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arXiv · 0708.3771

Atomic structure analysis of nanocrystalline Boehmite AlO(OH)

Stefan Bruehne·Saskia Gottlieb·Wolf Assmus·Edith Alig·Martin U. Schmidt
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Abstract

Nanocrystalline n-AlO(OH) (Disperal P2(R) of Sasol) was investigated by means of the atomic pair distribution function (PDF). The PDF is derived from powder diffraction data, an ideally resolved PDF is obtained from a synchrotron source which provides a large maximal scattering vector length Qmax > 300 nm-1. Here, however, we were able to reveal atomic structure details of the about 4 nm particles from in-house diffraction data (Qmax = 130 nm-1): PDF least squares model refinements show that n-AlO(OH) is of the layered Boehmite structure type (oC16, Cmcm). But the structure is uniformly distorted in domains of ca. 2 nm size within the nano particles. The hydrogen bonds between the layers are widened up significantly by +13 pm, accounting for the higher reactivity when compared to microcrystalline Boehmite. Our results from only one "nanocrystallographic" experiment are consistent with a trend which was found via the Rietveld technique on a series of AlO(OH) of different crystallite size (Bokhimi et al., 2001). In addition, the PDF contains information on structural distortion as a function of (coherence) domain size within the nano particles.

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Stefan Bruehne, Saskia Gottlieb, Wolf Assmus, Edith Alig, Martin U. Schmidt. 2007-08-28. Atomic structure analysis of nanocrystalline Boehmite AlO(OH). https://arxiv.org/abs/0708.3771

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