Al在无取向电工钢晶粒长大过程中对织构及晶界变化的影响

研究了含Al和不含Al的无取向电工钢在晶粒长大过程中织构转变及晶界变化的规律。结果表明,晶粒长大过程中电工钢的主要织构组分均为{111}〈112〉。在晶粒生长期间,不加Al的电工钢中{111}〈112〉、{111}〈110〉织构组分强化,而{100}〈001〉织构组分弱化。与不加Al的钢相比,加Al后,{111}〈112〉、{111}〈110〉织构组分强化的速率下降,{100}〈001〉织构组分变化不明显,甚至稍有增加。对于在晶粒生长期间持续变化的{111}〈112〉、{111}〈110〉和{100}〈001〉织构组分而言,{111}〈112〉和{111}〈110〉织构组分的低取向差角度晶界频率上升,而{100}〈001〉织构组分的低取向差角度晶界频率下降,但加入Al后,这些织构组分的低取向差角度晶界频率下降的速率明显变小。     

Grain Boundary Defect Chemistry of Acceptor-Doped Titanates: High Field Effects

The field enhanced average conductivity in grain boundary space charge depletion layers in acceptor-doped SrTiO₃ ceramics was investigated by impedance analysis in the time domain. The dependence of the grain boundary conductivity on the acceptor concentration, the temperature and the field dependence are discussed and interpreted in terms of a Schottky diffusion model combined with the influence of accumulated oxygen vacancies at the GB interface.     

PTCR Effect in BaTiO3: Structural Aspects and Grain Boundary Potentials

Extensive microstructural and structure-property studies on donor doped barium titanate have revealed that the PTCR phenomenon is strongly controlled by the density, number of grain boundaries available to conduction, domain orientation and grain boundary domain coherence. Structural heterogeneities lead to a wide range of grain boundary structures, potential barriers and, therefore, depletion widths. Conduction thus occurs primarily by percolation of electrons through favorably aligned domain pathways and low potential barrier grain boundaries. At the Curie point, the increase in the potential barriers along these pathways is likely to dominate the PTCR effect. To improve theoretical understanding a model needs to take heed of local values of parameters and also incorporate the fact that the bulk of the current flow is only through a certain percentage of grain boundaries. The specific structural factors that have led to an improved qualitative understanding of overall PTCR phenomenon are discussed.     

Relation Between Firing Conditions Grain Boundary Structure and Magnetic Properties in Polycrystalline MnZn-Ferrites

The influence of the firing conditions on the nanoscale structure of the grain boundaries and on the magnetic properties of polycrystalline MnZn-ferrites is investigated, on specimens of nearly identical microstructures. High oxygen partial pressures favor accumulation of impurity ions at the triple points. Under appropriate oxygen pressures homogeneous accumulation of impurities along the grain boundaries may occur, revealing therefore chemically pure grains and low hysteresis losses; simultaneously an increase of the grain boundary resistivity occurs that results to low eddy current losses. Managing the raw material impurity cations towards controlled grain boundary structures leads to the synthesis of MnZn-ferrites with power losses similar to those achieved when high purity raw materials are used together with externally introduced additives.     

Investigations on KTN thin films by XRD,XPS and micro raman spectroscopy

Abstract

The renewed interest in KTa_1?xNb_xO (KTN) mixed perovskite materials, especially in thin films of a high quality, is connected with their remarkable dielectric properties in the dilute compositions. Off-center Nb ions in the highly polarizable KTaO₃ lattice provide a drastic increase in the dielectric peak up to 20 times in comparison with pure KTaO₃ and KNbO₃. This paper reports a continuation of KTN thin films studies with several Nb concentrations in the range of 0 ≤ x ≤ 1 prepared by pulsed laser deposition from segmented KTaO₃, KNbO₃ and KNO₃ targets. The effect of the substrate and symmetry-breaking defects was studied by micro-Raman spectroscopy. An anomalous residual intensity of the forbidden first-order scattering modes in the cubic paraelectric phase of the KTN films was connected with the formation of polar microregions even far above the bulk T_c value. On the whole, the KTN film behavior shows the existence of specific defects enlarging the perovskite unit cell in the film so that the activity of off-center Nb ions increases in producing larger electric dipoles and extending the precursor phase above T_c.     

Preparation and Characterisation of High Density, High Purity Lanthanum Aluminate Bulk Ceramics

In this work some methods for preparation of lanthanum aluminate bulk ceramics were compared. High purity lanthanum aluminate LaAlO₃ (LAO) ceramic samples of high density (>94%) were prepared via three different routes and the morphology, chemical and electrical properties of the samples were investigated. For high purity samples a sol-gel route A. Douy and P. Odier [1] and a thermal nitrate decomposition route Shaji Kumar et al. [2] were introduced to reduce unintentional doping by the preparation process to a minimum. As a standard route the mixed oxide process was chosen. In sol-gel and nitrate decomposition procedures the formation temperature of LaAlO₃ from its oxides was lowered by using reactive -alumina from the pyrolysis of initial aluminium nitrate instead of commonly used -alumina (corundum) in the mixed oxide process. No commercial -alumina of sufficient purity is known.Differences in the electrical behaviour of the samples were measured, indicating some correlations between the samples' different morphology, purity and its' preparation parameters.     

Control of the Grain Boundary Electrical Features of the Semiconducting SrTiO3 Ceramics Synthesized from Surface-Coated Powders

Polycrystalline SrTi_0.99Nb_0.01O₃ (STNO) ceramics were synthesized by hot-press sintering Na-coated semiconducting STNO powders. The chemical and electrical characteristics of the grain boundary of the ceramics were investigated, and their relations were discussed in terms of process parameters. The diffusion coefficients as well as the activation energy of the Na ions near the grain boundary were obtained at particular heat-treatment conditions; it was demonstrated that these values can be used to design specific electrical features of the grain boundary. A systematic variation in the electrical characteristics of the grain boundary with process parameters was observed; it indicates that this synthesis method can be used for fine control over the chemical and electrical properties of the semiconducting ceramics.     

TEM,XRD和EIS在PEMFC基础研究中的应用

对利用TEM和XRD研究PEMFC中的Pt/C电催化剂以及合金催化剂的物理性能 ,利用EIS研究MEA中PTFE和Nafion含量的影响、电荷传递反应动力学和扩散动力学以及水迁移和水管理的情况、进展和问题进行了评述。最后探讨了可用于PEMFC基础研究的若干新方法。     

基于容量边界与电压边界的潮流模型选择方法

在对配电网安全域(DSSR)、供电能力以及安全分析进行建模时,针对直流潮流模型选择缺乏量化依据问题,提出了基于容量边界与电压边界的潮流模型选择方法.首先,在DSSR交流潮流模型基础上,提出了容量边界和电压边界的概念.其次,基于馈线长度变化时二者的位置关系寻找临界长度,即容量约束或电压约束主导的分界点.若馈线长度小于主导分界点确定的临界长度,则容量约束更严格,可采用直流潮流模型;反之,电压约束更严格,应采用交流潮流模型.最后,针对中国城市、城镇和乡村配电网,计算得到不同导线型号、功率因数和调压措施的临界长度参考值.同时给出了导则中5类供电区域的潮流模型选择建议.     

Structure and Electrical Properties of Ni-substituted Lanthanum Gallate Perovskites

Crystal structure, electrical conductivity and thermal expansion of materials in the system La_0.9Sr_0.1Ga_1–yNi_yO₃ (LSGN) with 0 < y 0.5 have been studied as a function of Ni content, temperature and P_{o 2}. The materials have an orthorhombic structure at low dopant content and a hexagonal structure for higher Ni content. The (P_{o 2}, T) results show increasing electronic conductivity at high P_{o 2} with increasing Ni content. At low P_{o 2} the conductivity fits a model for predominant ionic conductivity. AC impedance spectroscopy on an electron blocking cell of the form M/LSG/LSGN/LSG/M was used to isolate the ionic conductivity in the y=0.1 and 0.2 materials. The materials were found to have appreciable ionic conductivity in air with a similar magnitude and activation energy to the electrolyte materials. An analysis of the low frequency impedance of the blocking cell provided values for D at 800°C of the order of 9 × 10^–5 cm²/s. An evaluation of the so called chemical capacitance enabled determination of the electron density and mobility. The calculated electronic mobility of 3.8 × 10^–3 cm²/Vs and activation energy of 0.14 eV for the y = 0.2 material are in excellent agreement with expectations of an electronic transport model involving electron hopping within the Ni impurity band. The thermal expansion coefficients of the Ni doped materials were determined as a function of temperature and dopant level. The presence of mixed conductivity suggests that this material may be useful as an electrode for a lanthanum gallate based fuel cell or other electrochemical device.     

基于横电磁波天线的高空核电磁脉冲辐射波模拟器设计

为解决传统核电磁脉冲模拟器存在测试空间受限的问题,提出了基于横电磁波（TEM）喇叭天线的高空核电磁脉冲辐射波模拟器设计方案。通过数值仿真验证了TEM喇叭天线的辐射场波形,指出TEM喇叭天线在应用于辐射式电磁脉冲模拟器时存在低频辐射能力差的问题;通过比较TEM喇叭天线对3种典型核电磁脉冲的辐射能力,发现辐射场的上升沿部分主要取决于激励源的上升前沿陡度,辐射场的脉冲宽度与激励脉冲的宽度有关,可以通过展宽激励源脉冲宽度的方法来补偿TEM天线低频辐射能力差的问题;通过实验验证了利用TEM喇叭天线研制电磁脉冲辐射波模拟器的可行性,但仍需要阻性加载或展宽激励脉冲等方法对TEM喇叭天线的低频辐射性能进行改善。     

电力系统潮流可行域边界拓扑性质及边界算法

电力系统潮流可行域是一种评估系统静态安全的有效手段.文中探讨了不同子空间的潮流可行域边界的拓扑性质,提出了新的边界算法.首先,在把潮流可行域划分为负荷注入子空间与发电注入子空间的基础上,通过大量算例发现2个子空间的可行域边界具有截然不同的拓扑特性,特别是发电注入空间的潮流可行域边界在系统实际可能的运行范围内呈现较好的线性特性.然后在混合法的基础上,提出一种新的高维发电注入空间中潮流可行域L1范数最远边界点算法,该算法避免了频繁启动连续潮流计算,其结果的多解性也被用来进一步检验潮流可行域边界拓扑性质.     

粮食除湿杀菌处理及长期存储自动控制系统的研究

通过对粮食加工处理及长期存储工艺过程的研究和设计,开发了粮食除湿杀菌杀虫处理及长期储存自动控制及监控系统,该系统应用可以提高粮库粮食仓储的成品率和保鲜度,减少陈化粮对人民身体的危害,同时提高粮库仓储的自动化水平。     

节能型交流变频调速实验系统及节能效果分析

提出一种交流电动机作为模拟负载的变频调速实验系统及一种新型频差控制方法,对系统的运行原理及节能效果进行了分析,实验结果表明该系统的可行性及明显的节能效果.     

New design and development of size‐selected gas cluster SIMS

A new cluster time‐of‐flight secondary ion mass spectrometry (TOF‐SIMS) was developed, using a size‐selected gas cluster ion as a projectile. Because a large gas cluster ion can generate numerous low‐energy constituent atoms during a collision with the surface, multiple and ultralow‐energy sputterings are induced. Dividing the acceleration energy of a gas cluster ion by the number of constituent atoms provides the mean kinetic energy of the constituent atoms. Hence, sputtering can be controlled to minimize decomposition of the sample molecules by precisely adjusting the number of constituent atoms (the cluster size) and/or the acceleration energy of the gas cluster ions. The cluster size was selected by the time‐of‐flight method using two ion deflectors attached along the ion‐beam line. A high resolution of 11.7 was achieved for the cluster size/size width (m/Δm) of the Ar‐cluster ions. The SIM spectra of poly(methyl methacrylate) (PMMA) were measured using the size‐selected gas‐cluster SIMS machine. The large fragment ions emitted from PMMA are enhanced as the cluster size increases. This result suggests that a large cluster ion projectile in which each constituent atom within the cluster has decreased kinetic energy inhibits the decomposition of the polymer structure. © 2011 Wiley Periodicals, Inc. Electr Eng Jpn, 176(3): 52–58, 2011; Published online in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/eej.21159     

节能型交流变频调速实验系统及节能效果分析

提出一种交流电动机作为模拟负载的变频调速实验系统及一种新型频差控制方法 ,对系统的运行原理及节能效果进行了分析 ,实验结果表明该系统的可行性及明显的节能效果     

基于双倒易边界元法的非稳态导热几何边界识别

采用基于双倒易边界元法和共轭梯度法的反演算法求解二维非稳态导热边界识别问题。正问题采用双倒易边界元法求解,该法避免了传统边界元法需进行区域积分的缺点,仅需纯边界积分计算。反问题的解在正问题的基础上通过共轭梯度法最小化目标函数得到。考虑了管道和空腔未知边界为正弦曲线、偏心圆、椭圆等形状时的识别情况,讨论了初值、测量误差和加热热流大小等因素对反演解精度的影响。结果表明,该方法能将各种不规则边界识别出来,对初值和测量误差不敏感,加热热流增大时反演解精度有所提高。     

一种基于边界元离散的导热问题几何边界识别算法

采用基于边界元法和共轭梯度法的反演算法求解二维导热边界识别问题,即几何反问题。正问题采用边界元法求解,反问题的解则在正问题的基础上通过共轭梯度法优化目标函数得到。考虑了未知边界为偏心圆、正弦曲线、椭圆等形状时的识别情况,讨论了初值、测量误差和测量点数等因素对反演解精度的影响。结果表明,该方法能将各种不规则边界识别出来,对初值和测量误差不敏感,测量点数适当减少对反演解精度影响不大,测量点离未知边界越近反演解精度越高。     

TEM Characterization and Raman Spectra of Hydrothermal BaTiO3 Nanoparticles

Microstructures of BaTiO₃ (BT) nanoparticles synthesized by hydrothermal process, were investigated by transmission electron microscopy (TEM) and Raman spectra. TEM images showed that BT nanoparticles synthesized at high Ba/Ti molar ratios in the precursors had large particle sizes and cubic morphology. Small faceted-particles were observed in the BT powders synthesized by using ethylene glycol (EG) as solvent, in comparison to reactive medium of pure water or water-EG mixed solution. X-ray diffraction and selected area electron diffraction revealed that the as-produced BT nanoparticles exhibited a room temperature-stabilized cubic structure, whereas Raman spectra indicated a tetragonal phase BT existing in the produced nanoparticles, which is not the dominant phase due to the weak characteristic peak of tetragonal structure at 305 cm^?1. HRTEM images demonstrated that the BT nanoparticles with either cubic or rectangular shapes, were bounded by their {100} facets, and a terrace-ledge-kink surface structure was frequently observed at the edges of rough nanoparticles. Surface steps lying on the {100} planes were clearly observed. However, in the spherical nanoparticles, their surface edges were very smooth, and no surface steps were observed.