Direct ink writing of nAl/pCuO/HPMC with outstanding combustion performance and ignition performance

Abstract

Direct ink writing promotes ink formulation design gradually become a hotspot in the application research of nanothermite. In order to obtain an energetic ink with a certain mechanical strength and formability, it is necessary to compound the energetic material with an inert binder. The inert component will not only reduce the sensitivity and energy release efficiency of energetic systems, but also affect its application in micro ignition devices. Based on the thermal gelation behavior of hydroxypropyl methylcellulose (HPMC), the nAl/pCuO/HPMC ink was prepared by HPMC, nano aluminum powder (nAl), and sheet-like porous CuO (pCuO). It has found out that the energetic ink has a favorable printing accuracy when the HPMC content is 7 wt%. To compare the influence from the size and morphology of copper oxide and aluminum on ink printing and reaction performances, the mAl/pCuO/HPMC, nAl/nCuO/HPMC and nAl/mCuO/HPMC inks have been prepared using the same way. Due to the large particle size of the components, nAl/mCuO/HPMC cannot be printed continuously during the printing process. For the mAl/pCuO/HPMC, it cannot form self-sustaining combustion on the glass substrate when the ink is a single layer. The activation energy results show that nAl/pCuO/HPMC has the smallest value (68.39 kJ/mol). The calculated burning rate of nAl/pCuO/HPMC (32.56 cm/s) is about 6 times than that of nAl/nCuO/HPMC system (5.28 cm/s). The ignition performance test shows that only the nAl/pCuO/HPMC system can be successfully ignited by a SCB micro igniter when the HPMC content is 7 wt%. Meanwhile, the pressure test indicates that the nAl/pCuO/HPMC system (7 wt% HPMC, Ф=1.4) has the shortest pressure rising time (46.7 μs), but the largest pressurization rate (1661.7 GPa/s).