Study on the stability of aluminum-lithium alloys and their interaction mechanisms with propellant components

Aluminum-lithium (Al-Li) alloys are promising candidates for solid propellant applications due to their high specific energy and favorable combustion characteristics. However, the high chemical reactivity introduced by Li raises concerns regarding its stability and compatibility with propellant ingredients. This study evaluates the stability of Al-10Li particles containing 10 wt.% Li and their compatibility with representative propellant components. Results indicate that exposure to ambient air promoted the formation of hydroxyl, carbonate, Al–O, and Li–O species on the particle surfaces. These changes were accompanied by surface cracking and attenuation of the AlLi phase. After aging in ambient air, the rate of decrease in heat of combustion and the rate of increase in particle mass both rose with increasing relative humidity (RH). X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared (FTIR) measurements imply that H₂O and CO₂ play important roles in the structural damage after aging in ambient air. Compatibility tests of Al-10Li with key components in solid propellant at 60 °C show that Al-10Li particles are unreactive with hydroxyl‑terminated polybutadiene (HTPB). But it shows mild reactivity with toluene diisocyanate (TDI) and obvious reactivity with dioctyl sebacate (DOS). In contrast, mixing Al-10Li particles with ammonium perchlorate (AP) at room temperature produces a much stronger reactivity, including severe agglomeration and the release of alkaline gaseous products.