Angela Gondolini

Stainless steel porous substrates produced by tape casting

In this work the technological issues related to the production of tape cast large-area porous stainless steel supports for Solid Oxide Fuel Cells (SOFC) applications were carefully investigated. The slurry formulation was optimized in terms of amount and nature of the organic components needed: rice starch and polymethyl metacrylate were found to be, respectively, the most suitable pore former and binder because easily eliminated during the thermal treatment in reducing atmosphere. The compatibility of the binder system chosen with the most widely used solvents for screen printing inks was also evaluated. Finally the influence of the sintering temperature and of the refractory supports to be used during the thermal treatments onto the production of porous stainless steel supports was discussed. The whole process optimization allows to produce flat, crack-free metallic substrate 900-1000 μm thick, dimensions up to 5×5 cm and with a tailored porosity of 40% suitable for SOFCs application.

All-ceramic asymmetric membranes with superior hydrogen permeation

BaCe0.65Zr0.20Y0.15O3−δ–Gd0.2Ce0.8O2−δ (BCZY–GDC) composite with a planar asymmetrical architecture was investigated for the first time as a hydrogen separation membrane in the 600 °C to 750 °C temperature range. Asymmetrical membranes comprising a 20 μm thick dense BCZY–GDC layer supported on a 600 μm thick porous substrate with the same composition were successfully produced through a tape casting process. The influence of the dense layer composition on hydrogen separation and the catalytic activation of the dense membrane layer and porous support were thoroughly studied. The hydrogen permeation process was further characterized by varying the environment humidification degree and temperature and by shifting the sweep and feed gas compositions. This work highlights the importance of preserving the dual proton (BCZY) and electron (GDC) conductor phases during the sintering step of the membrane to enhance H2 permeation; a value of 0.47 mL min−1 cm−2 at 750 °C was obtained, which is currently one of the highest H2 fluxes obtained for all-ceramic proton-conducting membranes. In addition, a strong improvement is achieved when the feed/sweep sides of the membrane are reversed, i.e. H2 feeding in the support side leads to a flux increase up to 0.68 mL min−1 cm−2 at 750 °C when only the sweep side is hydrated. These results demonstrate that these asymmetric dual phase BCZY–GDC membranes are the most promising candidates for H2 separation applications at high temperatures.