稀释剂量对反应烧结Si_3N_4陶瓷结构和性能的影响

以工业Si粉为原料,α-Si3N4粉为稀释剂,聚乙烯醇为粘结剂,采用反应烧结工艺制备了Si3N4陶瓷。研究了稀释剂量对反应烧结Si3N4陶瓷的体积密度、开气孔率、相组成、微结构、弯曲强度和抗热震性的影响。结果表明,随稀释剂量的增加,Si3N4陶瓷的体积密度从2.27g/cm3降至2.04g/cm3,开气孔率从23%升至33.8%。Si3N4陶瓷由α-Si3N4、β-Si3N4和少量单质Si组成。Si3N4主要以针状晶形式存在,残留Si呈不规则块体。随着稀释剂量的增加,4组Si3N4陶瓷的三点抗弯强度分别为119MPa、112MPa、146MPa和113MPa;经50次800℃至室温空冷热震后,其强度保持率分别为81.5%、90.2%、87%和88.5%,表现出较好的抗热震性。

Effect of Diluent Amount on the Structure and Properties of Reactive Sintered Si3N4 Ceramic

Reactive sintered Si3N4 ceramic was prepared using industrial Si powder as raw material,α-Si3N4 powder as diluent,and polyvinyl alcohol as binder.The effects of the diluent amount on the volume density,open porosity,phase,microstructure,bending strength and thermal shock resistance of the Si3N4 ceramic were investigated.The results indicate that the volume density of the Si3N4 ceramic decreases from 2.27g/cm3 to 2.04g/cm3 while the open porosity increases from 23% to 33.8% with the diluent amount increases.The phases of the Si3N4 ceramic are mainly α-Si3N4,β-Si3N4 and a little of Si.The Si3N4 crystal exhibits a needle-like structure,while the residual Si exhibits an irregular block-like structure.The three point bending strength of the Si3N4 ceramics are 119MPa,112MPa,146MPa and 113MPa,respectively,with the diluent amount increases.Their conservations of the bending strength are 81.5%,90.2%,87%,and 88.5%,respectively,after 50 cycles thermal shock from 800℃ to room temperature.The Si3N4 ceramic exhibits better thermal shock resistance.