Adsorption and Phase Transitions in Slit-like Pores with Differently Adsorbing Walls.
We study the adsorption of a lattice gas in a slit-like pore with different walls. The density profiles are evaluated in the framework of the mean-field approximation. We show that changes in the potential field exerted by one wall can lead to substantial modifications of the phase behavior of the fluids. Copyright 2001 Academic Press.
Confined fluids in a Janus pore: influence of surface asymmetry on structure and solvation forces
Density distribution, fluid structure and solvation forces for fluids confined in Janus slit-shaped pores are investigated using grand canonical Monte Carlo simulations. By varying the degree of asymmetry between the two smooth surfaces that make up the slit pores, a wide variety of adsorption situations are observed. The presence of one moderately attractive surface in the asymmetric pore is sufficient to disrupt the formation of frozen phases observed in the symmetric case. In the extreme case of asymmetry in which one wall is repulsive, the pore fluid can consist of a frozen contact layer at the attractive surface for smaller surface separations (H) or a frozen contact layer with liquid-like and gas-like regions as the pore width is increased. The superposition approximation, wherein the solvation pressure and number density in the asymmetric pores can be obtained from the results on symmetric pores, is found to be accurate for , where is the Lennard-Jones fluid diameter and within 10% accuracy for smaller surface separations. Our study has implications in controlling stick slip and overcoming static friction ‘stiction’ in micro and nanofluidic devices.
Étude de l'adsorption par ellipsométrie: adsorption du Xe/(0001) graphite
The adsorption isotherms of xenon on the perfectly homogeneous (0001) face of graphite are known with great accuracy through classical volumetric measurements, LEED and Auger diffusion. Ellipsometric measurements have led to the same results. The formation of five successive monolayers and two phase transitions in the first monolayer have been shown. The ellipsometric signal Δ which is related to the formation of one monolayer varies linearly with the layer number, with only a slight discrepancy for n= 4.5. In the first monolayer the ellipsometric signal Δ varies linearly with the coverage ratio θ, 0 < 9 < 1. The detection sensibility corresponds to 1100th of a monolayer.