Doctoral Dissertations

Keywords and Phrases

Additive manufacturing; Direct ink write; Functionally graded materials; Low temperature co-fired ceramics; Robocasting; Ultra-high temperature ceramics

Abstract

"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

Advisor(s)

Hilmas, Greg

Committee Member(s)

Watts, Jeremy L.
Leu, M. C. (Ming-Chuan)
Kumar, Aditya
Convertine, Anthony J.

Department(s)

Materials Science and Engineering

Degree Name

Ph. D. in Materials Science and Engineering

Publisher

Missouri University of Science and Technology

Publication Date

Summer 2022

Pagination

xiv, 153 pages

Note about bibliography

Includes_bibliographical_references_(pages 137-152)

Rights

© 2022 Austin Johnathan Martin, All Rights Reserved

Document Type

Dissertation - Open Access

File Type

text

Language

English

Thesis Number

T 12279

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