Development of Integrated Method for Nanopore Characterization Based on Peculiar Phase Behavior of Fluids Confined in Nanospace

许多具有重要工业意义的多孔材料都具有纳米级的孔道。纳米孔的孔径表征通常是通过氮气吸附来完成的，使用所谓的开尔文凝聚模型进行分析，尽管吸附科学家已经达成共识，开尔文模型在纳米孔径范围内存在低估的缺陷，这是缺乏合适的工程模型来估计纳米级孔径的直接证据。本研究是基于对纳米空间中受限流体的特殊相行为的理解，即孔壁的相互作用势能会阻碍受限流体的相界，从而建立一个简单而准确的纳米孔表征模型。研究结论如下：1.研究结果。吸附等温线测量：我们先前提出的模型的有效性，该模型解释了孔壁势能对临界冷凝…的贡献通过使用FSM-16的检查，证明了纳米孔中的压力更大。此外，还测量了固体材料(包括多孔和非多孔)和吸附物质的不同组合的等温线，这将代表确定相互作用能强度的数据库。相互作用强度：之前提出的另一种用于计算氮气与孔壁之间相互作用强度的模型，被发现需要对相互作用较弱的吸附物进行改进。由此发展了一种新的模型，该模型利用低压力范围的Henry等温线，凝聚模型可以估计一致的孔尺寸，而无论使用何种吸附物，Kelvin模型当然不能像Kelvin模型那样成功。原子力显微镜(AFM)研究冻结转变：利用胶体探针AFM技术，测量了碳颗粒与浸泡在环己烷中的石墨衬底之间形成准狭缝纳米空间的力曲线，确定了不同尺寸纳米空间的凝固点。计算结果与上述测定的相互作用强度基本一致。在上述结果的基础上，结合分子模拟的结果，证实包含孔壁相互作用强度这一重要因素的相变模型能够足够准确地描述纳米孔中流体的相行为，这代表了基于纳米空间中特殊相行为的纳米孔表征的综合方法。较少

Many of industrially important porous materials possess nanometer order of pores. Pore size characterization for nanopore is usually done through nitrogen adsorption, using so-called the Kelvin condensation model for the analysis, although it is already common understanding for adsorption scientists that the Kelvin model has a deficit of the underestimation in the nanometer range of pores, which is a direct evidence for the lack of a suitable engineering model for estimating nanoscale pore size. The present study is to develop a simple and accurate model for nanopore characterization, based on the understanding of peculiar phase behavior of fluids confined in nanospace, where the interaction potential energy of pore wall would hinder the phase boundaries of the confined fluids. The conclusions are as follows.1. Adsorption isotherm measurement: The validity of our previously proposed model that accounts for the contribution of the pore-wall potential energy to the critical condensation … More pressure in nanopores was demonstrated through examination employing FSM-16. Further, isotherms with various combination of solid materials (both porous and nonporous) and adsorbates were measured, which would stand for the database for determining strength of interaction energies.2. Interaction strength: Another previously proposed model, which is for finding the interaction strength between nitrogen and a pore wall, was found to need improvement for adsorbates with weaker interaction. A new model utilizing Henry region of isotherm with lower pressure range was thus developed, with which the condensation model can estimate consistent pore sizes regardless of the adsorbate employed -- The Kelvin model can not of course be as successful.3. Study of freezing transition by atomic force microscopy (AFM): Employing so-called the colloidal probe AFM technique, the force curves between a carbon particle and a graphite substrate immersed in cyclohexane, which form quasi-slit nanospace, were measured and the freezing points in various sizes of nanospace were determined. The results were found to be consistent with the interaction strength determined as above. Thus a unique physical property of the interaction strength was able to describe both condensation and freezing phenomena comprehensively.Based on the above results, as well as those employing molecular simulations, it is concluded that the phase transition models including the important factor of the pore-wall interaction strength were confirmed to be able to describe the phase behavior of fluids in nanopores with sufficient accuracy, which now stand for the integrated method for nanopore characterization based on the peculiar phase behavior in nanospace. Less