Voici les éléments 1 - 10 sur 130
- PublicationAccès libreStatic Adsorption, by activated Carbons, of vapour Mixtures corresponding to immiscible Liquids(1999)
;Wintgens, D. ;Lavanchy, André
- PublicationAccès libreBinary Adsorption of Vapours in Active Carbons Described by the Dubinin Equation(1996)
;Lavanchy, André ;Stöckli, M. ;Wirz, C.
- PublicationAccès librePrediction of Filter Performances against Organic Vapours: Statistical Analysis of Breakthrough Times as a Basis for a Simple Prediction Model(2005)
;Lavanchy, André ;Liebi, R. ;Hugi-Cleary, DeirdreThe prediction of the protection efficiency of NBC-respiratory filters against organic vapours is often very difficult, especially when strong physical interactions or chemisorption processes are invoved. The presented statistical analysis is an attempt to develop a simple, but reliable, prediction model for breakthrough times. In over 70 experiments run under conditions of the EN 141 guidelines the breakthrough times of 39 organic compounds including alkanes, cyclo-alkanes, alkenes, alcohols, ketones and carboxylic acids have been measured for a given filter type. A linear regression model is then postulated to relate the breakthrough time to the adsorptive properties. For the model, each adsorptive molecule has been considered to be composed of a chemical functional group and a chain radical, resulting in a two dimensional structural code. The number of carbon atoms in the radical-chain and physical properties has been considered as an additional model parameter. General Linear Model (GLM) analysis was run to estimate model performances. We found out, that a simple linear model with only four regressors (two dimensional structural code, number of C atoms in the radical-chain and the saturation pressure) yields satisfactory breakthrough time predictions. Therefore, this study shows that, for a given filter type and well defined testing conditions, satisfactory predictions of breakthrough times of organic vapours are feasible.
- PublicationAccès libreThe Excess Enthalpies and Volumes of Mixing of 3-Methylhexane with Carbon Tetrachloride(1981)
;Quang Do, Kim ;Powell, BernardThe functions HE and VE have been measured between 293.15 and 303.15 K for the mixtures of (±), (+) and (-) 3 methylhexane with carbon tetrachloride, using improved calorimetric and dilatometric systems. As expected, it is found that the excess functions are identical for the optical isomers, within experimental error.
- PublicationAccès libreThe Characterization of Non-Porous Surfaces by Combination of the BET and the Dubinin-Radushkevich-Kaganer (DRK) Theories(2003)
;Hugi-Cleary, Deirdre ;Wermeille, Sandra
- PublicationAccès libreRecent Developments in the Context of the Dubinin-Astakhov Equation(1982)
; ;Lavanchy, A.Kraehenbuehl, F.The present work deals with two important aspects of the Dubinin-Astakhov equation, the fundamental relation of the theory for the filling of micropores. First, the theoretical basis of this equation is examined in the framework of a possible model, which leads to a reasonable agreement with experimental results. Secondly, it is shown how the D-A equation leads to an exact relation for the calculation of enthalpies of immersion of microporous carbons into organic liquids. So far, this relation has been tested with more than 35 systems (10 carbons and 8 liquids).
- PublicationMétadonnées seulementModelling of water adsorption by activated carbons: effects of microporous structure and oxygen content(2004)
;Slasli, A M ;Jorge, M ;Seaton, N AThe present paper examines the adsorption of water by microporous carbons containing various amounts of surface oxygen and a smaller proportion of basic centres. The modelling of water adsorption for 293 and 310 K, using variable pore size distributions (PSD), confirms that the overall type IV isotherm is the sum of a type I isotherm associated with the specific interactions, and a type V isotherm reflecting the non-specific interactions. The principle of temperature invariance is followed by these isotherms, which indicates that modelling leads to the Dubinin-Astakhov equation. The present approach allows the prediction of water adsorption near room temperature, on the basis of the PSD and the density of oxygen present on the surface area of the micropores. It is assumed, to a first and good approximation, that the pores are slit-shaped and the oxygen distribution is random. (C) 2004 Elsevier Ltd. All rights reserved.
- PublicationAccès librePhysical adsorption and the porosity of carbons, with special reference to the structure of micropores(1974)The problem of porosity in carbonaceous materials is briefly reviewed. Microporosity is investigated from the point of view of physical adsorption from the gas phase on graphite-like surfaces. Theoretical considerations show that the micropores can be treated as slots between the graphitic planes of the microcrystallites. The minima of the adsorption potentials are derived from the limiting heats of adsorption, measured by GSC.
- PublicationAccès libreApplications of Immersion Calorimetry in Dubinin’s Theory and Electrochemistry(2008)
;Centeno, Teresa A.This study shows that immersion calorimetry is a useful technique which simplifies considerably the analysis of porosity and chemical nature of activated carbons. The characterization of activated carbons in the general theoretical framework of Dubinin's theory with its extensions to calorimetry and adsorption from solutions allows the identification of some key parameters for the performance of these materials in electrochemical capacitors.
- PublicationAccès libreQuantum Mechanics and the Gravitational Red-shift(1969)It is shown that the formula for the gravitational red shift predicted by the theory of general relativity can also be derived by classical quantum mechanics combined with relativistic arguments. The agreement between the two derivations is a consequence of the separability of the time-dependent wave fonction, and of the first-order time differential in the wave equation.