| Effect of B-Si3N4 Initial Powder Size on Texture
Development of Porous Si3N4 Ceramics Prepared
by Gel Casting in a Magnetic Field |
Zhigang Yang,1 Jianbo Yu,1 Chuanjun Li,1 Yunbo Zhong,1 Kang Deng,1 Zhongming Ren,1, *
Qiuliang Wang,2 Yinming Dai2 and Hui Wang2
pages : 256-262
DOI : 10.1080/0371750X.2016.1202143 |
| Abstract |
| Textured porous Si3N4 ceramics with fine and coarse -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 -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 -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. |
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