Effect of gas atmospheres and SiO2 content on preparation and properties of SiO2–Si3N4 composite ceramics via nitridation of diamond-wire saw silicon waste powder.

Composite ceramics are applied widely nowadays by combining superior properties of different ceramic materials. In this study, SiO 2 –Si 3 N 4 composite ceramics with higher mechanical properties and lower dielectric constant were successfully fabricated by nitriding diamond-wire saw silicon waste. The effect of gas atmospheres (N 2 , NH 3 , N 2 –H 2) and SiO 2 content (0%, 10%, 20%, 30%, 40%) on the microstructure and properties of composite ceramics were studied. It shows that the synthesis of SiO 2 –Si 3 N 4 composite ceramics can be obtained in the NH 3 atmosphere, and it is inevitable to form the Si 2 N 2 O phase in N 2 and N 2 –H 2 mixture atmospheres. Furthermore, the shrinkage rate and dielectric constant of the ceramics decreased as SiO 2 content increased from 0% to 40%. As for the porosity of the sintered ceramics, it first decreased and then increased, with a minimum of 1.73% at the SiO 2 content of 20%. However, the flexural strength of the sintered ceramics was the inverse of the porosity, with a maximum of 160.72 MPa at the SiO 2 content of 30%. For the sintered ceramic with 30% SiO 2 , the shrinkage rate, dielectric constant, porosity and flexural strength are 0.3%, 4.62, 1.97% and 160.72 MPa respectively. Thus, this study provides an environment-friendly and value-added approach to recycling photovoltaic waste and reducing the cost of the reactive sintering SiO 2 –Si 3 N 4 composite ceramics with excellent mechanical and dielectric properties. [ABSTRACT FROM AUTHOR]