New Strategies for Preparing NanoSized Silicon Nitride Ceramics |
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Authors: | Xin Xu Toshiyuki Nishimura Naoto Hirosaki Rong-Jun Xie Yinchun Zhu Yoshinobu Yamamoto Hidehiko Tanaka |
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Affiliation: | National Institute for Materials Science, Advanced Materials Laboratory, Tsukuba, Ibaraki 305-0044, Japan |
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Abstract: | We report the preparation of nanosized silicon nitride (Si3N4) ceramics via high-energy mechanical milling and subsequent spark plasma sintering. A starting powder mixture consisting of ultrafine β-Si3N4 and sintering additives of 5-mol% Y2O3 and 2-mol% Al2O3 was prepared by high-energy mechanical milling. After milling, the powder mixture was mostly transformed into a non-equilibrium amorphous phase containing a large quantity of well-dispersed nanocrystalline β-Si3N4 particles. This powder precursor was then consolidated by spark plasma sintering at a temperature as low as 1600°C for 5 min at a heating rate of 300°C/min. The fully densified sample consisted of homogeneous nano-Si3N4 grains with an average diameter of about 70 nm, which led to noticeable high-temperature ductility and elevated hardness. |
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