P 56 Phase Transformations in gamma-Al(OH)3 under Heat Treatment in Air and Water Vapor / V. I. Lopushan, G. F Kuznetsov, R. N. Pletnev, D. G. Kleshchev // Bulletin of the Russian Academy of Sciences: Physics. - 2007. - Vol. 71, № 8. - P. 1187-1189 : il. - Bibliogr. : p. 1189 (9 ref.) Рубрики: ХИМИЧЕСКИЕ НАУКИ Кл.слова (ненормированные): ФАЗОВЫЕ ПЕРЕХОДЫ -- ТЕРМООБРАБОТКА -- АЛЮМИНИЙ Аннотация: The kinetics and mechanism of phase transitions (PTs) in gibbsite (γ-Al(OH)3) under heat treatment in air and water vapor (170–550°C) have been investigated by iso- and nonisothermal thermogravimetry, X-ray phase analysis, transmission electron microscopy, 27Al nuclear magnetic resonance, and chemical analysis. It is shown that (i) the gibbsite PT in air involves two interrelated transformations occurring simultaneously:(1) gibbsite -> boehmite (γ-AlOOH) and (2) gibbsite -> X-ray-amorphous alumina (Al2O3); both areimplemented through the topochemical mechanism; and (ii) in water vapor only transformation of gibbsite into boehmite occurs (PT-3), which is implemented through the dissolution–precipitation mechanism. The apparent activation energies of the PTs under consideration have been determined \\\\Expert2\\nbo\\Bulletin of the Russian Academy of Sciences Physics\\2007, V. 71, N 8, P. 1187-1189.pdf |