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Presents a study which bserved the preparation and electrical properties of bromine intercalated vapor-grown carbon fibers. Details on the experiment; Results of the study; Conclusions.

Carbon fibers are state-of-the-art materials with properties that include being light weight, high strength, and chemically stable, and are applied in various fields including aeronautical science and space science. Investigation of applications of carbon fibers to biomaterials was started 30 or more years ago, and various products have been developed. Because the latest technological progress has realized nano-level control of carbon fibers, applications to biomaterials have also progressed to the age of nano-size. Carbon fibers with diameters in the nano-scale (carbon nanofibers) dramatically improve the functions of conventional biomaterials and make the development of new composite materials possible. Carbon nanofibers also open possibilities for new applications in regenerative medicine and cancer treatment. The first three-dimensional constructions with carbon nanofibers have been realized, and it has been found that the materials could be used as excellent scaffolding for bone tissue regeneration. In this critical review, we summarize the history of carbon fiber application to the biomaterials and describe future perspectives in the new age of nano-level control of carbon fibers (122 references). [ABSTRACT FROM AUTHOR]

Rheological and mechanical properties of polypropylene filled with dilute Vapor-Grown Carbon Fibers (VGCF) were examined. VGCF were premixed with polypropylene by a mix and beat machine and the mixture was subsequently compounded by a screw extruder. The viscosity of the composites containing less than 7.5% VGCF concentration, measured by capillary rheometry, decreases compared with that of the raw resin in wide ranges of both shear rate and resin temperature. The tensile strength of the 0.1% VGCF composites increases 8.5% and the Young's modulus increases 11.4% while keeping the essential elongation property of polypropylene. [ABSTRACT FROM AUTHOR]

To obtain a new electroconductive composite, the vapor-grown carbon fiber (VGCF) has been applied to the thermoplastic resin composite as a conductive filler. The stability of electrical conductivity of the composite is investigated. The resistivity of VGCF composite is 1.7 x 10-1 ω-cm at room temperature which is one order smaller than that of commercial grade composites with carbon filler. The stability of electrical conductivity, under temperature change (-35 to +60°C) and for exposure tests (at room temperature and at 60°C), the VGCF composites have high degree of stability. The stability of electrical conductivity of the present composites are superior to those of conventional carbon fibers such as PAN-based, under tensile stresses and bending stresses. It is suggested that the fine conductive networks in the present composites give rise to these desirable performances. [ABSTRACT FROM AUTHOR]

In this study, using high-crystallinity VGGF as the virgin graphite, the second-stage type (C2F)n fibers were formed and their structures were analyzed by X-ray diffraction and SEM. To obtain a primary lithium battery with high potential, its application to an anode activator was investigated. Thus the potential of the resulting battery was found to be 0.3 V higher than that of a conventional lithium battery. In addition, the flatness of the discharge potential was excellent. This paper will compare this new type of battery and the conventional (CF)n Li primary battery. [ABSTRACT FROM AUTHOR]

A method to observe the dispersion structure of carbon nanotubes buried inside a molding composite is described in this communication. The idea is that by utilizing the difference in ablation temperature between the tubes and the composite material, only the composite material, which has a lower ablation temperature, is ablated and buried tubes appear. This was applied to a rubber composite mixed with vapor-grown carbon fibers. A 150-fs pulse laser was prepared as an ablation source. In the ablation images observed with a field-emission secondary electron microscope, linear tubes, clusters, and connections of the tubes could be easily found in their original state. [ABSTRACT FROM AUTHOR]

[Display omitted] • The effects of heat treatment on the electrical transport properties of polyacrylonitrile-based carbon fibers. • The structural transition affects the temperature dependence of the electrical resistance and the magnetoresistance. • A peculiar metallic transport behavior due to the band overlaps. The effects of heat treatment temperatures from 1000 to 2700 °C on the structural, chemical, and mechanical properties of polyacrylonitrile-based carbon fibers (CFs) were investigated. Structural changes affected mechanical properties, and in particular, a higher sp 3 content induced a higher tensile strength below 1600 °C. For a comprehensive study on the heat treatment effect and the mechanism for developing high-strength CFs, electrical transport properties were measured for the CFs. The transport behaviors in temperature-dependent conductivity and magnetoresistance were also significantly modified, which led to crossover from strong localization to weak localization due to sp2 carbon ordering. Interestingly, in samples that were subjected to intermediate heat treatment temperatures ranging from 1100 to 1600 °C, anomalous metallic temperature-dependent behavior was observed at low temperatures of below 40 K. This unusual charge transport was analyzed further with a pertinent heterogeneous model employing three-dimensional variable range hopping, weak localization, and linear metallic transport. The results suggest that mixed noncrystalline and crystalline structures with sp2/sp3 carbons, oxygen, and quaternary N groups in CFs enabled the transition behavior at such low temperatures. [ABSTRACT FROM AUTHOR]

We present a systematic and simple approach to produce high-strength carbon nanotube fibers (CNTFs) with electrical conductivity in the high performance range (>1000 S/cm). We studied several critical parameters to improve the mechanical properties of CNTFs by aryl cross-linking reaction. Both the molecular dynamics (MD) simulations and experimental results showed that the mechanical properties strongly depended on the degree of cross-linking, length of cross-linkers, and CNT diameter. The monobenzene (MB) covalent bonding between CNTF with double-walled CNTs (DWCNTs) showed the highest load transfer, resulting in significantly enhanced specific tensile strength (3.7 N/tex) and Young's modulus (210 N/tex) which are superior to the strongest commercial carbon fiber (3.6 N/tex and 180 N/tex), respectively. Furthermore, the mechanical properties of aryl cross-linked CNTF exhibited no significant change in strength with sample size of CNTFs, showing uniformity of strength with increasing degree of cross-linking. The electrical conductivity of the MB cross-linked CNTFs was ∼1400 S/cm, which is higher than the best value of commercial carbon fibers (715 S/cm). These results demonstrate that aromatic linker between CNTFs can significantly enhance mechanical properties without significant loss of electrical conductivity. These molecular engineering with MD simulations provide an important route to design and develop ultra-high-performance fibers. [ABSTRACT FROM AUTHOR]

Abstract: Effect of conductive additives and surface modification with NF3 and ClF3 on the charge/discharge behavior of Li4/3Ti5/3O4 (≈4.6μm) was investigated using vapor grown carbon fiber (VGCF) and acetylene black (AB). VGCF and mixtures of VGCF and AB increased charge capacities of original Li4/3Ti5/3O4 and those fluorinated with NF3 by improving the electric contact between Li4/3Ti5/3O4 particles and nickel current collector. Surface fluorination increased meso-pore with diameter of 2nm and surface area of Li4/3Ti5/3O4, which led to the increase in first charge capacities of Li4/3Ti5/3O4 samples fluorinated by NF3 at high current densities of 300 and 600mAg−1. The result shows that NF3 is the better fluorinating agent for Li4/3Ti5/3O4 than ClF3. [Copyright &y& Elsevier]

Abstract: Effect of surface fluorination and conductive additives on the charge/discharge behavior of lithium titanate (Li4/3Ti5/3O4) has been investigated using F2 gas and vapor grown carbon fiber (VGCF). Surface fluorination of Li4/3Ti5/3O4 was made using F2 gas (3×104 Pa) at 25–150°C for 2min. Charge capacities of Li4/3Ti5/3O4 samples fluorinated at 70°C and 100°C were larger than those for original sample at high current densities of 300 and 600mA/g. Optimum fluorination temperatures of Li4/3Ti5/3O4 were 70°C and 100°C. Fibrous VGCF with a large surface area (17.7m2/g) increased the utilization of available capacity of Li4/3Ti5/3O4 probably because it provided the better electrical contact than acetylene black (AB) between Li4/3Ti5/3O4 particles and nickel current collector. [Copyright &y& Elsevier]

Pyrene crystals were grown on carbon nanofibers (CNFs) by dispersing pyrene polycrystals and CNFs in water during ultrasonic irradiation, and they were characterized by scanning electron microscopy, X-ray diffractometry (XRD) and spectroscopy. The XRD measurements indicated that the orientation and size of the pyrene crystals on the CNF aggregates were different from that of the added pyrene polycrystals. Based on the spectroscopic properties of the pyrene crystals on the CNFs, the pyrene crystals on the CNF aggregates and on the individual CNFs were determined to be polycrystals and single crystals, respectively. These results indicate that pyrene crystals are produced on the CNFs by recrystallization of the added pyrene polycrystals and their crystal states depend on the aggregation state of the CNFs. [Copyright &y& Elsevier]

Abstract: Interlaminar fracture toughness for mode I and II deformation were investigated for carbon fiber (CF)/epoxy laminates toughened by a carbon nanofiber/epoxy interlayer. Vapor grown carbon fiber (VGCF) and vapor grown carbon nanofiber (VGNF) were chosen as the reinforcement for the interlayer. To illustrate the effect of the interlayer on the fracture toughness of the laminates, several types of carbon fiber reinforced plastics/carbon nanofiber (CFRP/CNF) hybrid laminates were fabricated. Each laminate was composed of unidirectional carbon/epoxy prepregs with carbon nanofiber varying the interlayer thickness. Mode I interlaminar fracture toughness was evaluated by a standard double cantilever beam (DCB) test. Mode II interlaminar fracture toughness was evaluated by an end notched flexure (ENF) test using a three point bending test. The experimental results of the DCB test confirms that the mode I interlaminar fracture toughness for hybrid laminates is about 50% greater than the base CFRP laminates. Furthermore, the results of the mode II fracture toughness test confirms that the interlaminar fracture toughness for hybrid laminates is 2–3 times greater than base CFRP laminates. In addition, the results revealed the recommended range of CNF interlayer thickness is between 100 and 150μm (approximately 20g/m2 carbon nanofiber area density). The difference in the effect of the interlayer fracture properties under mode I and II deformation was discussed on the basis of fractographic observations derived from scanning electric microscope. [Copyright &y& Elsevier]

Abstract: The effect of the dispersion, ozone treatment and concentration of cup-stacked carbon nanotubes on mechanical, electrical and thermal properties of the epoxy/CSCNT nanocomposites were investigated. Ozone treatment of carbon fibers was found to increase the surface oxygen concentration, thereby causing the contact angle between water, epoxy resin and carbon fiber to be decreased. Thus, the tensile strength, modulus and the coefficient friction of carbon fiber reinforced epoxy resin were improved. Moreover, the dispersion of fibers in polymer was increased and the electrical resistivity was decreased with the addition of filler content. The dynamic mechanical behavior of the nanocomposite sheets was studied. The storage modulus of the polymer was increased by the incorporation of CSCNTs. But the glass transition temperature decreased with increasing fiber loading for the ozone treated fiber composites. The ozone treatment did affect the morphology, mechanical and physical properties of the CSCNT. [Copyright &y& Elsevier]

1-Naphthol has been used as an in situ fluorescent probe to characterize the surface physicochemical properties of carbon nanofibers (CNFs). The fluorescence of 1-naphthol adsorbed on untreated CNFs originates from the 1Lb state and its peaks are shifted by the polarity of the surrounding media, indicating that there is a relatively non-polar area on the CNF surface. 1-Naphthol interacting with oxidized sites on the surface of nitric acid-treated CNFs exhibited an ion-pair fluorescence. This shows that there are some functional groups, interacting with 1-naphthol, on the treated CNF surface. The surface physicochemical properties of the CNFs can be characterized by this fluorescent probe. [Copyright &y& Elsevier]

Activated carbon fibers (ACFs), composed of nanometer-size fragments of graphite (nanographites), show π-electron-based paramagnetism. Measurements of ESR and magnetic susceptibility revealed that adsorption of water molecules drastically suppresses the paramagnetism of ACFs. Considering also the structural change, this is interpreted in terms of a crossover from a paramagnetic state to a low-spin state of each nanographite due to a structural change of nanographite-network caused by internal pressure of adsorbed water molecules. This phenomenon serves us as a new method for in situ controlling of the condensed state of electrons in soft materials. [Copyright &y& Elsevier]