Dynamical aspects of the adsorption hysteresis phenomenon

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• 作者：Rustem Valiullin ; Sergej Naumov ; Petrik Galvosas ; Jö ; rg Kä ; rger ; Peter A. Monson
• 关键词：Adsorption hysteresis ; Mesoporous materials ; Self-diffusion ; Activated dynamics ; NMR
• 刊名：Magnetic Resonance Imaging
• 出版年：2007
• 出版时间：May 2007
• 年：2007
• 卷：25
• 期：4
• 页码：481-484
• 全文大小：157 K

文摘

Equilibrium and nonequilibrium transport properties of adsorbates in mesoporous Vycor porous glass have been experimentally studied using nuclear magnetic resonance techniques. With the known geometrical characteristics of porous glass and with measured self-diffusivities, transient sorption curves have been quantitatively compared to those predicted within a Fick's law model. This model correctly describes data outside a hysteresis region. In contrast, in the hysteresis region, a two-step mechanism of density relaxation is required to explain the behavior. These two mechanisms are identified as diffusion at early stages and activated density redistribution at later stages of adsorption. The latter mechanism, being intrinsically slow in nature, is anticipated to prevent the system from reaching equilibrium.