Insights into the Second Law of Thermodynamics from Anisotropic Gas-Surface Interactions

Thermodynamic implications of anisotropic gas-surface interactions in a closed molecular flow cavity are examined. Anisotropy at the microscopic scale, such as might be caused by reduced-dimensionality surfaces, is shown to lead to reversibility at the macroscopic scale. The possibility of a self-sustaining nonequilibrium stationary state induced by surface anisotropy is demonstrated that simultaneously satisfies flux balance, conservation of momentum, and conservation of energy. Conversely, it is also shown that the second law of thermodynamics prohibits anisotropic gas-surface interactions in "equilibrium", even for reduced dimensionality surfaces. This is particularly startling because reduced dimensionality surfaces are known to exhibit a plethora of anisotropic properties. That gas-surface interactions would be excluded from these anisotropic properties is completely counterintuitive from a causality perspective. These results provide intriguing insights into the second law of thermodynamics and its relation to gas-surface interaction physics.Comment: 28 pages, 11 figure

Synthesis and properties of mullite-type (Bi1-xSrx)(2)((M1-yMy2)-M-1)(4)O9-x (M = Al, Ga, Fe)

Mullite-type A(2)M(4)O(9) phases (M = Al, Ga, Fe), representing promising oxygen conducting materials for solid oxide fuel cells (SOFCs), were synthesized using the glycerine- and the EDTA/citric acid synthesis method. For strontium-doped material pure phases could be obtained only by washing the samples after the heating in both synthesis methods. Temperature dependent investigations were carried out to show the influence of the metal atoms on the structural stability and thermal expansion coefficients. Whereas the Sr-free phases show a quasi linear thermal expansion behavior in all three directions up to their incongruent melting points, a discontinuity in the measured range is observed for the investigated strontium doped dibismuth-nonaoxotetrametallate(III) caused by the decomposition into Bi2M4O9, strontium metallates and bismuthoxide. Big single crystals were only observed for the Sr-free compound, of which the structure of Bi-2(Ga0.45Fe0.55)(4)O-9 will be presented here in the Barnighausen tree corresponding mulfite-type setting. (C) 2011 Elsevier Ltd. All rights reserved