Browsing by Subject "thermal stability"

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    Finite element study of Li diffusion and stress in LiNi0.33Mn0.33Co0.33O2 cathode using microstructures reconstructed by synchrotron X-ray tomography
    (Office of the Vice Chancellor for Research, 2016-04-08) Wu, Linmin; Zhang, Yi; Zhang, Jing
    LiNi0.33Mn0.33Co0.33O2 is a good substitute for LiCoO2 because of its good thermal stability and high energy density. In this study, the diffusion and stress in LiNi0.33Mn0.33Co0.33O2 cathode with realistic three-dimensional (3D) microstructures have been studied systematically. Synchrotron Xray tomography was used to obtain the 3D reconstructions of porous LiNi0.33Mn0.33Co0.33O2 microstructures. Li concentration distributions under various C-rates were investigated. The obtained charge/discharge curves under various C-rates were compared with the results from Newman’s model. The stress generation in the cathode was computed coupled with the diffusion. The hydrostatic stress, shear stress and von Mises stress in the particles were analyzed. The results show that the von Mises stress in particle boundaries is higher than the stress inside the particle due to the Li concentration gradient during discharge, which is consistent with the literature. Additionally, the von Mises stress near the particle contact region is much higher than other areas.
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    Thermal Stability of Novel Multilayer Lanthanum Zirconate Based Thermal Barrier Coatings
    (Wiley, 2016) Guo, Xingye; Lu, Zhe; Jung, Yeon-Gil; Li, Li; Knapp, James; Zhang, Jing; Department of Mechanical Engineering, School of Engineering and Technology
    This chapter discusses the thermal stability of SCL and DCL porous La2Zr2O7 coats by depositing three types of SCL and DCL La2Zr2O7 and 8YSZ structures in an experiment. Heat treatment, cyclic furnace cycle test and jet engine thermal shock test were conducted for the thermal barrier coatings (TBC) samples. The heating and cooling cycles were repeated until cracks or spallation were spotted on the TBC surface. Both the front and back surface temperatures were measured using pyrometer. The delamination is caused by the thermal residual stress induced by CTE difference between La2Zr2O7 and 8YSZ. All the La2Zr2O7 coats were delaminated in the furnace cycle test in less than 20 cycles. This is because residual thermal stresses accumulated during thermal cycling. Microstructure images of heat treated samples were taken using a scanning electron microscope.