Krypton, atomic area

For graphite layer, the number density per unit area n = 38.2 centers/nm, the minimum potential energy between a krypton atom and the graphite layer is... 

Nitrogen and krypton physisorption measurements at 77 K and hydrogen chemisorption measurements at 293 K were carried out with a Belsorp 28SA automatic adsorption apparatus in order to obtain BET surface area and the number of surface nickel atoms, respectively. The structure of catalysts was determined by X-ray diffraction using Cu radiation. 

Fischer et al, [122] proposed a model to predict the adsorption isotherm of krypton in porous material at supercritical temperature. In their study, a model pore of infinite length is formed by concentric cylindrical surfaces on which the centers of solid atoms are located. The interaction between an adsorbate and an individual center on the pore wall is described by the LJ 12-6 theory, and the overall potential is the integral of this interaction over the entire pore surface. With thermodynamic relations, Fischer et al. obtained the functional dependence of the saturation adsorption excess and the Henry s law constant on the pore structure. The isotherm was then produced by the interpolation between Henry s law range and saturation range. They tested their theory with the adsorption of krypton on activated carbon. It was shown that, with information on the surface area of the adsorbent and thermodynamic properties of the adso bate, their model gives more than quantitative agreement with experimental data. If a few experimental data such as the Henry s law constant at one temperature are available, the isotherms for all temperatures and pressures can be predicted with good quality. 

Nitrogen has been by far the most widely employed adsorbate at -196°C. In similar facilities, argon and krypton can also be used and suitable values for atomic aoss sectional areas are known (23). The advantage of krypton for penetrating smaller pores was shown by Vezina and Berube (24). 

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