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 (AlH) is the main challenges preventing its practical application. Here, a simple and effective core-shell structure aluminum hydrides@polydopamine (AlH@PDA) complex was constructed through in-situ polymerization. The evolution of element states on the surface of AlH 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 AlH in FTIR, Raman, and UV-Vis spectra testing. Compared with pure AlH, the formation of organic PDA coating improved AlH heat resistance. The adhesion work with GAP adhesive was also improved from 107.02 J/m of pure AlH to 111.13 mJ/m of AlH@PDA-5 complex. This paper provides well support for further practical application of AlH in solid propellants.