Hierarchically Structured Aluminium Oxide as a Functional Additive to Fire-fighting Powder Compositions: Synthesis and Properties

Hierarchically structured aluminium oxide was hydrothermally synthesized with carbamide as a precipitator. Raman spectroscopy, SEM spectroscopy, and X-ray phase analysis were used to investigate morphology and parameters of porously structured aluminium oxide as influenced upon by concentration of reactive solution, excessive portions of precipitator, and the counterion type. Differing mechanisms to form hierarchical structures with variable phase content of the hydrothermally synthesized product were evinced. The conditions under which spherulite-type aluminium oxide was formed were ascertained. Stable super-hydrophobic state of the surface of aluminium oxide spherulites was demonstrated as their characteristic feature obtained after hydrophobization with chlorosilanes. This feature pre-determines prospects of aluminium oxide spherulites as a functional additive for fire-fighting powder compositions to provide their stability against moisture and rheological properties improved.