O.I.Shpigunova
,
S. V. Shpigunov
,
Yu.N. Saraev (Institute of Strength Physics and Materials Science
,
Siberian Branch
,
Russian Academy of Sciences
,
Tom- sk
,
Russia)
金属学报(英文版)
In this paper the processes of melting and transfer of an electrode metal to the molten pool, hydrody- namics of molten pool in controlled pulsed arc welding in carbon dioxide have been investigated.The process of pulsed arc welding with systematic short - circuits of the arc gap is realized by adaptive algo- rithms of pulsed control over main energetic parameters of welding - arc current and voltage,arc heated efficiency,peak,short - circuiting current, which provide the dosage of energy for energy for melting and transfer of every for of an electrode metal, the control over fluidity of the weld pool. Physica and mathematical models describing such processes in CO2, origind software hare been developed.The re- sults of physical simulation and mathemaical modelling permit to determine the influence of energetic parameters of the process on the condition of the "power source-electrode-arc-molten pool" electrodynamic system at each moment of time.
关键词:
pulse
,
null
,
null
,
null
王华
,
李岩
功能材料
采用溶胶-凝胶工艺(Sol-Gel)在Pt/Ti/SiO2/p-Si衬底上成功制备了低漏电流Bi4Ti3O12(BIT)铁电薄膜,对所得样品的漏导行为进行了研究.研究表明,Bi4Ti3O12薄膜的漏电流密度在+3V偏压下低于10-9A/cm2,满足器件应用的要求.在不同场强下薄膜的漏导机制不同,而且正向和负向电场作用下I-V曲线明显不同,正向漏电流明显小于负向漏电流.电压低于2V时,薄膜以欧姆导电机制为主,电压在2～5.4V(加正向电压)或2.2～3.6V(加负向电压)时,BIT薄膜应以Schottky emission导电机制为主;而对于较高的场强下,BIT薄膜以Space-charge limited currents(SCLC)导电机制为主.
关键词:
铁电薄膜
,
Bi4Ti3O12
,
漏导机制
,
I-V特性
Physica Status Solidi B-Basic Research
The perturbation formulas of EPR g factors g(\\) g(perpendicular to) and hyperfine structure constants A(\\) A(perpendicular to) for the trigonal octahedral 3d(7) cluster are derived considering not only the configuration interaction effect due to the admixture among ground and excited states, but also the covalency effect due to the admixture between the d electrons of the 3d(7) ion and the p electrons of ligands. In these formulas, the parameters related to both effects and the trigonal field parameters are estimated from the optical spectra and the structural parameters of the studied system. According to these formulas, the EPR parameters g(\\), g(perpendicular to), A(\\) and A(perpendicular to) for Co2+ in the octahedral sites of Y3Al5O12 and Y3Ga5O12 garnets are satisfactorily explained from the optical spectra and the structure data. The role of the covalency effect is discussed.
关键词:
superposition model;phase-transition;absorption;linbo3;ions
徐国跃
,
马立新
,
谢国治
,
骆心怡
功能材料
制备的ZnO/Co2O3敏感电阻单元材料同时具有伏安(V-I)非线性特性及负温电阻(NTC)效应.两种效应的形成与烧结过程900℃热处理温度密切相关.差热分析(DTA)曲线表明:Co2O3在904℃有一相变吸收峰.在该温度点保温热处理的ZnO/Co2O3敏感电阻单元材料获得相对大的伏安非线性和NTC效应.电子自旋共振谱(ESR)证明,Co离子由烧结热处理前的Co3+价变成热处理后的Co2+价,其中最大敏感电阻和伏安非线性参数样品与最强Co2+离子ESR信号对应.变温过程ESR动态观察显示,Co2+与Co3+可逆变换,说明被Co2+离子束缚的电子存在禁锢与脱离的可逆过程.这是ZnO/Co2O3敏感电阻单元材料在电场、热场下产生V-I非线性及NTC效应的基础.
关键词:
ZnO
,
压敏陶瓷
,
V-I非线性
,
NTC效应
Journal of Physics and Chemistry of Solids
By using the defect structure data (characterized by the coordinates of impurity center) obtained from the shell model and the density functional theory in the generalized gradient approximation (GGA) corresponding to two supercell sizes, the zero-field splitting D of the tetragonal Fe-K(3+)-O-I center in KTaO3 crystal is calculated from the high-order perturbation formula based on the dominant spin-orbit coupling mechanism. The calculated results suggest that the sign of zero-field splitting D is negative and the defect structure data obtained from GGA method are more reasonable. Compared with that corresponding to the smaller supercell size, the calculated D value based on the GGA coordinates corresponding to the larger supercell size is closer to the observed value, suggesting that the GGA coordinates obtained from the larger supercell size are more accurate. (c) 2006 Elsevier Ltd. All rights reserved.
关键词:
inorganic compounds;oxides;crystal fields;defects;electron;paramagnetic resonance (EPR);fe centers;ions;scattering;spectra;sites;model;epr
王杭栋
,
万海洋
,
林杨帆
,
方明虎
低温物理学报
doi:10.3969/j.issn.1000-3258.2004.03.007
自今年3月在NaxCo2O4+Yh2o中发现超导电性以来,具有层状结构的Co系氧化物又受到人们广泛的关注.本文在成功合成具有misfit层状结构Bi2Sr2Co2Oy单相样品的基础上,通过Pb对Bi的部分替代、以及I的插层,成功地使其c轴由1.49nm增至1.87nm,并对其输运性质和磁性质进行了系统研究.结果发现:Pb的部分替代并没有使该体系的电阻-温度关系行为发生显著变化,但在低温下使样品呈现自旋玻璃态行为;I的插入不仅使其c轴长度增加,而且样品变为半导体,并不呈现超导电性,在低温下同样呈现自旋玻璃态行为.同时对Pb替代及I插层效应进行了讨论.
关键词:
钴氧化物
,
自旋玻璃
,
过渡性金属氧化物
Surface & Coatings Technology
Nanocrystalline Cr2O3 thin films were deposited on silicon wafers with (100) orientation by arc ion plating (AIP) technique at various negative bias voltages. By virtue of X-ray diffraction analysis, scanning electron microscope, and high-resolution transmission electron microscope, the influence of substrate bias voltage on the film growth process, microstructure, and characteristics was investigated systematically, including the phase constituents, grain size, lattice constant, chemical compositions, as well as surface and cross-section morphologies. With increasing the bias voltage, the grain size and lattice constant of AIP Cr2O3 films first decreased slightly, and then increased gradually again. Both reached the minimum (35 nm and 13.57 angstrom) when the bias voltage was - 100 V. However, the bias voltage had little effect on the phase constituents and chemical compositions of AIP Cr2O3 films. During the film growth process, the surfaces of Cr2O3 films were getting smoother with the negative bias voltage increase, in the meantime, their microstructures evolved from coarse columnar grains to fine columnar grains, short columnar recrystallized grains, and fine columnar grains again. (C) 2011 Elsevier B.V. All rights reserved.
关键词:
Cr2O3 film;Arc ion plating;Bias voltage;Grain size;Surface;morphology;HRTEM;chromium-oxide coatings;pulsed-laser deposition;negative bias voltage;si-n coatings;thin-films;mechanical-properties;optical-properties;nitrogen pressure;vapor-deposition;residual-stress
彭晓
,
王福会
,
D.R.
,
Clarke
金属学报
磁控溅射Co-Cr-Al(Y)纳米涂层在1000, 1100和1200℃氧化一定时间后, 用光激发荧光谱技术表征热生长的Al2O3相. 发现氧化层局部区域存在由非稳态相向稳态相的转变, 即: γ→θ→α; 其转变过程随温度升高显著加快, 并在1200℃下变昨不明显. 在相同温度下, Y明显减缓Al2O3相转变过程.
关键词:
光激发荧光谱术
,
null
,
null
彭晓
,
王福会
,
D.R.Clarke
金属学报
用光激发荧光谱术分析测量磁控溅射Co-Cr-Al(Y)纳米涂层经1000, 1100和1200℃氧化后Al2O3膜中的残余应力, 获得如下结果: (1) 残余应力随氧化温度升高而增大; (2) 暂态氧化出现的区域应力值明显低于无暂态氧化的区域; (3) 两种涂层1000℃下形成的氧化膜中的残余应力相差不大, 但在1100℃和1200℃下, 含Y涂层形成的氧化膜中的残余应力比不含Y中的高. 对实验结果进行了分析.
关键词:
光激发荧光谱术
,
null
,
null
