Mass Fraction Of Carbon Nanotubes Research Articles

Effect of functionalized carbon nanotube on cement mortar: From experiment to DFT research

In this paper, functionalized nanotube-reinforced cementitious composites were prepared, and the mechanical property test results showed that the 28d flexural strength of the composite was increased by 41.58% at a hydroxylated carbon nanotube mass fraction of 0.08[Formula: see text]wt.% compared to the original cement mortar. Carboxylated carbon nanotubes with a mass fraction of 0.02%, on the other hand, increased the 28d compressive strength by 99.12%. Probing the effect of the presence of functional groups on carbon nanotubes on the CNT/C–S–H interface by first principles. The results showed that the shear strengths (11.392[Formula: see text]MPa and 14.130[Formula: see text]MPa) of hydroxylated carbon nanotubes and plain carbon nanotubes at the interface with cementitious (CNT-OH/CSH and CNT/CSH) were lower than the shear strengths (21.584[Formula: see text]MPa) of carboxylated carbon nanotubes at the interface with cementitious (CNT-COOH/CSH). The adsorption of functional groups on carbon nanotubes changes the electron distribution on the surface of carbon nanotubes. The introduction of carboxyl groups exacerbates the charge transfer between carbon nanotubes and cementitious groups and promotes the generation of solid chemical bonds. This is the reason that carboxylated nanotubes added as reinforcement to cement mortar give better strength to the composite than hydroxylated nanotubes.

Nanoscale Dispersion of Carbon Nanotubes in a Metal Matrix to Boost Thermal and Electrical Conductivity via Facile Ball Milling Techniques.

Carbon nanotube (CNT)/metal composites have attracted much attention due to their enhanced electrical and thermal performance. How to achieve the scalable fabrication of composites with efficient dispersion of CNTs to boost their performance remains a challenge for their wide realistic applications. Herein, the nanoscale dispersion of CNTs in the Stannum (Sn) matrix to boost thermal and electrical conductivity via facile ball milling techniques was demonstrated. The results revealed that CNTs were tightly attached to metal Sn, resulting in a much lower resistivity than that of bare Sn. The resistivity of Sn with 1 wt.% and 2 wt.% CNTs was 0.087 mΩ·cm and 0.056 mΩ·cm, respectively. The theoretical calculation showed that there was an electronic state near the Fermi level, suggesting its electrical conductivity had been improved to a certain extent. In addition, the thermal conductivity of Sn with 2 wt.% CNTs was 1.255 W·m-1·K-1. Moreover, Young's modulus of the composites with CNTs mass fraction of 10 wt.% had low values (0.933 MPa) under low strain conditions, indicating the composite shows good potential for various applications with different flexible requirements. The good electrical and thermal conductive CNT networks were formed in the metal matrix via facile ball milling techniques. This strategy can provide guidance for designing high-performance metal samples and holds a broad application potential in electronic packaging and other fields.

Effect of carbon nanotube mass fraction and distribution on microwave heating effect of rubber composites

Effect of carbon nanotube mass fraction and distribution on microwave heating effect of rubber composites

Ultrafast-responsive carbon nanotube-grafted fibre textiles

Direct grafting of carbon nanotubes (CNTs) on fibre textiles is a promising strategy to functionalize conventional fibre-reinforced polymer composites with extra merits such as integrated sensing capability. In this study, CNTs are in situ grafted on glass fibre (GF) via chemical vapor deposition at a low synthesis temperature (500 °C). By regulating the mass fractions of CNTs, the quantum tunnelling effect can be triggered among CNT nanoparticles, with which the CNT-grafted GF textiles manifest high sensitivity to structure-guided ultrasonic waves in a frequency regime from 175 to 375 kHz. With ignorable degradation in mechanical attributes due to this direct grafting processing as affirmed by ASTM-complied tests (ASTM C1557 and D3039), the CNT-grafted GF textiles demonstrate the great potential in developing hybrid functional composites.

An experimental study of spectral radiative properties of multi-walled carbon nanotube coating for heat dissipation

Thermal management serves a crucial role in the stable operation of electronic equipment due to its miniaturization and functionality. Enhancing radiation heat transfer through heat dissipation coating is an effective method to improve the heat dissipation performance of electronic devices in thermal management of narrow space. In this paper, we employed the high emissivity property of multi-walled carbon nanotubes to improve the radiative heat dissipation performance of the coating. The effect of the distribution of multi-walled carbon nanotubes on the emissivity of the coating was studied with the finite-difference time-domain method. The emissivity of the coating with random distribution of multi-walled carbon nanotubes was found to be greater than that of the coating with vertical distribution of multi-walled carbon nanotubes. In order to further investigate the radiative properties of randomly distributed multi-walled carbon nanotube coatings, we experimentally investigated the effect of coating thickness and multi-walled carbon nanotube mass fraction on the spectral radiative properties of the coatings. We obtained the relationships between coating thickness, carbon nanotube mass fraction and coating radiation power. The data can provide some guidance for the regulation of radiation power of heat dissipation coatings and the selection of common coating processes. The maximum average emissivity and radiation power of the multi-walled carbon nanotube coating is 0.97, and 491.6 W m−2, respectively.

Study of flexible piezoresistive sensors based on the hierarchical porous structure CNT /PDMS composite materials

Flexible piezoresistive sensors (FPS) are important components of wearable electronics for human-machine interaction, human physiological signal monitoring and electronic skin. In this work, carbon nanotube (CNT)-polydimethylsiloxane (PDMS) (abbreviated as CP) composite materials with hierarchical porous structures were prepared by a facile solvothermal method. The electrical conductivity and mechanical elasticity of the porous structure CP composite materials can be separately tuned by varying the CNT mass fraction and PDMS composition ratio, respectively. A flexible piezoresistive sensor using porous structure CP composite materials as the sensing material was designed and fabricated. The optimized sensor exhibits a sensitivity of 0.59 kPa −1 in the pressure ranges of 0–260 kPa, a low detection limit of 12 Pa, a fast response time of 25 ms and outstanding cycling stability over 1,700 cycles. Such sensor design can be integrated into flexible wearable electronic devices for physiological signal monitoring in real-time. • The hierarchical porous structure CNT/PDMS composite materials were prepared by solvothermal method. • Mechanical and electrical properties of CNT/PDMS composite materials can be adjusted by changing the process parameters. • Sensing mechanism and sensor performance of FPS based on CNT/PDMS composite materials were studied. •Application of FPS for recording human respiratory volume and rate and human activity were examined.

Buckling and free vibration analysis of randomly distributed CNT reinforced composite beam under thermomechanical loading

In this study, the buckling and free vibration characteristics of three-phase randomly distributed carbon nanotube (CNT) reinforced fiber composite (RD-CNTRFC) beams subjected to in-plane compressive loadings and thermal environment are discussed in-depth through a semi-analytical approach. Displacement-based governing equations of motion are derived using Lagrange equation considering higher-order shear deformation theory (HSDT). The effective material properties of RD-CNTRFC are determined in two stages; firstly, effective properties of hybrid matrix (CNTs + Polymer) are evaluated using the Eshelbhy-Mori-Tanaka approach. Finally, overall effective properties of CNTRFC are estimated by implementing different homogenization techniques. The influences of temperature-dependent material properties and CNT-agglomeration are included in the derived formulation. The buckling loads and natural frequencies of RD-CNTRFC beams are computed using a typical eigenvalue solution. The influence of various boundary conditions, CNT mass fraction, CNT-agglomeration, length-to-thickness ratio, and various ply sequences are also addressed.

Effects of carbon nanotubes and sintering parameters on microstructure and properties of PCD

Polycrystalline diamond (PCD) was sintered from onion-like carbon (OLC) mixed with multi-walled carbon nanotube (MWCNT) at 5.5 GPa/1100–1300 °C/5–20 min holding time, in which OLC was generated by vacuum annealing of nano-diamond. Structures, morphologies, and properties of composites were characterized by X-ray diffraction, field emission scanning electron microscope, high-resolution transmission electron microscopy, and hardness measurement. The purposes of this paper were to lower the temperature of OLC conversion into PCD and optimize the performance of the PCD. The influence of sintering parameters on the microstructure and properties of PCD and the change of MWCNT and OLC structure in high-pressure and high-temperature (HPHT) were studied. Finally, when the mass fraction of carbon nanotubes is 10 %, the optimal process conditions were as follows: sintering pressure 5.5 GPa, temperature 1150 °C, holding time 20 min, sintering hardness was 18.84 GPa, and conversion rate of OLC to diamond was 25.96 %. Under the influence of HPHT and surrounding OLC, the MWCNT tends to be transformed into spheroids, while the structure of the OLC/MWCNT binding zone is graphite. This work not only provided a theoretical basis for the study of carbon nanotubes but also provided reasonable parameters for the synthesis of PCD.

Effect of carbon nanotubes on melting latent heat of paraffin wax: An experimental and simulated research

Paraffin wax (PW) is a typical organic phase change material (PCM) widely used in energy storage systems, and carbon nanotubes (CNT) are general additives to improve thermal conductivity. The latent heat of PW with a low mass fraction of CNT is explored in experiments and simulations. Both experiments and simulations show additives will decrease the melting latent heat of the material. For experiments, the lowest melting latent heat is 177.2 J/g, with a decrease of 1.6 % compared to pure PW. Besides the melting temperature barely changes with the mass fraction (about 325 K for both pure PW and composite PCM). The experimental results also show CNT is covered by PW uniformly, and CNT in materials keeps clusters and knots. The simulation shows that the decreasing melting temperature is caused by the energy change between PW and CNT. Moreover, the dense layer is not the reason for the decreasing latent heat. The latent heat of the material is affected by the energy change between PW and CNT. The final latent heat is closely connected to the sensible heat of the material. For PW adding a low mass fraction of CNT in normal atmospheric pressure, the final latent heat would be high if a material can keep a high melting temperature and high constant-pressure specific heat.

The effects of rotation on the frequencies and critical speed of CNTs/fiber/polymer/metal laminates cylindrical shell

This work focuses on the frequencies of rotating carbon nanotubes (CNTs)/fiber/polymer/metal laminates (CNTFPMLs) thin circular cylindrical shell. The cylindrical shell is studied on the basis of Love’s first approximation shell theory with simply supported boundary condition. In this manuscript, Eshelby-Mori-Tanaka is used to define the modulus of carbon nanotubes reinforced composites (CNTRCs) cylindrical shell. In addition, fibers can be reinforced using the obtained matrix by means of extended rule of mixture. The influence of various parameters for example characteristics of fiber phase material, such as circumferential and axial wave numbers, lay-ups, metal volume fraction, composite volume fraction and CNTs mass fraction on the frequencies of rotating CNTFPMLs cylindrical shell have been studied. The outputs illustrated by growing rotational speed, the frequencies of CNTFPMLs cylindrical shell change differently for different fiber volume fractions. Also, the backward and forward frequencies of functionally graded ( F G ) - X and F G - O distributions are more and less than the uniformly distributed ( U D ) for rotational speed equals to 1, respectively, while this process is reversed for rotational speed equals to 5. In 10 and 20 rotational speeds, while the frequencies of backward and forward modes for F G - X distribution are more and less than the U D , respectively, but this procedure is reversed in F G - O distribution.

A New Composite Phase Change Material for Cold and Heat Storage and Its Application

In today's society, energy consumption is growing at an alarming rate. Because of the huge economic benefits brought by traditional industries such as non renewable energy and fossil fuel power generation, people have to study them. The phase-change heat storage materials are widely used in the condensation heat storage due to their high temperature, low density and environmental protection. This paper considers the advantages, disadvantages and application scope of the new energy storage equipment based on the phase-change storage characteristics, and proves through experiments that under certain conditions, the appropriate solid-liquid ratio and the degree of substitution of different components are conducive to improving the performance of the composite storage heat exchanger. In this paper, a new composite phase change material for cold storage and heat storage is tested. The test results show that, because the carbon nanotubes added in the composite phase change material have no latent heat contribution in the whole phase change process, the phase change enthalpy of the composite phase change material will inevitably decrease with the increase of the carbon nanotube mass fraction.

О влиянии углеродных нанотрубок на физико-механические свойства полипропилена

One of the most interesting and promising materials of our time is carbon nanotubes. Most applications of nanotubes are associated with the possibility of combining them with other materials in the form of alloys, mixtures, composites or hybrid materials. In particular, the idea of including carbon nanotubes as a filler in various polymer-based matrices (for example, traditional polymers such as thermoplastics, thermosetting materials or elastomers, as well as conjugated polymers) for the formation of polymer/carbon nanotube nanocomposites has revolutionized materials science and engineering. The introduction of carbon nanotubes into the composite structure affects the structure and properties of the polymer binder, as well as the composite material as a whole. Currently, there are no experimental developments on the basis of which the introduction, distribution and stabilization of the dispersion of carbon nanotubes in polymer composites would be implemented in industrial technology. The development of the most effective methods for introducing carbon nanotubes into polymer materials and determining their effect on the physical and mechanical properties of polymers is an urgent and priority task. It is possible that these methods will be able to find application in the industrial production of polymer composite materials intended for use and operation in various extreme conditions (whether it is high temperatures, erosion, high force exposure or highly acidic/highly alkaline environments). The main physical and mechanical properties of polypropylene samples saturated with carbon nanotubes taken at different concentrations (0; 0.01; 0.05 and 0.1 wt. %), who found that the addition of CNT in large quantities negatively affects the tensile and bending strength limits, which may be associated with an increase in the degree of heterogeneity of the structure and the appearance of large agglomerates, which will be points of stress concentration. With an increase in the mass fraction of carbon nanotubes in the polymer nanocomposite, the tangent of the dielectric loss angle increases, which leads to better conductivity of the sample containing a larger number of nanotubes. This may be due to the fact that nanotubes become conductors of electric current in the volume of the polymer matrix.

Construction of carbon nanotubes/bismaleimide composite films with superior tensile strength and toughness

Carbon nanotubes (CNTs) have been considered as promising reinforcements for various composites due to their excellent mechanical properties. However, preparation of high-performance CNT/resin composites still suffers from bad dispersion, low fraction, and poor alignment of CNTs and their weak bonding with the resin matrix. Herein, we report an effective strategy towards preparing CNT/Bismaleimide (BMI) composite films with excellent mechanical properties. Firstly, from floating catalytic spray pyrolysis, CNTs are deposited on a water soluble substrate as a thin film to maintain their original microstructures. The films are then stacked layer by layer and pulled in tension with the substrate dissolved in water. The pristine stacked films are immersed in BMI solutions of different concentrations and stretched to different strains for simultaneous CNT reorientation and resin infiltration. The films are finally pressed at low temperature for resin permeation and redistribution and high temperature for resin curing. The determining factors such as the alignment and mass fraction of CNTs and the distribution of BMI resin in the composite film can be easily tailored. Benefiting from the resultant excellent CNT alignment, high CNT content (61.4 wt%), and uniform distribution of the resin between CNTs, the composite film can achieve excellent mechanical properties, including a tensile strength of 4.18 GPa, elongation at break of 4.35%, Young's modulus of 145 GPa, and toughness of 94.2 J cm−3. Such a strength and toughness are superior to those for the CNT composites published in the literature so far.

Construction of wood-based cellulose micro-framework composite form-stable multifunctional materials with thermal and electrical response via incorporating erythritol-urea (thiourea)-carbon nanotubes

In this study, two kinds of form-stable multifunctional materials with thermal and electrical response (FPCMs: DP-E7U3-CNT, DP-E7T3-CNT) are composed of wood-based honeycomb-like celluloses micro-framework (DP), carbon nanotubes (CNT), erythritol-urea (E7U3) or erythritol-thiourea (E7T3). In FPCMs, DP acts as a skeleton structure to seal E7U3 and E7T3 and provide more pathways for heat conduction. The CNT acts as an extended surface to further improve thermal conductivity. FE-SEM showed that the honeycomb-like pore structure of DP was completely filled with E7U3, E7T3 and CNT. FTIR and XRD analysis show that there is only a combination of physical interactions between the components of FPCMs. DSC curves and thermal conductivity analysis results show that DP-E7U3-1.5CNT and DP-E7T3-1.5CNT with the mass fraction of carbon nanotubes (1.5 wt%) have the highest latent heat values (230.3 J/g, 272.2 J/g) and thermal conductivity (0.9832 W/(m·K), 0.9363 W/(m·K)). Both DP-E7U3-1.5CNT and DP-E7T3-1.5CNT exhibit high latent heat retention and thermal stability after 100 heating-cooling cycles. In addition, DP-E7U3-1.5CNT and DP-E7T3-1.5CNT show excellent performance in light-heat energy conversion-storage, actual latent heat storage and release, thermal and electrical response performance, which make it has great potential to be multifunctional materials with thermal storage sand electrical response.

Microstructure and compression behavior of in-situ synthesized Ti2AlC reinforced Ti-48Al-2Cr alloy with carbon nanotubes addition

Different contents of carbon nanotubes (CNTs) were added into Ti-48Al-2Cr alloys (at%) to obtain in-situ synthesized Ti2AlC particles by vacuum arc melting. The effect of the CNT content in the range of 0–1.5 wt% on the microstructure and compression behavior were systematically investigated, especially the controlling mechanism of the Ti2AlC phase. The experimental results showed that the volume fraction of the Ti2AlC phase increases with increasing CNT content. The lamellar spacing of the microstructure and the length-diameter ratio of the Ti2AlC phase decreases as the CNT content increases. The compressive strength and strain first increase and then decrease with increasing CNT content. When the mass fraction of CNT is 1.0, the maximum compressive strength is 1904.25 MPa and the maximum strain is 9.84%, respectively, which is 37.9% and 53.9% higher than that of the Ti-48Al-2Cr alloy. The controlling mechanism of mechanical properties of Ti-48Al-2Cr-xCNT alloy is the combination of fine grain strengthening and γ phase weakening.

Agglomeration effects on free vibration characteristics of three-phase CNT/polymer/fiber laminated truncated conical shells

This paper investigates the effect of carbon nanotubes (CNTs) agglomeration on the free vibration characteristics of three-phase CNT/polymer/fiber laminated truncated conical shells surrounded by an elastic foundation. The shell material is considered to be composed of a CNT-reinforced polymer enriched by the oriented reinforcing fibers. The material density and the effective elastic properties are calculated based on the rule of the mixture, and the Eshelby–Mori–Tanaka scheme along with Hahn's homogenization technique, respectively. The third-order shear deformation theory (TSDT) is used for the analysis of the shear flexible shell and the foundation is modeled based upon the Winkler-Pasternak theory. A set of governing equations are derived using Hamilton's principle, and solved numerically by the generalized differential quadrature method (GDQM). After confirming the convergence and accuracy of the results, a parametric study is carried out to examine the influences of various parameters on the natural frequencies of the three-phase CNT/polymer/fiber laminated truncated conical shells such as boundary conditions, circumferential mode number, the geometrical parameters including the ratios of thickness/length to radius, and the semi-vertex angle, the material parameters contain the mass fractions of CNTs and fibers, chiral numbers as well as the agglomeration characteristics of CNTs, and finally the foundation parameters including the Winkler stiffness and shearing layer stiffness.

Nonlinear damped vibrations of three-phase CNT-FRC circular cylindrical shell

This study presents a semi-analytical solution of nonlinear vibrations of circular cylindrical shells made of carbon nanotube (CNT) fiber-reinforced composite (CNT-FRC). Vibrations are produced by a radial harmonic force and viscous structural damping is considered. The effective properties of a lamina of the CNT-FRC shell are evaluated in two steps. The elastic properties of randomly distributed CNTs in a polymeric matrix (i.e., hybrid matrix) are computed by the Eshelby-Mori-Tanaka/Voigt scheme to consider the CNTs agglomeration effect in the hybrid matrix. Then, the resulting hybrid matrix is reinforced with aligned fibers in order to prepare the lamina of the CNT-FRC shell; its effective properties are estimated by the Halpin Tsai homogenization approach. The CNT-FRC shell is modelled incorporating the von Kármán geometric nonlinearity and first-order shear deformation theory (FSDT). The nonlinear governing partial differential equations (PDEs) of the CNT-FRC shells are derived by the Hamilton’s principle. These PDEs are discretized into ordinary differential equations (ODEs) by using the Galerkin’s method. The ODEs are solved by incremental harmonic balance method (IHB) in conjunction with the arclength continuation method to obtain the frequency-amplitude response of the shell. The effect of different types of CNT agglomeration models, CNT mass fraction, agglomeration parameters and stacking sequence of laminates on the frequency-amplitude curves corresponding to forced and free nonlinear vibrations of the CNT-FRC shell are studied in detail.

Critical buckling load of honeycomb sandwich panels reinforced by three-phase orthotropic skins enhanced by carbon nanotubes

The buckling analyses illustrated in this research aim to provide useful results for the design and application of sandwich plates with a honeycomb core and three-phase orthotropic skins, which are reinforced by both carbon nanotubes (CNTs) and straight oriented fibers. A multiscale approach is developed to this aim, which is based on the Eshelby-Mori-Tanaka scheme and the Hahn homogenization technique. The outcomes are presented in terms of critical buckling loads for different boundary conditions, lamination schemes, fiber orientation and mass fraction of CNTs, in order to prove that all these elements represent fundamental design parameters in the analysis, manufacturing and behavior of these sandwich plates. The theoretical framework is based on the Reissner-Mindlin theory for laminated plates and on the von Kármán hypothesis as far as the nonlinear terms are concerned. The kinematic model includes the Murakami’s function to deal with such peculiar mechanical configurations, which is required to capture the zig-zag effect due to the different mechanical properties of the core and the external skins. The numerical approach and the theoretical methodology are validated by means of the comparison with the experimental and the theoretical results available in the literature.

Effect of CNTs Additives on the Energy Balance of Carbon/Epoxy Nanocomposites during Dynamic Compression Test

Previous research has shown that nanocomposites show not only enhancements in mechanical properties (stiffness, fracture toughness) but also possess remarkable energy absorption characteristics. However, the potential of carbon nanotubes (CNTs) as nanofiller in reinforced epoxy composites like glass fiber-reinforced polymers (GFRP) or carbon fiber-reinforced polymers (CFRP) under dynamic testing is still underdeveloped. The goal of this study is to investigate the effect of integrating nanofillers such as CNTs into the epoxy matrix of carbon fiber reinforced polymer composites (CFRP) on their dynamic energy absorption potential under impact. An out-of-plane compressive test at high strain rates was performed using a Split Hopkinson Pressure Bar (SHPB), and the results were analyzed to study the effect of changing the concentration of CNTs on the energy absorption properties of the nanocomposites. A strong correlation between strain rates and CNT mass fractions was found out, showing that an increase in percentage of CNTs could enhance the dynamic properties and energy absorption capabilities of fiber-reinforced composites.

Thermal Conductivity and Sound Absorption Properties of Carbon Nanotube / Foam Aluminum Composites

This article uses powder metallurgy technology to prepare foamed aluminum and carbon nanotubes (CNTs) / foamed aluminum composites. The laser thermal diffusion analyzer, thermal analyzer, and transfer function sound absorption coefficient test system were used to study the thermal conductivity and sound absorption properties of aluminum foam and its composites, respectively. The results show that the thermal conductivity of aluminum foam with 79% porosity is only 5W · m−1·K−1, which is much smaller than the thermal conductivity of aluminum. So it can be used as an ideal thermal insulation material; The thermal conductivity of carbon nanotubes (CNTs) / foamed aluminum-based composites increases first and then decreases with the increase in the mass fraction of CNTs. As the test temperature increases, the thermal conductivity of the material gradually increases. When the mass fraction of CNTs is 0.75%, the thermal conductivity of foamed aluminum-based composites reaches the maximum. As the test frequency increases, the sound absorption performance of foamed aluminum first increases, then decreases, and then gradually increases, reaching a maximum value around 1000 Hz. The sound absorption performance of CNTs / foam aluminum matrix composites decreases at lower test frequencies as the mass fraction of CNTs increases. At higher frequencies, as the mass fraction of CNTs increases, the sound absorption coefficient of foamed aluminum decreases first and then increases.