Irreversible volume growth in polymer-bonded powder systems: effects of crystalline anisotropy, particle size distribution, and binder strength

Pressed-powdered crystallites of intrinsically anisotropic materials have been shown to undergo irreversible volume expansion when subjected to repeated cycles of heating and cooling. In a previous letter publication [R. H. Gee et al., Appl. Phys. Lett. 70, 254105 (2007)], we developed a coarse-grained (micron-scale) interaction Hamiltonian for such a system and quantitatively reproduced experimentally observed irreversible growth through explicit molecular dynamics simulations. In this paper, we report (1) recent experiments with a high-density fluoropolymer binder that significantly lowers irreversible growth, (2) identification of a critical interaction parameter of our model that has a strong correlation with binder properties, (3) sensitivity of irreversible growth to the details of particle size and alignment distribution, and (4) a physical picture of irreversible growth in terms of particle displacements.