Abstract:

Reaction-sintered silicon carbide specimens were prepared using SiC,carbon black,and thermosetting phenolic resin as raw materials,extra adding metal Al powder (0,and 4 mass%),mixing,shaping,curing at 180 ℃,and carbonizing at 800 ℃,and firing in vacuum at 1 550 ℃,1 600 ℃,1 650 ℃ and 1 700 ℃,respectively,in graphite crucibles embedded by Si powder.The results show that:(1)the main phases of the specimens with 4% or without Al powder are α-SiC,β-SiC and free Si;(2)the specimen with 4% Al powder has lower permanent linear change;after firing at 1 600 ℃,the specimen has the lowest residual Si content and the highest SiC content,and performs the best properties;(3)Al has great plasticity;the specimen with 4% Al powder has high density and low porosity;during the reaction sintering process,the resistance of liquid Si infiltration is greater,the amount of infiltration is less,so the final residual amount is less,so the hot strength of the specimen is higher;after firing at 1 700 ℃,Al₄SiC₄ forms,increasing the bonding among the particles.

Key words: reaction sintered, silicon carbide, aluminum powder, residual silicon, microstructure

摘要：

以SiC、炭黑和热固性酚醛树脂为主要原料,配制成Al粉外加量分别为0和4%(w)的两种试样,经混料、成型、180 ℃固化、800 ℃炭化后,在石墨坩埚中用单质Si掩埋,在真空条件下分别经1 550 、1 600、1 650和1 700 ℃烧成反应烧结碳化硅。结果表明:1)未添加和添加4%(w)Al粉的试样经1 550~1 700 ℃烧成后,其主要物相均为α-SiC、β-SiC和游离Si。2)添加4%(w)Al粉试样的烧后线变化更小;经1 600 ℃烧成后残余Si量最低,SiC含量最高,综合性能最优。3)Al具有较大的可塑性,添加4%(w)Al粉试样的成型致密度更高,气孔更少更小,在反应烧结过程中液态Si渗入的阻力更大,渗入量更少,最终残余量也更少,试样的高温强度更高;经1 700 ℃烧成生成Al₄SiC₄,增强了物料颗粒之间的结合。

关键词: 反应烧结, 碳化硅, 铝粉, 残余硅, 显微结构