Role of four-phonon processes in thermal conductivity of two-dimensional materials and thermal-transport enhancement arising from interconnected nanofiller networks in polymer/nanofiller composites.

Recent research has shed light on the importance of four-phonon scattering processes in the thermal conductivity () of 2D materials. The inclusion of 4 phonon scattering processes from first-principles has been shown to lead to a thermal conductivity of ∼1290 W m K in graphene at 300 K, significantly lower than the values predicted to be in excess of 4000 W m K based only on 3 phonon scattering processes. Four phonon processes are shown to be most significant for flexural ZA phonon modes, where the reflection symmetry selection rule (RSSR) is less restrictive for 4-phonon than 3-phonon scattering processes.

Length dependence thermal conductivity of zinc selenide (ZnSe) and zinc telluride (ZnTe) - a combined first principles and frequency domain thermoreflectance (FDTR) study.

In this study, we report the length dependence of thermal conductivity () of zinc blende-structured Zinc Selenide (ZnSe) and Zinc Telluride (ZnTe) for length scales between 10 nm and 10 μm using first-principles computations, based on density-functional theory. The value of ZnSe is computed to decrease significantly from 22.9 W m K to 1.

Large Enhancement in Thermal Conductivity of Solvent-Cast Expanded Graphite/Polyetherimide Composites.

We demonstrate in this work that expanded graphite (EG) can lead to a very large enhancement in thermal conductivity of polyetherimide-graphene and epoxy-graphene nanocomposites prepared via solvent casting technique. A value of 6.6 W⋅m⋅K is achieved for 10 wt% composition sample, representing an enhancement of ~2770% over pristine polyetherimide (~0.

The superior effect of edge functionalization relative to basal plane functionalization of graphene in enhancing the thermal conductivity of polymer-graphene nanocomposites - a combined molecular dynamics and Green's functions study.

To achieve polymer-graphene nanocomposites with high thermal conductivity (), it is critically important to achieve efficient thermal coupling between graphene and the surrounding polymer matrix through effective functionalization schemes. In this work, we demonstrate that edge-functionalization of graphene nanoplatelets (GnPs) can enable a larger enhancement of effective thermal conductivity in polymer-graphene nanocomposites relative to basal plane functionalization. Effective thermal conductivity for the edge case is predicted, through molecular dynamics simulations, to be up to 48% higher relative to basal plane bonding for 35 wt% graphene loading with 10 layer thick nanoplatelets.

Thermal conductivity of hexagonal BCP - a first-principles study.

In this work, we report a high thermal conductivity () of 162 W m K and 52 W m K at room temperature, along the directions perpendicular and parallel to the -axis, respectively, of bulk hexagonal BCP (h-BCP), using first-principles calculations. We systematically investigate elastic constants, phonon group velocities, phonon linewidths and mode thermal conductivity contributions of transverse acoustic (TA), longitudinal acoustic (LA) and optical phonons. Interestingly, optical phonons are found to make a large contribution of 30.

Effect of Alignment on Enhancement of Thermal Conductivity of Polyethylene-Graphene Nanocomposites and Comparison with Effective Medium Theory.

Thermal conductivity () of polymers is usually limited to low values of ~0.5 W in comparison to metals (>20 W). The goal of this work is to enhance thermal conductivity () of polyethylene-graphene nanocomposites through simultaneous alignment of polyethylene (PE) lamellae and graphene nanoplatelets (GnP).