| 【文章摘要】 Ceramic bond c BN composites with large pores were prepared by firing at 740 ℃ for 1 h using Na_2O-Al_2O_3-B_2O_3-SiO_2 glass and c BN abrasives( particles size 0.150 mm /0.124 mm) as main starting materials,c BN micro-particles( particles size 0. 014 mm) as the additive,and NH4HCO3 as the pore forming agent. The effect of NH_4HCO_3 and c BN micro-particles on the microstructure and properties of c BN composites was studied. The results show that for the c BN composite without c BN micro-particles the porosity obviously increases when the NH_4HCO_3 addition increases from 0 to 21 mass%,and increases slightly when the NH_4HCO_3 addition increases from 28 mass% to 42 mass%; and the bending strength decreases with the NH_4HCO_3 addition increasing. For the c BN composite with 14 mass% c BN microparticles,the porosity increases continuously with the NH_4HCO_3 addition increasing,achieving 56. 14% for the NH_4HCO_3 addition of 42 mass%,while,an obvious decrease of the bending strength is obtained. It is clearly indicated that the c BN micro-particles contribute to the high porosity and high strength of the porous ceramic bond c BN composites. |