Atomic structure analysis of nanocrystalline boehmite AlO(OH)

Nanocrystalline n-AlO(OH) (Disperal P2, Sasol) Was investigated by means of the atomic pair distribution function (PDF). The PDF is derived from powder diffraction data, and an ideally resolved PDF is obtained from a synchrotron source which provides a large maximal scattering vector length Q(max) > 300 nm(-1). Here, however, we were able to reveal atomic structure details of the similar to 4 nm particles from in-house diffraction data (Q(max) = 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 similar to 2 nm within the nanoparticles. The hydrogen bonds between the layers are widened 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 that was found via the Rietveld technique on a series of AlO(OH) of different crystallite sizes (Bokhimi et al. J. Solid State Chem. 2001, 159, 32-40). In addition, the PDF contains information on structural distortion as a function of (coherence) domain size within the nanoparticles.