关键词: 多孔Si₃N₄陶瓷, 造孔剂, 孔径分布, 孔结构, 透气系数

Abstract: To improve their permeability,porous Si₃N₄ ceramics were prepared using Si powder as the raw material,Y₂O₃ and CaF₂ as sintering aids,and polymethyl methacrylate microspheres (5 and 20 μm) as pore-forming agents,gel-casting,binder-removing,and finally reaction sintering at 1 650 ℃ for 3 h in a nitrogen atmosphere.The effects of the particle sizes and additions (volume fractions of 0,15%,30%,45%,and 60%) of the pore-forming agents on the apparent porosity,pore size distribution,pore structure and permeability coefficient of the porous Si₃N₄ ceramics were studied.The results show that:(1)the samples with pore agents exhibit dual pore structures,which are composed of stacking-derived pores and spherical evolution pores,with bimodal pore size distribution;(2)with the same particle size,as the pore-forming agent addition increases,the apparent porosity and permeability coefficient of the samples increase,while the bulk density,bending strength,and fracture toughness decrease;(3)at the same addition,the samples with the smaller-sized agents (5 μm) have higher apparent porosity,permeability coefficient,and bending strength;using smaller-sized pore-forming agents can reduce the thickness of the pore walls and enlarge the pore sizes of the stacking-derived pores within the pore walls,thus enhancing the permeability of the pore walls;(4) the sample with 60% pore-forming agents of 5 μm has the best comprehensive performance,with the apparent porosity of 55.1%,permeability coefficient of 11.62×10^-14 m² and bending strength of 35.3 MPa.

Key words: porous Si₃N₄ ceramics, pore-forming agent, pore size distribution, pore structure, permeability coefficient