The effect of detonation polycrystalline diamond modification on the thermal decomposition of RDX

A well-dispersed micron-scale detonation polycrystalline diamond (DPD) was prepared and modified on RDX particles, preparing four DPD-modified RDX (DMR) composites with the modification amount increasing from 1/9 to 1/3. The effect of modification on the thermal decomposition and kinetics of RDX was studied using dynamic pressure measuring thermal analysis (DPTA), differential scanning calorimetry (DSC) and thermogravimetric analysis (TG) techniques. As the modification amount increased, the gas emission, reaction rate constant, decomposition temperature, and kinetic and thermodynamic parameters of the composites increased firstly and decreased afterwards. The DPD had a catalytic effect on the thermal decomposition of RDX, but this effect was not in linear correlation with the modification amount. The DPD-modification amount of 1/7 had the optimal catalytic effect. For DPD modification of less than 1/7, the thermal decomposition of RDX was accelerated by DPD. As the modification amount exceeded 1/7, the excessive DPD modification conversely hindered the decomposition of RDX. The thermal decomposition kinetics demonstrated that the thermal decomposition of the DMRs conformed to a multi-step reaction mechanism involving a catalytic reaction and a secondary reaction, while they had the same rate-determining step, which is the scission of the N-NO₂ bonds of RDX. The DPD modification changes the reaction pathway and reaction rate to affect the decomposition mechanism and kinetics.