Dawson结构(NH_4)_6P_2Mo_(18)O_(62)·12H_2O纳米粉体的室温固相合成及形成机理

Preparation and Formation Mechanism of Dawson Structure (NH_4)_6P_2Mo_(18)O_(62)·12H_2O Nano-powders by Solid State Reaction at Room Temperature

以H6P2Mo18O62·23H2O和(NH4)2C2O4·H2O为原料,首次采用室温固相反应合成出(NH4)6P2Mo18O62·12H2O纳米粉体,并运用元素分析、FTIR、XRD、TEM、TG-DTA和BET等技术对其组成、结构和性能进行了表征。发现(NH4)6P2Mo18O62·12H2O纳米粉体平均粒径为40nm,保留着杂多阴离子的Dawson结构,具有Dawson结构的特征衍射峰,比表面积为143.9m2·g-1,在445℃以下杂多阴离子有良好的热稳定性。在该固相反应中,研磨和放热反应热能可加速反应物分子的扩散速率和生成物分子的成核速率,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)6P2Mo18O62·12H2O纳米粉体起关键作用。

NH4)6P2Mo18O62·12H2O nano-powders were prepared by the solid state reaction of H6P2Mo18O62·23H2O with (NH4)2C2O4·H2O at room temperature. The nano-powders were characterized by elemental analysis, FTIR, XRD, TEM, TG-DTA and BET techniques. The experimental results indicate that the nano-powders were found still to exhibit Dawson structure and had the mean grain size of 40 nm and BET specific surface area of 143.9 m2·g-1. The heteropolyanion had a higher thermal stability at a temperature below 445 ℃. In this solid state reaction, grinding and reaction thermal energy could accelerate the speed of reactant molecular diffusion and product molecular nucleation while decreasing the particle′s size, water of crystallization of reactants and product H2C2O4·2H2O played a key role in forming the small size (NH4)6P2Mo18O62·12H2O nano-powders.