Imaging of Thermal Propagation in Combustion of Al/CuO Core-Shell Nanothermite Film
Notice bibliographique
Résumé
Nanoenergetics have been a topic of great discussion over the past few decades due to their extraordinary combustive properties. In particular, heavy investment has been put into researching nanothermites due to the low cost of their components and high energy release of the products. However, much is still unknown about the kinetics and thermodynamics of nanothermites on both the spatial and temporal micro-scale. Here, we report the design and implementation of a high-speed thermographic facility ("pyrometry setup") as well as the investigation of the combustion mechanism and flame propagation of Al/CuO nanothermite films at such scales using an alternate high-speed thermography (3.75 µm/px, 2.5 ms resolution) and videography (2.8 µm/px, 50 µs resolution) system. Sub-millimeter films of both Physically-Mixed (PM) and Core-Shell (CS) Al/CuO nanothermite were fabricated and subsequently ignited by hot wire, and the combustion event was recorded onto footage. This work demonstrates the differences between the combustion of PM and CS films with respect to temperature, flame propagation, and particle ejection. Discussions have been made on the so-called "reactive sintering" mechanism — in which reacting particles amalgamate before burning — and its effects on micro-scale combustion behavior. It has been shown that the self-contained nature of the CS film promotes spatio-thermometric uniformity within the pre-combusted regions of the film (uniform temperature banding), whereas the PM film exhibits irregularities within those regions as well as notable "hot spots" along the flame front. Additionally, the flame propagation from the CS film has been recorded to be faster than that of the PM film by a factor of 1.4 (~10.80 vs. ~7.44 cm/s, respectively), which may bear a relationship with the particle ejection seen in both samples. In the CS film, it is revealed to be more akin to a particle "exhaust" rather than an "ejection" of aggregated particles as displayed by the PM film (presumably caused by the hot spots), resulting in a hotter post-combustion region of space. This suggests that for CS films, the energy from the reaction remains relatively local to the reaction zone rather than being carried away by distantly ejected particles. Temperature measurements using an emissivity correction value of 0.15 indicate that the maximum temperature along the flame front for the PM film is ~3400 K and the distance ("conduction distance") between that and the unburned film (room temperature) is ~645 µm, giving an average spatial temperature gradient of 4.8 K/µm . For the CS film, the maximum temperature and conduction distance were found to be ~2500 K and ~600 µm, respectively, giving an average spatial temperature gradient of 3.7 K/µm.
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Comment cette classification a été obtenuedéplier
Prédiction machine sur la base complète
Imitation des enseignantsNi prévalence calibrée, ni vérité terrain. Validation humaine à venir. Le volet Gemma est une étiquette directe du modèle pour chaque travail de la base, lue sur la notice réduite au titre. Le volet Codex est un classifieur appris des 10 348 étiquettes directes de Codex et calibré sur les taux pondérés de l'échantillon; les champs sans appui suffisant ne portent aucun appel Codex. Le mode candidate est l'union des deux volets; le consensus est leur intersection. Ces sorties portent le statut machine_predicted_unvalidated et ne sont pas des étiquettes humaines.
Scores du classifieur distillé par catégorie (deux têtes)
| Catégorie | Codex | Gemma |
|---|---|---|
| Métarecherche | 0,000 | 0,000 |
| Méta-épidémiologie (sens strict) | 0,000 | 0,000 |
| Méta-épidémiologie (sens large) | 0,000 | 0,000 |
| Bibliométrie | 0,000 | 0,000 |
| Études des sciences et des technologies | 0,000 | 0,000 |
| Communication savante | 0,000 | 0,000 |
| Science ouverte | 0,000 | 0,000 |
| Intégrité de la recherche | 0,000 | 0,000 |
| Charge utile insuffisante (le modèle a refusé de juger) | 0,001 | 0,000 |
Scores machine (provisoires)
Les deux têtes enseignantes du modèle étudiant, lues sur ce travail. Un score ordonne la base pour la relecture; il n'affirme jamais une catégorie, et le statut de validation accompagne chaque rangée tel quel.
Scores de référence d'un modèle non mature (critères de maturité non atteints, 7 itérations). Un score ordonne; il n'affirme jamais une catégorie.
score_only:v0-immature-baseline · tel quel depuis la passe de notation : score_only signifie que le nombre peut ordonner les travaux, et qu'aucune étiquette de catégorie n'en découleClassification
machine, non validéePrédiction automatique; un appel candidat d’une seule source (Gemma direct ou Codex distillé), pas un consensus.
Le détail, modèle par modèle et score par score, se trouve en fin de page sous « Comment cette classification a été obtenue ».