Ta_2O_5-NaF-C体系制备TaC晶须的机理  

Growth mechanism of TaC whiskers synthesized via Ta_2O_5-NaF-C system

作　　者：王骏[1] 李国栋[1] 熊翔[1] 张磊[1] 

机构地区：[1]中南大学粉末冶金国家重点实验室,长沙410083

出　　处：《粉末冶金材料科学与工程》2016年第1期65-71,共7页Materials Science and Engineering of Powder Metallurgy

基　　金：国家重点基础研究发展规划("973"计划)资助项目(2011CB605805)

摘　　要：利用Ta2O5-NaF-C混合粉末为原料,采用碳热还原法在石墨表面制备不同形态的碳化钽晶须,利用SEM和XRD对晶须的形貌、结构与成分进行观察与分析,采用热力学计算与实验验证相结合的方法研究不同形貌碳化钽晶须的生长机制。结果表明:TaC晶须存在不同的生长机制,当原料粉末添加量较少时,石墨表面主要生长出圆柱状晶须伴有头部液滴状结构,原料粉末添加量较多时得到规则的四方柱状结构晶须,也存在2种不同形貌晶须并存的情况。圆柱状晶须为VLS(气-液-固)生长机制;四方柱状TaC晶须为VS(气-固)生长机制。在VLS机制中,催化液滴的主要成分为Na Ta O3。TaC whiskers with two kinds of morphologies were fabricated on graphite surface with mixed Ta2O5-NaF-C powders as raw materials by carbothermal reduction method. The morphology, microstructure and phase composition of the whiskers were observed and analyzed by SEM and XRD. The growth mechanism of TaC whiskers with different shapes were investigated through thermodynamics calculation and experimental verification. The results show that there exist different growth mechanisms of TaC whiskers. When the addition of raw powders is lower, cylinder-shaped whiskers with liquid-drop-shaped on the whisker top are obtained. When the addition of raw powders is higher, square pillar-shaped whiskers are obtained, and cylinder-shaped whisker are also observed. The cylinder-shaped whiskers grow via a VLS mechanism; square pillar-shaped whiskers grow via a VS mechanism. In VLS mechanism, Na Ta O3 acts as a catalyst.

关 键 词：碳热还原 TaC晶须 Ta2O5-NaF-C体系 形貌 生长机制 

分 类 号：TQ174[化学工程—陶瓷工业]