Study on Relation between Morphological Change of Crack Pattern in Powder Solid and Slow Dynamics

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The morphological change of broken powder solids defined as fragile solid-like materials, in which a lot of adhesive powders with random sizes are glued each other, has been investigated according to analogies with two transitions in particle systems, the glass and jamming transitions. Concerning to a dynamical property of the adhesive powders, the slow dynamics, which is a typical phenomenon in glassy materials, is observed near the transition point of the morphological change from cracking to crumbling. On the other hand, concerning to a static property of the powder materials such as the mean contact number per a particle versus the volume fraction, the power law function is observed, but the value of the exponent differs from that of reported value near the jamming transition point which is considered to be a universal value as a scaling exponent. Thus, we suggest that the morphological change is not directly related to the jamming transition at least from the view point of the critical phenomena.