Preparation of reactive sintering Si3N4-Si2N2O composites ceramics with diamond-wire saw powder waste as raw material.

In this paper, the reactive sintering Si3N4-Si2N2O composites ceramics were fabricated from the diamond-wire saw powder through the reaction-sintering nitridation method. The effects of sintering temperatures, holding time and oxygen contents on the Si3N4-Si2N2O composites formation were investigated in detail. The results revealed that the phases of final products consisted of α/β-Si3N4 and Si2N2O, and the proportion of three phases could be influenced by sintering temperatures and oxygen contents. In addition, rod-like particles and clastic granules were observed in final specimens, and rod-like particles mainly formed in low sintering temperatures and low oxygen contents, which could be attributed to the vapor-vapor-solid (VVS) growth mechanism. Furthermore, a lot of rod-like particles were distributed in cracks among the Si3N4-Si2N2O composites matrixes, which formed the bridge structures and enhanced the mechanical properties. The specimen obtained at 1500 ℃ with 5 wt.% SiO2 in raw materials had the highest compression strength of 150.6 MPa and the highest flexural strength of 46.1 MPa. Comparing with other typical composites, the Si3N4-Si2N2O composites in this work showed the desirable mechanical properties. Thus, this study provided an environment-friendly approach to recycle photovoltaic waste and reduce the cost of the reactive sintering Si3N4-Si2N2O composites ceramics.