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排序方式： 共有700条查询结果，搜索用时 15 毫秒
1.
Hongwei Liu Jiangwen Liu Guangcai Su Weizhou Li Jianmin Zeng Zhiliu Hu 《Metallurgical and Materials Transactions A》2012,43(10):3636-3641
The crystallography of body-centered-cube to face-centered cube (bcc-to-fcc) diffusion phase transformations in a duplex stainless steel and a Cu-Zn alloy, including long axis, orientation relationship (OR), habit plane (HP), and dislocation spacing, is successfully interpreted with one-step rotation from the Bain lattice relationship by applying a simplified invariant line (IL) analysis. It is proposed that the dislocation slipping direction in the matrix plays an important role in controlling the crystallography of precipitation. 相似文献
2.
Mingjun Pang Yongzhong Zhan Haizhou Wang Wenping Jiang Yong Du 《Computational Materials Science》2011,50(10):2930-2937
The structural, electronic and elastic properties of the AlCu2M (M = Sc, Ti and Cr) compounds in the pressure range of 0–100 GPa was investigated based on density functional theory. The calculated lattice parameters of the AlCu2M compounds at zero pressure and zero temperature are in very good agreement with the existing experimental data. The bulk modulus, shear modulus and Young’s modulus increases with the increase of pressure, which indicates that higher materials hardness may be obtained when increasing pressures. The bulk modulus and Young’s modulus of AlCu2Cr is the greatest under pressure. The shear modulus of AlCu2Ti is the highest above 30 GPa, while that of the AlCu2Sc is the strongest below 30 GPa. The calculated B/G values at zero and higher pressure indicated that they are ductile materials. The electronic densities of states and bonding charge densities have been discussed in details, revealing these compounds exhibit half-metallic behavior. In addition, the pressure dependences of Debye temperatures of AlCu2M compounds have also been calculated. The results indicate that Debye temperatures increase with increasing pressure. 相似文献
3.
《Hydrometallurgy》2006,81(3-4):234-240
The oxidation of glucose during the reductive leaching of pure MnO2 and manganese ore in sulphuric acid at 90 °C MnO2 was investigated. The aim was to identify the derivatives and the chemical pathway of glucose oxidation. Organic derivatives were monitored by HPLC using an Aminex HPX-78H column and UV detection. Chromatographic patterns of leaching solutions showed that major compound formed was formic acid. Minor quantities of glycolic, glyceric and traces of gluconic acids were identified. Results suggest that during the leaching reaction, the carbon chain of glucose is shortened by detachment of one carbon atom as formic acid. 相似文献
4.
《Computational Materials Science》2011,50(2):363-372
In the study of crystalline materials, the lattice constant (LC) of perovskites compounds play important role in the identification of materials. It reveals various interesting properties. In this study, we have employed Support Vector Regression, Artificial Neural Network, and Generalized Regression Neural Network based Computational Intelligent (CI) techniques to predict LC of cubic and monoclinic perovskites. Due to their interesting physiochemical properties, investigations in modeling the structural properties of perovskites have gained considerable attention. A dataset of a reasonable number of cubic and monoclinic perovskites are collected from the current literature. The CI techniques can efficiently correlate the LC of the perovskites materials with the ionic radii of constituent elements. A performance analysis of CI techniques is carried out with Multiple Linear Regression techniques, SPuDS software, and Density-Functional Theory. We have observed that the CI techniques yield accurate LC prediction as against the conventional approaches.Availability: Matlab based computer program developed for this work is available on request. 相似文献
5.
《Materials Letters》2005,59(14-15):1889-1892
Eutectic alloy Sn–9Zn is regarded as one of the potential substitutes for Pb-containing solders, although it has some drawbacks yet to overcome. One of the problems involved is drastic viscosity increase of rosin-based flux during soldering or storage. In the present work we investigated the role of ZnO in the viscosity transition of rosin. The results show that the viscosity transition is directly caused by the presence of ZnO in molten rosin and, at a certain temperature, there exists a critical ZnO concentration for its occurrence. The critical ZnO concentration increases with temperature. A graph is presented to show the conditions for the viscosity transition, in a ZnO concentration–temperature space. The transition is found to be reversible when shifting temperature or ZnO concentration across the boundary and to assume the features of a thermally activated phase transformation. 相似文献
6.
《Materials Letters》2005,59(19-20):2412-2417
High quality poly (5-nitroindole) (PNP) films were synthesized electrochemically by direct anodic oxidation of 5-nitroindole in boron trifluoride diethyl etherate (BFEE) containing additional 10% diethyl ether (by volume). The additional diethyl ether improved the solubility of the monomer in BFEE. In this medium, the oxidation potential onset of 5-nitroindole was measured to be only 1.04 V vs. SCE. PNP films obtained from this medium showed good electrochemical behavior with conductivity of 10− 2 S cm− 1. Structural studies showed that the polymerization of 5-nitroindole ring occurred at 2,3 position. As-formed PNP films could be dissolved in acetone, tetrahydrofuran (THF), dimethyl sulfoxide (DMSO), etc. Fluorescent spectral studies indicated that PNP was a good green light emitter with the best excitation and emission wavelength of 420 and 550 nm, respectively. To the best of our knowledge, this is the first time that nitro group-substituted high-quality conducting polymer films can be electrodeposited. These results will be greatly helpful for the understanding of the synthesis and properties of nitro-substituted conducting polymers and provide a new route for the post-functionalization of nitro-substituted conducting polymers through the reduction of nitro group. 相似文献
7.
《低温学》1987,27(7):361-378
This Paper reviews the present state-of-the-art of preparing multifilamentary A-15 superconductors. The most common types, Nb3Sn and V3Ga, are presently produced by the so-called bronze process. The highest Jc (overall) = 3.5 × 104 cm−2 (at 15 T and 4.2 K), obtained for bronze processed Nb3Sn composites through Ti addition, has pushed the useful limit of this material from 12 to 16 T. Similarly a Jc of 1 × 105 A cm−2 (at 20 T and 4.2 K) for the A-15 V3Ga has been attained through elemental additions to the core and the bronze matrix. To circumvent the problem of work-hardening of the bronze, several variations of the bronze process such as the internal tin method, the Nb tube method, the ECN method and jelly roll method have also been upgraded to commercial scale. Composites of Nb3Sn and V3Ga have been recently produced successfully on a laboratory scale following the so called in situ technique. These composites not only have a superior Jc value but display improved strain tolerance due to the ultrafine nature of the filaments formed in situ. In situ filamentary A-15 composites with high Jc values have also been produced by following the powder metallurgy technique. The infiltration technique has been found useful for producing high field Nb3(Al, Ge), Nb3(Al, Si) and Nb3Sn composite conductors with high εirr. Superior materials such as Nb3Al, Nb3Ga and Nb3(Al,Ge) with high Jc performance have been synthesized using the laser beam technique. Nb3Ge tapes with Tc = 21 K and Jc = 105 A cm−2 (at 18 T and 4.2 K) have been successfully produced on a laboratory scale by following the CVD technique. Thus, there are several available options from which to choose a technique for fabricating filamentary composites of ubiquitous Nb3Sn and V3Ga. New techniques for fabricating superior materials like Nb3Al, Nb3Ga, Nb3Ge and Nb3(Al, Ge) also seem to be at an advanced stage of development. 相似文献
8.
9.
《Materials Chemistry and Physics》1988,19(4):369-380
Electrochemical lithium insertion in pure and (PTFE-and/or C-) mixed CdIn2S2Se2 has been investigated by galvanostatic discharge experiments in the (−) Li/organic electrolyte/CdIn2S2Se2 (+) cell, also considering the behaviour in quasi-equilibrium open-circuit conditions, and by cyclic voltammetry. Structural changes induced by lithium insertion have been observed by powder X-ray diffraction measurements. The reversibility of the process is poor in the whole range explored, but differences in behaviour are noticed. During a galvanostatic discharge of the cell up to about 0.7 F.mol−1 no structural change takes place and the lithium diffusion process is slow, as shown by the very low value of the chemical diffusion coefficient (around 10−12 cm2.s−1, at 30 °C) determined according to a current-pulse relaxation technique. During a deeper discharge up to 5.35 F.mol−1 two plateaux — a short and an extended one — are noted in the experimental curve, while pseudocrystalline phases are formed. As a consequence of these structural rearrangements, the time needed to reach open-circuit quasi-equilibrium conditions after a galvanostatic discharge is high, particularly in the region of the first plateau. Analyses of the results evidence that CdIn2S2Se2 is a very interesting new compound, more significant for its fundamental properties than in view of its application as cathode material in aprotic solvent lithium cells. 相似文献
10.
《Acta Metallurgica Materialia》1993,41(10):2933-2937
A critical area in nanocrystalline materials research is development of grain growth relations for controlled, uniform heating or cooling. Theoretical relations describing nonisothermal coarsening are derived in terms of classical isothermal materials properties. An effective temperature is defined as the temperature at which equivalent coarsening occurs to that predicted during the heating or cooling period. This parameter is only a function of the endpoint temperatures and the activation energy for grain growth. Simplifications of the equations for grain size and effective temperature are derived and their implications discussed. 相似文献