CNT Nanocomposites Research Articles

Nickel sulfide anchored carbon nanotubes for all-solid-state lithium batteries with enhanced rate capability and cycling stability

All-solid-state lithium batteries employing NiS–CNT nanocomposites as cathodes exhibit superior rate capability and cycling performances owing to their excellent ionic/electronic conduction and structural stability.

3D Porous Mixed‐Valent Manganese Oxide Nanosheets Electrodeposited onto Flexible Ag‐CNT Textiles for Highly Improved Capacitive Performances

AbstractA simple yet efficient one‐pot ultrasonication process for the green preparation of a silver–carbon nanotube (Ag‐CNT) ink, which was then used to fabricate conductive flexible thin films by a simple immersion process, is reported. A novel three‐dimensional (3D) porous, hierarchical Ag–MnOx–CNT nanocomposite was synthesized by electrodeposition of manganese oxide (MnOx) nanosheets composed of MnO2 and Mn3O4 onto the Ag–CNT films. The unique Ag–MnOx–CNT electrode showed a specific capacitance of 842 F/g at 1 A/g and excellent charge–discharge cycling stability, with a capacitance retention of 148% at 10 A/g and a Coulombic efficiency of ∼90% after 5000 cycles. The greatly enhanced capacitive performance is ascribed to the facile redox reactions, 3D porous framework, and use of Ag NPs. These impressive results suggest that this nanocomposite is a promising candidate for use in high‐performance flexible energy storage applications.

Roles of filler dimensions, interphase thickness, waviness, network fraction, and tunneling distance in tunneling conductivity of polymer CNT nanocomposites

We present a simple model to express the tunneling conductivity of polymer CNT nanocomposites as a function of the filler dimensions, filler conductivity, interphase thickness, waviness, fraction of networked CNTs, and tunneling distance. This model expresses the percolation threshold and the fraction of networked CNTs in terms of filler dimensions, waviness, and interphase thickness. The model was tested using experimental results from the literature. The predictions show good agreement with the experimental results in all samples, demonstrating the model's robustness for estimating tunneling conductivity. Moreover, the tunneling distance decreases as the filler concentration increases in all samples. The model parameters have a reasonable effect on the tunneling conductivity. The waviness and tunneling distance inversely affect the tunneling conductivity. Further, the waviness weakens the effective length of the nanotubes, and large tunneling distances cannot effectively transfer electrons between two adjacent nanotubes. The interphase thickness directly controls the tunneling conductivity, because a thick interphase reduces the percolation threshold. Poor percolation also creates large and dense conductive networks in nanocomposites, which is desirable for conductivity.

PPy/TiO2(np)/CNT polymer nanocomposite material for microwave absorption

PPy/TiO2(np)/CNT nanocomposites are synthesized by ‘chemical oxidative polymerization’ of pyrrole. It is observed that polypyrrole along with TiO2(np) form core shell structure. The microwave measurements such as permittivity, permeability and reflection losses (metal back) are studied at X-band. Minimum reflection loss of microwave is due to dielectric loss in the nanocomposite and is − 51.11 dB (99.99%) at 8.64 GHz for sample (PPy/TiO2(np)/CNT) of thickness 3 mm. The nanocomposite is characterized by FESEM and XRD. The particle size of the TiO2(np) is found to be ranging from 60 to 150 nm. The average crystallite size is determined by Scherrer formula and is found to be 26 nm. We have observed negative value of µ″ (complex part of permeability) for the entire frequency range (8–12 GHz). In our study we also observed the resonance–antiresonance phenomenon in all the samples. We have also seen maximum attenuation of microwave for PPy/TiO2(np)/CNT polymer nanocomposite. The synthesized nanocomposites can be used for metamaterial applications.

Tribological and Mechanical Properties of Al(Cu)/MWCNT Nanocomposite Prepared by Mechanical Alloying and Hot Extrusion

The bulk Al–Cu-multiwall carbon nanotube (MWCNT) nanocomposite was prepared using mechanical alloying (MA) and hot extrusion processes. Al–4 wt % Cu powder mixture was first milled for 20 h to form the nanostructured Al(Cu) solid solution. The MWCNT was then added to the Al(Cu) powder mixture and further milled for 5 h. X-Ray Diffraction (XRD) and Differential Thermal Analysis (DTA) were performed to study the phase transformations during mechanical alloying and hot extrusion. Scanning Electron Microscope (SEM) and Transmission Electron Microscope (TEM) were also employed to study the samples microstructure. Mechanical properties of the bulk Al(Cu)/CNT nanocomposite were also studied using room and high temperature compression and wear tests. The results showed that after 20 h of mechanical alloying, a supersaturated Al(Cu) solid solution with the average grain size of 25 nm was achieved. Homogenous distribution of CNTs in the Al(Cu) supersaturated matrix was obtained. CNTs retained their tubular structure after 5 h milling time. Hot extrusion process at 550°C also led to the formation of bulk samples with nearly full density. The average yield and compressive strength of the Al(Cu)/CNT nanocomposite were found to be around 450 and 590 MPa at room temperature. The bulk nanocomposite showed suitable thermal stability by keeping its strength up to 300°C.

Synthesis and Characterization of TiO<sub>2</sub>/CNT Nanocomposites for Azo Dye Degradation

Pure TiO2 nanoparticles, TiO2/9 wt %CNT and TiO2/18 wt %CNT nanocomposites were fabricated by sol-gel method and the CNTs in TiO2/CNT nanocomposite were grown under the catalysis of Ni film in thermally chemical deposition process. The TiO2/CNT was characterized and analyzed by field-emission scanning electron microscope, transmission electron microscope, and x-ray diffractometer. The results showed that the pure TiO2 nanoparticles have anatase form when calcination temperature T ≦ 500 °C, and partly become rutile form when T ≧ 550 °C. The CNTs embedded in TiO2 could retard the phase transformation of TiO2 from anatase into rutile. The grain sizes of anatase and rutile phases ranged from 10.1 to 27.7 nm and essentially increase with increase in calcinations temperature. The CNTs in composite could reduce the adsorption and the photocatalytic degradation of azo dye (AO7).

Microstructure and mechanical properties of consolidated Cu-Cr-CNT nanocomposite prepared via powder metallurgy

In this paper, Cu-1wt.%Cr and Cu-1wt.%Cr/5wt.%CNT nanocomposite powders were produced by mechanical alloying method. Then, nanocomposite samples were consolidated by hot pressing at different temperatures of 25, 300 and 500 °C, times of 30, 60, 90 and 120 s and pressures of 40, 80 and 120 MPa. The consolidated nanocomposite samples were characterized by X-ray diffraction, scanning electron microscopy, shear punch test, wear test and measurements of density, microhardness and thermal stability. It was found that pressing temperature has a significant effect on improvement of hardness by about 65%. A quantitative relationship between relative density and pressing pressure was proposed. The effects of CNTs addition on the consolidation behavior and characteristics of the consolidated samples were also investigated. The results showed that the addition of CNTs makes the relative density, hardness, shear strength and elongation to failure decrease. However, in the presence of CNTs, the friction coefficient decreased by 82%; therefore, the wear resistance of the Cu-1wt.%Cr/5wt.%CNT nanocomposite was 72% higher than that of the Cu-1wt.%Cr. Additionally, presence of 5wt.% CNTs led to a four times greater thermal stability.

Role of the particle size polydispersity in the electrical conductivity of carbon nanotube-epoxy composites

Carbon nanotubes (CTNs) with large aspect-ratios are extensively used to establish electrical connectedness in polymer melts at very low CNT loadings. However, the CNT size polydispersity and the quality of the dispersion are still not fully understood factors that can substantially alter the desired characteristics of CNT nanocomposites. Here we demonstrate that the electrical conductivity of polydisperse CNT-epoxy composites with purposely-tailored distributions of the nanotube length L is a quasiuniversal function of the first moment of L. This finding challenges the current understanding that the conductivity depends upon higher moments of the CNT length. We explain the observed quasiuniversality by a combined effect between the particle size polydispersity and clustering. This mechanism can be exploited to achieve controlled tuning of the electrical transport in general CNT nanocomposites.

Synthesis of Hedgehoglike F-TiO2(B)/CNT Nanocomposites for Sonophotocatalytic and Photocatalytic Degradation of Malachite Green (MG) under Visible Light: Kinetic Study.

The present study describes the preparation of hedgehoglike F-doped titanium dioxide bronze (F-TiO2(B)) and its nanocomposites containing single-walled and multiwalled carbon nanotubes (SWCNTs, MWCNTs) by using combined ball milling-hydrothermal processes. Then, sonophotocatalytic and photocatalytic degradation of malachite green (MG) dye from aqueous solution using prepared materials was performed. The results show that F-TiO2(B)/SWCNT displays a good sonophotocatalytic and photocatalytic performance among other products under visible light. In addition, they indicated that the efficiency of malachite green degradation is more than 95% and 91% for sonophotocatalytic and photocatalytic methods, respectively. Also, they demonstrate that the photocatalytic efficiency of catalysts increases in the presence of ultrasound and the sonophotocatalysis process followed a second-order kinetics. The catalysts have been characterized by transmission electron microscopy (TEM), field emission scanning electron microscopy (FESEM), X-ray diffraction analysis (XRD), Fourier transform infrared spectroscopy (FTIR), UV-vis diffuse reflectance spectroscopy, and energy-dispersive X-ray spectroscopy (EDX). The analyzed data confirmed the presence of CNTs and fluorine (F) as dopant in all nanocomposites. The presented hybrid method reduced the band gap from 3.02 eV for F-TiO2(B) to 2.7 eV for F-TiO2(B)/SWCNT nanocomposite.

Microstructural evaluation and mechanical properties of Al-CNT nanocomposites produced by different processing methods

In this research, the semi-wet (SW) and slurry based (SB) methods were applied to synthesize Al-1.5 wt.%CNT nanocomposites powder. The initial 30 mm diameter compacted billets were produced through cold pressing and pressure-less sintering at 550 °C for 2 h for both types of nanocomposites. The billets were hot extruded at 400 °C to produce 10 mm diameter rods. The synthesis parameters of composites were investigated through experiments of tension, compression, FTIR, XRD, STA and Raman. The dispersion of CNTs within Al powder and fracture surface analysis was studied through FE-SEM.The yield and tensile strength of pure Al sample were measured as 90 and 136 MPa, respectively. These values were increased to 110 and 170 MPa for SW sample and improved to 152 and 203 MPa for SB product, by adding 1.5 wt.% CNT to pure Al. The strengthening effect of fibers was investigated using load transfer mechanism with fiber length less than critical value (l < lc) for SW and long fiber issue (l > lc) for SB samples. According to the fracture surface analysis, the bridging and CNTs fracture phenomena were observed in SB specimen and CNTs pull out was detected for SW sample. These results showed good agreement with strengthening efficiency of fibers (R) versus shear stress diagram including R = 25.6 in CNTs fracture and R = 13 in pull out regions. The Al4C3 interphase formation was characterized by XRD and Raman spectroscopies whereas end-contact and side-contact of carbides around CNTs were suggested as preferred sites for SB and SW products, sequentially.

Microstructure and Mechanical Properties of Al-3 Vol% CNT Nanocomposites Processed by High-Pressure Torsion

Abstract Al-3 vol% CNT nanocomposites were processed by high-pressure torsion (HPT) at room temperature under the pressure in the range of 2.5-10 GPa for up to 10 turns. Optical microscopy, scanning electron microscopy, and transmission electron microscopy (TEM) were used to investigate the microstructural evolutions upon HPT. Mechanical properties of the HPT-processed disks were studied using tensile tests and microhardness measurements. The results show gradual evolutions in the density, microstructure, and hardness with increasing the number of turns and applied presure. Nanostructured and elongated Al grains with an average grain thickness of ~40 nm perpendicular to the compression axis of HPT and an aspect ratio of ~3 are formed after 10 turns under 6 GPa. Evaluating the mechanical properties of the 10-turn processed Al/CNT nanocomposites indicates a tensile strength of 321 MPa and a hardness of 122 Hv. The tensile fracture surface of the Al/CNT nanocomposite mostly demonstrates a smooth fracture manner with fine dimples resulting in a low tensile ductility of ~1.5%.

Hierarchically porous-structured ZnxCo1−xS@C–CNT nanocomposites with high-rate cycling performance for lithium-ion batteries

Hybrid nanocomposites constructed from starfish-like ZnxCo1−xS rooted in porous carbon and strongly coupled carbon nanotubes have been rationally designed and they exhibit excellent lithium-storage performance.

A glassy carbon electrode modified with γ-Ce2S3-decorated CNT nanocomposites for uric acid sensor development: a real sample analysis

γ-Ce2S3-decorated multi-walled carbon nanotube nanocomposite (Ce2S3-CNT NC) was synthesized by a wet chemical method in basic media.

Fabrication of anl-glutathione sensor based on PEG-conjugated functionalized CNT nanocomposites: a real sample analysis

Three series of polyethylene glycol–carbon nanotube nanocomposites in the form of PEG/CNTa–e, PEG/f-CNT.Oxia–e, and PEG/CNT.C18a–ehave been fabricated using a dissolution stirring ultra-sonication method.

Electrochemical nanostructure platform for the analysis of glutathione in the presence of uric acid and tryptophan

In this work, a NiO–CNT nanocomposite and 2-(3,4-dihydroxyphenethyl)isoindoline-1,3-dione (DPID) were used as modifiers for the modification of a carbon paste electrode (DPID/NiO–CNT/CPE) for the electro-catalytic analysis of glutathione (GSH).

Efficient 2-Nitrophenol Chemical Sensor Development Based on Ce2O3 Nanoparticles Decorated CNT Nanocomposites for Environmental Safety.

Ce2O3 nanoparticle decorated CNT nanocomposites (Ce2O3.CNT NCs) were prepared by a wet-chemical method in basic medium. The Ce2O3.CNT NCs were examined using FTIR, UV/Vis, Field-Emission Scanning Electron Microscopy (FESEM), X-ray electron dispersive spectroscopy (XEDS), X-ray photoelectron spectroscopy (XPS), and powder X-ray diffraction (XRD). A selective 2-nitrophenol (2-NP) sensor was developed by fabricating a thin-layer of NCs onto a flat glassy carbon electrode (GCE, surface area = 0.0316 cm2). Higher sensitivity including linear dynamic range (LDR), long-term stability, and enhanced electrochemical performances towards 2-NP were achieved by a reliable current-voltage (I-V) method. The calibration curve was found linear (R2 = 0.9030) over a wide range of 2-NP concentration (100 pM ~ 100.0 mM). Limit of detection (LOD) and sensor sensitivity were calculated based on noise to signal ratio (~3N/S) as 60 ± 0.02 pM and 1.6×10−3 μAμM-1cm-2 respectively. The Ce2O3.CNT NCs synthesized by a wet-chemical process is an excellent way of establishing nanomaterial decorated carbon materials for chemical sensor development in favor of detecting hazardous compounds in health-care and environmental fields at broad-scales. Finally, the efficiency of the proposed chemical sensors can be applied and utilized in effectively for the selective detection of toxic 2-NP component in environmental real samples with acceptable and reasonable results.

Synthesis of star-like MnO2-CeO2/CNT composite as an efficient cathode catalyst applied in lithium-oxygen batteries

A MnO2-CeO2/CNT nanostructure is synthesized using hydrothermal method for which the amounts of CNT, CeO2 and MnO2 are determined using TGA and ICP-OES analysis equal to 55%, 25% and 20%, respectively. The MnO2-CeO2/CNT nanocomposite is characterized using SEM, EDS-SEM, XRD, BET, TGA and ICP techniques and used as an efficient cathodic electrocatalyst in the lithium-oxygen battery. The energy storage capacity of the lithium-oxygen battery fabricated using pristine CNT is about 4100mA.h/gelectrode at 100mA/gelectrode current density but that of MnO2-CeO2/CNT nanocatalyst is 7980mA.h/gelectrode at the 50mA/gelectrode current density and 6860mA.h/gelectrode at the 100mA/gelectrode current density showing a 68% improvement in the battery performance. The charge and discharge over-voltages are 0.68 and 0.20V, respectively, for MnO2-CeO2/CNT while they are 1.44 and 0.32V for CNT, respectively, at the 100mA/gelectrode current density exhibiting 52% and 37.5% decrease in charge and discharge over-voltages. The cyclic performance of the MnO2-CeO2/CNT nanostructure cathode is considered at 70 cycles reflecting its appropriate performance. The electrochemical impedance spectroscopy (EIS) illustrates a suitable reversibility for the synthesized cathode in such a way that the resistance created at discharge is diminished at the charging process.

Elastic properties of CNT- and graphene-reinforced nanocomposites using RVE

The present paper is aimed to evaluate and compare the effective elastic properties of CNT- and graphene-based nanocomposites using 3-D nanoscale representative volume element (RVE) based on continuum mechanics using finite element method (FEM). Different periodic displacement boundary conditions are applied to the FEM model of the RVE to evaluate various elastic constants. The effects of the matrix material, the volume fraction and the length of reinforcements on the elastic properties are also studied. Results predicted are validated with the analytical and/or semiempirical results and the available results in the literature. Although all elastic stiffness properties of CNT- and graphene-based nanocomposites are found to be improved compared to the matrix material, but out-of-plane and in-plane stiffness properties are better improved in CNT- and graphene-based nanocomposites, respectively. It is also concluded that long nanofillers (graphene as well as CNT) are more effective in increasing the normal elastic moduli of the resulting nanocomposites as compared to the short length, but the values of shear moduli, except G23 of CNT nanocomposite, of nanocomposites are slightly improved in the case of short length nanofillers (i.e., CNT and graphene).

압출성형기를 이용한 나노복합재 필름의 특성 분석

Polypropylene(PP)/multiwalled carbon nanotubes(MWCNT) nanocomposites films and PP/poly(vinyl alcohol)/CNT nanocomposites films were prepared through melt mixing method by the extruder. The PP/CNT nanocomposites films, which contain CNT of a variable content, were prepared for the first time and research on a appropriate content of the CNT on the PP/CNT nanocomposites films was conducted. The effects of take-up speed of the extruder on the mechanical and chemical properties of the PP/CNT and PP/PVA/CNT nanocomposites film were studied. Field emission scanning electron microscope(FE-SEM) was used to examine the surface morphology and the DSC measurement and tensile test were conducted. It was found that the properties decreased when take-up speed was increased.

Enhanced Water Vapor Transmission through Porous Membranes Based on Melt Blending of Polystyrene Sulfonate with Polyethylene Copolymers and Their CNT Nanocomposites.

A novel concept for the use of an immiscible and non-meltable polymer, such as sodium polystyrene sulfonate (PSSNa), in order to prepare polyethylene non-woven breathable membranes is described. Membranes were fabricated by melt compounding of properly functionalized PE (P(E-co-AA)) and PSSNa (P(SSNa-co-GMA)) copolymers in the presence of water soluble polyethylene glycol (PEG). The inability of PSSNa derivatives to be melted was overcome by using PEG, which was easily meltable thus inducing PSSNa processability improvement. PEG was removed after membrane fabrication and therefore also acted as a porogen. Carbon nanotubes, functionalized with PSSNa moieties or alkyl groups, were also incorporated in the membranes with the aim of improving the porous connectivity and increasing the water vapor transmission rate. The morphology of the membranes was investigated through Scanning Electron Microscopy (SEM). Water vapor transmission rate (permeation) (WVTR) measurements for the porous membranes showed increased values in comparison with the neat PE ones. A further increase of WVTR was observed with the addition of CNTs to the polymer membranes.