Thermal transport in 2-and 3-dimensional periodic “holey” nanostructures (original) (raw)
Related papers
Thermal transport in nanostructures
AIP Advances, 2012
This review summarizes recent studies of thermal transport in nanoscaled semiconductors. Different from bulk materials, new physics and novel thermal properties arise in low dimensional nanostructures, such as the abnormal heat conduction, the size dependence of thermal conductivity, phonon boundary/edge scatterings. It is also demonstrated that phonons transport super-diffusively in low dimensional structures, in other words, Fourier's law is not applicable. Based on manipulating phonons, we also discuss envisioned applications of nanostructures in a broad area, ranging from thermoelectrics, heat dissipation to phononic devices.
Anomalous Thermal Transport in Nanostructures
Fluctuation Relations and Beyond, 2013
Thermal transport in nanoscale structures has attracted an increasing attention in last two decades. Here we give a brief review of the recent developments in experimental and theoretical studies of heat transport in nano materials such as nanotube and nanowire. In particular, we will demonstrate that the phonons in nanotube and nanowires transport super-diffusively, which leads to a length dependent thermal conductivity. In other words, heat conduction in low dimensional nanostructures does not obey the Fourier's law.
Thermal Conductivity of a Nano-Structured Material
2005
In this paper, the phonon Boltzmann equation is solved numerically to study the phonon thermal conductivity of nano-structured thin films opened a nano-hole in a host material. We focused on effects of hole size on the reduction of thermal conductivity. The simulation shows that the temperature profiles in nano-structures are very different from those in conventional bulk materials, due to ballistic phonon transport at nanoscale. The conventional heat conduction equations cannot be applied to solve the heat transfer in solids at nanoscale. The effective thermal conductivity of nano-structures are calculated from temperature gradient. We predict the thermal conductivity dependence on the size of a nano-hole. At constant thin film thickness the larger the hole size, the smaller is the thermal conductivity of two-dimensional nano-structured thin film. The results of this study can be used to the development of thermal management of heat conduction by using artificial physical property.
Thermal Conductivity of Nanoscale Materials: A Review
Journal of Ultra Scientist of Physical Sciences Section B, 2017
Nanoscale materials are being widely used in science and technology. Rapid development in synthesis and fabrication of Nanoscale materials has created a great demand for scientific understanding of thermal conductivity in nanoscale materials. The thermal conductivity in low dimensional has been obtained by using different theoretical and numerical approaches. The low dimensional structures such as quantum well, wires and dots confined in extremely small region and have novel transport properties. Measurement methods e.g. reducing grain size, multiple Phonon scattering, BTE in 2D nanoribbons, source of coherent Phonons etc open new way for nanoscale thermal transport study. This review summarizes the development in experiments, theory and computation that have occurred in thermal transport of nanoscale materials.
Phonon transport and thermal conductivity in two-dimensional materials
Annual Review of Heat Transfer, 2016
Two-dimensional materials, such as graphene, boron nitride and transition metal dichalcogenides, have attracted increased interest due to their potential applications in electronics and optoelectronics. Thermal transport in two-dimensional materials could be quite different from three-dimensional bulk materials. This article reviews the progress on experimental measurements and theoretical modeling of phonon transport and thermal conductivity in two-dimensional materials. We focus our review on a few typical two-dimensional materials, including graphene, boron nitride, silicene, transition metal dichalcogenides, and black phosphorus. The effects of different physical factors, such as sample size, strain and defects, on thermal transport in Twodimensional materials are summarized. We also discuss the environmental effect on the thermal transport of two-dimensional materials, such as substrate and when two-dimensional materials are presented in heterostructures and intercalated with inorganic components or organic molecules.
High-temperature phonon thermal conductivity of nanostructures
Physical Review B, 2002
Phonon propagation in the disordered nanostructures at a high ͑about the Debye temperature or higher͒ temperature is considered. Scattering at the grain boundaries is assumed to be the main mechanism restricting the thermal conductivity. Influence of the structure ͑the grain size and its dispersion, the pore diameter and their volume concentration, and the intergrain interface structure͒ as well as temperature on the thermal conductivity is discussed.
Journal of Applied Physics, 2016
In the past two decades, phonon transport within nanoporous thin films has attracted enormous attention for their potential applications in thermoelectrics and thermal insulation. Various computational studies have been carried out to explain the thermal conductivity reduction within these thin films. Considering classical phonon size effects, the lattice thermal conductivity can be predicted assuming diffusive pore-edge scattering of phonons and bulk phonon mean free paths. Following this, detailed phonon transport can be simulated for a given porous structure to find the lattice thermal conductivity [Hao et al., J. Appl. Phys. 106, 114321 (2009)]. However, such simulations are intrinsically complicated and cannot be used for the data analysis of general samples. In this work, the characteristic length K Pore of periodic nanoporous thin films is extracted by comparing the predictions of phonon Monte Carlo simulations and the kinetic relationship using bulk phonon mean free paths modified by K Pore. Under strong ballistic phonon transport, K Pore is also extracted by the Monte Carlo ray-tracing method for graphene with periodic nanopores. The presented model can be widely used to analyze the measured thermal conductivities of such nanoporous structures.
ES Materials & Manufacturing, 2019
Tailoring thermal properties with nanostructured materials can be of vital importance for many applications. Generally classical phonon size effects are employed to reduce the thermal conductivity, where strong phonon scattering by nanostructured interfaces or boundaries can dramatically suppress the heat conduction. When these boundaries or interfaces are arranged in a periodic pattern, coherent phonons may have interference and modify the phonon dispersion, leading to dramatically reduced thermal conductivity. Such coherent phonon transport has been widely studied for superlattice films and recently emphasized for periodic nanoporous patterns. Although the wave effects have been proposed for reducing the thermal conductivity, more recent experimental evidence shows that such effects can only be critical at an ultralow temperature, i.e., around 10 K or below. At room temperature, the impacted phonons are mostly restricted to hypersonic modes that contribute little to the thermal conductivity. In this review, the theoretical and experimental studies of periodic porous structures are summarized and compared. The general applications of periodic nanostructured materials are further discussed.
Effect of wave versus particle phonon nature in thermal transport through nanostructures
Computational Materials Science, 2020
Comprehensive understanding of thermal transport in nanostructured materials needs large scale simulations bridging length scales dictated by different physics related to the wave versus particle nature of phonons. Yet, available computational approaches implicitly treat phonons as either just waves or as particles. In this work, using a full wavebased Non-Equilibrium Green's Function (NEGF) method, and a particle-based ray-tracing Monte Carlo (MC) approach, we investigate the qualitative differences in the wave and particle-based phonon transport at the vicinity of nanoscale features. For the simple example of a nanoporous geometry, we show that phonon transmission agrees very well for both methods with an error margin of ± 15%, across phonon wavelengths even for features with sizes down to 3-4 nm. For cases where phonons need to squeeze in smaller regions to propagate, we find that MC underestimates the transmission of long wavelength phonons whereas wave treatment within NEGF indicates that those long wavelength phonons can propagate more easily. We also find that particle-based simulation methods are somewhat more sensitive to structural variations compared to the wave-based NEGF method. The insight extracted from comparing wave and particle methods can be used to provide a better and more complete understanding of phonon transport in nanomaterials.
Size effects in thermal conduction by phonons
Physical Review B, 2014
Heat transport in nanoscale systems is both hard to measure microscopically, and hard to interpret. Ballistic and diffusive heat flow coexist, adding confusion. This paper looks at a very simple case: a nanoscale crystal repeated periodically. This is a popular model for simulation of bulk heat transport using classical molecular dynamics (MD), and is related to transient thermal grating experiments. Nanoscale effects are seen in perhaps their simplest form. The model is solved by an extension of standard quasiparticle gas theory of bulk solids. Both structure and heat flow are constrained by periodic boundary conditions. Diffusive transport is fully included, while ballistic transport by phonons of long mean free path is diminished in a specific way. Heat current J(x) and temperature gradient ∇T (x) have a non-local relationship, via κ(x − x), over a distance |x − x | determined by phonon mean free paths. In MD modeling of bulk conductivity, finite computer resources limit system size. Long mean free paths, comparable to the scale of heating and cooling, cause undesired finite-size effects that have to be removed by extrapolation. The present model allows this extrapolation to be quantified. Calculations based on the Peierls-Boltzmann equation, using a generalized Debye model, show that extrapolation involves fractional powers of 1/L. It is also argued that heating and cooling should be distributed sinusoidally (ė ∝ cos(2πx/L)) to improve convergence of numerics.