Microstructure and interaction in aluminum hydrides@polydopamine composites and interfacial improvement with GAP adhesive

The reduction of interfacial interaction and the deterioration of processing properties of aluminum hydrides (AlH₃) is the main challenges preventing its practical application. Here, a simple and effective core-shell structure aluminum hydrides@polydopamine (AlH₃@PDA) complex was constructed through in-situ polymerization. The evolution of element states on the surface of AlH₃ conducted by X-ray photoelectron spectroscopy indicated the successful introduction of PDA to form the core@shell structure, the thickness of the PDA coated layer increased with the increasing PDA dosage from 0.1 to 1.6% in mass fraction, and the maximum of thickness is 50 nm in TEM testing. Py GC/MS results proved that the increase of dopamine concentration leads to higher proportions of self-assemble units, whereas lower dopamine concentrations favor higher levels of chemical bonded components. Regarding whether PDA is a covalent polymer or a noncovalent aggregate of some species, the formation of intermediates, such as dopaminechrome and 5,6-dihydroxyindole played an important role to coordination interaction with AlH₃ in FTIR, Raman, and UV-Vis spectra testing. Compared with pure AlH₃, the formation of organic PDA coating improved AlH₃ heat resistance. The adhesion work with GAP adhesive was also improved from 107.02 J/m² of pure AlH₃ to 111.13 mJ/m² of AlH₃@PDA-5 complex. This paper provides well support for further practical application of AlH₃ in solid propellants.