Jonas Gurauskis

Alkoxide-based precursors for direct drawing of metal oxide micro- and nanofibres

Abstract The invention of electrospinning has solved the problem of producing micro- and nanoscaled metal oxide fibres in bulk quantities. However, until now no methods have been available for preparing a single nanofibre of a metal oxide. In this work, the direct drawing method was successfully applied to produce metal oxide (SnO2, TiO2, ZrO2, HfO2 and CeO2) fibres with a high aspect ratio (up to 10 000) and a diameter as small as 200 nm. The sol–gel processing includes consumption of precursors obtained from alkoxides by aqueous or non-aqueous polymerization. Shear thinning of the precursors enables pulling a material into a fibre. This rheological behaviour can be explained by sliding of particles owing to external forces. Transmission (propagation) of light along microscaled fibres and their excellent surface morphology suggest that metal oxide nanofibres can be directly drawn from sol precursors for use in integrated photonic systems.

Residual stress measurements of alumina-zirconia ceramics by time-of-flight neutron diffraction

Neutron strain scanning and Rietveld analysis were used to study the residual stresses in Al2O3/Y-TZP ceramic composites fabricated by different green processing techniques (a novel tape casting and conventional slip casting) and with different zirconia content. The results show that the residual stresses in zirconia particulates are tensile and the ones in alumina matrix are compressive, with almost flat through-thickness residual stress profiles in all bulk samples. The residual stresses for both phases were mainly dependent on the zirconia content, irrespective of the measurement direction and the fabrication process.

Residual strain scanning of alumina-based ceramic composites by neutron diffraction

Residual strain profiles were measured by neutron diffraction in alumina-aluminum titanate ceramic composites sintered at two different temperatures, namely 1450 and 1550°C. The results show that irrespective of the direction and the sintering temperature, the obtained profiles are almost flat, with very similar results for both temperatures. In addition, the results demonstrate that the alumina is in compression whereas the aluminium titanate is subjected to tensile residual stresses.