Kuzmin Vyacheslav, Safiullin Kajum, Stanislavovas Andrey, Tagirov Murat
Kazan Federal University, Kazan, 420008, Russian Federation.
Phys Chem Chem Phys. 2017 Aug 30;19(34):23146-23153. doi: 10.1039/c7cp03949b.
We performed He gas diffusion measurements for the first time in a highly porous ordered AlO aerogel sample at a temperature of 4.2 K using a nuclear magnetic resonance field gradient technique. A strong influence of He adsorption in the aerogel on self-diffusion is observed. The classical consideration of adsorptive gas diffusion in mesopores leads to anomalously high tortuosity factors. The application of a more sophisticated model than the simple combination of empirical two-phase diffusion and the Knudsen gas diffusion models is required to explain our results. Anisotropic properties of the aerogel are not reflected in the observed gas diffusion even at low gas densities where the anisotropic Knudsen regime of diffusion is expected. The observed gas densification indicates the influence of the aerogel attractive potential on the molecular dynamics, which probably explains the reduced diffusion process. Perhaps this behavior is common for any adsorptive gases in nanopores.
我们首次使用核磁共振场梯度技术，在温度为4.2 K的高度多孔有序AlO气凝胶样品中进行了氦气扩散测量。观察到气凝胶中氦吸附对自扩散有强烈影响。介孔中吸附性气体扩散的经典考量导致异常高的曲折因子。需要应用比经验性两相扩散和克努森气体扩散模型简单组合更复杂的模型来解释我们的结果。即使在预期有各向异性克努森扩散机制的低气体密度下，气凝胶的各向异性特性也未在观察到的气体扩散中体现出来。观察到的气体致密化表明气凝胶吸引势对分子动力学的影响，这可能解释了扩散过程的减缓。也许这种行为对于纳米孔中的任何吸附性气体都是常见的。
