Effect of Graphite Pore‐Forming Agents on the Sintering Characteristics of Ni/YSZ Composites for Solid Oxide Fuel Cell Applications

Pore‐forming agents are an effective way to engineer porosity in a sintered compact. When adding graphite to tape cast nickel oxide (NiO) and yttria‐stabilized zirconia (YSZ) composites, the amount of porosity created is similar to the volume of graphite added. The sintering characteristics of NiO/YSZ composites with varying graphite loadings are similar to the sintering characteristics of the graphite‐free composites. Below a critical graphite loading of 20 vol% graphite of the pressed green volume, the volumetric sintering shrinkage increases slightly with increasing graphite loading because of the higher organic material content in the tape. Above a graphite loading of 20 vol%, swelling in the composite thickness is severe thus introducing greater linear sintering shrinkage anisotropy. The sintering anisotropy is attributed to the delamination of the tape cast layers caused by the large volume of exit gases formed during the graphite burnout.