Edinburgh Napier University

  Solid oxide fuel cells are an important strand of future energy provision, offering high efficiency, compactness and little or no pollution. However, their necessary high operating temperatures place severe demands on component materials resulting in relatively difficult and expensive materials and processes.

This thesis investigates novel materials and processes used in the manufacture of anodes for solid oxide fuel cells. To that end, combinations of yttria-stabilised zirconia (YSZ), titanium diboride, nickel, nickel-chromium and cobalt have been processed and characterised for microstructural and electrical properties. In addition, electroless deposition of nickel, cobalt and nickel/cobalt onto yttria-stabilised zirconia has been investigated with optimum processing conditions being established. In particular, the importance of yttria-stabilised zirconia particle size combined with the sintering temperature of the electrolessly-deposited cermet has been established.

A nominal YSZ particle size of 0.5 to 1 microns was found to give excellent results in terms of improved integrity for given pressing pressures and sintering conditions. The best results in terms of electrical conductivity were achieved using these smaller-sized particles after being given an electrolessly deposited duplex coating of nickel followed by cobalt. For these conditions, a sinter temperature of 1000ºC produced the best distribution of anode metallic content – the 1200ºC sinter resulted in metallic agglomerations probably caused by localised melting. These microstructural observations – achieved by scanning electron microscope mappings – agreed with the electrical conductivity results.

The work has demonstrated the potential of a cost-effective process for the manufacture of anodes for use in solid oxide fuel cells and will act as the basis for further work in this area.