Effect of hybrid nanofillers on thermal conductivity of composite phase change materials

In order to study the effect of hybrid nanofillers on the thermal conductivity of composite phase change materials(PCMs), organic composite PCMs filled with carbon nanotubes and silver (or alumina) nanoparticles as binary nanofillers were prepared. The effective thermal conductivity of the samples in solid phase was measured using the transient plane source technique at room temperature. The influence of the total loading, ratio of carbon nanotubes to nanoparticles, and base PCMs on the effective thermal conductivity of the composite PCMs were investigated experimentally. It was shown that the carbon nanotubes and nanoparticles act against each other. The thermal conductivity enhancement of the composite PCMs due to the presence of hybrid nanofillers is even lower than that with pure carbon nanotubes or nanoparticles. The relatively low total loadings (up to 1.5 vol%) of the nanofillers are not sufficient to lead to formation of effective heat conduction networks. This was confirmed by the microscopic images taken on the dispersion of nanofillers. Despite the existence of fairly uniform dispersion of the hybrid nanofillers, the desired synergetic effect between the dissimilar nanofillers is absent as a result of both the difference in their heat conduction mechanisms and the relatively high thermal interface resistance. The unfavorable effect occurs instead when the heat conduction paths are blocked within each type of nanofillers. ©, 2015, Zhejiang University. All right reserved.