Synthesis of Zirconium Carbide via Carbothermal Reduction: Phase and Microstructural Evolution with CaF2 Catalysis and Thermodynamic Study

ZrC was synthesized using sol-gel-like methods and carbothermic reduction techniques, employing Zr(OPr n ) 4 and carbon black as raw materials and CaF 2 as catalyst. High-crystallinity ZrC were obtained after a 20-minute hold at 1550°C. The effects of CaF 2 content and heat treatment temperature on structural transformation of the precursor, phase evolution, microstructural evolution and elemental composition analysis, as well as to analyze the catalytic mechanism of CaF 2 were investigated. The results indicated that this method enables effective and uniform mixing of ZrO 2 and carbon black. Adding CaF 2 promoted the deoxygenation of ZrO 2 and ZrC x O 1-x to ZrC, reducing the initial formation temperature of ZrC to 1300°C. The carbothermal reaction was nearly complete at 1500°C, yielding a composition of ZrC 0.951 O 0.049 at 1600°C. Thermodynamic calculations showed that CaF 2 react with ZrO 2 to form an intermediate phase of ZrF 4 , altering the reaction mechanism and reducing the theoretical initial synthesis temperature of ZrC to 1000°C.