Introduction

The fabrication of ceramic interconnects for solid oxide fuel cells (SOFC) and separator plates for electrochemical separation devices has been a perennial challenge facing developers. Electrochemical vapor deposition (EVD), plasma spraying, pressing, tape casting and tape calendering are processes that are typically utilized to fabricate separator plates or interconnects for the various SOFC designs and electrochemical separation devices (1,2). For sake of brevity and the selection of a planar fuel cell or gas separation device design, pressing will be the only fabrication technique discussed here. This paper reports on the effect of the characteristics of two doped lanthanum manganite powders used in the initial studies as a planar porous separator for a fuel cell cathode and as a dense interconnect for an oxygen generator.

The selection of a suitable fabrication process is highly dependent upon the device design. The raw material properties, such as surface area, particle and agglomerate size distribution, morphology, and minute secondary phases, affect the processing parameters. The influence of the initial powder characteristics on consolidation of ceramics has been well studied (3-5). Armstrong reported on the characteristics of zirconia powders from two synthesis techniques and the effect of those characteristics on consolidation and densification (3). Combustion synthesis yielded hard agglomerates which required ball milling to break down the agglomerate structure to achieve greater than 94% theoretical density. Hydrothermal synthesis provided weakly agglomerated powders in which consolidation and complete densification was dependent upon the pH of the starting suspension and the technique utilized to remove the powder from the suspension. Effects of the raw material properties on fabrication of interconnects was demonstrated by Milliken et al who showed that the sintered density of uniaxially compacted strontium doped LaCr03 increased with increasing green density (6). The increase in green density was obtained by optimizing isostatic pressure, binder, lubricant, sintering aids, and the reduction of hard agglomerates through ball milling of the starting powder prior to pressing.

0 0

Post a comment