Koparde Vishal N, Cummings Peter T
Department of Chemical Engineering, Vanderbilt University, Nashville, Tennessee 37235, USA.
ACS Nano. 2008 Aug;2(8):1620-4. doi: 10.1021/nn800092m.
The size below which anatase nanoparticles become more stable than rutile nanoparticles (crossover diameter) is dependent on the environment of the nanoparticles. It is smaller for nanoparticles in vacuum than those in water and continues to decrease with increase in temperature. Phase transformation between anatase and rutile phases is facilitated by enhanced ionic mobility at temperatures near the melting point of the nanoparticles. Multiparticle multiphase molecular dynamics simulations of TiO(2) nanoparticles undergoing sintering-induced phase transformations are reported here. Over the time scales accessible to molecular dynamics simulations, we found that the final sintering agglomerate transformed to the rutile phase, provided one of the sintering nanoparticles was rutile, while sintering of anatase and amorphous nanoparticles resulted in a brookite agglomerate. No such phase transformations were observed at temperatures away from nanoparticle's melting temperatures.
锐钛矿型纳米颗粒比金红石型纳米颗粒更稳定时的尺寸（交叉直径）取决于纳米颗粒所处的环境。真空中纳米颗粒的交叉直径比水中的更小，且随着温度升高而持续减小。在接近纳米颗粒熔点的温度下，离子迁移率增强促进了锐钛矿相和金红石相之间的相变。本文报道了TiO₂纳米颗粒烧结诱导相变的多颗粒多相分子动力学模拟。在分子动力学模拟可及的时间尺度上，我们发现如果烧结纳米颗粒之一是金红石型的，最终烧结团聚体转变为金红石相，而锐钛矿型和无定形纳米颗粒烧结则产生板钛矿团聚体。在远离纳米颗粒熔点的温度下未观察到此类相变。
