Surface area, crystal morphology and characterization of transition alumina powders from a new gibbsite precursor

Abstract

A new procedure was used to prepare a microcrystalline powder constituted by thin euhedral hexagonal gibbsite plates, 0.2 to 0.6 µm in diameter and 32 nm thick. The powder, fired between 200 and 1000 °C, produced chi and kappa transition aluminas. Alpha-alumina is formed from 1000 °C and recrystallized up to 1500 °C. At 1000 °C, kappa-and alpha-alumina coexisted, but kappa-alumina could only be characterized by SAED. The details of the internal organization of the transition alumina pseudomorphs were clearly observable in TEM due to the great thinness of the I-gibbsite plates. The specific surface area varied from pristine I-gibbsite (24.9 m ) at 1500 °C. The maximum value of specific surface area is 347 m 2 .g -1 in chi-alumina powder at 300 °C, a difference from Bayer gibbsite, in which the chi-alumina highest surface area is 370 m 2 .g -1 at 400 °C.

Synthesis of high-surface-area γ-Al2O3 from aluminum scrap and its use for the adsorption of metals: Pb(II), Cd(II) and Zn(II)

“…Li et al [32] revealed that the crystal growth of bayerite and gibbsite follows different pathways and, as can be seen in the results of the present report, the crystal growth of the bayerite and gibbsite were strongly influenced by the precipitation pH. Next, the XRD pattern of the aluminum oxide obtained by thermal treatment of Gel 8-80 at 500 • C is attributed to the formation of poorly crystalline chi-alumina, and is very similar to that found by Meephoka et al [33], Mekasuwandumrong et al [34], Vieira-Coelho et al [35] and Tsuchida and Ichikawa [36], with characteristic broad peaks located at 37 • , 40 • , 46 • , 60 • and 67 • . As in the present report, the chi-alumina was obtained by the cited authors from pure gibbsite.…”

Alumina: discriminative analysis using 3D correlation of solid-state NMR parameters

“…Also high resolution TEM analysis supports a hexagonal arrangement. 100 However, all authors agree the oxygen sublattice is best described as a dense packing of oxygen planes with either a fully random stacking sequence one that is ordered only locally. Therein, tetrahedral and octahedral Al sites are both considered to be disordered, and typically in a ratio of roughly 0.3.…”

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

“…It is characterized with good thermal and chemical stability [ 9 ]. Its texture is defined with a high specific surface area (135–190 m 2 /g) [ 10 , 11 ], appropriate pore size distribution, pore size and surface acidity (derived from the local microstructure, phase composition, chemical composition). Moreover, the presence of acid/base centers may offer an additional source of active centers for catalysts [ 12 ].…”