Bibliographic record
Abstract
RESUME Pour une large gamme d’applications en ingenierie, allant des materiaux de conversion de l’energie thermoelectrique aux materiaux d’interface thermique, la conductivite thermique dans les structures a l’echelle nanometrique fut un sujet interessant et important a la fois dans la recherche fondamentale et appliquee. La theorie classique de Fourier ne permet pas de d´ecrire la conduction thermique dans les materiaux nanostructures en raison de la negligence des evenements de la limite de diffusion qui jouent un role tres important dans les structures a l’echelle nanometrique. Le but ultime de ce travail est d’etablir un cadre general pour etudier la conductivite thermique dans les nanodispersions. Dans cette these, en passant en revue les principes de base du transport des phonons dans les nanostructures, les coefficients de conductivite thermique qui se posent dans la theorie de la chaleur macrosopique de Fourier sont modifies et rendus applicables pour les nanodispersions. Afin d’adapter la conductivite thermique macroscopique aux besoins de cette etude, l’influence de la limite de diffusion des phonons est prise en compte. La majorite des libres parcours moyens de la matrice et des particules dispersees fournis par la theorie cinetique sont modifies de facon a capturer les effets de la limite de diffusion. Un bon accord entre les predictions de nos modeles et les resultats experimentaux et numeriques disponibles a ete trouve. Notre analyse theorique permet de comprendre comment la taille des particules, la fraction volumique des particules dispersees, leur forme, les proprietes de l’interface particule-matrice, et l’agglomeration des particules influencent la conductivite thermique des nanodispersions. Nous etudions egalement les nanodispersions hybrides dans lesquelles les particules en suspension sont de differents types (par exemple, des nanofils et des nanospheres). Notre modele montre que la conductivite thermique augmente a mesure que la specularite de l’interface augmente. Pour la dispersion de particules anisotropes, l’influence de l’orientation des particules sur la conductivite thermique est mise en evidence.----------ABSTRACT For a wide range of engineering applications, ranging from thermoelectric energy conversion materials to thermal interface materials, the thermal conductivity in nanoscale structures has been an interesting and an important subject in both fundamental and applied research. The classical Fourier theory is not able to describe the heat conduction in nanostructured materials due to the neglect of boundary scattering events that play a very important role at nanoscale structures. The ultimate purpose of this work is to establish a general framework for studying the thermal conductivity in nanodispersions. In this dissertation, by reviewing the fundamentals of the phonon transport in nanostructures, the heat conductivity coefficients arising in macroscopic Fourier heat theory are modified and made applicable for nanodispersions. In order to adapt the macroscopic thermal conductivity for the purpose of this study, the influence of the phonon-boundary scattering is taken into account. The phonon mean free paths in both the matrix and the dispersed particles, that is provided by kinetic theory, are modified in a way to capture the boundary scattering effects. A good agreement between predictions of our models and available experimental and numerical results is found. Our theoretical analysis helps to understand how the particle size, the volume fraction of dispersed particles, their shape, the particle-matrix interface properties, and the particle agglomeration influence the thermal conductivity of nanodispersions. We also investigate hybrid nanodispersions in which the suspended particles of are of different types (for example nanowires and nanospheres). Our model shows that the thermal conductivity increases as the specularity of interface increases. For dispersion of anisotropic particles, the influence of particle orientation on the thermal conductivity is highlighted. When more nanoparticles are oriented in the direction of the heat flux, a higher thermal conductivity is expected due to smaller area on which the phonon-boundary scattering takes place.
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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) | 0.000 | 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) | 0.000 | 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 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".