Metal-ceramic/ceramic nanostructured layered composites for solid oxide fuel cells by spark plasma sintering.

In this work, bi-layered Fe-Ni-Co-YSZ/YSZ nanostructured composites for solid oxide fuel cells were obtained using the spark plasma sintering (SPS) technique. The microstructures of the anode and electrolyte were controlled by optimization of SPS consolidation parameters. The resulting bilayers have a full dense YSZ electrolyte and porous Fe-Ni-Co/YSZ anode as well as crack-free and well-bonded anode/electrolyte interface. On the other hand, SPS under non-optimized processing parameters cannot yield the desired results. The high resistance to thermal stresses of the fabricated half-cells was achieved with Fe-Ni-Co/YSZ anode. The developed anode showed higher thermal compatibility with YSZ electrolyte than usual Ni/YSZ cermet. Thus, with the successful combination of SPS parameters and anode material, we have obtained bi-layers for SOFCs with required microstructure and thermal compatibility.

Spark plasma sintered Ni-YSZ/YSZ bi-layers for solid oxide fuel cell.

Ni-YSZ/YSZ bi-layers for SOFCs were fabricated by spark plasma sintering (SPS). Optimization of SPS parameters of YSZ and NiO/YSZ powders was performed in order to fabricate anode and electrolyte with desired microstructures. The effect of sintering conditions on microstructure and electrical properties of YSZ was studied. The influence of processing parameters and amount of pore-forming agent on the microstructures of Ni/YSZ cermets was also investigated. It was shown that the amount of pore-former and in situ reduction of nickel oxide had a substantial effect on microstructure of the cermets. The in situ reduced anode demonstrates sufficiently homogeneous distribution of Ni and YSZ making a conduction path for electrons and ions. Ni-YSZ/YSZ bi-layers with crack-free and well-bonded anode/electrolyte interface were obtained. Furthermore, warping was not observed for the produced bi-layers.

Tough yttria-stabilized zirconia ceramic by low-temperature spark plasma sintering of long-term stored nanopowders.

Weakly agglomerated 1.75 and 3 mol% yttria stabilized zirconia nanopowders were used in this study after six years of storage in vacuum-processed plastic containers. The proper storage conditions of the Y-TZP nanopowders avoided the hard agglomeration. Untreated and bead-milled nanopowders were used to obtain dense ceramics by slip casting and subsequent low-temperature sintering. Fully dense nanostructured 1.75Y-TZP and 3Y-YZP ceramics with and without doping of 1 wt% Al2O3 were produced by an optimized spark plasma sintering (SPS) technique at the temperatures of 1050-1150 degrees C at a pressure of 100 MPa. The SPS has revealed the clear advantage of consolidation of the weakly agglomerated nanopowders without preliminary deagglomeration. The Vickers hardness of both the low-temperature and spark plasma sintered samples was found to lie in the range of 10.98-13.71 GPa. A maximum fracture toughness of 15.7 MPa m(1/2) (average 14.23 MPa m(1/2)) was achieved by SPS of the 1.75Y-TZP ceramic doped with 1 wt% Al2O3 whereas the toughness of the 3Y-TZP ceramics with and without alumina doping was found to vary between 3.55 and 5.5 MPa m(1/2).