Molecular dynamics simulation studies have been performed to study the oxygen ion diffusion in yttria stabilized zirconia single crystals and bicrystals separated by tilt grain boundaries (GBs). Two types of GBs which are Σ 5 (3 1 0) and Σ 13 (5 1 0) are studied at temperatures between 1,000 K and 2,000 K. The effect of grain size, which is the distance between two GBs, and the effect of GB orientations are systematically investigated in this study. The oxygen diffusion in the bicrystals is found to be blocked by the GB, and the blocking effect increases with decreasing grain size and is affected by different grain orientations. In addition, the oxygen diffusion along the GB plane is most hindered.

We present a series of experimental results indicating improved oxygen reduction characteristics on nanocrystalline yttria-stabilized zirconia (YSZ) surfaces. We compare (i) cathodic interface impedances on nanocrystalline and microcrystalline YSZ, (ii) oxygen exchange rate on and bulk diffusivity in nano- and single-crystal YSZ, and (iii) bulk and surface conductivities of nano-YSZ. The results collectively indicate that the oxygen reduction/exchange rate is faster on nanocrystalline YSZ than on micro- and single-crystal YSZ, which likely is related to fast oxygen or electronic transport on the surface.

Articles you may be interested inThe isotropic-nematic phase transition of tangent hard-sphere chain fluids-Pure components J. Chem. Phys. 139, 034505 (2013) Equation of state and structure of hard-sphere fluids confined in a cylindrical hard pore were investigated at the vicinity of fluid-solid transition via molecular dynamics simulation. By constructing artificial closed-packed structures in a cylindrical pore, we explicitly capture the fluid-solid phase transition and coexistence for the pore diameters from 2.17 to 15. There exist some midpore sizes, where the phase coexistence might not exist or not clearly be observable. We found that the axial pressure including coexistence follows oscillatory behavior in different pore sizes; while the pressure tends to decrease toward the bulk value with increasing pore size, the dependence of the varying pressure on the pore size is nonmonotonic due to the substantial change of the alignment of the molecules. The freezing and melting densities corresponding to various pore sizes, which are always found to be lower than those of the bulk system, were accurately obtained with respect to the axial pressure.

Articles you may be interested inFluid-solid phase transition and coexistence of square-well fluids confined in narrow cylindrical hard pores are characterized using molecular simulation methods. The equation of state containing a fluid phase, a solid phase and a fluid-solid coexistence state was separately obtained for different attractive ranges of potential well and pore diameters; = 1.2, 1.3, 1.4, and 1.5 for a pore of diameter D = 2.2 , = 1.5 and 1.65 for a pore of diameter D = 2.5 . For = 1.2, 1.3, and 1.4 at pore diameter D = 2.2 , = 1.5 at D = 2.5 , the fluid-solid phase coexistence densities and pressure are close to the hard sphere fluids at the same temperature, while the pressure decreases significantly for = 1.5 at D = 2.2 and = 1.65 at D = 2.5 , respectively. We also report the structural properties of the systems undergoing a phase transition.

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