Accurate determination of anisotropic thermal conductivity for ultrathin composite film

Abstract

Highly anisotropic thermal conductive materials are of great values in thermal management applications. However, accurate determination of ultrathin composite thermal properties is a daunting task, due to the tiny thermal conductance, severely hindering the further exploration of novel efficient thermal management materials, especially for size-confined environments. In this work, by utilizing a hybrid measuring method, we demonstrate an accurate determination of thermal properties for montmorillonite/reduced graphene oxide (MMT/rGO) composite film with thickness range of 0.2 to 2 μm. The in-plane thermal conductivity measurement is realized by one-dimensional steady-state heat conduction approach while the cross-plane one is achieved via a modified 3ω method. As-measured thermal conductivity results are cross-checked with different methods and known materials, revealing the high measurement accuracy. A high anisotropic ratio of 60.5, independent of composite thickness, is observed in our measurements, further ensuring the negligible measurement error. Notably, our work develops an effective approach for ultrathin composite thermal conductivity determination, which may promote the evolution of ultrathin composites for potential thermal-related applications.

Unraveling the Impact of Boron Nitride and Silicon Nitride Nanoparticles on Thermoplastic Polyurethane Fibers and Mats for Advanced Heat Management

“…Particularly for the electrospun composites, high porosity, up to 90%, and anisotropic thermal conductivity further complicate the thermal conductivity measurements. 75,76 This underscores the imperative for further research to develop more reliable and accurate methods for measuring the thermal conductivity of the electrospun mats.…”

“…On the other hand, issues such as reaching thermal equilibrium in a short time, laser penetration depth comparable to the film’s thickness, and the need to coat the sample with a conductive layer increase the errors for thermal conductivity measurements of thin films by LFA. Particularly for the electrospun composites, high porosity, up to 90%, and anisotropic thermal conductivity further complicate the thermal conductivity measurements. , This underscores the imperative for further research to develop more reliable and accurate methods for measuring the thermal conductivity of the electrospun mats.…”

Bridging a Gap in Thermal Conductivity and Heat Transfer in Hybrid Fibers and Yarns via Polyimide and Silicon Nitride Composites

“…Problems such as reaching a thermal equilibrium state in a short time, laser penetration depth close to the film's thickness, direct contact of the film and the sample holder, and large thermal contact resistance between the heating source and the thin film are the main reasons that increase the measurement error for very thin films. [39,40] Besides, the measurement error is even higher for electrospun membranes due to their high porosity and high anisotropic thermal conductivity, especially with thermally conductive fillers. Another disadvantage is the necessity of usually applying carbon-based coating on the polymer membranes that, in the case of thin samples, artificially increases the measured thermal conductivity values.…”