Addition Of Carbon Nanotubes Research Articles

Structure and electrochemical properties of CNT-supported Li-Ti-O anode material for Li-ion battery

We investigated the structural and electrochemical properties of Li-Ti-O (LTO) and carbon nanotube (CNT)-added LTO for anode material in secondary Li-ion batteries using various techniques. The study focused on elucidating the effects of the microstructural evolution in LTO and the CNT addition on battery functionality. For all the tested compositions of LTO ([Li]/[Ti] = 0.9, 1.0 and 1.22), the system is fully oxidized to comprise a mixed-phase having Li4+2δTi5O12+δ (δ’s are approximately 0.14, 0.25, and 0.65, respectively) and Li2TiO3 structures. The results of the half-cell tests show a decrease in charge/discharge capacity with increasing [Li]/[Ti] ratio, and the detailed structural and chemical analyses unequivocally reveal that the such degradation in the electrochemical property originates mainly from the increase of Li content (δ). Meanwhile, after adding CNT, the Li capacity becomes greatly increased while the LTO composition and the redox kinetics do not change significantly. The origin of the improved specific capacity is associated with the formation of micron-sized structures at the surface of the LTO particles. Thereby we demonstrate that surface engineering via the CNT addition is a promising way to improve the performance of the LTO-based anode material.

Fast Self-Assembly of Photonic Crystal Hydrogel for Wearable Strain and Temperature Sensor.

Structural colors from photonic crystals (PCs) have attracted emerging attention in the research area of wearable sensors. Conventional self-assembly of PC takes days to weeks. Here, a fast self-assembly method of PC with horizontal precipitation of silica nanoparticles (NPs) in a polydimethylsiloxane fence, which can be completed within 1-4 h depending on the fence parameters, is introduced. The resultant PC exhibits tunable structural colors in the entire visible spectrum. With infiltration of composite hydrogels containing acrylic acid, acrylamide, chitosan, and carbon nanotubes (CNTs) into the gaps of NPs to form an inverse opal PC, a structural color hydrogel that can quickly respond to different stimuli, including strain and temperature, is obtained. Moreover, with the addition of CNTs, the composite PC hydrogel can also output an electronic signal together with optical color changes. Based on these extraordinary responsive behaviors, the PC hydrogel sensor for quantitative feedback to external stimuli of stretching, bending, pressing, and thermal stimuli, with brilliant color change and electronic signal outputs simultaneously, is demonstrated. This fast-assembled PC hydrogel with excellent responsive properties has great potential for applications in wearable devices, mechanical sensors, temperature sensors, and colorimetric displays.

Experimental investigation of buckling behavior of E-glass/epoxy laminated composite materials with multi-walled carbon nanotube under uniaxial compression load

This study experimentally investigated the effects of nanoparticle reinforcement on the buckling behavior of composite materials. Different sizes of carboxylic acid functionalized multi-walled carbon nanotubes were used as nanoparticles. E-glass fiber-reinforced composite materials with polymer matrix in the [0°/90°/0°/90°]s cross-ply array with and without carbon nanotube reinforcement were produced by hand lay-up and vacuum bagging. Three types of carbon nanotubes in different sizes and proportions of 0.1%, 0.2%, 0.3%, 0.4%, and 0.5% by weight were added to the epoxy resin. For the buckling test, the samples with two clamped and two free sides were attached to the universal testing machine to apply a uniaxial compressive load. As a result of the experiments, it was found that the addition of carbon nanotube in certain proportions increases the critical buckling load of composite materials. The highest increase in the critical buckling load (26.10% increase) was achieved with a carbon nanotube reinforcement of 0.2% by weight, having an outer diameter of 10–20 nm, internal diameter of 5–10 nm, and length of 0.5–2 mm. As the carbon nanotube sizes added to the epoxy resin decreased, the buckling strength increased.

Preparation of TiO2-CNT-Ag Ternary Composite Film with Enhanced Photocatalytic Activity via Plasma-Enhanced Chemical Vapor Deposition

In this study, a TiO2-CNT-Ag ternary composite film was successfully synthesized using the plasma-enhanced chemical vapor deposition method by simultaneously feeding a carbon nanotube (CNT)/Ag suspension and titanium tetraisopropoxide gas. The prepared TiO2-CNT-Ag film was characterized by scanning electron microscopy, transmission electron microscopy, energy-dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, X-ray diffraction, and ultraviolet-visible spectroscopy. Moreover, the Ag/Ti ratio of the film was confirmed using an inductivity-coupled plasma optical emission spectrometer. The performance of the TiO2-composite film for the degradation of rhodamine 6G under simulated solar light irradiation was evaluated. The rate constant of the prepared TiO2-CNT-Ag for rhodamine 6G degradation was approximately 1.8 times greater than that of prepared TiO2. This result indicates that the addition of CNT and Ag significantly improved the photocatalytic activity of the prepared films.

The Effect of Agglomeration on the Electrical and Mechanical Properties of Polymer Matrix Nanocomposites Reinforced with Carbon Nanotubes.

In this work, we investigated the effect of carbon nanotubes addition and agglomeration formation on the mechanical and electrical properties of CNT–polymer-based nanocomposites. Six specimens with carbon nanotubes (CNTs) fractions of 0%, 0.5%, 1%, 2%, 4% and 5% were manufactured and characterized by dynamic mechanical analysis (DMA) and four-probe method. The stress–strain curves and electrical conductivity properties were obtained. Scanning electron microscopy (SEM) was used to characterize both agglomeration and porosity formation. By employing micromechanics, through representative volume element (RVE), finite element analysis (FEA) and resistor network model (RNM), the Young’s modulus and electrical conductivity values were calculated. The samples’ elastic moduli showed an increment, reaching the maximum value at a CNTs fraction of 2%, thereafter an adverse effect was caused in the high CNT percentage samples. The final electrical conductivity seemed greatly altered with the addition of CNTs, reaching the percolation threshold at 2%. The unavoidable formation of CNT agglomerates appeared to influence the final physical properties. The CNT agglomerates adversely affect the mechanical performance of high-CNT-percentage samples. Conversely, an exponential increment in the electrical conductivity was presented as the agglomerates formed networks allowing the transport of electrons through the tunnelling effect. These phenomena were experimentally and numerically confirmed, showing a good correlation.

Influence of carbon black and carbon nanotube on mechanical and piezoelectric properties of γ–C2S–PZT composite

This paper investigated the influence of carbon black (CB) and carbon nanotube (CNT), used at 0–1%, by volume, on mechanical performance and piezoelectricity of 0–3 γ–C2S–based piezoelectric composite. The γ–C2S–based piezoelectric composite was prepared through carbonation of the proportioned mixture. Parameters d33, g33, and εr were characterized with the CB and CNT additions. The influence of PZT size and volume on these parameters were also studied. Tested results showed that a greater PZT average size and volume significantly improved the d33, g33, and εr values of γ–C2S–based piezoelectric composite given the increased contact among PZT particles. The use of 1.0% CB can lead to 50% and 265% enhancements in d33 and εr, respectively. Such improvements in d33 and εr values were 50% and 190%, respectively, with the addition of 0.3% CNT. This is attributed to the enhanced conductivity of γ–C2S–based piezoelectric composite, which can promote the poling of PZT particles. Moreover, the compressive strength of γ–C2S–based piezoelectric composite were improved by 12 and 3 MPa with the use of CB and CNT, respectively. In addition, the γ–C2S–based piezoelectric composite had 2–6 folds greater d33 and εr values given the similar CB and CNT contents relative to those of cementitious piezoelectric composite. Therefore, the use of CB and CNT can advance the development of γ–C2S–based piezoelectric composite with enhanced mechanical performance and piezoelectricity.

Effects of multi walled carbon nanotubes and multilayer graphene on the damping and quasi-static compressive mechanical properties of novel EP/ZA22 composites

In order to develop novel high damping materials with excellent compressive mechanical properties and energy absorption capacity to meet the needs of buffering and vibration reduction in various fields, epoxy resin (EP) filled foam Zn-22Al (ZA22) composites were fabricated for the first time. EP can significantly improve the damping and compressive mechanical properties of the ZA22 foam due to the superposition of multiple damping sources and the support of EP to pores, respectively. However, the filling of EP will lead to brittleness in the compression process of the composites. It is found that the addition of multi walled carbon nanotubes (MWCNTs) or multilayer graphene (MLG) to EP can efficiently improve the toughness of the composites because of the increased energy consumption in the fracture process of EP, and the damping can also be further improved due to the increased interface density and the amount of polymer chains involved in friction.

Understanding the influencing mechanism of CNTs on the microstructure and mechanical properties of semi-solid stir casting Al-Cu-Mg alloys

In this study, carbon nanotube (CNT) reinforced Al-Cu-Mg composites were fabricated by combining high-energy ball milling (HEBM) with semi-solid stirring casting technology (SSC). The effect of CNTs on the microstructural evolution and performance enhancement of hot extruded CNT/Al-Cu-Mg composites was investigated. SEM and XRD revealed that the addition of CNTs significantly refined the α-Al phase and suppressed its preferential growth in the (111) orientation. The microstructure of the hot-extruded composites was a heterostructure consisting of CNTs-rich fine-grained regions (1–5 μm) and CNTs-poor coarse-grained regions (7–20 μm). Additionally, CNTs were mainly distributed at the α-Al grain boundaries. Specifically, the higher the CNTs content, the higher the recrystallization degree of the composites. The tensile strength and yield strength increased from 319 MPa and 261 MPa to 523 MPa and 476 MPa, respectively, with CNT contents ranging from 0 to 1.5 wt.% owing to dislocation strengthening, grain refinement strengthening, load transfer strengthening, and second phase strengthening induced by CNTs.

Cooling rate effects on luminescence and structure properties of the 5CB liquid crystal, doped by different nanoparticle dispersions

The effect of the 5CB liquid crystal cooling rate on its luminescence spectra at the low temperature (T = 4.2 K) has been found and studied for two types of nanocomposites: 5CB liquid crystal, doped by carbon nanotubes (NT) or so-called hybrid nanoparticles (NT + OMMT). Hybrid nanoparticles were prepared from organomodified layered montmorillonite minerals (OMMT) with the addition of carbon nanotubes. Experiments have been carried out at two cooling rates, 2 and 10 K/min. Structure of the luminescence spectral bands is associated with 5CB crystallization peculiarities and formation of its glass-like state under different cooling regimes of the isotropic phase. The reasons for the short-wavelength shifts of the luminescence peaks for the 5CB–(NT + OMMT) sample compared to the 5CB–NT one are discussed.

Effects of introducing CNTs and GPLs on mechanical, modal, thermal, and water uptake properties of twill basalt fiber-reinforced epoxy matrix composites

The current study investigates the effect of the addition of multiwall carbon nanotubes (CNTs) and graphene platelets (GPLs) on the mechanical, dynamic, viscoelastic, and water uptake properties of basalt fiber-reinforced epoxy (BFE) composites. The results show that the addition of nanoparticles in small concentrations improves the mechanical properties including the modulus of elasticity, tensile strength, flexural modulus, strength, and interlaminar shear strength of BFEs. Moreover, the filling of nanofillers in small concentrations increases the natural frequency and decreases the damping factor. Based on the viscoelastic test results, the addition of CNTs and GPLs in small concentrations improves the viscoelastic properties such as the storage modulus, loss modulus, damping ratio, thermal stability, and thermal conductivity. The filling of CNTs in small concentrations increases the hydrophilic nature. The addition of GPL nanoparticles affects the BFE water uptake characteristics similar to the addition of CNTs. It is worth mentioning that the addition of such nanoparticles in higher concentrations affects the mechanical, modal, and viscoelastic properties of the composites unfavorably.

CNT-Type Dependent Cellular Adhesion on 3D-Printed Nanocomposite for Tissue Engineering.

At present, one of the main limitations of three-dimensional (3D) bioprinting in tissue engineering stems from a scarcity of biomaterials tailored for specific applications. Widely used hydrogels offer an optimal printability and a suitable environment for cell growth; however, they lack the mechanical strength required for non-soft tissues, for example, cartilage, tendons, and meniscus. This work investigated the physicochemical, mechanical, and biological characteristics of a 3D-printed polycaprolactone (PCL) reinforced with multiwalled carbon nanotubes (MWCNT) and “bamboo-like” carbon nanotubes (BCNT) with the following w/w % concentrations: 0.005%, 0.01%, 0.02%, and 0.2%. The materials were analyzed with subsequent techniques: Scanning electron microscopy, nanoindentation, parallel plate rheometry, and differential scanning calorimetry. Biological evaluations were performed with normal human articular chondrocytes by confocal microscopy and proliferation assay. The study revealed that the carbon nanotubes (CNT) addition improved the rheological properties of the material by increasing the setting temperature. Moderate enhancement was observed in terms of mechanical properties. The most significant difference was noted in cell adhesion and proliferation. Pure PCL did not facilitate cell growth and mainly apoptotic cells were observed on its surface. The addition of 0.01% MWCNT resulted in enhanced adhesion and proliferation; however, the morphology of the cells remained spherical, signifying a suboptimal surface for proliferation. Interestingly, PCL reinforced with 0.02% BCNT displayed excellent facilitation of cellular adhesion and proliferation, which is uncharacteristic of pure PCL. In summary, this study investigated the potential of CNT-reinforced PCL for 3D bioprinting and tissue engineering, highlighting key physicochemical, mechanical, and biological aspects of this biomaterial.

Surface Response Analysis for the Optimization of Mechanical and Thermal Properties of Polypropylene Composite Drawn Fibers with Talc and Carbon Nanotubes.

A large portion of the produced Polypropylene (PP) is used in the form of fibers. In this industrially oriented study, the development of composite PP drawn fibers was investigated. Two types of fillers were used (ultra-fine talc and single-wall carbon nanotubes). Optimization of the thermal and mechanical properties of the produced composite drawn fibers was performed, based on the Box-Behnken design of experiments method (surface response analysis). The effect of additives, other than the filler, but typical in industrial applications, such as an antioxidant and a common compatibilizer, was investigated. The drawing ratio, the filler, and the compatibilizer or the antioxidant content were selected as design variables, whereas the tensile strength and the onset decomposition temperature were set as response variables. Fibers with very high tensile strength (up to 806 MPa) were obtained. The results revealed that the maximization of both the tensile strength and the thermal stability was not feasible for composites with talc due to multiple interactions among the used additives (antioxidant, compatibilizer, and filler). Additionally, it was found that the addition of talc in the studied particle size improved the mechanical strength of fibers only if low drawing ratios were used. On the other hand, the optimization targeting maximization of both tensile strength and thermal stability was feasible in the case of SWCNT composite fibers. It was found that the addition of carbon nanotubes improved the tensile strength; however, such improvement was rather small compared with the tremendous increase of tensile strength due to drawing.

Effect of Ni-coated carbon nanotubes addition on the wettability, microhardness, and shear strength of Sn-3.0Ag-0.5Cu/Cu lead-free solder joints

Effect of Ni-coated carbon nanotubes addition on the wettability, microhardness, and shear strength of Sn-3.0Ag-0.5Cu/Cu lead-free solder joints

Mechanical and biological properties of atmospheric plasma-sprayed carbon nanotube-reinforced tantalum pentoxide composite coatings on Ti6Al4V alloy

Ta2O5 coatings containing 0, 3, 5 and 7 vol% multi-walled carbon nanotubes (CNTs) were deposited on Ti6Al4V substrates by atmospheric plasma spraying (APS). The addition of CNTs had no obvious effect on the surface morphology and roughness of the coatings, but increased the coating porosity. The coatings consisted primarily of β-Ta2O5 phase, a small amount of α-Ta2O5, and minor C peaks corresponding to the CNTs. As the CNT content increased, the elastic modulus (E) and indentation fracture toughness also increased. However, the higher CNT content increased the coating porosity and reduced the microhardness. Following immersion in simulated body fluid (SBF) for 14 days, the surfaces of all the coatings were completely covered with hemispherical bone-like apatite. Furthermore, after incubation in osteoblast-like osteosarcoma MG-63 cell culture for 7 days, all of the coatings showed excellent cell attachment, growth and spreading. Overall, the present results show that the addition of CNTs to Ta2O5 raw powder improves the indentation fracture toughness of the resulting coatings without degrading their biological properties.

Study on the effect of tailoring the hard copolymer polyurethane on the thermal, mechanical and electrical properties of hard copolymer polyurethane/multi-walled carbon nanotubes nanocomposites

This study focusses on the effect of the addition of multi-walled carbon nanotubes (MWCNTs) on the morphology and thermal, rheological and electrical properties of hard copolymer polyurethane (HCPU) using 1,5 pentane-diols as a chain extender, containing 85% of hard segment blocks. Step-growth polymerisation was used to synthesise a HCPU polymer matrix, followed by melt compounding to prepare the nanocomposites. SEM investigation of the neat HCPU structure and its nanocomposites indicated the uniform dispersion of MWCNTs within the polymer matrix; further TEM morphology investigation showed some agglomeration regions, attributed to the high MWCNT content (2 wt%). An XRD test confirmed a homogeneous distribution of MWCNTs by observing the remaining location of the highest peaks of MWCNTs and amorphous peaks of the HCPU matrix. Analysis of the melt rheology test results showed an improvement in complex viscosity combined with an increase in the G’ and G” of nanocomposites from those of pure HCPU due to the presence of MWCNTs. Finally, electrical conductivity of nanocomposites demonstrated a significant improvement in its value at high loading of MWCNTs from that of pure HCPU matrix.

Enhancing the solar absorption capacity of expanded graphite-paraffin wax composite phase change materials by introducing carbon nanotubes additives

The potential solar thermal utilization of solar energy based on phase change materials (PCMs) is limited by their low thermal conductivity and weak solar absorption capacity. Among various additives used to enhance the thermal conductivity of PCMs, expanded graphite (EG) has been proved to be a low-cost but effective choice. This work aims to further enhance the solar absorption capacity of EG-paraffin wax composite PCMs by adding small amounts of carbon nanotubes (CNTs) as the light absorbent. The prepared composite PCMs with 5 wt.% EG and 2 wt.% CNTs show superior thermal conductivity (2.05 W/m⋅K), high solar absorption capacity (94.2%) while maintaining the high latent heat (159 kJ/kg). Moreover, these superior thermal and optical properties can be maintained after 1000 melting-freezing cycles. Our results provide a high-performance composite PCM that may be used in solar-thermal conversion applications.

Developments and Applications of Carbon Nanotube Reinforced Cement-Based Composites as Functional Building Materials

Carbon nanotube (CNT) is a promising nanomaterial with excellent mechanical, electrical, thermal, and chemical stability. It has received extensive attention due to its unique multifunctional properties in engineering materials. Researchers have explored the preparation and characterization of CNT reinforced cement-based materials. Studies have shown that adding CNT will significantly improve the performance of cement-based materials. This article introduces the techniques for the dispersion characterization of CNT and summarizes the advantages and disadvantages of these techniques. The functionalized applications of CNT in cement-based materials are reviewed, including sensing performance, structural health monitoring of concrete, electromagnetic shielding, and other applications. In addition, the application and development prospects of CNT in 3D printing concrete have been prospected. Finally, we discussed the existing problems and challenges in developing and applying CNT in cement-based materials and suggested future research.

Mechanical and wear properties of SiCp/CNT/Al6061 hybrid metal matrix composites

6061 aluminum (Al6061) alloy matrix composites with hybrid reinforcements composed of both carbon nanotubes (CNTs) and silicon carbide particles (SiCp) were prepared by spark plasma sintering technique. SiCp, CNTs and Al6061 powder were firstly mixed by a tip-sonication mixing, then frozen the suspension in liquid N2, and finally freeze-dried in a vacuum to obtain the uniform dispersion of SiCp and CNTs. The SiCp/CNT/Al6061 hybrid composites containing homogenously dispersed SiCp and CNTs exhibited significantly improvements in hardness, tensile strength and yield strength values of 37%, 38%, and 49%, respectively, compared with those of SiCp/Al6061 composites without CNTs. The improvements in the mechanical properties were attributed to the synergistic strengthening effects of the CNTs and SiC particulates. The coefficient of friction and specific wear rates of the hybrid composites were decreased by the addition of low-friction CNTs due to the self-lubrication effect. The CNTs did not reduce the friction coefficient and specific wear rate of the specimens as significantly with the increase of the applied load. This could be resulted from the transformation of carbonaceous structures of CNTs during the tribological testing process.

ZnO-MWCNT @ Fe3O4 as a novel catalyst for methanol and ethanol oxidation

Zinc oxide is considered a practical substance in various fields of science, but the low electrical conductivity of zinc oxide seems to be one of the main reasons for its limited use in alcohol oxidation for application in fuel cells. In this study, the ZnO, ZnO-MWCNT, and ZnO-MWCNT@Fe3O4 catalysts were synthesized by hydrothermal method, and their structures and morphologies were characterized by XRD, SEM, EDX, TEM, and BET. To evaluate the electrochemical performance of catalysts, their electro-catalytic ability was investigated in methanol and ethanol oxidation processes. The results showed that the addition of Fe3O4-decorated multi-wall carbon nanotubes to the structure of zinc oxide created the active oxidation sites and increased the conductivity and specific area in the catalyst. The synergistic effects of placement of the catalyst components to each other increased the methanol and ethanol oxidation ability of ZnO-MWCNT@Fe3O4, and the excellent stability of 91% was obtained during 500 cycles in the MOR process. The proposed catalyst introduces ZnO-based materials as a catalyst that has promising potential applications in alcohol oxidation.

Insight into dynamic compressive response of carbon nanotube/carbon fiber-reinforced concrete

The dynamic compressive properties of concrete reinforced with the carbon nanotubes (CNTs) and carbon fibers (CFs) were investigated in this paper. For both single and hybrid addition, the CNTs and CFs enhanced the dynamic compressive strength of the concrete, but the hybrid addition showed a higher enhancement effect. Hybrid CNTs and CFs were more conducive to improve the strain-rate effect of the dynamic compressive strength, and when the content of hybrid CNTs and CFs was constant, a higher proportion of CNTs led to a more significant improvement. However, the addition of CNTs alone reduced the strain-rate effect. The addition of CNTs increased the content of hexagonal prismatic Ca(OH)2, the proportions of gel pores and harmless capillaries, and decreased the porosity of the concrete, thus enhancing the dynamic compressive strength of the concrete. The addition of CFs increased the porosity of the concrete and the probability of large pores. But the crack-inhibition action of the CFs still led to the increase of the dynamic compressive strength. The hybrid synergistic effect of CNTs and CFs was more conducive to enhance the dynamic compressive strength and its strain-rate effect, and also to enhance the impact resistance of the concrete.