Correlation between spatially resolved morphological and crystallographic texture in porous diesel particulate filter ceramics, and its implications on their microcracking behavior

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The basic idea of this proposal is to investigate for the first time, the correlation between morphological (pore space) and crystallographic (domain orientation) texture for highly microcracked and porous diesel particulate filter (DPF) ceramics at meso (sub-mm) and macro (over the whole specimen) scale. We plan to make combined use of spatially resolved X-ray refraction and diffraction topography. By the use of such meso- and macro-scale information (i.e. integrated through the whole specimens and obtained by neutron and conventional X-ray diffraction or from the analysis of computed tomography data), we also aim at modeling the evolution of mechanical (Young’s modulus) and physical (thermal dilation) properties, separating and encompassing the effects of porosity and microcracking, and thereby elaborating new constitutive laws for such materials. In general, very little work on DPFs is available in the public domain, and a significant part of it comes from the applicant. This project will therefore fill an enormous gap in the publicly available scientific understanding of mechanical and thermal properties of microcracked porous ceramics. With the aid of a Mercator Fellow, detailed numerical and analytical models will be developed to account for microcrack propagation through new types of cohesive elements (to be developed during the project and to be fed with TEM and SEM data). Such cohesive elements will be capable of simulating crack healing, closure, and re-opening. Combining experimental and numerical data, the mechanisms of microcracking will be further elucidated. In fact, another main objective of the project is to formulate constitutive laws (both at a meso- and at macro-scale). A phenomenological constitutive model will be built on a representative volume element. The developed numerical framework should serve as a “virtual laboratory” to assess quantities that are not directly measurable (such as the strength of intergranular bonds). DPF ceramics with varying degrees of microcracking, porosity, and crystallographic texture will be studied (highly microcracked aluminum titanate versus highly porous but mildly microcracked cordierite and virtually non-microcracked silicon carbide). Classic advanced microstructural characterization (3D Optical Microscopy, Transmission and Scanning Electron Microscopy, Hg porosimetry) and high-temperature Youngs’ modulus measurements will also be used to feed the models with input and validation data. Finally, existing experimental data will also be used as a comparison.