Twofold Description of the Texture of Aluminium Oxides Prepared by the Sol—Gel Method

Abstract

To date, a complete assessment of the so-called pore-size distribution by adsorption methods has, in general, not been accomplished. This is because the diverse capillary phenomena involved in such a description of the porous structure usually undergo cooperative and/or percolative interactions which hinder complete characterization. The object of the present work was to suggest a general method for the analysis of texture and to provide specific examples which identify and describe some of the problems and possibilities of the textural characterization of porous substrata from vapour adsorption studies. A series of alumina products of very assorted morphologies were synthesized using a modified Yoldas sol-gel method, and used to demonstrate important morphological and mechanical aspects of the pore structure from the observation and analysis of their nitrogen adsorption hysteresis loops at 76 K.

Effect of Boehmite Crystallite Size and Steaming on Alumina Properties

“…The initial slopping character on the descending boundary curves observed for PSB-C and PSB-S (Figure ) reflects the porous structure shrinkage caused by stress change of the condensate during depressurization. This is due to swelling of parallel grain plates by adsorbed nitrogen, because the structures in these samples were less rigid than those found for aluminas derived from BOE. The plateau of the descending boundary curve of PSB-C and PSB-S indicates an appreciable pore blockage.…”

“…Analysis of the hysteresis loop shape by using the descending boundary curve (DBC) 20-22 technique provides information about pore blocking and pore structure rigidity in alumina samples. The hysteresis loop shape of aluminas derived from BOE (Figure ) corresponds to structures of medium strength without pore blockage . Therefore, steaming had only a weak effect on pore size distribution (Figure ).…”

“…The pore size distribution and shape are closely related to the hysteresis loop classified by IUAPAC, BET, or BDDT . The analysis of the adsorption−desorption isotherms was complemented following criteria on the inspection of the hysteresis loop shape based on the so-called descending boundary curve (DBC) …”

Estudio de fenómenos capilares en medios porosos: sorción de nitrógeno y porosimetría de mercurio. Acuerdos y discordancias

“…El DSBM, permite construir de manera sencilla medios porosos de diversa naturaleza [4][5][6][7][8] y estudiar algunos fenómenos capilares que ocurren en ellos, como son: a) la sorción de nitrógeno con la ayuda de métodos analíticos [9-13] y de Monte Carlo [14][15][16][17]; b) retracción e intrusión de mercurio [18][19][20], los cuales son casos especiales de la imbibición y drenaje respectivamente; c) crecimiento de burbujas [21,22]. También se ha explicado y simulado la formación de agregados arbóreos de partículas de sílice [23], morfología de polímeros [24] y de productos de agregación provenientes de la transición sol-gel [25,26], así como superficies catalíticas [27][28][29], etc.…”