层状可加工陶瓷Ti3SiC2自蔓延高温合成反应机理的研究

采用燃烧波淬熄法,以Ti粉、Si粉和C粉为原料研究了层状可加工陶瓷Ti3SiC2在自蔓延高温合成(SHS)中的反应机理.淬熄试样中保留未反应区、反应区和已反应区,用扫描电子显微镜观察燃烧反应中显微组织的转变过程,用能谱仪分析各微区的成分变化,并通过差热分析(DSC-TGA)和XRD分析考察了从600℃到1500℃ Ti-C-Si系统的反应合成过程和相形成规律.结果表明:层状可加工陶瓷Ti3SiC2自蔓延高温合成的机理为溶解-析出机制,Ti粉与Si粉的固态扩散导致低熔点Ti-Si溶液形成,Ti、Si、C粉粒逐渐向Ti-Si溶液中溶解,当溶液中的Ti、Si、C浓度饱和时,从中析出TiC、SiC颗粒,最后形成最终产物Ti3SiC2.

Mechanism research on self-propagating high-temperature synthesis of Ti3SiC2 ceramics

The mechanism on self-propagating high-temperature synthesis(SHS) of Ti3SiC2 ceramics with Ti,Si and C powders mixtures was studied by means of the combustion front quenching method.The process of microstructure conversion in the quenched sample was observed using a scanning electron microscope(SEM),a compositional change in each micro-region of the microstructure was studied by energy dispersive X-ray(EDX),the temperature was measured,and investigated by differential thermal analysis(DTA) of raw powders and X-ray diffraction(XRD) of samples sintered at different temperatures.The results show that the mechananism of combustion synthesis of Ti3SiC2 ceramics can be described as dissolution-preciptation.Ti-Si melt is formed through sold diffusion between titanium and nickel powders,then the atoms of Ti,C and Si gradually dissolve into the Ti-Si melt,and TiC,SiC particles will prepicitate from the Ti-Si-C melt as the Ti-Si-C is saturated,at last the final product of Ti3SiC2 forms.