孔隙率对20%BN/Si_3N_4复合多孔陶瓷力学与介电性能的影响

Effect of Porosity on Mechanical and Dielectric Properties of 20%BN/Si_3N_4 Composite Porous Ceramics

采用气氛烧结工艺,通过在原料中加入不同体积分数的PMMA球造孔剂制备了气孔率在32.5%～45.8%之间的20%BN/Si3N4(体积分数,下同)多孔复合陶瓷材料。显微组织结构分析表明由PMMA球分解造成的孔较为均匀地分布在基体中。研究了气孔率对复合陶瓷力学性能与21～33GHz微波频率范围内介电性能的影响规律。三点弯曲强度随着气孔率的增加从197MPa降低至141MPa,介电常数和介质损耗也随着气孔率的增加而减少,介电常数与Maxwell-Garnet关系符合较好。

Porous 20vol.%BN/Si3N4 composite ceramics with different volume fractions of 32.5%to 45.8% in porosity were prepared by adding different amounts of PMMA spheres as the pore-forming agent. Microstructural analysis revealed that spherical cavities decomposed from PMM are scattered uniformly in matrix. The effect of the porosity on the mechanical properties and dielectric properties in the range of 21 GHz and 33 GHz for the composites are discussed. The dielectric constant and tangent loss, as well as flexural-strength decrease with the increase of the porosity, and the dielectric constant data agrees with the Maxwell-Garnet law well.