共查询到20条相似文献,搜索用时 109 毫秒
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《低温与超导》2015,(10)
对S30408奥氏体不锈钢进行室温应变强化,在深冷温区(77K~4.2K)进一步时效处理,利用金相显微镜、X射线衍射仪(XRD)和透射电子显微镜(TEM)研究了应变诱发和热诱发马氏体相变的微观特征,探讨了马氏体相变的微观机理。结果表明:马氏体相变的含量、微观形貌、形核特征和位错组态随着预应变量的增加和温度的降低而改变,且应变强化比温度对相变的影响要大。诱发马氏体与母相奥氏体的位相关系符合K-S关系,其相变的微观机理为γ(fcc)→ε(hcp)、γ(fcc)→α'(bcc)、γ(fcc)→ε(hcp)→α'(bcc)、γ(fcc)→形变孪晶→α'(bcc)。 相似文献
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对S30408奥氏体不锈钢进行室温应变强化,在深冷温区(77K^4.2K)进一步时效处理,利用金相显微镜、X射线衍射仪(XRD)和透射电子显微镜(TEM)研究了应变诱发和热诱发马氏体相变的微观特征,探讨了马氏体相变的微观机理。结果表明:马氏体相变的含量、微观形貌、形核特征和位错组态随着预应变量的增加和温度的降低而改变,且应变强化比温度对相变的影响要大。诱发马氏体与母相奥氏体的位相关系符合K-S关系,其相变的微观机理为γ(fcc)→ε(hcp)、γ(fcc)→α'(bcc)、γ(fcc)→ε(hcp)→α'(bcc)、γ(fcc)→形变孪晶→α'(bcc)。 相似文献
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本文对液氮温区的大块体超导材料的约瑟夫逊效应进行了实验研究.我们证实在未加工成任何弱连接形式的体超导材料上也会观察到约瑟夫逊效应.这对于搞清液氮温区超导材料的特性及其应用都具有一定的参考价值. 相似文献
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本文以实验为基础,简要而系统地介绍了氧化物高温超导YBCO体系中超导体YBa2Cu3O7-δ材料的实验室生产过程 相似文献
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激光诱导击穿光谱(LIBS)是近十几年来快速发展的一种新的表面分析工具,由于具有分析速度快、灵敏度高等优点,故在材料科学领域引起广泛的关注。文中采用LIBS、扫描电子显微镜/能谱仪(SEM/EDS)和电子探针显微分析(EPMA)三种分析方法,对两类不同焊缝的熔合线区域进行线扫描分析,研究了Ni,Mn,C,Si等元素在熔合线区域含量的变化情况。结果表明,对于含量较高且焊缝和母材成分差别较大的Ni和Mn元素,三种方法获得了一致的分析结果,两试样焊缝内的Ni和Mn含量均高于母材,在熔合线区域明显体现出浓度梯度分布。三种方法根据Ni和Mn的浓度分布测得的熔合线区宽度值比较接近。对于含量较低且焊缝和母材成分差别较小的C和Si元素,采用SEM/EDS和EPMA时,焊缝与母材之间的成分差异没有分析出来;而采用LIBS时,两区域的成分差异则可以清晰的展现出来,在熔合区域能够清楚观察到浓度梯度分布曲线。LIBS的分析灵敏度明显高于SEM/EDS和EPMA,在分析低含量元素时更具优势。 相似文献
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Thermodepolarizing current spectra for components of mica-based insulating composites are presented. The variation of the thermograms with experimental conditions is revealed. The data reported are the initial results of elaborate measurements in this area and can be used in devising new insulating materials and new methods for the quality control of insulators. 相似文献
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分析了深燃LNG工艺低温绝热技术的应用情况,并就LNG工厂中使用的几种低温绝热材料及结构型式作了介绍,对今后LNG工艺设计具有一定参考作用。 相似文献
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A review of measured breakdown properties in insulating films and of electronic theories of breakdown shows both theoretical and experimental inconsistencies. A theory is proposed in which electronic breakdown is caused by local chance events, such as a succession of avalanches at one spot. Successive avalanches sustain the growth of space charges, the local cathode field, and the avalanche rate. When the cathode field becomes large enough to make continuation of avalanching a certainty, instability with current runaway arises, causing breakdown. According to theory, breakdowns occur over a range of fields, their chance increasing very strongly with field; the breakdowns occur randomly in space and in time; the time to instability on a breakdown event decreases as some exponential function of increasing field; the breakdown field can both increase and decrease with temperature; it may be electrode dependent, and it decreases first rapidly and then more slowly with increasing film thickness. Observations made in a number of insulating films support the proposed theory. 相似文献
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随着超导技术的迅速发展,高温超导电力设备的工作温度已经可以控制在液氮温度附近,绝缘材料的电气特性是影响电力设备工作性能和运行可靠性的重要因素。聚酰亚胺由于其优异的电气性能和力学性能,广泛应用于常温下电力设备绝缘,而其作为低温绝缘材料应用的研究目前鲜有报道。因此,在液氮温度下聚酰亚胺的绝缘性能研究具有十分重要的意义。文中选取室温附近(300K)和液氮温度(78K)两个温度点,对聚酰亚胺的直流击穿性能和沿面闪络特性进行了测试。研究结果表明温度对聚酰亚胺绝缘材料的直流击穿场强和沿面闪络强度均有一定影响。 相似文献
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Yuanxiang Zhou Qinghua Sun Ninghua Wang Yunshan Wang 《Journal of Electrostatics》2009,67(2-3):426-429
Polyethylene is widely used in electrical wires and power cables. The pre-stressing effect, which restricts the applications of polyethylene, has not yet been investigated in depth. We studied the breakdown of low-density polyethylene (LDPE) films pre-stressed by direct current (DC) electric field. The results showed some conformity, as reported in many other papers, that the DC breakdown strength EB+ with the same polarity to that of the pre-stressing field was higher than the DC breakdown strength EB of thin LDPE films without pre-stressing, while the DC breakdown strength EB? with the opposite polarity was lower than EB. Such phenomena could be explained by the hetero effects of accumulating space charges, which enhanced the electrical field when the polarity was reversed. However, as a further increase in pre-stressing electrical field, both EB+ and EB? were found higher than EB. We investigated the space charge behavior in LDPE films and found that when applied with a higher electrical field, space charge packet initialized and traveled through the specimen. The results suggest that the space charge packet behavior may contribute to the pre-stressing effects on electrical breakdown in LDPE films. 相似文献
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《Comptes Rendus de l''Academie des Sciences Series IV Physics》2001,2(5):761-774
Electrical charge generation occurring during contact and friction of insulating materials has long been identified. However the contribution of these electrical charges to the frictional behaviour is usually neglected. Based on published results and on our own experimental work on the ability of the dielectric materials to trap charges, we show in this study that the interaction energy during friction depends markedly on these trapped charges. Eventually, we propose the complementary use of the ‘mirror’ method and of surface force measurements to obtain a quantitative evaluation of this contribution. 相似文献
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Zoltán ádám Tamus 《Journal of Electrostatics》2009,67(2-3):154-157
The possible use of insulating materials is basically determined by their electrical properties (i.e. resistivity, dielectric strength) in many new technologies in several branches of the industry. The application of these materials is strongly determined by the physical and chemical properties resulting from the material structure. During lifetime many chemical processes start up in the material (e.g. decreasing of the content of the additives, breaking of polymeric chains) and the molecular structure of material is altered. The changes are reflected in the physical properties and it can dramatically decrease the applicability of the insulating materials. According to the complexity of the materials and the complexity of the stresses the changing of material properties can only be precisely investigated by complex diagnostic measurements.The use of complex investigation (parallel electrical, chemical, mechanical examinations) of insulating materials is introduced in the paper. Based upon the complex insulation diagnostics and the resulted database of different insulating materials to be applied in industrial electrostatics the possible use of complex non-destructive insulation diagnostics is drawn for practical purposes. 相似文献
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A. Mahesh Kumar M. Chaitanya Varma G.S.V.R.K. ChoudaryP. Prameela K.H. Rao 《Journal of magnetism and magnetic materials》2012,324(1):68-71
The study of gadolinium substitution in small amounts on the saturation magnetization and DC resistivity of nickel-zinc nanoferrite has led to the understanding of the degree of formation of a secondary orthoferrite GdFeO3 phase, the generation of cationic and oxygen vacancies and the dilution of gadolinium in the lattice. The role of secondary phase in modifying the electromagnetic properties has been stressed by making further investigations on the Curie temperature and the activation energies. 相似文献