关键词: ZrC, 碳热还原法, 液相先驱体法, c-ZrO₂, 晶核形成, 低成本

Abstract: To prepare finer nano zirconium carbide (ZrC) powder at low temperatures,zirconia powder and zirconium oxychloride were used as zirconium sources,nano carbon black as the carbon source,and absolute ethanol and deionized water as media.Two preparation routes were adopted,including the carbothermal reduction method and liquid precursor conversion method combined with carbothermal reduction.Different n(Zr)∶n(C) molar ratios (1∶2,1∶3,1∶3.3 and 1∶3.6) were designed,and the hot system was optimized by stepwise heat preservation at 1 200,1 400 and 1 600 ℃.Meanwhile,a reference sample with n(Zr)∶n(C)=1∶3 was prepared by direct heating to 1 600 ℃.The effects of the zirconium source,Zr/C molar ratio and hot treatment system on the phase composition and microstructure of ZrC powders were investigated.The results show that holding at 1 200 ℃ for 1 h with carbothermal reduction can completely convert m-ZrO₂ into high-activity c-ZrO₂,which significantly reduces the activation energy and energy consumption of the reaction.Pure-phase polygonal ZrC with grain size of 100-200 nm can be obtained by further heating to 1 600 ℃ and holding for 1 h.An additional heat preservation at 1 400 ℃ for 10 min promotes abundant nucleation and restricts grain growth,refining the grain size to 60-120 nm.Under the molar ratio of n(Zr)∶n(C)=1∶3,the adoption of zirconium oxychloride as the zirconium source realizes molecular-level mixing of reactants and further refines pure-phase ZrC grains to 60-90 nm.This crystal form regulation and stepwise sintering strategy provides a feasible route for preparing nano ZrC powders with low cost and low energy consumption.

Key words: ZrC, carbothermal reduction method, liquid precursor conversion method, c-ZrO₂, nucleation, low-cost