Adsorption isotherms of fractal surfaces
Adsorption isotherms of fractal surfaces
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DOI：
10.1016/s0927-7757(02)00063-8
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发表时间：
2002-07-09
影响因子：
5.2
通讯作者：
Wong, PZ
中科院分区：
文献类型：
--
作者：
Qi, H;Ma, J;Wong, PZ
利用货车德瓦尔斯相互作用研究惰性分子在分形表面上的吸附，是一种探索分形维数D的方法，但至今仍缺乏令人信服的证据。我们已经使用小角散射（SANS），以确定三个页岩样品的孔隙表面尺寸，并进行了氮吸附研究。我们发现，根据现有的理论预测分析吸附等温线总是导致D值低于SANS获得的D值。所有三种样品的理论曲线也存在系统性偏差。为了了解这些问题的起源，我们使用了幂律分布的非耦合球形孔作为分形表面的代表，并进行了数值模拟的吸附等温线。我们发现，模拟的等温线表现出相同的实验中观察到的一般特征。VDW效应和毛细凝结之间的交叉总是发生，它排除了使用等温线来确定D在真实的系统。(C)2002 Elsevier Science B.V.保留所有权利。
Adsorption of inert molecules on fractal surfaces by Van der Waals (VDW) interactions has long been proposed as a method to probe the fractal dimension D but convincing evidence is still missing after more than a decade. We have used small angle scattering (SANS) to determine the pore surface dimensions for three shale samples and carried out nitrogen adsorption studies. We found that analyzing the adsorption isotherm according to the available theoretical predictions always resulted in D values that are lower than those obtained by SANS. There are also systematic deviations from the theoretical curve common to all three samples. To understand the origin of these problems, we used a power law distribution of uncoupled spherical pores as a representation of a fractal surface and carried out numerical simulations of the adsorption isotherm. We found that the simulated isotherms exhibit the same general features observed in the experiment. A crossover between the VDW effect and capillary condensation always occurs and it precludes the use of isotherms to determine D in real systems. (C) 2002 Elsevier Science B.V. All rights reserved.