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

摘要： 为了在较低的温度下制备更细小的纳米碳化锆(ZrC)粉体,分别以氧化锆粉、氧氯化锆为锆源,纳米炭黑为碳源,无水乙醇、去离子水为介质,采用碳热还原法、液相先驱体转化法结合碳热还原法制备ZrC粉体,设置不同的n(Zr)∶n(C)(分别为1∶2、1∶3、1∶3.3、1∶3.6),优化热处理制度(1 200、1 400、1 600 ℃分段保温),并制备n(Zr)∶n(C)=1∶3且直接升温至1 600 ℃的对照粉体,研究锆源、n(Zr)∶n(C)、热处理制度对ZrC粉体显微结构和物相组成的影响。结果表明:在碳热还原反应过程中,在1 200 ℃保温 1 h可使m-ZrO₂完全转变为高活性c-ZrO₂,显著降低碳热还原活化能与反应能耗,再升温至1 600 ℃保温1 h即可获得晶粒尺寸100~200 nm的纯相多边形ZrC;继续增设1 400 ℃保温10 min,可促进晶核大量生成并抑制晶粒长大,将晶粒尺寸细化至 60~120 nm。当n(Zr)∶n(C)=1∶3时,采用氧氯化锆为锆源可实现反应物分子级混合,进一步将纯相ZrC细化至60~90 nm。该晶型调控与分段热处理思路为低成本、低能耗制备纳米ZrC粉体提供了可行路径。

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