Thermal transport across grain boundaries in polycrystalline silicene: a multiscale modeling

During the fabrication process of large scale silicene through common chemical vapor deposition (CVD) technique, polycrystalline films are quite likely to be produced, and the existence of Kapitza thermal resistance along grain boundaries could result in substantial changes of their thermal properties. In the present study, the thermal transport along polycrystalline silicene was evaluated by performing a multiscale method. Non-equilibrium molecular dynamics simulations (NEMD) was carried out to assess the interfacial thermal resistance of various constructed grain boundaries in silicene as well as to examine the effects of tensile strain and the mean temperature on the interfacial thermal resistance. In the following stage, the effective thermal conductivity of polycrystalline silicene was investigated considering the effects of grain size and tensile strain. Our results indicate that the average values of Kapitza conductance at grain boundaries at room temperature were estimated nearly 2.56*10^9 W/m2K and 2.46*10^9 W/m2K through utilizing Tersoff and Stillinger-Weber interatomic potentials, respectively. Also, in spite of the mean temperature whose increment does not change Kapitza resistance, the interfacial thermal resistance can be controlled by applying strain. Furthermore, it was found that, by tuning the grain size of polycrystalline silicene, its thermal conductivity can be modulated up to one order of magnitude.Comment: 24 pages, 11 figure

Graphene Helicoid: The Distinct Properties Promote Application of Graphene Related Materials in Thermal Management

The extremely high thermal conductivity of graphene has received great attention both in experiments and calculations. Obviously, new feature in thermal properties is of primary importance for application of graphene-based materials in thermal management in nanoscale. Here, we studied the thermal conductivity of graphene helicoid, a newly reported graphene-related nanostructure, using molecular dynamics simulation. Interestingly, in contrast to the converged cross-plane thermal conductivity in multi-layer graphene, axial thermal conductivity of graphene helicoid keeps increasing with thickness with a power law scaling relationship, which is a consequence of the divergent in-plane thermal conductivity of two-dimensional graphene. Moreover, the large overlap between adjacent layers in graphene helicoid also promotes higher thermal conductivity than multi-layer graphene. Furthermore, in the small strain regime (< 10%), compressive strain can effectively increase the thermal conductivity of graphene helicoid, while in the ultra large strain regime (~100% to 500%), tensile strain does not decrease the heat current, unlike that in generic solid-state materials. Our results reveal that the divergence in thermal conductivity, associated with the anomalous strain dependence and the unique structural flexibility, make graphene helicoid a new platform for studying fascinating phenomena of key relevance to the scientific understanding and technological applications of graphene-related materials.Comment: 7 figure

Thermal Properties of Graphene, Carbon Nanotubes and Nanostructured Carbon Materials

Recent years witnessed a rapid growth of interest of scientific and engineering communities to thermal properties of materials. Carbon allotropes and derivatives occupy a unique place in terms of their ability to conduct heat. The room-temperature thermal conductivity of carbon materials span an extraordinary large range - of over five orders of magnitude - from the lowest in amorphous carbons to the highest in graphene and carbon nanotubes. I review thermal and thermoelectric properties of carbon materials focusing on recent results for graphene, carbon nanotubes and nanostructured carbon materials with different degrees of disorder. A special attention is given to the unusual size dependence of heat conduction in two-dimensional crystals and, specifically, in graphene. I also describe prospects of applications of graphene and carbon materials for thermal management of electronics.Comment: Review Paper; 37 manuscript pages; 4 figures and 2 boxe