Effect of [beta]-Si3N4 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 2016-12, Vol.75 (4), p.256
• Main Authors: Yang, Zhigang, Yu, Jianbo, Li, Chuanjun, Zhong, Yunbo, Deng, Kang, Ren, Zhongming, Wang, Qiuliang, Dai, Yinming, Wang, Hui
• Format: Article
• Language: English
• Subjects: Casting; Ceramics; Magnetic fields; Sintering
• ISSN: 0371-750X; 2165-5456
• DOI: 10.1080/0371750X.2016.1202143

Textured porous Si3N4 ceramics with fine and coarse [beta]-Si3N4 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]-Si3N4 powders in 6T. The Lotgering orientation factor in green bodies showed the value of 0.72∼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]-Si3N4 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 Si3N4 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.