可加工氮化硅/氮化硼复相陶瓷的制备

FABRICATION OF MACHINABLE SILICON NITRIDE/BORON NITRIDE COMPOSITE CERAMICS

以硅(Si)粉、六方氮化硼(h-BN)为原料,在氮气(N2)中用燃烧合成(combustion synthesis,CS)气固反应法,原位生成可加工氮化硅/氮化硼(Si3N4/h-BN)复相陶瓷。考察了h-BN不同体积分数(下同)对Si3N4/h-BN复相陶瓷可加工性的影响。结果表明:在实验条件下,Si粉氮化完全,不存在残余的游离Si。Si3N4/h-BN复相陶瓷中以柱状β-Si3N4为主相,β-Si3N4晶粒之间为针状h-BN相。随着h-BN相含量的增加,Si3N4/h-BN复相陶瓷的可加工性提高,抗弯强度先减小后增加。h-BN含量为25%时,Si3N4/h-BN复相陶瓷的抗弯强度最低。

Machinable silicon nitride/ hexahedral boron nitride （Si3N4/h-BN） composite ceramics with silicon （Si） powders and hexahedral boron nitride （h-BN） as raw materials were synthesized in-situ in a nitrogen pressure by combustion synthesis gas-solid reaction. The effect of volume fraction （the same below） of h-BN on machinable properties of Si3N4/BN composite ceramics was inves- tigated. The results show that Si powders were fully nitrified under the experimental conditions and no residual free silicon was found. Columnar crystals of β-Si3N4 are the main phase and acicular crystals of h-BN disperse intergranular position of β-Si3N4. With increase of the volume content of h-BN, the machinability of the composite ceramics increases, but the bending strength first decreases and then increases. The lowest point of bending strength is at 25% of h-BN.