Abstract: This work aims to explore a low-cost and environmentally friendly shaping method to prepare reaction-bonded silicon carbide (RBSC) materials,SiC fine powder and micropowder,phenolic resin,and epoxy resin were used as the main raw materials,tetramethylammonium hydroxide as the dispersant to prepare SiC ceramic slurries with a solid loading of 55 mass% and phenolic resin mass fractions of 13.5%,18%,22.5%,and 27%,respectively.The green bodies prepared by gelcasting and cured were heat treated at 800 ℃ for 2 h,followed by heat treatment at 1 760 ℃ for 3 h in vacuum to form the RBSC materials.The curing mechanism of the green bodies and the effect of the phenolic resin addition on the microstructure,phase composition,and physical properties of the samples were studied.The results show that:(1)the curing mechanism of the green body is that the hydroxymethyl groups in the phenolic/epoxy resin undergo cross-linking via condensation reactions with ortho-para hydrogen atoms in the aromatic ring,forming a high-strength bonding network;(2)with the increasing phenolic resin addition,the residual carbon in the resin system reacts with molten silicon,the cold modulus of rupture of the fired sample first increases and then decreases;when the addition of phenolic resin is 18%,the cold modulus of rupture of the sample is the highest,reaching 79.9 MPa;the apparent porosity and bulk density of the sample are 1.1% and 2.88 g·cm^-3,respectively.

Key words: reaction-bonded silicon carbide, gelcasting, phenolic resin, epoxy resin

摘要： 为了探究一种低成本、环保的反应烧结碳化硅材料成型方法,以SiC细粉和微粉、酚醛树脂和环氧树脂为主要原料,四甲基氢氧化铵为分散剂,配制固相质量分数为55%,酚醛树脂质量分数分别为13.5%、18%、22.5%及27%的SiC陶瓷泥浆,采用凝胶注模成型制成坯体,坯体经固化、800 ℃保温2 h热处理后,在真空条件下1 760 ℃保温3 h制备反应烧结碳化硅材料。研究了坯体的固化机制及酚醛树脂加入量对试样显微结构、物相组成和物理性能的影响。结果表明:1)坯体固化机制为酚醛/环氧树脂中羟甲基与芳环的邻对位氢发生缩合反应交联,形成了较高强度的结合网络。2)随着酚醛树脂加入量的增加,树脂体系裂解残碳与熔融硅反应,烧后试样的常温抗折强度先增加然后降低。当酚醛树脂加入量为18%(w)时,烧后试样常温抗折强度最高,为79.9 MPa,此时试样的显气孔率和体积密度分别为1.1%、2.88 g·cm^-3。

关键词: 反应烧结碳化硅, 凝胶注模, 酚醛树脂, 环氧树脂