Characterization and Analysis on the Thermal Transformation of Boehmite Synthesized by Yoldas Method

Abstract

The boehmite (AlOOH) sol derived from aluminium isopropoxide was synthesized by Yoldas method. The physicochemical process and phase transition of AlOOH were investigated by TG-DSC, N2 adsorption-desorption, XRD and TEM. The results showed that upon heating, AlOOH lost the physicsorbed water first, and then lost the chemisorbed water at 242 °C, and the dehydroxylation occurred at 361 °C. The BET surface area, total pore volume and pore diameter increased, since the waters were lost. The orthorhombic AlOOH transformed to the cubic γ-Al2O3 at 361 °C, the cubic η-Al2O3 appeared after 484 °C, the monoclinic θ-Al2O3 and rhombohedral α-Al2O3 appeared after 1026 °C, and it totally turned into α-Al2O3 at 1237 °C.

Chemical and Structural Characterization of Amorphous and Crystalline Alumina Obtained by Alternative Sol–Gel Preparation Routes

“…The first endothermic peak refers to solvent evaporation, with two accompanying weight losses. High exothermic effect at 305 °C corresponds to the combustion of organics [ 45 ]. DTG curve shows a multi-stage weight loss associated with this effect, presented by two weight losses.…”

Improved hydration resistance of CaO granules via sol‐processed metal oxide protective layers

“…Nanoparticles were introduced into the surface of CaCO 3 granules by spraying the nano sol (Figure 10A). With the increase in temperature, nano boehmite (AlOOH) particles in alumina sol began dehydration and converted to high activity nano Al 2 O 3 26,27 and the CaCO 3 pseudomorphs with microsized pores were formed (Figure 10B) when alumina sol was used. The reaction mechanism involving calcium carbonate and boehmite was suggested according to the equation ():…”