Effective Thermal Properties and Thermal Boundary Resistances of Multiphase Composites Containing Carbon Nanotubes and Inorganic Nanoparticles

Monte Carlo simulations were employed to investigate the effective thermal conductivity ($K_{\mathrm{eff}}$) and thermal boundary resistances ($R_{\mathrm{bd}}$) of polymer composites containing carbon nanotubes (CNTs) and inorganic nanoparticles. By considering $R_{\mathrm{bd}}$ between any two phases and the synergistic effect of CNTs and nanoparticles, our model more accurately predicted$K_{\mathrm{eff}}$ of 3-phase composites than effective medium theories (EMTs). Complex morphology of CNTs (diameter, length) and the heat transfer at interfaces ($R_{\mathrm{bd}}$) were quantified to study their influences on $K_{\mathrm{eff}} $. By matching the simulated $K_{\mathrm{eff}}$ with the measured $K_{\mathrm{eff}}$, $R_{\mathrm{bd}}$ of polymer-CNT and polymer-nanoparticle could be estimated. The results showed that $K_{\mathrm{eff}}$ of composites increases when CNT fraction increases and when $R_{\mathrm{bd}}$ of polymer-nanofillers (CNTs and nanoparticles) decreases. CNT bundle was built to investigate its effect on $K_{\mathrm{eff}}$ of composites, which had not been considered in EMTs. It was found that when CNT bundles increase, $K_{\mathrm{eff}}$ decreases in the composites with random and parallel CNTs, whereas, $K_{\mathrm{eff}}$ increases in those with perpendicular CNTs.