Combustion synthesis of MoSi2 and MoSi2–Mo5Si3 composites
Combustion synthesis of MoSi2 and MoSi2–Mo5Si3 composites
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DOI：
10.1016/j.jallcom.2006.08.033
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发表时间：
2007-07
影响因子：
6.2
通讯作者：
C. Yeh;W. Chen
中科院分区：
文献类型：
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作者：
C. Yeh;W. Chen
通过自蔓延高温合成法（SHS）从不同化学计量的元素粉末压块制备二硅化钼（MoSi2）和MoSi2-Mo5Si3复合材料进行了实验研究。本研究采用Mo:Si=6:5、1:1、9:11、3:4、2:3和1:2（对应Si含量在45.5-66.7at.%范围内）六种成分的测试样品。实验证据表明，反应前沿的传播模式、燃烧波速和反应温度受到反应物压块的起始化学计量和预热温度（Tp）的显着影响。在200℃和300℃预热的情况下，Mo:Si=6:5、1:1和9:11的压坯均观察到具有纺丝反应区的自持燃烧，并且检测到反应温度低于Si的熔点（1410℃）。另一方面，Mo:Si=3:4、2:3和1:2的样品在Tp=200和300℃下实现了稳定传播的平面燃烧前沿，并且发现反应温度超过1410℃。然而，在没有预热或Tp=100℃的情况下，平面反应区不再稳定，因此转变为以旋转模式传播的局部反应区。根据 XRD 分析，证实 Mo:Si=6:5、1:1、9:11、3:4 和 2:3 的反应物压块形成了 MoSi2-Mo5Si3 复合材料，但在 Mo:Si=6:5 和 1:1 的情况下发现了大量未反应的单质 Mo。通过增加反应物压块中的Si含量，显着减少未反应的Mo。对于Mo:Si=2:3的样品，合成的复合材料中含有少量的残余Mo。此外，从Mo:Si=1:2的样品中得到了由二硅化物MoSi2组成的单相产物。
An experimental study on the preparation of molybdenum disilicide (MoSi2) and MoSi2–Mo5Si3composites was conducted by self-propagating high-temperature synthesis (SHS) from elemental powder compacts of different stoichiometries. Test specimens with six compositions including Mo:Si=6:5, 1:1, 9:11, 3:4, 2:3, and 1:2 (corresponding to the Si content in the range of 45.5–66.7at.%) were employed in this study. Experimental evidence shows that the propagation mode of the reaction front, combustion wave velocity, and reaction temperature are significantly influenced by starting stoichiometry and preheating temperature (Tp) of the reactant compact. In the cases of preheating at 200 and 300°C, self-sustaining combustion featuring a spinning reaction zone was observed for the compacts of Mo:Si=6:5, 1:1, and 9:11, and the reaction temperatures lower than the melting point of Si (1410°C) were detected. On the other hand, a planar combustion front propagating in a steady manner was achieved in the samples with Mo:Si=3:4, 2:3, and 1:2 at Tp=200 and 300°C, and the reaction temperatures exceeding 1410°C were found. However, the planar reaction font was no longer stable in the case of without preheating or at Tp=100°C, and therefore was transformed into a localized reaction zone propagating in a spinning mode. According to the XRD analysis, formation of MoSi2–Mo5Si3composites from the reactant compacts of Mo:Si=6:5, 1:1, 9:11, 3:4, and 2:3 was confirmed, but a significant amount of elemental Mo left unreacted was found in the cases of Mo:Si=6:5 and 1:1. The unreacted Mo was considerably decreased by increasing the Si content in the reactant compact. For the sample of Mo:Si=2:3, the residual Mo containing in the synthesized composite was in a small quantity. In addition, a single-phase product composed of the disilicide MoSi2was yielded from the sample of Mo:Si=1:2.