T.S.Ke (Tingsui GE)(Lab. of Internal Friction and Defects in Solids
,
Institute of Solid State Physics
,
Chinese Academy of Sciences
,
Hefei 230031
,
China)
材料科学技术（英文）
In the seventies some scientific workers from France and ltaly suggested that the grain boundary internal friction peak (named the Ke peak in the literature) widely accepted as a grain bound ary process, is originated from the motion of lattice dislocations. Since this problem is one of fundamental importance, this controversy has drawn much international attention. Started from 1982, the Hefei research group made a critical analysis of the large amount of literature concerning this problem and performed a series of crucial experiments to clarify the controversy It is concluded that the irrelevant evidence suggested by the controverters comes from the farfetched interpretation and the mis-identification of the internal friction peaks appeared under various experimental conditions and different states of the specimens.
关键词:
许传龙
,
王式民
工程热物理学报
在加压密相气力输送实验装置上获得了不同操作条件下煤粉颗粒静电波动信号,并用Hilbert-Huang变换、功率谱进行分析.结果表明:随着表观速度的增加,静电波动信号主峰值的频率增大;静电波动信号希尔伯特-黄变换(Hilbert-Huang)揭示了气固两相流静电信号的非线性和非平稳特征,随气固两相流颗粒相浓度降低和颗粒及表观速度增加,静电波动信号特征尺度由高尺度(低频)向低尺度(高频)转移.多尺度分析有助于认识气固两相流动形态及其转变规律.
关键词:
颗粒静电
,
静电传感器
,
气-固两相流
,
Hilbert-Huang变换
中国腐蚀与防护学报
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关键词:
Materials Science and Engineering a-Structural Materials Properties Microstructure and Processing
Monocrystalline copper samples with [001] and [221] orientations were subjected to shock/recovery experiments at 30 and 57 GPa and 90 K. The slip system activity and the microstructural evolution were investigated. Different defect structures, including dislocations, stacking faults, twins, microbands, and recrystallized grains were observed in the specimens. The residual microstructures were dependent on crystalline orientation and pressure. The differences with crystalline orientations are most likely due to different resolved shear stresses on specific crystalline planes. The geometric relationships between the shock propagation direction and crystalline orientation are presented under uniaxial strain. It is shown that the [2 2 11 orientation, by virtue of having fewer highly activated slip systems, exhibits greater concentration of deformation with more intense shear on the primary system. This, in turn leads to greater local temperature rise and full recrystallization, in spite of the thermodynamic residual temperature of similar to 500 K and rapid cooling (within 20 s) to ambient temperature. The profuse observation of microbands is interpreted in terms of the mechanism proposed by Huang and Gray [J.C. Huang, G.T. Gray III, Acta Metallurgica 37 (1989) 3335-3347]. (C) 2009 Elsevier B.V. All rights reserved.
关键词:
Shock compression;Shock loading;Slip bands;Microtwins;Microbands;strain rate history;single-crystals;grain-size;constitutive;description;plastic-deformation;mechanical response;deformed metals;loaded nickel;substructure;recrystallization
Physical Review B
An elastic Ising model for CoMnO(6) chain is proposed to explain the ferroelectricity induced by collinear magnetic order in Ca(3)CoMnO(6), and then a mean-field theory with interchain spin interactions based on this model is developed. With inclusion of the dynamics of polarization domains at finite temperature, we address the rationality of our theory by the good agreement of the calculated electric polarization and dielectric susceptibility with the reported data on Ca(3)Co(2-x)Mn(x)O(6) (x approximate to 0.96) [Y. J. Choi, H. T. Yi, S. Lee, Q. Huang, V. Kiryukhin, and S.-W. Cheong, Phys. Rev. Lett. 100, 047601 (2008)], a typical diatomic Ising spin chain system, while the predicted magnetic susceptibility shows some difference from experiment, the reason of which is discussed.
关键词:
calcium compounds;cobalt compounds;dielectric polarisation;ferroelectricity;Ising model;magnetic susceptibility;multiferroics;optical susceptibility;one-dimensional oxides;magnetic-properties;multiferroics;ca3co1+xmn1-xo6
Physica B-Condensed Matter
Polycrystalline La0.5Lu0.2Sr0.3MnO3 samples prepared by thermal decomposition are investigated by means of electron diffraction and high-resolution transmission electron microscopy. Besides rhombohedral La0.7Sr0.3MnO3 phase (R-phase) and hexagonal LuMnO3 phase (H-phase) reported by Huang, unexpectedly, an orthorhombic lattice (O-phase) with space group Pnma is observed in the interior of R-phase grain. The lattice parameters of the orthorhombic unit cell are a(o) = 5.44 angstrom, b(o) = 7.65 angstrom and c(o) = 5.48 angstrom The formation of O-phase results from a(-)b(+)a(-) type orthorhombic distortion of MnO6 octahedra induced by partial substitution of Lu3+ for La3+. Meanwhile, based on image simulation of the interface between R and O-phases, the atomic bonding on the interface is particularly discussed. (c) 2005 Elsevier B.V. All rights reserved.
关键词:
orthorhombic lattice;octahedral;substitution;atomic bonding;la0.7-xluxsr0.3mno3 perovskites;transport-properties;magnetoresistance;films
Materials Letters
Phase separation and microstructure of La0.7Sr0.3MnO3 doped with rare earth elements (Eu, Ho, Yb and Lu) are studied using X-ray diffraction (XRD) and transmission electron microscopy (TEM). Composition and diffraction analyses demonstrate that the ionic radius of doping element plays an important role in the crystalline structure and the lattice constants of the secondary phase. When La 3 is replaced partly by Eu3+ or Ho3+, orthorhombic perovskite structure with space group Pnma is formed due to the distortion Of MnO6 octahedra. Different from the phenomenon observed by Huang et al., however, the hexagonal non-perovskite structure (YbMnO3 and LuMnO3) has appeared when La3+ and Sr2+ are substituted completely by Lu or Yb (c) 2005 Elsevier B.V. All rights reserved.
关键词:
ionic radius;crystalline structure;lattice constants;orthorhombic;perovskite;hexagonal non-perovskite;magnetoresistance;perovskites;films
