Simple Preparation of AP@CuDHT Core–Shell Structure: A “One Stone, Three Birds” Method for Comprehensively Improving the Energy, Thermal Properties, and Hygroscopicity of AP

Comprehensive improvement in the thermal properties, energy characteristics, and hygroscopicity of ammonium perchlorate (AP) carries substantial significance to its utilization in solid propellants. In the present study, a novel coating agent, CuDHT, was synthesized via the self-assembly of 3,6-dihydrazino-1,2,4,5-tetrazine (DHT) and transition metal ions (Cu²⁺), which can comprehensively enhance the performance of AP. The morphology, composition, and thermal properties of samples prepared in this work were examined via scanning electron microscopy, Fourier transform infrared spectroscopy, powder X-ray diffraction, differential scanning calorimetry, and thermogravimetric analysis techniques. Meanwhile, the burning rate and combustion temperature of AP@CuDHT-based solid propellants were tested via infrared thermography. The findings show that AP particles have their surfaces coated with a homogeneous and compact CuDHT coating layer. Moreover, the CuDHT coating layer is capable of markedly catalyzing AP's thermal decomposition and reducing its hygroscopicity. As the CuDHT coating content increases, the peak temperature of AP@CuDHT's high-temperature decomposition and moisture absorption rate gradually decrease. When the CuDHT content reaches 10 wt %, the HTD peak temperature of AP@CuDHT moves forward by 69.5 °C relative to pure AP, and the moisture absorption rate is cut by 0.326 wt %. Compared with pure AP, AP@CuDHT (10%)'s impact and friction sensitivities are higher by 4% and 8%. Additionally, CuDHT can remarkably enhance the combustion performance of solid propellants. With an increase in CuDHT content, the burning rate of AP@CuDHT-based propellants and their combustion temperature gradually increase. At 10 wt % CuDHT, the burning rate and combustion temperature are enhanced by 6.1 mm·s^-1 and 572.6 °C, respectively, compared to those of pure AP-based propellants. In summary, this study provides references for comprehensively improving the hygroscopicity, energy, and thermal properties of AP and, meanwhile, demonstrates a significant application outlook for promoting the combustion performance in solid propellants.