Kinetic and mechanistic decomposition studies on advanced energetic materials

摘要

The objective of this dissertation was to determine the decomposition characteristics of several newer energetic materials under combustion-like conditions by T-jump/FTIR spectroscopy. Hydrazinium nitroformate (HNF) was examined between 130-400$spcirc$C, which includes melt/foam decomposition and self-ignition regimes. Reaction regimes included evaporation, conversion to $rm NHsb4lbrack C(NOsb2)sb3rbrack,$ and progressive decomposition to $rm COsb2,$ CO, N$sb2$O, NO, and H$sb2$O. Induction-time decomposition kinetics $(Esb{rm a}$ = 25 kcal/mol, ln (B, s$sp{-1})$ = 25.3) of the melt/foam layer were determined from time-to-exotherm and agree reasonably well with previously reported temperature-profile data.;Thirteen 5- and 6-member nitrogen heterocycles and acyclic compounds were shown to convert into melon-like, cyclic azine residues when heated to $Tge500spcirc$C. The gaseous products were also determined by IR spectroscopy. The melon-like residue could suppress the burning rate if these compounds are formulated into solid rocket propellants.;Discrepancies in the published global kinetic data for the thermal decomposition of 5-nitro-2,4-dihydro-1,2,4-triazol-3-one (NTO) were shown to result partly from inadequate consideration of the competing processes of sublimation and thermal decomposition. These processes were isolated and their kinetics determined. For sublimation, $Esb{rm a}=25.8$ kcal/mol, ln (A, s$sp{-1})=29.2$ (isothermal at 0.002 atm); $Esb{rm a}=28.6$ kcal/mol, ln(A, s$sp{-1})=31.3$ (nonisothermal at 0.002 atm). Decomposition kinetics on semi-confined NTO (20 atm Ar pressure) determined by T-jump/FTIR spectroscopy yield $Esb{rm a}=87.1$ kcal/mol and ln (A, s$sp{-1})=74.8.$ From these and reported data, the kinetic constants for decomposition alone are $Esb{rm a}=78{-}87$ kcal/mol and ln (A, s$sp{-1})=67{-}78.$ Lower values of the Arrhenius parameters result predominately or partly from sublimation.;An evaluation was made of whether T-jump/FTIR spectroscopy could determine the decomposition kinetics $(Esb{rm a}$ and ln A) and thermochemical $(Delta Hsb{rm d})$ constants of an energetic material at high temperature and high heating rate. Polystyrene peroxide (PSP) was selected, and the kinetic constants were found to be appropriate for O-O bond homolysis as the rate determining step: $Esb{rm a}=39$ kcal/mol, ln (A, s$sp{-1})=21.5.$ Significant uncertainty exists, however, in the estimation of $Delta Hsb{rm d}.$.