Mechanisms Of Gas Sorption Hysteresis In Ink-Bottle-Type Pores Confirmed
The mechanisms of gas sorption hysteresis in ink-bottle-type pores have been confirmed in a recent paper (January 2006) published in Langmuir (volume 22, pages 756-764 (2006)) titled "Adsorption Hysteresis of Nitrogen and Argon in Pore Networks and Characterization of Novel Micro- and Mesoporous Silicas". The authors, Matthias Thommes (Quantachrome Instruments), Bernd Smarsly and Matthijs Groenewolt (Max-Planck Institute of Colloids and Interfaces) and Peter Ravikovitch and Alexander Neimark (Center for Modeling and Characterization of Nanoporous Materials at TRI/ Princeton) report that adsorption measurements with different adsorptives now allow one to identify and separate the effects of pore-blocking and cavitation-controlled evaporation (desorption). Results of nitrogen and argon adsorption experiments performed at 77K and 87K on novel micro/ mesoporous silica materials demonstrate that cavitation is the dominant mechanism of desorption in SE3030, KLE, and KLE/IL silicas with ordered networks of cylindrical and/or spherical pores. In contrast, percolation effects, rather than cavitation, contribute to the hysteresis observed in the disordered pore network of Vycor glass. What is demonstrated, therefore, is that cryogenic adsorption/desorption experiments performed with different adsorptives allows one to identify and separate the effects of pore blocking/percolation and cavitation during desorption. By using a novel hybrid nonlocal density functional theory (NLDFT) method which takes into account the effect of delayed capillary condensation in pores of different geometries, pore size distributions can be calculated just from adsorption isotherms over the entire range of micro- and mesopores.
Dr. Matthias Thommes (Quantachrome's Director of Applied Science) is a world renowned researcher in the area of adsorption and nano-porous materials, author of numerous scientific papers and co-author of a highly respected monograph on characterization of such materials. Dr. Thommes has given more than 30 presentations at prestigeous international scientific meetings, and is a member of International Advisory Committees on many conferences. Dr. Thommes was recently appointed to the Advisory Board of the journals Particle & Particle Systems Characterization and Adsorption Science and Technology.
The Max Planck Institute of Colloids and Interfaces located in Potsdam, Germany, is concerned with structures at the nano- and micrometer level. Current research focuses on nanostructures in amphiphilic systems, biomimetic mineralization, biocompatible materials, polyelectrolyte multilayers, the use of structured surfaces, and the self-organization of membranes.
The Center for Modeling and Characterization of Nanoporous Materials at TRI/ Princeton is an internationally recognized leader in porous materials science and engineering. They specialize in the adsorption of gases and vapors in porous solids, and the absorption and spreading of liquids on fibers, structured substrates, and porous & fibrous materials.
SOURCE: Quantachrome Instruments