Microstructure tailoring of the nickel–yttria stabilised zirconia (Ni–YSZ) cermet hollow fibres

Abstract

Nickel–yttria stabilised zirconia (Ni–YSZ) hollow fibres have been prepared by the phase inversion/sintering technique followed by a reduction process with hydrogen. This work is particularly focussed on tailoring the microstructure and the properties of hollow fibres by ethanol addition into the spinning hollow fibre suspension. Microstructure evolution change is demonstrated by increasing the amount of ethanol from 0 to 35wt% e.g. the hollow fibre cross-section is modified from a sponge-like structure sandwiched by two thin finger-like layers to the sponge-like structure only. Higher ethanol content translates to denser hollow fibres. This trend also correlates with the shrinkage, mechanical strength and electrical conductivity of the hollow fibres. As the ethanol content is increased, shrinkage reduces, mechanical strength improves and electrical conductivity increases. The Ni–YSZ hollow fibres made from suspensions containing 15–25wt% ethanol are considered the best option as anode supports for micro-tubular solid oxide fuel cells in terms of their median porosity values, since insufficient porosity would hinder the fuel and product transport, whereas excessive porosity would deteriorate the mechanical strength of the fibres.