M. V. Nathal (NASA Lewis Research Center Cleveland OH. USA)
金属学报(英文版)
The purpose of this paper is to review the current state of development of new composite materials for advanced aircraft engines. The advantages and disadvantages of Ti-base.NiAl-base, and MoSi_2-base composites as replacements for today's Ni-base superalloys are discussed from the standpoint of key technical issues. current status, and future directions. Results describing progress in both improved understanding of the mechanisms of deformation and fracture, and improved material performance will be covered.
关键词:
: composites. Ti alloys
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Journal of Physics and Chemistry of Solids
The tetragonal distortion for the tetragonal V2+-V-M center in KBr:V2+ crystal is estimated by analyzing its EPR data from two theoretical models, one is the two spin-orbit (S.O.) parameter model where the contributions to EPR parameters from both the S.O. coupling of the central metal ion and that of the ligands are considered and another is the conventional one-S.O.-parameter model where only the contribution from the S.O. coupling of the central metal ion is included. The result from the two-S.O.-parameter model is more than ten times that of the one-S.O.-parameter model. The reasonableness of the former is discussed. (C) 1998 Elsevier Science Ltd. All rights reserved.
关键词:
inorganic compounds;crystal fields;defects;electron paramagnetic;resonance (EPR);epr parameters;transition;ions
D.Eylon
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S.R.Seagle
材料科学技术（英文）
The state of Ti research, development and industry is reviewed in this article. The fifty-year anniversary of Ti technology commercialization in the USA provides an opportunity for a historical perspective. Incorporation of "information-age" tools into alloy development, processing, and production invigorates the technology. Consolidation, diversification and globalization have been transforming the Ti industry in the recent years.
关键词:
Acta Chimica Sinica
Passive film formed on 304 stainless steel in 2.5 mol/L H2SO4 solution by using alternating voltage (A. V.) passivation have been investigated by measuring capacitance and photoelectrochemical parameters. The investigation of the effect of measure frequency on the slope of Mott-Schottky curve has been carried out. The photoelectrochemical measurements were consistent with the capacitance measurement. Analysis of the experimental results showed that the passive film formed 304 stainless steel by using A. V. passivation exhibits semiconducting properties. Using the simple model of semiconductor rather than the multi-donor level model can explain satisfactorily the semiconducting behavior of the film formed on 304 stainless steel by using A.V. passivation.
关键词:
A. V. passivation;passive film;semiconducting properties;stainless;steel;model;electrodes
Chemical Physics Letters
The relationship between the local structure and EPR spectrum is studied by diagonalizing the complete energy matrices for Mn(2+) in a trigonal ligand-field. The results show that the degree of distortion increases with temperature increasing whether it is compressed or elongate distortion, and the distorted tendency of the local structure is different according to the sign of D. Meanwhile, the distortion of Cd(BF(4))(2)center dot 6H(2)O:Mn(2+) system is more sensitive to temperature than that of ZnSnF(6)center dot 6H(2)O:Mn(2+) system. Moreover, the EPR parameter D is closely associated with the local structure parameters R and h while (a - F) is mainly concerned with R. (C) 2010 Elsevier B. V. All rights reserved.
关键词:
single-crystals;optical-absorption;phase-transitions;mn2+;field;ions;resonance;spectra;relaxation;fe-3+
Spectrochimica Acta Part a-Molecular and Biomolecular Spectroscopy
The spin Hamiltonian parameters (zero-field splitting D, g factors g(parallel to), g(perpendicular to) and hyperfine structure constants A(parallel to), A(perpendicular to)) for M2+ (M = Co, Mn, V and Ni) ions in CsMgCl3 are studied by using the perturbation formulas of the spin Hamiltonian parameters for 3d(n) (n = 7, 5, 3, 8) ions in trigonal symmetry based on the cluster approach. In these formulas, the contributions to the spin Hamiltonian parameters from the admixture of d orbitals of the central ions with the p orbitals of the ligands and from the trigonal distortion are included and the parameters related to these effects can be obtained from the optical spectra and the local structures of the studied systems. Based on the studies, it is found that the local trigonal distortion angle beta in the M2+ impurity center is unlike that beta(H) (approximate to51.71degrees) in the host CsMgCl3. The spin Hamiltonian parameters for these divalent ions in CsMgCl3 are also satisfactorily explained by using the local angle beta. The validity of the results is discussed. (C) 2003 Elsevier B.V. All rights reserved.
关键词:
electron paramagnetic resonance;crystal-field theory and spin;Hamiltonians;local structure;m2+(M = Co, Mn, V and Ni);CSMgCl3;acoustic paramagnetic resonance;atomic screening constants;superposition model;tetragonal symmetry;crystal-structure;epr;parameters;scf functions;sites;absorption;fluoride
Physica Status Solidi B-Basic Research
By means of the diagonalization of the complete energy matrix of 3d(2)/d(8) ions in trigonal symmetry and in consideration of the covalency reduction effect, the optical and EPR spectra of V3+ ions in C(NH2)(3)Al(SO4)(2)center dot 6H(2)O crystal are calculated. The results are in agreement with the observed values. The difficulty about the too-large spin-orbit coupling parameter in the explanation of EPR parameters from the Abragam and Pryce model is removed. (c) 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
关键词:
aluminum sulfate hexahydrate;electron-paramagnetic-resonance;pressure;field;cr3+
Chemical Physics Letters
A theoretical method for investigating the inter-relation between the electronic and the molecular structures of a d(5) ion in a tetragonal ligand-field has been established on the basis of a 252 x 252 complete energy matrix. Using this method, the local structure parameters of the Fe3+-V-M system in AMF(3):Fe3+ crystals are determined by the experimental EPR spectra at T = 300 K. It is shown that, the local lattice structure around an octahedral Fe3+ center has a compression distortion along the crystalline axis in AMF(3):Fe3+ crystal. From our analysis, we also conclude that Delta R vs. 10(4)b(2)(0) is approximately linear for the Fe3+-V-M system in AMF(3):Fe3+ crystals. (c) 2006 Elsevier B.V. All rights reserved.
关键词:
electron-paramagnetic-resonance;spin-hamiltonian parameters;epr-spectra;ions;kznf3;phase;exafs;laser;field;site
