Abstract: A method of manufacturing closed end ceramic fuel cell tubes with improved properties and higher manufacturing yield is disclosed. The method involves bonding an unfired cap to a hollow unfired tube to form a compound joint. The assembly is then fired to net shape without subsequent machining. The resultant closed end tube is superior in that it provides a leak-tight seal and its porosity is substantially identical to that of the tube wall. The higher manufacturing yield associated with the present method decreases overall fuel cell cost significantly.

Abstract: A method and an apparatus for making straight fuel cell tubes are disclosed. Extruded tubes comprising powders of fuel cell material and a solvent are dried by rotating the extruded tubes. The rotation process provides uniform circumferential drying which results in uniform linear shrinkage of the tubes. The resultant dried tubes are very straight, thereby eliminating subsequent straightening steps required with conventional processes. The method is particularly useful for forming inner air electrode tubes of solid oxide fuel cells.

Abstract: An electrochemical cell is made having a porous fuel electrode (16) and a porous air electrode (13), with solid oxide electrolyte (15) therebetween, where the air electrode surface opposing the electrolyte has a separate, attached, dense, continuous layer (14) of a material containing cerium oxide, and where electrolyte (16) contacts the continuous oxide layer (14), without contacting the air electrode (13).

Abstract: A method of manufacturing porous ceramic tubes for fuel cells with improved properties and higher manufacturing yield is disclosed. The method involves extruding a closed end fuel cell tube, such as an air electrode of a solid oxide fuel cell, in which the closed end also functions as the sintering support. The resultant fuel cell tube has a superior porosity distribution which allows improved diffusion of oxygen at the closed end of the tube during operation of the fuel cell. Because this region has the highest current density, performance enhancement and improved reliability of the fuel cell tube result. Furthermore, the higher manufacturing yield associated with the present method decreases the overall fuel cell cost.

Abstract: A transparent yttrium oxide ceramic is made by densifying a yttrium oxide power without addition of dopants. The yttrium oxide powder is consolidated into a body of a predetermined shape and sintered to a density such that any remaining porosity is sealed from the surrounding atmosphere. The closed porosity body is then subjected to an elevated pressure and temperature to provide the body with substantially 100% of theoretical density while the body is disposed adjacent an oxygen supplying media. The oxygen supplying media is a ceramic media used to provide an oxygen partial pressure during the densification step ast the elevated pressure and temperature. After this step, a clear transparent body is provided without the need for any further high temperature processing such as a post densification anneal to restore oxygen stoichiometry to the body. The resulting body has substantial transparency over the wavelength range of 0.6 .mu.m to 7 .mu.m.