Phase transitions of ϵ-HNIW in compound systems

The heat-induced phase transitions of ϵ-HNIW, both neat and coated with various additives used in plastic bonded explosives, were investigated using powder X-ray diffraction and differential scanning calorimetry. It was found that ϵ-HNIW, after being held at 70°C for 60h, remained in the ϵ-phase. Applying other conditions, various phase transition parameters were determined, including T_c (the critical phase transition temperature), T₅₀ (the temperature at which 50% of the phase transition is complete) and T₁₈₀ (the percentage of γ-HNIW present in samples heated to 180°C). According to the above three parameters, additives were divided into three categories: those that delay phase transition, those that raise the critical temperature and the transition rate, and those that promote the phase transition. Based on the above data, a phase transition mechanism is proposed.