Shi Li,Tao Guo,Miao Yao,Wen Ding,Jialin Chen,Jiaxing Song,Sheng Zhang,Rui Zhu
To study the effect of the addition of potassium perchlorate (KClO4) on the performance of nano thermites, Al/Bi2O3 nano thermites with different mass fraction (wt%) of KClO4 was made by ultrasonic dispersion method. Then, all samples were tested by SEM, DSC and rapid excitation ignition. DSC results showed Al/Bi2O3/10 wt%KClO4 had the highest heat release. Compared with Al/Bi2O3, the heat release increased by 28.32%. The results of activation energy calculations showed Al/Bi2O3/30 wt%KClO4 had the lowest activation energy (Ea). Its activation energy was reduced by 30%, mere about 149.17 KJ mol−1. Finally, it can be seen from the combustion situation that the addition of KClO4 reduced the intensity of burning. This work found a way to increase the heat release or reduce the activation energy of nano thermites by controlling the amount of KClO4 added.
Yang Qin,Jie Liu,Jiangbao Zeng,Jinbin Zou,Ye Song,Fengsheng Li
To improve the ignition and combustion performance of boron (B), the B@ potassium perchlorate (KP) composite micro-units are successfully prepared by recrystallization of solvent evaporation. The morphology and structural composition show that B@KP composite micro-units are formed by the gentle recrystallization of KP at the heterogeneous interface between B particles and solvents. It is shown by thermal analysis that the initial thermal decomposition temperature of KP is reduced by 49 °C due to the reduction of particle size. In addition, the heat of 420 J/g released by the thermal decomposition of KP is beneficial to the evaporation of the oxide boron (B 2 O 3 ) film on the surface of B, which reduces the initial oxidation temperature of B by 185 °C and improves the ignition performance of B. Interestingly, the oxygen (O 2 ) released by the thermal decomposition of KP quickly reacts with B to release heat of 3608 J/g, which improves the combustion performance of B. The optimal mass ratio of B to KP is 1: 5, which results in the ignition delay time of 641 ms, a reduction of 19 ms compared to the physical mixed sample. The ignition delay times of other samples are 724 ms, 680 ms and 650 ms respectively, and B could not be ignited successfully. In the combustion process, all samples emit a bright green flame of B combustion, and even a fierce combustion flame like a mushroom cloud appears. In a word, the B@KP composite micro-units have great potential for application in solid propellants.
Microwave ignition (MWI) technology enables synchronized large-area multi-point ignition, multi-pulse operation, higher combustion temperature and efficiency, and dynamic thrust modulation through microwave field adjustments compared to conventional electric ignition methods. However, MWI application is still limited by the absence of a microwave-responsive ignition agent. Herein, A series of nano-titanium/copper ferrite/potassium perchlorate ( n- Ti-CFO/KP (0∼40%)) microwave-sensitive agents were successfully synthesized via electrostatic spraying, where KP enhances combustion, while CFO acts as both catalyst and microwave sensitizer. MWI results demonstrate that n- Ti-CFO/KP (10%) exhibits the shortest ignition delay time (IDT) by 6.34 ms, owing to its high chemical reactivity and the high microwave absorption of Ti, CFO. Combustion analysis suggests that n- Ti-CFO/KP (40%) composite achieves 10-fold combustion enhancement over KP-free ignition agents by a peak pressure of 552.2 kPa and combustion rate of 221.4 m·s -1 , while n- Ti-CFO/KP exhibits the combustion flame temperature of 1250 °C compared to n- Ti-CFO by 700 °C. This remarkable improvement is attributed to the synergistic catalytic activation and combustion - supporting effects of CFO. Furthermore, n- Ti-CFO/KP (10%) exhibits comparable combustion and sensitivity performance to conventional agents ( μ- Ti/KP and B/KNO 3 ). The n- Ti-CFO/KP (10%) shows its main exothermic peak at 310 °C, significantly lower than the 550 °C peak observed for μ- Ti/KP, as well as the excellent catalytic decomposition effect of CFO on KP was further confirmed, where the low reaction temperature can shorten the microwave dielectric heating time. The synergistic effect and combustion intensification result from the coupled interaction between the microwave thermal characteristics of n- Ti-CFO and low-temperature oxygen release kinetics of KP. This coupling achieves significantly reduced MWI delay and enhanced energy release rates, thereby overcoming traditional combustion's reliance on high-temperature conditions. This result provides a new insight into the design of pyrotechnics and propulsion for fast plasma generation and microwave combustion.
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