Multi-stage combustion characteristics of sodium perchlorate/lithium perchlorate-based electrically controlled solid propellant

Much attention has been directed toward the development of electrically controlled solid propellant (ECSP) as it can implement switched on-off as well as regulation of burning rate. In this work, sodium/lithium battery-inspired sodium perchlorate (SP)/lithium perchlorate (LP)-based ECSPs were prepared and characterized. Herein, an ignition-combustion-extinguishment cycle is referred to a stage. The properties of electro-conductibility and multi-stage combustion for ECSPs were investigated, utilizing electrochemical impedance spectroscopy (EIS) and electrically controlled combustion test system. Results demonstrated that the component compatibility and conductivity of ECSP were optimal as mSP:mLP = 1:1, excellently eliminating the crystallization problem of the propellant. The ignition/extinguishment delay time of the second stage was always significantly lower than that of the first stage, whereas the adjustable capability of the burning rate of the second stage was slightly better than that of the first stage (100 V similar to 200 V). Meanwhile, it was found that there was a positive correlation of the burning rate vs the electrical conductivity in the combustion stable stage. In Addition, the concentration gradient of anions/cations and the composition of surface compounds of different layers were analyzed by energy dispersive spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS) and discharge test of ECSP-supercapacitor. Accordingly, the multi-stage electrothermal combustion mechanism model was established, revealing that ion transfer, electron exchange, ohmic heating and PVA gel flame-retardation are the four major factors affecting the controllable combustion of ECSP.