Mixed Multi-walled Carbon Nanotubes Research Articles

Electronic Skin as Human–Robot Interface for Human Grasp Recognition in Home-Care Robots: Introducing a Complete Set of Resources

Population aging has highlighted the significance of developing home-care robots to assist human life. However, traditional home-care robots work according to fixed procedures, which lack human–robot interaction to mimic human hand action. Human–robot interfaces provide an opportunity for interactions between robots and users, which play an important role in home-care robots. Traditional human–robot interfaces are based on rigid, cumbersome, and high-priced machines, which prevent their wide application in performing home-care tasks. An e-skin sensor with 11 stretchable resistors evenly distributed on the back of the human hand, which could be applied to monitor human finger motion and control robotic fingers to dexterously grasp diverse objects, is presented in this article. A 3D printer is employed to pattern high-performance wires into structurally soft and stretchable filamentary serpentines. The stretchable resistors are fabricated by a thin sensing film of mixed multiwalled carbon nanotubes (MWCNTs) and silicone elastomer. The e-skin sensor is applied in a hand-in-the-loop system for controlling a robotic hand to help grasp an object synchronously. A robot system is developed to connect the e-skin with the robotic hand to perform grasp actions with a success rate of more than 80%. By analyzing the experimental results of the e-skin sensor and robotic hand grasp, this work obtains insights showing that the skin sensor can help engineers design a home-care assistant plan for patients according to monitoring value or a human–robot interaction mode by robotic fingers mimicking human finger actions.

Investigation of the mechanical and thermal properties of epoxy adhesives reinforced by carbon nanotubes and silicon dioxide nanoparticles in single-lap joints

In this study, the shear strength and thermal properties of the adhesively bonded joints were investigated of adhesives reinforced with nanoparticles using carbon fiber-reinforced composite materials. The diglycidyl ether bisphenol A (DGEBA) was used as the epoxy resin. Single lap joint tests of 1% wt. Multi-walled carbon nanotubes (MWCNT) and 3, 5, and 7% wt. silicon dioxide (SiO2) nanoparticle-reinforced mixed adhesives were performed according to ASTM D5868 standards. The shear strengths of the mixed adhesives obtained by mixing at different ratios were compared with the epoxy resin. Upon conducting an analysis of the shear strengths of nanomaterials, results indicate that the incorporation of 1CNT + 3SiO2 in the nanomaterials showed the greatest improvement, with a 46% increase in shear strength. 1CNT + 5SiO2, 1CNT, and 1CNT + 7SiO2 showed increases of 32%, 14%, and 5%, respectively. The results of a tensile test indicate that pure epoxy exhibited a tensile strength of 5953 N, 1CNT, and 3SiO2, while the epoxy composite demonstrated a significantly higher tensile strength of 8738 N, along with an elongation of 0.72 mm. In addition, the morphology of fractured surfaces was examined by scanning electron microscopy (SEM). To investigate damage mechanisms, such as bridging, crack blunting, and branching of nanoparticles were observed. Characterization of epoxy resin and mixed MWCNT + SiO2 nanoparticles reinforced adhesives were also performed using Fourier infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), and differential thermal analysis (DTA). Nanoparticles are settled between polymer chains, improving polymer chains’ motion and thermal properties.

Development of a Pd-xCNT-Ni-yCB composite catalyst to enhance the oxidation of various alcohols in alkali mediums

Developing a comprehensive strategy and superior catalysts for alcohol oxidation is essential for real applications of direct alcohol fuel cells. By adding palladium (Pd) onto the nickel (Ni) nanoparticles loaded on a mixed multiwalled carbon nanotubes (CNTs) and carbon black (CB) support by a reduction method with 10 wt% Pd and 10 wt% Ni, various weight ratios carbon compositions of Pd-xCNT-Ni-yCB catalyst materials (x and y = 1–2) were also studied. Well-dispersed Pd nanoparticles with average particle sizes of 3.3 and 5.5 nm were present on the 1CNT-Ni-2CB and 1CNT-2CB composite supports, respectively. X-ray photoelectron spectroscopy (XPS) analysis indicated that Pd exhibits a metallic palladium surface state with some fraction of NiO and Ni(OH)2 species. Alcohol oxidation e.g., methanol, ethanol, and iso-propanol in alkaline electrolytes was investigated by electrochemical measurements and analysis. Compared with single carbon catalysts, e.g., Pd-CNT and Pd-CB catalysts, in studies involving methanol, ethanol and isopropanol oxidation, most Pd-xCNT-Ni-yCB catalysts show high activity. The best performance obtained by Pd-1CNT-Ni-2CB could be related to the increased kinetics reaction and instantaneous presence of the bifunctional mechanism and electronic effect, resulting in a Pd and Ni alloy with a small amount of Ni(OH)2 in the xCNT-Ni-yCB composite support surfaces.

ANFIS based effectiveness and number of transfer units predictions of MWCNT/water nanofluids flow in a double pipe U-bend heat exchanger

In this study, the heat transfer coefficient, Nusselt number, effectiveness and number of transfer units of water mixed multi-walled carbon nanotubes nanofluids passes through a tube-in-tube heat exchanger was experimentally investigated. Investigations were performed in the operating conditions of Reynolds number ranging from 3500 to 12000 and volume concentrations ranging from 0% to 0.3%, respectively. The obtained four parameters were predicted using adaptive neuro fuzzy inference system (ANFIS). The Reynolds number and particle volume loadings are the input data in artificial neural network analysis and heat transfer coefficient, Nusselt number, effectiveness and number of transfer units is output or target. The Nusselt number, heat transfer coefficient, effectiveness, and number of transfer units was enhanced to 31.3%, 44.17%, 2.51% and 2.76% at φ = 0.3% and at a Re of 10005, against base fluid. Implementation of ANFIS with various quantities of neurons in the mid layer provides 1–10−6 with the correlation coefficient (R2) of 0.9978, and 0.9998 and root mean square error of 0.0018581, and 0.0014159 for heat transfer coefficient and Nusselt number, respectively. The above developed structure has been successful in predicting 96% of variation in all the parameters.

Fabrication of Freestanding Flexible Electrode Based on PEDOT:PSS Polymer Composite for Li – S Batteries

Currently, Poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) is considered a promising composite in energy conversion and storage devices due to its high electrical conductivity, chemical stability, outstanding flexibility and great electrochemical properties. Owing to its favorable mechanical and electrical properties PEDOT:PSS has wide applications in transparent electrodes, photovoltaics, fuel cells, supercapacitors and lithium-ion batteries [1-2]. Flexible free-standing sulfur @ MWCNT @ PEDOT:PSS composite films might be prepared using various techniques such as vacuum infiltration, facile solution mixing method, rod-coating technique, hydrothermal method, and doctor-blade technique [3]. In our review, we synthesized PEDOT:PSS @ sulfur@ MWCNT composite film by a doctor-blade technique onto the polypropylene (PP) substrate. First, the cathode composite was prepared by mixing multi-walled carbon nanotubes (MWCNT) composite with a sulfur content 1:1, PEDOT:PSS water-based dispersion and DMSO as a solvent to form a homogeneous slurry. The slurry was coated onto PP substrate by doctor-blade method and subsequently dried in a vacuum oven. Furthermore, sulfur @ MWCNT @ PEDOT:PSS film was structurally characterized by scanning electron microscopy (SEM) analysis. SEM images show the flexible film, which exhibits a network structure formed by interpenetration of MWCNTs and PEDOT:PSS. Sulfur nanoparticle clusters are surrounded by CNT networks, forming intimate interfaces with each other. According to EDS results, uniform distribution of each element can be observed. Acknowledgement This work was supported by the research projects АР08052143 “Development of Wearable Self-Charging Power Unit” from the Ministry of Education and Science of the Republic of Kazakhstan.

Failure analysis of self-healing epoxy resins using microencapsulated 5E2N and carbon nanotubes

Investigation on self-healing properties of epoxy containing microcapsules of pure 5-ethylidene-2-norbornene (5E2N) and mixed multi-walled carbon nanotube (MWCNT) suspension is presented in this work using lap shear and mode I fracture tests. While both systems show significant self-healing functionalities between 39% and 97%, those repaired with MWCNT/5E2N microcapsules are found to have mechanical recovery efficiencies two times higher than those containing 5E2N alone, under different types of loading. MWCNT/5E2N microcapsules are also found to improve the physical strength of the epoxy matrix much higher than microcapsules containing only 5E2N. Compared to self-healing epoxy systems made of 5E2N microvessels, the dispersion of 0.10 wt.% of only MWCNTs inside the encapsulated monomer increases the lap shear strengths of the pristine materials and the self-healing materials tested after one fracture/curing cycle, by about 50% and 250%, respectively. Using fractographic observations, Raman spectroscopy and scanning electron microscopy, we observe the occurrence of a ring opening metathesis polymerization reaction and the contribution of MWCNTs to strengthening the material. The present work indicates that the MWCNT/5E2N microcapsule when incorporated into an appropriate epoxy formulation can serve as efficient self-healing matrix material for laminated composites, as well as self-healing structural adhesives for composite bonded joints, two features that make this system highly relevant for applications in aerospace engineering.

Optimization of the fabrication conditions and effects of multi-walled carbon nanotubes on the tensile properties of various glass fibers/unsaturated polyester resin composites

Abstract Conventional glass fiber/unsaturated polyester resin (UPR) composites were fabricated by four layers to verify the optimum fabrication conditions such as the initial curing temperature, fiber changes and vacuum. Before that another optimum condition for stir mixing multi-walled carbon nanotubes (MWCNTs) into UPR was further investigated based on the initial curing temperature. Exothermic temperature measurements, density measurements, thermo-gravimetric analysis and tensile testing were utilized to identify the effects of these factors on the UPR and composite laminates. Consequently, an initial curing temperature range of 25°C–35°C was recommended to start the polymerization. In addition, the fiber combination and applying vacuum were also represented as the other optimum conditions in composite fabrication. The optimum initial curing temperature was applied for modifying UPR with 0.1 wt.% MWCNTs. Then, all of optimum conditions were used to fabricate glass fibers/modified UPR composites. The higher tensile strength and modulus of fiber combination with the adding of MWCNTs were obtained at 25.29 MPa and 1.39 GPa, respectively. The results indicate that simple MWCNT mixing can be used in industry due to the reduction of the fabrication time and better tensile properties.

Thermal, mechanical and tribological properties of polyamide 6 matrix composites containing different carbon nanofillers

Abstract Polyamide 6 (PA6) matrix composites were prepared by incorporating multiwalled carbon nanotubes (MWCNTs) or by co-incorporating MWCNTs and carbon black (CB) of different contents. The thermal, mechanical and tribological properties of the composites were investigated using thermogravimetric analysis, nano-indentation, ball-on-disc micro-tribological test and micro-scratch test. It was found that a proper carbon filler content in the composites promoted the thermal stability of the composites, but an excessive loading of carbon fillers degraded the thermal stability of the composites. Although the hardness of the composites decreased with increased carbon filler content, the composites filled with mixed MWCNTs and CB had a higher load bearing capacity than the ones without CB. The tribological results indicated that the increased carbon filler content apparently lowered the friction coefficient of the composites due to the lubricating effect of the carbon fillers. It was also observed that the friction coefficients of the PA6-MWCNT-CB composites were consistently higher than those of the PA6-MWCNT composites due to the lower wear resistance of the PA6-MWCNT-CB composites. The scratch resistance of the composites decreased with increased carbon filler content due to the reduced cohesive strength of the composites.

Dynamic crosstalk analysis of mixed multi‐walled carbon nanotube bundle interconnects

Multi-walled carbon nanotube (MWCNT) bundles have potentially provided attractive solutions in current nanoscale VLSI interconnects. From fabrication point of view, it is difficult to control the growth of a densely packed bundle having MWCNTs with similar diameters. A realistic bundle is combination of MWCNTs with different number of shells. Thus, this research work focuses on the analytical model of a bundle having the MWCNTs with different number of shells or in turn different diameters (mixed MWCNT bundle (MMB)). Based on the multi-conductor transmission line theory, an equivalent single conductor (ESC) model is employed for the proposed MMB arrangements. The ESC model of MMB is used to compare the dynamic crosstalk delay with conventionally arranged bundle containing MWCNTs with similar diameters (MWCNT bundle (MB)) under different input transition time and spacing conditions. It is observed that a realistic MMB correctly estimates the crosstalk delay for the different transition time that overestimates the delay of a conventionally arranged MB by 1.35 times. Moreover, the MMB arrangement reduces the overall crosstalk delay by 47.26% compared with the conventional MB arrangements for an inter-bundle spacing ranging from 5 to 30 nm.

Synthesis and Electrochemical Performance of LiV<sub>3</sub>O<sub>8</sub>/MWCNTs Cathode Material for Lithium-Ion Batteries

Layered LiV3O8cathode material was prepared by sol-gel method using ethylene diamine tetra-acetic acid (EDTA) as chelon, and LiV3O8/MWCNTs composite materials were fabricated by mixing multi-walled carbon nanotubes (MWCNTs) and LiV3O8particles via ball milling technic. X-ray diffraction (XRD), scanning electron microscopy (SEM), galvanostatic charge-discharge experiments were employed to characterize the material structure, morphology and electrochemical properties respectively. The results show that the layer structure of LiV3O8did not change after doping MWCNTs, and the LiV3O8/MWCNTs composite showed excellent electrochemical performance. The initial specific discharge capacity of the 2% MWCNTs （mass percent） composites can reach 217.5 mAh/g at 0.1C discharge rate in the potential region 1.8-4.0V, and maintains a stable capacity of 224.9 mAh/g within 30 cycles. Comparing to the LiV3O8/MWCNTs, the capacity of pure LiV3O8samples can only remain 86% intetial specific capacity at the same test conditions.

Synthesis and Electrochemical Performance of LiV<sub>3</sub>O<sub>8</sub>/MWCNTs Cathode Material for Lithium-Ion Batteries

Layered LiV3O8 cathode material was prepared by sol-gel method using ethylene diamine tetra-acetic acid (EDTA) as chelon, and LiV3O8/MWCNTs composite materials were fabricated by mixing multi-walled carbon nanotubes (MWCNTs) and LiV3O8 particles via ball milling technic. X-ray diffraction (XRD), scanning electron microscopy (SEM), galvanostatic charge-discharge experiments were employed to characterize the material structure, morphology and electrochemical properties respectively. The results show that the layer structure of LiV3O8 did not change after doping MWCNTs, and the LiV3O8/MWCNTs composite showed excellent electrochemical performance. The initial specific discharge capacity of the 2% MWCNTs （mass percent） composites can reach 217.5 mAh/g at 0.1C discharge rate in the potential region 1.8-4.0V, and maintains a stable capacity of 224.9 mAh/g within 30 cycles. Comparing to the LiV3O8/MWCNTs, the capacity of pure LiV3O8 samples can only remain 86% intetial specific capacity at the same test conditions.

Energy dissipation behaviors of surface treated multi-walled carbon nanotubes-based nanofluid

A nanofluid with good energy dissipation property was fabricated by mixing multi-walled carbon nanotubes (MWCNTs) and a nonwetting high surface tension liquid. Surface treatment of MWCNTs with various organic functional groups was performed to improve the energy dissipation capability of the fluid. The test results indicated that the chain length of the grafted organic groups had a critical effect on the energy dissipation property. Furthermore, an optimum chain length of the grafted organic groups, the length of the Dodeca-fluoroheptyl-propyl-trimethoxysilane, was obtained to make the specific pore-diameter MWCNTs-based nanofluid achieve the maximum infiltration pressure and energy dissipation capability. Additionally, more liquid came out of the long-chain treated MWCNTs after a loading-unloading process.

Study on Sensing Properties of Electro-spun PEO/MWNT Non-woven Fabric

This paper presents a study on the sensing properties of a conductive polymer composite (CPC) that is processed by an electrospinning technique. The CPC is obtained by mixing multi-walled carbon nanotubes (MWNT) with a poly (ethylene oxide) (PEO) matrix. Sensors made of this composite are characterised by measuring their electrical properties as a function of external stimuli. In particular, their responses to vapours of toluene, methanol and dioxan are investigated. As studied, the PEO/MWNT material shows high and stable sensitivity over three testing cycles for the selected vapours. An increase in electrical resistance is observed under the influence of chemical substances. This paper supports the concept that penetration of molecules of selected chemical substances leads to the partial disorder of contact between neighboured nanotubes located in the polymer matrix. The electro-spun non-woven fabric with a low amount of MWNT (3 wt.%) in the PEO matrix seems to be a good textile product for application as sensing membranes in personal protective clothing.

Morphology, mechanical, cross-linking, thermal, and tribological properties of nitrile and hydrogenated nitrile rubber/multi-walled carbon nanotubes composites prepared by melt compounding: The effect of acrylonitrile content and hydrogenation

The purpose of this work was to prepare nanocomposites by mixing multi-walled carbon nanotubes (MWCNT) with nitrile and hydrogenated nitrile elastomers (NBR and HNBR). Utilization of transmission electronic microscopy (TEM), scanning electron microscopy (SEM), and small- and wide-angle X-ray scattering techniques (SAXS and WAXS) for advanced morphology observation of conducting filler-reinforced nitrile and hydrogenated nitrile rubber composites is reported. Principal results were increases in hardness (maximally 97 Shore, type A), elastic modulus (maximally 981MPa), tensile strength (maximally 27.7MPa), elongation at break (maximally 216%), cross-link density (maximally 7.94×1028m−3), density (maximally 1.16gcm−3), and tear strength (11.2kNm−1), which were clearly visible at particular acrylonitrile contents both for unhydrogenated and hydrogenated polymers due to enhanced distribution of carbon nanotubes (CNT) and their aggregated particles in the applied rubber matrix. Conclusion was that multi-walled carbon nanotubes improved the performance of nitrile and hydrogenated nitrile rubber nanocomposites prepared by melt compounding.

EFFECT OF MULTI-WALLED CARBON NANOTUBES ON THE PROPERTIES OF POLYOXYMETHYLENE

Polyoxymethylene(POM)/multi-walled carbon nanotubes(MWCNT) composites were prepared by melt mixing MWCNTs and POM in a rotational rheometer.The morphology,conductive property,dynamic rheological property,thermal property and crystallization behavior of the composites were investigated.It was found that MWCNTs,without any modification,dispersed homogeneously in the POM matrix.The conductive percolation effect was observed when the MWCNTs content was 1 wt%,with the percolation threshold between 0.5 wt%～1.0 wt%.The thermal conductivity of POM/MWCNT composites increased to 0.5289 W/(K m) with the addition of 1.0 wt% MWCNTs,1.5 times higher than that of pure POM [0.198 W/(K m)].When the content of MWCNTs is further increased,the thermal conductivity of the composites hardly changed.The effective media approach(EMA) was used to confirm that the moderate increase of thermal conductivity was contributed to the interfacial resistance between MWCNTs and POM.MWCNTs have significant nucleating effect on POM,and 0.5 wt% MWCNTs could enhance the crystallization temperature of POM by about 6℃,but did not improve further with additional addition of MWCNTs.The complex viscosity,storage modulus and loss modulus of the composites increase with the content of MWCNTs.

PREPARATION AND MICROSTRUCTURE OF MCNT/Cu NANOCOMPOSITE

The fracture process and the structure changes of the multi-walled carbon nanotubes (MCNT) during the mechanical ball milling process were investigated and the samples of ball milled powder were observed by SEM. The results indicate that the MCNT turned into nano-whiskers or nano-particles during the ball milling process. The pre-milled MCNT could be distributed in Cu powders homogeneously. The bulk MCNT / Cu nanocomposite were fabricated by hot pressing the mixed MCNT / Cu powders at a temperature of 1073 K under a pressure of 20 MPa and the microstructure of the composites were investigated. It has been found that the multi-walled carbon nanotubes distributed in copper evenly.

The synergetic effect of carbon nanotubes and carbon black in a rubber system

Rubber/carbon composites were prepared by mixing multi-walled carbon nanotubes (MWCNTs), carbon black or a mixture of carbon black and MWCNTs with rubber by a laboratory two-roll mill. Results showed that MWCNTs could effectively improve elastic modulus, stress at a defined enlongation, abrasion resis￣tance and electrical properties compared to the carbon black additive. However, the tensile strength, tear strength, strain to failure, viscosity and processing properties of the MWCNT based composites were rather poor. The properties of the composites with both MWCNTs and carbon black added were improved effectively by the formation a grape-cluster-like reinforcing structure. When the weight ratio of MWCNTs to carbon black was 1∶4, the tear strength (78.4kN/m), hardness (68) and abrasion loss (0.112cm3/km) of the rubber/MWCNT-carbon black composite were better than those of the rubber/carbon black composite and the strain to failure (470%) and viscosity (65Pa·s) were better than those of the rubber/MWCNT composite. The rubber/MWCNT composites had excellent dynamic mechanical properties and could be used in tyres with low roll hysteresis and fatigue loss resistance.

Rheology of multiwall carbon nanotube suspensions

Carbon nanotubes have exhibited unusually large changes in selective physical and mechanical properties when added to polymers or polymer composites in small quantities. To understand their rheological behavior and processibility, we mixed multiwalled carbon nanotubes (MWNT) in epoxy and created suspensions of different dispersion qualities, MWNT aspect ratios, concentrations, suspension network structures, and MWNT orientation states. Their rheological properties were measured with a cone and plate rheometer. It was found that as MWNT dispersion quality improved or their network connections, the aspect ratio or concentration increased, the MWNTs interactions became stronger as indicated by a higher storage modulus G′, complex viscosity ∣η*∣, and steady shear viscosity η. It was found that suspensions which contained a mixture of separated MWNT along with small MWNT aggregates exhibited G′ that was independent of frequency suggesting solidlike behavior. This frequency sweep method could be used to characterize the network structure state for well dispersed nanotube suspensions. The steady shear viscosity η was found to be more sensitive to MWNT separation than G′ and ∣η*∣. All suspensions exhibited shear thinning behavior and nanotubes showed statistically significant alignment in the direction of the shear flow. Aligned MWNT suspensions not only displayed lower η than randomly orientated MWNT suspensions, but also had lower G′ and ∣η*∣ values. Transmission electron microscope (TEM) images of cured suspensions and a recently developed capillary method was used to validate the MWNTs suspension state and its microstructure.

Rheological and Structure Investigation of Melt Mixed Multi‐Walled Carbon Nanotube/PE Composites

AbstractIn this study a series of melt mixed multi‐walled carbon nanotube (MWNT)/Polyethylene composites with several carbon nanotube (CNTs) concentrations were investigated. A good dispersion of the nanotubes in the matrix was seen using scanning electron microscopy. Melt rheological measurements in dynamic mode were used to estimate the percolation state of the CNTs within the polymer and to provide information about the structure of the CNT/polymer composites. The effect of nanotubes on the non‐isothermal crystallization behaviour of the nanocomposites was also studied by differential scanning calorimetry.

Effect of carbon nanotube pre-treatment on dispersion and electrical properties of melt mixed multi-walled carbon nanotubes / poly(methyl methacrylate) composites

Multi-walled carbon nanotubes (MWNTs) pre-treated by concentrated mixed acid or oxidized at high temperature were melt mixed with poly(methyl methacrylate) (PMMA) using a twin screw extruder. The morphologies and electrical properties of the MWNT/PMMA composites were investigated. The thermally treated MWNTs (t-MWNTs) were well dispersed, whereas the acid treated MWNTs (a-MWNTs) were highly entangled, forming large-sized clusters. The resulting electrical properties of the composites were analyzed in terms of the carbon nanotube (CNT) dispersion. The experimental percolation threshold was estimated to be 3 wt% of t-MWNTs, but no percolation occurred at similar concentrations in the a-MWNT composites, due to the poor dispersion in the matrix.