液相聚合物前驱体法制备高熵碳化物纳米粉体

高熵碳化物陶瓷是近年来发展的新型材料, 由于具有高硬度、高模量和低热导率等优异性能而备受关注。液相聚合物前驱体法在陶瓷化过程中可以实现多元素的均匀分散, 制备高熵陶瓷具有独特的优势, 但是相关报道较少。本研究以金属醇盐为原料, 通过可控水解缩合反应制备了金属醇盐共聚物溶液, 加入碳源烯丙基酚醛(AN)后得到了澄清的粘稠液相高熵碳化物前驱体(PHEC), 在真空下1800 ℃裂解2 h获得了(Ti, Zr, Hf, Ta)C高熵碳化物陶瓷纳米粉末。通过不同手段对前驱体和陶瓷粉体进行表征, 结果表明: 裂解温度低于800 ℃所获得的样品主要为t-ZrO₂及氧化物固溶体, 1000 ℃开始发生碳热还原反应形成碳化物固溶体, 温度升高至1800 ℃后转化为高熵碳化物陶瓷; 所得陶瓷粉末纯度高, 元素分布均匀, 颗粒尺寸一致, 粒径~100 nm。制备的液相陶瓷前驱体具有高陶瓷产率(28.6 wt%)和低黏度(150 mPa?s)的特点, 在极性溶剂中溶解性良好。所开发的液相前驱体法在制备高熵陶瓷纳米粉体、陶瓷纤维和陶瓷基复合材料领域具有重要应用价值。

Synthesis of High-entropy Carbide Nano Powders via Liquid Polymer Precursor Route

High entropy carbide ceramics have been proposed in recent years for their promising properties as high hardness,high modulus and low thermal conductivity.Liquid polymer precursor method,of which multiple elements distribute homogeneously during the pyrolysis process,is considered to be favorable in fabricating high entropy ceramics.However,few reports have studied the synthesis of liquid precursor.In this work,liquid polymer precursor of(Ti,Zr,Hf,Ta)C were synthesized by co-hydrolysis and polycondensation of equiatomic metal containing monomers,and adding allyl-functional novolac resin(AN)as carbon source.The obtained polymer precursors of high entropy carbide ceramics(PHECs)were soluble in propyl alcohol and stable for months.The corresponding high entropy carbide ceramic nano powders were obtained by pyrolyzing PHEC at 1800℃for 2 h in vacuum.The precursors and ceramic powders were characterized by different methods.Results reveal that the ceramic sample pyrolyzed at 800℃are composed of t-ZrO₂and oxide solid solutions,and carbothermal reduction reaction began after pyrolyzed at 1000℃,with carbide solid solutions being generated.After being pyrolyzed at 1800℃,the samples convert to target high entropy carbide ceramics.As-obtained ceramics are characterized to be high purity with uniform distribution of nanosized particles(~100 nm).The synthesized precursor has high ceramic yield(28.6wt%),low viscosity(150 mPa·s),and good solubility in polar solvents.Therefore,the proposed liquid polymer precursor method is reliable in preparation of high entropy ceramic nano powders,ceramic fibers and ceramic matrix composites.