Effects of microstructural instability on the creep behavior of Si-C-O (Nicalon) fibers in argon

Journal Article · Wed Dec 01 04:00:00 EST 1993 · Journal of the American Ceramic Society; (United States)

OSTI ID:5429508

Jia, Nanying; Bodet, R; Tressler, R E ^[1]

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1. Pennsylvania State Univ., University Park, PA (United States). Center for Advanced Materials

Tensile creep tests of single Si-C-O fibers were conducted in argon at 1300 C. and 300 to 700 MPa. Fibers exhibited only primary creep, where the creep strain e and creep time t could be empirically fitted by e = (1/[Beta]) in (1 + [Beta][dot e][sub 0]t). The fiber deformation was described by a rheological model for the viscous flow of a concentrated suspension. Under the test conditions, the microstructure of Nicalon was unstable, resulting in weight loss and SiC grain growth. This instability was attributed to the decomposition of the amorphous SiC[sub x]O[sub y] phase in the fiber, forming SiC and CO as products. As a result, the viscosity of the fiber increased because of an increase in the SiC volume fraction. The continuous increase in viscosity caused a continuously decreasing creep rate, which made steady-state creep impossible under these conditions. Because of the instability in the microstructure, the chemical environment was found to have a profound influence on the mechanical properties of Nicalon at elevated temperatures.

• OSTI ID: 5429508
• Journal Information: Journal of the American Ceramic Society; (United States), Journal Name: Journal of the American Ceramic Society; (United States) Vol. 76:12; ISSN 0002-7820; ISSN JACTAW
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360602* -- Other Materials-- Structure & Phase Studies
360603 -- Materials-- Properties
CARBIDES
CARBON COMPOUNDS
COMPOSITE MATERIALS
CREEP
MATERIALS
MATHEMATICAL MODELS
MECHANICAL PROPERTIES
MICROSTRUCTURE
SILICON CARBIDES
SILICON COMPOUNDS