Abstract

AbstractUltrafine diamond dust and the metastable fullerenes C60 and B24N36 offer new pathways of energy release which are unattainable in conventional energetic materials. Theoretical and experimental studies indicate that the high bare-surface strain energies of these small particles are released in rapid (< 1 μsec) phase changes. For diamond, C60 and B24N36, strain energies of 1000, 1210 and 1245 cal/g, respectively, may be released during transition to graphite, diamond and hexagonal BN under pressures exceeding 100 kbar. It is shown that the behavior of these nanoscale particles under high shocks may be traced to their intrinsic five-fold and icosahedral symmetry, which leads to an incompatibility of global and local driving forces for space filling under high compression. From a correlation function analysis, it is shown that shear can induce long range correlations of fluctuations which arise from geometrical frustration, thereby reducing the activation energy for phase change. For the first time, critical stresses and symmetry rules are determined for such phase changes in aggregates of nanoscale particles.

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