In‐situ synthesis of 15R‐Sialon from Al‐Si₃N₄‐Al₂O₃ composite at 1500°C via liquid‐phase sintering

Abstract

In this study, alumina-based composite with 12 wt% Al and 16 wt% Si 3 N 4 was designed to achieve the synthesis of 15R-Sialon reinforced alumina composite.To investigate the reaction mechanism, two-step sintered Al-Si 3 N 4 -Al 2 O 3 samples at different temperatures ranging from 600 • C to 1500 • C were prepared and characterized via X-ray diffraction and scanning electron microscope (SEM). The results revealed that 15R-Sialon was synthesized at 1500 • C through a novel liquid Si phase sintering and Si 3 N 4 played as a precursor and a reactant. First, Si 3 N 4 precursor reacted with Al to form intermediate phases AlN and Si, which were not further transformed below 1400 • C. When the sintering temperature was 1500 • C, the formed Si presented as a liquid phase, under the influence of which plate-like15R-Sialon was generated from Al 2 O 3 , residual Si 3 N 4 , and derived AlN. The obtained Si was also involved in the synthesis of 15R-Sialon and completely transformed. In addition to the AlN from Si 3 N 4 , the AlN deriving from the nitridation of Al may not react with liquid Si. Compared to 15R-Sialon from liquid Si, platelike 15R-Sialon with smaller size was generated from AlN, SiO, and O 2 .