K. Mii (Sumitomo Metal Industries
,
Ltd.
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1-t-3 Otemachi
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Tokyo 100
,
Japan)M Amano (National Research Institute for Metals
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1-2-1 Sengen
,
Tsukuba 305
,
Japan)
金属学报(英文版)
The R & D of hydrogen absorbing alloys in Japan started in the early 1970s.Many alloys such as TiMm1.5 based alloys, Fe-Ti-O alloys (e.g. FeTi1.15 O0.024) andthe(mischmetal)Ni5 based alloys (e.g. MmNi4.5 Cr0.46 Mn0.04) were developed by the early 1980s. The application of these alloys to hydrogen storage, heat storage, heat pump, hydrogen purification and motor vehicles has been tried in many iaboratories,and the various techniques for using hydrogen absorbing alloys have been developed.The standarkization of evaluation methods for hydrogen absorbing alloys has been promoted by the Ministry of International Trade and Industry (MITI), and four of them were established as Japanese Industrial Standard (JIS).Alloys for Ni-Metal Hydride batteries have been extensively investigated since 1987in Japun. Mm-Ni-Co-Al-Mn alloys (e.g. MmNi3.55 Co0.75Al0.9Mn0.4) have been devel-oped and commereialized since 1990. The amount of production of small-size Ni-MH batteries in 1995 was about three hundred milliion in number and about one hundred billion yen. The R & D for higher enerpy-density Ni-MH batteries is intensively in progress.MITI and STA (Science and Technology Agency) have promoted the R & D of hydro-gen absorbing alloys in Japan by carrying out the national projects such as Sunshine Program (MITI: 1974-1993) and Utilization of Wind Engeray (STA 1980-1985). The New Sunshine Program (MITI 1993-2020) have started in 1993. This program con-tains the application of hydrogen absorbing alloys to Economical- Enerpy- City System and to We-NET (International Clean Energy System of Technology Utilizing Hydro-gen: World Energy Network.
关键词:
hydrogen absorbing alloy
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null
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null
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Philosophical Magazine
The EPR g factors, g// and g perpendicular to, of tetragonally elongated and compressed CuIIN6 octahedral clusters (with the ground states |dx2 - y2 > and |dz2 >, respectively) in [image omitted] (MI = K, Rb, Cs; MII = Ca, Sr, Ba, Pb) crystals were calculated using a two-mechanism model. In the model, the contributions to the g-shifts, gi (= gi - gs, where i = // or perpendicular to; gs approximate to 2.0023 is the free-ion g value), from both the crystal-field (CF) mechanism related to CF excited states and the charge-transfer (CT) mechanism related to CT excited states, which is neglected in the widely-used CF theory, were considered. For the CF mechanism, two theoretical methods, the perturbation theory method (PTM) and the complete diagonalization (of energy matrix) method (CDM), were applied. The CF parameters used were calculated from the superposition model, in which the structural data for CuIIN6 clusters in [image omitted] crystals were measured exactly by X-ray diffraction. The calculated g factors for both the tetragonally elongated and compressed CuIIN6 octahedra are in reasonable agreement with the experimental values. For the strongly covalent CuIIN6 clusters in crystals with different ground states, both the PTM and CDM can be applied to calculate the g-shifts, [image omitted], arising from the CF mechanism, but exact and reasonable calculations of g factors should take both CF and CT mechanisms into account.
关键词:
crystal field;electron paramagnetic resonance;octahedral cluster;charge transfer;spin-hamiltonian parameters;atomic screening constants;jahn-teller;distortion;temperature-dependence;lead hexanitrocuprate(ii);2-mechanism model;scf functions;br crystals;complexes;bands
Juhua HUANG
,
Jinjun RAO
,
Xuefeng LI
材料科学技术（英文）
Sheet metal forming is widely applied to automobile, aviation, space flight, ship, instrument, and appliance industries. In this paper, based on analyzing the shortcoming of general finite element analysis (FEA), the conception of parametric finite element analysis (PFEA) is presented. The parametric finite element analysis, artificial neural networks (ANN) and genetic algorithm (GA) are combined to research thoroughly on the problems of process parameters optimization of sheet metal forming. The author programs the optimization scheme and applies it in a research of optimization problem of inside square hole flanging technological parameters. The optimization result coincides well with the result of experiment. The research shows that the optimization scheme offers a good new way in die design and sheet metal forming field.
关键词:
Sheet metal forming
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null
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null
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Intermetallics
An eutectic multiphase alloy NiAl-28Cr-5.94Mo-0.05Hf-0.01Ho (at.%) was directionally solidified by liquid metal cooling technique at withdrawal rates of 3, 8 and 10 mm min(-1). The microstructure and tensile properties of alloys at room temperature, 1253 K and 1373 K were investigated. With the increase of withdrawal rate, the microstructure was refined including the refinement of eutectic cells and lamellae between the NiAl and Cr(Mo) phases. At room temperature, the alloys fractured as cleavage mode. At 1253 K, yield behavior occurred which lead to higher of tensile strength and ductility compared to those at room temperature, and the properties are independent of withdrawal rate. At 1373 K, tensile properties increase with the increase of withdrawal rate, and both the strength and elongation rate are lower than those at 1253 K. The mechanisms responsible for these changes were discussed. (C) 2009 Elsevier Ltd. All rights reserved.
关键词:
Nickel aluminides;based on NiAl;Mechanical properties at ambient;temperature;Mechanical properties at high temperatures;nial-cr;mechanical-properties;microstructure
Nanoscale Research Letters
The linear thermal expansions (LTE) of bulk nanocrystalline ingot iron (BNII) at six directions on rolling plane and conventional polycrystalline ingot iron (CPII) at one direction were measured from liquid nitrogen temperature to 300 K. Although the volume fraction of grain boundary and residual strain of BNII are larger than those of CPII, LTE of BNII at the six measurement directions were less than those of CPII. This phenomenon could be explained with Morse potential function and the crystalline structure of metals. Our LTE results ruled out that the grain boundary and residual strain of BNII did much contribution to its thermal expansion. The higher interaction potential energy of atoms, the less partial derivative of interaction potential energy with respect to temperature T and the porosity free at the grain boundary of BNII resulted in less LTE in comparison with CPII from liquid nitrogen temperature to 300 K. The higher LTE of many bulk nanocrystalline materials resulted from the porosity at their grain boundaries. However, many authors attributed the higher LTE of many nanocrystalline metal materials to their higher volume fraction of grain boundaries.
关键词:
Linear thermal expansion;Bulk nanocrystallined materials;Severe;rolling technique;electrochemical corrosion behavior;different grain sizes;microstructure;diffraction;selenium;metals
Oxidation of Metals
The corrosion of four Fe-Cr commercial steels with different tents in a simulated waste-gasification atmosphere containing 0.5 vol.% H-2, 0.5 vol.% HCl, balance CO2 has been investigated at 773 and 873 K. The same materials have also been tested in the same gas mixture free from HCl at both temperatures for comparison. The results show that the materials with low-chromium content (2.25 CrMoV and NF616) undergo accelerated corrosion in the presence of HCl, while the stainless steel SS304 suffers very little corrosion. On the contrary a steel containing 12 wt.% Cr (12 CrMoV) corrodes rather rapidly at 773 K but quite slowly at 873 K. The beneficial effect of chromium on the corrosion resistance of the steels increases with the chromium content at both temperatures. The steels tested show corrosion rates generally decreasing with time, having kinetics which are approximately parabolic at 773 K but intermediate between parabolic and linear at 873 K Only little or even no chlorine can be detected at the scale/metal interface at both temperatures for all materials corroded in HO-containing atmospheres. The corrosion mechanism can be explained by the so-called "active-oxidation, model.
关键词:
Cr steels HCl;reducing atmosphere;corrosion;high-temperature corrosion;fe-cr alloys;hydrogen-chloride;chromium-alloys;gas-mixtures;oxygen;800-degrees-c;oxidation;metals;fuels
Applied Physics a-Materials Science & Processing
Transportation and thermodynamic properties of misfit-layered polycrystalline [Ca(2)CoO(3)](0.62)[CoO(2)] were measured in order to clarify the nature of metal- semiconductor transition (MST) at T (MS)a parts per thousand 400 K, above which the simultaneous decrease of resistivity and increase of thermopower with temperature give rise to a great enhancement of thermoelectric power factor up to 1000 K. A first-order phase transition characteristic around T (MS) was revealed by anomalies of resistivity, differential scanning calorimetry, and thermal expansion. The first-order characteristic of the MST can be rationalized from the Virial theorem at an itinerant to localized electron transition in the narrow e (T) band within the [CoO(2)] plane. Above T (MS), the reduction of the retained delocalized states within the matrix of localized states and the enhancement of charge carrier effective mass with increasing temperature might account for the considerable enhancement of the thermopower.
关键词:
thermoelectric properties;ca3co4o9;ceramics;system
