Thermal Conductivity Of Carbon Nanotubes Research Articles

Thermal Transport in Nano Structured Carbon Nanotubes and Its Thermal Conductance

We have studied thermal transport in nano-structured carbon nanotubes and have calculated its thermal conductance using the nonequilibrium Green’s function method. The thermal conductance of carbon nanotubes linearly depended on the width of the unzipped part of the carbon nanotube but exponentially decayed and then converged to a finite value of the unzipped length increased. But characteristics are unusual to common bulk materials but are universal to nano materials of nanotube and graphene like structures. An exponentially decayed thermal conductance with the length was found at interfaces. Electronic conductance was found to show an exponential thermal transport in carbon nanotubes showed features distinctly different from those in common bulk materials. Carbon nanotubes have been found strong structural imperfections; their thermal conductance exhibited unexpectedly perfect linear scaling behavior as the width of the unzipped part changed. As the unzipped length increased, thermal conductance exponentially decreased by the one dimensional atomic chain model. The obtained results were found in good agreement with previous results.

Is the Hamilton-Crosser model of any relevance? – A contribution dedicated to the 150th anniversary of Maxwell's model and the 100th anniversary of Fricke's model

The Hamilton-Crosser model (HC model) is designed to describe the thermal conductivity of suspensions and nanofluids with anisometric particles. It is one of the most widely cited models in the nanofluid community. In this paper we show, however, that the HC model (1962) is essentially scientific folklore. It is an incorrect reformulation of a correct model that has been derived almost a century ago, Fricke's model (1924). The latter is a generalization to ellipsoids, in particular spheroids, of Maxwell's model (1873) for spheres. Fricke's model is an effective medium approximation that provides admissible (though not necessarily realistic) predictions of the thermal conductivity of carbon nanotube or graphene nanoplatelet nanofluids, while the HC model is an inadmissible variant of the same model, because it cannot reproduce the correct predictions (Fricke's model) and under certain circumstances it even violates a basic law of physics, the upper Hashin-Shtrikman bound (1962). Thus, it cannot be used for any isotropic system. Therefore, in contrast to common belief, any comparison of experimental data with the HC model predictions is irrelevant and all attempts to “improve” or “renovate” the HC model should be abandoned.

Review of: "Thermal conductivity of carbon nanotubes from a theoretical point of view for the reproduction of nanotransistors"

Review of: "Thermal conductivity of carbon nanotubes from a theoretical point of view for the reproduction of nanotransistors"

Influence mechanism of functionalization of CNTs on the thermal transport property of their nanofluids

Carbon nanotube (CNT) nanofluids have promising application prospects as the working fluids in energy and power systems due to their prominent thermal properties, while the poor stability of CNT nanofluids is one of the biggest obstacles to their practical application. The addition of functional groups on CNTs is a good method to improve the dispersion of CNT nanofluids, while the influence mechanism of this strategy on the thermal transport property is not clear. In this work, the thermal conductivities of CNT, CNT-OH, and CNT-COOH nanofluids were investigated by experiments and molecular dynamics (MD) simulations to reveal the influence mechanism of functionalization on the thermal transport ability of CNT nanofluids. Both experimental measurements and MD simulations indicate the significant suppression of functionalization on the thermal transport property of CNT nanofluids. Furthermore, the influence mechanism of functional groups on the thermal conductivity of CNT nanofluids has been revealed by analyzing the effect of the thermal conductivities of CNTs, the formation of hydrogen bonds, the mean square displacement of water molecules, and the interlayer thermal resistance of CNT and water. This work is helpful to the utilization of CNT nanofluids as working fluids in energy systems.

Tuning structural and thermal conductivity of carbon nanotubes under strain effects

Equilibrium molecular dynamics (EMD) computations have been performed to estimate the thermal conductivity (λ) of armchair and chiral single-walled carbon nanotubes (SWCNTs) under the influence of varying axial compressive and tensile strains ±γ(%). For the first time, the present work provides new outcomes of structural behavior of SWCNTs linked through λ, considering the combinations of nanotube length (L), system temperature (T) and effects of varying ±γ(%). A radial distribution function (RDF) test has performed in order to investigate the structure analysis of armchair and chiral SWCNTs with different compressive (−1% – −10%) and tensile (+1% – +10%) strain sequences at the extreme L (= 100 Å and 1900 Å) and T (=300 K). The RDF and visualization tests indicate that both configurations are more tunable under tensile strain but the buckling processes of armchair SWCNTs are less evident as compared to chiral configurations. The simulation data shows that the λ(T, L) increases as L extends and it also confirmed through slight increase in RDF peaks, while the λ(T, L) of chiral SWCNTs is high compared to armchair SWCNTs for a complete range of T at L (= 100 Å and 1900 Å). However, the calculations indicate that the delta change in λ(T, L) of armchair SWCNTs is more than the chiral one, as expected. The simulation data demonstrates that the positions of the highest and lowest values of the thermal conductivity of the chiral SWCNTs shift to a longer L as compared to the armchair SWCNTs. The λ(T, L) of SWCNTs remains high for -γ(%) range at short L (=100 Å) due to less broaden shift in RDF peaks but slightly higher for +γ(%) range at longer L (=1900 Å) due to boarder shift in RDF peaks. Moreover, the present simulation results obtained from EMD approach are found to be in reasonable agreement with those obtained via the previous known numerical results.

An overview of current status, application, and future development about carbon nanotube

Carbon Nanotube (CNTs) could cause inflammation respiratory and blood vessels in the human body. The limitation of arc discharge, laser ablation and CVD hinders the support of large scale demands for technology innovation and civilization-level engineering project,which also encourages and promotes the investment of research and commercial development. This paper discusses the discovered properties, recent application, and production of CNTs by collecting recent open literature. The high-performance machinal properties, electric conductivity, and thermal conductivity of CNTs with related application are experimented and explained. The current problems faced, including toxicity and mass production challenges, are stated, and how they reflect prospects and future directions of CNTs are pointed out in this paper. This study shows that mass demand created by pioneering and breaking construction can accelerate the process of material development.

Modeling the thermal conductivity of carbon nanotube (CNT) nanofluids and nanocomposites – a fresh restart

After two decades of discussion it seems that the model-based prediction of the thermal conductivity of carbon nanotube (CNT) nanofluids and nanocomposites has come to a dead end and needs a fresh restart, since misleading statements and claims and repeated over and over again, mainly in the current literature on CNT nanofluids. In this paper a simple but rigorous model is presented (in two variants) for predicting the thermal conductivity of CNT nanofluids and nanocomposites. The model is based on Fricke's classical Maxwell-type effective medium approximation for systems with spheroidal particles, but – in contrast to all previous models – takes into account the Molyneux bounds for describing the random orientation of the CNTs. We show that the predictions of our model are significantly lower than the corresponding predictions via Nan's model and will thus turn out to be closer to experimental data reported in the literature.

Modeling of thermal conductivity for disordered carbon nanotube networks

Several theoretical models have been developed so far to predict the thermal conductivities of carbon nanotube (CNT) networks. However, these models overestimated the thermal conductivity significantly. In this paper, we claimed that a CNT network can be considered as a contact thermal resistance network. In the contact thermal resistance network, the temperature of an individual CNT is nonuniform and the intrinsic thermal resistance of CNTs can be ignored. Compared with the previous models, the model we proposed agrees well with the experimental results of single-walled CNT networks.

OPTIMIZATION OF NANO FILLERS CONTENT TO FABRICATE ELECTRICALLY CONDUCTIVE CARBON FIBER REINFORCED POLYMER FOR SPACE USE

Carbon fiber reinforced polymer (CFRP) composites are used in aerospace sector due to their high specific stiffness and light weight, and are a better alternative for aluminum, Invar, and Kovar alloys. However, lower electrical and thermal conductivity of CFRP was the main restriction for extensive use in aerospace sector as compared to aluminum alloys. High aspect ratio, high mechanical stability, high electrical as well as thermal conductivity of carbon nanotubes (CNTs) makes them excellent filler material in CFRP to enhance its electrical, mechanical, and thermal properties. CNTs add synergetic effect to CFRP giving improved CNT-CFRP composites in terms of electrical and mechanical properties. Single-walled carbon nanotubes (SWCNTs) and multi-walled carbon nanotubes (MWCNTs) are used as filler for fabricating conductive CFRP. Selection of type of CNT (SW/MW-CNT), percentage of CNTs to be used as filler, extent of dispersion in thermosetting resin and carbon fiber layers, governs the properties of CNT-CFRP composites. Objective of the current study was to find optimum percentage of SWCNT and MWCNT to get highly electrically conductive CNT-CFRP composites with ease of manufacturing.

Regulatable thermal conductivity and excellent mass transport of water-filled carbon nanotube as capillary wicks

• The heat and mass transfer of single wall carbon nanotubes as capillary wicks are studied by molecular dynamics simulations. • The regulatable thermal conductivity can be beneficial to both start-up and overheating operation of heat pipe. • The thermal conductivity of carbon nanotube is reduced due to the thermal motion of water molecules and vdW force. Passive liquid cooling of ultrathin heat pipe has received considerable attention due to its excellent performance of removing heat from hot spot of electronic devices. However, achieving controllable thermal conductivity of the capillary wick materials to reduce the start-up time and total thermal resistance remains a challenge. Here we propose the capillary wick of carbon nanotube array to regulate its heat transfer performance via the water filling ratio. Molecular dynamics simulation results found that the thermal conductivity of water-filled carbon nanotubes is reduced by 17.8%-23.8%, which is benefit to start-up operation. At overheating operation, the high thermal conductivity of empty carbon nanotube can reduce the temperature of the endothermic surface. Importantly, the thermophoretic movement speed of water can reach up to 74 m/s and radial mass exchange occurs driven by temperature gradient. Phonon spectral analysis and heat flow decomposition revealed that the decrease of water-filled carbon nanotube thermal conductivity originates from the low-energy coupling of van der Waals force between water molecules and carbon nanotube and the thermal motion of two water molecules layers. The regulatable thermal conductivity and excellent mass transport performance demonstrate the promising potential of carbon nanotube as next-generation capillary wick of ultrathin heat pipe.

Application of Nanocomposite Energy Storage Materials in Green Building Design.

In order to solve the problem of the application of composite phase change heat storage materials in building energy conservation, the author proposes the application of nanocomposite energy storage materials in green building design. Modified carbon nanotubes were prepared by mixed acid oxidation and ball milling, and composited with stearic acid to prepare phase change heat storage materials. Modified carbon nanotubes were prepared by mixed acid oxidation and ball milling and composited with stearic acid to prepare phase change heat storage materials. Experimental results show that acidified carbon nanotubes have a hindering effect on the thermal diffusion of stearic acid molecular segments so that the thermal conductivity of carbon nanotubes added with a mass fraction of 1% is only 1.3 times higher than that of pure stearic acid. Conclusion. Nanocomposite energy storage materials have excellent application prospects in green building design.

Effect of Surface Modification of Carbon Nanotubes on the Properties of High-Strength and High-Conductivity Copper Matrix Composites

The use of carbon nanotubes (CNTs) as the reinforcing phase to prepare copper-based composite materials can improve the strength and high conductivity of copper-based conductors. In order to analyze the effect of surface oxidation modification on the structural properties of carbon nanotubes and its strengthening effect on composite materials, this article combines heterogeneous copolymerization liquid phase mixing method and spark plasma sintering molding method; prepares the carbon nanotubes/copper composite materials using carbon nanotubes under different oxidation treatment conditions as the reinforcing phase (the volume fraction of carbon nanotubes is 3%); and characterizes the microstructure, mechanical properties, and electrical and thermal conductivity of the composite material. Studies have shown that the tensile strength and hardness of composite materials first increase with the increase of CNT oxidation treatment time and then decrease with the increase of oxidation treatment time. When the oxidation treatment time is 4 h, CNTs are uniformly dispersed in the matrix while maintaining good structural integrity and load-bearing capacity, and the composite material has the highest mechanical properties. The tensile strength of the composite material made of 80‐ nm CNTs reaches 452.4 MPa, which is 1.6 times that of pure copper, and the hardness reaches 127.4HV, which is twice that of pure copper. The electrical conductivity and thermal conductivity of the composite material first increase with the increase of the oxidation treatment time of carbon nanotubes and then decrease with the increase of the oxidation treatment time. The 80 nm CNT reinforced composite material has better CNT dispersion performance and higher conductivity than that of 15 nm CNT preparation. The electrical conductivity of the composite material reaches the maximum value of 92% IACS when the CNT oxidation treatment time is 4 hours, which is 95% of the pure copper sample, and the electrical conductivity is significantly better than that of the CNT/Cu composite material and copper alloy prepared by other methods. The thermal conductivity of composite materials is lower than that of pure copper. The thermal conductivity of carbon nanotubes with an oxidation treatment time of 2 h decreases most obviously, indicating that the thermal resistance generated by the interface and agglomeration phases in the composite material affects its thermal conductivity.

Comment on "Ultrahigh Convergent Thermal Conductivity of Carbon Nanotubes from Comprehensive Atomistic Modeling".

Received 14 September 2021Accepted 23 May 2022DOI:https://doi.org/10.1103/PhysRevLett.128.259601© 2022 American Physical SocietyPhysics Subject Headings (PhySH)Research AreasPhononsThermal conductivityPhysical SystemsCarbon-based materialsNanotubesNanowiresTechniquesBoltzmann theoryMolecular dynamicsCondensed Matter, Materials & Applied Physics

Study on the theoretical calculation method for the effective thermal conductivity of carbon nanotube composite molten salt for solar energy application

Carbonate salt is a potential heat storage material for solar thermal power. Aimed at calculating the effective thermal conductivity of Li 2 CO 3 -K 2 CO 3 eutectic doped with carbon nanotube (CNT), a theoretical calculation method based on the three-dimensional random curl structure model was developed. Meanwhile, for the purpose of method verification, CNT composite molten salt was prepared by high-energy ball grinding method. The curl degree of carbon nanotube was determined by image identification technique. The effective thermal conductivity of the composite molten salt was measured to validate the calculation model. The comparison showed that, for well-mixed CNT composite molten salt, the error of the theoretical calculation model was less than 8.5%, which indicated that this calculation model can be used to calculate the effective thermal conductivity of CNT composite molten salt. Moreover, the influence of key factors such as the curl degree and aspect ratio of CNT on the effective thermal conductivity of composite molten salt were revealed. The results included that, first, the effective thermal conductivity ( λ eff ) of composite molten salt decreased with increasing CNT curl degree. Second, increasing CNT aspect ratio to 175 could improve λ eff of composite molten salt. Third, the increase of CNT thermal conductivity was the key factor to the improvement of λ eff of composite molten salt. Fourth, λ eff of the composite molten salt could be significantly increased when the order of magnitude of the interfacial thermal resistance (m 2 ·K·W −1 ) was reduced to 10 −7 . • A calculation model on λ of CNT enhanced molten salt for heat storage is given. • Curl phenomenon of carbon nanotube is quantified via image identification. • 3-D random curl structure physical model is established. • Carbon nanotube enhanced salt is prepared by ball milling method and tested. • Effective thermal conductivity calculation is validated with experiments.

Molecular dynamics study of thermal conductivity of carbon nanotubes and silicon carbide nanotubes

In this paper, the application of Muller-Plathe method and Jund method in reverse nonequilibrium molecular dynamics to the heat conduction of one-dimensional nanotubes are tested and studied. The results show that the Jund method cannot obtain a good linear temperature gradient and its thermal conductivity is also dependent on the choice of heat flux. When the exchange frequency is 50, the thermal conductivity obtained by the Muller-Plathe method converges to a stable value. This method can be well applied to the study of thermal conductivity of nanotubes. The Muller-Plathe method is a good option when the number of atoms exchanged is 1 and the exchange frequency is 100. On this basis, we further investigate the effect of length, diameter and temperature of carbon nanotubes and silicon carbide nanotubes on the thermal conductivity. The thermal conductivity of carbon nanotubes is obviously higher than that of silicon carbide nanotubes, and their effects of length, diameter and temperature on the thermal conductivity are consistent. The thermal conductivity of nanotubes increases with the rise of temperature, but the increase rate decreases and the length dependence also weakens. Therefore, when carbon nanotubes and silicon carbide nanotubes reach certain lengths, their values of thermal conductivity will converge and no longer change with length, which is completely consistent with the results of previous studies. Comparing with carbon nanotubes, the convergence rate of thermal conductivity of SiC nanotubes is significantly lower. When the temperature is low, the diameter has a certain effect on the thermal conductivity; however, with the increase of temperature, the diameter has almost no effect on the thermal conductivity at high temperature. The effect of temperature on the thermal conductivity of nanotubes shows that the thermal conductivity of nanotubes generally decreases with the rise of temperature, but the occurrence of the peak phenomenon is also affected by the length of nanotubes. When the length of carbon nanotubes is 10 nm, the influence of temperature and diameter on the thermal conductivity are irregular. However, when the length of carbon nanotubes is 100 nm, the thermal conductivity of carbon nanotubes decreases continuously with the rise of temperature, and there occurs no peak phenomenon. Besides, when the tube length is 10 nm, the peak of SiC nanotubes appears at about 100 K. However, when the tube length is 100 nm, the thermal conductivity of SiC nanotubes decreases with the rise of temperature, but no peak phenomenon occurs.

Modeling the Thermal Conductivity of Carbon Nanotube (Cnt) Nanofluids and Nanocomposites – a Fresh Restart

Modeling the Thermal Conductivity of Carbon Nanotube (Cnt) Nanofluids and Nanocomposites – a Fresh Restart

Effects of Current Annealing on Thermal Conductivity of Carbon Nanotubes.

This work documents the annealing effect on the thermal conductivity of nanotube film (CNTB) and carbon nanotube fiber (CNTF). The thermal properties of carbon nanotube samples are measured by using the transient electro-thermal (TET) technique, and the experimental phenomena are analyzed based on numerical simulation. During the current annealing treatment, CNTB1 always maintains the negative temperature coefficient of resistance (TCR), and its thermal diffusivity increases gradually. When the annealing current is 200 mA, it increases by 33.62%. However, with the increase of annealing current, the TCR of CNTB2 changes from positive to negative. The disparity between CNTB2 and CNTB1 suggests that they have different physical properties and even structures along their lengths. The high-level thermal diffusivity of CNTB2 and CNTF are 2.28–2.46 times and 1.65–3.85 times higher than the lower one. The results show that the decrease of the thermal diffusivity for CNTB2 and CNTF is mainly caused by enhanced Umklapp scattering, the high thermal resistance and torsional sliding during high temperature heating.

Numerical Approximation of Microorganisms Hybrid Nanofluid Flow Induced by a Wavy Fluctuating Spinning Disc

The analysis explored a numerical simulation of microorganisms, carbon nanotubes (CNTs) and ferric oxide water-based hybrid nanofluid flow induced by a wavy fluctuating spinning disc with energy propagation. In the presence of CNTs and magnetic nanoparticulates, the nanofluid is synthesized. The exceptional tensile strength, flexibility, and electrical and thermal conductivity of carbon nanotubes and iron nanoparticles have been extensively reported. The motive of the proposed analysis is to optimize thermal energy conveyance efficiency for a spectrum of industrial and biomedical applications. The phenomena have been expressed as a system of partial differential equations (PDEs) which contain the momentum, energy, concentration, and motile microorganism equations. The modeled equations have been diminished to the dimensionless system of nonlinear ODEs through a similarity framework. The Matlab built-in package boundary value solver has been utilized to solve the obtained system of ODEs. The findings are compared to the PCM technique for validity purposes. The results are illustrated graphically and discussed. The layout of a rotating disc has a positive effect on energy transition and velocity profile. The irregular rotating surface increases energy progression up to 15% relative to a smooth surface. The accumulation of nanocomposites (CNTs and magnetic nanoparticles) significantly enhanced the thermal capabilities of the liquid medium. When operating with a low distribution, it is more impactful.

Carbon Nanotube Mask Filters and Their Hydrophobic Barrier and Hyperthermic Antiviral Effects on SARS-CoV-2.

Carbon nanotube face mask filters have strong and uniform hydrophobicity, high durability, and high thermal conductivity and exhibit excellent barrier and antiviral effects against SARS-CoV-2. The nanocarbon filter functions as a superior barrier compared to those in conventional masks owing to the stronger, more uniform, and more durable hydrophobic nature of the carbon nanotubes. A tightly knit carbon nanotube network has a pore size smaller than that of the average coronavirus; nevertheless, the breathability is equal to that of the conventional polypropylene filter. The exceptional thermal conductivity of carbon nanotubes transpires hyperthermic antiviral effects, which offers stronger protection against the virus, as well as reusability. The facile processability, low cost, and light weight of the aerosol-synthesized carbon nanotube filter warrants its viability, reinforcing the fight against the COVID-19 pandemic.

Влияние инкапсуляции фуллеренов на оптические и термоэлектрические свойства углеродных нанотрубок

The hybrid systems based on the carbon nanotubes (CNT) and fullerenes (nanopipodes) are promising for applications in nanoelectronics. With insignificant variation of the CNT diameter the change of the fullerenes geometry takes place. The periodically located inside fullerenes represent a set of quantum points in the one-dimensional super-lattice. Using the variation of inside fullerenes it is possible to modulate the zone structure of the CNT – fullerene system and to control the electronic and phonon characteristics of nanopipodes. In the work the optical and thermoelectric properties of CNT with encapsulated molecules of C60 fullerene have been investigated. Using the first-principle methods the coefficients of absorption, optical conductivi-ty, thermal conductivity, thermoelectric figure of merit for CNT with fullerenes, periodically lo-cated inside the nanotubes at different distances from each other, have been calculated. It has been shown that with decreasing the distance between fullerenes the optical conductivity of CNT – C60 is suppressed at high frequencies. It has been determined that the conductance of the structures with fullerenes is less than the conductance of a clean tube, and approximately equal for considered distances (12.3 and 19.7 Å) between fullerenes. The CNT thermal conductivity due to the encapsulation of fullerenes considerably (3–4 times) decreases for the considered CNT (8.8) – C60 systems.