Søren Preben Vagn Foghmoes

Oxygen Permeation in Thin, Dense Ce0.9Gd0.1O1.95-δ Membranes II. Experimental Determination

Thin (~30 μm), dense Ce 0.9 Gd 0.1 O 1.95-δ (CGO10) membranes (5 × 5 cm 2 ) supported on a porous NiO/YSZ substrate were fabricated by tape casting, wet powder spraying and lamination. A La 0.58 Sr 0.4 Co 0.2 Fe 0.8 O 3-δ /Ce 0.9 Gd 0.1 O 1 . 95-δ (LSCF/CGO10) composite cathode was applied by screen printing. Oxygen permeation measurements and electrochemical characterisation of the cells were performed as a function of temperature with air and varying hydrogen/steam mixtures flowing in the feed and permeate compartments, respectively. The oxygen flux was found to reach 10 N mL min -1 cm -2 at ~1100 K and to exceed 16 N mL min -1 cm -2 at 1175 K. The measured oxygen flux was in good agreement with theoretical predictions from a model that takes into account the bulk transport properties of Ce 0.8 Gd 0.1 O 1.95-δ , the anode and cathode polarisation resistances, and the gas conversion and gas diffusion losses in the permeate compartment. The performance of the membrane was also investigated under varying CH 4 and H 2 O gas mixtures at 1106 K. The oxygen flux increased with decreasing steam to carbon ratio and was found to exceed 10 N mL min -1 cm -2 of O 2 for steam to carbon ratios below 4:3. Post-test analysis of the tested membrane did not reveal any significant microstructural degradation of the CGO10 membrane or the anode-support.

In situ characterization of delamination and crack growth of a CGO-LSM multi-layer ceramic sample investigated by X-ray tomographic microscopy

The densification, delamination and crack growth behavior in a Ce0:9Gd0:1O1:95 (CGO) and (La0:85Sr0:15)0:9MnO3 (LSM) multi-layer ceramic sample was studied using in situ X-ray tomographic microscopy (microtomography), to investigate the critical dynamics of crack propagation and delamination in a multilayered sample. Naturally occurring defects, caused by the sample preparation process, are shown not to be critical in sample degradation. Instead defects are nucleated during the debinding step. Crack growth is significantly faster along the material layers than perpendicular to them, and crack growth and delamination only accelerates when sintering occurs.