scholarly journals Effect of Micro- to Nanosize Inclusions upon the Thermal Conductivity of Powdered Composites with High and Low Interface Resistance

2015 ◽  
Vol 2015 ◽  
pp. 1-8 ◽  
Author(s):  
Muhammad Zain-ul-abdein ◽  
Waqas S. Awan ◽  
Hassan Ijaz ◽  
Aqeel A. Taimoor ◽  
Ayyaz Muhammad ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Thermal Resistance ◽  
Volume Fraction ◽  
Effective Properties ◽  
Theoretical Models ◽  
Inclusion Size ◽  
Interfacial Thermal Resistance ◽  
Interfacial Resistance ◽  
Filler Volume Fraction ◽  
The Matrix

Materials for thermal management application require better control over the thermophysical properties, which has largely been achieved by fabricating powdered composite. There are, however, several factors like filler volume fraction, shape morphology, inclusion size, and interfacial thermal resistance that limit the effective properties of the medium. This paper presents a methodology to estimate the effective thermal conductivity of powdered composites where the filler material is more conductive than the matrix. Only a few theoretical models, such as Hasselman and Johnson (HJ) model, include the effect of interfacial resistance in their formulation. Nevertheless, HJ model does not specify the nature of the interfacial thermal resistance. Although Sevostianov and Kachanov (SK) method takes care of interface thickness, they, on the other hand, have not taken into account the interfacial resistance due to atomic imperfections. In the present work, HJ model has been modified using SK method and the results were compared with experimental ones from the literature. It has been found that the effect of interfacial resistance is significant in highly resistive medium at microscale compared to nanoscale, such as Cu/diamond system, while, in a highly conductive medium, like bakelite/graphite system, the effect of shape factor is more significant than interfacial thermal resistance.

Effective Thermal Conductivity of Functionally Graded Particulate Nanocomposites With Interfacial Thermal Resistance

2008 ◽  
Vol 75 (5) ◽  
Author(s):  
H. M. Yin ◽  
G. H. Paulino ◽  
W. G. Buttlar ◽  
L. Z. Sun
Keyword(s):  
Thermal Conductivity ◽  
Thermal Resistance ◽  
Effective Thermal Conductivity ◽  
Functionally Graded ◽  
Interfacial Thermal Resistance ◽  
Conductivity Distribution ◽  
Consistent Model ◽  
The Matrix ◽  
Graded Material ◽  
Perfect Interface

By means of a fundamental solution for a single inhomogeneity embedded in a functionally graded material matrix, a self-consistent model is proposed to investigate the effective thermal conductivity distribution in a functionally graded particulate nanocomposite. The “Kapitza thermal resistance” along the interface between a particle and the matrix is simulated with a perfect interface but a lower thermal conductivity of the particle. The results indicate that the effective thermal conductivity distribution greatly depends on Kapitza thermal resistance, particle size, and degree of material gradient.

Modeling and Measurement of Pressure-Dependent Junction-Spreader Thermal Resistance for Integrated Circuits

2001 ◽  
Author(s):  
Peng Zhou ◽  
Kenneth E. Goodson
Keyword(s):  
Integrated Circuits ◽  
Thermal Resistance ◽  
Volume Fraction ◽  
Past Research ◽  
Theoretical Models ◽  
Thermal Interface Material ◽  
Simple Relationship ◽  
Reliability Engineering ◽  
Transient Model ◽  
Filler Volume Fraction

Abstract The junction-spreader thermal resistance is an important part of the overall junction-ambient thermal resistance in electronic packages. Past research has provided theoretical models for contact thermal resistance between the thermal interface material (TIM) and the contacting rough solid surface. However, these models are based on steady-state assumptions and do not describe the evolution of the junction-spreader thermal resistance during the lifetime of an electronic package. This chapter presents a transient model for the junction-spreader thermal resistance based on classical theories for lubrication and surface wettability. This transient model provides a simple relationship for pressure-dependent junction-spreader thermal resistance and yields an optimum filler volume fraction for particle filled TIMs. An experimental approach developed in this chapter measures the pressure-dependence, as well as the spatial distribution of junction-spreader thermal resistance. The data agree reasonably well with the model predicting for the pressure-dependent junction-spreader thermal resistance. The theoretical and experimental approaches developed in this study are promising tools for thermal management and reliability engineering of electronic packaging.

Thermal Transport Properties and Interface Effects of Carbon Nanostructures

2017 ◽  
Author(s):  
Sushan Nakarmi ◽  
V. U. Unnikrishnan
Keyword(s):  
Thermal Conductivity ◽  
Thermal Resistance ◽  
Thermal Transport ◽  
Carbon Nanostructures ◽  
Heat Bath ◽  
Md Simulations ◽  
Interfacial Thermal Resistance ◽  
Interfacial Resistance ◽  
Intrinsic Properties ◽  
Thermal Transport Property

The variations in thermal conductivity of nanocomposites are found to depend not only the intrinsic properties of the fiber and matrix phases but also on the interfacial resistance of the reinforcing phase. As we go down the length scales, the interfacial thermal resistance due to size of the nanoparticle becomes significant. In order to address the effect of size (length and diameter) of nanotube on the thermal transport property of nanotube composites, thermal conductivity of different nanotube samples varying in length and diameter will be estimated first using molecular dynamic (MD) simulations with AIREBO potentials. This will be carried out using the ‘Heat-Bath’ method - non-equilibrium molecular dynamics (NEMD) approach. In the heat bath method, constant amount of heat is added to and removed from the hot and cold regions and the resulting temperature gradient is measured and the thermal conductivity is calculated using the Fourier Law. This will be followed by the study of interfacial thermal resistance of these nanostructures. These intrinsic properties are then used with continuum based mathematical formulations to study the effect of size of the nanoparticle on the overall thermal conductivity of the nanocomposite.

scholarly journals A Multi-Scale, Semi-Analytical Model for Transient Heat Transfer in a Nano-Composite Containing Spherical Inclusions

2019 ◽  
Vol 21 (2) ◽  
pp. 101
Author(s):  
A. Dobri ◽  
T.D. Papathanasiou
Keyword(s):  
Thermal Conductivity ◽  
Thermal Resistance ◽  
Effective Thermal Conductivity ◽  
Analytical Model ◽  
Transient Response ◽  
Interfacial Thermal Resistance ◽  
Spherical Inclusions ◽  
Macro Scale ◽  
The Matrix ◽  
Two Phases

This paper presents a semi-analytical model for transient heat conduction in a composite material reinforced with small spherical inclusions. Essential to the derivation of the model is the assumption that the size of the inclusions is much smaller than the length scale characterizing the macroscopic problem. An interfacial thermal resistance is also present between the two phases. During heating, the inclusions are treated as heat sinks within the matrix, with the coupling provided by the boundary conditions at the surface of the embedded particles. Application of Duhamel’s Theorem at the particle scale provides the local relationship between the temperature profile in a particle and the matrix that surrounds it. A simple spatial discretization at the macro-scale leads to an easily solvable system of coupled Ordinary Differential Equations for the matrix temperature, particle surface temperature and a series of ψ-terms related to the heat exchange between phases. The interfacial thermal resistance between the two phases can lead to the particle temperature lagging behind that of the surrounding matrix. The resulting transient response of the matrix temperature cannot be reproduced by a material with a single effective thermal conductivity. In the case where transient methods are used to determine effective thermal conductivity, this transient response may introduce errors into the measurement.

Thermal Transport at Carbon Nanotube-Graphene Junction

2013 ◽  
Author(s):  
Jungkyu Park ◽  
Vikas Prakash
Keyword(s):  
Thermal Conductivity ◽  
Molecular Dynamics ◽  
Carbon Nanotube ◽  
Thermal Resistance ◽  
Thermal Transport ◽  
Single Layer ◽  
Single Layer Graphene ◽  
Interfacial Thermal Resistance ◽  
Interfacial Resistance ◽  
Pillar Height

We present results of a molecular dynamics study to analyze thermal transport at carbon nanotube (CNT)-graphene junctions comprising of single layer graphene and (6,6) armchair single-walled carbon nanotubes (SWCNTs). Two possible junction types with different degrees of sp2 and sp3 hybridization are investigated. Reverse Non-Equilibrium Molecular Dynamics (RNEMD) simulations are used to obtain the thermal conductivities in these hybrid structures and also analyze the role of the interfacial thermal resistance at the SWCNT-graphene junctions in limiting thermal transport. The highest out-of-plane (along the SWCNT axis) thermal conductivity of a hybrid structure with a CNT-graphene junction was obtained to be 158.9±1.2 W/m-K when the junction comprised of only sp2 bonds with an interpillar distance of 15 nm and a pillar height of 200 nm. The highest in-plane thermal conductivity (along the graphene layer plane) with two CNT-graphene junctions was found to be 392.2±9.9 W/m-K with junctions comprising of only sp2 bonds and an interpillar distance of 20 nm and a pillar height of 25 nm. In all cases, junctions with mixed sp2/sp3 hybridization showed higher interfacial thermal resistance than junctions with pure sp2 bonds, and the thermal interfacial resistance was found to be weakly dependent on the length of CNT and the interpillar distance. The highest interfacial thermal resistance measured across the CNT-graphene junction was 3.10×10−6 K-cm2/W when the junction comprised of mixed sp2/sp3 bonds and with 15 nm interpillar distance and 50 nm pillar height.

Thermal Modeling of Randomly Distributed Multi-Walled Carbon Nanotube/Polymer Composites

2012 ◽  
Vol 548 ◽  
pp. 123-127
Author(s):  
Xiao Tuo Li ◽  
Xin Yu Fan ◽  
Ying Dan Zhu ◽  
Juan Li
Keyword(s):  
Thermal Conductivity ◽  
Carbon Nanotube ◽  
Thermal Resistance ◽  
Polymer Composites ◽  
Volume Fraction ◽  
Three Dimensional ◽  
Interfacial Thermal Resistance ◽  
The Finite Element Method ◽  
Multi Walled Carbon Nanotube ◽  
The Relationship

A three-dimensional computational model based on the finite element method was developed to predict the thermal properties of randomly distributed multi-walled carbon nanotube (MWCNT)/polymer composites. The numerical results agree very well with the experimental data for MWCNT/epoxy composites with the MWCNT loading below ~10 vol% at the interfacial thermal resistance of ~1.0×10-8 m2K/W, which may give insight into the relationship between the thermal behavior of MWCNT-matrix interfaces and the thermal conductivity of composites. This model is also a useful tool to evaluate the effects of MWCNT-matrix interfacial thermal resistance, volume fraction, thermal conductivity and diameter of MWCNTs on the thermal conductivity of other types of MWCNT/ polymer composites.

scholarly journals Thermal conductivity of silicone elastomer with a porous alumina continuum

e-Polymers ◽  
2021 ◽  
Vol 21 (1) ◽  
pp. 845-853
Author(s):  
Qichao Song ◽  
Bo Wang ◽  
Zhiyu Han ◽  
Zhidong Han
Keyword(s):  
Thermal Conductivity ◽  
Thermal Resistance ◽  
Effective Medium Theory ◽  
Porous Alumina ◽  
Theoretical Models ◽  
Silicone Elastomer ◽  
Interfacial Thermal Resistance ◽  
X Ray Diffraction ◽  
Medium Theory ◽  
Gel Casting

Abstract In this paper, porous alumina continuum (PAC) was prepared with alumina powders (APs) by the gel-casting method and was applied to obtain silicone elastomer (SR) composites (PAC/SR) by the impregnating process. The structure was investigated by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The influences of PAC on thermal conductivity and dielectric permittivity of PAC/SR composites were studied in comparison with AP/SR composites. When the alumina content was 14 vol%, the thermal conductivity of the PAC/SR composites reached 0.84 W·(m·K)−1, which was 3.1 times higher than that of the AP/SR composites. The thermal conductivity of PAC/SR and AP/SR was simulated by theoretical models, and the interfacial thermal resistance was calculated by effective medium theory, which indicated the advantages of PAC in enhancing the thermal conductivity of SR-based composites and the reduced interfacial thermal resistance between PAC and SR.

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