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Abstract: Polyaniline-coated multi-walled carbon nanotubes were prepared by in situ chemical polymerization method for the novel sensing materials of ammonia gas. The thickness of the polyaniline coatings was controlled by the oxyfluorination treatment on the multi-walled carbon nanotubes. The oxyfluorination with higher oxygen content produced the more hydrophilic functional groups on the surface of multi-walled carbon nanotubes. Both the resistivity change and the response time were significantly improved with high repeatability using the more hydrophilic multi-walled carbon nanotubes which were modified with oxyfluorination. [Copyright &y& Elsevier]

Abstract: Activated multi-walled carbon nanotubes were prepared with appended vanadium as a hydrogen storage medium. The pore structure was significantly improved by an activation process that was studied using Raman spectroscopy, field emission transmission electron microscopy and pore analysis techniques. X-ray photoelectron spectroscopy and X-ray diffraction results reveal that the vanadium catalyst was introduced into the carbon nanotubes in controlled proportions, forming V8C7. The improved pore structure functioned as a path through the carbon nanotubes that encouraged hydrogen molecule adsorption, and the introduced vanadium catalyst led to high levels of hydrogen storage through the dissociation of hydrogen molecules via the spill-over phenomenon. The hydrogen storage behavior was investigated by electrical resistance measurements for the hydrogen adsorbed on a prepared sample. The proposed mechanism of hydrogen storage suggests that the vanadium catalyst increases not only the amount of hydrogen that is stored but also the speed at which it is stored. A hydrogen storage capacity of 2.26wt.% was achieved with the activation effects and the vanadium catalyst at 30°C and 10MPa. [Copyright &y& Elsevier]

Abstract: Glucose-sensing electrodes were constructed from carbon fibers by electrospinning and heat treatment. By controlling the pore size, the specific surface area and pore volume of the electrospun carbon fibers were increased for efficient immobilization of the glucose oxidase. Carbon nanotubes were embedded as an electrically conductive additive to improve the electrical property of the porous carbon fibers. In addition, the surface of the porous carbon fibers was modified with hydrophilic functional groups by direct oxyfluorination to increase the affinity between the hydrophobic carbon surface and the hydrophilic glucose oxidase molecules. The porosity of the carbon fibers was improved significantly with approximately 28- and 35-fold increases in the specific surface area and pore volume, respectively. The number of chemical bonds between carbon and oxygen were increased with higher oxygen content during oxyfluorination based on the X-ray photoelectron spectroscopy results. Glucose sensing was carried out by current voltagram and amperometric methods. A high-performance glucose sensor was obtained with high sensitivity and rapid response time as a result of carbon nanotube addition, physical activation and surface modification. The mechanism of the highly sensitive prepared glucose sensor was modeled by an enzyme kinetics study using the Michaelis–Menten equation. [Copyright &y& Elsevier]

Abstract: The electro-responsive transdermal drug delivery system was prepared by electrospinning of poly(vinyl alcohol)/poly(acrylic acid)/multi-walled carbon nanotubes (MWCNTs) nanocomposites. The surface modification of MWCNTs was carried out by oxyfluorination to introduce the functional groups on the hydrophobic MWCNTs. The dispersion of MWCNTs and the compatibility with polymer matrices were improved by oxyfluorination. The MWCNT content and oxyfluorination condition played important roles in the swelling and drug release characteristics of nanofibers. The conductivity of nanofibers increased by increasing the content of MWCNTs and performing oxyfluorination with higher oxygen content. Uniform distribution of the oxyfluorinated MWCNTs in the nanofibers was crucial to the electro-responsive swelling and drug releasing behaviors of nanofibers. [Copyright &y& Elsevier]

Abstract: A polyacrylonitrile/carbon nanotube (CNT) complex was fabricated for use as a gas sensor using an electrospinning method. The surfaces of the multi-walled carbon nanotubes (MWCNTs) were modified by using a fluorination treatment to provide sufficient dispersion within the electrospun fibers. The electrospun fibers were thermally treated to obtain carbon fibers and then chemically activated to increase the number of active sites for efficient gas adsorption. The activation process improved the porous structure by increasing the specific surface area by approximately 115-fold. The gas-sensing ability and response time improved by introducing both the porous structure and the fluorinated MWCNTs. High-performance gas sensing followed a proposed mechanism, which included the effects of the activation and the MWCNT additive. The pore structure that developed as a result of activation significantly increased the amount of adsorbed gas and produced the high sensitivity of the gas sensor, while the MWCNTs led to a quick sensor response time due to the efficient transfer of resistance changes occurring on the surface of the fibers. Overall, due to the effects of chemical activation and fluorinated MWCNT additives, the sensor''s sensitivity to NO gas improved by approximately 8 times, the response time decreased by approximately 60%. [Copyright &y& Elsevier]

Abstract: A high-performance NO gas sensor was prepared by inducing thermal fluorination of carbon nanotube semiconductors. Thermal fluorination of multi-walled carbon nanotubes (MWCNTs) was carried out at various temperatures (100∼1000°C) to investigate the effects of the reaction temperature. The mechanism of high-performance NO gas sensor electrode was shown to depend on the fluorination temperature in a way that can be divided into three regions, separated at 400 and 1000°C. In the first temperature region, the induction of fluorine functional groups onto MWCNTs showed the opposite trend in electrical resistance change comparing with traditional p-type MWCNTs. In the second temperature region, the induced fluorine functional groups were attenuated by generated fluorinated carbon gases resulting in the decomposition of MWCNTs and the recovery of traditional p-type gas sensor behavior. In the highest temperature region above 1000°C, reoriented carbon structure was observed, showing bent nanotubes produced from destruction by fluorination and subsequent reorientation due to the high temperature. The gas sensing responsiveness was significantly improved by the thermal fluorination, which causes electrophilic attraction, creates adsorption sites for target NO gases and improve hydrophobicity for gas sensing stability in humid condition. In conclusion, a high-performance gas sensor was obtained by thermal-fluorination of MWCNTs. [Copyright &y& Elsevier]

Abstract: Polyurethane fibers were fabricated using an electrospinning method with aluminum hydroxide and multi-walled carbon nanotubes (MWCNTs) as flame-retardant additives to improve the thermal oxidation stability of the polyurethane fibers. The MWCNTs were incorporated into the polyurethane fibers after oxyfluorination treatment to improve the dispersivity and compatability. The thermal properties and anti-oxidation stabilities of these polyurethane fibers were investigated under nitrogen and oxygen flows from room temperature to 600°C to determine the effects of the MWCNTs and aluminum hydroxide additives. The aluminum hydroxide acted as an energy storage tank by releasing water, resulting in an endothermic reaction. The MWCNTs promoted the formation of a charred layer that acted as a protective film to prevent the decomposition of the polyurethane by oxygen radicals. The flame-retardant properties were also improved by an enhanced gel-type structural network generated by the MWCNTs. The integral procedure decomposition temperature and activation energy increased significantly, indicating that the flame-retardant properties of the polyurethane fibers improved. These results are attributed to the aluminum hydroxide, MWCNT additives, and the oxyfluorination treatment. [Copyright &y& Elsevier]

Abstract: Thermal fluorination of multi-walled carbon nanotubes (MWCNTs) was performed to improve their hydrogen storage capacity, based on three considerations. First, the surface of the MWCNTs was altered by thermal fluorination to create a pathway for the storage of hydrogen molecules inside the MWCNTs. These surface treatments increased the number of MWCNT defects through attack by fluorine radicals. The defects were identified using Raman peaks and TEM images. Second, thermal fluorination changed the pore structure by enlarging the specific surface area and the pore volume, which increased the number of hydrogen adsorption sites. Last, the induced fluorine groups enhanced the hydrogen storage capacity through attraction effects on the electron in the hydrogen molecules due to the high electronegativity of fluorine. In conclusion, thermal fluorination increased the hydrogen storage capacity of MWCNTs four-fold to 1.69 wt%. [Copyright &y& Elsevier]

Abstract: Carbon fibers were prepared as an electromagnetic interference shielding material by electrospinning and heat treatment methods. To increase the electromagnetic shielding effectiveness, additives (Fe2O3/BaTiO3/multi-walled carbon nanotubes) were included due to their excellent dielectric and coercive force properties. The additives were observed to cluster on the surface of fibers; additive metal oxides did not show any structural changes during the heat treatment, retaining their original magnetic properties. The permittivity of the materials improved significantly as a result of the added carbon nanotubes and their high electrical conductivity. Magnetic properties such as saturated magnetization and coercive force were also improved by the presence of Fe2O3/BaTiO3, which enhanced the permeability. The improved permittivity and permeability significantly contributed to effective shielding of electromagnetic interference measured at 37dB. [Copyright &y& Elsevier]

Abstract: Flame retardant additives of montmorillonite (MMT) and multi-walled carbon nanotube (MWCNT) were embedded in epoxy resin to improve the resin''s flame retardant properties. MMT was fluorinated to exfoliate its layers and enhance its dispersion into the epoxy resin. The MWCNT was also fluorinated to create hydrophobic functional groups for improved dispersion into the epoxy resin. The MWCNT reduced the degradation rate of the epoxy resin and increased the char yield. Limiting oxygen index also increased showing first order against char yield. The exfoliated MMT acted as an energy storage medium to hinder thermal transfer within the epoxy resin. The activation energy increased almost two times by fluorinated MMT/MWCNT additives. The fluorination of the additives, MMT and MWCNT significantly improved the flame retardant properties of the epoxy resin. [Copyright &y& Elsevier]

Abstract: The pH and electro-responsive composite microcapsules were prepared by using multi-walled carbon nanotubes (MWCNTs), poly(vinyl alcohol), and poly(acrylic acid). MWCNTs were employed to improve the electro-responsive properties of microcapsules. The surface modification of MWCNTs was carried out by oxyfluorination for the improved dispersion in the microcapsule shell. The morphology of microcapsules and the location of MWCNTs in the microcapsule shell were investigated by SEM and TEM. The dispersion of MWCNTs in the microcapsule shell and the formation of composite microcapsules were improved by using the oxyfluorinated MWCNTs having the hydrophilic functional groups on the surface. The dual pH and electro-responsive release behavior of the composite microcapsules had a close relation with the uniform distribution of MWCNTs in the microcapsule shell. [ABSTRACT FROM AUTHOR]

Abstract: The application of an electric field was found to markedly increase the sensitivity of a gas sensor system. Multi-walled carbon nanotubes (MWCNTs) were used as a gas-sensing material in order to detect a target nitrogen monoxide (NO) gas. The response of the gas sensor was evaluated under both positive and negative electric fields at various applied voltages. The responsiveness of the gas sensor increased by a factor of 2.5 as a function of increasing positive electric fields because of the optimized electron acceptor–donor reaction between the NO gas and the MWCNTs. It was concluded that the applied electric field accelerated the electron transfer between the NO gas and the MWCNTs. [ABSTRACT FROM AUTHOR]

Abstract: Polyaniline-based fibers were fabricated with multi-walled carbon nanotubes and polyethylene oxide by the electrospinning method to be employed as an electromagnetic interference shielding material. To improve the electromagnetic interference shielding efficiency, the dispersion and adhesion of the carbon nanotubes in the polyaniline electrospun fibers were enhanced through surface modification by the direct fluorination method. This fluorination treatment enhanced the electron donor–acceptor reaction between the fibers and nanotubes, causing adhesive bonding for high electromagnetic interference shielding efficiency. The electrical conductivity improved with the addition of the carbon nanotubes and the fluorination treatment of the carbon nanotubes, reaching up to 4.8×103 S/m. The scanning electron microscope images showed well-oriented carbon nanotubes inside of the polyaniline fibers based on the effects of the fluorination. Investigating the electromagnetic interference shielding efficiency mechanism confirmed that absorption was the main reaction that shielded the electromagnetic interference. Eventually, an improved electromagnetic interference shielding efficiency of 42dB was obtained. [Copyright &y& Elsevier]

Abstract: Composite microcapsules of poly(vinyl alcohol)/poly(acrylic acid)/multi-walled carbon nanotubes were prepared and the electromagnetic interference shielding behavior was evaluated for the composite microcapsules. The dispersion and adhesion of multi-walled carbon nanotubes in microcapsules were improved by the surface modification through direct oxyfluorination which introduced polar groups on the multi-walled carbon nanotubes. The composite microcapsules containing the oxyfluorinated multi-walled carbon nanotubes showed significant increases in permittivity, permeability, and electromagnetic interference shielding efficiency. The electromagnetic interference shielding efficiency of composite microcapsule increased up to 51dB mainly base on the absorption mechanism. [Copyright &y& Elsevier]

Abstract: Multi-walled carbon nanotubes were embedded into e-beam-cured epoxy resin to improve the mechanical properties of epoxy resin. The surfaces of these carbon nanotubes were modified using a fluorination treatment to improve their dispersion and adhesion in epoxy resin. The dynamic mechanical properties of epoxy/carbon nanotube composites were investigated at various heating rates and frequencies. As an effect of fluorination treatment, the semi-ionic bond of C–F on the surface of multi-walled carbon nanotubes played an important role in the improved dispersion and adhesion of carbon nanotubes into the epoxy resin. The storage modulus and loss modulus of the composites increased with higher applied frequency. The activation energy of the composites was increased by the effects of a higher heating rate due to the slow heat transfer in the epoxy/carbon nanotube composites. Eventually, the dynamic mechanical properties of the investigated epoxy were significantly improved by the carbon nanotubes dispersed therein via the fluorination treatment. [Copyright &y& Elsevier]

Abstract: To improve the efficiency in shielding electromagnetic interference in electronic devices, multi-walled carbon nanotubes were used, due to their excellent electric and magnetic properties at high aspect ratios, and were added to an epoxy matrix. Fluorination was carried out to achieve excellent dispersion and adhesion of the additives in the epoxy matrix. The improved dispersion was confirmed by UV spectra. The permittivity and permeability were also significantly improved based on the effects of the additives and the fluorination treatment. The efficiency of shielding electromagnetic interference increased up to 28dB. This improved efficiency of shielding electromagnetic interference may be caused by a well-organized conductive network of additives in epoxy. [Copyright &y& Elsevier]

Abstract: Multi-walled carbon nanotubes (MWCNTs) were embedded into high-density polyethylene (HDPE) to improve the electrical properties of HDPE polymeric switches. The MWCNT surfaces were modified by oxyfluorination to improve their positive temperature coefficient (PTC) and negative temperature coefficient (NTC) behaviors in HDPE polymeric switches. HDPE polymeric switches exhibit poor electron mobility between MWCNT particles when the number of oxygen functional groups is increased by oxyfluorination. Thus, the PTC intensity of HDPE polymeric switches was increased by the destruction of the electrical conductivity network. The oxyfluorination of MWCNTs also leads to weak NTC behavior in the MWCNT-filled HDPE polymeric switches. This result is attributed to the reduction of the mutual attraction between the MWCNT particles at the melting temperature of HDPE, which results from a decrease in the surface free energy of the C–F bond in MWCNT particles. [Copyright &y& Elsevier]