Production of nano-sized chromium carbide powders from Cr2O3/C precursors by direct electrochemical reduction in molten calcium chloride

• Direct electrochemical synthesis of chromium carbide from Cr2O3/C precursors
• A Cr2O3/C mixture was directly electrolyzed without a sintering step.
• Influences of electrolysis parameters on the electrolysis process were investigated.
• Analysis on the formation mechanism of chromium carbide was done.

Chromium carbides were synthesized by direct electrolysis of non-sintering Cr2O3/C precursors in CaCl2 molten at 1123 K. A series of electrolysis experiments were conducted with different Cr2O3/C molar ratios, cell voltages and electrolysis time. The products were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive spectrometer (EDS) techniques, respectively. The results showed that the single-phase Cr7C3 powders with a mean diameter of < 200 nm were prepared after electrolysis at 2.8 V for 5 h in 1123 K CaCl2 melt. By prolonging the electrolysis time to 10 h, the product was converted into a Cr7C3 and Cr3C2 composite. Carbon was not only used as a raw material, but could also accelerate the rate of electrochemical reduction of Cr2O3. The reaction procedure forming the chromium carbides involved the electro-deoxidation of Cr2O3 and combined with carbon simultaneously.