Mullite Whisker Reinforced Zirconia Toughened Alumina for High Temperature Applications
Bibliographic record
Abstract
Particulate enhanced oxide ceramics are an attractive class of materials for high temperature applications because they possess many of the high temperature capabilities of monolithic ceramics but also have enhanced mechanical properties due to their multi-phase structure. High temperature structural ceramics have the potential to operate above at higher temperatures than current super alloys; however, processing costs and lack of reliability has prevented their commercialization. In this work a particulate reinforced ceramic composed entirely of oxides is proposed as a more oxidation resistant and cost effective structural ceramic which will have potentially improved resistance to environmental degradation. Zirconia Toughened Alumina (ZTA), as the matrix, has enhanced toughness, strength, and creep resistance over single phase alumina or zirconia. ZTA can further be strengthened by the incorporation of SiC type whiskers; however, these whiskers are prone to deterioration at temperatures above 1000°C through oxidation. In this work Mullite, in whisker form, is proposed as the reinforcement to ZTA due to its stability in oxidizing atmospheres at high temperatures. Mullite whiskers are grown through the molten salt method and incorporated into the ZTA matrix using a colloidal processing route in this study. The composition of the ZTA matrix is 15wt% Yttria stabilized Zirconia (YSZ), 85 wt% α-Alumina. The Mullite whiskers make up 20 vol% of the composite, yielding a final composition of 71.6 wt% Alumina, 12.7 wt% YSZ, and 15.6 wt% Mullite. The green compacts are fired in a two stage sintering process incorporating atmospheric pressure sintering to 92% density (seal the pore channels) and then hot isostatic pressure pressing (HIP) to increase the density. Samples have been tested for room temperature flexural strength using a three point bend test and fracture toughness through Gong’s Vickers indentation method. The results of microstructure study and mechanical tests are reported in this paper.
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How this classification was reachedexpand
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 | 0.001 | 0.000 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.001 | 0.000 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 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 itClassification
machine, unvalidatedMachine predicted; a candidate call from one teacher head, not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".