VR. SobolO.N MazurenkoA.A. Drozd and B.B. Boiko(Institute of Solid State and Semiconductor Physics ASB
,
P. Brovka Str.
,
17
,
220072 Minsk
,
Belarus)
金属学报(英文版)
Peculiarities of low temperature charge transport and enerpy accumulation in alu-minum devices are investigated by means of study of cylindrical conductors having a rudial cuerent fiow between inner and outer concentric contracts. Azimuthal current and, connected with it, self magnetic field are investigated in a wide range of radial current density up to 6000 A/cm2 under an external magnetic field up to 8 T Electron scattering processes are investigated and it is shown that relaxation electron mechanisms are determined by strong temperature dependence on account of high sus-ceptibility of scattering to anisotropy of electron dispersion law. The role of thermal phonons is investigated through an effective averaged conductivity tensor of polycrystalline medium. Using data of self magnetic self distribution on sample surface an energy density of self magnetic field is estimated. It is shown that at T=4.2 K average energy of self field may achieve at least 1 J/cm3. Using data of relaxation processes at temperature of liquid hydrogen it is established that self magnetic field must be a third of helium magnitude with respective self magnetic enengy density, spiral motion of carriers in this geometry being regarded as a current coils in usual inductive element.
关键词:
energy storage
,
null
,
null
,
null
Journal of Applied Physics
Amorphous BC2N powders were prepared by mechanical milling with hexagonal boron nitride and graphite as starting materials. A bulk amorphous BC2N compound was produced by sintering the as-milled amorphous BC2N powders in a vacuum of 10(-5) Torr at a temperature of 1470 K. The conductivity measurement for the bulk amorphous BC2N compound showed that it behaves as a semiconductor with band gap energy of 0.11 eV for temperatures ranging from room temperature to 560 K and a semimetal for temperatures between 560 and 740 K. The mechanism of the formation of the amorphous BC2N powders is discussed. (C) 1998 American Institute of Physics.
关键词:
bc2n
Journal of Materials Science
The solid-state reaction between crystalline nickel and pulverized melt-spun amorphous Fe78Si12B10 powders during mechanical milling has been investigated. For the powder mixtures with low nickel content (less-than-or-equal-to 30 at%), the reaction results in the production of a new amorphous phase. For the powder mixture with a high nickel content (up to 50 at%), crystalline gamma(Fe, Ni) and new amorphous phases are obtained. During the milling process, nickel atoms can dissolve in the amorphous matrix by diffusion due to severe deformation. The existence of ''free volume'' in the melt-spun amorphous phase may favour the diffusion of nickel atoms. At the same time, the elemental atoms (such as iron) in the amorphous phase may also dissolve into the nickel matrix. The amorphization between the amorphous and crystalline phases is attributed to the asymmetry of interdiffusion of the atoms in different matrices.
关键词:
metallic glasses;amorphization;alloys
Physica Status Solidi B-Basic Research
The spin Hamiltonian parameters, g factors and the hyperfine structure constants for Co4+ (3d(5)) and Ir4+ (5d(5)) in SrTiO3 are theoretically studied from the formulas of these parameters for an nd(5) (n = 3 and 5) ion in a tetragonally distorted octahedron with low spin S = 1/2. According to the theoretical analyses, the impurity-ligand bond lengths R-parallel to' parallel to the C-4 axis are found to be larger than the host values R-parallel to based on the phase transition rotation angles phi of the [TiO6](8-) octahedron by the C-4 axis at 4.2 and 77 K, respectively. The elongation of the ligand octahedra in the host may be enhanced in the impurity centers by the Jahn-Teller effect of the nd(5) ions. The theoretical results based on the above local structures show good agreement with the experimental data.
关键词:
electron-paramagnetic-resonance;atomic screening constants;phase-transition;optical-absorption;scf functions;doped srtio3;degrees k;crystals;ions;spectra
Chemical Physics Letters
The magnetism and the electronic structures of Ti-doped AlN are studied by the first-principles calculations. It is found that Ti prefers to substitute Al site in AlN host, and this doped configuration favors the ferromagnetic ground state. The magnetic moment of the supercell containing single Ti(Al) is 1.00 mu B. Electronic structures suggest magnetic moments mainly come from the doped Ti atom, Ti-doped AlN is n-type ferromagnetic semiconductor and the ferromagnetism can be explained by double-exchange mechanism. For O and Ti co-doped AlN, calculations show O(N) defect would induce magnetic moments increasing and change Ti-doped AlN from semiconductor to metal. Crown Copyright (C) 2009 Published by Elsevier B. V. All rights reserved.
关键词:
room-temperature;gan
Journal of Alloys and Compounds
Growth kinetics and interfacial morphologies of the intermetallic compounds (IMCs) between single crystal Ag and Sn-4Ag, Sn-3Cu and Sn-37Pb solders were investigated by solid-state aging at 160 degrees C and liquid-state aging at 260 degrees C. Isothermal equation of chemical reaction and phase diagrams were used to explain the effects of Ag, Cu and Pb on the growth kinetics of IMCs under solid-state and liquid-state aging conditions. The diffusion coefficients for the three solder joints of Sn-4Ag/Ag, Sn-3Cu/Ag and Sn-37Pb/Ag were calculated after solid-state and liquid-state aging. It is found that Pb can effectively retard the growth of IMCs during liquid-state aging but has little influence on the growth rate of IMCs during the solid-state aging. Some local small cracks were frequently observed in the Cu(6)Sn(5) particles near interfaces of the Sn-3Cu/Ag solder joints after solid-state aging for several days. However, there were no such local small cracks when solders or interfaces did not contain the Cu(6)Sn(5) particles after the same aging time. (C) 2008 Elsevier B.V. All rights reserved.
关键词:
Ag single crystal substrate;Lead-free solder;Intermetallic compounds;(IMCs);Growth kinetics;Local cracks;lead-free solders;electroless ni(p) metallization;intermetallic;compound;cu-sn;joints;ni;bi;nanoindentation;microstructure;wt.percent
Journal of Applied Physics
Using the full potential linearized augmented plane wave method based on the spin density functional theory, we investigate the ferromagnetic properties, the electronic structure, and the formation energy of Ga(0.9375)M(0.0625)N (M=vacancy, Ca). The calculations indicate that both cases prefer ferromagnetic ground state. The magnetic moments mainly come from the N atoms surrounding the defect centers, which are different from the conventional diluted magnetic semiconductor. High formation energy for the Ga vacancy Suggests that the defect concentration is too low to result in the ferromagnetic GaN. The formation energy for the two substitutional (Ca(Ga),Ca(N)) and two interstitial sites (tetrahedral T, Ca(i-T) and octahedral O, Ca(i-O)) doped configurations indicates that Ca prefers the substitutional Ga in GaN. The defect concentrations for the Ga(0.9375)Ca(0.0625)N under thermal equilibrium N-rich and N-realistic growth conditions are also discussed, respectively. The calculations show that defect concentration under N-rich condition can readily reach 7%, while under N-realistic growth condition, the maximum defect concentration is as low as 1.71% when the growth temperature increases to 1100 K (melting point of GaN). These results suggest that it would be a little difficult to achieve ferromagnetic state for Ga(0.9375)Ca(0.0625)N using the chemical-equilibrium fabrication method, such as chemical precipitation. Using the same method as that for Cu-doped ZnO [L. H. Ye et al., Phys. Rev. B 73, 033203 (2006)], the transition temperature of Ga(0.9375)Ca(0.0625)N may be close to room temperature. (C) 2008 American Institute of Physics.
关键词:
generalized gradient approximation;doped zno;gan;semiconductors;calcium;systems;origin
Journal of Applied Physics
The structure and magnetic properties of Nd2Fe14BNdelta-based alloys prepared by mechanical alloying have been investigated. For the Nd14Fe78B8Ny series, a large amount of NdN, alpha-Fe, and a small Nd2Fe14B phase are observed in x-ray diffraction patterns. With increasing Nd content, the amount of the Nd2Fe14BNdelta phase increases and alpha-Fe decreases gradually. When x greater than or equal to 25 in the NdxFe92-xB8Ny systems, some amount of the N-containing, Nd-rich phase appears. Meanwhile, the content of the nitrogen in the Nd2Fe14BNdelta phase decreases and, correspondingly, the Curie temperature decreases. The coercivity and the maximum magnetic energy product of this series attain maxima at x=25. A coercivity as high as 20 kOe has been achieved. The effect of nitrogen on the formation, composition, and magnetic properties of the Nd2Fe14BNdelta compound is discussed. (C) 2000 American Institute of Physics. [S0021-8979(00)22208-1].
关键词:
phase;sm
