Masters Theses

Abstract

"The mechanical properties and processing parameters of boride ceramics in foam and laminate architectures were evaluated. The ceramic reticulated foam was produced through a polymer substrate replication technique and the hardness and compressive strength were tested. The laminate structure was tested to evaluate the flexure strength and work of fracture as a function of temperature.

The foam architecture was produced using a TiB2 slurry coating on a polyurethane reticulated foam preform. Foams sintered to 2150⁰C displayed an average grain size of 8.9 ± 7.3 µm, and a hardness of 17.3 ± 2.4 GPa. Crush testing foams were sintered at 1975⁰C, and displayed a specific strength of 208 ± 63 kPa with an overall porosity of 97%. For these specimens, it is likely that microcracking lowered the hardness, but the overall strength was controlled by the bulk density.

The laminate structures were fabricated using alternating layers of ZrB2 and C--10 vol% ZrB2. The structures were fabricated through the shaping of ceramic loaded thermoplastic polymers that underwent burnout and hot pressing cycles. These specimens had strong phase ZrB2 layers that were about 150 µm thick alternating with weak phase layers that were about 20 µm thick. Specimens exhibited a maximum flexure strength of 311 ± 10 MPa at 1600⁰C, and an increased work of fracture compared to conventional ZrB2 ceramics. The maximum fraction of inelastic work of fracture occurred at room temperature, and decreased as temperature increased. This was reflected in the length of the crack path through the specimen. Deflected cracks travelled through the center of the C--ZrB2 layers in the material in Mode II fracture"--Abstract, page iv.

Advisor(s)

Fahrenholtz, William

Committee Member(s)

Hilmas, Greg
Watts, Jeremy Lee, 1980-

Department(s)

Materials Science and Engineering

Degree Name

M.S. in Ceramic Engineering

Sponsor(s)

United States. Air Force. Office of Scientific Research

Comments

Financial support of United States Air Force Office of Scientific Research, grant FA9550-14-1-0385, Dr. Ali Sayir, program director

Publisher

Missouri University of Science and Technology

Publication Date

Summer 2017

Journal article titles appearing in thesis/dissertation

  • Processing and mechanical properties of TiB2 reticulated foams
  • Processing and elevated temperature mechanical properties of ZrB2-based laminates

Pagination

ix, 65 pages

Note about bibliography

Includes bibliographical references.

Rights

© 2017 Connor Charles Wittmaier, All rights reserved.

Document Type

Thesis - Open Access

File Type

text

Language

English

Thesis Number

T 11192

Electronic OCLC #

1003049826

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