On the evolution of morphology of zirconium sponge during reduction and distillation
On the evolution of morphology of zirconium sponge during reduction and distillation
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DOI：
10.1016/j.matchar.2006.12.015
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发表时间：
2008-03
影响因子：
4.7
通讯作者：
K. Kapoor;C. Padmaprabu;D. Nandi
中科院分区：
文献类型：
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作者：
K. Kapoor;C. Padmaprabu;D. Nandi
高纯度金属锆是通过四氯化锆的镁热还原然后真空蒸馏来生产的。该还原过程是分批进行的，得到还原物质中的金属海绵和氯化镁。海绵经真空蒸馏提纯后可供使用。在还原过程中形成的海绵的形态及其对进一步加工的影响具有重要意义。在本研究中，进行了详细的调查，涉及海绵颗粒的形态及其含义在真空蒸馏过程中的演变。利用扫描电子显微镜和X射线衍射仪对材料的微观结构进行了研究。观察到形成的新生海绵是高度不稳定的，其几乎立即转变为针状形态，其进一步转变为圆形并最终转变为块状形状。在这些颗粒中观察到表面的刻面和针状形成，这可能是由于表面能的各向异性。在还原过程中形成的海绵的形态影响蒸馏过程。细针状海绵形态导致粒子喷射，这是由于曲率效应。这是导致在蒸馏过程中形成不需要的物质的原因。XRD谱线展宽分析表明，单个海绵颗粒没有结构缺陷（位错），并且在性质上几乎是单晶的。
High purity zirconium metal is produced by magnesio-thermic reduction of zirconium tetrachloride followed by vacuum distillation. The reduction process is carried out in a batch giving metal sponge and magnesium chloride in the reduced mass. The sponge is purified to using by vacuum distillation. The morphology of the sponge formed during the reduction and its influence on further processing has significant importance. In the present study, a detailed investigation involving evolution of the morphology of sponge particles and its implication during the vacuum distillation was carried out. The study of the microstructure was done using scanning electron microscopy and X-ray diffraction. It is observed that the nascent sponge formed is highly unstable which transforms to a needle-like morphology almost immediately, which further transforms to rounded and finally to a bulk shape. Faceting of the surface and needle-shape formation were observed in these particles, this is probably due to anisotropy in the surface energy. The morphology of the sponge formed during the reduction influences the distillation process. The fine needle-like shape sponge morphology leads to particle ejection, which is explained to be due to curvature effect. This is responsible for the formation of unwanted mass during distillation. XRD line broadening analysis indicates that the individual sponge particles are free from structural defects (dislocation) and are nearly single crystalline in nature.