Browsing by Subject "zirconium diboride"

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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, Jeremy
This 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.
Freeform Fabrication of Zirconium Diboride Parts Using Selective Laser Sintering
(2008-09-10) Leu, Ming C.; Adamek, Erik B.; Huang, Tieshu; Hilmas, Greg E.; Dogan, Faith
Using the Selective Laser Sintering (SLS) process, both flexural test bars and 3D fuel injector components have been fabricated with zirconium diboride (ZrB2) powder. Stearic acid was selected as the binder. Values of SLS process parameters were chosen such that the green parts could be built with sharp geometrical features and that the sintered parts could have good mechanical properties. After binder burnout and sintering, the SLS fabricated ZrB2 test bars achieved 80% theoretical density, and the average flexural strength of the sintered samples was 195 MPa. These values demonstrate the feasibility of the SLS process for freeform fabrication of 3D parts with the ultra high temperature ceramic.