Low‐Temperature Oxidation Embrittlement of SiC (Nicalon <sup>™</sup> )/CAS Ceramic Matrix Composites
Why this work is in the frame
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Bibliographic record
Abstract
The influence of extended duration (up to 1000 h), low temperature oxidation heat‐treatments (375°–600°C) has been assessed using a model ceramic matrix composite system with a graphitic fiber/matrix interphase. For this study a Nicalon ™ fiber reinforced CaO–Al 2 O 3 –SiO 2 matrix composite was selected (Nicalon ™ /CAS), which possesses a thin (∼20–40 nm) carbon‐based interphase. Oxidation exposure has been conducted under both unloaded and static fatigue‐loaded conditions. For unstressed oxidation exposure, degradation of the carbon‐based interphase is apparent at temperatures as low as 375°C, after 1000 h exposure, resulting in a transition to a nominally brittle failure mode (i.e., negligible fiber pull‐out). The degree of mechanical property degradation increases with increasing temperature, such that strength degradation, and a transition to nominally brittle failure, is apparent after just 10 h at 600°C. Static fatigue loading between 450° and 600°C demonstrated generally similar trends, with reduced lifetimes being observed with increasing temperature. Based upon the unloaded oxidation experiments, combined with previously obtained intermediate and high‐temperature oxidation stability studies, a simple environmental embrittlement failure mechanism map is presented for Nicalon ™ /CAS. The implications of this study for advanced composite designs with multiple thin carbon‐based interphase layers are also discussed.
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Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.002 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.001 |
| Bibliometrics | 0.000 | 0.001 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from it