Masters Theses

Abstract

"A novel spiral architecture was formed using titanium diboride and silicon carbide ceramics as either the spiral or matrix phase. Particulate composites with the same compositions were fabricated to compare to the materials in this study. Spiral additions were formed using powder loaded polymers followed by a single and/or multi-filament co-extrusion. For 25 vol% SiC spiral additions to TiB2, boron nitride was added to the SiC spiral to alter the bonding at the interface and reduce thermal residual stresses. All samples were hot-pressed to near full density at 1980 ⁰C. Hot pressed multi-filament co-extrusion of 2.4 mm / 1 mm resulted in the smallest, consistent spirals ~50 µm in diameter. For the SiC spirals in TiB2 study, the room temperature flexure strength was 193 ± 17 MPa, with the particulate composite being 488 ± 45 MPa. The fracture toughness for the spiral material was as high as 7.5 ± 0.6 MPa·m1/2 with the particulate composite being 5.3 ± 0.4 MPa·m1/2. Spiral length was studied with TiB2 spirals in a SiC matrix. The resulting average room temperature flexure strength was 313 ± 11 MPa and 417 ± 41 MPa for spiral and monolithic samples, respectively. Fracture toughness was increased from 4.2 ± 0.2 MPa·m1/2 for the monolithic to 6.2 ± 0.4 MPa·m1/2 with the addition of spirals. The higher fracture toughness is a result of crack deflection in and around the spiral inclusions. Wear testing resulted in a loss of 1.1 mm3 and 3.3 mm3 per 6000 revolutions for monolithic and uniaxial specimens, respectively. While more wear was observed, the strength of the uniaxial samples after wear increased 16% whereas monolithic strength decreased 18%"--Abstract, page iv.

Advisor(s)

Watts, Jeremy Lee, 1980-

Committee Member(s)

Hilmas, Greg
Fahrenholtz, William

Department(s)

Materials Science and Engineering

Degree Name

M.S. in Materials Science and Engineering

Sponsor(s)

University of Missouri Research Board

Publisher

Missouri University of Science and Technology

Publication Date

Fall 2014

Pagination

xii, 71 pages

Note about bibliography

Includes bibliographical references (pages 67-70).

Rights

© 2014 Andrea Lynn Els, All rights reserved.

Document Type

Thesis - Open Access

File Type

text

Language

English

Subject Headings

Ceramic-matrix composites
Materials -- Dynamic testing
Fiber-reinforced ceramics -- Fracture

Thesis Number

T 10580

Electronic OCLC #

902730955

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