Recycling the diamond-wire saw silicon powder for preparing the regulable Si3N4 materials by non-catalytic nitridation

In this paper, the diamond-wire saw silicon powder (DWSSP) solid waste in the photovoltaic industry was recycled to prepare silicon nitride through the nitridation method. Nitridation dynamics and reaction mechanisms of DWSSP were investigated in detail. The results showed that the kinetic model of nitriding DWSSP was more suitable for the grain model controlled by the combination of diffusing through the product layers and accumulation pores. Meanwhile, two paths to destroy the dense silicon oxides shell covered on the surface of DWSSP were illustrated during the nitridation process. They were the indirect nitridation to generate the silicon oxynitride fibers and the direct nitridation to form the silicon oxynitride granules, respectively. Morphology and composition of products were mainly determined by the nitriding temperature and time. The pure silicon nitride powder was obtained from DWSSP nitrided at 1550 °C for 10 h. Interestingly, a core-shell structure particle of silicon nitride as core and silicon oxynitride as the shell was prepared at 1450 °C for 10 h, which possible could be a pretty raw material for fabricating the silicon nitride-based composite ceramics with special performances.