Control of non-equilibrium microstructure and function of oxide scales formed in high temperature oxidation of metalic materials for high efficiency energy comversion

点击翻译按钮获取中文摘要

(1)Quantitative prediction of void formation in a growing scales in high temperature oxidationEquations have been proposed for evaluation of chemical potential distribution, ionic fluxes and its divergence in a growing oxide scales. The divergence was proved to be the good measure for evaluating the void formation. The validity was experimentally confirmed in magnetite scales formed in high temperature oxidation of iron.(2)High temperature oxidation of ferritiv Fe-Cr alloys for interconnects in solid oxide fuel cell (SOFC) and electrical conductivity of the oxide scale.Simulating the operation condition of SOFC, high temperature oxidation of Fe-16Cr alloys was conducted in the dual atmosphere, in which specimens were exposed air for the cathode and the mixture of H2O (97%) and H2 (3%) at 1073 K. The continuous protective Cr2O3 scales were formed on both sides. The growth rates were quite similar, indicating the major defect was interstitial ion of Cr in two cases.The estimation of the … More oxygen potential distribution clarified that the oxygen potential is low almost the whole region in scales. This fact predicted the reason why the electrical conductivity of the Cr2O3 scales were high. Applied external currents retarded the growth rate of Cr203 on the cathode and enhanced it on the anode. The equations were proposed for evaluating the scale growth rate under the external current and the equations predicted the growth rate in the long term exposures.(3)Control of microstructure development and design of the function of the scales.The summary of this project is the following(1)The quantitative prediction of microstructure development is possible with diffusion coefficients of constituent ions as a function of oxygen potential.(2)For controlling microstructure, it is dispensable to design the diffusivity. The appropriate doping is an possibility for the design of the microstructure.(3)The evaluation of chemical potential distribution and divergences of ionic fluxes is very powerful for controlling microstructures and designing the function of scales. Less