Fabrication of self-supporting structures made of washcoat materials (γ-Al₂O₃-CeO₂) by ceramic stereolithography: Towards digital manufacturing of enhanced catalytic converters

Abstract

Despite increasing interest in the use of alternative fuel, conventional diesel or gasoline powered vehicles still dominate road transportation; removal of their emitted pollutants is a challenge to sustainable transportation. The automotive industry has employed catalytic converters (CCs) to effectively modify or eliminate toxic pollutants emitted by combustion engines. The efficiency of a CC greatly depends on its geometry and is hindered by limitations in fabrication techniques. To go beyond these limits and further enhance the performance of CCs, one can use state-of-the-art ceramic stereolithography (CSL) technology, which enables fabrication of complex-shaped structures. In this work, a novel photocurable ceramic resin made of γ-Al2O3 and CeO2 (the commonly used washcoat materials in CCs) is shaped into the honeycomb and twisted honeycomb structures using CSL. Measurements reveal that upon the addition of CeO2 to the plain γ-Al2O3 resin, the penetration depth of light is significantly decreased from 408.06 μm to 75.19 μm. This research also focuses on the balance between having a high surface area and achieving good physical stability in the printed structures. Accordingly, the appropriately debinded structures are sintered at two different temperatures: 900 °C and 1100 °C. It is found that the structure sintered at 900 °C has a higher surface area, and thus, it is a better candidate for catalytic applications. Furthermore, investigation of the stabilizing effect of CeO2 on printed γ-Al2O3 finds that CeO2 is effective in stabilizing the printed γ-Al2O3 at1100 °C but not 900 °C. Targeting the realization of green and sustainable transportation, the applied CSL technique in this study enables flexible control in the design and fabrication of self-supporting structures that are expected to open promising ways for the optimization of CCs.