Effects and function mechanism of Fe‐containing additives on SiC synthesis with silicon cutting waste

With the rapid development of the photovoltaic industry, a great amount of silicon cutting waste (SCW) are being generated, which lead to a heavy environmental burden as well as a high cost of the photovoltaic industry. In this paper, the effects of Fe‐containing additives and their function mechanism on recycling SCW to synthesize high‐purity SiC were studied. The results show that Fe‐containing additives, including Fe, Fe2O3, and Fe(NO3)3, have obvious effect on recycling SCW to synthesize SiC. And Fe(NO3)3 additive achieves the best effect. Fe(NO3)3 can effectively destroy the SiO2 film wrapped on the Si particles, so that expose the inner Si to C at lower temperatures than that of the reaction between C and SiO2. Besides, Fe(NO3)3 additive can effectively reduce the activation energy both for Si and C reactions and SiO2 and C reactions, and contribute to the transport of the raw materials as well as the dissolution and precipitation of Si and C due to the formation of the FeSi melt at low temperatures. The optimal processing conditions are determined as Fe(NO3)3 addition of 1–3 wt.% and smelting temperature of 1200–1300℃. Phenolic resin decompose and give birth to high‐reactivity C; while Fe(NO3)3 takes a form transition to Fe2O3 and final FeSi; assisted with these up‐two process, silicon cutting waste (SCW) is capable of transforming into SiC with the consumption of SiO2 that wrap on the SCW's surface at relatively low temperatures.