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Thermal Percolation in Well-Defined Nanocomposite Thin Films
Boyce S Chang1, Chen Li2, Jinghang Dai2
1Department of Materials Science and Engineering, University of California, Berkeley, Berkeley, California 94720, United States.
ACS Applied Materials & Interfaces
|March 21, 2022
Summary
Thermal percolation in polymer nanocomposites was achieved using spherical, nonconductive nanoparticles. This study demonstrates controlled nanoparticle assembly enables efficient thermal transport at low filler loadings, overcoming previous limitations.
Area of Science:
- Materials Science
- Polymer Science
- Nanotechnology
Background:
- Thermal percolation, a rapid increase in thermal transport via filler networks, is crucial for thermal management in polymer nanocomposites.
- Achieving thermal percolation typically requires high-aspect-ratio, conductive fillers at high loadings, posing experimental and modeling challenges.
- The low thermal conductivity contrast ratio between fillers and matrix, and undefined network structures, complicate thermal percolation in randomly dispersed composites.
Purpose of the Study:
- To demonstrate thermal percolation in polymer nanocomposites using spherical, nonconductive nanoparticles with controlled arrangement.
- To elucidate structure-property relationships in nanocomposites by controlling nanofiller placement (1,2,3-dimension arrangement).
- To investigate the influence of volume fraction, interfacial thermal resistance, and filler conductivity on thermal conductivity, departing from effective medium approximations.
Main Methods:
- Fabrication of self-assembled polymer nanocomposites with controlled nanoparticle arrangements.
- Utilizing spherical, nonconductive nanoparticles with a thermal conductivity contrast ratio (k_f/k_m) of approximately 60.
- Experimental characterization of thermal transport properties at a low filler volume fraction (9 vol %).
Main Results:
- Demonstrated successful thermal percolation with spherical, nonconductive fillers at a low volume fraction (9 vol %).
- Observed deviations from effective medium approximations regarding volume fraction, interfacial thermal resistance, and filler conductivity effects.
- Established that the contrast ratio plays a minor role in thermal percolation for ratios above approximately 60, common for semiconducting nanoparticles in polymers.
Conclusions:
- Controlled nanofiller assembly enables thermal percolation even with spherical, nonconductive fillers, challenging previous assumptions.
- The findings provide new insights into thermal percolation, establishing new limits for contrast ratio, interfacial thermal conductance, and filler size.
- This work opens avenues for designing advanced polymer nanocomposites for efficient thermal management applications.
