Global analysis of the assembly of Fe2VAl and metal electrode through the study of the bonding process conditions.
Bibliographic record
Abstract
Fe2VAl-based thermoelectric modules are very promising for large scale applications such as industrial energy harvesting since its constituent materials are abundant, non-toxic and low cost. However, the assembly of modules based on Fe2VAl compounds requires to properly bond this thermoelectric material to high electrical conductivity material such as copper. Furthermore, the assembly must remain efficient in the entire range of temperature at which Fe2VAl compounds show interesting thermoelectric properties, which means from 300K to 700K. At these temperatures, thermal ageing may induce significant modification of the microstructure at the interface between thermoelectric material and electrical conductor. Moreover, copper is known to show poor oxidation resistance above 500K in atmospheric conditions and replacement by pure nickel or nickel-plated copper should be considered [1]. To understand the influence of the bonding process on the property of the assembly, we propose a global analysis based on characterization of the interface microstructure, measurements of surface contact resistance and Seebeck coefficient of a junction as well as the assessment of the effect of thermal ageing [2]. We tested a panel of joining technologies and discriminated some processes based on the global analysis. The most promising technique is the use of a high temperature (1000K) silver-based brazing compound under high vacuum condition (10-4 mbar). This process leads to low surface contact resistance (<10μΩ∙cm2), the appearance of a thin reactive layer at the interface, a weak change on the Seebeck coefficient and no major degradation of the assembly properties after heat treatment. Furthermore, those results were obtained for all three of copper, nickel-plated copper and nickel electrodes. Finally, this bonding process has been upscaled to manufacture a complete thermoelectric module with 36 thermoelectric legs and 37 electrodes in an induction vacuum furnace. [1] ANIEKWE, U. V. et UTIGARD, T. A. High-temperature oxidation of nickel-plated copper vs pure copper. Canadian metallurgical quarterly, 1999, vol. 38, no 4, p. 277-281. [2] ROY, G. et al. Global Analysis of Influence of Contacts on Heusler-Based Thermoelectric Modules. Journal of Electronic Materials, 2019, p. 1-13.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.001 |
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 source (direct Gemma or distilled Codex), 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".