Propriétés du film de krypton adsorbé sur la face (0001) du graphite préalablement recouverte d'hexafluorure de soufre

Theory and Observation of Displacement Phenomena in Coadsorbed Films

“…Yet CH 4 , a relatively inert gas with a much weaker attraction to graphite, succeeds, at low temperatures, in displacing a preadsorbed monolayer film of CCl 4 from graphite and adsorbing directly onto the substrate [2]. Displacement of a more condensable species by a relatively inert species is observed in a number of similar systems, such as Kr͞C 6 H 12 [2,3], Kr͞CCl 4 [4,5], Xe͞SF 6 [6], and Kr͞SF 6 [7,8]. We present here a simple thermodynamic model of displacement and compare it with experimental data for the Kr͞CCl 4 and CH 4 ͞CCl 4 coadsorption systems.…”

“…The primary experimental evidence for displacement has come from coadsorption isotherms [2][3][4][5][6][7], which measure the film coverage of the inert gas species (species 2), as a function of its vapor pressure or chemical potential, dm 2 , in the presence of the preadsorbate (species 1) film (dm 2 ϵ m 2 2 m 0 2 , chemical potential measured relative to bulk saturation). Typically small preadsorbate saturated vapor pressures (ഠ10 220 Torr for CCl 4 at 77 K [9]) permit accurate measurement of the species-2 vapor pressure.…”

Structural characterization of krypton physisorption on (0001) graphite pre-plated with cyclohexane

“…Structural characterization of krypton physisorption on (0001) graphite pre-plated with cyclohexane A. Razafitianamaharavo (1), P. Convert (2), J. P. Coulomb (3), B. Croset (4) and N. Dupont-Pavlovsky (1) (1) CNRS, Laboratoire Maurice Letort, 54600 Villers les Nancy, France (2) Institut Laue Langevin, 156 12,1990, accepted in final form on May 18,1990) Résumé. 2014 Le film mixte formé lors de la physisorption de krypton sur une surface de graphite (0001) pré-recouverte d'une monocouche de cyclohexane a été étudié par diffraction de neutrons et de rayons X. L'organisation de la couche mixte prévue à partir des résultats obtenus par volumétrie d'adsorption sur une surface très uniforme (graphite exfolié) est dans son ensemble conservée sur les échantillons de graphite exfolié recomprimé (Papyex) utilisés pour les expériences de diffraction, malgré les difficultés d'atteinte de l'équilibre d'adsorption liées à la densité du Papyex.…”

“…Within the last few years, structural characterizations of these films have been carried out and in some cases 2D solid solutions have been evidenced [1][2][3][4][5][6][7]. When the respective temperatures of condensation of the two adsorbates are very different, classical volumetric measurements can be applied to the thermodynamic characterization of the composite film by means of the preadsorbed layer technique, which was introduced by Halsey and Singleton [8], and extended later on [9][10][11][12][13]. The most condensable adsorbate is introduced first at relatively high temperature, in order to control the adsorption equilibrium ; the sample is then cooled down to the temperature of the second component adsorption.…”

“…This technique was used for the last two systems studied, Kr-SF6/graphite [12] and Kr-C-,6H12/graphite [13]. In both cases, krypton adsorption was shown to result in the displacement of the pre-adsorbed film.…”