纳米晶碳化锆粉体的制备及热力学机制  

Preparation and Thermodynamics Mechanism of Nanocrystalline ZrC Powders

作　　者：李榕[1] 宋绍雷[1,2] 王亚丽[1] 甄强[1,2] 

机构地区：[1]上海大学纳米科学与技术研究中心,上海200444 [2]上海大学材料科学与工程学院,上海200444

出　　处：《稀有金属》2015年第7期605-610,共6页Chinese Journal of Rare Metals

基　　金：国家自然科学基金面上项目(51272154)资助

摘　　要：以氧氯化锆、氨水、乙醇为原料,通过化学沉淀法获得含氢氧化锆沉淀的悬浊液,向悬浊液中加入可溶性蔗糖作为碳源,均匀混合后将悬浊液烘干得到前驱体粉体。将前驱体粉体压成圆柱形坯体,在流动的氩气气氛保护下进行高温固相反应来合成Zr C粉体。通过热力学计算分析了碳热反应合成Zr C的反应机制及适宜的温度和CO分压条件。计算结果表明反应式Zr O2+3C=Zr C+2CO(g)的标准生成吉布斯自由能在1900 K以上为负值;而随着CO分压的降低,反应的标准生成吉布斯自由能随之降低。通过X射线衍射(XRD)分析研究了前驱体的Zr/C摩尔比、反应温度、反应时间以及氧分压对高温反应产物物相的影响,优化了Zr C的合成条件。进一步的热力学分析表明,氧分压足够低时Zr C才能稳定存在。最终采用蔗糖作为碳源,Zr/C摩尔比设为1∶3,将前驱体包埋在活性炭中并在流动的高纯氩气保护下经1600℃反应240 min后得到的立方相Zr C粉体,粉体颗粒近球形,小于100 nm。Using ZrClO2,NH3·H2O and ethanol as raw materials,suspension solution containing zirconium hydroxide precipitates were obtained by precipitation method. Sucrose used as carbon source was added into the suspension solution and homogeneously mixed,and then the suspension solution was dried to obtain the precursor. The precursors were pressed into green pellets,and treated in the flow of argon at elevated temperature to synthesize Zr C powders by solid state reaction. Through thermodynamic calculation,the carbon thermal reaction mechanism was analyzed,and the suitable reaction temperature and the partial pressure of CO were also determined. The calculation results showed that the standard Gibbs free energy of reaction ZrO2＋ 3C = ZrC ＋ 2CO（ g） was negative when the temperature was above 1900 K,and the value decreased with the partial pressure of CO decreasing. The effects of Zr/C ratio of precursor,reaction temperature and time,and O2 pressure on the phases of high temperature reaction products were investigated by Xray diffraction（ XRD） analysis,and the synthesis condition was optimized. Further thermodynamic analysis showed that Zr C was stable only when the oxygen partial pressure was low enough. Finally,cubic phase Zr C was obtained by embedding the precursor in activate carbon and sintering at 1600 ℃ for 240 min in high purity argon flow with sucrose as carbon source and Zr/C molar ratio of 1∶3. The particles were spherical and the sizes were smaller than 100 nm.

关 键 词：固相合成 碳化锆 热力学计算 纳米晶 

分 类 号：TB383[一般工业技术—材料科学与工程]