Influence of reduction conditions of NiO on its mechanical and electrical properties

  • Yehor Brodnikovskyi Frantsevich Institute for Problems of Materials Science, 3 Krzhyzhanovsky Str., Kyiv, 03680
  • Bogdan Vasyliv Karpenko Physico-Mechanical Institute, 5, Naukova Str., Lviv, 79060
  • Viktoriya Podhurska Karpenko Physico-Mechanical Institute, 5, Naukova Str., Lviv, 79060
  • Mariusz Andrzejczuk Warsaw University of Technology, Faculty of Materials Science and Engineering, Wołoska Str., 141, 02-507 Warsaw
  • Nikkia McDonald Centre for Fuel Cell and Hydrogen Research, School of Chemical Engineering, University of Birmingham, Birmingham, B15 2TT
  • Oleksandr Kyrpa Frantsevich Institute for Problems of Materials Science, 3 Krzhyzhanovsky Str., Kyiv, 03680
  • Orest Ostash Karpenko Physico-Mechanical Institute, 5, Naukova Str., Lviv, 79060
  • Robert Steinberger-Wilckens Centre for Fuel Cell and Hydrogen Research, School of Chemical Engineering, University of Birmingham, Birmingham, B15 2TT
  • Malgorzata Lewandowska Warsaw University of Technology, Faculty of Materials Science and Engineering, Wołoska Str., 141, 02-507 Warsaw, Poland
Keywords: NiO, Ni, RedOx, SOFC anode

Abstract

Yttria stabilized zirconia with a nickel catalyst (Ni-YSZ) is the most developed, widely used cermet anode for manufacturing Solid Oxide Fuel Cells (SOFCs). Its electro-catalytic properties, mechanical durability and performance stability in hydrogen-rich environ­ments makes it the state of the art fuel electrode for SOFCs. During the reduction stage in initial SOFC operation, the virgin anode material, a NiO-YSZ mixture, is reduced to Ni-YSZ. The volume decrease associated with the change from NiO-YSZ to Ni-YSZ creates voids and causes structural changes, which can influence the physical properties of the anode. In this work, the structural, mechanical and electrical properties of NiO samples before and after reduction in pure H2 and a mixture of 5 vol. % H2-Ar were studied. The NiO to Ni phase transformations that occur in the anode under reducing and Reduction-Oxidation (RedOx) cycling conditions and the impact on cell microstruc­ture, strength and electrical conductivity have been examined. Results show that the RedOx treatment of the NiO samples influence on their properties controversially, due to structural transfor­mation (formation of large amount of fine pores) of the reduced Ni. It strengthened the treated samples yielding the highest mechanical strength values of 25.7 MPa, but from another side it is resulting in lowest electrical conductivity value of 1.9×105 S m-1 among all reduced samples. The results of this investigation shows that reduction conditions of NiO is a powerful tool for influence on properties of the anode substrate.

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Published
21-04-2016