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

Abstract

Composite ceramics are applied widely nowadays by combining superior properties of different ceramic materials. In this study, SiO2–Si3N4 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 (N2, NH3, N2–H2) and SiO2 content (0%, 10%, 20%, 30%, 40%) on the microstructure and properties of composite ceramics were studied. It shows that the synthesis of SiO2–Si3N4 composite ceramics can be obtained in the NH3 atmosphere, and it is inevitable to form the Si2N2O phase in N2 and N2–H2 mixture atmospheres. Furthermore, the shrinkage rate and dielectric constant of the ceramics decreased as SiO2 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 SiO2 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 SiO2 content of 30%. For the sintered ceramic with 30% SiO2, 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 SiO2–Si3N4 composite ceramics with excellent mechanical and dielectric properties.