Powders of Chromium and Chromium Carbides of Different Morphology and Narrow Size Distribution

Powders of Cr and Cr carbides (Cr2C, Cr7C3, and Cr23C6) have been prepared by hydrogen reduction of CrO1.9 and Cr3C2 powders of different morphology, texture and specific surface area. The Cr and Cr carbides particles have the morphology of the parent compound and a narrow size distribution. Depending on the shape, the average size is of the order of some micrometers or some tens of micrometers. Starting with Cr3C2 allows the preparation of Cr powders at a temperature (1000°C) markedly lower than that required when CrO1.9 is used as the precursor (1300°C). However, a Cr3C2 specific surface area of the order of 10 m2/g is necessary to achieve this within a reasonably short time (6 to 12 h). Powders of the lower carbides are prepared by using a milder hydrogen thermal treatment.