Due to the low natural content, silicon carbide is mostly artificial. The standard method is to mix quartz sand with coke, use the silica and petroleum coke, add salt and wood chips, put it into an electric furnace, heat it to a high temperature of about 2000 °C, and obtain silicon carbide powder after various chemical processes.
Silicon carbide (SiC) is an essential abrasive because of its high hardness, but its application range is beyond ordinary abrasives. For example, it has high-temperature resistance and thermal conductivity and is one of the preferred kiln materials for tunnel kiln or shuttle kiln. Its electrical conductivity makes it an essential electric heating element.
SiC products’ preparation first requires the preparation of SiC smelting blocks or: SiC granules, which contain C and are super hard, so SiC granules were once called: emery. But be careful: it is different from the natural corundum (also known as garnet).
In industrial production, SiC smelting blocks are usually made of quartz, petroleum coke, etc., which are auxiliary materials and materials. After mixing, they are blended into a reasonable proportion and suitable particle size. (To adjust the gas permeability of the charge, it is necessary to add the appropriate amount. The wood chips are prepared by adding high-quality salt when preparing green silicon carbide.
The thermal equipment for preparing SiC smelting block at high temperature is a special silicon carbide electric furnace. Its structure consists of the bottom of the stove, the end wall with electrodes on the inner surface, the detachable sidewall, and the core body (full name: the electric heating body of the electric furnace center, generally Graphite powder or petroleum coke is installed in the center of the charge according to a specific shape and size, typically circular or rectangular, and its two ends are connected with electrodes.
The firing method used in the electric furnace is commonly referred to as burying powder. When it is energized, the heating starts. The core body temperature is about 2500°C or even higher (2600 ~ 2700°C). When the charge reaches 1450°C, the synthesis of SiC is started (but SiC is mainly formed at ≥ 1800°C), and CO is released. However, SiC will decompose at ≥ 2600°C, but the decomposed Si will form SiC with C in the charge. Each group of electric furnaces is equipped with a set of transformers. Still, only a single electric furnace is supplied for the power supply so that the voltage can be adjusted according to the electric load characteristics to maintain constant power. The high-power electric furnace is heated for about 24 hours, and the reaction of generating SiC after the power failure is finished. After a cooling period, the sidewall can be removed, and the charge can be gradually removed.