Towards Macroporous α-Al 2 O 3 -Routes, Possibilities and Limitations

• Published in: Materials 2020-04, Vol.13 (7)
• Main Authors: Carstens, Simon, Meyer, Ralf, Enke, Dirk
• Format: Article
• Language: English
• ISSN: 1996-1944; 1996-1944

This article combines a systematic literature review on the fabrication of macroporous α-Al O with increased specific surface area with recent results from our group. Publications claiming the fabrication of α-Al O with high specific surface areas (HSSA) are comprehensively assessed and critically reviewed. An account of all major routes towards HSSA α-Al O 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 γ-Al O may be the more stable alumina modification for > 175 m /g. In fact, the highest specific surface area unobjectionably reported to date for α-Al O amounts to 16-24 m /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 . Besides, the Mn-assisted α-transition appears to be a promising approach for some alumina materials, whereas pore protection by carbon filling kinetically inhibits the formation of α-Al O seeds. These experimental results are substantiated by attempts to theoretically calculate and predict the specific surface areas of both porous materials and nanopowders.