in 0.1 M Na〈sub〉2〈/sub〉SO〈sub〉4〈/sub〉 solution at room temperature of the IN 740H nickel superalloy. The aluminizing processes were carried out by chemical vapor deposition (CVD): (a) in AlCl〈sub〉3〈/sub〉 vapors, (b) in a mixture of AlCl〈sub〉3〈/sub〉+ZrCl〈sub〉3〈/sub〉 vapors under a hydrogen atmosphere as carrier gas under the same conditions (process temperature −1040 °C, time-7h under reduced pressure of 150 hPa). Observations of the surface of the produced layers showed that the additional modification of the aluminizing process with zirconium affects the morphology of the layers formed as compared to the unmodified aluminizing process. It was also found that the prepared aluminide layers unmodified and modified additionally with zirconium improve corrosion resistance of the Inconel 740H nickel superalloy. On the basis of the conducted tests, it was also found that after high-temperature aluminizing processes in the IN 740H substrate precipitates are formed at the grain boundaries containing carbide forming elements such as: Cr, Ti, Nb, which may form secondary carbides, e.g. M〈sub〉6〈/sub〉C, M〈sub〉7〈/sub〉C〈sub〉3〈/sub〉.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: January 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Vacuum, Volume 159〈/p〉 〈p〉Author(s): Oleg Sazhin〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The effect of surface roughness on free molecular gas flow in 3-D rectangular channel is studied by the test particle Monte Carlo method. It is shown that the so-called “superdiffuse” scattering observed in a number of flow experiments is a result of disregarding the surface roughness effect. Its consideration leads to a satisfactory agreement between the computed and experimental data.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: December 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Vacuum, Volume 158〈/p〉 〈p〉Author(s): Bharath Bandi, Soumitra Kumar Dinda, Jyotirmaya Kar, Gour Gopal Roy, Prakash Srirangam〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Zircaloy-4 to Zircaloy-4 (Zr-4) similar butt joints were prepared using Electron Beam Welding (EBW) technique under different weld conditions such as with beam oscillation, without beam oscillation and at different welding speeds. Three-dimensional (3D) visualisation of porosity in weld joints was carried out using X-ray computed tomography (XCT) technique. Quantification of porosity such as the average size, number and shape of the pores were evaluated and compared among weld joints produced under different conditions. XCT results show that the porosity of the welds increased substantially with the increase in the weld speed. More interestingly, the results also show that there is a significant decrease in porosity of the joint produced with beam oscillation condition. An increase in weld speed from 700 mm/min to 1000 mm/min resulted in a significant increase in pore density (from 16 to 313 per mm3) and it was observed that the average size of the macro pores increased from 96.4 μm to 121.5 μm. The joints prepared with beam oscillation produced least number of pores with minimum percentage of macro pores and maximum percentage of spherical pores in it. Raman spectroscopy results confirmed the presence of hydrogen gas in pores of all the weld joints.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: December 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Vacuum, Volume 158〈/p〉 〈p〉Author(s): Yongdong Wang, Jixiao Wang, Haiting Hu, Junsheng Meng, Xia Zhao〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉By using Y〈sub〉2〈/sub〉O〈sub〉3〈/sub〉 nanoparticles, instead of part or all of Al〈sub〉2〈/sub〉O〈sub〉3〈/sub〉, acting as filler, Y〈sub〉2〈/sub〉O〈sub〉3〈/sub〉-modified aluminide coatings were produced on 309 stainless steel using a conventional pack-cementation method at 700 °C for 6 h. Effect of Y〈sub〉2〈/sub〉O〈sub〉3〈/sub〉 content in the pack mixtures on the cyclic-oxidation resistance of different aluminide coatings was comparably investigated. The results show that the phase of aluminide coatings was Fe〈sub〉24〈/sub〉Al〈sub〉76.8〈/sub〉. With the increase of Y〈sub〉2〈/sub〉O〈sub〉3〈/sub〉 content in the pack mixtures, the thickness of aluminide coatings decreased but the cyclic-oxidation resistance at 900 °C in air increased, because of prevention of cavities at the alumina scale/coating interface, and because of mitigation of degradation of the aluminide coating due to decreased outward diffusion and inward interdiffusion between the aluminide and the 309 stainless base. The reasons for the results are discussed.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: December 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Vacuum, Volume 158〈/p〉 〈p〉Author(s): Yu Liu, Zhao Zhang, Guangqiang Li, Yang Wu, Deming Xu, Baokuan Li〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In this study, five types of CaF〈sub〉2〈/sub〉〈img src="https://sdfestaticassets-eu-west-1.sciencedirectassets.com/shared-assets/16/entities/sbnd"〉CaO〈img src="https://sdfestaticassets-eu-west-1.sciencedirectassets.com/shared-assets/16/entities/sbnd"〉Al〈sub〉2〈/sub〉O〈sub〉3〈/sub〉 slags with varying CaO/Al〈sub〉2〈/sub〉O〈sub〉3〈/sub〉 mass ratio and CaF〈sub〉2〈/sub〉 content were selected for investigating the vaporization behavior of slag bearing high CaF〈sub〉2〈/sub〉 content by thermo gravimetry and ion and molecule coexistence theory. The results show that the volatile product of slag is the AlF〈sub〉3〈/sub〉. The vaporization rate is affected by the vapor pressure of AlF〈sub〉3〈/sub〉, mole number of complex molecules and the viscosity of slag. For all slags, the vaporization rate of slag bearing approximately 70 wt% CaF〈sub〉2〈/sub〉 and 30 wt% Al〈sub〉2〈/sub〉O〈sub〉3〈/sub〉 is the fastest due to the ultra-high vapor pressure of AlF〈sub〉3〈/sub〉. In the test of slags containing 70 wt% CaF〈sub〉2〈/sub〉, vaporization rate firstly decreases, then increases with CaO/Al〈sub〉2〈/sub〉O〈sub〉3〈/sub〉 mass ratio increasing from 0.05 to 1.10 and 2.00. In the case of slags containing same CaO/Al〈sub〉2〈/sub〉O〈sub〉3〈/sub〉 mass ratio, vaporization rate firstly increases, then decreases with CaF〈sub〉2〈/sub〉 content decreasing from 68.9 wt% to 48.1 wt% and 28.7 wt%. Slag T5 bearing approximately 30 wt% CaF〈sub〉2〈/sub〉, 33.9 wt% CaO and 36.1 wt % Al〈sub〉2〈/sub〉O〈sub〉3〈/sub〉 has lower electrical conductivity, slower vaporization rate and larger sulfide capacity, which will be economical, environmentally friendly and suitable for vacuum electroslag remelting.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 28 September 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Vacuum〈/p〉 〈p〉Author(s): Catalina Ciobotaru, Ion Gruia〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The monochromatization-effect of visible light (the M-effect) emitted from electronegative-electropositive gas mixture plasma consists in dramatic reduction the spectrum of electropositive gas to one or a few very intense spectral lines in relation to the other lines. The main generation mechanism of this process is the polar-resonant reaction of three-body. The article presents the influence of the reaction energy defect size on the degree of polarization of quasi-monochrome light emitted by a plasma discharge of a very low radio frequency, at a total pressure of gaseous mixture of about 10〈sup〉3〈/sup〉 Pa. This requirement is correlated with the existence of two other criteria, important for the mentioned effect, namely the emission probability of spectral line and the number of electronegative gas metastable atoms. Recorded data are comparatively analyzed for two situations de facto, with and without application of a magnetic field, leading us to the conclusion that the existence of a magnetic field in plasma increases the degree of polarization of the emitted monochrome light.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: December 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Vacuum, Volume 158〈/p〉 〈p〉Author(s): Y. Wang, Y.T. Zhao, Z.W. Yang, D.P. Wang〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Vacuum brazing was applied to join Al〈sub〉2〈/sub〉O〈sub〉3〈/sub〉 ceramic and pure Nb with two active Ag-based fillers, Ag-Cu-Ti and Ag-Cu-Ti + Mo. The influences of the brazing parameter and the content of Mo particles on the microstructure and mechanical properties of the brazed joint were studied. The typical interfacial structure of Al〈sub〉2〈/sub〉O〈sub〉3〈/sub〉/Nb joint brazed with Ag-Cu-Ti filler metal at 900 °C for 10 min was Al〈sub〉2〈/sub〉O〈sub〉3〈/sub〉/Ti〈sub〉3〈/sub〉(Cu,Al)〈sub〉3〈/sub〉O/TiCu+Ti〈sub〉2〈/sub〉Cu〈sub〉3〈/sub〉+TiCu〈sub〉4〈/sub〉+Ag(s,s)+Cu(s,s)/Nb. In the joints brazed with Mo particle-modified composite filler, the large blocky Ti-Cu compounds disappeared, and a large number of fine phases formed in the brazing seam. The dissolved Mo played a better role in refining the microstructure compared with residual Mo particles. In addition, the finite element method (FEM) calculated results showed that the residual stress peak value of Al〈sub〉2〈/sub〉O〈sub〉3〈/sub〉/Nb brazed joint decreased from 296 MPa to 253 MPa when 8 wt. % Mo particles were added in the composite filler. The shear strength of Al〈sub〉2〈/sub〉O〈sub〉3〈/sub〉/Nb brazed joints could reach up to 203 MPa at 900 °C for 10 min. The joining properties of the Al〈sub〉2〈/sub〉O〈sub〉3〈/sub〉/Nb brazed joint were primarily dependent on the dispersion degree of fine Ti-Cu compounds and the thickness of Ti〈sub〉3〈/sub〉(Cu,Al)〈sub〉3〈/sub〉O reaction layer.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: December 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Vacuum, Volume 158〈/p〉 〈p〉Author(s): Biren Patel, Ranjan K. Pati, Indrajit Mukhopadhyay, Abhijit Ray〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Cu〈sub〉2〈/sub〉SnS〈sub〉3〈/sub〉 thin films have been deposited by using non-vacuum spray pyrolysis technique on soda lime glass substrates from single aqueous solution containing all the constituents. The effect of post deposition annealing of the Cu〈sub〉2〈/sub〉SnS〈sub〉3〈/sub〉 thin films on the composition, structural, optical and electrical properties has been studied. The XRD study reveals that vacuum annealing of the thin film gives rise to the evolution of Cu〈sub〉x〈/sub〉S〈sub〉y〈/sub〉 secondary phases by the loss of elemental tin, while the annealing held at sulphur atmosphere increases the crystallinity of the film without giving rise to any secondary phases. The Cu〈sub〉2〈/sub〉SnS〈sub〉3〈/sub〉 phase with preferred orientation along the (112) crystal direction grew to greater extent upon sulphur annealing associated with an improvement in the optical band gap. From the Raman analysis it was observed that as-deposited films are dominated by the presence of tetragonal crystal symmetry of the Cu〈sub〉2〈/sub〉SnS〈sub〉3〈/sub〉 phase. Upon vacuum annealing the peak appearing at 474 cm〈sup〉−1〈/sup〉 grows to greater extent which corresponds to CuS phase, and is in good agreement with the XRD spectra. Eventually its sulphur annealing gives the pure phase of Cu〈sub〉2〈/sub〉SnS〈sub〉3〈/sub〉 with dominating tetragonal crystal structure.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: December 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Vacuum, Volume 158〈/p〉 〈p〉Author(s): Andrey V. Kaziev〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The properties of cathode sheath in a non-sputtering magnetron discharge are discussed involving the theoretical assumptions based on the classical glow discharge description, and magnetron specific effects. It is shown that in a wide range of experimental conditions (gas pressure 〈em〉p〈/em〉 from 1 to 100 Pa, discharge current 〈em〉I〈/em〉〈sub〉d〈/sub〉 from 10 to 1500 A), the trends for principal plasma parameters (electron density 〈em〉n〈/em〉 and temperature 〈em〉T〈/em〉〈sub〉e〈/sub〉) remain the same. Nevertheless, there is crucial difference in dominant supply of electrons between low pressure and elevated pressure non-sputtering magnetron regimes. Both secondary electron emission at low pressures and thermal ionization at high pressures result in sufficiently high electron source for sustaining dense non-sputtering magnetron plasmas at characteristically low voltage 〈em〉V〈/em〉〈sub〉d〈/sub〉 ∼ 80–120 V.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: January 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Vacuum, Volume 159〈/p〉 〈p〉Author(s): Tuo Ye, Yuanzhi Wu, Anmin Liu, Congchang Xu, Luoxing Li〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The dynamic impact tests were performed on 6063 alloy with different initial aging conditions of under-aged (UA), peak-aged (PA) and over-aged (OA) at different strain rates ranging from 1 × 10〈sup〉3〈/sup〉 to 5 × 10〈sup〉3〈/sup〉 s〈sup〉−1〈/sup〉 by split Hopkinson pressure bar. The results show that dynamic deformation behavior is affected by initial aging condition, as well as strain rate. The PA alloy exhibits the highest flow stress and strain rate sensitivity (SRS), while the UA alloy displays the lowest flow stress and SRS. The dislocation and precipitate evolution were analyzed by TEM observations. During high strain rate deformation, the density of the dislocation increases with strain rate, the GP zones in the UA alloy are almost dissolved into the matrix, the number density of the 〈em〉β′′〈/em〉 precipitates in the PA alloy decreases with increasing strain rate due to the dynamic dissolution. The impact deformation results in a great energy differences between precipitates and matrix, precipitates dissolution occurs in order to balance the disrupted thermodynamic equilibrium. The dynamic evolution of the precipitates has a great effect on the mechanical property of the impacted 6063 alloy, it is necessary to consider the microstructure evolution in material selection and structure design.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: January 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Vacuum, Volume 159〈/p〉 〈p〉Author(s): Jie Hu, Liang Zhang, Benqian Lu, Xueqian Wang, Hao Huang〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉A new type of photocatalyst by the dispersion of LaMnO〈sub〉3〈/sub〉 nanoparticles on N doped porous biocarbon using a simple sol-gel method without adding any nitrogen source (such as NH〈sub〉3〈/sub〉, NH4OH, N〈sub〉2〈/sub〉H〈sub〉4〈/sub〉). Biochar is obtained from soybean dregs through two methods of hydrolysis and pyrolysis. The results show that the biocar obtained by two-step pyrolysis method is a better choice. The samples are characterized by field-emission scanning electron microscopy (FE-SEM), Raman spectroscopy, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), photoluminescence analysis, Brunauer-Emmett-Teller surface area analysis (BET) and UV-vis diffuse spectroscopy. It clearly demonstrates that composite exhibit an excellent photocatalytic activity in the degradation of Direct Green BE under UV-vis light because of its larger specific surface area, more active sites, improved charge separation efficiency and enhanced visible harvest ability. Furthermore, three typical N-bonding configurations in porous carbon is efficient for the enhanced photocatalytic activity, the h〈sup〉+〈/sup〉 and •O〈sub〉2〈/sub〉〈sup〉−〈/sup〉 play main roles in the photocatalytic system.〈/p〉〈/div〉 〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉The mechanism that occurs in the LaMnO〈sub〉3〈/sub〉/N doped porous carbon during photocatalytic process is shown in the figure. N substitution at “regular” C sites and can be present of three typical N-bonding configurations such as pyridinic, pyrrolic or graphitic nitrogen. The graphitic N can act as the electron-transfer mediator for the photogenerated electrons. Moreover, the pyridinic N and pyrrolic N at the edges or defects can function as the activation region for the oxygen reduction.〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0042207X18315616-fx1.jpg" width="270" alt="Image 1" title="Image 1"〉〈/figure〉〈/p〉〈/div〉

Description: 〈p〉Publication date: Available online 14 June 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Vacuum〈/p〉 〈p〉Author(s): Ai Momozawa, Rainer Telle〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉This study investigates thermal expansion and thermal vibration behavior of borides using HT-XRD. In the previous research, it has been known that the vibrational behavior directly expresses the behavior of materials at high temperatures. In this work, the high temperature X-ray diffraction (HT-XRD) measurements of TiB〈sub〉2〈/sub〉, W〈sub〉2〈/sub〉B〈sub〉4〈/sub〉, and CrB〈sub〉2〈/sub〉 were conducted at the high temperature ranges; up to 1500 K. From the generated results, the study calculates thermal expansion coefficients, which coincides the previous research. Rather, the study calculates the mean square displacements of borides for evaluating the thermal vibration behaviors at elevated temperatures, demonstrating that: (1) the application of a formula into HT-XRD data could determine Debye-Waller factors of these borides; (2) a term of “agglomeration” could contribute to defining the mean square displacement 〈em〉u〈/em〉〈sup〉2〈/sup〉; (3) both the Debye-Waller factor and the thermal expansion may function to design new boride-based materials at the high temperature; and (4) CrB〈sub〉2〈/sub〉 has a quick increase in mean square displacement and is remarkably large value at elevated temperatures.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: December 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Vacuum, Volume 158〈/p〉 〈p〉Author(s): Shaan Ameer, Kajal Jindal, Savita Sharma, Pradip K. Jha, Monika Tomar, Vinay Gupta〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In this paper, the linear optical response of Cr doped BiFeO〈sub〉3〈/sub〉 (BFCO) using first principles calculations based on the density functional theory (DFT) is reported. The electronic and magnetic properties of BFCO are studied. Cr doping is found to result in an increase in magnetization in BFO. To corroborate the theoretical understanding in BFCO, Cr doped BFO thin film is also deposited via a multistep spin coating technique. The structural and optical characterization of the thin film are performed and the obtained results are compared with the theory.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: February 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Vacuum, Volume 160〈/p〉 〈p〉Author(s): Guoming Zheng, Xiaonan Mao, Lei Li, Rui Dang〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Microstructures and textures determine the mechanical properties of metal materials. In this work, a Ti6242S bar with ϕ260*129 mm scale was selected to study variation of microstructures and textures from edge to center by Optical Microscope and X-Ray Diffraction. Owing to the less plane stress, fast cooling rate and complex flow stress, grains size are quietly fine and macrotextures are close to nearly random in edge, which lead to the most excellent and homogeneous mechanical properties. By comparing feature of microstructure in R/2 and center position, larger volume fraction of α〈sub〉s〈/sub〉 colonies formed in center. Meanwhile, the main texture components were (11〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si3.gif" overflow="scroll"〉〈mrow〉〈mover accent="true"〉〈mn〉2〈/mn〉〈mo〉¯〈/mo〉〈/mover〉〈/mrow〉〈/math〉0) [1〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si4.gif" overflow="scroll"〉〈mrow〉〈mover accent="true"〉〈mn〉1〈/mn〉〈mo〉¯〈/mo〉〈/mover〉〈/mrow〉〈/math〉00] and (11〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si3.gif" overflow="scroll"〉〈mrow〉〈mover accent="true"〉〈mn〉2〈/mn〉〈mo〉¯〈/mo〉〈/mover〉〈/mrow〉〈/math〉0)[0001] in R/2, but symmetrical cubic texture with very high intensity come into being in center. More and larger α〈sub〉s〈/sub〉 colonies combine high-density texture jointly cause tensile strength and yield strength drop dramatically in center. Young's modulus is mainly influenced by textures, due to different texture in different location, edge was the largest, following by the center and R/2. The spheroidization of α〈sub〉p〈/sub〉 laths was completed in edge by strain-induced but dynamic recrystallization in R/2 and center by analyzing grain boundary feature and misorientation of EBSD data.〈/p〉〈/div〉 〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉In this work, three specimens were selected and labeled by S1, S2 and S3 which corresponding (a), (b) and (c) in images. The relationship among microstructure, macrotextures and mechanical properties can be concluded that (1) in side, both α〈sub〉p〈/sub〉 and α〈sub〉s〈/sub〉 grains are fine and macrotextures are close to random texture, which lead to the highest and homogeneous mechanical properties; (2) in R/2, most of grains are equixaial α〈sub〉p〈/sub〉 and (〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si1.gif" overflow="scroll"〉〈mrow〉〈mn〉11〈/mn〉〈mrow〉〈mover accent="true"〉〈mn〉2〈/mn〉〈mo〉¯〈/mo〉〈/mover〉〈/mrow〉〈mn〉0〈/mn〉〈/mrow〉〈/math〉) [〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si2.gif" overflow="scroll"〉〈mrow〉〈mn〉1〈/mn〉〈mrow〉〈mover accent="true"〉〈mn〉1〈/mn〉〈mo〉¯〈/mo〉〈/mover〉〈/mrow〉〈mn〉00〈/mn〉〈/mrow〉〈/math〉] texture was come into being, so a good match between strength and ductility are gained; (3) in center, the width of α〈sub〉s〈/sub〉 grains is about two times of R/2 and with more larger α〈sub〉s〈/sub〉 colonies, the size of α〈sub〉p〈/sub〉 is similar to R/2 but smaller volume fraction. In addition, symmetrical cubic texture with maximum intensity of 7.9 times random is formed, which combine to led to tensile and yield strength drop quickly.〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0042207X18316567-fx1.jpg" width="500" alt="Image 1" title="Image 1"〉〈/figure〉〈/p〉〈/div〉

Description: 〈p〉Publication date: Available online 1 August 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Vacuum〈/p〉 〈p〉Author(s): Yung-An Chan, Georg Herdrich〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Characterization of IEC tight jet mode is achieved through Faraday probe measurements. Preliminary results indicate that the tight jet is a highly energetic electron beam with scattering of secondary ions and electrons, which result from electron beam impact ionization. A novel analytical model is proposed to evaluate this non-Maxwellian plasma beam, including a compensation of the secondary electron emission effect on the probe's surface. The results show prominent features on the extracted jet's kinetic energy and the respective (electron) current of IEC. In addition, they demonstrate a practical method to characterise non-Maxwellian plasma jets through Faraday probes.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: January 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Vacuum, Volume 159〈/p〉 〈p〉Author(s): Mo-Lin Su, Jia-Ning Li, Ke-Gao Liu, Wen-Jun Qi, Fei Weng, Yuan-Bin Zhang, Ji-Shuai Li〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Vacuum electron beam welding (EBW) was used to weld the thick TA1 titanium alloy sheets. Test results indicated that the coarse serrated-shape α and needle-shape α′ grains were observed in weld zone (WZ); the heat affected zone (HAZ) near the weld center consisted of α and α′ gains; the tensile strength of the TA1 joint was 344 MPa, which was significantly higher than that of the base metal (BM); the fracture of the tensile samples with different penetration depths all occurred on BM, the tensile property of the upper-bottom joint was better than that of the middle joint; moreover, lots of dimples can be observed on the fatigue fracture surface, exhibiting the characterization of the ductile fracture.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: January 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Vacuum, Volume 159〈/p〉 〈p〉Author(s): Denize Kalempa, Felix Sharipov, Júlio Conti Silva〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Sound waves due to vibro-thermal excitation propagating through a binary mixture of rarefied gases in a gap between source and receptor are investigated by applying the McCormack model to the Boltzmann equation. The sound waves are induced by mechanical vibration and temperature variation of one plate, while the other plate being fixed at a constant temperature, acts as a receptor of sound waves. The oscillatory gas mixture flow is considered as fully established and all its macroscopic quantities depend on time harmonically. The discrete velocity method is used to solve the coupled kinetic equations in wide ranges of both rarefaction and oscillation parameters. The former is defined as the ratio of the distance between the plates to the equivalent free path, while the latter is the ratio of the intermolecular collision frequency to sound frequency. Analytical solutions in the free molecular and hydrodynamic regimes have been obtained too. Two mixtures, namely, Helium〈img src="https://sdfestaticassets-eu-west-1.sciencedirectassets.com/shared-assets/16/entities/sbnd"〉Argon and Helium〈img src="https://sdfestaticassets-eu-west-1.sciencedirectassets.com/shared-assets/16/entities/sbnd"〉Xenon, are considered with a molar fraction equal to 0.1, 0.5 and 0.9. The amplitudes and phases of all macroscopic characteristics of the gas mixture flow are calculated as functions of the rarefaction and oscillation parameters so that the free molecular, transitional and hydrodynamic regimes are covered. The results are compared to those obtained in the limit of a single gas in order to investigate the influence of the molar fraction and molecular masses of species on the problem solution. The reciprocal relations between cross phenomena are obtained and verified numerically.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: December 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Vacuum, Volume 158〈/p〉 〈p〉Author(s): Sunil Kumar, Vishal Sharma, P.K. Diwan〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The energy loss straggling of 5.486 MeV α-particles in Tb, Ta and Au metallic foils (varying thicknesses ∼4.20–16.00 mg/cm〈sup〉2〈/sup〉) is measured, in the fractional energy loss limits (ΔE/E %) ∼20–85, using transmission technique. These measured straggling values are compared with the predicted values based on Bohr, Lindhard and Scharff, Bethe and Livingston, Yang et al. and Titeica analytical straggling formulas. The present comparison reveals that the prediction of Titeica straggling formula shows better agreement with the measured values as compared to other considered straggling formulas. Here, Titeica formula based predicted values show generally ∼0.60–1.30 times deviation with the presently measured straggling values.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: December 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Vacuum, Volume 158〈/p〉 〈p〉Author(s): Tong Zhao, Wangcan Cai, Marius Dahmen, Jonathan Schaible, Chen Hong, Andres Gasser, Andreas Weisheit, Tim Biermann, Ingomar Kelbassa, Han Zhang, Dongdong Gu, Johannes Henrich Schleifenbaum〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The use of aluminium alloys containing Sc and Zr in additive manufacturing (AM) provides new solutions for lightweight design. Representative thin-wall structured parts were additively fabricated with a commercially available Al-4.55Mg-0.51Mn-0.65Sc-0.30Zr alloy in Laser Metal Deposition (LMD) process. A bi-directional and a uni-directional scan strategy were applied and laser power from 500 W to 600 W was used. Nanohardness tests were conducted on specimens aged at 300 °C for up to 19 h to observe the ageing responses. Fine-grained microstructures with few micro-sized precipitates containing Sc- and Zr were found in the last track of every specimen. The area formed by the track-overlapping was the opposite, but an apparent hardening was observed only after the ageing. AM-processes with local remelting are facing the challenge to exert the potential strengthening effect of aluminium alloys containing Sc. The mushy state must be suppressed to prevent the waste of the expensive rare elements.〈/p〉〈/div〉 〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0042207X18309187-fx1.jpg" width="500" alt="Image 1" title="Image 1"〉〈/figure〉〈/p〉〈/div〉

Description: 〈p〉Publication date: December 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Vacuum, Volume 158〈/p〉 〈p〉Author(s): Chander Prakash, Sunpreet Singh, Manjeet Singh, Kartikey Verma, Babulal Chaudhary, Subhash Singh〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The present research work is aimed to discuss a novel method of depositing hydroxyapatite coats, with interconnected pores, on the surface of bio-degradable Mg〈img src="https://sdfestaticassets-eu-west-1.sciencedirectassets.com/shared-assets/16/entities/sbnd"〉Zn〈img src="https://sdfestaticassets-eu-west-1.sciencedirectassets.com/shared-assets/16/entities/sbnd"〉Mn alloy by using hydxroxyapatite (HA) powder mixed electric discharge machining (HAM-EDM) process. The parameters of HAM-EDM process has been optimized using multi-objective particle swarm optimization (MO-PSO) technique to determine the optimal levels of concentration of hydroxyapatite powder (C〈sub〉HA〈/sub〉), peak-current (I〈sub〉p〈/sub〉), pulse-on (T〈sub〉on〈/sub〉), and pulse-off (T〈sub〉off〈/sub〉). The surface roughness (S〈sub〉R〈/sub〉), thickness of recast layer (R〈sub〉LT〈/sub〉), and micro-hardness (M〈sub〉H〈/sub〉) were chosen as output response characteristics. The experiments were performed according to L〈sub〉27〈/sub〉 orthogonal array and an empirical model has been developed to interpret the co-relation amongst input and output parameters. A number of optimal solutions (∼100) were obtained by MO-PSO technique, where all responses were optimized. Among them, best optimal condition is to deposit biomimetic HA-containing layer with low SR (0.70 μm), low RLT (11.85 μm) and high MH (246 HV) was C〈sub〉HA〈/sub〉 = 5.28 g/l, I〈sub〉p〈/sub〉 = 3.48 A, T〈sub〉on〈/sub〉 = 40.33 μs, and T〈sub〉off〈/sub〉 = 109.29 μs? Further, the specimens produced were characterized, morphologically and topologically, and revealed the existence of hydroxyapatite (HA) layer with interconnected pores of 5–10 μm size. The EDS spectrum showed that presence of Ca, P, and O on the modified surface, which conferred the deposition of HA-layer on the surface. The XRD pattern investigations of modified surface confirmed the formation of various biocompatible phases, which enhanced the mechanical properties, corrosion and osseintegration characteristics.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 13 April 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Vacuum〈/p〉 〈p〉Author(s): Refat El-Sheikhy, Akira Kobayashi〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉 〈p〉Observations on fracture and crack bifurcation phenomenon of plasma spray Zr coating is studied in current paper with new understanding based on new recognized information.〈/p〉 〈p〉A new model is developed for Zr coating layers and cracks. Analytical fundamental characterization is carried out regarding mechanism under high thermal stresses on outer face with cooling back side of the substrate. Results are new such as crack branches at 120°, layered cracks, stepped crack surface and variable crack width. The zirconia coating has hexahedral shape as a honeycomb microstructure. Due to effect of heating-cooling, the first coating layer and near layers to substrate surface of zirconia coating will be contracted or do not be expanded while outside coating layers will be extended producing bi-interfacial de-bonding between particles and propagation to other crystals producing cracks and branching. Depth and width of the crack will be extended and increased in the coating layers producing stepped and layered cracks with branches. Propagation angles of branches are always 60°. Cracking load will be maximum at main crack orientation angle of β = 45° for equal stresses in both X and Y directions while for β〈30, β〉60 cracking load will be minimized meaning that crack will carry high stresses at 30〉β 〉 60.〈/p〉 〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 12 June 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Vacuum〈/p〉 〈p〉Author(s): Akira Kobayashi〈/p〉

Description: 〈p〉Publication date: December 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Vacuum, Volume 158〈/p〉 〈p〉Author(s): Ayushi Paliwal, Monika Tomar, Vinay Gupta〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Surface Plasmon Resonance (SPR) technique has been used in the present work to study the optical properties of pulsed laser deposited single phase BiFeO〈sub〉3〈/sub〉, Mn doped BiFeO〈sub〉3〈/sub〉 (BFMO) and Ce doped BiFeO〈sub〉3〈/sub〉 (BCFO) thin films. Refractive index dispersion studies with varying incident wavelengths has also been studied. Magnetic field dependence on the optical properties of BFMO thin films have also been determined using SPR. A very high sensitivity of 147°/Tesla was found for the prism/Au/BFMO structure exhibiting maximum change in optical properties with magnetic field indicating the potential use of BFMO thin films for the realization of efficient optical sensor.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: January 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Vacuum, Volume 159〈/p〉 〈p〉Author(s): Bo Gao, Xiaoye Du, Yangyang Liu, Baorui Song, Shuheng Wei, Yanhuai Li, Zhongxiao Song〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉A superhydrophobic titanium dioxide (TiO〈sub〉2〈/sub〉) film with the template of a candle smoked Si wafer was successfully fabricated by magnetron sputtering. The film specimens were examined by X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, contact angle meter, scanning electron microscope (SEM), transmission electron microscope (TEM) and gas-sensitivity tests. The results showed that the TiO〈sub〉2〈/sub〉 solely deposited on the silicon wafer was hydrophilic, with its contact angel only 61°, while it became superhydrophobic with water contact angle up to 155° after depositing on candle smoked substrate. The SEM and TEM results showed that the TiO〈sub〉2〈/sub〉 morphology kept the spongy-like framework covering on the carbon clusters formed template. In this paper, the superhydrophobic TiO〈sub〉2〈/sub〉 was achieved on the candle soot without modification by low surface energy materials, which shows the dominance of the structure for preparing hydrophobic TiO〈sub〉2〈/sub〉 films. The TiO〈sub〉2〈/sub〉 films deposited on the candle soot more excellent gas sensitivity than pure TiO〈sub〉2〈/sub〉 films.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: December 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Vacuum, Volume 158〈/p〉 〈p〉Author(s): J.B. Mathangi, M. Sadeesh Sharma, B. Mercy Jacquline, M. Helen Kalavathy〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Adsorption technique was employed to reduce the pollutants from the fluid phase. In this research work, Activated Carbon was produced by chemical activation of wood sawdust at different impregnation ratios and the yield, bulk density, methylene blue number, iodine number and pH point of zero charges were determined. The S〈sub〉BET〈/sub〉 for AC3H was found to be 797.73 m〈sup〉2〈/sup〉 g〈sup〉−1〈/sup〉. Batch adsorption for the removal of nickel was carried out to perform the isotherm and kinetic study by varying parameters such as contact time, initial metal ion concentration, carbon dosage and temperature. The maximum adsorption capacity of Ni〈sup〉2+〈/sup〉 onto adsorbent was 16.47 mg g〈sup〉−1〈/sup〉. The fixed bed adsorption was performed for parameters such as particle size of 1.7 mm, 1.4 mm & 0.6 mm and flow rate of 50 mL min〈sup〉−1〈/sup〉, 70 mL min〈sup〉−1〈/sup〉 and 90 mL min〈sup〉−1〈/sup〉 which in turn indicated favorable column dynamics and its CO〈sub〉2〈/sub〉 adsorptive behavior. The maximum equilibrium adsorption capacity for CO〈sub〉2〈/sub〉 adsorption obtained was 0.96 mol kg〈sup〉−1〈/sup〉 for the flow rate of 90 mL min〈sup〉−1〈/sup〉 and a particle size of 0.6 mm. Kinetic and dynamic models were fitted with the experimental data and the adsorption constants were determined.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 27 August 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Vacuum〈/p〉 〈p〉Author(s): Amodini Mishra〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In the present work, magnetite (Fe〈sub〉3〈/sub〉O〈sub〉4〈/sub〉) nanoparticles decorated graphene oxide (GO) sheets were synthesized using the chemical method. Graphene based nanocomposites show an effective adsorbent property, and therefore can be used as an organic pollutant remover from the aqueous medium. The X-ray diffraction analysis was done to investigate the crystallinity and particle size of Fe〈sub〉3〈/sub〉O〈sub〉4〈/sub〉 decorated GO sheets and the particle size was found to be 28 nm. Surface morphology of Fe〈sub〉3〈/sub〉O〈sub〉4〈/sub〉@GO nanocomposites was studied using transmission electron microscopy and the obtained inter planer spacing in Fe〈sub〉3〈/sub〉O〈sub〉4〈/sub〉@GO nanocomposites was 0.246 nm. For the applications point of view, these nanocomposites have been used for the removal of Rhodamine 6G dye molecules from the aqueous medium. The removal capacity was found to increase as the concentration of the nanocomposite increases. In Fe〈sub〉3〈/sub〉O〈sub〉4〈/sub〉@GO nanocomposites the GO sheets provide large surface area due to different functional groups like epoxide (C-O-C), carboxylic acid (-COOH), hydroxyl (-OH) to adsorb dye molecules. This study provides a new platform for the use of Fe〈sub〉3〈/sub〉O〈sub〉4〈/sub〉@GO nanocomposites in a water clean-up process.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: January 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Vacuum, Volume 159〈/p〉 〈p〉Author(s): Yanfei Pan, Bo Liu, Huixiang Hu, Haodong Jiang, Feng Wei, Min Zhou, Xinyan Fan, Haibiao Yu, Gengwu Niu, Jintian Huang〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The rod-shaped Ni-NiO/TiO〈sub〉2〈/sub〉 hollow composite structure based on metallization cellulose fibers and Titanium butoxide (TBOT) via Sol-Gel method was fabricated to obtain a highly active rod-shaped hollow catalysts. The results showed that the high-heat treatment had no obvious influence on the hollow structure cavity size and the ideal surface roughness value of hollow structure was 6.385 μm. The XRD patterns revealed that the Ni and TiO〈sub〉2〈/sub〉 particles that had been deposited on cellulose fibers had a crystallite size structure between 16.5 and 19.4 nm. The characteristic absorption peak at 1035 cm〈sup〉−1〈/sup〉 assigned to Ti-O-C of anatase nano-TiO〈sub〉2〈/sub〉 on hollow structure surface appeared. It is feasible to control the crystallite size and hollow cavity pore size via Sol-Gel method. The magnetic hollow structure shown here can be applied as catalysts and it can be completely natural subsidence within 5 min. Herein, the catalytic capacity of the rod-shaped Ni-NiO/TiO〈sub〉2〈/sub〉 hollow composite structure for Cu (II) was found to be 5696 mg g〈sup〉−1〈/sup〉.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: January 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Vacuum, Volume 159〈/p〉 〈p〉Author(s): Ben D. Beake, Adrian J. Harris〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉It is important to measure nanomechanical properties of materials for extreme environments at temperatures that match their operating conditions so that the data are more relevant than those obtained from room temperature measurements. Reliable high temperature mechanical property data improves our understanding of the linkage between the small-scale mechanical behaviour and the performance and design of advanced materials systems for increasingly extreme environments. Accurate high temperature nanomechanical measurements require significantly more careful instrumental and experimental design than at room temperature. It is important to consider (i) instrumental stability and thermal drift (ii) the test environment and its influence on the stability of the indenter and sample (iii) modifications to the experimental load history and analysis procedures to minimise the effect of greater time-dependency. In this review of best practice and published studies effective strategies for mitigating these effects and achieving reliable, validated data are discussed with illustrative examples on thin films and bulk materials operating in extreme environments in applications in the nuclear, aerospace, fuel cell and cutting tool industries to 1000 °C.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: December 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Vacuum, Volume 158〈/p〉 〈p〉Author(s): Jiankun Qin, Xiaowan Li, Yali Shao, Kaixin Shi, Xin Zhao, Tianshi Feng, Yingcheng Hu〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Transparent wood is an environmentally friendly material that could be used as building materials or substrates for solar cells to reduced electrical energy consumption. Many problems remain in the delignification process, such as energy consumption and gas pollution. In this paper, the optimum conditions for two stage delignification of low density balsa wood (〈em〉Ochroma pyramidale〈/em〉) and high density of basswood (〈em〉Tilia tuan〈/em〉) were studied. The optimized single layer transparent wood was laminated to produce transparent wood with high thickness. The results showed that the lamination method cut the delignification time in half and improved the dimensional stability of the transparent wood. Optical testing showed that the maximum transmittance of the same direction laminated transparent wood was similar to the single layer transparent wood with the same thickness. The mechanical experiments showed that the transparent basswood had a better tensile strength, which reached 75.12 MPa. Optimizing the process of the transparent wood could greatly reduce the preparation time and the energy consumption, so that mass production of enterprises could become a reality.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: December 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Vacuum, Volume 158〈/p〉 〈p〉Author(s): Jing Wang, Junping Zhang, Ruosong Chen, Cheng Yang, Lan Xiang, Meigui Yi〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Porous MgO nanoplates with high surface area has been synthesized by a vacuum calcination route using industrially available Mg(OH)〈sub〉2〈/sub〉 as the precursor. The vacuum calcination not only promoted the phase transformation of Mg(OH)〈sub〉2〈/sub〉 to MgO at a low temperature (300 °C), but also inhibited the thermally-induced particle growth and pore coalescence, leading to the formation of MgO nanoplates with fine grain sizes (5.5 nm), ultrasmall pores (2–4 nm) and high surface area (390 m〈sup〉2〈/sup〉 g〈sup〉−1〈/sup〉). The as prepared MgO nanoplates exhibited superior arsenic adsorption properties with a maximum adsorption capacity of 481.0 mg g〈sup〉−1〈/sup〉, as well as excellent catalytic activity for the Claisen-Schmidt condensation reaction.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: December 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Vacuum, Volume 158〈/p〉 〈p〉Author(s): Kun Liu, Yajiang Li, Juan Wang〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉TC4 titanium alloy was joined with Ni80Cr20 alloy by vacuum diffusion bonding at 950 °C without interlayer. Results indicate that interfacial reaction layer is composed of TiNi, Ti〈sub〉2〈/sub〉Ni, Ti(Ni, Cr)〈sub〉3〈/sub〉+Cr〈sub〉ss〈/sub〉, and Ti(Al, Ni)〈sub〉s〈/sub〉. A higher diffusion rate of Ni than Ti caused the segregation of Ni element across the interface which induced the formation of Ni-poor area near Ni80Cr20 side and generated some Kirkendall voids. Moreover, the accumulated Kirkendall voids acted as the source for micro cracks to initiate and propagate along the interface. The maximum shear strength of joints is 55 MPa obtained at the bonding time of 60 min and most joints fractured near Ni80Cr20 side. The interfacial brittle Ti-Ni intermetallic compounds and porous microstructure of Ni80Cr20 as well as the formation of micro cracks near Ni80Cr20 side facilitated the initiation and propagation of cracks during fracture.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: December 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Vacuum, Volume 158〈/p〉 〈p〉Author(s): Hongbo Ju, Ning Ding, Junhua Xu, Lihua Yu, Yaoxiang Geng, Guo Yi, Tianyao Wei〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Niobium nitride and copper (NbN-Cu) composite films with different copper content (Cu/(Nb+Cu) = 0.6 at.%-24.8 at.%) were deposited using magnetron sputtering, and the microstructure and tribological properties of the films were investigated. The results showed that the films exhibited a mixture phase of face-centered cubic (fcc) NbN, hexagonal close-packed (hcp)NbN and fcc-Cu. The addition of copper below 6.0 at.% dropped both friction coefficient (〈em〉μ〈/em〉) and wear rate (〈em〉WR〈/em〉) sharply. A further increase in copper content decreased the 〈em〉μ〈/em〉 furtherly, while the decreasing in 〈em〉μ〈/em〉 took sacrifice of 〈em〉WR.〈/em〉 The addition copper of 6.0 at.% into the niobium nitride matrix could broaden the niobium nitride film's effective service temperature to 400 °C. The lubricating copper (〈200 °C) and the tribo-phases of copper oxide and niobium oxide remained the value of 〈em〉μ〈/em〉 at ∼0.55 regardless of temperatures at the cost of the increase of 〈em〉WR.〈/em〉〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: January 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Vacuum, Volume 159〈/p〉 〈p〉Author(s): Yun Ji, Songyong Liu, Jianping Li〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In this work, the pressure drop and flow characteristics of solid–gas two-phase flow in a horizontal pipe were investigated experimentally. The pressure drop was measured by pressure transmitters, and the particle flow behaviour was observed using a high-speed camera. The particle concentration and gas pressure drop were systematically compared under different supply standard air fluxes. It was found that the particle materials exhibited a dune flow at a lower airflow velocity, and the pressure drop decreased first and then increased with increasing supply airflow velocity, until the critical wind speed for spraying materials was achieved. The coefficient of variation and power spectral density (PSD) analysis of the pressure drop were introduced to study the flow stability in pneumatic conveying; the fluid flow stability increased with decreasing coefficient of variation, and the results of the PSD analysis were consistent with those of the flow characteristics and pressure drop. When the standard airflow velocity exceeded the critical wind speed, the solid–gas ratio had a slight impact on the flow stability, and the optimum supply pressure for pneumatic conveying of these spraying materials was 0.4 MPa.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: December 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Vacuum, Volume 158〈/p〉 〈p〉Author(s): A.V. Voitsekhovskii, S.N. Nesmelov, S.M. Dzyadukh, V.S. Varavin, S.A. Dvoretsky, N.N. Mikhailov, M.V. Yakushev, G.Y. Sidorov〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The electrical properties of MIS structures based on graded band gap Hg〈sub〉0.77〈/sub〉Cd〈sub〉0.23〈/sub〉Te grown by the molecular beam epitaxy method with the Al〈sub〉2〈/sub〉O〈sub〉3〈/sub〉 dielectric formed by the plasma enhanced atomic layer deposition method were investigated. It is established that for such structures the recharge of slow states takes place and significantly distorts the form of the capacitance-voltage (C-V) characteristics. A technique is proposed for constructing the C-V curves of HgCdTe MIS structures, which makes it possible to eliminate the effect of slow surface states. It is shown that Al〈sub〉2〈/sub〉O〈sub〉3〈/sub〉 films are suitable for passivation of infrared detectors due to small flat band voltages leading to the realization of the depletion or weak inversion modes. The hysteresis of electrical characteristics is eliminated when an intermediate CdTe layer with a thickness of about 0.2 μm is grown in situ during the epitaxial growth.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: December 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Vacuum, Volume 158〈/p〉 〈p〉Author(s): Jing Li, Jianzhong Zhou, Aixin Feng, Yunjie Sun, Yu Huang, Xuliang Tian, Shu Huang, Xiankai Meng〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The microstructural response and tensile properties on 2024-T351 aluminum alloy specimens induced by cryogenic laser peening were investigated. The microstructure behaviors were characterized by transmission electron microscopic examination and electron backscattered diffraction analysis. Tensile properties tests at room temperature were also performed. The experimental results cleared that compared with room temperature laser peening, cryogenic laser peening can induce higher-density of dislocation and smaller-size grain, while the strength and plasticity of the processed 2024-T351 aluminum alloy were simultaneously increased. The analysis results suggested that the more excellent tensile properties were attributed to the more beneficial microstructural evolution induced by cryogenic laser peening.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: December 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Vacuum, Volume 158〈/p〉 〈p〉Author(s): Savita Sharma, Monika Tomar, Vinay Gupta〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Present work reports the photovoltaic (PV) effect in different metal top electrodes decorated multiferroic BFO thin films. Polycrystalline BFO thin film has been deposited on Platinum (Pt) coated silicon substrates successfully through Pulsed laser deposition (PLD) technique. Different Metal top electrodes (Au, Cu, Ag, and Al) of 200 μm diameter were deposited on BFO thin films using thermal evaporation technique and their influence on ferroelectric and photovoltaic properties including J〈sub〉sc〈/sub〉 -short circuit current, V〈sub〉oc〈/sub〉 -open circuit voltage and I〈sub〉on〈/sub〉/I〈sub〉off〈/sub〉 has been investigated. Variation in photovoltaic properties with different metal contacts has been related to the leakage current and ferroelectric polarization. Au/BFO/Pt structure exhibited improved ferroelectric properties with enhanced saturation polarization of P〈sub〉s〈/sub〉 = 33.53 μC/Cm〈sup〉2〈/sup〉 along with remnant polarization of P〈sub〉r〈/sub〉 = 19.34 μC/Cm〈sup〉2〈/sup〉 as compared to other structures. The open circuit voltage and short circuit photocurrent density were found to be −1.09 V and 11.73 mA/cm〈sup〉2〈/sup〉 respectively. The elevated ferroelectric photovoltaic response obtained in current work may be accredited to the existing substantial depolarization field as a result of superior remnant polarization.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: January 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Vacuum, Volume 159〈/p〉 〈p〉Author(s): Jinxuan Cheng, Xiaowu Hu, Xiongxin Jiang〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉This paper described microstructure evolution of interfacial intermetallic compound (IMC) layers in a series of Sn-37Pb/Cu-Co systems (the different amount of Co additions was a variable in this experiment, and we represented it with Cu-〈em〉x〈/em〉Co in the rest of this article). With the same aging temperature (150 °C), the addition of Co significantly influenced the interfacial reaction between Sn-37 Pb solder and Cu-Co substrate. Through analyses of these changes, we found that Co addition was an important strategy to control IMC thickness and improve the interfacial wettability. Additionally, correlations between the thickness of IMC layers and aging time were established, and successfully fitted into linear functions, and this relationship corresponded to the characteristics of growth mechanism controlled by volume diffusion. Unfortunately, Kirkendall voids and microcracks were still inevitable in the current study, which could severely degrade the performance of solder joint, so further methods to improve these defects need to be explored.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: February 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Vacuum, Volume 160〈/p〉 〈p〉Author(s): Fenglong Li, Xue Gu, Kun Zhang, Tat Thang Nguyen, Minghui Guo〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Sustainable nanofibrillated cellulose (NFC) -based composites as advanced functional materials have attracted considerable attention for using in soft wearable electronic devices. In this work, a controllable one-pot method to fabricate NFC/g-C〈sub〉3〈/sub〉N〈sub〉4〈/sub〉 composite film with different content of graphite carbon nitride (g-C〈sub〉3〈/sub〉N〈sub〉4〈/sub〉) via vacuum-induced self-assembly (VISA) process has been presented. The composite film was constructed by electrostatic interaction/hydrogen bonding between NFC and g-C〈sub〉3〈/sub〉N〈sub〉4〈/sub〉 coupled with vacuum-assisted filtration. The results demonstrated that the obtained NFC/g-C〈sub〉3〈/sub〉N〈sub〉4〈/sub〉 composite film exhibited better specific capacitance. The high specific capacitance of 51 F g〈sup〉−1〈/sup〉 at 1 mA cm〈sup〉−2〈/sup〉 and 46 F g〈sup〉−1〈/sup〉 at 1 mA cm〈sup〉−2〈/sup〉 are achieved. The study provides a straightforward method of fabricating freestanding film as supercapacitor electrode, which have the potential in soft wearable electronic devices.〈/p〉〈/div〉 〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0042207X18312739-fx1.jpg" width="305" alt="Image 1" title="Image 1"〉〈/figure〉〈/p〉〈/div〉

Description: 〈p〉Publication date: Available online 1 August 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Vacuum〈/p〉 〈p〉Author(s): Seiya Tanaka, Shin Yamada, Ryota Soga, Kimiya Komurasaki, Rei Kawashima, Hiroyuki Koizumi〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Aiming at development of a new method of alumina reduction that is useful for ore mined from the moon, experiments of alumina reduction using CW laser ablation were conducted with a kW-class CW CO〈sub〉2〈/sub〉 laser with 400–2000 W power. After a laser beam was focused on a sintered alumina rod, the surface was heated to a temperature necessary for ablation of alumina. Ambient pressure in the test chamber was controlled by supplying Ar gas at 0–0.30 atm, 0.50 atm and 1.0 atm initially, with gas evacuated using a rotary vacuum pump. Under those conditions, an ablation plume was ejected continuously from the sintered alumina rod surface, which was not observed in vacuum. Ambient pressure was increased to 0.40 atm, 0.65 atm, and 1.2 atm. Moreover, emission spectra from the ablation plume were measured; Al I line spectra were detected. Results show that alumina reduction occurred without reducing stores. The equilibrium temperature varied with ambient pressure and laser intensity: 3100–3700 K. Molar reduction of 9.7% and energy conversion efficiency of 0.64% were achieved. Further improvement of the molar reduction percentage can be achieved using increased laser intensity and ambient pressure.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: January 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Vacuum, Volume 159〈/p〉 〈p〉Author(s): Eunji Jun〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Fokker-Planck kinetic models have been devised as an approximation of the Boltzmann collision operator. Cubic Fokker-Planck-DSMC hybrid method is employed to simulate the diatomic gas flow through a thin slit and a thin orifice. Pressure driven nitrogen expansion gas flows with two different pressure ratios are investigated at Knudsen number 0.001. The DSMC method is physically accurate for all flow regime; however it is computationally expensive in high density or near continuum regions. The Fokker-Planck-DSMC hybrid scheme employs DSMC in rarefied regions and Fokker-Planck method in near continuum flow regions for an efficient and accurate solution. Numerical procedures of the cubic Fokker-Planck method are implemented within the framework of an existing DSMC-solver, SPARTA. The Fokker-Planck-DSMC hybrid solution reproduces pure DSMC solution with improved computational efficiency up to a factor of five for vacuum flow through a thin orifice. In addition, breakdown of translational equilibrium is investigated. Domain criterion of FP-DSMC is safely smaller than Bird's breakdown criterion.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 22 September 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Vacuum〈/p〉 〈p〉Author(s): Junko Yamasaki, Shigeru Yokota, Kohei Shimamura〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Finding alternatives to xenon as a propellant is essential for reducing the launching cost of all-electric satellites and for achieving low-cost electric propulsion, especially using Hall thrusters. Argon is a candidate as such a low-cost propellant, but it has never been used practically owing to its poor performance. We attempted two methods to improve the thruster performance: (1) by mixing xenon in argon propellant and (2) by modifying the thruster structure for the argon propellant. Modifying the thruster structure yielded an increase in the specific impulse from 482 to 1500 s using pure argon. Also, when we used an argon-xenon mixture gas as propellant, the thruster performance increased under argon-rich conditions using the modified thruster.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: January 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Vacuum, Volume 159〈/p〉 〈p〉Author(s): Jarnail Singh, Vikram Verma, Ravi Kumar〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉We have investigated the structural and optical properties of aluminium substituted chromium oxides (Cr〈sub〉2〈/sub〉O〈sub〉3〈/sub〉) nanoparticles. Pure and Al substituted Cr〈sub〉2〈/sub〉O〈sub〉3〈/sub〉 nanoparticles having various concentrations of Al (i.e. from 1 to 5%), were synthesized using co-precipitation method. The prepared samples were characterized by using X-ray diffraction (XRD), Field emission scanning electron microscopy (FESEM), Raman spectroscopy and UV-VIS spectroscopy techniques. XRD studies demonstrated that Cr〈sub〉2〈/sub〉O〈sub〉3〈/sub〉 exhibit rhombohedral structure and it didn't get affected with Al substitution, which is also complemented by the Raman spectra. FESEM images show that the pure Cr〈sub〉2〈/sub〉O〈sub〉3〈/sub〉 nanoparticles are spherical in shape and transformed into platelets form with Al substitution. UV–Vis study reveals that Al substitution leads to slight decrement in optical band gap of Cr〈sub〉2〈/sub〉O〈sub〉3〈/sub〉. This work leads to the development of highly effective 〈em〉p〈/em〉-type transparent conducting oxide materials.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: December 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Vacuum, Volume 158〈/p〉 〈p〉Author(s): M.C. Nwankwo, A.C. Nwanya, A. Agbogu, A.B.C. Ekwealor, Paul M. Ejikeme, R. Bucher, R.U. Osuji, M. Maaza, Fabian I. Ezema〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In this study, successive ionic layer adsorption and reactions (SILAR), a simple and cost-effective method was used to successfully synthesize Mn〈sub〉3〈/sub〉O〈sub〉4〈/sub〉 thin film electrodes on fluorine-doped tin oxide (FTO) and stainless steel (ss) substrates. The synthesized films were characterized using scanning electron microscopy (SEM), X-Ray diffraction (XRD) and UV–vis–NIR spectroscopy. The electrochemical energy storage behavior of the electrodes was evaluated using cyclic voltammetery (CV), potentiostatic charge-discharge (c-d) technique and electrochemical impedance spectroscopy (EIS) in 1M solution of Na〈sub〉2〈/sub〉SO〈sub〉4〈/sub〉 electrolyte. The highest specific capacitance of 786.2Fg〈sup〉-1〈/sup〉 was obtained at a scan rate of 5 mVs〈sup〉−1〈/sup〉 for the 80-cycle film electrode. The SILAR deposited Mn〈sub〉3〈/sub〉O〈sub〉4〈/sub〉 thin film electrodes is a promising material for pseudocapacitor application based on the electrochemical properties obtained.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 12 May 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Vacuum〈/p〉 〈p〉Author(s): Yoshihiro Oka, Tomoya Kuroshima, Kohei Sawachika, Michiru Yamashita, Mitsumasa Sakao, Keiichiro Ohnishi, Keiichi Asami, Mitsuyasu Yatsuzuka〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉A silver nanocolloidal solution was prepared by a cavitation bubble plasma with a pair of silver rod electrodes in a sodium hydroxide water solution with the initial pH = 11.0. The cavitation bubble plasma was generated by the bipolar high voltage pulses of the repetition rate 200 kHz and the pulse width 0.8 μs in the sodium hydroxide water solution in which many cavitation bubbles produced by a high-speed rotor were feeding. The UV–Vis absorption spectra of the silver nanocolloidal solution exhibited a characteristic peak around 400 nm in wavelength. The silver nanocolloidal solution of 250 mL including silver nanoparticles of median diameter 1.3 nm and concentration 4 ppm was prepared at the processing time 1 min. The particle size in the solution increased with increasing the processing time and grew to 14.6 nm in median diameter at the processing time 20 min. The concentration of particles also increased with increasing the processing time. A TEM image of silver nanoparticles revealed that the particles were spherical crystalline.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: January 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Vacuum, Volume 159〈/p〉 〈p〉Author(s): F. Friedel, C. Röttele, L. Schimpf, J. Wolf, G. Drexlin, M. Hackenjos, A. Jansen, M. Steidl, K. Valerius〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The KArlsruhe TRItium Neutrino experiment (KATRIN) aims to measure the effective electron anti-neutrino mass with an unprecedented sensitivity of 0.2 eV/c〈sup〉2〈/sup〉, using 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si1.gif" overflow="scroll"〉〈mrow〉〈mtext〉β〈/mtext〉〈/mrow〉〈/math〉-electrons from tritium decay. Superconducting magnets will guide the electrons through a vacuum beamline from the windowless gaseous tritium source through differential and cryogenic pumping sections to a high resolution spectrometer. At the same time tritium gas has to be prevented from entering the spectrometer. Therefore, the pumping sections have to reduce the tritium flow by at least 14 orders of magnitude. This paper describes various simulation methods in the molecular flow regime used to determine the expected gas flow reduction in the pumping sections for deuterium (commissioning runs) and for radioactive tritium. Simulations with MolFlow+ and with an analytical model are compared with each other, and with the stringent requirements of the KATRIN experiment.〈/p〉〈/div〉 〈/div〉