Fabrication of Silicon Carbide from Recycled Silicon Wafer Cutting Sludge and Its Purification

Abstract

Around the world, silicon carbide (SiC) is used as a raw material in several engineering applications because of its various beneficial properties. Currently, though the Acheson method is one of the most emblematic to manufacture SiC, the direct carbonization of metallic silicon is simple and beneficial. In this reaction, silicon wafer cutting sludge can be used as an alternative silicon source material. The silicon wafer sludge contains silicon, ethylene glycol, cooling water, and a small amount of impurities. In this study, SiC was synthesized using silicon wafer sludge by a carbothermal process. In a typical experiment, the silicon sludge was mixed with carbon at different molar ratios. Then, the mixture was turned into pellets, which were placed in alumina crucibles and heat-treated at a temperature from 1400 °C to 1600 °C to fabricate SiC. To deduce the optimum condition for the synthesis of SiC, an investigation was carried out on the effects of different mixing ratios, temperatures, and heating times. To ensure sufficient carbonization, excess carbon was mixed, and the synthesized SiC was characterized by X-ray diffraction (XRD). Subsequently, purification of the synthesized SiC products by oxidation of excess carbon was performed. The removal of extra carbon could be confirmed by XRD and attenuated total reflectance (ATR) spectroscopy. This process can give basic information for the development of a technology to produce SiC using recycling Si wafer cutting sludge waste.