硅藻土负载AgO复合材料的制备及热分解非等温动力学

采用化学氧化沉淀法,以过硫酸钾为氧化剂制备了硅藻土负载过氧化银(AgO)复合材料,并使用X射线衍射仪(XRD)、扫描电子显微镜(SEM)和激光粒度仪对其进行了表征,借助热重(TG)分析研究了复合材料的热分解过程和非等温热分解动力学.结果表明,制备的复合材料为正方晶系方英石和单斜晶系AgO混合体,且AgO质量分数为12.7%;复合材料的中位径为18.53μm,比表面积为203.32 m2/kg,颗粒的粒度分布在0.614～116.5μm之间.复合材料中AgO在171℃开始分解成Ag2O,在更高温度时Ag2O进一步分解成Ag;热分解反应服从以核生成和核成长为控制步骤的A1机理,其热分解表观活化能为131.37 kJ/mol,反应频率因子为3.19×1013 s-1.同自制的AgO粉末相比,复合材料中AgO的热分解温度升高,表观活化能上升约40 kJ/mol.

Preparation and Non-isothermal Kinetics of Thermal Decomposition of AgO-loaded Diatomite Composite

AgO-loaded diatomite composite was prepared by chemical oxidation-deposit method using potassium persulfate as oxidant.The composite was characterized by X-ray diffraction,scanning electron microscope and the laser particle size analyzer.The process and kinetic behavior of thermal decomposition of the composite were studied by means of thermogravimetry.The results show that the AgO-loaded diatomite composite with a AgO content(mass fraction) of 12.7% is made up of tetragonal christobalite and monoclinic silver peroxide.The size of the composite is in the range of 0.614—116.5 μm and the median-particle-size and specific surface area of the composite are 18.53 μm and 203.32 m2/kg,respectively.The composite decomposes at 171 ℃ along with the formation of silver oxide followed by decomposing into silver at higher temperature.The mechanism of decomposition reaction is random nucleation and subsequent growth mechanism(A1),and the apparent activation energy and reaction frequency factor are 131.37 kJ/mol and 3.19×1013 s-1,respectively.Compared with reference silver peroxide powders,the thermal decomposition temperature of the composite rises and a considerable increase of the activation energy up to 40 kJ/mol was observed.