A diverse spectrum of technology drivers such as improved thermal barriers, higher efficiency thermoelectric energy conversion, phase-change memory, heat-assisted magnetic recording, thermal management of nanoscale electronics, and nanoparticles for thermal medical therapies are motivating studies of the applied physics of thermal transport at the nanoscale. This review emphasizes developments in experiment, theory, and computation in the past ten years and summarizes the present status of the field. Interfaces become increasingly important on small length scales. Research during the past decade has extended studies of interfaces between simple metals and inorganic crystals to interfaces with molecular materials and liquids with systematic control of interface chemistry and physics. At separations on the order of ∼1 nm, the science of radiative transport through nanoscale gaps overlaps with thermal conduction by the coupling of electronic and vibrational excitations across weakly bonded or rough interface...

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Nanoscale thermal transport. II. 2003–2012

Emerging challenges and materials for thermal management of electronics

The extremely high thermal conductivities of carbon nanotubes have motivated a wealth of research. Progress includes innovative conduction metrology based on microfabricated platforms and scanning thermal probes as well as simulations exploring phonon dispersion and scattering using both transport theory and molecular dynamics. This article highlights these advancements as part of a detailed review of heat conduction research on both individual carbon nanotubes and nanostructured films consisting of arrays of nanotubes or disordered nanotube mats. Nanotube length, diameter, and chirality strongly influence the thermal conductivities of individual nanotubes and the transition from primarily diffusive to ballistic heat transport with decreasing temperature. A key experimental challenge, for both individual nanotubes and aligned films, is the separation of intrinsic and contact resistances. Molecular dynamics simulations have studied the impacts of specific types of imperfections on the nanotube conductance and its variation with length and chirality. While the properties of aligned films fall short of predictions based on individual nanotube data, improvements in surface engagement and postfabrication nanotube quality are promising for a variety of applications including mechanically compliant thermal contacts.

http://nanoheat.stanford.edu/sites/default/files/publications/RevModPhys%20Marconnet%20et%20al..pdf

Thermal conduction phenomena in carbon nanotubes and related nanostructured materials

Thermal transport in polymeric materials and across composite interfaces

Membrane fouling, which arises from the nonspecific interaction between the membrane surface and foulants, significantly impedes the efficient application of membrane technology. Antifouling and antimicrobial materials are important classes of functional materials for the surface modification of reverse osmosis and nanofiltration membranes. Applications of various organic and inorganic materials having different characteristics such as size, surface charge, hydrophilicity, functionality and biocidal activity, provide protective/sacrificial layers to the membrane surface against different foulants and microorganisms. This review summarizes the properties and applications of organic and inorganic materials, antifouling mechanisms, and surface modification of pre-formed membranes. Materials such as zwitterionic polymers, neutral polymers, polyelectrolytes, amphiphilic polymers, quaternary ammonium polymers, biopolymers, hydrophilic polymers, polydopamine, inorganic salts, and nanomaterials have shown great potential in reducing foulant adhesion and/or proliferative microbial growth on membrane surfaces.

Antifouling, fouling release and antimicrobial materials for surface modification of reverse osmosis and nanofiltration membranes

Dynamics of water and solute transport in polymeric reverse osmosis membranes via molecular dynamics simulations

We use nonequilibrium molecular dynamics to study heat transfer across structures consisting of a few layers of graphene sandwiched between silicon crystals. We find that when heat transfers from a silicon lead on one side across the graphene layers to a silicon lead on the other side, the interfacial conductance is essentially independent of the number of layers, in agreement with recent experimental findings. By contrast, wave-packet simulations show that the transmission coefficient of individual vibrational modes depends strongly on frequency and the number of graphene layers, indicating significant interference effects. This apparent contradiction is resolved by a theoretical calculation, which shows that the integrated contribution of the phonons to the interfacial thermal conductance is essentially independent of the number of layers. When one atomic layer of graphene is heated directly, the effective interfacial conductance associated with heat dissipation to the silicon substrate is much smaller. We attribute this to the resistance associated with heat transfer between high and low frequency modes within heated graphene.

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Heat transfer mechanism across few-layer graphene by molecular dynamics

Stiffness of interfacial bonding between two materials plays a major role in controlling the thermal conductance of the interface. We use nonequilibrium molecular dynamics simulations to study interfacial thermal conductance at an epitaxial interface between two fcc crystals with interatomic interactions described by Lennard Jones (LJ) potentials. The interface stiffness was varied by two different methods: (i) application of pressure and (ii) direct change of the interfacial bonding strength by varying the depth of potential well parameter of the LJ potential. Our results show that when the interfacial bonding strength is low, interfacial stiffness increases linearly with pressure due to the anharmonicity of atomic interactions. Consequently, the interfacial conductance increases, first proportionally to interfacial stiffness, and then it saturates at a high value. Quantitatively similar behavior is observed when the stiffness of the interfacial bonding is increased by directly varying the depth of the potential well parameter of the LJ potential. By contrast, when the interfacial bonding strength is high, thermal conductance is almost pressure independent and in fact slightly decreases with increasing pressure. This decrease can be explained by the change of overlap between the vibrational density of states (DOS) in the two crystalline materials.

Bonding and pressure-tunable interfacial thermal conductance

We use molecular dynamics simulations to compute junction thermal conductance of carbon nanotubes as a function of crossing angle and pressure, and conductivity of arrays and bundles consisting of multiple junctions as a function of pressure. Two types of arrays are investigated: crossbar structures consisting of alternating orthogonal layers of nanotubes and close-packed bundles of parallel oriented tubes. Conductance of 90° junction increases with pressure 4 fold before saturation; cross-plane thermal conductivity of crossbar structures increases by a factor of 2. For parallel junctions pressure doubles the conductance while thermal conductivity of nanotubes bundles is more or less pressure independent.

Meng Shen

Papers

Dynamics of water and solute transport in polymeric reverse osmosis membranes via molecular dynamics simulations

Heat transfer mechanism across few-layer graphene by molecular dynamics

Bonding and pressure-tunable interfacial thermal conductance

Inter-tube thermal conductance in carbon nanotubes arrays and bundles: Effects of contact area and pressure

Rejection mechanisms for contaminants in polyamide reverse osmosis membranes