Chemically grafting carbon nanotubes onto carbon fibers by poly(acryloyl chloride) for enhancing interfacial strength in carbon fiber/unsaturated polyester composites

We propose a novel method to uniformly graft high density carbon nanotubes (CNTs) onto carbon fiber (CF) using poly (acryloyl chloride) (PACl) as coupling agents. Compared to micromolecule couping agent previously reported in literature [2,3], PACl can supply much more active groups, which is beneficial for grafting high density CNTs onto CF surface. Moreover, in order to further increase the grafting density of CNTs, the solvothermal strategy was used for improving the reactive activity between CF and CNTs. After CNTs grafting treatment, there are still substantial amounts of reactive groups which can further react with various types of molecules to meet different requirements. In order to create chemical bonding between CF and unsaturated polyester (UP), CF-CNT was further grafted with undecylenic alcohol (UA) to get CF-CNT-UA hierarchical reinforcement. The interfacial adhesion of the resulting composites showed a dramatic improvement.     

Improved interfacial properties of carbon fiber/epoxy composites through graphene oxide-assisted deposition of carbon nanotubes on carbon fiber surface

A useful reinforcement for carbon fiber (CF) composites was found by performing the assisted electrophoretic deposition (EPD) of graphene oxide (GO) for carbon nanotubes (CNTs) onto the CF surface. GO-assisted EPD of CNTs was conducted without the use any other pre-treatment or additives in order to avoid destroying the structure of the CNTs and to facilitate preparation of stable dispersion that was suitable for EPD. The presence of GO-CNTs may effectively increase both the roughness and wettability of the CF surface, resulting in an improvement to the interfacial bonding strength between the CF and the epoxy (EP). In contrast to the pristine CF/EP composite, the GO-CNTs/CF/EP composite exhibited a 64.6 % increase in interlaminar shear strength. Meanwhile, the water absorption of the composites decreased from 0.36 wt.% to 0.14 wt.%. The variable surface morphology, surface roughness, surface free energy and surface chemical composition of the CF were considered to have had an effect on the interfacial properties of the CF/EP composites; these effects could be seen using atomic force microscopes, scanning electron microscopes, X-ray photoelectron microscopes and contact angle analysis characterizations.     

Effect of high temperature treatment on electrochemical properties of activated carbon fabric in supercapacitor application

In this study, viscose rayon-based activated fabrics were used as the electrodes of supercapacitors. First, viscose rayon knitted fabrics underwent oxidation, carbonization and activation in a semi-open high-temperature erect furnace to produce activated carbon fabrics (ACFs). They were then treated at temperatures up to 1500 °C for one hour. Electrochemical properties of ACFs were investigated by cycle voltammetry and electrochemical impedance spectroscopy. The ACFs after high temperature treatment has improved conductivity and substantially increased mesopore ratio, yielding higher capacitor retention in rapid charging-discharging processes. It is shown that the ACFs treated at 1500 °C had the highest mesopore ratio of 83 %, specific surface area of 1254 m²/g and average pore diameter of 20.9 Å, resulting in lower resistance of 0.2 Ω-cm. In addition, this ACFs electrode showed the highest capacitance retention of 49 % at high charging speed of 250 mV/s.     

Directly-prelithiated carbon nanotube film for high-performance flexible lithium-ion battery electrodes

Carbon nanotube (CNT) films are very flexible and serve as active materials for lithium-ion batteries (LIBs). Hence, they have high potential as flexible free-standing electrodes for wearable batteries. However, nanocarbon materials such as CNTs and graphene are of limited use as electrodes because they have a large initial irreversible capacity due to the formation of a solid electrolyte interphase (SEI). Herein, we prelithiated the CNT films to make them available as electrodes for flexible batteries by reducing their irreversible capacity. The SEI is pre-formed through a direct prelithiation (DP) method that brings lithium metal into direct contact with CNT films in an electrolyte. As a result, the capacity of directly-prelithiated CNT film electrodes continues to increase to 1520 mAh/g until 350th cycle of charge/discharge and their initial irreversible capacity vanishes. The changes in the electrochemical properties of CNT film electrodes by DP treatment and their flexibility are investigated.     

Perspective on Carbon Fiber Woven Fabric Electrodes for Structural Batteries

The purpose of this work is to explore effective means of fabricating nanostructure-deposited continuous woven carbon fabric and to investigate the feasibility of using this material in structural battery applications. In order to prove this concept, two types of nanostructured carbon fabric electrodes – one with vertically-aligned carbon nanotubes (VACNTs) formed directly on carbon fabric utilizing iron (Fe) nanoparticles and Al buffer layers, the other with the same VACNTs on a chemical vapor-deposited graphene surface utilizing Ni seed layers on the carbon fabric – were fabricated to investigate material electrical performances as battery electrodes. The reversible specific capacity of 250 mAh/g on average at C/20 with good cyclic retention in these three all-carbon electrodes, including pristine carbon fabric, suggests a promising structural battery electrode for low-current battery applications. Even though the capacity of VACNT-grafted carbon fabrics was limited due to poor wetting of the VACNT forest with electrolyte caused by the lack of functionalization of the VACNT, their excellent cyclic performances and galvanostatic curves support the idea that the carbon nanotube and carbon fabric combination can be utilized in battery applications. However, pristine-carbon fabric is still a good candidate for battery applications because of its simplicity of mass production.     

Preparation and characterization of porous carbon based nanocomposite for supercapacitor

Porous nanocomposites are prepared by electrospinning blended polyacrylonitrile, copper acetate and mutiwalled carbon nanotube in N, N-dimethylformamide. The electrospun nanofiber webs are oxidatively stabilized and then carbonized resulting in composite carbon nanofibers. The study reveals that composite nanofibers with relatively smooth surface morphology are successfully prepared. X-ray diffraction is used to confirm the presence of Cu in carbon nanofibers. The carbon nanofibers with CNTs have better thermal stability and higher electrical conductivity. The Brunauer-Emmett-Teller analysis reveals that C/Cu/CNTs nanocomposites with mesopores possess larger specific surface area and narrower pore size distribution than that of C/Cu nanofibers. The electrochemical properties are investigated by cyclic voltammetry and galvanostatic charge-discharge tests. The nanocomposite with 0.5 wt.% CNT loading exhibits an energy density of 2 Whkg^?1, power density of 1916 Wkg^?1, a specific capacitance of about 225 Fg^?1 at a current density of 2 Ag^?1 and its capacitance decreased to 78 % of its initial value after 3,000 cycles.     

Hybrid multi-scale basalt fiber-epoxy composite laminate reinforced with Electrospun polyurethane nanofibers containing carbon nanotubes

In this study, we report the fabrication and evaluation of a hybrid multi-scale basalt fiber/epoxy composite laminate reinforced with layers of electrospun carbon nanotube/polyurethane (CNT/PU) nanofibers. Electrospun polyurethane mats containing 1, 3 and 5 wt% carbon nanotubes (CNTs) were interleaved between layers of basalt fibers laminated with epoxy through vacuum-assisted resin transfer molding (VARTM) process. The strength and stiffness of composites for each configuration were tested by tensile and flexural tests, and SEM analysis was conducted to observe the morphology of the composites. The results showed increase in tensile strength (4–13 %) and tensile modulus (6–20 %), and also increase in flexural strength (6.5–17.3 %) and stiffness of the hybrid composites with the increase of CNT content in PU nanofibers. The use of surfactant to disperse CNTs in the electrospun PU reinforcement resulted to the highest increase in both tensile and flexural properties, which is attributed to the homogeneous dispersion of CNTs in the PU nanofibers and the high surface area of the nanofibers themselves. Here, the use of multi-scale reinforcement fillers with good and homogeneous dispersion for epoxy-based laminates showed increased mechanical performance of the hybrid composite laminates.     

Polyvinylpyrrolidone/Carbon Nanotube/Cotton Functional Nanocomposite: Preparation and Characterization of Properties

In the last decade, preparation of multifunctional composites have attracted researchers around the World for multi-purpose application. In this regard, we produced polyvinylpyrrolidone/carbon nanotubes/cotton (PVP/CNTs/cotton) nanocomposite by coating cotton fabric via pad-dry-cure under UV irradiation. Several characterization methods were used to investigate the functionality and durability including scanning electron microscopy, thermo-gravimetric analysis, flammability test, reflectance spectroscopy, tensile strength test, water absorption and antibacterial analysis. The interactions among PVP molecular chains, CNT particles and cellulose were confirmed by Raman spectroscopy. We observed a uniform coating of PVP/CNTs on the fiber surface. An advantage of our developed method was the strong interfacial interaction among compositions, high durability along with multifunctional properties. PVP/CNT nanocomposite was able not only to improve the thermal stability of cotton, but also provided a reduced flammability and good antibacterial properties. Here, we confirm a simple and versatile method for fabrication of PVP/CNTs/cellulose nanocomposite for multi-purpose applications.     

Scalable preparation of multiscale carbon nanotube/glass fiber reinforcements and their application in polymer composites

The introduction of carbon nanotubes (CNTs) into conventional fiber to construct a hierarchical structure in polymer composites has attracted great interest owing to their merits of performance improvement and multiple functionalities. However, there is a challenge for realizing the scalable preparation of the multi-scale CNT-glass fiber (CNTGF) reinforcements in practical application. In this work, we present a simple and continuous method of the mass production of multiscale CNT-glass fiber (CNT-GF) reinforcements. Scanning electron microscopy and thermo gravimetric analysis indicated ~1.0 wt% CNTs were highly dispersed on the whole fiber surface through a facile surfactant-assisted process. Such hybrid CNT-GF fillers were found to effectively enhance the stiffness, strength and impact resistance of polypropylene polymer. Increased storage modulus, glass transition temperature and crystallization temperature of the composites filled with the CNT-GF fillers were also observed in the differential scanning calorimetry and dynamic mechanical analysis compared with the composites containing the pristine GF fillers. Fracture surface analysis revealed enhanced interfacial quality between CNT-GF and matrix, which is likely responsible for improved performance of the hierarchical polymer composites.     

Mechanical enhancement of UHMWPE fibers by coating with carbon nanoparticles

Fiber-reinforced plastic (FRP) is composed of reinforced fibers and matrix resin, and has high specific strength and low-density materials. Because of the orientation of the fibers within them, FRPs are prone to buckling damage when under compression along the axial direction of the fiber, especially flexible organic ones. The compressive performance of FRP is largely dependent on fiber properties. the buckling load of FRP will increase with the increasing of fiber’s. In this study, we developed a way to improve the compressive and bending strength of ultra-high molecular weight polyethylene (UHMWPE) fibers. Carbon nanotubes (CNTs) and vapor-grown carbon fibers (VGCFs) were coated on the surface of UHMWPE fibers by pyrrole vapor deposition. The transverse compressive strength and bending strength of single UHMWPE fibers were determined by microcompression and single fiber bending measurements, respectively. The experiment result showed that coating UHMWPE fibers with CNTs and VGCFs increased both their transverse compressive strength and bending strength. It is excepted that the improved fiber would applied in FRP for better compressive performance.     

Preparation and properties of alkaline functionalized carbon nanotubes reinforced polyurethane composites

Composites consisting of polyurethane (PU)/carbon nanotubes (CNTs) have been successfully prepared by solution mixing method. CNTs were modified through mechano-chemical reaction to increase the compatibility with PU via hydrogen bondings. SEM microphotographs proved that modified CNTs (M-CNTs) became shorter and FTIR spectra showed that hydroxyl groups had been introduced to the surface of M-CNTs. SEM images of PU/M-CNTs composites also proved that M-CNTs were effectively dispersed in PU matrix. Mechanical property tests showed that addition of M-CNTs could significantly improve the tensile properties of PU/M-CNTs composite (breaking strength enhancement ratio for composite with 5.0 wt% M-CNTs was 103.81 %). The thermal stability of composites with M-CNTs was also improved. The initial degradation temperature enhancement was 19.9 oC for the composite with 0.5 wt% M-CNTs. Electrical property tests showed that the electrical properties were improved by adding M-CNTs. The volume conductivities increased 3 and 5 orders of magnitude for the composites with 5.0 wt% and 10 wt% M-CNTs, respectively. The addition of M-CNTs had little effect on the elastic properties of the composites.     

Effects of carbon nanotubes on morphological structure, thermal and flammability properties of electrospun composite fibers consisting of lauric acid and polyamide 6 as thermal energy storage materials

The ultrafine composite fibers consisting of lauric acid (LA) and polyamide 6 (PA6) as form-stable phase change materials (PCMs), were prepared successfully by electrospinning. The effect of carbon nanotubes (CNTs) on the structural morphology, phase change behaviors, thermal stability, flammability and thermal conductivity properties of electrospun LA/PA6 composite fibers was investigated by field-emission scanning electron microscopy (FE-SEM), differential scanning calorimetry (DSC), thermogravimetric analyses (TGA), microscale combustion calorimeter (MCC) and melting/freezing times measurements, respectively. SEM observations indicated that the LA/PA6 and LA/PA6/CNTs composite fibers possessed flat and ribbon-shaped morphologies, but the neat PA6 fibers had cylindrical shape with smooth surface; and the average fiber diameters for LA/PA6 composite fibers decreased generally with the addition of CNTs. DSC measurements indicated that the heat enthalpies of the composite fibers were lower that that of neat LA powders, while the amounts of CNTs had no appreciable effect on the phase change temperatures and heat enthalpies of the composite fibers. TGA results showed that the addition of CNTs increased the onset thermal degradation temperature, maximum weight loss temperature and charred residue at 700 °C of the composite fibers, attributed to the improved thermal stability properties. It could be found from MCC tests that there were two-step combustion processes for composite fibers, and corresponded respectively to combustion of LA and polymer chains (PA6) in composite fibers. The addition of CNTs reduced the peak of heat release rate (PHRR) of electrospun composite fibers, contributing to the decreased flammability properties. The improved thermal conductivity performances of LA/PA6/CNTs composite fibers was also confirmed by comparing the melting/freezing times of LA/PA6 composite fibers with that of neat LA powders. The results from the SEM observation showed that the composite fibers had no appreciable variations in shape and diameter after heating/cooling processes.     

Synthesis of electrospun carbon nanofiber/WO<Subscript>3</Subscript> supported Pt,Pt/Pd and Pt/Ru catalysts for fuel cells

In the present study, nano-sized Pt/WO₃-carbon nanofiber, Pt-Pd/WO₃-carbon nanofiber and Pt-Ru/WO₃-carbon nanofiber electrocatalysts were synthesized and the performance of prepared catalysts were compared with catalysts coated carbon black for the oxygen reduction reaction (ORR). The morphology and structure of prepared catalysts were characterized using scanning electron microscopy (SEM) and X-ray diffraction (XRD) analysis. The SEM images showed that the catalyst nanoparticles were well dispersed on the both carbon nanofiber and carbon black supports. Electrochemical measurements including linear sweep voltammetry (LSV), electrochemical impedance spectroscopy (EIS) and chronoamperometry (CA) tests were applied to investigate the potential of the fabricated electrodes on the ORR. The results demonstrated that the catalysts based on carbon nanofibers showed a significant increase of activity toward the ORR. Also, the Pt/Pd coated carbon nanofibrous electrode showed the highest electrochemical activity.     

Development and characterization of MWNTs/Chitosan biocomposite fiber

The Preparation of conductive biocomposite fiber through Carbon nanotubes (CNTs) incorporation into biopolymer matrixes has stimulated much interest for bio-implant applications. The present study focuses on development and characterization of biocomposite fiber composed of chitosan (CHT) as a biopolymer and multiwall carbon nanotubes (MWNTs) as a conductive filler. In term of processing, the most important challenge is to prepare a highly stable dispersion of MWNTs in biopolymer matrix. The hydrodynamic diameter distribution of CNTs in acetic acid solution acquired by dynamic light scattering (DLS).Results demonstrate the supreme stability of CNTs dispersion which is extremely essential for homogenous distribution of CNT in polymeric matrix. Rheological properties of the spinning solution have also been investigated to adjust the viscosity for fiber processing step. A range of viscosity between 2000–8000 cP, has been recorded in different CNT loading. The scanning electron microscopy (SEM) images of the surface and cross sectional area of the fibers reveal the formation of nano-pores after MWNT addition. The tensile strength show a maximum increase of about 33.65 % compared to bare CHT. Also, the measurement of four probe electrical conductivity for different MWNTs loading shows a maximum conductivity of 0.107 S/cm at percolation threshold of 2.89 wt%.     

Polycarbazole modified carbon fiber microelectrode: Surface characterization and dopamine sensor

Electropolymerization of carbazole (Cz) by cyclic voltammetry (CV) onto carbon fiber microelectrodes (CFME) (diameter ∼7 μm) in dichloromethane (CH₂Cl₂) solution of 0.1 mol·dm⁻³ tetraethyl ammonium perchlorate (TEAP) results in the formation of polycarbazole (PCz) thin film coatings. CV results showed that these PCz thin films have reversible redox behavior in monomer-free electrolyte solution. The resulting thin polymer films were characterized using Fourier transform infrared attenuated total reflectance spectroscopy (FTIR-ATR) and atomic force microscopy (AFM). Results performed at optimum experimental conditions indicate that electrodes show a reversible and stable behavior over sixty eight days of testing for dopamine in 100 μmol·dm⁻³ buffer solution. A detection limit for PCz thin films as low as 0.1 μM (3S/N) was obtained for the polycarbazole (PCz) thin films formed using CV. Hence, this novel sensor can be considered as promising sensor for dopamine detection.     

Composites of polyvinyl alcohol and carbon nanotubes decorated with silver nanoparticles

A simple method to decorate carbon nanotubes (CNTs) with silver nanoparticles was developed to enhance the electrical conductivity of CNTs. The acid-treated CNTs were suspended in the silver acetate solution, ammonia solution was then added, and the CNTs decorated with silver nanoparticles (Ag@CNTs) were produced. The Ag@CNTs were dispersed in polyvinyl alcohol (PVA) to fabricate electrically conducting polymer composites. The electrical, thermal and mechanical properties of the composites were measured. The electrical conductivity of the composites containing 0.8 % (o.w.f.) Ag@CNTs was more than four orders of magnitude higher than those of pristine and functionalized CNTs respectively, which confirmed the effectiveness of the Ag@CNTs as conducting filler. However, the improved electrical conductivity led to somewhat decrease of mechanical properties of PVA/Ag@CNTs composites.     

Performance of PTT fabric treated with CNTs/SiO<Subscript>2</Subscript>/thiazole dye hybrid materials

A series of CNTs/SiO₂/thiazole dye hybrid materials prepared via the sol-gel process is synthesized from carbon nanotubes (CNTs) and tetraethoxysilane with heteroaryl 4-phenyl-2-amino-thiazole dyes. Heterocyclic 4-phenyl-2-aminothiazole dyes are processed with the hydrolysis-condensation reaction at a constant ratio of vinyltriethoxysilane and tetraethoxysilane condensed with modified CNTs in appropriate proportion under a catalyst. The structures of the CNTs/SiO₂/thiazole dye hybrid materials are characterized by Fourier transform infrared spectroscopy (FTIR). Polytrimethylene terephthalate (PTT) fabrics are used to evaluate the morphology structure by scanning electron microscopy (SEM). SEM images show that a uniform dyeing on the PTT fabrics to confirm the reaction of hybrid materials with PTT fabrics. The washing fastness, color evenness, water contact angle, air permeability, electric conductivity, and weatherability of PTT fabrics dyed with CNTs/SiO₂/thiazole dye hybrid materials are evaluated, with results indicating improved conductivity and water-repellent.     

Efficacy research of electrocardiogram and heart rate measurement in accordance with the structure of the textile electrodes

Recently, the demand for 24-hour biological signal monitoring in various fields such as health care and sports is increasing rapidly because of lifestyle changes and increasing interests in health. Thus, the field of clothing for continuous monitoring of biological signals is again illuminated increasing the market. However, smart clothing used to monitor biological signals has disadvantages affecting the motion artifact which are due to movements of the human body, so studies for minimizing motion artifact is underway from various angles. In this research, we configured the structure of the textile electrodes can be applied inside of the clothing, of the flat type and the three-dimensional type, and tried to derive the electrocardiogram and the structure of the suitable structure to measure the heart rate through measuring and comparing the electrocardiogram signal and the heart rate accuracy by structure. For this process, the heart rate accuracy and electrocardiogram signals of 8 men, with a standard body shape in their twenties, were measured and analyzed when walking and standing. At this time, the subjects were wearing clothes in which three-dimensional electrodes and flat type electrodes could be applied, respectively, to measure the electrocardiogram signal and heart rate in accordance with the experimental protocol. The results of the stability of the waveform, the signal size and the SNR (Signal to Noise Ratio) of the threedimensional electrode when measuring the electrocardiogram signal were higher than those of the flat electrode. In addition, in the heart rate measured at the time when walking and standing, the accuracy of the three-dimensional electrode was shown to be higher than the flat type electrode, so the three-dimensional electrode was analyzed in a suitable structure for measuring the electrocardiogram and heart rate.     

Capacitive behaviors and monomer concentration effects of poly(9-benzyl-9<Emphasis Type="Italic">H</Emphasis>-carbazole) on carbon fiber microelectrode

In this work, 9-benzyl-9H-carbazole (BzCz) monomer was chemically synthesized by a new process. It was electrocoated on carbon fiber microelectrode (CFME) as an active electrode material in 0.1 M sodium perchlorate (NaClO₄)/acetonitrile (ACN) solution. The electropolymerization process was successfully performed less amount of 3 mM. The characterization of Poly(BzCz)/CFME thin films was performed by Fourier transform infrared reflectance-attenuated total reflection spectroscopy (FTIR-ATR) and Electrochemical impedance spectroscopy (EIS). The effects of monomer concentrations (1, 2, and 3 mM) during the preparation of modified electrodes were examined by EIS. Capacitive behaviors of modified CFMEs were defined via Nyquist, Bode-magnitude and Bode-phase plots. Variation of capacitance values by initial monomer concentration and specific capacitance values are presented. The highest specific capacitance value for a potensiodynamically prepared polymer thin film in the initial monomer concentration of 1 mM with a charge of 4.54 mC cm⁻² was obtained about 221.4 μF cm⁻². An equivalent circuit model, R(C(R(QR)))(CR), for different concentrations of Poly(BzCz). CFME was proposed and experimental data were simulated to obtain the numerical values of circuit components.     

Supramolecular composite of single-walled carbon nanotubes with oligo(p-phenyleneethynylene)s-graft-poly(ethyleneoxide)s

Poly(p-phenyleneethynylene)s, composed of a rigid backbone with alternating arylenes and ethynylenes, exhibit high conductivity and chemical stability, and thus they have huge potentials for various applications, including chemosensors, electronic and photonic devices. In spite of numerous interesting applications to date, not many researches concerning oligo(p-phenyleneethynylene)s-graft-poly(ethylene oxide)s (OPEs-g-PEOs) have been carried out, let alone their complexation behaviors with carbon nanomaterials. In this article, we present the synthesis of OPEs-g-PEOs and characterize its morphological and spectral properties by various characterization techniques. We have investigated the interaction of OPEs-g-PEOs with single-walled carbon nanotubes (SWNTs) using various characterization techniques, such as UV-visible, photoluminescence, and Raman spectroscopy, along with SEM, TEM, and POM. In this way, we have successfully demonstrated that OPEs-g-PEOs provide a useful means to modify the physical properties of CNTs, especially in terms of their solubility in common organic solvents.