Thermal Properties Of Carbon Nanotubes Research Articles

Wet-spinning of carbon nanotube fibers: dispersion, processing and properties

ABSTRACT Owing to the intrinsic excellent mechanical, electrical, and thermal properties of carbon nanotubes (CNTs), carbon nanotube fibers (CNTFs) have been expected to become promising candidates for the next-generation of high-performance fibers. They have received considerable interest for cutting-edge applications, such as ultra-light electric wire, aerospace craft, military equipment, and space elevators. Wet-spinning is a broadly utilized commercial technique for high-performance fiber manufacturing. Thus, compared with array spinning from drawable CNTs vertical array and direct dry spinning from floating catalyst chemical vapor deposition (FCCVD), the wet-spinning technique is considered to be a promising strategy to realize the production of CNTFs on a large scale. In this tutorial review, we begin with a summative description of CNTFs wet-spinning process. Then, we discuss the high-concentration CNTs wet-spinning dope preparation strategies and corresponding non-covalent adsorption/charge transfer mechanisms. The filament solidification during the coagulation process is another critical procedure for determining the configurations and properties for derived CNTFs. Next, we discuss post-treatment, including continuous drafting and thermal annealing, to further optimize the CNTs orientation and compact configuration. Finally, we summarize the physical property-structure relationship to give insights for further performance promotion in order to satisfy the prerequisite for detailed application. Insights into propelling high-performance CNTFs production from lab-scale to industry-scale are proposed, in anticipation of this novel fiber having an impact on our lives in the near future.

Investigation of thermal properties of carbon nanotubes and carboxyl group - functionalized carbon nanotubes

Thermal properties characterizations for carbon nanotubes (CNTs), carboxyl group-functionalized carbon nanotubes (FCNT), and graphite were presented in the paper. TGA/DSC and TEM techniques were used for characterization. The features of TGA characteristics transformation for synthesized carbon nanomaterials were investigated. The specific heat capacities of the samples at a constant pressure increased as the temperature increased.

Laser Sintering of CNT/PZT Composite Film

The discovery of piezoelectricity inspired several sensing applications. For these applications, the thinness and flexibility of the device increase the range of implementations. A thin lead zirconate titanate (PZT) ceramic piezoelectric sensor is advantageous compared with bulk PZT or a polymer when it comes to having minimal impacts on dynamics and high-frequency bandwidth provided by low mass or high stiffness, while satisfying constraints regarding tight spaces. PZT devices have traditionally been thermally sintered inside a furnace and this process consumes large amounts of time and energy. To overcome such challenges, we employed laser sintering of PZT that focused the power onto selected areas of interest. Furthermore, non-equilibrium heating offers the opportunity to use low-melting-point substrates. Additionally, carbon nanotubes (CNTs) were mixed with PZT particles and laser sintered to utilize the high mechanical and thermal properties of CNTs. Laser processing was optimized for the control parameters, raw materials and deposition height. A multi-physics model of laser sintering was created to simulate the processing environment. Sintered films were obtained and electrically poled to enhance the piezoelectric property. The piezoelectric coefficient of laser-sintered PZT increased by approximately 10-fold compared with unsintered PZT. Moreover, CNT/PZT film displayed higher strength compared with PZT film without CNTs after the laser sintering while using less sintering energy. Thus, laser sintering can be effectively used to enhance the piezoelectric and mechanical properties of CNT/PZT films, which can be used in various sensing applications.

Numerical thermal analysis of armchair (6,6) and zig-zag (12,0) carbon nano-tubes (CNTs)

In this study, the thermal behaviour of small-sized single-atom CNTs was examined. CNTs are composed of crystals that form a nanostructure with different geometric shapes by arranging them in different ways according to the length-diameter ratio. Due to the mechanical, electrical, and thermal properties of CNTs, the thermal conduction of CNT materials is critical in controlling the performance and stability of CNTs. CNTs, which are low-dimensional materials with a single atomic layer thickness, have excellent thermal conductivity. According to the simulation technique in ANSYS, CNTs containing the same number of atoms and bonds were developed. The heat transfer of different structures of CNTs in armchairs (6,6) and zig-zag (12,0) were compared. A comparison of zig-zag and armchair CNTs thermal behaviour shows that zig-zag CNTs lattice structure has more advantages than armchair CNTs lattice structure by heat transfer. Highlights In this study, finite element-based thermal analysis of single and double-walled armchair and zig-zag carbon nano-tubes (CNTs) using the lattice method was investigated. A simulation technique was developed and applied in the ANSYS program for single and double-walled carbon nanotubes (CNTs). Armchairs (6,6) and zig-zag (12,0) CNTs in different lattice structures with equal atomic numbers and bond numbers are modelled according to different diameters and length ratios. The CNTs, which have the same material properties as the trays placed at both open ends of the pipes, are kept at different temperature values, and conduction heat transfer behaviour is investigated for certain temperature values. According to the investigated heat conduction behaviour of zig-zag and armchair CNTs, the lattice structure of the zig-zag carbon nano-tubes is more advantageous in terms of heat conduction than the cage structure of armchair CNTs, and it transmits heat faster than the armchair CNTs.

Effect of SW-CNT Diameter on Polymer Degradation and Resistance of Polystyrene/SW-CNTs Composites Induced by γ-Irradiation

The outstanding electrical, mechanical, and thermal properties of carbon nanotubes (CNTs) make them promising materials for a wide range of applications. Numerous theoretical and experimental studies on the diameter-dependent properties of single-walled carbon nanotubes (SW-CNTs) exist. The incorporation of carbon nanotubes into commercial polymers can alter the properties of both materials. Herein, we demonstrate polystyrene/SW-CNT composites with different diameters to check property changes, including radiation-protective characteristics under various doses of gamma radiation. The intrinsic glassy state of polystyrene disappeared owing to the introduction of SW-CNTs into the polymer-polymer chain. In addition, when 1.3 nm diameter SW-CNTs were introduced, the Fourier-transform infrared spectroscopy peaks for alkyl aryl ethers were observed at 10–60 kGy of gamma irradiation. In this study, the different phenomena that occur when polystyrene/SW-CNT composites are formed with different SW-CNT diameters (0.78 nm and 1.3 nm) were investigated via systematic analyses.

Thermally induced fracture analysis of CNT reinforced FG structures with multiple discontinuities using XIGA

In this paper, the authors have employed XIGA to perform the fracture analysis of carbon nanotubes (CNT) reinforced functionally graded (FG) structures with discontinuities subjected to a coupled loading condition (thermo-mechanical load). For the first time, XIGA is used to analyse cracked CNT reinforced FG structures. The exponential rule is supposed to regulate the material property gradation in FG (which is made up of metal (Ti–6Al–4V) and ceramic (ZrO2)) structures. Several micromechanics models are utilized for evaluating the equivalent mechanical and thermal properties of CNTs (SWCNT and MWCNT) reinforced FG structure. To capture the discontinuity along the singular fields near the crack tip and the crack face, appropriate enrichment functions are used. Investigations are performed to estimate the effects of inclusions and holes on the SIFs of FG structures reinforced with CNT. Also, the effect of mechanical properties (Young’s modulus) of inclusion and percentage content of CNTs (SWCNT & MWCNT) on SIFs is explored. Furthermore, the authors have investigated the effect of different loading conditions on the SIFs.

Heat Transfer of SWCNT-MWCNT Based Hybrid Nanofluid Boundary Layer Flow with Modified Thermal Conductivity Model

Thermal conductivity is one of the important thermophysical property of nanofluid in enhancing heat transfer. To analyse heat transfer in boundary layer problems thermal diffusivity coefficient along with embedded nano particle thermophysical values will be used via various thermal conductivity models. Many thermal conductivity models are being utilised for theoretical analysis of heat transfer behaviour such as Maxwell model, Hamilton crosser model etc. In this current communication we are analysing the thermal properties of carbon nanotubes by embedding modified Xue thermal conductivity model. Momentum, energy and nano particle volume fraction equations are turned into differential equation of single variable by using appropriate similarity transformation and solved by numerical scheme shooting method. Skin friction, Nusselt numbers for mono particle nanofluid, hybrid nanofluid are computed for distinct physical parameters and it is observed that heat transfer rate is improved with SWCNT-MWCNT as compared to SWCNT.

An integrated XFEM modeling with experimental measurements for optimizing thermal conductivity in carbon nanotube reinforced polyethylene

The present paper investigates the thermal properties of carbon nanotube reinforced polyethylene and specifically its potential as highly conductive material. To this end, an integrated approach is proposed combining both numerical and experimental procedures. First, in order to study conductive heat transfer in two-phase materials with imperfect interfaces, a detailed numerical model is developed based on the extended finite element method, where material interfaces are modeled using the level set method. The thermal conductance at the interface of the carbon nanotubes and the polymer matrix is considered to be an unknown model parameter, the value of which is obtained by utilizing a series of experimental measurements of the composite material’s effective conductivity. The interfacial thermal conductance parameter value is inferred by calibrating the numerically predicted effective conductivity to the series of the corresponding experimental measurements. Once this parameter is estimated, the data-informed model is subsequently employed to provide reliable predictions of the effective conductivity of the composite for various weight fractions and configurations of carbon nanotubes in the parent material. Furthermore, microstructural morphologies that provide upper limits on the effective conductivity of the composite are identified via sensitivity analysis, demonstrating its potential as a highly conductive material.

Mechanical and thermal properties of carbon nanotubes in carbon nanotube fibers under tension-torsion loading.

In carbon nanotube fibers (CNFs) fabricated by spinning methods, it is well-known that the mechanical and thermal performances of CNFs are highly dependent on the mechanical and thermal properties of the inherent CNTs. Furthermore, long CNTs are usually preferred to assemble CNFs because the interaction and entanglement between long CNTs are effectively stronger than between short CNTs. However, in CNFs fabricated using long CNTs, the interior carbon nanotubes (CNTs) inevitably undergo both tension and torsion loading when they are stretched, which would influence the mechanical and thermal performances of CNFs. Here, molecular dynamics (MD) simulations were carried out to study the mechanical and thermal properties of individual CNTs under tension-torsion loading. As for mechanical properties, it was found that both the fracture strength and Young's modulus of CNTs decreased as the twist angle α increased. Besides, step-wise fracture happened due to stress concentration when the twisted CNTs are stretched. On the other hand, it could be seen that the thermal conductivity of CNTs decreased as α increased. This work presents the systematic investigation of the mechanical and thermal properties of CNTs under tension-torsion loading and provides a theoretical guideline for the design and fabrication of CNFs.

Experimental assessment on machinability performance of CNT and DLC coated HSS tools for hard turning

The present work investigates the deposition of carbon nanotubes (CNT) over the HSS tool. Also, it assesses the machining capacity of the coated tool with respect to some of most important aspects of the machinability, such as surface roughness, cutting tool-tip temperature, cutting forces, tool wear, and service life. The Plasma Enhanced Chemical Vapour Deposition (PECVD) technique was used to deposit CNTs over the substrate. To recognize the dense deposition of CNTs, microstructural analysis was carried out through Scanning Electron Microscopy (SEM) and Raman spectroscopy. Further, a scratch test was embedded to validate the bonding strength of the covered layer substrate. Machining experiments were performed using CNT and Diamond-Like Carbon (DLC) coated tools. The analysis of experimental outcomes for three different cutting environments shows that the CNT coated tool represent a viable candidate for machining of harder materials. We have observed a dramatic reduction of the cutting tool tip temperature and cutting forces due to the excellent mechanical and thermal properties of CNTs. Indeed, the CNT coated tools prove their suitability when compared with the DLC coated tools. The analysis of tool wear demonstrated a much lower wear condition for CNTs tools when comparing to DLC coating one. This was translated in longer tool life for the CNT coated tool, which was about 28 min longer with only marginal failure under high cutting conditions when comparing to DLC one.

Experimental evaluation of machinability performance of CNT coated HSS tool during turning of titanium alloy

The present research deals with the deposition of carbon nanotubes (CNT) over the HSS tool, and to evaluate the machining performance of the coated tool with respect to the important machinability aspects like cutting tip temperature, cutting forces, surface roughness and tool wear and life. The plasma enhanced chemical vapour deposition (PECVD) technique was employed to deposit CNTs over the substrate. Microstructural investigations through SEM and Raman spectroscopy were carried out to acknowledge the dense deposition of CNTs. Scratch test was also performed to validate the bonding strength of the coated layer with the substrate. Machining experimental results under three different cutting conditions, concluded that the CNT coated tool is the right potential candidate for turning tougher materials. Drastic depletion in cutting tip temperature and cutting forces to the extent of 70 to 80 % was observed for coated tool due to the excellent mechanical and thermal properties of CNTs. However, there was no significant effect of coating to influence the surface roughness at a lower level of cutting conditions, but considerable improvement has been observed at elevated cutting condition. The tool wear and life analysis explored the steady improvement to a remarkable extent. Very specifically, under elevated machining conditions, tool life investigations concluded the fact that the CNT coated tool has a tool life of more than 60 minutes with negligible failure.

Flexible omnidirectional terahertz imaging inspection chips by controlling the optical and thermal properties of carbon nanotubes

Flexible omnidirectional terahertz imaging inspection chips by controlling the optical and thermal properties of carbon nanotubes

Mechanical, Electrical, and Thermal Properties of Carbon Nanotube Buckypapers/Epoxy Nanocomposites Produced by Oxidized and Epoxidized Nanotubes.

High volume fraction carbon nanotube (CNT) composites (7.5–16% vol.) were fabricated by the impregnation of CNT buckypapers into epoxy resin. To enhance the interfacial reaction with the epoxy resin, the CNTs were modified by two different treatments, namely, an epoxidation treatment and a chemical oxidation. The chemical treatment was found to result in CNT length severance and to affect the porosity of the buckypapers, having an important impact on the physico-mechanical properties of the nanocomposites. Overall, the mechanical, electrical, and thermal properties of the impregnated buckypapers were found to be superior of the neat epoxy resin, offering an attractive combination of mechanical, electrical, and thermal properties for multifunctional composites.

Investigation of the Optical, Morphological and Thermal Properties of Carbon Nanotubes Synthesized by Nebulized Spray Pyrolysis

Multiwalled carbon (C) nanotubes (CNTs) were synthesized by nebulized spray pyrolysis of xylene and ferrocene in a horizontal tube furnace at atmospheric pressure. The reaction temperature and the ...

Thermal conductance bottleneck of a three dimensional graphene-CNT hybrid structure: a molecular dynamics simulation.

Three dimensional (3D) graphene-CNT hybrid structures (GCNTs) are promising materials for applications including capacitors and gas storage and separation devices, however until now their thermal conductance mechanism has scarcely been studied. These hybrid nanomaterials are particularly suitable as next-generation thermal interface materials due to the excellent thermal properties of carbon nanotubes and single atomic layer graphene. In this paper, the out-of-plane thermal conductivities of GCNTs, graphene nanomesh (GNM), and graphene sheets are investigated using molecular dynamics (MD) simulations which apply the Green-Kubo method. Distinct from GNMs and graphene sheets, the GCNTs exhibit a relatively high out-of-plane thermal conductivity, stemming from the CNTs' ability to accelerate the energy flow. However, the GCNT out-of-plane thermal conductivity is still far lower than that of pristine graphene due to extreme phonon localizations, which are concentrated on the graphene-CNT junction regions as evidenced by the participation ratio, phonon vibrational density of states, and overlap energy. This study provides microscopic insight into the GCNT heat transfer mechanism and offers design guidelines for application of GCNTs in thermal management devices.

Awareness: potential toxicities of carbon nanotubes.

Carbon nanotubes belong to a class of tiny tubular structures composed of carbon atoms. These carbon atoms are arranged in a honeycomb-type (nano)tube and their structure and the strength of the bonds between the atoms provide exceptional physicochemical properties. Carbon nanotubes consist of either single graphene cylinders [single-walled carbon nanotube (SWCNT)] with an outer diameter of 1–3 nm, or multiple graphene cylinders arranged in concentric layers [multi-walled carbon nanotube (MWCNT)] with diameters ranging from 10 to 200 nm and a length from a few hundreds of nano-meters to several tens of micro-meters. The unique physicochemical, mechanical (strength/stiffness), electrical, and thermal properties of carbon nanotubes have contributed to an increased use of these materials in the electronics, aerospace, computer, and pharmaceutical industries.

Role of grain boundaries on the thermal properties of carbon nanotubes

Abstract Carbon nanotubes (CNTs) do not exist in their pristine form naturally and they have certain types of defects. In comparison to all other types of defects, grain boundary (GB) defects may affect the thermal conductivity of CNTs significantly and the study of thermal properties of CNTs containing GB is essential. In this work, Fourier’s law and Reverse Non-Equilibrium Molecular Dynamics (RNEMD) method have been applied on CNTs based on adaptive intermolecular reactive empirical bond order force field potential to calculate their thermal conductivities. The current results reveal the deviation of thermal conductivities of defective CNTs pristine ones.

A Meta-study on the Thermal Properties of Carbon Nanotubes in Thermal Interface Materials

Computer Integrated Circuit (IC) microprocessors are becoming more powerful and densely packed while cooling mechanisms are seeing an equivalent improvement to compensate. A significant limit to cooling performance is thermal transfer between die and heatsink. In this meta study we evaluate carbon nanotube (CNT) thermal interface materials (TIMs) in order to determine how to maximise thermal transfer efficiency. We gathered information from over 15 articles focused on the thermodynamic parameters of CNT TIMs from databases such as Scopus, IEEE Xplore and ScienceDirect. Articles were filtered by key words including ‘carbon nanotubes’ and ‘thermal interface materials’ to identify scientific articles relevant to our research on TIMs. From our meta study we have found that enhancing CNTs will provide the best improvement in TIMs. The parameters analysed to determine TIM performance included thermal resistance, thermal conductivity and the effect of CNT concentration on computer operation time. Through our investigation we understood that increasing the concentration of CNT from 0 to 2 wt % increases the operation time from 75 seconds at 66°C to 200s at 63°C as well as increasing the thermal conductivity by 1.82 times for the AS5 thermal paste with 2 wt % CNT. Furthermore, CNT TIM pastes with less thickness have a lower thermal resistance of 0.4 K/W. However not all these parameters have been tested with computer chips. This means that in order to increase current heat transfer efficiency limit, we must integrate these parameters into experimental models.
 Keywords: Thermal Interface Material; Thermal Paste; Carbon Nanotubes; Thermal Transfer Efficiency; Integrated Circuit; Heat Sink; Heat Dissipation.

Nano-composite multi-wall carbon nanotubes using poly(p-phenylene terephthalamide) for enhanced electric conductivity

Because of unique brilliant electrical, mechanical as well as thermal properties of carbon nanotubes, they have a broader application in nano-composite fields with the energy and advanced science area. In this study, we have reported the specific and sequential functionalization approach for the systematic modification of multi-walled carbon nanotubes with poly(p-phenylene terephthalamide) (PPTA) that was prepared via polycondensation method. A novel hybrid material of pristine PPTA/MWNTs nano-composite was designed to produce uniform nanofibers with diameters range over 17–29 nm for electercal conductivity application. A series of PPTA based nano-composite materials were prepared using an ultrasonic bath with various ratios of pristine multi-wall carbon nanotubes and COOH- Multi-wall carbon nanotubes (0.5, 1.0 and 1.5). The dispersion of multi-wall carbon nanotubes has been inspected by several analyses, Raman’s spectroscopy, which indicated the presence of different peaks characteristic. The Fourier-transform infrared spectroscopy analysis confirmed the nano-composites were existed in the materials morphology as desired. In addition, the thermal stability of nano-composites was upgraded after with the successful addition multi-wall carbon nanotubes (0.5%), the electrical conductivity was enhanced in the range of 10−8 because of the coupling of PPTA compared with original materials. Based on our finding, we believe that PPTA/multi-wall carbon nanotubes nano-composite materials can act as widespread fillers to enhance the electrical conductivity of novel nano-composite materials for energy and advanced applications.

Mechanical and thermal properties of carbon nanotube- and graphene-glass fiber fabric-reinforced epoxy composites: A comparative study

This study was focused on the comparative effect of tube- and sheet-like nanocarbons on the structure–property relationships of fiber-reinforced composites. Graphene nanosheets and multi-walled carbon nanotubes (MWCNTs) were dispersed into commercial glass fiber fabric (Gf) to obtain multiscale graphene-Gf- and MWCNT-Gf-reinforcing materials, respectively, followed by a vacuum-assisted resin infusion process. The influence of MWCNTs and graphene on the mechanical and thermal performance of multiscale composites were investigated. The experimental results indicated that oxidized MWCNTs or graphene could ensure excellent dispersibility on the fiber surface, and ultimately enhance the mechanical properties and thermal stability of the resultant composites. Graphene oxide (GO), with a wrinkled and roughened texture, was shown to be superior to MWCNTs in terms of toughening the fiber/matrix interface and delaying the deformation or failure of the epoxy matrix. Under the same dosage of nanocarbons, the interlaminar shear strength of GO-Gf-reinforced composites (GO-GfCs) was raised by approximately 12%, and the relevant onset thermal-decomposition temperature was increased by > 11℃, compared with carboxyl MWCNT-Gf-reinforced composites (Mc-GfCs). Meanwhile, the GO-GfCs exhibited superior static and dynamic mechanical properties compared to those of Mc-GfCs.