CNT Composites Research Articles

Flexible thermoelectric cells fabricated by rubbing-in technology with rubber-carbon nanotubes/graphene composites

In this research, CNT and graphene-rubber composites based thermoelectric cells were fabricated by using the rubbing-in technology. However, the comparative analysis of both elastic thermoelectric cells was also carried out. The carbon nanotubes and graphene composites with rubber were used as an active layer of thermoelectric cells. The films were deposited over rubber substrate (length 7 mm and width 5 mm) and pressure of (7–12) g/cm2. The electric dependence of the cells i.e., voltage (open-circuited), current (short-circuited), resistance and Seebeck coefficient with respect to averaged temperature (with gradient = 10 °C) was measured in the temperature interval of 30 °C–55 °C. The CNT/Graphene-rubber composite based active layer properties were investigated and results showed that with an increment in average temperature, there is an increase in current and voltage as well. In case of short circuit current, the increase in CNT-rubber and graphene-rubber composites was 1.82 and 4.5 times while an increase in open circuit voltage was 1.75 and 6.5 times, respectively. It was also found, that the graphene-rubber composites cells had a higher thermoelectric coefficient as compared to CNT-rubber thermoelectric cells. These cells can be potentially utilized as flexible and vibrations free thermoelectric sensors for measurement of the gradient of temperature and elastic thermoelectric modules for low power applications.

Enhanced photocatalytic activity of ternary multilayered Ag/TiO 2 /CNT composites for methylene blue degradation

The TiO 2 modified carbon nanotube composites (TiO 2 /CNT) and Ag deposited ternary multilayered composites (Ag/TiO 2 /CNT) were prepared by chemical deposition and sonochemical reaction, respectively. The composites were characterised by transmission electron microscopy, scanning electron microscopy, X-ray diffraction, Fourier-transform infrared spectroscopy, and ultraviolet-visible (UV-vis). The results showed that anatase TiO 2 layers were wrapped on the surfaces of the CNTs. The face-centred-cubic structure of Ag nanoparticles (NPs) was dispersedly formed on the surfaces of the Ag/TiO 2 /CNT composites. The expected formation and good dispersion of Ag was obtained by high-intensity ultrasound irradiation assistance. All the resulted TiO 2 /CNT and Ag/TiO 2 /CNT composites exhibited a higher photocatalytic performance than that of TiO 2 for the degradation of methylene blue. The novel nanocomposite photocatalysts were developed through structural changes and double effects of carbon materials and noble metals as electron acceptors. Inhibited recombination of electron-hole pairs allows effective electron transfer and active redox reaction on the surfaces of the composites. The novel composite combines the CNTs with excellent electronic nature and nobel metallic NPs with the special semiconductor-metal junction. It can provide new guidance for the application of carbon nanotube-based photocatalytic materials in photocatalysis field from UV-vis spectrum.

High conductive and mechanical robust carbon nanotubes/waterborne polyurethane composite films for efficient electromagnetic interference shielding

Highly conductive multi-walled nanotubes (MWCNT)/waterborne polyurethane (WPU) composites were prepared using facile latex technology without surfactant, in which the solid composites were achieved by filtration process to prevent the re-aggregation of MWCNT during drying process. MWCNT was distributed along the interfaces of polyurethane particles, constructing segregated structure without insulating surfactant. Therefore, high conductivity of 362.6 ± 23.1 S m−1 was obtained at CNT content of 10.6 wt%, resulting in excellent electromagnetic interference (EMI) shielding effectiveness (SE) of 24.7 dB at thin film thickness of 0.4 mm in X-bands. Considering lightweight and thin thickness, outstanding specific shielding effectiveness (SSE) of 537 dB cm2 g−1 was achieved, higher than most values of CNT composites ever reported. Furthermore, the composites exhibited desirable mechanical properties with high elongation at break of 62%, demonstrating promising applications for commercial EMI shielding, especially for flexible and stretchable devices.

Carbon nanotube functionalization as a route to enhancing the electrical and mechanical properties of Cu-CNT composites.

Copper-CNT (carbon nanotube) composite materials are promising alternatives to conventional conductors in applications ranging from interconnects in microelectronics to electrical cabling in aircraft and vehicles. Unfortunately, exploiting the full potential of these composites is difficult due to the poor Cu-CNT electro-mechanical interface. We demonstrate through large-scale ab initio calculations and sonication experiments that this problem can be addressed by CNT surface modification. Our calculations show that covalent functionalization of CNTs below 6.7 at% significantly improves Cu-CNT wetting and the mechanical properties of the composite. Oxidative pre-treatment of CNTs enhances the Young's modulus of the composite by nearly a factor 3 above that of pure Cu, whereas amination slightly improves the electrical current density with respect to the unmodified Cu-CNT system in the high bias regime. However, only nitrogen doping can effectively improve both the mechanical and electrical properties of the composite. As the experiments show, consistent with the calculations, substitutional doping with nitrogen effectively improves adhesion of the CNT to the Cu matrix. We also predict an improvement in the mechanical properties for the composite containing doped double-wall CNTs. Moreover, the calculations indicate that the presence of nitrogen dopants almost doubles locally the transmission through the nanotube and reduces the back scattering in the Cu matrix around the CNT. The computed electrical conductance of N-doped Cu-CNT "carpets" exceeds that of an undoped system by ∼160%.

Li2TiO3/Graphene and Li2TiO3/CNT Composites as Anodes for High Power Li–Ion Batteries

AbstractThree‐dimensional composites Li2TiO3/graphene (LTO/Gr) and Li2TiO3/carbon nanotube (LTO/CNTs) were synthesized by solid‐state reaction for application as anode materials for lithium‐ion batteries. These composites are structurally characterized by X‐ray diffraction, Raman spectroscopy and high‐resolution transmission electron microscopy, while electrochemically tests are performed by cyclic voltammetry and chronopotentiometry. The synergetic effect of graphene and CNTs with LTO facilitate the network conduction leading to faster electron and Li+ ion transfer and improve cycling stability and rate capability of the anode. The LTO/Gr and LTO/CNTs composites exhibited an initial discharge capacity as high as 154 and 149 mAh g−1 at 1C rate, respectively and retained excellent cycling stability of 98% and 96% after 30 charge–discharge cycles.

Facile Synthesis of PVP-MnO2/CNT Composites as ORR Electrocatalyst for an Air-Cathode Microbial Fuel Cell

The cathodic oxygen reduction reaction (ORR) is an influential step in fuel cells for the electrochemical energy conversion. Here we synthesized Polyvinylpyrrolidone incorporated carbon nanotube supported manganese dioxide (PVP-MnO2/CNT) composite and used as ORR electrocatalyst for air-cathode microbial fuel cell (MFC). The physical and electrochemical characterization of PVP-MnO2/CNT were performed by using Field Emission Scanning Electron Microscopy (FESEM), Energy Dispersive X-ray analysis (EDX), X-ray Diffraction analysis (XRD), Cyclic Voltammetry (CV) and Electrochemical Impedance Spectroscopy (EIS). The electrochemical characterization results showed that the PVP-MnO2/CNT possessed the higher ORR catalytic activity with lower charge transfer resistance compared to MnO2 and MnO2/CNT. The performance of the electrocatalysts as cathode was evaluated in air-cathode MFC and it was found that the MFC with MnO2-PVP/CNT electrocatalyst generated a maximum power density of 1365.30 mW/m3, which was higher than that of MFCs with MnO2/CNT catalyst (1083.98 mW/m3), MnO2 (540.91mW/m3) and CNT (438.47 mW/m3). Therefore, the viable synthetic strategy and proposed application of PVP-MnO2/CNT will broaden up the reality of MFC for power generation.

Enhanced Microwave Absorption of CNT Composites Mixing with Fe3O4 and Carbonyl Iron

Enhanced Microwave Absorption of CNT Composites Mixing with Fe3O4 and Carbonyl Iron

Development of sunflower oil‐based nonisocyanate polyurethane/multiwalled carbon nanotube composites with improved physico‐chemical and microwave absorption properties

In this article, we have developed sunflower oil based non‐isocyanate polyurethane (NIPU)/amine functionalized multiwalled carbon nanotube (AF‐CNT) composites. First, carbonated sunflower oil (CSFO) was obtained by solvent‐free mixture reaction of CO2 with epoxidized sunflower oil under the conditions (120°C, 40 bar) for 10 h, and characterized by FTIR, 1H NMR and 13C NMR. Then, NIPUs were synthesized by reacting the CSFO with isophorone diamine (IPDA) and subsequently, the effects of different weight percentages (0–2 wt%) of AF‐CNTs on physico‐chemical properties of the NIPU/AF‐CNT composites were examined. FT‐IR, XRD and SEM analyses confirmed the formation of the polymer nanocomposites. The results of the studies showed that polymer nanocomposites exhibited better performance than that of pristine polymer. In addition to the improvement in physico‐chemical properties, the electromagnetic interference shielding properties of the composites (1.5 wt% AF‐CNTs) were also calculated in the 8.2–12.4 GHz (X‐band) frequency range with different thicknesses. It is seen that the composite (1.5 wt%) with thickness 3 mm shows the highest microwave absorption with −17 dB at 10.86 GHz. POLYM. COMPOS., 40:E1120–E1130, 2019. © 2018 Society of Plastics Engineers

High activity of g-C3N4/multiwall carbon nanotube in catalytic ozonation promotes electro-peroxone process

Three kinds of graphitic carbon nitride materials (bulk, porous and nanosheet g-C3N4) were composited with a multiwall carbon nanotube (MWCNT) by a hydrothermal method, and the obtained b-C3N4/CNT, p-C3N4/CNT and n-C3N4/CNT materials were used in the electrodes for electro-peroxone process. It was found that the n-C3N4/CNT composite exhibited the highest efficiency in oxalate degradation, though it performed the worst in the oxygen-reduction reaction for H2O2 production. The n-C3N4/CNT composite exhibited higher activity than CNT and other composites in catalytic ozonation experiments, due to the higher pyrrolic-N content modified on the CNT surface and higher surface area. It also has higher electron transfer ability, which benefited to the electro-reduction of both O2 and O3. The result confirmed that catalytic ozonation process was an important means to enhance the degradation efficiency in the electro-peroxone process, besides peroxone process and O3-electrolysis.

Hybrid effects in the fracture toughness of polyvinyl butyral-based nanocomposites

Hybrid polyvinyl butyral (PVB) nanocomposite films comprising surface-treated carbon nanotubes (CNT-COOH) and nanoclays (NC) were tested for their “trouser-leg” fracture toughness in comparison to the values of the respective CNT and NC parent composites and to that of the pristine PVB film. Relative to the fracture toughness of the pristine PVB, the parent composites PVB/CNT-COOH-0.2% and PVB/NC-2% and the PVB/CNT-COOH-0.2%/NC-2% hybrid exhibited 105, 118, and 181% improvements, respectively. These were both impressive fracture toughness improvements and a significant hybrid effect – the latter being only slightly lower than the nominal maximum effect of 223% based on the combined improvements of the parent composites. Part of the samples was tested qualitatively by ball impact test of ballistic glass samples with relevant films. Among these samples, the hybrid film presented the best result. A significant linear correlation between fracture surface energy and roughness values was taken to reflect a fracture resistance mechanism of crack front slowdown by its interactions with nanoparticles.

Highly packed graphene–CNT films as electrodes for aqueous supercapacitors with high volumetric performance

Aqueous supercapacitors with high volumetric energy density are prepared using high mass, high density (1.5 g cm−3) electrodes of graphene–CNT composites.

Predicting mechanical properties of polyvinylidene fluoride/carbon nanotube composites by molecular simulation

Pristine polyvinylidene fluoride (PVDF) and its CNT composites (PVDF/CNT) at three CNT weight fractions, 8 wt%, 16 wt% and 24 wt%, were used to investigate the influence of CNT fraction on the mechanical properties of PVDF. Molecular dynamics (MD) simulation was utilized to predict the mechanical properties of PVDF/CNT composites. The tensile stress–strain profiles indicate that the Young’s modulus and tensile strength of pristine PVDF can be significantly improved by the embedded CNTs. However, these CNTs induce stress concentration within the composites, resulting in increased brittleness and a fracture at lower strains. By taking advantage of this molecular simulation procedure, fast comparable predictive properties of PVDF/CNT composites could be performed, with the simulation results providing atomistic-level insights into this new pathway to reduce the cost and research time in related experiments.

Comparison of the effect of carbon, halloysite and titania nanotubes on the mechanical and thermal properties of LDPE based nanocomposite films

Abstract In this study, titania nanotubes (TNTs) were prepared by hydrothermal method with the aim to compare the properties of these one-dimensional tubular nanostructures' reinforced nanocomposites with the carbon and halloysite nanotubes' (CNTs and HNTs, respectively) reinforced nanocomposites. Low density polyethylene (LDPE) was used as the matrix material. The prepared nanocomposites were characterized and compared by means of their morphological, mechanical and thermal properties. SEM results showed enhanced interfacial interaction and better dispersion of TNTs and HNTs into LDPE with the incorporation of a MAPE compatibilizer, however, these interactions seem to be absent between CNTs and LDPE, and the CNTs remained agglomerated. Contact angle measurements revealed that CNT filled nanocomposites are more hydrophilic than HNT composites, and less than TNT composites. CNTs provided better tensile strength and Young's modulus than HNT and TNT nanocomposites, a 42% increase in tensile strength and Young's modulus is achieved compared to LDPE. Tear strength improvement was noticed in the TNT composites with a value of 35.4 N·mm − 1 , compared to CNT composites with a value of 25.5 N·mm − 1 ·s − 1 . All the prepared nanocomposites are more thermally stable than neat LDPE and the best improvement in thermal stability was observed for CNT reinforced nanocomposites. CNTs depicted the best improvement in tensile and thermal properties and the MAPE compatibilizer effectiveness regarding morphological, mechanical and thermal properties was only observed for TNT and HNT systems.

Exposure assessment method for products containing carbon nanotubes inside a test chamber with a Taber abrasion machine

Polymer/carbon nanotube (CNT) composites exhibit distinguished properties, but more quantitative risk assessments on CNTs are necessary as research and development advances. One method to assess the exact risk is to evaluate the characteristics of nanoparticles generated from CNT composites during sanding or Taber abrasion tests. Some researchers have applied loads to CNT composites using Taber machines and analysed the particles using aerosol-measuring instruments and electron microscopes. However, employing aerosol-measuring instruments is challenging due to the small amount of generated particles. Additionally, the presence of abundant background nanoparticles in testing environments creates issues in quantitative measurements. Our research strives to develop an examination method to measure even very small amounts of nanoparticles generated by Taber abrasion. In this study, a Taber abrasion machine is miniaturised so that it fits inside a small chamber. A high-efficiency particulate air filter is attached to the chamber to eliminate background nanoparticles. Then CNT composites are abraded with the miniaturised Taber abrasion machine inside the chamber and the generated particles are analysed.

Experimental study on mechanical properties of PE / CNT composites

High density polyethylene/carbon nanotube composites have been produced for investiga- tions. Four CNT volume fractions and two injection pressures were considered. According to the Taguchi approach, eight experiments were designed. The effect of the carbon nanotubes weight fraction and injection pressure on hardness and impact strength of nanocomposite samples were investigated. The results showed that the effect of the carbon nanotube weight fraction on hardness and impact strength of nanocomposite samples was much higher than the effect of injection pressure. By adding 1%wt (weight) carbon nanotube into the polymer, the impact strength and hardness of the samples improved by 74% and 47%, respectively.

Effect of processing conditions on the structure, electrical and mechanical properties of melt mixed high density polyethylene/multi-walled CNT composites in compression molding

Abstract Processing conditions can significantly influence the structure and properties of polymer nanocomposites. In the present study, melt mixed high density polyethylene (HDPE)/multi-walled carbon nanotube (MWCNT) nanocomposites were prepared via twin-screw extrusion and then compression molded (CM). The effect of heating temperature, pressing time and cooling rate on the structure, electrical and mechanical properties of the CM nanocomposites was systematically investigated. Volume resistivity tests indicate that the nanocomposite with 2 wt.-% MWCNTs, which is in the region of the electrical percolation threshold, is very sensitive to the CM parameters such that heating temperature > pressing time > cooling rate. Generally, the resistivity of nanocomposites decreases with increasing heating temperature and pressing time. Interestingly, the electrical resistivity of the rapidly cooled nanocomposite with 2 wt.-% MWCNTs is about 2 orders lower than that of the slowly cooled nanocomposite which is attributed to the lower crystallinity and smaller crystallites presenting less of an obstacle to the formation of conductive pathways. The tensile properties of the nanocomposite with 2 wt.-% MWCNTs are also influenced by the compression molding parameters to some extent, while those of the nanocomposites with higher MWCNT loading are insensitive to the changes in processing conditions. The modulus of the nanocomposites increases by about 25 to 50 % and 110 to 130 %, respectively, with the incorporation of 2 and 4 wt.-% MWCNTs, which agrees well with the theoretical values predicted from Halpin-Tsai and Mori-Tanaka models. This work has important implications for both process control and the tailoring of electrical and mechanical properties in the commercial manufacture of conductive HDPE/MWCNT nanocomposites.

A wireless smart UV accumulation patch based on conductive polymer and CNT composites

A wearable, highly sensitive, and wireless UV patch was successfully fabricated to record the accumulative UV radiation in terms of resistance.

Rational synthesis of Ni3(HCOO)6/CNT ellipsoids with enhanced lithium storage performance: inspired by the time evolution of the growth process of a nickel formate framework.

Metal-organic frameworks (MOFs) as novel electrode materials have attracted intensive attention; however, low electronic conductivity hinders their practical application in lithium ion batteries (LIBs). This work reports the synthesis of conductive MOF/CNT composites with enhanced electrochemical reactivity. The growth mechanism of the pristine MOF and the correlations of two components are investigated from the viewpoint of crystal engineering. The time dependent morphology evolution experiment reveals that [Ni3(HCOO)6] undergoes an 'aggregation-based nucleation-growth' mechanism. As a result, [Ni3(HCOO)6]/CNT microsized ellipsoidal particles are controllably synthesized by tuning the reaction time and the reagent concentration, where CNTs penetrate the entire particles thoroughly. The obtained [Ni3(HCOO)6]/CNT composites exhibit significantly enhanced electrochemical activity in comparison with the as-synthesized pristine [Ni3(HCOO)6]. This is ascribed to the effective 3D conductive network constructed by CNTs. Our results provide an effective synthetic strategy to construct conductive MOF/CNT composites, which pave the way for developing other conductive MOFs for electrode materials.

Highly Conductive Wire: Cu Carbon Nanotube Composite Ampacity and Metallic CNT Buckypaper Conductivity

ABSTRACTCarbon nanotube (CNT) composites are being explored to improve the conductivity and density of electrical wire used in aviation. Presented are the current carrying capacity of a CNT-Cu composite and Roman spectroscopy and electrical conductivity of Buckypaper (BP) made of normal and sorted 95% metallic CNT (m-CNT). The ampacity of the Cu-CNT composite was 3.8% lower than pure Cu. This is significant because it is not in agreement with high CNT ampacity claims. The average conductivity of the CNT in the sorted, 95% metallic BP was 2.5 times higher than the CNT in the un-sorted BP. This shows the importance of the intrinsic CNT conductivity as opposed to interfacial resistances and that the conductivity of the semiconductor CNT present in the un-sorted BP must be much lower than the conductivity of m-CNT. The high conductivity of the sorted BP provides proof that conductivity improvements in CNT composites can be made by the use of sorted, highly conductive m-CNT.

Multi-walled carbon nanotube/polyethersulfone nanocomposites for enhanced electrical conductivity, dielectric properties and efficient electromagnetic interference shielding at low thickness

Herein, we report the synthesis of a high performance electromagnetic interference shielding (EMI) composite by utilizing polyethersulfone (PES) as a model matrix. Thin films of PES filled with conductive multi-walled carbon nanotubes (MWCNTs) were fabricated by a simple solution casting technique. The effect of filler concentration on EMI shielding efficiency, dielectric constant, electrical conductivity, hardness and thermal stability were investigated, and these properties were found to improve with the filler amount. An exceptionally high EMI shielding effectiveness of 35 dB (well above the common commercial EMI shielding requirement of 20 dB) was obtained in the X-band at a low thickness of 0.5 mm. Furthermore, the PES based CNT composites displayed a high electrical conductivity of 450 S/m. A high dielectric constant of 127 was obtained for a 20 wt% CNT filled polymer composite which was 40 times larger than the pure polymer matrix. Characterization tools indicate the intimate contact between the host matrix (PES) and CNT filler, which provided synergistic effects for improving dielectric properties as well as EMI shielding.