Phonon Transport Analysis of Thermal Conductivity in Particulate Nanocomposites

Les modeles theoriques ont ete presentes pour la prediction de la conductivite thermique de composites constitues de particules spheriques. Parmi ces modeles, seuls quelques-uns d'entre eux sont en mesure de predire correctement la conductivite thermique de nanocomposites. La difficulte a modeliser correctement cette propriete physique origine de la difference entre la conductivite de la matrice et des particules a l'etat pur par rapport a leurs valeurs respectives dans le composite. En consequence, la resistance thermique a l'interface entre la matrice et les particules devient une variable importante de la conductivite thermique des materiaux nanocomposites. Dans ce projet, l'analyse de l'echange des phonons thermiques dans les milieux heterogenes est realisee et une formule generale de la conductivite thermique effective de nanocomposites est presentee. Dans la premiere etape du travail, le transport de phonons a l'interface entre la matrice et des nanoparticules est etudie. Cette investigation vise a presenter la resistance thermique sous une nouvelle forme. Les deux types de transport de phonons sur l'interface particule-matrice, soient diffus et speculaire, sont pris en compte dans le calcul de la conductivite thermique effective pour les nanocomposites particulaires. Dans un deuxieme temps, le modele propose est evalue en regard de resultats numeriques et experimentaux disponibles dans la litterature. Cette evaluation tend a prouver que le modele propose est capable de predire la conductivite thermique effective pour un large eventail de fractions volumiques et de tailles de particules. ---------- Theoretical models have been presented for predicting the thermal conductivity of composites consisting of spherical particles. Among these models, only a few of them are able to predict the thermal conductivity of nanocomposites. This is because the matrix and particle thermal conductivities in nanocomposites are not equal to their bulk values due to increased interface scattering. The boundary scattering becomes important when the characteristic length of the media is smaller than the bulk mean free path of phonons. The thermal boundary resistance at the interface between matrix and suspended particles is affected on the thermal conductivity of nanocomposites. In this work, the phonon viewpoint of heat transport in heterogeneous media is investigated and a general formula for the effective thermal conductivity of particulate nanocomposites is presented. In the first step of this project, the phonon scattering at the interface between matrix and nanoparticles is investigated. This study aims to present the thermal boundary resistance in a new form. Both diffuse and specular types of scattering of phonons on the particle-matrix interface are taken into account in the derivation of the effective thermal conductivity for the particulate nanocomposites. In the next step, the proposed model is evaluated with numerical and experimental results available in literature. This evaluation is done to prove that the proposed model is able to predict the effective thermal conductivity in a wide