Premium
Oxidation kinetics strength of Hi‐Nicalon TM ‐S SiC fiber after oxidation in dry and wet air
Author(s) -
Hay Randall S.,
Chater Richard J.
Publication year - 2017
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/jace.14833
Subject(s) - crystallization , materials science , kinetics , fiber , crystal (programming language) , impurity , composite material , chemical engineering , mineralogy , analytical chemistry (journal) , chemistry , physics , organic chemistry , quantum mechanics , computer science , engineering , programming language , chromatography
Hi‐Nicalon™‐S SiC fiber strengths and Weibull moduli were measured after oxidation for up to 100 hours between 700°C and 1400°C in wet and dry air. SiO 2 scale thickness and crystallization extent were measured by TEM . The effect of furnace environment on trace element levels in the SiO 2 scales was characterized by secondary ion mass spectroscopy. Crystallization kinetics and D eal‐ G rove oxidation kinetics for glass and crystalline scale, and the transition between them, were modeled and determined. Crystallization retards oxidation kinetics, and scale that formed in the crystalline state was heavily deformed by the growth stress accompanying SiC oxidation volume expansion. Glass scales formed in dry air slightly increased fiber strength. Glass scales formed in wet air did not increase strength, and in some cases significantly decreased strength. Scales more than 200 nm thick were usually partially or completely crystallized, which degraded fiber strength. Contamination of scales by trace impurities such as Al and Ca during heat treatment inhibited crystallization. The oxidation kinetics and the strengths of oxidized Hi‐Nicalon™‐S fibers are compared with previous studies on SiC fibers, bulk SiC , and single‐crystal SiC . Empirical relationships between oxidation temperature, time, scale thickness, and strength are determined and discussed.