Thermomechanical Responses of Microcracks in a Honeycomb Particulate Filter

Manufacturing honeycomb-structured catalysts require a careful understanding of the microstructure of the solid substrate and its dependence on thermal-processing conditions. Herein, it is the thermal responses of microcracks in an uncoated microcracked aluminum titanate honeycomb catalyst is investigated by analyzing the material's resonance frequency using the high-temperature impulse excitation technique. The resonance frequencies are presented as Young's modulus values to avoid sample size effects. Dynamic Young's modulus measurements show closed-loop hysteresis due to microcracks healing and reopening, causing a reversible response. The hysteresis is further used to understand microcracks’ dependence on critical thermal-processing conditions used in a catalyst manufacturing plant, including peak operating temperature (800–1000 °C), dwell period (1–3 h), and heating rates (1–5 °C min⁻¹). Microcracks are observed to have two healing responses: instantaneous and delayed healing. Both responses significantly influence the design of catalyst manufacturing. Complete reopening of microcracks from their healing temperature (1150 °C) is a very time-consuming process (50–60 h). However, it is shown in the analysis that microcrack relaxation is a critical phenomenon that must be considered in quality-controlled environments.