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Collisions of an atomic beam of He atoms with the surface of an aligned nematic liquid crystal film (4′-pentyl-4-cyano biphenyl, 5CB) initiate a transient change in the aligmnent of the surface region of the film. The effect is greater when the He atoms approach perpendicular to the alignment director of the sample than when the approach is parallel to the director. The relaxation of the system back to its initial alignment has a temperature dependence which suggests that rotational diffusion is the relaxation mechanism. Laser induced fluorescence spectra of I[SUB2] molecules scattered from the isotropic phase and from the nematic phase of 5CB indicate that molecules scattered from aligned 5CB are more internally excited than those scattered from an isotropic 5CB sample. In total, these results indicate that the dynamics of collisions at the gas-liquid crystal interface are strongly dependent upon the molecular order in the liquid crystal. [ABSTRACT FROM AUTHOR]

Yttrium doped boehmite nanofibres with varying yttrium content have been prepared at low temperatures using a hydrothermal treatment in the presence of poly(ethylene oxide) surfactant (PEO). The resultant nanofibres were characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). TEM images showed the resulting nanostructures are predominantly nanofibres when Y-doping is less than 5%; in contrast Y-rich phases were formed when doping was around 10%. The doped boehmite and the subsequent nanofibres/nanotubes were analyzed by thermogravimetric and controlled rate thermal analysis methods. The boehmite nanofibres produced in this research thermally transform at higher temperatures than boehmite crystals and boehmite platelets. Boehmite nanofibres decompose at higher temperatures than non-hydrothermally treated boehmite. [ABSTRACT FROM AUTHOR]