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A method is proposed for the synthesis of nanoscale boehmite powder at low temperatures of hydrothermal treatment in 1.5 wt % HCl solution at 150 and 170°C and in water at 80, 100, and 130°C. The optimal parameters of hydrothermal treatment are found. The conversion stages of γ-Al2O3 to boehmite (AlOOH) are found; the process is solid-phase (topochemical). The physical and technological properties of boehmite nanopowder are studied. We have found that boehmite possesses similar properties despite the temperature of hydrothermal treatment. [ABSTRACT FROM AUTHOR]

We have studied the kinetics of boehmite nanopowder formation during hydrothermal treatment of γ-Al2O3 nanopowder in a 1.5% HCl solution at 200, 170, and 150°C. The results demonstrate that the temperature-dependent reaction rate constant follows the Arrhenius equation. The Ea of the process has been determined to be 84 kJ/mol. The thermodynamics of γ-Al2O3 nanopowder conversion into boehmite during hydrothermal treatment at 150°C has been studied by differential scanning calorimetry. The heat of vaporization of water from a two-phase nanosystem (γ-Al2O3 + forming boehmite) has been determined to be 8, 16, and 22 kJ/mol H2O, which points to an active role of water with a low heat of vaporization in the initial stages of the hydrothermal treatment of the γ-Al2O3 nanopowder. The heat effect of the АlООН → γ-Al2O3 conversion in the nanopowders is lower than the reference value by 7 kJ/mol AlOOH, which is attributable to the small particle size and low structural perfection of the synthesized boehmite (AlOOH). [ABSTRACT FROM AUTHOR]