Non-Metallic Covalent Carbides

The atomic and crystalline structure of the two non-metallic carbides, boron and silicon carbides, is less complex than that of the 

The two covalent carbides have low density, low atomic weight, and useful semiconductor properties. They are extremely hard and strong materials which exhibit typical ceramic characteristics. 

In this chapter, each carbide is listed alphabetically with its basic properties, its major CVD reactions and processes, and its present and potential applications. 

Boron carbide is a non-metallic covalent material with the theoretical stoichiometric formula, B4C. Stoichiometry, however, is rarely achieved and the compound is usually boron rich. It has a rhombohedral structure with a low density and a high melting point. It is extremely hard and has excellent nuclear properties. Its characteristics are summarized in Table 9.2. 

Chemical Resistance. Boron carbide resists oxidation in air up to 600°C due to the formation of a film of B2O3. Its chemical resistance is generally excellent although it reacts with halogens at a high temperature. 

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