Masters Theses

Xuan Lin

Abstract

"Boron carbide whisker reinforced alumina matrix composites were prepared by pressureless sintering process. The sintering parameters which control the composite densification were studied. The maximum composite densities were achieved at 1800°C for 60 minutes. Carbon-containing atmospheres were proved to be suitable for the composite to get densified, and the oxygen partial pressures corresponding to CO/CO2 ratio showed no effect on the composite densification provided no oxidation on the B4C phase.

The boron carbide whiskers were screen classified into five size fractions, and the effect of inclusion size was presented. The composites with fine inclusion size exhibited better sinter ability than those with coarser size, and narrow size distribution yielded higher densities than wider distribution. The maximum relative densities of 98 ~ 89% were achieved for composites containing 10 ~ 40 vol% B4C whiskers with size range of -325+400 mesh. Micrograph analysis revealed that B4C acts as sintering aid to Al203 via mechanisms other than being grain-growth inhibitor.

Fracture toughness improvement was observed and a K1c of ≈6.2 MPa.m1/2 was achieved with 20 vol% whiskers. Compared to alumina, the composites increased the hardness up to ≈25%, but didn't improve the flexural strength. A stoichiometry change of the boron carbide during sintering was detected from the X-ray diffraction analysis. An unidentified phase was found in sintered composites, indicating a reaction between Al203 and B4C"-- Abstract, p. ii

Advisor(s)

Ownby, P. D.

Committee Member(s)

Rahaman, M. N., 1960-
Leighly, Hollis P., 1923-2004

Department(s)

Materials Science and Engineering

Degree Name

M.S. in Ceramic Engineering

Publisher

University of Missouri--Rolla

Publication Date

Spring 1995

Pagination

x, 82 pages

Note about bibliography

Includes bibliographical references (pages 75-81)

Rights

© 1995 Xuan Lin, All rights reserved.

Document Type

Thesis - Restricted Access

File Type

text

Language

English

Thesis Number

T 6949

Print OCLC #

32844946

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