scholarly journals Thermal Transport Properties of Dry Spun Carbon Nanotube Sheets

2016 ◽  
Vol 2016 ◽  
pp. 1-8 ◽  
Author(s):  
Heath E. Misak ◽  
James L. Rutledge ◽  
Eric D. Swenson ◽  
Shankar Mall
Keyword(s):  
Thermal Conductivity ◽  
Carbon Nanotube ◽  
Thermal Transport ◽  
Transport Theory ◽  
Primary Concern ◽  
Potential Candidate ◽  
Ir Camera ◽  
Dry Spinning ◽  
Out Of Plane ◽  
Plane Direction

The thermal properties of carbon nanotube- (CNT-) sheet were explored and compared to copper in this study. The CNT-sheet was made from dry spinning CNTs into a nonwoven sheet. This nonwoven CNT-sheet has anisotropic properties in in-plane and out-of-plane directions. The in-plane direction has much higher thermal conductivity than the out-of-plane direction. The in-plane thermal conductivity was found by thermal flash analysis, and the out-of-plane thermal conductivity was found by a hot disk method. The thermal irradiative properties were examined and compared to thermal transport theory. The CNT-sheet was heated in the vacuum and the temperature was measured with an IR Camera. The heat flux of CNT-sheet was compared to that of copper, and it was found that the CNT-sheet has significantly higher specific heat transfer properties compared to those of copper. CNT-sheet is a potential candidate to replace copper in thermal transport applications where weight is a primary concern such as in the automobile, aircraft, and space industries.

scholarly journals Thermal transport properties of decagonal quasicrystals and their approximants

2013 ◽  
Vol 1517 ◽  
Author(s):  
Petar Popčević ◽  
Ante Bilušić ◽  
Kristijan Velebit ◽  
Ana Smontara
Keyword(s):  
Thermal Conductivity ◽  
Electrical Resistivity ◽  
Transport Properties ◽  
Heat Transport ◽  
Thermal Transport ◽  
Strong Relationship ◽  
Decagonal Quasicrystal ◽  
Decagonal Quasicrystals ◽  
Plane Anisotropy ◽  
Out Of Plane

ABSTRACTTransport properties (thermal conductivity, electrical resistivity and thermopower) of decagonal quasicrystal d-AlCoNi, and approximant phases Y-AlCoNi, o-Al13Co4, m-Al13Fe4, m-Al13(Fe,Ni)4 and T-AlMnFe have been reviewed. Among all presented alloys the stacking direction (periodic for decagonal quasicrystals) is the most conductive one for the charge and heat transport, and the in/out-of-plane anisotropy is much larger than the in-plane anisotropy. There is a strong relationship between periodicity length along stacking direction and anisotropy of transport properties in both quasicrystals and their approximants suggesting a decrease of the anisotropy with increasing number of stacking layers.

Increasing Efficiencies of Thermoelectric Devices Through Angular Interface Geometries

2009 ◽  
Author(s):  
D. P. Sellan ◽  
C. H. Amon
Keyword(s):  
Thermal Conductivity ◽  
Figure Of Merit ◽  
Equation Model ◽  
Boltzmann Transport ◽  
Thermoelectric Efficiency ◽  
Thermoelectric Figure ◽  
Subsequent Increase ◽  
Acoustic Mismatch ◽  
Out Of Plane ◽  
Plane Direction

The phonon Boltzmann transport equation model is used to evaluate the reduction of out-of-plane thermal conductivity and subsequent increase in thermoelectric figure of merit when an angular interface is patterned between a germanium thin-film and silicon substrate. According to the acoustic mismatch model, the angular structure reduces the out-of-plane thermal conductivity by spatially redistributing phonons traveling in the out-of-plane direction. Simulation results demonstrate a 43% reduction in out-of-plane thermal conductivity when operating in the fully ballistic regime. This decrease in phononic thermal conductivity would result in an increase of intrinsic thermoelectric efficiency by a factor of 1.75.

scholarly journals Thermal Resistance across Interfaces Comprising Dimensionally Mismatched Carbon Nanotube-Graphene Junctions in 3D Carbon Nanomaterials

2014 ◽  
Vol 2014 ◽  
pp. 1-10 ◽  
Author(s):  
Jungkyu Park ◽  
Vikas Prakash
Keyword(s):  
Carbon Nanotube ◽  
Thermal Resistance ◽  
Carbon Nanomaterials ◽  
Single Layer ◽  
Unit Cell ◽  
Single Layer Graphene ◽  
Interfacial Thermal Resistance ◽  
Layer Graphene ◽  
Out Of Plane ◽  
Plane Direction

In the present study, reverse nonequilibrium molecular dynamics is employed to study thermal resistance across interfaces comprising dimensionally mismatched junctions of single layer graphene floors with (6,6) single-walled carbon nanotube (SWCNT) pillars in 3D carbon nanomaterials. Results obtained from unit cell analysis indicate the presence of notable interfacial thermal resistance in the out-of-plane direction (along the longitudinal axis of the SWCNTs) but negligible resistance in the in-plane direction along the graphene floor. The interfacial thermal resistance in the out-of-plane direction is understood to be due to the change in dimensionality as well as phonon spectra mismatch as the phonons propagate from SWCNTs to the graphene sheet and then back again to the SWCNTs. The thermal conductivity of the unit cells was observed to increase nearly linearly with an increase in cell size, that is, pillar height as well as interpillar distance, and approaches a plateau as the pillar height and the interpillar distance approach the critical lengths for ballistic thermal transport in SWCNT and single layer graphene. The results indicate that the thermal transport characteristics of these SWCNT-graphene hybrid structures can be tuned by controlling the SWCNT-graphene junction characteristics as well as the unit cell dimensions.

Stochastic Modeling of the Bulk Thermal Conductivity for Dense Carbon Nanotube Networks

2009 ◽  
Author(s):  
Nikhil A. Ashtekar ◽  
David A. Jack
Keyword(s):  
Thermal Conductivity ◽  
Carbon Nanotube ◽  
Contact Resistance ◽  
Thermal Transport ◽  
Power Flow ◽  
Thermal Contact ◽  
Separation Distance ◽  
Bulk Conductivity ◽  
Carbon Nanotube Networks ◽  
Bulk Thermal Conductivity

A computational, physics-based, bulk thermal conductivity model of a neat carbon nanotube network at room temperature is developed using classical finite element techniques. The model is based on experimentally available stochastic distributions of length, diameter, chirality, and orientation, and uses theoretical results for thermal contact resistance from the literature and molecular dynamics simulations for the stochastic nature of tube separation distance. Understanding the thermal transport properties of carbon nanotube networks at various operating temperatures is crucial for the industrial acceptance of these materials in aerospace and electrical applications. Mechanisms of thermal transport are discussed including; thermal conductivity along the tube and inter-contact resistance between the tubes, where the later is considered the dominating factor. The effect of variations of several of the aforementioned stochastic factors influencing the bulk conductivity is investigated, and results demonstrate that changes in the nanotube length play a significant role in improving the bulk conductivity of the network. In addition, a brief study into localized power flow is presented and lends insight into a possible cause of premature network failure.

Interfacial thermal transport and structural preferences in carbon nanotube–polyamide-6,6 nanocomposites: how important are chemical functionalization effects?

2015 ◽  
Vol 17 (22) ◽  
pp. 14502-14512 ◽  
Author(s):  
Mohammad Reza Gharib-Zahedi ◽  
Mohsen Tafazzoli ◽  
Michael C. Böhm ◽  
Mohammad Alaghemandi
Keyword(s):  
Thermal Conductivity ◽  
Carbon Nanotube ◽  
Structural Properties ◽  
Thermal Transport ◽  
Chemical Functionalization ◽  
Structural Preferences

We investigate the influence of chemically functionalized CNTs on the structural properties of the surrounding polyamide-6,6 matrix as well as the interfacial thermal conductivity of polymer–CNT nanocomposites.

scholarly journals Industrial Thermal Insulation Properties above Sintering Temperatures

Materials ◽  
2021 ◽  
Vol 14 (16) ◽  
pp. 4721
Author(s):  
Amalie Gunnarshaug ◽  
Maria-Monika Metallinou ◽  
Torgrim Log
Keyword(s):  
Thermal Conductivity ◽  
Heat Treatment ◽  
Thermal Insulation ◽  
Fire Protection ◽  
Thermal Transport ◽  
Amorphous Materials ◽  
Transport Theory ◽  
Treatment Temperature ◽  
Dimensional Changes ◽  
Passive Fire Protection

Processing highly flammable products, the oil and gas (O&G) industry can experience major explosions and fires, which may expose pressurized equipment to high thermal loads. In 2020, oil fires occurred at two Norwegian O&G processing plants. To reduce the escalation risk, passive fire protection may serve as a consequence-reducing barrier. For heat or cold conservation, equipment and piping often require thermal insulation, which may offer some fire protection. In the present study, a representative thermal insulation (certified up to 700 °C) was examined with respect to dimensional changes and thermal transport properties after heat treatment to temperatures in the range of 700 °C to 1200 °C. Post heat treatment, the thermal conductivity of each test specimen was recorded at ambient temperature and up to 700 °C, which was the upper limit for the applied measurement method. Based on thermal transport theory for porous and/or amorphous materials, the thermal conductivity at the heat treatment temperature above 700 °C was estimated by extrapolation. The dimensional changes due to, e.g., sintering, were also analyzed. Empirical equations describing the thermal conductivity, the dimensional changes and possible crack formation were developed. It should be noted that the thermal insulation degradation, especially at temperatures approaching 1200 °C, is massive. Thus, future numerical modeling may be difficult above 1150 °C, due to abrupt changes in properties as well as crack development and crack tortuosity. However, if the thermal insulation is protected by a thin layer of more robust material, e.g., passive fire protection to keep the thermal insulation at temperatures below 1100 °C, future modeling seems promising.

Thermal Transport in Graphene Supported on Copper

2012 ◽  
Author(s):  
Liang Chen ◽  
Satish Kumar
Keyword(s):  
Thermal Conductivity ◽  
Thermal Transport ◽  
Copper Substrate ◽  
Interaction Strength ◽  
Thermal Coupling ◽  
Phonon Modes ◽  
Large Wave ◽  
Relaxation Time Approximation ◽  
Out Of Plane ◽  
Dynamics Simulations

The present study investigates the thermal transport in suspended graphene and graphene supported on copper substrate using equilibrium molecular dynamics simulations, Green-Kubo method and relaxation time approximation (RTA) approach. The thermal coupling between graphene and copper substrate was investigated by varying the interaction strength between the carbon atoms and Cu atoms at the interface. The contribution of different phonon modes to the thermal conductivity of suspended and supported graphene was analyzed in order to elucidate the graphene-substrate thermal interactions. The thermal conductivity of graphene decreases with the increasing strength of the interfacial interaction. The analysis shows that the interactions with copper substrate can reduce the thermal conductivity by up to 44%. The decrease of thermal conductivity is primarily due to the suppression of contribution from out-of-plane acoustic (ZA) phonons in the large wave vector region.

Strain Effect on Thermal Transport in Carbon Nanotube-Graphene Junctions

2018 ◽  
Author(s):  
Jungkyu Park ◽  
Paul Pena
Keyword(s):  
Thermal Conductivity ◽  
Carbon Nanotube ◽  
Flexible Electronics ◽  
Thermal Transport ◽  
Carbon Nanostructures ◽  
Tensile Strain ◽  
Mechanical Strain ◽  
Strain Effect ◽  
Interesting Phenomenon ◽  
Covalent Bonds

We employ molecular dynamics simulations to explore the effect of tensile strain on the thermal conductivity of carbon nanotube (CNT)-graphene junction structures. Two different types of CNT-graphene junctions are simulated; a perfect seamless junction between CNT and graphene with complete sp2 covalent bonds, and a CNT-graphene junction with mixed sp2/sp3 covalent bonds are studied. The most interesting phenomenon observed in the present research study is that the thermal conductivity of CNT-graphene junction structures increases with an increase in mechanical strain. For the case of CNT-graphene junction structure with pillar height of 50 nm and inter-pillar distance of 15 nm, the thermal conductivity is improved by 22.4% when 0.1 tensile strain is imposed. It is observed that the thermal conductivity improvement is enhanced when a larger graphene floor is placed between junctions since larger graphene floor allows larger deformation (larger tensile strain) in the junction. In addition, the thermal conductivity of CNT-graphene junction structures with pure sp2 bonds is observed to be higher than the thermal conductivity of CNT-graphene junction structures with mixed sp2/sp3 bonds regardless of the amount of tensile strain. The obtained results will contribute to the development of flexible electronics by providing a theoretical background on the thermal transport of three dimensional carbon nanostructures under deformation.

scholarly journals Enhanced thermal conductivity in immiscible polyimide blend composites with needle-shaped ZnO particles

RSC Advances ◽  
2017 ◽  
Vol 7 (25) ◽  
pp. 15492-15499 ◽  
Author(s):  
Shoya Uchida ◽  
Tomoya Murakami ◽  
Takeru Iwamura ◽  
Ryohei Ishige ◽  
Shinji Ando
Keyword(s):  
Thermal Conductivity ◽  
Composite Films ◽  
High Thermal Conductivity ◽  
Zno Particles ◽  
Out Of Plane ◽  
Plane Direction ◽  
Enhanced Thermal Conductivity

Novel composite films exhibiting high thermal conductivity along the out-of-plane direction were prepared from two types of immiscible polyimides (PIs) and needle-shaped ZnO particles.

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