Effect of volume-fraction dependent agglomeration of nanoparticles on the thermal conductivity of nanocomposites: Applications to epoxy resins, filled by SiO2, AlN and MgO nanoparticles

A thermodynamic model for transient heat conduction in ceramic-polymer nanocomposites is proposed. The model takes into account particle's size, particle's volume fraction, and interface characteristics with emphasis on the effect of agglomeration of particles on the effective thermal conductivity of the nanocomposite. The originality of the present work is its basement on extended irreversible thermodynamics, combining nano- and continuum-scales without invoking molecular dynamics. The model is compared to experimental data using the examples of SiO2, AlN and MgO nanoparticles embedded in epoxy resin. The analysis is limited to spherical nanoparticles. The dependence of the degree of agglomeration with respect of the volume fraction of particles is also discussed and a power-law relation is established through a kinetic mechanism and experiments performed in our laboratory. This relation is used in our theoretical model, resulting into a good agreement with experiments. It is shown that the effective thermal conductivity may either increase or decrease with the degree of agglomeration.