X‐ray Diffraction Study of the Effect of High‐Temperature Heat Treatment on the Microstructural Stability of Third‐Generation SiC Fibers

Abstract

Third‐generation SiC fibers [High Nicalon S (HNS) and Tyranno SA3 (Ty–SA3)] were studied by X‐ray diffraction and transmission electron microscopy (TEM) after heat treatments in neutral atmosphere up to 1900°C. The microstructural changes in both materials were determined using a modified Hall–Williamson method introducing an anisotropy parameter taking into account the high density of planar defects. HNS fibers exhibit significant modifications in the coherent diffraction domains (CDD) size, which drastically increases from 24 to 70 nm in the range 1600°C–1900°C. TEM observations support these results. The residual microstrain values decrease from 0.0015 to 0.0005 between 1750°C and 1850°C. Similarly, the anisotropy parameter significantly decreases in the same temperature range. Concerning the Ty–SA3 fibers, no evolution in terms of CDD size and residual microstrain was observed. However, the anisotropy parameter decreases at 1800°C. TEM observations did not show noticeable grain growth. The grain size was found to be larger than the CDD and the planar defects density to decrease at high temperature. In both types of fibers, the CDD sizes are similar for the highest temperature heat treatments.

High dose neutron irradiation of Hi-Nicalon Type S silicon carbide composites, Part 1: Microstructural evaluations

“…The Hi-Nicalon Type S fiber is composed of SiC grains with some free carbon, generally containing a turbostratic texture, located between SiC grains [20]. Previous studies have shown that the fiber microstructures display virtually no evolution from temperature alone up to $1600°C.…”

A Review of SiC Fiber Oxidation with a New Study of Hi‐Nicalon SiC Fiber Oxidation

“…Hi-Nicalon (S) was developed to be a nearly stoichiometric and highly crystalline SiC fiber. [10,13,[20][21][22][23][24][25][26][27][28] One goal of this paper was to compile all of the oxidation kinetics results that exist to our knowledge in the literature to use as a resource for future SiC fiber oxidation testing and CMC oxidation modeling. [9,11] Several studies on the mechanical properties of SiC are available [12][13][14][15][16][17][18] including a review by Yun and DiCarlo.…”

Study of the Ion‐Irradiation Behavior of Advanced SiC Fibers by Raman Spectroscopy and Transmission Electron Microscopy

“…These values yield, respectively, 26 and 36 nm for the HNS fibers and 141 and 210 nm for the TSA3 fibers in agreement with Gosset et al . values …”

“…In this study, we focus on the irradiation behavior of SiC fibers that will be used as reinforcement of the composite, that is, Hi‐Nicalon type S (HNS) from Nippon Carbon Co. (Japan) and Tyranno SA3 (TSA3) from Ube Industries (Japan). These fibers consist of 3C–SiC grains with high stacking fault (SF) densities and small grain sizes . The aim of this work was to study the influence of their different microstructures on their ion‐irradiation behavior in comparison to SiC single crystals.…”