Analysis of polydisperse ball-milled fluorite powders using a full pattern technique

M. Leoni¹, G. De Giudici², R. Biddau², P. Scardi¹

¹ University of Trento, Department of Materials Engineering and Industrial Technologies, 38050 via Mesiano 77, Trento, Italy

² Univerity of Cagliari, Department of Earth Sciences, 09100 via Trentino 51, Cagliari, Italy.

X-ray powder diffraction is particularly suited to the analysis of nanocrystalline materials. Both structural and microstructural information can nowadays be obtained simultaneously by full pattern processing techniques.

Among those, Whole Powder Pattern Modelling (WPPM) outperform most traditional Line Profile Analysis (LPA) techniques by giving a direct interpretation of the diffraction pattern in terms of physical microstructural models. In the present work we illustrate a recent evolution of the WPPM approach, allowing the refinement of a general domain-size distribution, not related to any a priori fixed analytical profile or size distribution shape. Besides the description of the new algorithm we show the results of the analysis of ball milled synthetic fluorite powders. The new WPPM procedure provides a detailed information on the evolution of the grinding process with time: the decrease and change of shape of the grain size distribution with the milling time is accompanied by a steady increase in defect content. The increased defectivity is shown to be a main responsible for the higher reactivity and therefore for the high dissolution rates shown by ball-milled fluorite powders.

Acknowledgement

This work was supported by the basic research funds of the Italian Ministry of University and Research, PRIN 2003-2004 project "Mechanisms of surface interactions in mineral phases: kinetics of dissolution, of crystal growth and their modeling"