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THERMAL TRANSPORT IN NANOSTRUCTURED ORGANIC-INORGANIC HYBRID MATERIALS

DOI: 10.1615/AnnualRevHeatTransfer.2016014222
pages 67-126

Wee-Liat Ong
Zhejiang University/University of Illinois at Urbana-Champaign Institute (ZJU-UIUC Institute)

Jonathan A. Malen
Department of Mechanical Engineering and Department of Materials Science and Engineering, Carnegie Mellon University, Pittsburgh, PA


KEY WORDS: phonon, thermal conductivity, thermal interface conductance, thermal interface resistance, nanocrystal, self assembled monolayer

Abstract

Nanostructured organic-inorganic hybrid materials hold promise as scalable materials with novel properties that emerge based on the choice of organic and inorganic constituents. These tunable materials have applications in electronics, optoelectronics, energy storage, and energy conversion, where heat is either a focal point in the design, or a parasitic byproduct of operation that must be effectively managed to optimize device performance. Herein, we review the theory and measurement of thermal transport in a wide range of organic-inorganic hybrid materials including single-molecule junctions, self-assembled monolayers, nanocrystal suspensions, nanocrystal arrays, polymer-nanostructure composites, and organic-inorganic molecular crystals. Experiments on self-assembled monolayers find that thermal interface conductance is dominated by phonons and limited by adhesion and vibrational alignment at the organic-inorganic interface. This finite thermal interface conductance bears on the thermal conductivity of nanostructured hybrid composite materials that have extensive internal interfaces. By comparison, little is known about thermal transport in hybrid molecular crystals−a relatively new class of materials that stems from the chemistry of organic and inorganic building blocks ~1 nm in size. Emergent superstructures are less aptly described as composites and instead as unique new crystals (e.g., organic-inorganic perovskites). To complement our review of experimental findings, we discuss theoretical findings and focus on analytical tools that offer a predictive capability for the intelligent design of new hybrid materials. In particular, we consider modified versions of the diffuse mismatch model for predicting thermal interface conductance and several effective medium approximations to predict the thermal conductivity of hybrid materials.

ARHT Digital Library

Illustration of composite TIMs with a percolation of spherical nanoparticles, and high aspect ratio nanowires. NANOSTRUCTURED THERMAL INTERFACES
Photograph of copper/diamond sintered wick structure. RECENT ADVANCES IN TWO-PHASE THERMAL GROUND PLANES
The microchannel with a single pillar used by Jung et al., and an SEM image of the pillar with a flow control slit at 180 deg (facing downstream). ADVANCED CHIP-LEVEL LIQUID HEAT EXCHANGERS
Schematics of thermal boundary conductance calculations. NONEQUILIRIUM MOLECULAR DYNAMICS METHODS FOR LATTICE HEAT CONDUCTION CALCULATIONS