Towards Macroporous ?-Al2O3-Routes, Possibilities and Limitations.

ABSTRACT: This article combines a systematic literature review on the fabrication of macroporous ?-Al2O3 with increased specific surface area with recent results from our group. Publications claiming the fabrication of ?-Al2O3 with high specific surface areas (HSSA) are comprehensively assessed and critically reviewed. An account of all major routes towards HSSA ?-Al2O3 is given, including hydrothermal methods, pore protection approaches, dopants, anodically oxidized alumina membranes, and sol-gel syntheses. Furthermore, limitations of these routes are disclosed, as thermodynamic calculations suggest that ?-Al2O3 may be the more stable alumina modification for ABET > 175 m2/g. In fact, the highest specific surface area unobjectionably reported to date for ?-Al2O3 amounts to 16-24 m2/g and was attained via a sol-gel process. In a second part, we report on some of our own results, including a novel sol-gel synthesis, designated as mutual cross-hydrolysis. Besides, the Mn-assisted ?-transition appears to be a promising approach for some alumina materials, whereas pore protection by carbon filling kinetically inhibits the formation of ?-Al2O3 seeds. These experimental results are substantiated by attempts to theoretically calculate and predict the specific surface areas of both porous materials and nanopowders.

SUBMITTER: Carstens S 

PROVIDER: S-EPMC7179033 | biostudies-literature | 2020 Apr

REPOSITORIES: biostudies-literature