Carbon coagulation in a nonstationary detonation-product flow

Evolution of Carbon Clusters in the Detonation Products of the Triaminotrinitrobenzene (TATB)-Based Explosive PBX 9502

“…To describe the dynamics of carbon clustering in detonation products, we adopted the diffusion-limited reaction rate model originally developed by Shaw and Johnson, and later modified/generalized by several groups. ,,, This model is thoroughly described elsewhere ,,, and will be outlined here only briefly. The growth of carbon clusters is described by the rate equations where C n is the concentration of carbon clusters containing n carbon atoms.…”

“…Implications of this disagreement and possible remedies for modeling were recently discussed . Feasible mechanisms capable of slowing down carbon clustering to match the experimental observations included accounting for “evaporation” or fragmentation of carbon clusters, a large activation barrier of cluster fusing, or an unrealistically large viscosity of the detonation products . Less direct estimations of the carbon cluster formation times, based on electrical conductivity measurements, interferometry, and finite HE stick radius effects, as well as gas gun experiments, seemed to agree better with theoretical predictions than the TR-SAXS results cited above.…”

“…The reaction zone of carbon-rich HEs often consists of two stages, schematically shown in Figure A. − The first fast stage is referred to as the “fast reaction zone” and, akin to ideal HE detonation, is thought to be associated with formation of gaseous products. The excess carbon, liberated during this fast reaction zone, then undergoes slow “carbon clustering” , (also referred to as carbon condensation − or coagulation − ), where smaller clusters gradually coalesce into larger ones. The excess carbon has been shown by recovery studies to form solid carbon residues of various allotropes and morphologies (e.g., graphite, amorphous carbon, nanodiamonds). − At even longer time scales, carbon clusters may aggregate, without significant fusing, and form fractal networks. ,, While this general framework is largely accepted, quantitative understanding of the dynamics of carbon clustering in detonation of carbon-rich HEs has still been largely inaccessible, and has implications for post-detonation forensics, nanodiamond synthesis, and HE performance modeling.…”