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

本提案的基本思想是首次研究高微裂纹和多孔柴油颗粒过滤器（DPF）陶瓷在中观（亚毫米）和宏观（整个样品）尺度上的形态学（孔隙空间）和晶体学（畴取向）织构之间的关系。我们计划结合使用空间分辨x射线折射和衍射形貌。通过使用这些中观和宏观尺度的信息（即通过中子和常规x射线衍射或从计算机断层扫描数据分析获得的整个标本的集成），我们还旨在模拟力学（杨氏模量）和物理（热膨胀）性能的演变，分离和包含孔隙率和微裂纹的影响，从而为此类材料阐述新的本构定律。一般来说，在公共领域中很少有关于dpf的工作，其中很大一部分来自申请人。因此，该项目将填补公众对微裂多孔陶瓷的机械和热性能的科学理解的巨大空白。在墨卡托研究员的帮助下，将开发详细的数值和分析模型，以解释通过新型内聚元素的微裂纹扩展（将在项目期间开发，并提供TEM和SEM数据）。这种有凝聚力的元素将能够模拟裂缝愈合、关闭和重新打开。结合实验和数值数据，进一步阐明微开裂机理。事实上，该项目的另一个主要目标是制定本构律（在中观和宏观尺度上）。一个现象学的本构模型将建立在一个具有代表性的体积元上。开发的数值框架应作为“虚拟实验室”，以评估不能直接测量的数量（如晶间键的强度）。将研究具有不同程度微裂纹、孔隙度和晶体结构的DPF陶瓷（高度微裂纹的钛酸铝与高度多孔但轻度微裂纹的堇青石和几乎没有微裂纹的碳化硅）。经典的先进微观结构表征（3D光学显微镜、透射和扫描电子显微镜、汞孔隙度测定法）和高温杨氏模量测量也将用于为模型提供输入和验证数据。最后，利用已有的实验数据进行对比。

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.