Browsing by Subject "ceramic on-demand extrusion"
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Item Designed Extrudate for Additive Manufacturing of Zirconium Diboride by Ceramic On-Demand Extrusion(University of Texas at Austin, 2016) McMillen, Devin; Li, Wenbin; Leu, Ming C.; Hilmas, Gregory E.; Watts, JeremyThis work describes a process by which zirconium diboride (ZrB2) parts may be fabricated using the Ceramic On-Demand Extrusion (CODE) process. An oxide-carbide-nitride system consisting of ceramic powders and pre-ceramic organics, designed to yield ZrB2 after reaction sintering, has been developed to produce an aqueous-based extrudate for subsequent processing in the CODE system. Pressurelessly sintered test specimens containing 1 wt% PVA binder achieve high relative density ≥ 99%. The viscoelastic response of the extrudate was characterized via spindle rheometry with a small sample adapter. Batches with 1 wt% PVA and 0.5 wt% Methocel show strong shear thinning characteristic, under shear rates of 1-28 s-1. XRD and SEM were utilized for microstructural analysis to determine phase development and microstructural morphology.Item Fabricating Functionally Graded Materials by Ceramic On-Demand Extrusion with Dynamic Mixing(University of Texas at Austin, 2018) Li, Wenbin; Martin, Austin J.; Kroehler, Benjamin; Henderson, Alexander; Huang, Tieshu; Watts, Jeremy; Hilmas, Gregory E.; Leu, Ming C.Ceramic On-Demand Extrusion (CODE) is an extrusion-based additive manufacturing process recently developed for fabricating dense, functional ceramic components. Presented in this paper is a further development of this process focusing on fabrication of functionally graded materials (FGM). A dynamic mixing mechanism was developed for mixing constituent ceramic pastes, and an extrusion control scheme was developed for fabricating specimens with desired material compositions graded in real time. FGM specimens with compositions graded between Al2O3 and ZrO2 were fabricated and ultimately densified by sintering to validate the effectiveness of the CODE process for FGM fabrication. Energy dispersive spectroscopy (EDS) was used to compare final compositions to the original material designs. The specimen’s hardness at different locations along the gradients was examined by micro-indentation tests. The dimensions of sintered specimens were measured, and the effects of material composition gradients on the distortions of sintered FGM specimens were analyzed.Item Fabricating Zirconia Parts with Organic Support Material by the Ceramic On-Demand Extrusion Process(University of Texas at Austin, 2017) Li, Wenbin; Ghazanfari, Amir; McMillen, Devin; Scherff, Andrew; Leu, Ming C.; Hilmas, Gregory E.Ceramic On-Demand Extrusion (CODE) is an extrusion-based additive manufacturing process recently developed for fabricating dense, functional ceramic components. This paper presents a further development of this process and focuses on fabricating 3 mol% yttria-stabilized zirconia (3YSZ) components that cannot be fabricated without using support structures. The 3YSZ paste is deposited through the main nozzle, and a polycaprolactone (PCL) pellet feedstock is melted and deposited through an auxiliary nozzle to build support structures. After a green part is printed and dried, the support structures are removed by heating the part to ~70 °C to melt the PCL. The part is then sintered at 1550 o C to achieve near theoretical density. The maximum angle of overhanging feature that can be fabricated without support was determined to be 60°. Sample parts were fabricated and evaluated to demonstrate the effectiveness of the PCL support material and CODE’s capability to fabricate geometrically complex parts.Item Properties of Partially Stabilized Zirconia Components Fabricated by the Ceramic On-Demand Extrusion Process(University of Texas at Austin, 2016) Li, Wenbin; Ghazanfari, Amir; McMillen, Devin; Leu, Ming C.; Hilmas, Gregory E.; Watts, JeremyThe Ceramic On-Demand Extrusion (CODE) process is a novel additive manufacturing process for fabricating dense ceramic components from aqueous pastes of high solids loading. In this study, 3 mol% Y2O3 stabilized tetragonal zirconia polycrystal (3Y-TZP) parts were fabricated using the CODE process. The parts were then dried in a humidity controlled environmental chamber and sintered under atmospheric pressure. Mechanical properties of the sintered parts were examined using ASTM standard test techniques, including density, Young’s modulus, flexural strength, Weibull modulus, fracture toughness and Vickers hardness. The microstructure was analyzed, and grain size was measured using scanning electron microscopy. The results compared with those from Direct Inkjet Printing, Selective Laser Sintering, and other extrusion-based processes indicated that zirconia parts produced by CODE exhibit superior mechanical properties among the additive manufacturing processes. Several example parts were produced to demonstrate CODE’s capability for fabricating geometrically complex ceramic parts.