YANG Jilian ZHANG Baisheng JIN Lan DING Yongfan YE Chuntang Institute of Atomic Energy
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Beijing
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ChinaYANG Yingchang SUN Hong KONG Linshu Peking University
,
Beijing
,
China YANG Jilian
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Associate Professor
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P.O.Box 275
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Sub 80
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Beijing 102413
,
China
金属学报(英文版)
The site occupancies in permanent magnetic alloy Y_2(Fe_(0.95)Al_(0.05))_(14)B has been studied by means of neutron diffraction.The results from profile refinement show that Al enters the tetragonal structure of Nd_2Fe_(14)B and occupies the 4c and 8j_2 sites of the space group P4_2/mnm preferably.The relation between the site occupancies and the magnetic proper- ties is discussed preliminarily.
关键词:
Y_2(Fe_(0.95)Al_(0.05))_(14)B
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null
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null
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null
材料科学技术（英文）
The results of molecular dynamics calculations on the interfacial energies and atomic structures of Ag/Ni and Cu/Ni interfaces are presented. Calculation on Ag/Ni interfaces with low-index planes shows that those containing the (111) plane have the lowest energies, which is in agreement with the experiments. Comparing surface energy with interfacial energy, it is found the order of the interfacial energies of Ag/Ni and Cu/Ni containing the planes fall in the same order as solid-vapor surface energies of Ag, Cu and Ni. In this MD simulation, the relaxed atomic structure and dislocation network of (110)(Ag)parallel to(110)(Ni) interface are coincident to HREM observations.
关键词:
molecular dynamics;interfacial energy;atomic structure;heterophase;boundary;fcc metals;model;boundaries;liquid;nickel
Haijiang LIU
,
Shaoqing WANG
,
An DU
,
Caibei ZHANG
材料科学技术（英文）
The results of molecular dynamics calculations on the interfacial energies and atomic structures of Ag/Ni and Cu/Ni interfaces are presented. Calculation on Ag/Ni interfaces with low-index planes shows that those containing the (111) plane have the lowest energies, which is in agreement with the experiments. Comparing surface energy with interfacial energy, it is found the order of the interfacial energies of Ag/Ni and Cu/Ni containing the planes fall in the same order as solid-vapor surface energies of Ag, Cu and Ni. In this MD simulation, the relaxed atomic structure and dislocation network of (110) Ag||(110) Ni interface are coincident to HREM observations.
关键词:
Molecular dynamics
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null
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null
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null
B.W. Wang
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H. Shen
金属学报(英文版)
Ni-Cr System solar selective thin solid films were prepared by d.c. magnetron reactivesputtering under the atmosphere of O2 and N2. Ni-Cr alloy was chosen as targetmaterial and copper sheets as substrate. Using SEM, Spectrophotometer and Talystepto analyze the relations between the selective characteristic and the structure, theformation and the thickness of the thin films. The aim is to obtain good solar selectivethin films with high absorptance and low emittance, which is applied to flat plate solarheat collectors.
关键词:
solar selective thin film
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null
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null
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null
Journal of Applied Physics
Using the full potential linearized augmented plane wave method based on the spin density functional theory, we investigate the ferromagnetic properties, the electronic structure, and the formation energy of Ga(0.9375)M(0.0625)N (M=vacancy, Ca). The calculations indicate that both cases prefer ferromagnetic ground state. The magnetic moments mainly come from the N atoms surrounding the defect centers, which are different from the conventional diluted magnetic semiconductor. High formation energy for the Ga vacancy Suggests that the defect concentration is too low to result in the ferromagnetic GaN. The formation energy for the two substitutional (Ca(Ga),Ca(N)) and two interstitial sites (tetrahedral T, Ca(i-T) and octahedral O, Ca(i-O)) doped configurations indicates that Ca prefers the substitutional Ga in GaN. The defect concentrations for the Ga(0.9375)Ca(0.0625)N under thermal equilibrium N-rich and N-realistic growth conditions are also discussed, respectively. The calculations show that defect concentration under N-rich condition can readily reach 7%, while under N-realistic growth condition, the maximum defect concentration is as low as 1.71% when the growth temperature increases to 1100 K (melting point of GaN). These results suggest that it would be a little difficult to achieve ferromagnetic state for Ga(0.9375)Ca(0.0625)N using the chemical-equilibrium fabrication method, such as chemical precipitation. Using the same method as that for Cu-doped ZnO [L. H. Ye et al., Phys. Rev. B 73, 033203 (2006)], the transition temperature of Ga(0.9375)Ca(0.0625)N may be close to room temperature. (C) 2008 American Institute of Physics.
关键词:
generalized gradient approximation;doped zno;gan;semiconductors;calcium;systems;origin
Journal of Chemical Physics
Based on Mei's embedded atom model [Mei , Phys. Rev. B 43, 4653 (1991)] molecular dynamics simulations have been performed to investigate the rapidly cooling processes of Cu. The atomic transport property, namely the self-diffusion coefficient, is computed in the liquid state, and the results near the melting point of Cu are in good agreement with experimental data and other computational values. The atom diffusion movements during the long period of relaxation have been also studied around the solidification temperature T-c. To describe the complex microstructural evolutions during the rapidly cooling processes and the long relaxation processes, the pair correlation function and the pair analysis technique are used. It is demonstrated that the crystallization of amorphous Cu is caused by the atomic diffusion. (C) 2004 American Institute of Physics.
关键词:
transition-metals;computer-simulation;supercooled-liquid;model;fcc;potentials;diffusion
Shuwang DUO
,
Meishuan LI
,
Yaming ZHANG
材料科学技术（英文）
In order to study the atomic oxygen corrosion of spacecraft materials in low earth orbit environment, an atomic oxygen simulator was established. In the simulator, a 2.45 GHz microwave source with maximum power of 600 W was launched into the circular cavity to generate ECR (electron cyclotron resonance) plasma. The oxygen ion beam moved onto a negatively biased Mo plate under the condition of symmetry magnetic mirror field confine, then was neutralized and reflected to form oxygen atom beam. The properties of plasma density, electron temperature, plasma space potential and ion incident energy were characterized. The atomic oxygen beam flux was calibrated by measuring the mass loss rate of Kapton during the atomic oxygen exposure. The test results show that the atomic oxygen beam with flux of 1016~1017 atoms•cm-2•s-1 and energy of 5~30 eV and a cross section of Φ80 mm could be obtained under the operating pressure of 10¬-1~10-3 Pa. Such a high flux source can provide accelerated simulation tests of materials and coatings for space applications.
关键词:
Atomic oxygen
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null
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null
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null
材料科学技术（英文）
In order to study the atomic oxygen corrosion of spacecraft materials in low earth orbit environment, an atomic oxygen simulator was established. In the simulator, a 2.45 GHz microwave source with maximum power of 600 W was launched into the circular cavity to generate ECR (electron cyclotron resonance) plasma. The oxygen ion beam moved onto a negatively biased Mo plate under the condition of symmetry magnetic mirror field confine, then was neutralized and reflected to form oxygen atom beam. The properties of plasma density, electron temperature, plasma space potential and ion incident energy were characterized. The atomic oxygen beam flux was calibrated by measuring the mass loss rate of Kapton during the atomic oxygen exposure. The test results show that the atomic oxygen beam with flux Of 10(16)similar to10(17) atoms(.)cm(-2.)s(-1) and energy of 5similar to30 eV and a cross section of phi80 mm could be obtained under the operating pressure of 10(-1)similar to10(-3) Pa. Such a high flux source can provide accelerated simulation tests of materials and coatings for space applications.
关键词:
atomic oxygen;low earth orbit space environment;ECR plasma;microwave;surfaces;erosion
