Cost-effective synthesis of β-Si3N4 powder from recycled silicon waste for thermal conductive composites

Silicon nitride (Si 3 N 4 ) is regarded as promising material for various applications in the fields of electronics, chemistry and mechanics due to its outstanding properties. However, the high preparation cost has been one of the main obstacles that limits its large-scale industrial applications. Herein, we report a cost-effective strategy to synthesis high quality β -phase Si 3 N 4 powder by low-cost combustion synthesis method using recycled kerf loss silicon waste from photovoltaic industry . The effects of reaction pressure and additive on the oxygen content, phase composition, morphology and reaction mechanism of the prepared powders were investigated. Pure phase β -Si 3 N 4 powder of low oxygen content (0.95 wt%) was obtained at low combustion reaction pressure (2 MPa) with an environmentally friendly new additive C 3 H 6 N 6 . Thermal conductive silicon rubber composites were prepared by using the synthesized β -Si 3 N 4 powder as a filler. The effects of filler content on the microstructure, thermal, electric and mechanic properties of the fabricated polydimethylsiloxane (PDMS) composites were investigated. A high thermal conductivity of 1.4 Wm −1 K −1 was achieved in the PDMS composite with the addition of 80 wt% β -Si 3 N 4 powder, which is comparable to that of commercial β -Si 3 N 4 powder made from high purity silicon powder. This work proved that the recycled silicon waste from photovoltaic industry has the potential to be used as the silicon source for the cost-effective synthesis of high quality β -Si 3 N 4 powder for high thermal conductive composites applications .