Identification of impact attrition mechanisms in solution by morphological analysis

Image analysis was used to characterise quantitatively the shapes of single crystals impacted against a target. The conditions of impacts are created to simulate the impacts undergone by the crystals in an industrial crystalliser. The change of particle morphology due to attrition enables to understand the abrasion and breakage mechanisms of the crystals after one or several collisions. The projected area, the elongation, the robustness, the concavity characterise the evolution of the crystal shape as a function of the number of impacts. The crystal becomes rounded and its shape irregular. The quantification of the length and of the propagation of the created cracks is done. Cracks are initiated by the impacts and propagate to join one another, creating a fragment finally removed from the particle. (C) 2000 Elsevier Science S.A. All rights reserved.