Ceramic powder synthesis metal carbides

The reduction of oxides in reducing atmospheres is also an important industrial fluid—solid reaction that produces a powder. Because these types of reactions can affect ceramic powder synthesis, they are included in this chapter. However, these reduction reactions are frequently used to produce metal powders and are not often used to produce ceramic powders. These reduction reaction can, however, be the first step in a sequence of steps to produce carbide and nitride powders. Several examples of fluid—solid reduction reactions are... 

The first six reactions form mixed oxide ceramic powders. The last three reactions are carbothermal reductions to produce different metal carbides. The most famous is the Atcheson process for synthesis of SiC from Si02 and carbon, where the carbon in the mixture of reactant powders is used as a resistive electrical conductor to heat the mixture to the reaction temperature. This reaction is performed industrially in a 10-20 m long bunker fixed with two end caps that contain the source and sink for the cLc current. The reactant mixture is piled to a height of 2 m in the bunker and a current is applied. The temperature rises to the reaction temperatures, and some of the excess C reacts to CO, providing further heat. The 10-20 m bunker is covered with a blue flame for most of the reaction period. The resulting SiC is loaded into grinding mills to produce the ceramic powders and abrasives of desired size distributions. 

Mechanochemical processing has been used to manufacture nanocrystalline powders of nitride and carbide ceramics. The majority of systems involve milling of the metal precursor with a source of carbon or nitrogen. The source of carbon or nitrogen has typically taken the form of the element itself. However, a variety of other reagents have also been used. For example, Zhang et al. reported the synthesis of titanium nitride by milling titanium metal with pyrazine in a benzene solution. 

V. A. Gorshkov, G. N. Komratov, and V. I. Yukhvid, Production of cast higher chromium carbide using self-propagating high-temperature synthesis, Sov. Powder Metall. Met. Ceram. 1992, 31, 952-955. 

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