磷酸锆结合多孔氮化硅的增强与高温结构稳定性

Enhancement and High Temperature Structural Stability of Porous SiN-based Ceramics Bound with Zirconium Phosphate

采用磷酸铵盐部分取代磷酸,利用它们分解温度的不同和气相传质作用,控制磷酸锆结合多孔氮化硅陶瓷中的磷酸锆结合相逐级生成,巩固多孔陶瓷的孔壁结构,增强氮化硅晶粒之间的结合。结果表明:通过600℃埋烧后,所制备的多孔氮化硅陶瓷具有较高的孔隙率,且孔壁中Si_(3)N_(4)晶粒均具有完整的连接结合;经1400℃高温热处理后,多孔陶瓷中的磷酸锆部分分解使材料的孔隙率进一步增大,且主要物相仍为α-Si_(3)N_(4)晶粒,只有少量的α-β相转变;热处理后材料结构稳定且具有较高的力学强度,孔隙率60%样品的抗弯强度超过50MPa,且随着孔隙率的降低而增强显著。

Porous Si_(3)N_(4)ceramics bound with phosphate were fabricated by step synthesis of zirconium phosphate using ammonium phosphate partially instead of H_(3)PO_(4)as binding and pore-forming agent.The step synthesis of zirconium phosphate enhanced the binding between Si_(3)N_(4)grains and then strengthened the wall structure of porous Si_(3)N_(4)ceramics.The results show that the porous Si_(3)N_(4)ceramics burying consolidated at 600℃have a high porosity,and the Si_(3)N_(4)grains are combined well with a complete connection on the pore wall.Although the decomposition of zirconium phosphate increases the porosity of porous ceramics during the pressureless sintering at 1400℃for 2 h,the main phase remainsα-Si_(3)N_(4)and only a small amount of crystal phase transition occurs from alpha to beta-Si_(3)N_(4).After 1400℃heat-temperature treatment,porous Si_(3)N_(4)ceramics maintain stable microstructure and high mechanical strength.The bending strength of the sample with 60%porosity is higher than 50 MPa,and increases significantly with the decrease of porosity.