carbide is manufactured industrially by the electrochemical reaction of high purity quartz sand with carbon in an electric resistance furnace (Acheson process):



Preferred carbons are petroleum coke (pitch coke) and anthracite. Addition of sodium chloride ensures the removal of troublesome impurities as volatile chlorides. The presence of sawdust increases the porosity of the reaction mixture and eases outgassing. 

The electric furnaces, in which this reaction is carried out, are ca. 15^.3^.3 m³ in size and are lined with refractory material. Electrodes at opposite ends are connected to a graphite core. The furnace is filled round this core with the reaction mixture and electrically heated to 2200 to 2400°C. The heating up time is ca. 18 h and the reaction time a further ca. 18 h. After cooling, the sides of the furnaces are removed and the unreacted material on the edges removed. The , which has formed round the graphite core, is broken up and separated into different qualities.

The purest SiC is bright green (99.8% SiC), the color changing with decreasing Sic-content from dark green (99.5% SiC) to black (99% SiC) to gray (90% SiC). 70 t of raw mixture yields 8 to 14 t of high grade SiC and 6 to 12 kWh of energy are required to produce 1 kg of raw silicon carbide.

The raw silicon carbide is processed by crushing in jaw crushers or hammer mills and subsequent fine grinding in ball mills. Very pure SiC qualities are obtained by chemical treatment with sulfuric acid, sodium hydroxide or hydrofluoric acid.

Silicon carbide is remarkable for its unusually large variety of different morphologies, which differ in their stacking sequences of hexagonal and rhombohedral layers. All hexagonal and rhombohedral forms are often simply described as α-SiC. The commercially available SiC produced by the Acheson process is α-SiC.

The manufacture of cubic β-SiC, which is favored at temperatures below 2000°C, or mixtures of α- and β-SiC is carried out by deposition from the gas phase (Chemical Vapor Deposition). β-SiC powder with good sintering properties and small crystallite size is e.g. obtained by the thermal decomposition of alkyl silanes or alkyl dichlorosilanes in plasmas or tlow reactors at temperatures above 1000°C:

In another process metallic silicon is evaporated in an electrical arc and reacts with methane to silicon carbide. A disadvantage of all gas phase processes is their high cost compared with the Acheson process.