1.西安建筑科技大学材料科学与工程学院，西安 710055;2.中钢集团洛阳耐火材料研究院有限公司先进耐火材料国家重点实验室，洛阳 471039
1.College of Materials Science and Engineering， Xi'an University of Architecture and Technology，Xi'an 710055;2.State Key Laboratory of Advance Refractories， Sinosteel Luoyang Institute of Refractories Research Co.，Ltd.，Luoyang 471039
Si3N4多孔陶瓷具有优异的力学性能、介电性能、热学性能和化学稳定性等，特别适用于高温、大载荷、强侵蚀环境下的宽频透波材料。反应烧结Si3N4多孔陶瓷在性能、工艺和成本方面优势显著，原料Si粉特性显著控制着其物相、显微结构、力学和介电性能。本文以不同粒径和纯度的Si粉为原料制备注凝成形、反应烧结Si3N4多孔陶瓷。结果表明，双粒径配料使素坯产生紧密堆积效应，其遗传并进一步演化出两级显微组织强韧化机制，双粒径配料5 & 45 μm时的弯曲强度和断裂功获得最大值109.94 MPa和990.74 J/m2。该值分别比单粒径配料5和45 μm时的值提高了111.42%、25.97%和46.55%、20.46%；介电常数和介电损耗分别约为4.20和0.007。注凝成形、反应烧结Si3N4多孔陶瓷可以兼顾力学性能和介电性能，适用于透波罩等异形、大尺寸构件。
Silicon nitride porous ceramics possessed excellent mechanical， dielectrical， thermal properties and chemical stability. It was very suitable for broadband wave transparent materials using in high temperature， large load and strong corrosion circumstance. Reaction bonded silicon nitride porous ceramics had advantages of excellent properties， convenient process and low cost. The characteristics of Si powders remarkably controlled the phase component， microstructure， mechanical and dielectric properties. In this study， Si powders with different particle size and purity were used to prepare gelcasting and reaction bonded silicon nitride porous ceramics. The results show that dual granularity produces close packing effect in the green body， which is inherited and further evolves into a reinforcing and toughening mechanisms of two-tier microscopic tissue in the sintered body. Dual granularity of 5 μm and 45 μm obtains the largest bending strength of 109.94 MPa and work of fracture of 990.74 J/m2. The values are 111.42% and 25.97% higher than that of single granularity of 5 μm as well as 46.55% and 20.46% higher than that of single granularity of 45 μm . The dielectric constant and dielectric loss are about 4.20 and 0.007 respectively. Gelcasting and reaction bonded silicon nitride porous ceramics can possess both good mechanical and dielectric properties， which are suitable for special-shaped and large scale component such as radome.