Abstract:

The effects of binders on the sintering performance,mechanical properties and microstructure of SiC-CA₆ composites were investigated using commercial SiC,CA₆ fine powder and activated α-Al₂O₃ as raw materials,water soluble resin and phenolic resin as the binder,and firing at 1 400,1 500,1 600 and 1 650 ℃ for 3 h,respectively.The results show that the properties changes of the two samples are similar,but the samples bonded with water soluble resin have better comprehensive properties.Firing at temperatures below 1 600 ℃ in carbon embedded atmosphere,SiC in the samples bonded with water soluble resin oxidizes to form SiO₂,andin turn reacts with CA₆ to generate low melting point phase,thus promoting thesintering.Firing at 1 650 ℃,SiC under goes activated oxidation and the SiO₂ content in liquid decreases allowing for substantial generation of well-developed flake CA₆ in the samples.As the temperature increases,the residual flakycarbon in the samples bonded with phenolic resin transforms to amorphous carbon,slowing the oxidation of SiC and reducing the liquid phase,which hinders the sintering and affects the performance of the samples to a certain extent.

Key words: silicon carbide-calcium hexaluminate composites, water soluble resin, phenolic resin, calcium hexaluminate, residual carbon

摘要：

以工业SiC、CA₆细粉和活性α-Al₂O₃为原料,分别以水溶性树脂和酚醛树脂为结合剂,制备了SiC-CA₆复合材料,在1 400、1 500、1 600和1 650 ℃热处理3 h后,研究了结合剂对SiC-CA₆复合材料烧结性能、力学性能和显微结构的影响。结果表明:两种结合剂制备的试样性能的变化趋势相近,但水溶性树脂结合的试样在总体上具有较好的综合性能。在埋碳条件下,热处理温度≤1 600 ℃时,水溶性树脂结合试样中的SiC氧化生成SiO₂,进而与材料中的CA₆反应生成低熔点物相,促进试样的烧结;热处理温度为1 650 ℃时,SiC发生活性氧化,液相中的SiO₂含量也会减少,从而使得试样中生成大量发育良好的片状CA₆。酚醛树脂结合的试样中的残碳在材料中会随着温度的升高从鳞片状转化为无定形状,由于残碳的存在减缓了材料中SiC的氧化,也使得材料中液相减少,进而在一定程度上抑制材料的烧结,从而对材料的性能造成一定的影响。

关键词: SiC-CA₆复合材料, 水溶性树脂, 酚醛树脂, CA₆, 残碳