Keggin结构纳米硅钨酸铵的室温固相合成与物性

首次以H4SiW12O40 * 22H2O和(NH4)2C2O4 * H2O为原料,室温固相反应合成出(NH4)4SiW12O40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60 nm,比表面积为108.7 m2/g,在430℃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H2C2O4 * 2H2O,对形成小粒径的(NH4)4SiW12O40纳米粒子起关键作用.

Synthesis and Properties of the Keggin Structure (NH4)4 SiW12 O40 Nanoparticles by Solid State Reaction at Room Temperature

(NH4)4SiW12O40nanoparticles were prepared firstly by the solid state reaction of H4SiW12O40·22H2O with (NH4)2C2O4·H2O at the room temperature. The nanoparticles were characterized by elemental analysis, FTIR, XRD,TEM, TG-DTA and BETtechniques. The experimental result indicates that the nanoparticles were found still to exhibit Keggin structure and had the mean grain size 60 nm and BETspecific surface areas 108.7 m2/g. The nanometermaterials had a higher thermal stability at a temperature below 430℃. The forming mechanism of nanoparticles has also been discussed. In this solid state reaction, grind and reaction thermal energy could accelerate the speed ofH4SiW12O40·22H2O with (NH4)2C2O4·H2O diffusion and its product (NH4)4SiW12O40nucleationwhile decreasing particles size. The water of crystallization of reactants forms easily small water cells in the reaction and restricts (NH4)4SiW12O40particle size, and the productH2C2O4·2H2O crystal play a key role in prohibiting (NH4)4SiW12O40crystal growth and formingthe small size of nanoparticles.