摘要
首次以H4SiW12 O40·2 2H2 O和 (NH4) 2 C2 O4·H2 O为原料 ,室温固相反应合成出 (NH4) 4 SiW12 O40 纳米微粒 ;用元素分析、FTIR确定产物的组成和结构 ;XRD、TEM和BET对产物的形貌、晶粒尺寸和比表面积进行了表征 ;TG DTA确定了产物的稳定温区 .结果表明 ,产物为纳米粒子 ,平均粒径为 6 0nm ,比表面积为 10 8.7m2 /g ,在 4 30℃以下具有良好的热稳定性 .在固相反应中 ,研磨和放热反应热效应能加快反应物扩散速率和生成物成核速率 ,使产物粒径减小 ;反应物含有结晶水和生成物H2 C2 O4·2H2 O ,对形成小粒径的 (NH4) 4 SiW12 O40 纳米粒子起关键作用 .
(NH4)(4)SiW12O40 nanoparticles were prepared firstly by the solid state reaction of H4SiW12O40.22H(2)O with (NH4)(2)C2O4.H2O at the room temperature. The nanoparticles were characterized by elemental analysis. FT-IR, XRD, TEM, TG-DTA and BET techniques. The experimental result indicates that the nanoparticles were found still to exhibit Keggin structure and had the mean grain size 60 nm and BET specific surface areas 108.7 m(2)/g. The nanometer materials had a higher thermal stability at a temperature below 430degreesC. The forming mechanism of nanoparticles has also been discussed. In this solid state reaction, grind and reaction thermal energy could accelerate the speed of H4SiW12O40.22H(2)O with (NH4)(2)C2O4.H2O diffusion and its product (NH4)(4)SiW12O40 nucleation while decreasing particles size. The water of crystallization of reactants forms easily small water cells in the reaction and restricts (NH4)(4)SiW12O40 particle size, and the product H2C2O4.2H(2)O crystal play a key role in prohibiting (NH4)(4)SiW12O40 crystal growth and forming the small size of nanoparticles.
基金
ProjectsupportedbytheEducationOfficeKeyResearchofHubeiProvince (2 0 0 0Z0 10 0 9)andtheKeyResearchofHubeiUniversity (A0 0 2 0 )
