超临界干燥法制备MnO2气凝胶及其表征

Characterization of MnO_2 Aerogels Prepared via Supercritical Drying Technique

以高锰酸钾和反丁烯二酸为原料,采用溶胶-凝胶法和超临界干燥工艺制备了MnO2气凝胶.利用扫描电镜(SEM)、透射电镜(TEM)、X射线衍射(XRD)、X射线光电子能谱(XPS)、BET比表面积测定、红外光谱及热重与差热等实验技术对气凝胶的多孔形态、结构特性、凝胶产物的组成进行了表征,并研究了脱水热处理温度对气凝胶结构的影响.结果表明:选择合适的反应物摩尔比,可合成锰的平均价态接近4的MnO2凝胶.最终的MnO2气凝胶为亲水型非晶态块状多孔材料,它由纳米级胶体粒子聚集而成,呈连续、相互贯通的三维多孔网络结构(粒子的平均直径约10nm,平均孔径100nm).气凝胶的空间网络结构特征在常规脱水温度热处理过程中不会受到明显的破坏.

The MnO2 aerogels were prepared from KMnO4 and allomaleic acid via sol-gel process and supercritical drying technique. The porous morphology, structure and composition of the aerogels were characterized by SEM, TEM, XRD, XPS, BET surface area, IR and TG/DSC. The effects of dehydration temperature on the aerogels structure were investigated. The results indicate that the proper mole ratio of reactants is favorable to the syntheses of MnO2 gels with the average valence states of manganese being close to 4. The resuiting aerogels are hydrophilic, non-crystalline and monolithic porous materials with continuous, interpenetrate and three-dimensional network structure, which consist of nanoscale MnO2 colloidal particles with mean particles size of 10nm and mean pore diameter of 100nm. The aerogels morphology maintain unchanged during the heat treatment of dehydration at conventional temperature.