Abstract: In order to improve the mechanical properties of reaction sintered silicon carbide,reaction sintered silicon carbide ceramics were prepared using silicon carbide micropowder (55-44 and 5.0-3.5 μm) and carbon black as raw materials,carboxymethyl cellulose sodium (CMC) and hydroxypropyl methyl cellulose (HPMC) as pore forming agents,firing at 1 740 ℃ for 1 h.Effects of different carbon black additions (5%,7.5%,10%,12.5%,and 15%,by mass) and pore forming agents with different mass ratios of CMC to HPMC on the physical properties of reaction sintered silicon carbide were studied.The prepared ceramics were also analyzed by XRD and an optical microscope.The results show that:(1)when the carbon black addition increases from 5% to 15%,the flexural strength of the material increases from 172 MPa to 258 MPa,and the fracture toughness increases from 3.31 to 3.77 MPa·m^1/2;(2)the pore forming agent can optimize the distribution of free Si;when the carbon black addition is 15% and the pore forming agent mass ratio of CMC/HPMC is 1.5/4.5,the reaction sintered silicon carbide performs excellent mechanical properties with the flexural strength of 268 MPa and the fracture toughness of 4.42 MPa·m^1/2.

Key words: reaction sintered silicon carbide, carbon black, pore forming agent, fracture toughness

摘要： 为提高反应烧结碳化硅的力学性能,以碳化硅微粉(55~44和5.0~3.5 μm)和炭黑为原料,羧甲基纤维素纳(CMC)和羟丙基甲基纤维素(HPMC)为造孔剂,经1 740 ℃保温1 h制备了反应烧结碳化硅陶瓷。研究了炭黑添加量(加入质量分数分别为5%、7.5%、10%、12.5%、15%)及不同质量比的造孔剂对反应烧结碳化硅物理性能的影响,并进行XRD和光学显微镜分析。结果表明:1)当炭黑添加量(w)从5%增加到15%时,材料弯曲强度从172 MPa升高到258 MPa,断裂韧性从3.31 MPa·m^1/2升高到3.77 MPa·m^1/2;2)造孔剂能够优化游离Si的分布,当炭黑添加量为15%(w),造孔剂CMC与HPMC质量比为1.5∶4.5时,反应烧结碳化硅具有优异的力学性能,其弯曲强度为268 MPa,断裂韧性为4.42 MPa·m^1/2。

关键词: 反应烧结碳化硅, 炭黑, 造孔剂, 断裂韧性