关键词: 反应烧结碳化硅, 炭黑, 造孔剂, 断裂韧性

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