| Budget Amount *help |
¥14,000,000 (Direct Cost: ¥14,000,000)
Fiscal Year 2002: ¥1,700,000 (Direct Cost: ¥1,700,000)
Fiscal Year 2001: ¥12,300,000 (Direct Cost: ¥12,300,000)
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| Research Abstract |
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
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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
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