Structural Transformations in the Nio-Containing Anode of Ceramic Fuel Cells in the Course of its Reduction and Oxidatio
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STRUCTURAL TRANSFORMATIONS IN THE NiO-CONTAINING ANODE OF CERAMIC FUEL CELLS IN THE COURSE OF ITS REDUCTION AND OXIDATION V. Ya. Podhurs’ka,1 B. D. Vasyliv,1 O. P. Ostash,1, 2 O. D. Vasyl’ev,3 and E. M. Brodnikovs’kyi3
UDC 666.3: 539.4.015
We study the role of structural transformations in the nickel phase under the action of reducing and oxidizing high-temperature (600°С) gaseous atmospheres in the formation of the levels of strength and electric conductivity of NiO-containing materials for the anodes-substrates of ceramic fuel cells. By using the cyclic redox treatment (redox cycling) of NiO oxide, which includes the stages of heating in a vacuum up to a fixed temperature (600°С), reduction of the heated material in a Ar–5 vol.% H2 gaseous mixture, degassing, and oxidation in air at the same temperature, we managed to form a structure guaranteeing the improved physicomechanical characteristics of YSZ–Ni and ScCeSZ–Ni composites. Keywords: ceramic fuel cell, anode-substrate, NiO-containing ceramics, redox treatment, electric conductivity, strength.
The principal directions of improvement of the existing models of ceramic (solid-oxide) fuel cells (CFC) include the creation of structures of the anode, cathode, and electrolyte resistant to degradation in working media and the optimization of the structure of CFC as a layered macrocomposite [1–3]. As one of the efficient procedures used for the improvement of the mechanical and electrochemical properties of NiO-containing anodessubstrates of the CFC, we can mention their cyclic redox treatment (redox cycling) in certain optimized modes [4–8]. However, the mechanisms of formation of the most widespread NiO-containing anode structures and, in particular, composites of the YSZ–NiO and 10Sc1CeSZ–NiO systems, in the course of this kind of treatment still remain insufficiently studied. For their comprehension, it is reasonable to concentrate attention on the investigation of the specific features of structural transformations in the nickel phase under the action of reducing and oxidizing high-temperature gaseous atmospheres by using model specimens made of nickel oxide because the ceramic frame of the YSZ or ScCeSZ composites (zirconium oxide stabilized by yttrium or by scandium and cerium) under these conditions does not undergo noticeable structural transformations [9]. The aim of the present work is to analyze the role of structural transformations in the nickel phase under the action of reducing and oxidizing high-temperature (600°С) gaseous atmospheres in the formation of the levels of strength and electric conductivity of NiO-containing materials for the anodes-substrates of the CFC. Materials and Experimental Procedure We study specimens sintered by using pure NiO powders at the Frantsevych Institute for Problems in Materials Science of the Ukrainian National Academy of Sciences [10]. 1 2 3
Karpenko Physicomechanical Institute, Ukrainian National Academy of Sciences, Lviv, Ukraine. Corresponding author; e-mail: [email protected].
Frantsevych Institute for Problem
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