Multi-walled Carbon Nanotube Composites Research Articles

Upcycling Waste Plastics into Multi-Walled Carbon Nanotube Composites via NiCo2O4 Catalytic Pyrolysis

In this work, multi-walled carbon nanotube composites (MWCNCs) were produced by catalytic pyrolysis of post-consumer plastics with aluminium oxide-supported nickel, cobalt, and their bimetallic (Ni/α–Al2O3, Co/α–Al2O3, and NiCo/α–Al2O3) oxide-based catalysts. The influence of catalyst composition and catalytic reaction temperature on the carbon yield and structure of CNCs were investigated. Different temperatures (800, 900, 950, and 1000 °C) and catalyst compositions (Ni, Co, and Ni/Co) were explored to maximize the yield of carbon deposited on the catalyst. The obtained results showed that at the same catalytic temperature (900 °C), a Ni/Co bimetallic catalyst exhibited higher carbon yield than the individual monometallic catalysts due to a better cracking capability on carbon-hydrogen bonds. With the increase of temperature, the carbon yield of the Ni/Co bimetallic catalyst increased first and then decreased. At a temperature of 950 °C, the Ni/Co bimetallic catalyst achieved its largest carbon yield, which can reach 255 mg g−1plastic. The growth of CNCs followed a “particle-wire-tube” mechanism for all studied catalysts. This work finds the potential application of complex oxide composite material catalysts for the generation of CNCs in catalytic pyrolysis of wasted plastic.

High-performance and low-cost manganese oxide/multiwalled carbon nanotubes composite as cathode material for aqueous magnesium ion battery

• The λ-MnO 2 /MWCNTs composite was synthesized with feasible solution method and applied as cathode in aqueous magnesium ion battery for the first time. • The λ-MnO 2 particles are distributed in MWCNTs network structure, which increased the specific surface area and conductivity of electrode material. • The λ-MnO 2 /MWCNTs composite showed good electrochemical performances in three electrode and MnO 2 /MWCNTs//AC full cell systems. • The mechanism of magnesium ion insertion/deinsertion in λ-MnO 2 /MWCNTs electrode was investigated in this paper. The aqueous magnesium ion batteries (AMIBs) with the advantages of low cost, intrinsical safety and environmentally friendly have received worldwide attention as promising candidates for green energy storage system. Herein, we report a composite material engineered from λ-MnO 2 particles and multiwalled carbon nanotubes (MWCNTs) as cathode for AMIB. The λ-MnO 2 possesses a spinel-type crystalline structure, which is beneficial for the insertion/deinsertion of Mg 2+ ions. The MWCNTs network shorts ionic diffusion distance and increases the interface of electrode material/electrolyte. Hence, the λ-MnO 2 /MWCNTs composite demonstrates a large capacity of 251 mAh g −1 at 50 mA g −1 in 0.5 M MgCl 2 solution, and high capacity retention of 86.2 % after 1000 cycles at 1000 mA g −1 in MgSO 4 solution. Furthermore, the λ-MnO 2 /MWCNTs//AC system is firstly assembled as full AMIB, which delivers a specific capacity of 84.8 mAh g −1 at 100 mA g −1 . The rate capability test is performed at 300 mA g −1 . This system displays a gradually rise tendency in the specific capacity at initial 100 cycles on account of the activation process. After 1000 cycles, the specific capacity is 56.9 mAh g −1 . This work develops an easily prepared, low-cost and good performance electrode material for AMIB system.

Morphological: Optical, and Mechanical Characterizations of Non-Activated and Activated Nanocomposites of SG and MWCNTs

Nanocomposites of silica gel (SG) and multiwalled carbon nanotubes (MWCNTs) of relatively low concentrations (0.25, 0.50, and 0.75 wt%) were characterized before and after annealing. Adsorption is a surface phenomenon, and based on this, the morphology of the composites was investigated by scanning electron microscopy (SEM). The produced images show that the MWCNTs were embedded into the silica gel base material. Fourier transform infrared (FTIR) transmittance spectroscopy showed that MWCNTs were not functionalized within the matrix of silica gel and MWCNT composites. However, after annealing the composites at 400 °C for 4 h in air, evidence of activation was observed in the FTIR spectrum. The effects of the embedding of MWCNTs on porosity, specific surface area, and pore size distribution were studied using Raman spectroscopy. The Raman spectra of the prepared composites were mainly dominated by characteristic sharp scattering peaks of the silica gel at 480, 780, and 990 cm−1 and a broad band centered at 2100 cm−1. The scattering peaks of MWCNTs were not well pronounced, as the homogeneity of the composite is always questionable. Nanosizer analysis showed that at 0.25 wt%, the distribution of MWCNTs within the silica gel was optimal. Vickers hardness measurements showed that the hardness increased with the increasing weight percent of MWCNTs within the composite matrix, while annealing enhanced the mechanical properties of the composites. Further studies are required to investigate the pore structure of silica gel within the matrix of MWCNTs to be deployed for efficient cooling and water purification applications.

Strain‐sensing behavior of flexible polypropylene/poly(ethylene‐co‐octene)/multiwalled carbon nanotube nanocomposites under cyclic tensile deformation

AbstractIn this study, the associations between the structural evolution and physical properties of polypropylene/poly(ethylene‐co‐octene)/multiwalled carbon nanotube (PP/POE/MWCNTs) composites were established. The MWCNTs particles preferentially migrating from PP matrix to disperse in POE phase, which contributed to a richer network structure, thus resulting in a significant improvement for electrical conductivity, as well thermal stability, and toughness property with the elongation at break from 300% to 800%. Furthermore, the online strain‐resistance analysis showed that introducing POE phase had a big advantage in improving the recovering resilience and stability of the conductive network structure of PP/POE/MWCNTs composites under a multi‐time circular tensile test with a strain of 5%. It was highlighted that the maximum and minimum electrical conductivity levels of PP/POE composites remained almost constant and even the ratio of the real‐time resistance to the initial one was negative just at the beginning of each circulation regarding the strain stretching and recovery. This was attributed to the oriented conductive network structure of PP/POE nanocomposites induced by the applied strain, thereby increasing the electrical conductivity. Overall, this research provides a basic guidance for preparing composites with ultrahigh flexibility and stability under a circular deformation, which is an essential element taken into consideration for smart sensors with high sensitivity.

Determination of photocatalytic process parameters on phenol degradation using TiO2-MWCNT (cocoPAS) composite

Multi-walled carbon nanotubes (MWCNT) were prepared by treatment of cocoPas and titanium dioxide nanocomposites TiO2 – MWCNT (cocoPAS) prepared by stirring and mixing method was used as a photocatalyst for the degradation of phenol in water under light irradiation. The morphology and microstructure of the composites were characterized with SEM, FT-IR, BET, XRD and UV-visible spectrophotometer. The purpose of this study were synthesize TiO2-MWCNT (cocoPAS) composite and evaluate its performance for photodegradation phenol. It was found that the degree of photodegradation of phenol under UV light was highly dependent on the concentration of phenol and the degradation temperature. The presence of MWCNT worked as the adsorbent and electron acceptor to efficiently enhance the phenol photodegradation. The as-prepared nanotubes, with surfactant contents, showed high- photocatalytic activities with increase degradation. These results indicate that TiO2 – MWCNT (cocoPAS)composites using cocoPAS can be used to enhance degradation and can expand potential applications for the degradation of organic pollutants.

Peeling behaviors of epoxy based multi-walled carbon nanotubes (MWCNTs) composites and surface deposited silver interface: A comparative study of MWCNTs with different diameter and surface functionalization

Incorporating nano fillers such as multi-walled carbon nanotubes (MWCNTs) into polymeric matrix can generate rough surface and transfer stress directly to improve adhesion of metal-polymer interfaces. However, the interfaces became more complicate to optimize the adhesion. In this work, the effects of MWCNTs with different surface chemical groups and different diameter on surface profile, wettability and adhesion were studied. The results showed that the adhesion was related to surface wettability when using pristine MWCNTs and this relationship was extinct after the MWCNTs were functionalized. Out of the intuition, the functionalization was not with perfect universality in improving adhesion. D peaks were expanded with the ID/IG and FWHM of A1 and A4 increased by dual functionalization from 0.33 to 0.62, 92.39 to 105.91 cm−1 and 0.49 to 1.63, 140.47 to 172.24 cm−1, respectively. We found that the adhesion of functionalized MWCNTs depended on multiple factors including surface roughness, wettability, the intrinsic mechanical property of MWCNTs, and stress distribution on MWCNT surface when combined with the surface enhanced Raman spectroscopy (SERS) results. This work will be inspiring for novel technology of metal-polymer interfacial modification.

Preparation and Catalytic Activity of Platinum Supported on Amine-Functionalized MIL-101 (Fe)/Nitrogen-Doped Carbon Nanotube Composite for Fuel Cells.

Pt-supported on amine functionalized MIL-101 (Fe) and nitrogen doped multi-walled carbon nanotube (CNT) composites were synthesized by hydrothermal synthesis and pyrolysis process. Electrochemical properties were measured by cyclic voltammetry (CV), chronoamperometry (CA) and structural analysis was done by field emission scanning electron microscopy (FE-SEM) and Fourier transform infrared spectroscopy (FT-IR). As a result, higher electrochemical surface area (ECSA) and methanol oxidation reactions were obtained, and the electrochemical properties of Pt-c(NH₂-MIL-101)@NCNT are better than pristine Pt-c(NH₂-MIL-101). The enhanced activity related with the synergy effect from the higher conductivity of N-doped CNT and the better porous nanostructure of carbonized NH₂-MIL-101(Fe).

Tunable Humidity-Sensing Performance of Graphene Oxide With Leaf-Vein-Like Multiwall Carbon Nanotube Conductive Networks

In this study, we report the humidity-sensing performance of 1,6-hexanediamine modified graphene oxide (HAGO) and functionalized multiwall carbon nanotube (fMWCNT) composites. The negatively charged fMWCNTs are randomly attached to the surface of positively charged HAGO (so-called electrostatic self-assembly), forming a leaf-vein-like conductive network. The relative resistance response of fMWCNTs/HAGO humidity sensors can be well-tuned by varying the content of fMWCNTs. The results demonstrate that the sensor based on 1:4 mass ratio of fMWCNTs/HAGO composite possesses the high relative resistance response, good repeatability and excellent stability. The decrease of mass proportion of fMWCNTs can result in the decrease of response time as well as hinder the recovery process. The resistance change of fMWCNTs/HAGO sensors over a wide range of relative humidity (35-95%) can be well fitted with the Henry-clustering model.

Tunable Multilevel Data Storage Bioresistive Random Access Memory Device Based on Egg Albumen and Carbon Nanotubes.

In this paper, a tuneable multilevel data storage bioresistive memory device is prepared from a composite of multiwalled carbon nanotubes (MWCNTs) and egg albumen (EA). By changing the concentration of MWCNTs incorporated into the egg albumen film, the switching current ratio of aluminium/egg albumen:multiwalled carbon nanotubes/indium tin oxide (Al/EA:MWCNT/ITO) for resistive random access memory increases as the concentration of MWCNTs decreases. The device can achieve continuous bipolar switching that is repeated 100 times per cell with stable resistance for 104 s and a clear storage window under 2.5 × 104 continuous pulses. Changing the current limit of the device to obtain low-state resistance values of different states achieves multivalue storage. The mechanism of conduction can be explained by the oxygen vacancies and the smaller number of iron atoms that are working together to form and fracture conductive filaments. The device is nonvolatile and stable for use in rewritable memory due to the adjustable switch ratio, adjustable voltage, and nanometre size, and it can be integrated into circuits with different power consumption requirements. Therefore, it has broad application prospects in the fields of data storage and neural networks.

Evaluation of Ultimate Strength and Fundamental Frequency of Fiber/Epoxy and Fiber/Al6061 Composite Plate

Polymers and metal composites have emerged as a significant class of materials for cutting-edge engineering applications in the current material research and development environment because of their low cost, ease of design and manufacturing, and excellent and enhanced mechanical performances. The motto behind the present work is to develop a class of such materials and to study the mechanical properties of epoxy-based Glass (G/E), Graphite (Gr/E), Aramid (A/E), Carbon HM Types (C/E), and Multi-Walled Carbon Nanotube Composites (MWCNT/E) and aluminum-based MWCNT composites. An analytical solution and finite element analysis are used to evaluate and obtain the optimum mechanical properties of the lamina of the composites, such as ultimate longitudinal tensile strength, transverse tensile strength, shear strength, and the fundamental frequency of the composite plate analysis. All-side fixed boundary conditions have been used in the present study. In addition to the above, a detailed demonstrative analysis based on the after-effects of the modulus ratio and the volume fraction of the fiber on the ultimate tensile strength has also been made. In addition, the CNT AMC plate has been examined, with the findings being compared to the composite plate of Epoxy Metal Matrices (EMCs).

Bismuth Sulfide Strongly Coupled to Functionalized MWNTs Hybrids with Improved Thermoelectric Properties

AbstractThe efficiency of thermoelectric (TE) materials depends on an interplay between various material properties, and strategies for co‐optimizing these properties will be necessary for implementing these materials in the future. In this work, bismuth sulfide (Bi2S3) and acid treated multiwalled carbon nanotube (f‐MWNT) composites are fabricated by wet chemical synthesis at room temperature. Bi2S3 is intimately anchored onto the surface of the f‐MWNT to form a coaxial nanostructure. The power factor of the composite is enhanced relative to both the pure Bi2S3 and MWNTs, due to a large enhancement of the electrical conductivity. The enhanced conductivity is attributed to restructuring of the bismuth (Bi) and oxygen (O) bonding environments when Bi2S3 is chemically interfaced with the f‐MWNTs, suggestive of the formation of a strongly coupled complex via BiO/BiS bonds. Strong‐coupling is further supported by scanning transmission electron microscopy, Raman, and diffuse reflectance spectroscopy, which reveal fast charge‐transfer between the Bi2S3 and MWNT when interfaced together. These results support material compositing as a potential strategy for engineering enhanced TE materials.

In-situ synthesis and thermal properties of biobased Poly(neopentyl glycol 2,5-furandicarboxylate)/multi-walled carbon nanotubes composites

The in-situ synthesis and thermal properties of biobased poly(neopentyl glycol 2,5-furandicarboxylate) (PNF)/multi-walled carbon nanotubes (MWCNTs) composites were studied in this research. The chemical structure, thermal stability, crystallization behavior, and crystal structure of PNF/MWCNTs composites were extensively investigated and compared with those of PNF. Scanning electron microscopy image revealed that MWCNTs uniformly dispersed in PNF matrix. In the composites, MWCNTs slightly improved the thermal stability of PNF, while the crystallization of PNF was obviously enhanced by MWCNTS under both the nonisothermal and isothermal crystallization conditions as the heterogeneous nucleating agent. Only 0.5 wt% of MWCNTs obviously increased the melt crystallization temperature from 132.9 °C for neat PNF to 141.2 °C for the composite and decreased the crystallization half-time from 3.1 min for neat PNF to 1.9 min for the composite at 165 °C. In addition, MWCNTs did not modify the crystal structure of PNF.

Corrosion Resistance of Al-CNT Metal Matrix Composites.

The design of aluminium–graphite metal matrix composites (MMCs) with advanced mechanical properties and high corrosion resistance is in demand for aerospace, transportation, and industrial applications. Breakthroughs in this field are limited due to the tendency of aluminium–graphite MMCs to corrode. In the present research, aluminium-based MMCs were produced by a relatively novel combined two-staged method. Multiwall carbon nanotubes (MWCNTs) were added into molten Al1070 and processed by high-pressure die casting followed by cyclic extrusion. For the composites produced by this method, it was previously demonstrated that mechanical properties are improved in comparison with pure aluminium alloys. In the current study, the manufactured Al–MWCNT composites were investigated by electrochemical tests (such as open circuit potential), potentiodynamic tests, linear polarization tests, and electrochemical impedance spectra to understand the corrosion resistance of the obtained composite material. The experimental testing of the corrosion resistance of Al–MWCNT MMCs showed that due to the advantages of the fabrication method, the addition of CNTs to aluminium does not cause a radical decrease of corrosion resistance.

Beneficial stilbene-based derivatives: From the synthesis of new catalytic photosensitizer to 3D printouts and fiber-reinforced composites

New meta- and para-cyanoderivatives of 1,4-di(styryl)benzene and 1,3-di(styryl)benzene were synthesized and investigated for their use as photosensitizers of iodonium salt for various photopolymerization processes. Detail spectroscopic characteristic of this compound were performed, and the mechanism of initiation in binary photoinitiating system together with iodine salt was discussed and confirmed by experiments. Using real-time FTIR, the usefulness of the proposed meta- and para-cyanoderivatives of 1,4-di(styryl)benzene and 1,3-di(styryl)benzene as highly efficient photosensitizers for various photopolymerization processes was tested, including: free-radical photopolymerization of acrylate monomer or cationic photopolymerization of epoxy and glycidyl monomers. In addition, the formation of interpenetrating polymer networks with the use of proposed two-component initiating systems was performed. Encouraged by excellent polymerization results with the use of the developed initiating systems, additional application tests were carried out, including: 3D printing using vat polymerization, visible based direct ink writing, preparation of various fiber-reinforced composite or formation of multiwalled carbon nanotubes composites (MWCNTs nanocomposites), for which the manufacturing process has been analyzed in detail using real-time FTIR method.

Radiation synthesis of polyacrylamide/functionalized multiwalled carbon nanotubes composites for the adsorption of Cu(II) metal ions from aqueous solution

Radiation synthesis of polyacrylamide/functionalized multiwalled carbon nanotubes composites for the adsorption of Cu(II) metal ions from aqueous solution

Development of an Electrochemical Sensor Based on Nanocomposite of Fe3O4@SiO2 and Multiwalled Carbon Nanotubes for Determination of Tetracycline in Real Samples

In this work, an electrochemical sensor (GCE/MWCNT/Fe3O4@SiO2) based on a composite of multiwalled carbon nanotubes (MWCNT) and an Fe3O4@SiO2 (MMN) nanocomposite on a glassy carbon electrode (GCE) was developed for the detection of tetracycline (TC). The composite formed promoted an increased electrochemical signal and the stability of the sensor, combining its individual characteristics such as high electrical conductivity and large surface area. The composite material was characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Mössbauer spectroscopy, and scanning electron microscope (SEM). The adsorptive stripping differential pulse voltammetry (AdSDPV) promoted better performance for the electrochemical sensor and greater sensitivity for TC detection. Under optimized conditions, the currents increased linearly with TC concentrations from 4.0 to 36 µmol L−1 (0.997) and from 40 to 64 µmol L−1 (0.994) with detection and quantification limits of 1.67 µmol L−1 and 4.0 µmol L−1, respectively. The sensor was applied in the analysis of milk and river water samples, obtaining recovery values ranging from 91–117%.

A probe-free electrochemical immunosensor for methyl jasmonate based on ferrocene functionalized-carboxylated graphene-multi-walled carbon nanotube nanocomposites

Methyl jasmonate (MeJA) is an endogenous plant hormone, which plays an important role in agriculture production. A novel probe-free electrochemical immunosensor was fabricated for detecting of MeJA. Fc, carboxylated graphene (COOH-GR) and carboxylated multi-walled carbon nanotubes (COOH-MWNT) composite was formed and used to fabricate screen-printed electrode (SPE). Fc was used as the electronic medium. COOH-GR and COOH-MWNT were used to improve the conductivity and catalytic activity of the sensor and to immobilize the MeJA antibody. Thus, the immunosensor can be used to detect MeJA without external redox probe solution. The designed sensor can detect MeJA in a wide range of 100 fM-100 μM, and its detection limit is as low as 31.26 fM (S/N = 3). The as-prepared probe-free immunosensor is simple, low cost, and does not need redox probe solutions for measurements, which shows great promise for future application in precision agriculture.

Properties of Surface Heating Textile for Functional Warm Clothing Based on a Composite Heating Element with a Positive Temperature Coefficient.

A high-stretch positive temperature coefficient (PTC) surface heating textile (PTC-SHT) was fabricated using a composite of PTC powder and multiwall carbon nanotubes (MWCNTs). The PTC-SHT (heating area = 100 × 100 mm2) was produced by screen-printing the PTC-MWCNT composite paste onto a high-stretch textile with embroidered electrodes. Overall, the temperature increased to 56.1 °C with a power consumption of 5 W over 7 min. Subsequently, the surface temperature of the PTC-SHT remained constant despite the continued decrease in power consumption. This indicated that heating was accompanied by an increase in resistance of the PTC-SHT, which is typical of this process—i.e., heating to a constant temperature under a constant voltage over an extended period of time. In addition, 4.63 W power was required to heat the PTC-SHT surface from an external temperature of 5 to 45 °C in 10 min, after which stable low-temperature heat generation behavior was observed at a constant temperature of 50 °C, which was maintained over 40 min. In contrast, negative temperature coefficient (NTC) behavior has been observed in an NTC-SHT consisting of only MWCNTs, where a slow heating rate in the initial stage of power application and a continuous increase in surface temperature and power consumption were noted. The PTC-SHT consumed less power for heat generation than the NTC-SHT and exhibited rapid heating behavior in the initial stage of power application. The heat generation characteristics of the PTC-SHT were maintained at 95% after 100,000 cycles of 20% stretch–contraction testing, and the heating temperature remained uniformly distributed within ± 2 °C across the entire heating element. These findings demonstrated that an SHT with PTC characteristics is highly suitable for functional warm clothing applications that require low power consumption, rapid heating, stable warmth, and high durability.

Fabrication and Characterization of Cold-Pressed and Sintered Aluminium - MWCNT Composites

In the present article aluminium matrix composites were fabricated by cold pressing and sintering technique. Multi-walled carbon nanotube (MWCNT) with various weight percentage 0.5, 1.0, 1.5 and 2.0 were added as a reinforcement to aluminium (Al) matrix. A planetary ball mill was used for mechanical alloying and even dispersion of carbon nanotubes (CNTs) in aluminium matrix. Tin (Sn) with 1.0 weight percent was used in composite to incite the sintering. The sintering was carried out at 500°C inside a tube furnace in an argon atmosphere. The morphology and structure of CNT and Al-Sn-CNT composite was characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and Raman spectroscopy. The effect of MWCNT reinforcement on microhardness and wear properties of Al-Sn-CNT composite was investigated. The hardness of composites was improved significantly with increase in CNT fraction. The reduction in the coefficient of friction and improvement in the wear resistance of the Al-Sn-CNT composite was noticed with the increase in percentage of CNTs in the composite.

Sorptive removal of methylene blue from water by magnetic multi-walled carbon nanotube composites.

In the present study, five magnetic multi-walled carbon nanotubes (MMWCNTs) with different diameters were prepared and their performance on the sorptive removal of methylene blue (MB) from water was investigated. Transmission electron microscope, scanning electron microscope, Fourier transform infrared spectrometer, X-ray diffraction, and vibrating sample magnetometer confirm that the surface of these MMWCNTs has been decorated by Fe3O4 nanoparticles, which renders the MMWCNTs superparamagnetic. Thus, these MMWCNTs can be easily separated from water after the adsorption. During the adsorption process, pH slightly affected the removal efficiency of MB and the adsorption performed better under weak alkaline conditions. Adsorption kinetics followed the pseudo-second-order kinetic model well, and the Dubinin-Radushkevich model fitted the isotherms best. The maximum adsorption capacity for MB reached 204.2 mg/g, and the values decreased with increasing diameters of MMWCNTs due to decreasing specific surface areas. The thermodynamics parameters indicated the spontaneous and exothermic nature of the adsorption. The reusability test showed that MMWCNTs could be used for 6 cycles without significant loss of the adsorption capacity. And common ions (K+, Na+, Ca2+ and Al3+) and SDS in water did not show greatly effects on the removal efficiency of MB. Hence, MMWCNTs prepared in this study could be promising adsorbents for dyes removal from wastewater.