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Updated: Aug 10, 2026

Facile Preparation of Ultrafine Aluminum Hydroxide Particles with or without Mesoporous MCM-41 in Ambient Environments
Published on: May 11, 2017
High fraction of penta-coordinated aluminium in amorphous and crystalline aluminium borates
S Simon1, G J van Moorsel, A P Kentgens
1Department of Molecular Spectroscopy, Faculty of Science, University of Nijmegen, Netherlands.
Abstract:
27Al and 11B magic-angle spinning nuclear magnetic resonance (MAS NMR) results are reported on aluminium borates of composition Al2(1 - x)B2xO3 (0 < or = x < or = 0.7). It is shown that starting from liquid precursors with hexa-coordinated Al and tri- and tetra-coordinated B, porous aluminium borates are obtained containing high fractions of penta-coordinated Al. The presence of boron in the crystalline phases stabilizes penta-coordinated Al, existing already in their amorphous precursors, and at the same time distorts the surroundings of the hexa-coordinated Al. The reversible effect of air exposure on low-coordinated Al (Al4C, Al5C) and B (B3C) proved that at least these species are situated at the surfaces of the pores. The A9B2 phase still contains a small fraction of tetra-coordinated B. The 27Al and 11B MAS NMR spectra of A9B2 show a well-resolved powder spectrum with no indication of broadening due to a distorted configuration.
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