Porous SiO₂–Si₃N₄ Composite Ceramics Sintered by Carbothermal Nitridation of Diamond-Wire Sawing Silicon Waste

A novel process regarding carbothermal nitridation of diamond-wire sawing silicon waste powder (DSSWP) was developed to fabricate porous SiO₂–Si₃N₄ composite ceramics. The process involves the following two sequential steps: preparation of the α-Si₃N₄ whiskers at 1350 °C for 3 h in an ammonia atmosphere using the starting material of DSSWP and 20 wt% SiO₂, and sintering porous SiO₂–Si₃N₄ composite ceramics at 1420 °C for 3 h using 68 wt% α-Si₃N₄ whiskers generated in 1st step, 20 wt% SiO₂, 4 wt% MgO, 4 wt% Al₂O₃, and 4 wt% C, respectively. The results indicated that the porosity, dielectric constant, flexural strength, and fracture toughness of composite ceramics were 23.6%, 3.72, 132.72 MPa, and 12.61 MPa·m^1/2, respectively, showing 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.

Flow sheet of preparing the porous SiO₂-Si₃N₄ composite ceramics sintered by carbothermal nitridation of DSSWP