P. MICHAUX, G. Montavon, A. DENOIRJEAN, SPCTS - UMR CNRS 6638, Faculty of Sciences, Limoges cedex, France; P. Fauchais, University of Limoges, Limoges, France
Intermediate Temperature – Solid Oxy-Fuel Cells (IT-SOFC) include in their design anode layer made usually of cermet layer of Ni and Yttria-Stabilized Zirconia (Y-PSZ) through which hydrogen species permeate. This layer needs to fulfill several characteristics: a controlled pore network architecture ensuring the permittivity factor, an adequate Ni over Y-PSZ volume fraction and a fine dispersion of Y-PSZ among nickel to limit to the maximum possible extend sintering during operation.
Several manufacturing routes are possible to process this functional layer. Thermal spraying appears as a pertinent one thanks to its versatility and flexibility. Decreasing the size of the precursors permits to improve the layer performances thanks to a finer structure and porous architecture allowing a higher reactive rate between nickel and hydrogen species.
One possible route aims at spraying micrometer-sized agglomerates of nanometer-sized nickel mono-oxide and Y-PSZ. Beside the sharpened carcinogen character of nickel mono-oxide, layers manufactured via this route exhibit a two-scale structure, nanometer- and micrometer-sized, corresponding to particle cores that were not molten within the plasma flow and particle peripheral areas that were molten, respectively. Such a structure impedes the layer functional properties by decreasing its mechanical and reactive properties.
This papers aims at presenting alternative routes to manufacture Ni/8Y-PSZ cermet thick layers exhibiting nanometer-sized architectures. Two different processes were considered: i) suspension plasma spraying (SPS) using a suspension of Ni/8YSZ nanometer-sized particles synthesized by a chemical route and ii) solution precursor plasma spraying (SPPS) using a mixture of raw salts of components.
Effects of some operating parameters (spray distance, plasma flow mass enthalpy, etc.) on the porosity, morphology and composition of the resulting coatings were investigated. These parameters appear more critical in the SPPS process compared to the SPS one since a chemical precipitation should take place in the time of only a few milliseconds of reaction.
Summary: This papers aims at presenting alternative routes to manufacture Ni/8Y-PSZ cermet thick layers exhibiting nanometer-sized architectures in view of improving functional performances of SOFC anodes. Two different processes were considered: i) suspension plasma spraying (SPS) using a suspension of Ni/8YSZ nanometer-sized particles synthesized by a chemical route and ii) solution precursor plasma spraying (SPPS) using a mixture of raw salts of components in the appropriate molar fractions.
Effects of some operating parameters (spray distance, plasma flow mass enthalpy, etc.) on the porosity, morphology and composition of the resulting coatings were investigated. These parameters appear more critical in the SPPS process compared to the SPS one since a chemical precipitation should take place in the time of only a few milliseconds of reaction.
