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EXPLOSIVE HARDENING OF HIGH Mn STEEL

LI Mingshan ZHAO Shida Institute of Mechanics , Academia Sinica , Beijing , ChinaSHI Guoshun Beijing Centre of Physical and Chemical Analysis , Beijing , China

金属学报(英文版)

The explosive hardening of high Mn Steel was simulated by using light gas gun under selected ranges of impact load from 10 to 20 GPa and pulse duration from 0.04 to 1.6μs.The experi- mental results showed that a lot of twins formed in the shocked high Mn steel may be the prin- cipal cause of explosive hardening.

关键词: high Mn steel , null , null , null

Studies of Physical and Chemical Properties of Two-Dimensional Hexagonal Crystals by First-Principles Calculation

Journal of the Physical Society of Japan

In this study, we implement first-principles calculation to study the physical and chemical properties of two-dimensional (2D) hexagonal crystals. The ab initio results of the crystallographic, elastic, and electronic band-gap parameters of C, Si, Ge, BN, CN, SiN, and SiC monolayers are presented. Similarly to graphene, CN and BN are among compounds with the highest 2D elasticity. The in-plane elastic moduli of Si and Ge monolayers are relative small. C, Si, and Ge monolayers are semimetal. All the four binary 2D crystals are semiconductors with wide band gaps. Two typical 2D hexagonal lattice structures, i.e., sp(2) flat and sp(3) rumpled configurations, are classified. The orbital sp(2)-hybridization in graphene and 2D BN is verified by angular-momentum projected atomic density of state calculation. 2D SiC is basically in sp(2)-hybridization. The orbital hybridization of Si, Ge, CN, and SiN monolayers is of the sp(3)-type on the whole. In view of the structural and chemical features of these monolayers, different methods for the experimental preparation of 2D crystals are suggested.

关键词: 2D crystals;orbital hybridization;elastic moduli;first-principles;calculation;iii-v compounds;elastic-constants;silicon-nitride;graphene;pseudopotentials;membranes;graphite;phase

Chemical composition and Mott-Schottky analysis of passive film formed on G3 alloy in bicarbonate/carbonate buffer solution

Dangguo LI

金属学报(英文版)

The chemical composition and semi-conductive properties of passive film on nickel-based alloy (G3 alloy) in bicarbonate/carbonate buffer solution were investigated by Auger spectroscopy (AES), X-ray photoelectron spectroscopy (XPS), electrochemical impedance spectra (EIS) and Mott-Schottky plot. AES and XPS results showed that the passive film appeared double-layer, in which the inner film was composed of nickel oxide, the mixed nickel-chromium-molybdenum-manganese oxides were the major component of the outer film. The electrochemical results revealed that the factors including frequency, potential, time, temperature and pH value can affect the semi-conductive property, the doping densities decreased with increasing potential and pH value, prolonging time, and decreasing temperature. According to the above results, it can be concluded that the film protection on the substrate enhanced with increasing potential and pH value, prolonging time, and decreasing temperature.

关键词: Nickel-based alloy , 俄歇分析 , X-射线光电子能谱 , 电化学阻抗谱 , Mott-Schottky曲线

Physical Properties of Nano-HAs/ZrO2 Coating on Surface of Titanium Materials Used in Dental-Implants and Its Biological Compatibility

Journal of Nanoscience and Nanotechnology

A gradient composite coating on the surface of titanium materials, which are used in dental implants, is prepared using an electric-chemical method. The physical properties of the composite coating and its strength of combining with titanium material are studied by the scanning electron microscope, energy dispersive spectrum and X-ray diffraction analysis, etc. The results show that the nanohydroxyapatite/ZrO2 composite coating is uniformly deposited and formed on the surface of titanium materials, its strength of combining with titanium surface reaches 16.3 MPa, which is determined by the tensile test. The immersion experiment shows that a new matter of carbonate-apatite is distributed uniformly on the surface of the composite coating of nanohydroxyapatite/ZrO2. The cell experiment of cultivate exhibits that the osteoblasts MG-63 is also grown well on the surface of the composite coating. These results indicate that the nanohydroxyapatite/ZrO2 composite coating on the surface of titanium materials has a good biological activity and compatibility and could be used in the dental-implants.

关键词: Nanohydroxyapatite;ZrO2;Titanium Materials;Osteoblasts MG-63;Electrochemical Deposition Method;Composite Coating;Biological;Compatibility;pulsed electrochemical deposition;nano-hydroxyapatite;bone tissue;composite;ceramics;zirconia;biocompatibility;nanoparticles;cytotoxicity;temperature

Theoretical study of the electron paramagnetic resonance parameters and local structure for the tetragonal Ir(2+) centre in NaCl

Pramana-Journal of Physics

The electron paramagnetic resonance (EPR) parameters (the g factors, hyperfine structure constants and the superhyperfine parameters) for the tetragonal Ir(2+) centre in NaCl are theoretically investigated from the perturbation formulas of these parameters for a 5d(7) ion in tetragonally elongated octahedra. This impurity centre is attributed to the substitutional [IrCl(6)](4-) cluster on host Na(+) site, associated with the 4% relative elongation along the C (4)-axis due to the Jahn-Teller effect. Despite the ionicity of host NaCl, the [IrCl(6)](4-) cluster still exhibits moderate covalency and then the ligand orbital and spin-orbit coupling contributions should be taken into account. In addition, the theoretical EPR parameters based on the Jahn-Teller elongation show good agreement with the observed values.

关键词: Electron paramagnetic resonance;crystal- and ligand-field theory;Ir(2+);NaCl;transition-metal ions;epr spectroscopic investigations;atomic;screening constants;nuclear double-resonance;magnetic-resonance;superposition model;silver-halides;spin-resonance;scf functions;complexes

Theoretical studies of EPR parameters and microstructure of the rhombic Co2+-V-Ag centre in AgCl

Physica Status Solidi B-Basic Research

The perturbation formulae of EPR g-factors g(i) (i = x, y, z) and hyperfine constants Ai for a 3d(7) (Co2+) ion at a rhombic octahedral site in a crystal are established from a cluster approach. In these formulae, the contributions from the covalency effect, the configuration interaction and the rhombic crystal field are considered and the parameters used in the calculation of EPR parameters. except the core polarization constant x in the calculation of Al, can be estimated from the optical spectra and the structure data of the studied system. From these formulae, the EPR parameters g(i) and A(i) for the rhombic Co2+-V-Ag centre in AgCl are reasonably explained by considering suitable rhombic distortion and so the microstructure of this rhombic centre is obtained.

关键词: superposition model;crystals

Theoretical investigations of the g-factors and hyperfine structure constants for a tetragonal Co2+ centre in NH4Cl crystal

Physica Status Solidi B-Basic Research

The EPR g-factors g(\\), g(perpendicular to) and hyperfine structure constants A(\\), A(perpendicular to) for a tetragonal Co2+ centre, i.e.. Co(H2O)(2)Cl-4 centre, in NH4Cl crystal are calculated from the perturbation formulas based on a cluster approach. In these formulas, the parameters related to the contributions from the configuration interaction. the covalency effect and the low-symmetry crystal field can be obtained from the optical spectra and the structural model and data of the studied system. The core polarization constant it in the calculation formulas of hyperfine constants is used as an adjustable parameter. The calculated results are in good agreement with the observed values.

关键词: superposition model;centers;resonance;ions;cr3+

Structural evolution and physical properties of Bi(1-x)Gd(x)FeO(3) ceramics

Acta Materialia

The crystal structure and physical properties of Bi(1-x)Gd(x)FeO(3) ceramics with x <= 0.5 have been studied by X-ray diffraction, differential scanning calorimetry, dielectric and magnetic measurements. Bi(1-x)Gd(x)FeO(3) compounds crystallize at room temperature in R3c structure for x < 0.08 and in Pbnin structure for x >= 0.3. The R3c phase transforms to the Pbnm phase as temperature increases. Temperature-dependent dielectric response and low-temperature X-ray diffraction indicate a phase transition of the Pbnm phase at low-temperature. Detailed structural analysis indicates that the interaction between Bi and O plays an important role in the evolution of structure and physical properties. A phase diagram is constructed to illustrate the physical property composition temperature relations. (C) 2010 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

关键词: Bi-based magnetoelectric perovskites;Crystal structure;Phase;transformation;X-ray diffraction;ferroelectric properties;magnetic-properties;room-temperature;bismuth;ferrite;bifeo3 films;perovskites;diffraction;chemistry;crystal

Discrepancies in the Regression Modelling of Recrystallization Rate as Using the Data from Physical Simulation Tests

L.P. Karjalainen , M.C. Somani , S.F. Medina

金属学报(英文版)

The analysis of numerous experimental equations published in the literature reveals a wide scatter in the predictions for the static recrystallization kinetics of steels. The powers of the deformation variables, strain and strain rate, similarly as the power of the grain size vary in these equations. These differences are highlighted and the typical values are compared between torsion and compression tests. Potential errors in physical simulation testing are discussed.

关键词: physical simulation , null , null , null , null

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