Nickel coarsening

Simwonis, D.,Tietz, F. Stover. D. Nickel coarsening in annealed Ni/SYSZ anode substrates for solid oxide fuel-cells. Solid State Ionics 132 (2000), pp. 241-251. 

Apart from nickel coarsening, additional causes of the inadmissible increase in anodic overpotentials can be thought of as blockage of the nickel network by the presence of SDC particles, poor adhesion between the anode and the electrolyte, slow In situ steam reforming reaction of methane on nickel, insufficient active length of triple-phase boundaries, and so on. To overcome these... 

Low redox cycling tolerance. Redox cycling occurs when the fuel flow to the stack is interrupted. Air leaking in from the environment will oxidize the nickel. Upon recovery of the fuel flow the nickel oxide will reduce again. Such a cycle will cause considerable performance loss due to coarsening of the nickel particles in the anode. 

Iwashita, C. H., and Wei, R. P., Coarsening of Grain Boundary Carbides in a Nickel-Base Ternary Alloy During Creep, Acta Mater., 48 (2000), 3145-3156. 

Kang TK, Yoon DN (1978) Coarsening of tungsten grain in Uquid nickel-tungsten matrix. MetaU Trans A-Phys MetaU Mater Sci 9 433 38... 

Kang, T.-K. and Yoon, D. N., Coarsening of tungsten grains in liquid nickel-tungsten matrix, MetalL Trans. A, 9A, 433-38, 1978. 

In the present work, steel oxidation by oxygen provided by nickel oxide was identified as the main source for volume expansion and the limited shrinkage of the half-cell multilayer. In addition, intense Cr-Fe-Ni interdiffusion and Ni coarsening were observed when the different materials are co-sintered. The Cr oxide formed on the steel surface at 1000 C seems to limit Ni diffusion through the steel, but it cannot prevent Fe outward diffusion when the temperature is further increased. 

This alloy exhibits resistance to nitriding, excellent long-term thermal stability, and low thermal expansion. It is also resistant to grain coarsening at high temperatures. Good resistance to carburization is also displayed. Because of its nickel matrix, the alloy does not possess adequate resistance to sulfadizing enviromnents. 

For preparation of the anode, a slurry composed of NiO and Ceo.8Smo.2O2 s (SDC) mixture is screen printed onto the electrolyte. The firing process involves treatment of the screen-printed anode layer on the electrolyte at 1100°-1300°C for 3 h in air. The relative amounts and particle size ratios of the mixture of NiO and SDC are optimized in such a way that the resulting microstructure is resistant to coarsening of reduced nickel particles under the operating... 

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