Effect of agarose content on microstructures and mechanical properties of porous silicon nitride ceramics produced by gelcasting

• Published in: Journal of Zhejiang University. A. Science Vol. 11; no. 10; pp. 771 - 775
• Main Authors: Zhang, Jing-yi, Ye, Feng
• Format: Journal Article
• Language: English
• Published: Hangzhou Zhejiang University Press 01.10.2010
• Subjects: Civil Engineering; Classical and Continuum Physics; Engineering; Industrial Chemistry/Chemical Engineering; Mechanical Engineering; 凝胶注模成型; 力学性能; 多孔硅; 微观结构; 氮化物陶瓷; 氮化硅陶瓷; 琼脂糖; ceramics; Gelcasting; TQ174; Porous Si; Mechanical properties; Microstructure; N
• ISSN: 1673-565X; 1862-1775
• DOI: 10.1631/jzus.A1000125

Porous Si3N4 self-reinforce ceramics were prepared by gelcasting using agarose solutions. By changing the agarose content in the slurries, the porous silicon nitride ceramics with different porosities, α→β-Si3N4 phase transformation, and mechanical properties were obtained. When the agarose content changed from 0.2% to 0.8% （w/w, based on powder）, the porosities increased from 10.3% to 21.4%, while the fracture strength decreased from 455 to 316 MPa and the fracture toughness decreased from 6.6 to 5.5 MPa·m1/2. Many fibrous β-Si3N4 grains grown from the internal wall of the round pores is the typical microstructure of the gelcasting porous silicon nitride ceramic. Both elongated β-Si3N4 grains and suitable interfacial bonding strength contributes to high fracture toughness by favoring crack deflection and bridging. The growth mechanisms of fibrous grains resulted from the synergy of solution-diffusion-reprecipitation and vapor-liquid-solid （VLS）.