Silicon carbide refractories are classified, according to the method of bonding the silicon carbide granules, as siliceous (formed in the oxidation of carbide), nitride (Si3N4), oxynitride (Si2ON2), and aluminosilicate, as well as recrystallized and self-bonded. The products are formed on presses (or by other methods) from powdered mixtures containing silicon carbide and subsequently fired at 1300°-1550°C (certain types at 2000°-2200°C).
Silicon carbide refractories exhibit high thermal conductivity: 7-17 watts per (m.°K) at 800°C. As a result, they show good thermal stability. They are also resistant to deformation at elevated temperatures. At 130O°-1500°C in an oxidizing medium they undergo gradual oxidation, particularly in the presence of an excess of oxygen and of water vapor. Silicon carbide refractories are used in recuperators, retort furnaces, nonferrous-metal-lurgy plant units, shelves of tunnel wagons (in firing porcelain and ceramics), and boilers.
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