Synthesis and characterization of pseudoboehmite by neutralization method

Abstract Pseudoboehmite was obtained through neutralization of ammonium aluminum sulfate solution [NH4Al(SO4)2·12H2O] with ammonia water [NH3 (aq)]. The neutralization process resulted in flake-like overlapping flower-like structures at 80 °C and 85 °C. When the temperature of the NH4Al(SO4)2·12H2O solution was raised to 90 °C, nanoparticles, microspheres with a diameter of less than 50 nm, were obtained. The (131) plane was studied by HRTEM imaging (high resolution transmission electron microscopy). Density functional theory was used to study the interface properties of the pseudoboehmite, and the surface energy and attachment energy were calculated for the optimized crystal planes of interest. The results show that the relaxed (131) plane has the lowest surface energy (0.0474 J/m2), and thus is the most stable surface. Additionally, the (200) plane of the pseudoboehmite has the lowest absolute value of attachment energy (0.2106 eV/unit), consistent with having the strongest X-ray diffraction peak and indicating that it is the preferred orientation. The formation mechanism of flower-like and microspherical particles is discussed, with consideration for solution temperature effects on morphology and the predicted equilibrium morphology and growth morphology of pseudoboehmite.