Fabrication of α-Sialon Nano-Ceramics
Y- α-sialon (m=1.35, n=0.675) ceramics were prepared by high-energy mechanical milling followed by spark plasma sintering. The milling promoted not only liquid-phase sintering, but also phase transformation from β-Si3N4 to α-sialon. Under the same holding time of 5 min, milled powder could be completely densified at 1500oC, which is about 250oC lower than that required for as-received powder. The temperature where the phase transformation finished was 1600oC and 1750oC for milled and as-received powder, respectively. The grain size of obtained dense ceramics from milled powder was significantly decreased. Nano-sized dense ceramics have been obtained by sintering the milled powder at 1500oC for 5 min. Although 100 % α-sialon has not been achieved, the nano-sized ceramics can be used for superplastic deformation, taking advantage of small grain size and large amount of transient liquid phase.
T. Ohji, T. Sekino and K. Niihara
X. Xu, T. Nishimura, N. Hirosaki, R. J. Xie, Y. Yamamoto, H. Tanaka, "Fabrication of α-Sialon Nano-Ceramics ", Key Engineering Materials, Vols. 317-318, pp. 629-632, 2006