Adrian Leo

Oxygen permeation through perovskite membranes and the improvement of oxygen flux by surface modification

Abstract BSCF hollow fiber membranes possessing an asymmetric layered structure were prepared using a modified phase inversion process followed by subsequent sintering at temperatures from 1100 to 1175 ˚C. The fibers were characterized by SEM, and tested for air separation at ambient pressure and temperatures between 650 and 950 ˚C. Although the prepared hollow fibers resulted in self-supported asymmetric substrate with a very thin densified perovskite layer for mixed conduction, O2 permeation was controlled by surface O2 exchange kinetics rather than bulk diffusion. In order to improve O2 flux, surface modification was carried out by the attachment of Pt particles on the surface of the hollow fiber. The maximum O2 flux measured for pure perovskite hollow fiber was 0.0268 mol m−2 s-1 at 950 ˚C whilst O2 fluxes increased up to 25% after the surface modification using Pt micro-particles.

Characterization and Pervaporation Study on Ethanol Separation Membranes

Inorganic membranes have many advantages for dehydration of azeotropic mixtures of ethanol and water for renewable fuel purposes. In this work, we developed an inorganic membrane from γ-alumina and tested it for its ability to selectively permeate water over ethanol. Ethanol adsorbed both chemically and physically on the surface of γ-alumina, blocking the 47 Å pores sufficiently to enhance water selectivity. Stable flux was observed over 6 h, but after 4–5 h of continuous testing, water selectivity rose above 200 due to this blocking phenomenon.

Effect of nano-Al2O3 addition on the densification of YSZ electrolytes

This work investigates the effect of nanosized Al2O3 addition on the sinterability of YSZ electrolyte. (1−x)YSZ + Al2O3 ceramics with compositions x = 0 to 0.01 were prepared by the conventional mixed oxide route from a commercial powder suspension (particle size <50 nm), and sintered at 1200 to 1500°C for 2 hours in air. Densification, phase evolution, and microstructure were characterized by SEM/EDS and XRD. An improvement in sintered density was observed for the samples with 0.2 to 0.5 mol% Al2O3, though depending on the sintering temperature. Only cubic zirconia was detected as crystalline phase, although XRD features suggested chemical interactions depending upon the amount of Al2O3. The grain size of YSZ was homogeneous and no second phase segregation was detected in the tested range of incorporated nano-Al2O3 and sintering temperatures.