Visualizing the Effect of Extrusion Velocity on the Spatial Variation of Porosity in a Titanium Dioxide/Binder System

Abstract

Extrusion is a common process technique used to fabricate porous materials such as catalysts and membranes. The performance and efficiency of such materials are governed by porosity and pore distribution. The spatial variation of porosity within the catalyst structure can be linked to process variables in the extrusion processes such as extrusion velocity. A change in extrusion velocity can lead to a change in extrusion pressure. The extrusion pressure effect is a combination of die entry deformation and frictional die land shear. In this work, the effect of extrusion velocity on the spatial variation of porosity in a titania-binder extrudate has been studied. Capillary rheometer analysis was done to investigate the effect of extrusion velocity. A segmentation approach was developed to study the spatial variation of porosity at the die wall (sheared region) compared to the unsheared (center) region of the extrudate. The results show that the extrusion pressure effect increases as the velocity increases. The extrusion conditions affect the spatial variation of porosity.

Green Microstructural Visualization of Dry-Pressed Spray-Dried Alumina (Al<sub>2</sub>O<sub>3</sub>)

“…Ku [28] developed a method using Spurr Low Viscosity Kit epoxy to infiltrate ceramic powders within interparticle pores without causing dispersion or breakage. Alazzawi et al [29] has shown this infiltration method can successfully infiltrate green titanium dioxide extrudates for microstructural characterization with the use of a FESEM and charge mitigation techniques for higher resolution microstructural characterization. This method will be the method investigated for this paper.…”