共查询到20条相似文献,搜索用时 15 毫秒
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真空蒸馏方法以其流程短、消耗少、对环境无污染等优点,成为高纯金属,特别是低熔点金属的研究热点和工业生产中的最主要的方法之一.综述了真空蒸馏技术在高纯金属提纯方面的现状与前景,详细介绍了真空蒸馏技术的分馏机理和影响因素,包括饱和蒸气压、分离系数和蒸发速率3个方面对真空蒸馏提纯效果和效率的影响.介绍了真空蒸馏技术在高纯金属铋、锑、铟3种低熔点金属制备中的应用,并探讨了采用多种方法联合提纯获得超高纯金属的可行性,通过真空蒸馏与区域熔炼两种方法相结合制备了纯度大于99.999 9 %的超高纯铋. 相似文献
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高效、高灵敏度的原位微区分析技术开发对于固态电迁移等稀土提纯工艺具有重要意义。实验以固态电迁移提纯后金属镝棒为研究对象,将激光剥蚀-电感耦合等离子体质谱法(LA-ICP-MS)应用于高纯稀土金属的微区分布分析。研究了激光剥蚀速率对样品覆盖率和分析时间的影响,确定了剥蚀速率为50μm/s;考察了剥蚀池及ICP-MS载气流量对待测元素信号强度、氧化物产率及元素分馏效应的影响,确定了载气流量分别为0.60L/min(He)和1.0L/min(Ar)。采用线扫描方式,以基体元素~(158)Dy为内标,获得了不同电迁移区域各杂质元素的二维相对强度分布图,初步探究了各杂质元素的迁移规律。结果显示:在电迁移过程中,Al、Si、Ti、Fe、Mo、W元素从阴极向阳极迁移;Ni、Cu元素从中间区域向两极迁移。这一迁移趋势与辉光放电质谱法(GD-MS)分析结果相一致。同时,LA-ICP-MS还得到更丰富的微区统计分布信息。不同电迁移区域各杂质元素最大偏析度、相对标准偏差(RSD)值及最大偏析位置进一步揭示了各元素的迁移状态,可能与固态电迁移工艺相联系。因此,LA-ICPMS有望为稀土金属提纯工艺解析及优化提供一种新的有效分析手段。 相似文献
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N. M. Gorey D. A. Koss J. F. Hellmann 《Metallurgical and Materials Transactions A》1998,29(5):1499-1507
Fiber fragmentation is a problem frequently encountered during the processing of metallic matrix composites. In this study,
we examine the fragmentation of continuous fibers during a common composite consolidation process based on hot pressing in
an open-ended channel die with fibers aligned parallel to the die walls. During the latter stages of consolidation, flow of
the matrix along the die cavity may occur such that the resulting load transfer to the fibers can cause their fracture even
in the absence of bending. This study analyzes the combination of conditions necessary for both matrix flow along the die
cavity and the shear-lag loading of the fibers to a level that causes fragmentation. In order to validate the analysis, we
model the fragmentation of fibers during elevated temperature hot pressing of Ni-base composites by the room-temperature consolidation
of degraded sapphire fibers in a tin matrix. The observed fiber fragmentation behavior is in good agreement with theoretical
predictions. The analysis also indicates that this mode of fiber fragmentation is confined either to low volume-fraction fiber
composites or to the ends of panels of high volume-fraction fiber composites. 相似文献
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R. H. Hopkins 《Metallurgical and Materials Transactions B》1974,5(5):1183-1188
The primary recrystallization of dysprosium can be characterized by an apparent activation energy of 13.4 ±1.4 kcal/mole when
specimens are isothermally annealed at temperatures between 400 and 600°C. At temperatures between 300 and 400°C recrystallization
is strongly retarded, possibly by precipitation, and the activation energy associated with the process is increased to 31.4
±4 kcal/mole. The deformation texture of dysprosium sheet following a cold reduction of 50 pct can be described as (0001)<1010>
with a rotational spread of 15 to 20 deg about the rolling direction. Annealing the rolled sheet produces a recrystallization
texture which is composed of two components related to the deformation texture by 27 deg rotations about a common 1010 direction.
Within the scatter of the data this texture can be represented by the ideal orientation l5l6 (1010). 相似文献
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为了降低金属镝中的钙含量,对真空精炼时间,真空度,精炼温度的控制找出了合理的工艺条件,提出了产品质量。 相似文献