碳化法制备氧化锌前躯体热力学分析及其产物表征

Thermodynamic analysis on preparation of zinc oxide precursor by carbonation method and characterization of its products

分析了碳化法制备氧化锌前躯体过程的热力学,研究了碳酸氢铵用量及其加入方式、硫酸锌溶液浓度和温度对前躯体的影响,并用差热-热重（TG-DTA-DTG）、X射线衍射仪（XRD）、扫描电镜（SEM）对产物进行表征。结果表明,由热力学计算得到生成碱式碳酸锌[Zn5（CO3）2（OH）6]的吉布斯自由能最小,为-170.429 9 kJ/mol;采用碳酸氢铵和硫酸锌溶液并流加入,在碳酸氢铵和锌离子的物质的量比为2.4∶1、锌离子浓度为0.4 mol/L、反应温度为40℃的条件下,得到前躯体;通过TG-DTA-DTG,XRD分析,前躯体以碱式碳酸锌的形式存在,其分解温度在170~330℃,分解时直接放出二氧化碳和水得到活性氧化锌。SEM分析表明该前驱体为片状固体,平均粒径约为0.4μm。

Thermodynamics in preparation process of zinc oxide precursor by carbonation method was analyzed.Influences of the amounts and addition ways of ammonium bicarbonate,concentration of zinc sulfate solution and temperature on precursor were studied and the product was characterized by TG-DTA-DTG,XRD,and SEM.Results showed that Gibbs free energy of generation of basic zinc carbonate [Zn5（CO3）2（OH）6] calculated by thermodynamics was the smallest,which was-170.429 9 kJ/mol;precursor was obtained under the processing conditions as follows：ammonium bicarbonate and zinc sulfate solutions were added with paralled flow,n（NH4HCO3）∶n（Zn2＋）=2.4∶1,concentration of Zn2＋ was 0.4 mol/L and reaction temperature was 40 ℃.From the analysis of TG-DTA-DTG and XRD,precursor was existing in the form of basic zinc carbonate;decomposition temperature of precursor was 170～330 ℃;decomposition directly emitted carbon dioxide and water and activated zinc oxide was formed finally.SEM showed the precursor was flake-like solid with the average size of about 0.4 μm.