Key words: sub- and supercritical water, aluminum, oxidation, nanoparticles
Oxidation of bulk aluminum samples by sub- and supercritical water leads to the formation of (AlOOH)n and (Al2O3)n nanoparticles. At uniform heating of reactants to 700 K, H2 evolution starts at 523 K. If supercritical water (665 K, 23.1 MPa) is injected into reactor containing aluminum sample, the time delay of oxidation is 140 s. The transmission electron microscopy study of oxidized aluminum samples shows that oxidation by supercritical water leads to the preferential formation of large (300÷400 nm) particles of α-Al2O3. Small (20÷50 nm) particles of γ-Al2O3 with insignificant contents of AlOOH together with large particles of α-Al2O3 are found when in aluminum is oxidized by water vapor in a programmed heating regime. The kinetic equations describing the rate of H2 production during the reaction of water with aluminum are derived and mechanisms of nanostructuring are discussed.
doi:10.1134/S199079311007002X