MnCO_3微球的可控制备、表征及高温热分解行为

Controlled Synthesis and Characterization of Manganese Carbonate Microspheres and Its Thermal Decomposition Behavior at High Temperature

以高锰酸钾(KMnO_4)为锰源,柠檬酸(C_6H_8O_7)为还原剂,采用水热合成技术在160℃条件下一步制备了碳酸锰(MnCO_3)微球。用X射线衍射(XRD)、扫描电镜(SEM)、同步热分析(TG-DSC)、傅里叶变换红外光谱(FT-IR)、N_2吸附脱附技术及激光粒度仪对制备产物的结构、形貌、热稳定性、孔结构和粒度分布进行了表征。系统研究了柠檬酸用量、反应温度、反应时间对合成产物晶型和形貌的影响,探讨了MnCO_3在空气氛围中不同温度下的热分解行为。研究结果表明,产物MnCO_3为介孔材料,其孔径、比表面积和孔容分别为20.9nm、27.9 m^2·g^(-1)和0.19cm^3·g^(-1)。柠檬酸用量对制备产物的晶体结构具有控制作用,其浓度达1.49mol/L时产物为高纯MnCO_3微球。反应温度和时间对产物MnCO_3的晶型和形貌几乎没有影响。MnCO_3在空气氛围中发生热分解,300~400℃时产物以MnO_2为主,560℃时煅烧产物为Mn_2O_3,1000℃时分解生成Mn_3O_4。

MnCO3 microspheres were successfully synthesized by treating KMnO4 in different concentration of citric acid solutions at 160℃ using one-step hydrothermal method.The structure,morphology,thermal stability,textural properties and granularity of the product were characterized by XRD,SEM,TG-DSC,FT-IR,nitrogen adsorption-desorption and laser granularity analyzer.The effects of citric acid dosage,reaction time and temperature on the structures and morphologies of manganese carbonate were investigated systematically.The thermal decomposition behavior of MnCO3 at different temperatures in the air atmosphere was preliminarily discussed.The experimental results indicated that the MnCO3 presented typical mesoporous structure,with pore size,specific surface area and pore volume of 20.9nm,27.9m^2·g^-1 and 0.19cm^3·g^-1,respectively.The citric acid dosage had significant influence on the crystal structures of as-prepared product,and MnCO3 microspheres with high-purity could be obtained under an optimized concentration of 1.49mol/L.Neither time nor temperature in the reaction process had obvious effect on the crystal form and morphology of manganese carbonate.MnCO3 underwent thermal decomposition in air atmosphere,MnO2 generated when the calcination temperature was 300-400 ℃,Mn2O3 appeared when the calcination temperature was 560 ℃,and the Mn3O4 was formed when the temperature reached 1000 ℃.