Abstract: When preparing reaction-bonded SiC ceramics by slip casting,due to the introduction of a large amount of solvent,problems of high porosity and low strength exist for the products after subsequent drying,vacuum Si infiltration,and sintering.To enhance the mechanical properties of reaction-bonded SiC ceramics prepared by slip casting,fine SiC powder,carbon black,and graphite were used as main starting materials,sodium carboxymethyl cellulose as the binder,polyvinylpyrrolidone as the dispersant,and TiN powder as the additive to prepare SiC ceramic slurries with TiN extra-addition of 0,2.5%,5%,and 7.5%,by mass.SiC ceramics were obtained after slip casting and heat treatment at 1 740 ℃ for 2 h in the Si embedded condition.The effect of the TiN addition on the physical properties,phase composition,and microstructure of the reaction-bonded SiC ceramics was investigated.The results show that when the TiN addition increases from 0 to to 7.5%,the apparent porosity shows a slight downward trend,while the bulk density increases accordingly;TiN can react with free Si to generate TiSi₂ with high fracture toughness,and to some extent consume the free Si in the sample,improving the mechanical properties of the reaction-sintered SiC ceramics.Therefore,when the TiN addition increases from 0 to 7.5%,the modulus of rupture increases from 204.8 MPa to 304.3 MPa,an increase of 48.6%,and the fracture toughness also increases from 3.76 MPa·m^1/2 to 4.42 MPa·m^1/2,with a growth rate of 17.6%.When the TiN powder addition is 7.5%,the reaction-sintered SiC sample exhibits the optimal comprehensive performance.

Key words: reaction-sintered SiC, TiN, slip casting, mechanical properties

摘要： 在采用注浆成型工艺制备反应烧结SiC陶瓷的过程中,由于大量溶剂的引入,后续干燥、真空渗Si烧结后,存在制品气孔率偏高、强度较低的问题。为提高注浆成型反应烧结SiC陶瓷的力学性能,选用碳化硅细粉、炭黑、石墨作为主要原料,以羧甲基纤维素钠作为黏结剂,聚乙烯吡咯烷酮作为分散剂,并添加TiN粉体,配制TiN外加质量分数分别为0、2.5%、5%、7.5%的SiC陶瓷浆料,经注浆成型得到陶瓷素坯,再经 1 740 ℃保温2 h埋Si烧结制得SiC陶瓷。探究TiN粉体添加量对反应烧结SiC陶瓷的物理性能、物相组成以及显微结构的影响。结果表明:随着TiN的外加质量分数从0逐步增加至7.5%,反应烧结SiC陶瓷的显气孔率呈现出略微下降的趋势,体积密度则相应有所上升;TiN能够与游离Si反应生成断裂韧性较高的 TiSi₂,并在一定程度上消耗了试样中的游离Si,提高反应烧结SiC陶瓷的力学性能,因此TiN的外加质量分数从0增至7.5%时,试样的抗弯强度从204.8 MPa提升至304.3 MPa,涨幅为48.6%,断裂韧性也从 3.76 MPa·m^1/2 增加到4.42 MPa·m^1/2,增长率达17.6%。当TiN粉末的外加质量分数为7.5%时,反应烧结SiC试样展现出较佳的综合性能。

关键词: 反应烧结SiC, TiN, 注浆成型, 力学性能