燃烧合成Mg2Ni的反应过程研究

Reaction Process Research of Combustion Synthesis Mg2Ni

摘要:

采用自蔓延及热爆两种燃烧模式成功合成了较纯的Mg2Ni金属间化合物。通过对不同预热温度下热爆反应过程的考查，证实在较低温度下，Mg-Ni体系存在固-固反应，且反应的程度随预热速度的降低而增大。采用在试样项部添加Al-Ti—C引燃剂的方法，在圆柱形钢模具内成功淬熄了Mg—Ni反应。对不同区域的XRD分析表明反应直接生成了Mg2Ni而没有中间产物。结合SEM及EDS分析，燃烧合成Mg2Ni分为以下几个过程：（1）预热阶段的固-固反应过程；（2）燃烧阶段的液相反应过程；（3）燃烧完成阶段的产物冷却结晶过程；（4）保温阶段的成分均匀化过程。

Abstract:

The pure Mg2Ni intermetallic was synthesized by self-propagating combustion mode and thermal explosion mode respectively. And the reaction process of thermal explosion was researched under different preheat temperatures. The results show that solid combustion exists at lower temperatures, and the degree of reaction increase with the decrease of preheat rate. A further experiment of Combustion Front Quenching (CFQ) was carried out successfully in cylindrical steel mould by adding some Al-Ti-C powder that is accepted as a high exothermic system on the top of Mg-Ni samples. The physical and chemical changes of all region in the quenched samples during the combustion synthesis were examined by scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS) and x-ray diffraction (XRD). The results show that the Mg2Ni is directly synthesized rather than through other intermediates and the synthesis process of Mg2Ni can be express as: (1) solid combustion in the pre-combustion stage; (2) liquid combustion in the combustion process; (3) nucleation and crystallization of the product after the reaction; (4) uniformizing of the composition in the heat preservation stage.