An inverse gas-solid chromatographic study of the adsorption heterogeneity of aluminum oxide powders used in ceramic processing

Ceramic processing suffers from a paucity of information regarding the exact chemical nature of the surface of the raw material powders. Different lots powder (e.g. alumina), when used in the same process, may result in ceramics having vastly differing properties. A rapid, accurate method of measurement of the surface energy distribution of these materials would be valuable. Using alumina as a model material and porous layer open tubular columns, the methodology required to measure the adsorption isotherm by the Elution at a Characteristic Point (ECP) method has been developed. A critical discussion of the various steps involved, such as detector calibration and relationship between the chromatographic peak shape and the adsorption isotherm is presented. A new method for determination of the adsorption energy distribution function, which is applicable to any convex upwards adsorption isotherm, has been developed. This robust and accurate method offers several advantages over existing techniques which are discussed. The validity of the model and the accuracy of its solutions are critically evaluated. Finally, the reproducibility of thermodynamic parameters (e.g. average adsorption energy) obtained using specific probe solutes, and the ability of the method to discriminate between different samples having the same nominal composition is demonstrated.