AFM and low-pressure argon adsorption analysis of geometrical properties of phyllosilicates
Résumé
The distribution of edge and basal surface areas of phyllosilicate particles is an essential parameter for understanding the interaction mechanisms at solid/gas or solid/liquid interfaces. Among the techniques proposed to determine the geometrical heterogeneities of flat solids, low pressure argon adsorption and AFM analysis are the most promising ones to derive the weight-averaged values of specific surface areas. A series of publications [1,2] have been recently dedicated to the combination of both methods showing the correlation between the two approaches. As the obtention of a large set of high resolution AFM images is time consuming it is necessary to test the ability of AFM routine analysis to derive systematically and statistically surface areas and aspect ratio, with all possible experimental and instrumental artefacts. In the present study, the expected agreement was found between AFM and argon adsorption determination for total, basal and edge specific surface areas of non swelling clay minerals, except for one kaolinite, which is very heterogeneous in sizes. In addition, it was observed that for a given sample, individual particles present similar shapes, whatever their size, allowing to derive statistical relationship between AFM basal and total surface areas. On the basis of the obtained results, recommendations are given to derive accurate edge, basal and total specific surface areas of phyllosilicates by combining conventional gas adsorption (nitrogen BET) and routine AFM techniques.
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