结合PTFE与热激化的燃烧合成原位生成Zr2Al3C4/Al2O3复材

摘要

Preparation of Zr2Al3C4?Al2O3 in situ composites was investigated by self-propagating high-temperature synthesis (SHS) involving both aluminothermic reduction of ZrO2 and chemical activation of PTFE (Teflon). The starting materials included ZrO2, Al, carbon black and PTFE. In addition to the conventional SHS method, the experiments were conducted by a chemical-oven SHS (COSHS) route to thermally assist the synthesis reaction. The threshold amount of 2％ (mass fraction) PTFE was required to induce self-sustaining combustion. When the conventional SHS scheme was utilized, due to low combustion temperatures between 1152 and 1272 ℃ and insufficient reaction time, the dominant carbide forming in the composite was ZrC instead of Zr2Al3C4. On the other hand, the COSHS technique increased the combustion temperature of the reactant compact to about 1576 ℃, lengthened the high-temperature duration for the reaction, and prevented Al vapor from escaping away. As a consequence, Zr2Al3C4?Al2O3 composites with a small amount of Zr3Al3C5 were obtained. The microstructure of the COSHS-derived product showed that plate-like Zr2Al3C4 grains were about 2 μm in thickness and 10?30 μm in length, and most of them were closely stacked into a laminated configuration.%采用自蔓延燃烧合成(SHS)结合ZrO2铝热还原与PTFE化学激化制备Zr2Al3C4–Al2O3复材.原料包括氧化锆、铝、碳黑和PTFE粉末.除了传统的SHS方法外,合成实验以化学炉辅助的燃烧合成法(COSHS)进行.实验发现,达成自蔓延燃烧的最低PTFE含量为2％(质量分数).当使用传统SHS方法时,由于燃烧温度低(1152～1272℃)且反应时间不足,合成复材中主要的碳化物为ZrC,而不是Zr2Al3C4.但是,当应用COSHS技术时,燃烧温度可提高至1576℃,而且反应在高温下的时间增长,同时可避免铝蒸气的流失;因此,可以成功制备内含少许Zr3Al3C5的Zr2Al3C4?Al2O3复材.Zr2Al3C4晶粒为平板状,厚度约2μm,长度约10～30μm,多数晶粒紧密堆栈成层状微结构.