化学激励燃烧合成SiC超细粉末的工艺和机理研究

INVESTIGATION ON PROCESSING AND MECHENISM OF ULTRA-FINE SiC POWDER BY CHEMICAL STIMULATION COMBUSTION SYNTHESIS

研究了利用聚四氟乙烯 (-C2 F4 -) n 作活化剂时Si/C混合粉末在氮气中的燃烧行为 .结果表明 :少量聚四氟乙烯的加入就可有效激励Si -C弱放热反应 ,使之以燃烧合成方式生成SiC .氮气参与反应时可进一步提高燃烧反应温度 ,并且首先以气相 -晶体机制生成Si3N4 ,然后在反应前沿分解为SiC .调整工艺参数可获得亚微米级SiC粉末 .综合X射线衍射、差热 /热重分析及扫描电镜观察 ,提出了Si-C -N -(-C2 F4 -) n 体系中的燃烧反应机制 ,并从热力学角度对实验结果进行了讨论 .

The combustion behavior of Si/C composite powders with addition of (-C 2F 4-) n as activator at pressurized nitrogen atmosphere was investigated. It is demonstrated that a small amount of (-C 2F 4-) n addition can stimulate effectively the weak exothermic reaction between Si and C in the form of self_sustaining combustion mode. The combustion temperature can be enhanced further if the reaction is carried out in nitrogen atmosphere. The sequential reaction with the formation of Si 3N 4 via vapor_crystal mechanism is followed by the decomposition of the nascent Si 3N 4 and the competing reaction between Si and C, which produce SiC. Sub_micrometer sized SiC powders can be obtained by optimizing the processing parameters. The reaction mechanism in the Si-C-N-(-C 2F 4-) n system is deduced based on XRD and DSC/TG analysis and SEM observation and the experimental results are also discussed based on thermodynamic analysis.