Effect of beta -Si sub(3)N sub(4) Initial Powder Size on Texture Development of Porous Si3N4 Ceramics Prepared by Gel-Casting in a Magnetic Field

• Published in: Transactions of the Indian Ceramic Society Vol. 75; no. 4; pp. 256 - 262
• Main Authors: Yang, Zhigang, Yu, Jianbo, Li, Chuanjun, Zhong, Yunbo, Deng, Kang, Ren, Zhongming, Wang, Qiuliang, Dai, Yinming, Wang, Hui
• Format: Journal Article
• Language: English
• Published: 01.10.2016
• Subjects: Ceramics; Coarsening; Magnetic fields; Orientation; Silicon nitride; Sintering (powder metallurgy); Surface layer; Texture
• ISSN: 0371-750X; 2165-5456
• DOI: 10.1080/0371750X.2016.1202143

Textured porous Si sub(3)N sub(4) ceramics with fine and coarse beta -Si sub(3)N sub(4) powders as the raw materials were prepared by gel casting in a strong magnetic field of 6T and subsequent pressureless sintering. These results showed that highly textured porous Si3N4 ceramics could be obtained by adjusting the ratio between fine and coarse beta -Si sub(3)N sub(4) powders in 6T. The Lotgering orientation factor in green bodies showed the value of 0.72 similar to 0.74 with the increase of coarse powder content. The sintering process promoted texture development of the samples by Ostwald ripening owing to the big difference in the beta -Si sub(3)N sub(4) initial powder size. After sintering at 1800oC for 2 h, the degree of texture (Lotgering orientation factor) in the sample, prepared with fine and coarse powders at the ratio of 1:1, reached the maximum value (0.91), and it had relatively high density (66.91%) and low apparent porosity (34.51%). The crystallographic texture in porous Si sub(3)N sub(4) ceramics led to the anisotropic bending strength. The method combined with gel casting in a strong magnetic field was beneficial for preparing highly textured porous ceramics with big and complex shape.