Synthesis of B4C/CrB2 Powders by Boron-Carbide Reduction Using Nanofiber Carbon for the Fabrication of Ceramics

The results of studying the process of obtaining B4C/CrB2 powder mixtures by the boron-carbide reduction of chromium oxide Cr2O3 in the presence of nanofiber carbon and the results of studying some properties of ceramics made using the synthesized powder are presented. By the method of thermodynamic modeling, it is found that the minimum temperature of the complete reduction of Cr2O3 by the boron-carbide reduction method is 1540°С at a pressure of ⁓0.08 MPa. The characteristics of powders containing 10–70 mol % of the CrB2 phase are studied. The average size of 50% of the powder particles for the studied compositions does not exceed 11 µm. The specific surface area of the samples does not exceed 6 m2/g. The oxidation of the resulting mixtures with oxygen in air begins at a temperature of ~550°С. At the same time, when the temperature reaches 1000°С, no more than 65 wt % of powders is oxidized. Ceramics made using the synthesized powder mixture B4C–10 mol % CrB2 by hot pressing have a relative density of 95% and fracture toughness of 5.25 ± 0.15 MPa m0.5.