WADSWORTH Jeffrey and FLUSS Michael(Chemistry and Materials Science Directorate
,
Lawrence Livermore National Laboratory
,
Livermore
,
CA 94551)
金属学报(英文版)
The role of the National Laboratories is summarized from the era of post World War II to the present time. The U.S. federal government policy for the National Laboratories and its influence on their materials science infrastructure is reviewed with respect to .determining overall research strategies, various initiatives to interact with industry (especially in recent years),building facilities that serve the nation, and developing leading edge research in the materials sciences. Despite reductions in support for research in the U.S. in recent years, and uncertainties regarding the specific policies for Research &Development (R&D) in the U.S., there are strong roles for materials research at the National Laboratories. These roles will be centered on the abilities of the National Laboratories to field multidisciplinary teams, the use of unique cutting edge facilities, a focus on areas of strength within each of the labs,increased teaming and partnerships, and the selection of motivated research areas. It is hoped that such teaming opportunities will include new alliances with China, in a manner similar, perhaps, to those recently achieved between the U.S. and other countries.
关键词:
: U.S. Materials Science. U.S. National Laboratories and Facilities
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null
A .A.Khedr
,
I.Z.Selim
,
K.M.El-Sobki and O.S.Shehata(Physical Chemistry Dept.
,
National Research Centre
,
Dokki
,
Cairo
,
Egypt)
材料科学技术（英文）
Electrochemical behaviour of stainless steel type 430 in acidic solutions of methanol, ethanol and in their binary mixtures with water (from 0 to 100% alcohol) at 25℃ has been studied. using potentiostatic poIarization technique and weight loss method. It was found that the corrosion rate of the metal was affected by the physico-chemical properties of the media such as, viscosity, state of solvation, molar volume contraction, proton availability and dielectric constant, it was demonstrated from the potentiostatic study that the active passive transition strongly depended on the concentration of the acid, and on the water content of the media.
关键词:
Z.M.Hanafi
,
F.M.Ismai and M.Sb.Khalil (Inorganic Chemistry Dept.
,
National Research Centre
,
Dokki
,
Cairo
,
Egypt)
材料科学技术（英文）
Infrared absorption spectra of orange, black and transferred Sb2S3 samples have been Studied in the spectral range 200~4000cm-1. The pronounced difference between the different samples is the appearance of excess sulphur present in the orange and transferred samples except those of transferred at 543 K and the black Sb2S3. The change of sharpness of some IR peaks reveals the amorphous/crystalline change. The effect of the degree of crystallinity and stoichiometry on the energy gap values was investigated using optical method. The obtained dielectric parameters ε'and ε" of the different samples are thoroughly afFected by the degree of cryStallinity and smoothly affected by either the frequency or the temperature or both, except at lower frequencies.
关键词:
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
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+
Pramana-Journal of Physics
By calculating the optical spectrum band positions and EPR parameters (g factors, g(parallel to), g(perpendicular to) and zero-field splitting D) by diagonalizing the complete energy matrix of 3d(8) ions in trigonal symmetry, the defect structure of Ni2+ centre in alpha-LiIO3 crystal is studied. It is found that to reach the good fits of optical and EPR data between calculation and experiment, the Ni2+ ion should shift by Delta z approximate to 0.298 angstrom along C-3-axis and the O-2-ions between the Ni2+ ion and Li+ vacancy (V-Li) should be displaced away from the V-Li by Delta x approximate to 0.097 angstrom because of the electrostatic interaction. The results are discussed.
关键词:
Optical spectra;electron paramagnetic resonance;defect structure;Ni2+;alpha-LiIO3.;field;ions;cr3+;temperature;parameters;epr;pressure;model;liio3
Z. Yang
,
J.P. Li
,
J.X. Zhang
,
G.W.Lorimer
,
J. Robson
,
null
,
null
,
null
,
null
金属学报(英文版)
The current research and development of magnesium alloys is summarized. Several aspects of magnesium alloys are described: cast Mg alloy, wrought Mg alloy, and novel processing. The subjects are discussed individually and recommendations for further study are listed in the final section.
关键词:
Magnesium alloys
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null
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null
