Preparation and characterization of composite support NiO/La_0.7Ca_0.3CrO_3-<i>δ</i> by phase-conversion spinning method for micro-tubular SOFC

Abstract

Using solid-phase reaction process to synthesize La0.7Ca0.3CrO3-δ(LCC) primary powder, composite hollow fiber membrane of NiO/LCC (1:1) was prepared by phase-conversion spinning method and then sintered at 1400℃ in air as micro-tubular solid oxide fuel cells (SOFC) support. The particle size distribution, TG-DTA thermal analysis, structure, morphologies, electrical conductivity, thermal expansion and bending strength were characterized by laser particulate size analyzer, thermal analyzer, X-ray diffraction, scanning electron microscopy, standard DC four-probe technique, thermal expansion dilatometer and universal material testing machine. Results indicate that LCC and NiO powders have considerable chemical and sintering compatibilities at SOFC co-firing temperature (1400℃). The fracture section of the hollow fiber membrane exhibits a sandwich-like structure with homogeneous porous surfaces. Two layers of obviously bigger parallel finger-like pores distribute uniformly between the inner and outer surfaces of the microtubule section. The porosity of the sample is 60.6%, and increases to a relatively high value of 68.1% after reduction. Electrical conductivity of the sintered specimen decreases as the temperature increasing in pure H2. The value reaches 10.8S·cm-1 at 700℃. Bending strength before and after reduction are 39.6MPa and 33.2MPa respectively. Thermal expansion coefficient (TEC) value of the NiO/LCC hollow fiber membrane gets to 12.4×10-6K-1, which is very close to that of other SOFC components, such as NiO/YSZ anode and LCC interconnect.

Keywords

• micro-tubular SOFC
• hollow fiber membrane
• sintering ability
• electrical conductivity