Processing to Enable Direct-Write Additive Manufacturing of Ceramics and Ceramic Composites
"This research focuses on the processing of novel feedstocks for and during direct-write additive manufacturing (AM), specifically the direct ink writing (DIW) and Ceramic On-Demand Extrusion (CODE) manufacturing processes, in order to produce ceramic and ceramic-based composite components. Strongly dispersed, concentrated (φ = 0.42), nanoparticle (d50 ~0.3 µm), zirconia (ZrO2) pastes were used to print densely filled, large continuous volume (≳ 1 cm3) ceramic components. An elastic shear modulus (G’) of 56,000 Pa and yield stresses between 6 and 10 Pa allowed for printed components of 34.5 mm in height over 115 layers without slumping due to partial drying. Printed parts exhibited lateral particle migration during post-processing. Several methods were proposed to improve future feedstocks to prevent this defect. A zirconium diboride (ZrB2) paste (φ = 0.45) was formulated to print fine-featured (<335 >µm), ultra-high temperature ceramic (UHTC) monoliths. The final ZrB2-based paste exhibited an elastic shear modulus of ~104 Pa, flow index of 0.34, and flow stress of ~40 Pa, as-designed for monolithic printing. In discrete multi-material printing, dielectric and conductor formulations were printed together to established considerations for co-DIW of ceramic electronic packaging technologies. Low temperature co-fired ceramic (LTCC) structures were demonstrated by co-printing but were not successfully post-processed due to mismatched co-drying. In graded printing, a Mo (φ = 0.45) paste was developed to print with ZrB2. These formulations were successfully combined to 3D print 11 layer, 10% gradings between the constituents into laminar bars. These bars were pressurelessly sintered to 2050°C without observed cracking but had an average warpage of 20 ± 9°"--Abstract, p. iv
Additive manufacturing, Direct ink write, Functionally graded materials, Low temperature co-fired ceramics, Robocasting, Ultra-high temperature ceramics, Materials Science and Engineering
Missouri University of Science and Technology
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