Fundamental Investigation of Sintering Anisotropy

Reference Presenter Authors
12-031 Rajendra Kumar Bordia Bordia, R.K.(Clemson University); Martin, C.(Université de Grenoble - Alpes); Olevsky, E.(San Diego State University); Two primary causes of anisotropy in shrinkage during sintering are: (a) anisotropic green microstructure; and (b) anisotropic external applied stresses during sintering. In this presentation, the effect of both these factors on sintering anisotropy will be presented using both experimental results and simulations. For the first case, freeze casting has been used to create green microstructures with designed anisotropic hierarchical porosity. The sintering of these microstructures has been considered both experimentally and using discrete element simulations. The experiments and simulation results agree well and are rationalized in terms of the anisotropy in the orientation of the contacts between particles. In another set of experiments, we have explored the development of anisotropy during sintering in a ceramic that starts of as an isotropic microstructure. The effect of applied stress on the evolution of the pore size, pore shape and orientation has been carefully studied. Multi-scale simulations have been used to understand the observed microstructural evolution. Both of these cases are examples of a special type of anisotropy – transversely anisotropic. A generalized continuum mechanics formulation for transversely isotropic sintering problems will be presented. 

Some of the applications of these anisotropic, hierarchical porous structures in energy conversion and storage will be highlighted. Example of the use of the integrated experimental and simulations research to optimize microstructure design will be presented. As an example, the experimental results on the performance of battery electrodes with anisotropic microstructures will be compared with electrodes with isotropic microstructure to illustrate the advantages of engineered microstructures.
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