溶胶-凝胶法载银SiO_2杂化材料的红外光谱和热分析

FTIR and Thermal Αnalysis of Silver-doped Hybrid Silica Material by Sol-gel Method

采用溶胶-凝胶法在甲基化改性SiO2溶胶中掺杂硝酸银制备了Ag/MTES-SiO2杂化材料.通过XRD、红外光谱和TG-DTG分析考察了Ag/MTES-SiO2杂化材料的热稳定性,结合Coast-Redfern积分法和Achar微分法求算了Ag/MTES-SiO2杂化材料在热分解过程中各阶段的活化能和指前因子.结果表明,Ag/MTES-SiO2杂化材料经120℃以上焙烧后,样品中出现了纳米金属Ag粒子.随着焙烧温度的升高,Ag粒子的衍射峰强度和SiO2颗粒结晶的趋势增加.当焙烧温度达到600℃时,Si—CH3基团完全消失,至750℃时,残余C—H基团完全无机化.在N2气氛中,Ag/MTES-SiO2杂化材料中—CH3的无机化历程经历了4个阶段,各阶段具有不同的热分解动力学机理函数,其活化能分别为71.92,125.78,235.73和417.37 kJ/mol,指前因子分别为1.18×109,7.14×1010,8.35×1013和1.16×1020 s-1.

Ag/MTES-SiO2 hybrid material was prepared by sol-gel method,in which AgNO3 was added into methyl-modified silica sol.According to XRD,FTIR spectra and TG-DTG analysis,the thermal stability of Ag/MTES-SiO2 hybrid material was discussed.The activation energies and frequency factors were figured out by Coast-Redfern intergral method and Αchar differential method.The results show that metallic nano-silver peaks can be clearly found in the silica materials calcined above 120 ℃.The metallic silver is obtained from the reduction of AgNO3.The Si—CH3 vibrational bands disappear completely when the calcination temperature increased to 600 ℃,which mineralized when the calcination temperature further increased to 750 ℃.The introduction of Ag nanoparticles nearly has no influence on the thermal stability of —CH3 groups.As the calcining temperature increased,the diffraction peaks of metallic silver in intensity and the tendency of silica particles to form crystals increase.There are four steps in the thermal decomposition of Ag/MTES-SiO2 materials in N2 atmosphere,with different mechanism functions.The activation energies are 71.92,125.78,235.73 and 417.37 kJ/mol,and the frequency factors are 1.18×109,7.14×1010,8.35×1013 and 1.16×1020 s-1 for the four steps,respectively.