This study aims to create controlled fine space by electrospinning, and to develop the electrode materials for high-performance energy devices. With the popularization of mobile devices, household appliances, hybrid vehicles, electric vehicles, and the like, the use of power storage devices is expanding, and further performance improvements are required. In this study, a novel electrode material was developed by compositing Si with carbon nanofibers derived from polyacrylonitrile (PAN) by electrospinning and heat treatment. The texture and structure of the nanofibers were observed and analyzed by scanning electron microscopy (SEM), energy dispersive X-ray spectrometry (EDX) and transmission electron microscopy (TEM) combined with image processing. Nano spaces were created in the CNFs and Si particles were able to be contained in the CNFs. In the second and subsequent cycles of the charge/discharge experiments of lithium ion battery (LIB) electrode made from the materials, the capacity was more than twice the theoretical capacity using graphite, and good cycle performance was obtained.

A digitization of the TEM pictures of fluorine-intercalated graphite fibers has been used to carry out quantitative measurements of the defect structure of this material. Emphasis is given to both the computer analysis technique and to the characterization of the defects. The amount of intercalation-induced disorder increases with increasing fluorine concentration. The fast Fourier transform of the digitized TEM image exhibits two diffuse spots, corresponding to the c-axis repeat distance of the intercalation compound. The length and width of the spots are a measure of the out-of-plane and in-plane disorder present in the fibers. From the fast Fourier transform, the distribution of interlayer repeat distances and the fraction of unintercalated graphite regions throughout the material is obtained. By selecting a small range of repeat distances and carrying out an inverse fast Fourier transform, the spatial distribution of material with a given repeat distance is determined. Regions with the same repeat distance are found to form islands. This particular feature of fluorine graphite intercalation compounds, as well as the nature of the microscopic defects and the staging behavior of fluorine-intercalated graphite fibers, are discussed in connection with the dual covalent and ionic nature of the carbon-fluorine bond in fluorine-intercalated graphite.

New structural features observed in heat-treated vapor-grown carbon fibers (VGCF’s), produced by the thermal decomposition of hydrocarbon vapor, are reported using image analysis of the lattice plane structure observed by transmission electron microscopy (TEM) and atomic force microscopy (AFM). The TEM lattice image of well-ordered graphite fibers (heat-treated VGCF’s at 2800 °C) was treated by a two-dimensional fast Fourier transform, showing sharp bright spots associated with the 002 and 100 lattice planes. The heat-treated VGCF’s consist of a polygonally shaped shell, and the long and short fringe structures in the TEM lattice image reflect the 002 and 100 lattice planes, respectively. From this analysis, new facts about the lattice structure are obtained visually and quantitatively. The 002 lattice planes remain and are highly parallel to each other along the fiber axis, maintaining a uniform interlayer spacing of 3.36 Å. The 100 lattice planes are observed to make several inclined angles with the 002 lattice planes relative to the plane normals, caused by the gliding of adjacent graphene layers. This work visually demonstrates coexistence of the graphitic stacking, as well as the gliding of the adjacent graphene layers, with a gliding angle of about 3–20°. These glide planes are one of the dominant stacking defects in heat-treated VGCF’s. On the other hand, turbostratic structural evidence was suggested by AFM observations. The structural model of coexisting graphitic, glide, and turbostratic structures is proposed as a transitional stage to perfect three-dimensional stacking in the graphitization process. These structural features could also occur in common carbons and in carbon nanotubes.

The present work presents a useful comparison of micropore size distributions (MPSDs) obtained from gas adsorption and image analysis of high-resolution transmission electron micrographs. It is shown that the MPSD obtained for a chemical activated carbon is concordant with that obtained from CO2 adsorption. In addition, this technique has allowed us to obtain the MPSD of a carbon molecular sieve (CMS) prepared in our laboratory by a copyrolysis process, which could only be characterized by CO2 adsorption at 273 K (not by N2 adsorption at 77 K due to diffusional problems). The MPSD obtained by high-resolution transmission electron microscopy (HRTEM) for the CMS is wider than that obtained by CO2 adsorption, suggesting that HRTEM is detecting the closed porosity existing in this sample, which is not accessible to gas adsorption. The existence of closed porosity in the CMS is explained considering the preparation method used. Thus, HRTEM combined with image analysis seems to be useful for structural analysis of narrow micropores including closed porosity.

The electrical resistivity and microstructure of nano-carbon materials, such as anisotropic coal tar pitch (pitch C) and polyparaphenylene (PPP), were investigated. The resistivity of the samples measured under applied pressure decreased as the packing density increased. The change ratio, ρ/PD (resistivity/packing density), for pitch C was larger than that for well-known petroleum pitch (Ashland 240), and the resistivity value of the former was about 30% smaller than that of the latter at the highest packing density. The difference in the resistivity under pressure is thought to be caused not only by the contact resistance of the grains but also by the difference in the domain structure of the two kinds of samples. The packing density of PPP, which is a disordered carbon material, is scarcely changed by applied pressure. The resistivity of PPP was found to be affected strongly by the heat treatment temperature.

Carbon nanotubes (CNTs) or carbon nanofibers (CNFs) are of great interest from both the fundamental and practical points of views. A particular effort is being directed toward their use in composite materials for a variety of applcations, including electrostatic discharge, structural reinforcement, and thermal dissipation. However, the research studies and applications of CNTs or CNFs have been hindered by the poor solubility and processibility of them. Recently, the dispersion of CNTs via covalent or noncovalent methods is considered an efficient method to overcome these difficulties. In particular, the dispersion of CNTs by noncovalent methods has shown useful for improving their solubility without impairing their physical properties. On the other hand, few studies have been reported on the dispersion of CNFs. Herein, we report on the dispersion of CNFs in water via noncovalent method.

In order to clarify the mechanism of Li-ions insertion/deinsertion into/from polyparaphenylene (PPP)-based carbons, the PPP carbonization has been analyzed. The weight loss of the PPP carbonized samples increased at a faster rate in the temperature range 600–680 °C. Hydrocarbons such as benzene and biphenyl were mainly detected by gas chromotography–mass spectrometry at a temperature of 710 °C during thermo-gravimetric analysis of PPP. The microtexture and the structure of heat treated PPP samples were characterized by high resolution transmission electron microscopy and investigated by image processing. The resistivity measurements of heat treated PPP showed a drastic decrease in the 680–730 °C HTT range. We related the microtexture evolution, the hydrocarbons release and the resistivity decrease of PPP carbonized samples to Li-ion battery capacity.

The evolution during carbonization treatments of a 100% anisotropic pitch (pitch C) was compared to that of Ashland 240 (100% γ resins). The anisotropic pitch C results from a gas-sparge preparation leading to a composition of 93% β resins (QS-TI) and 7% γ resins (QS). It is made of a major component (QS-TI), in which droplets (100–300 nm in size) partially toluene soluble are distributed. The physicochemical, textural and microtextural evolutions of the two pitches were studied. During pitch C primary carbonization, anisotropic droplets grow by coalescence, then decompose into Brooks and Taylor mesophase spheres suspended in isotropic drops. These drops develop at the expense of the anisotropic matrix by a continuous regeneration of the small anisotropic droplets which feed the isotropic drops by diffusion process. Then inside these drops, mesophase spheres grow then coalesce and the behaviour of a conventional pitch is restored. These various molecular associations are due to absence of chemical events below 450°C, leading to the global mass spectrum being constant. At 500°C the material is homogeneously anisotropic though plastic, the metastable system is destroyed and the evolution of conventional pitches is recovered, i.e. above 550°C macropores develop up to solidification at 600°C (semi-coke stage).

Cyclooxygenase-2 (COX-2) is one of the rate-limiting enzymes for prostaglandin synthesis from arachidonic acid. Although it is known that inhibition of cyclooxygenase activity delays ulcer healing, the regulatory relationship between COX-2 and its metabolites in gastric epithelial cell proliferation is not well known.To investigate whether COX-2 has an effect on gastric mucosal cell proliferation and further studied whether such effect is mediated only by prostaglandin E2 (PGE2), a representative metabolite of arachidonates in the gastric mucosa.Artificial wounds of defined area size were created on complete monolayer cell sheets of isolated rat gastric epithelial cells and rat gastric cell line RGM1 under the addition of arachidonic acid or a COX-2 selective inhibitor, JTE522. Repair of wounds was assessed by monitoring wound size, with cell proliferation detected using 5-bromodeoxyuridine staining. Quantity of secreted PGE2 was measured by enzyme immunoassay.Stimulation of foetal calf serum increased the expression of COX-2 protein and inhibition of COX-2 retarded wound healing with reduction of cell proliferation. Arachidonic acid increased PGE2 production and accelerated restoration. Combination of JTE522 and arachidonic acid resulted in a marked retardation of wound healing compared to the control, but JTE522 did not completely suppress the increase in cellular PGE2 content following the addition of arachidonate.The difference in the effects of JTE522 on PGE2 production and on wound healing suggest that the involvement of COX-2 in gastric epithelial cell proliferation is not mediated solely by PGE2.

Polyparaphenylene (PPP)-based carbon is expected for a high-performance material of a negative electrode of lithium (Li) ion secondary battery, but the details of relationship between characteristics and heat treatment have not been known. In this report, electrochemical and electrical properties of heat-treated PPP-based carbon powder were investigated and the possibility of the use as the negative electrode of Li ion secondary batteries was shown.

Straight long carbon nanofibers with a large hollow core obtained by a floating reactant method show a stacking morphology of truncated conical graphene layers, which in turn exhibit a large portion of open edges on the outer surface and also in the inner channels. Through a judicious choice of oxidation conditions, nanofibers with increased active edge sites are obtained without disrupting the fiber’s morphology. A graphitization process induces a morphological change from a tubular type to a reversing saw-toothed type and the formation of loops along the inner channel of the nanofibers, accompanied by a decrease in interlayer spacing.

A relation between the pore structure and the fracture resistance is examined on carbon fiber/pitch-based carbon matrix composites since pores are considered an important microspace component affecting the fracture behavior in the composites. A part of the pores may lie on a fiber surface so that the bonding force at the fiber/matrix interface is varied depending on the size and the spatial distributions of the pores. The change in the bonding force distribution brings a large-scale fiber pullout process into the composites. Therefore, the fracture resistance can be improved by controlling the microspace of the composites.

Carbon spheres with well-dispersed nickel particles were formed by the carbonization of chelate resin complexed with Ni(II) ions at 600 and 1000 degreesC, When the amounts of nickel after carbonization were less than 1 mass%, more than 90% of Ni species were paramagnetic or superparamagnetic, irrespective of carbonization temperature, indicating that they were dispersed as small clusters. For samples with 2.2-3.4 mass% Ni and formed at 600 degreesC, most of Ni species were ferromagnetic and their coercive force was less than 10 Oe at 280 K. The Ni metal particles in these samples were around 10 nm in size and well dispersed, but the number density of particles was not uniform in the samples of <1 mass% Ni. For samples with 3.4 mass% Ni and formed at 1000C, more than 80% of Ni species were ferromagnetic and the coercive force slightly increased to about 20 Oe. The results of XRD measurement and TEM observation showed that the Ni metal particles were around 10-30 nm and well dispersed in agreement with the magnetic properties. The results showed that the present method is promising to form the carbon materials containing well dispersed fine metal particles. (C) 2001 Elsevier Science B.V. All rights reserved.

The formation of graphite crystals from mixtures of different carbon precursors, poly(vinyl chloride) (PVC), poly(vinyl alcohol) (PVA) and poly(vinyl pyrrolidone) (PVP), with iron oxides Fe3O4 and Fe2O3, nickel oxide NiO, cobalt oxide Co3O4 and iron powder was studied at a temperature between 800 and 1200°C. The formation of flaky graphite crystals was confirmed from X-ray diffraction and transmission electron microscopy, and the reaction mechanism was studied by differential thermal analysis. From the powder mixtures of vinyl polymers, PVC, PVA and PVP, with Fe2O3, Fe3O4, Fe and Co3O4, graphite was obtained by the heat treatment at the temperature above 1000°C for 1 h, the higher temperature and the longer residence time giving the higher crystallinity of graphite. However, the mixture of NiO with PVA behaved a little different; well-developed turbostratic structure at 1000°C for 1 h and well-crystallized graphite at 1100°C for 24 h. The formation of graphite crystals was supposed to occur through the following steps; thermal decomposition and carbonization of vinyl polymers below 500°C, reduction of metal oxides to metal by carbonaceous products and then catalytic action of metals to precipitate graphite. Since carbons were consumed for the reduction of metal oxides, the mixing ratio of PVA to metal oxides suitable for the formation of graphite crystals was found to be related to the oxidation state of metals.

Transmission electron microscopy (TEM) is one of the most useful methods to clarify the structure in carbon materials. We developed quantitative analysis methods for the texture and structure of carbon materials containing the micro- and nano-spaces by using electron microscopy combined with image processing technique. The relations between phase transfer functions and TEM images of amorphous carbon films which consist of random arrangement of carbon layers were investigated using image processing. The similar patterns as the laser diffraction are obtained by the two-dimensional (2D) fast Fourier transform (FFT) of the digitized TEM images. The details of frequency distribution can be analyzed by integration around the central point of the power spectrum images. We applied this new technique to the study of microtexture and structure of graphite intercalation compounds (GICs). As a result of application of the frequency analysis using 2D FFT to the CuCl2-GIC, a characteristic power spectrum pattern called streak, which was similar to the electron diffraction pattern, was obtained. The images corresponding to the specific frequencies were reconstructed by 2D inverse FFT (IFFT). The stage structure of CuCl2-GICs was discussed by using this technique.

A new approach to study of micro texture and structure of graphite intercalation compounds (GICs) is shown using high resolution transmission electron microscopy (TEM) combined with image analysis and fuzzy reasoning. As a result of application of the frequency analysis using 2-dimensional (2D) fast Fourier transform (FFT) to the CuCl2-GICs, a characteristic power spectrum pattern called streak, which is similar to an electron diffraction pattern, is obtained. The images correspond to the specific frequencies are reconstructed by 2D inverse FFT (IFFT). Then the stage structure of CuCl2-GICs is investigated.

Graphite nanoparticles were prepared by the heat treatment of diamond nanoparticles in the range 900-1600 degreesC. X-ray diffraction, transmission electron microscopy (TEM) and Raman scattering studies indicate that the onset temperature of the diamond-graphite transition is around 1200 degreesC and the complete conversion of diamond to graphite occurs at 1600 degreesC. Based on the structural characteristics the samples are categorized into sp(3)-dominated (as-prepared and 900 degreesC), sp(2):sp(3) mixed-phase (1200 and 1400 degreesC), and sp(2)-dominated systems (1600 degreesC). The larger c-axis repeat distances and the high-resolution TEM images for the sp2:sp3 mixed-phase systems denote the presence of the remnant buckling feature of the diamond (111) planes in the graphene sheets. Magnetic susceptibility and ESR studies suggest the development of itinerant-pi -electron system from the 1200 degreesC and higher-temperature heat-treated samples. The completely graphitized sample reveals the important role of edge-inherited nonbonding pi -electron states in the electronic structure. The Raman G-peak position and the orbital diamagnetism show considerable deviation from the bulk-graphite values, which is explained on the basis of charge transfer from the gaphite pi band to the localized edge states and the resulting shifting of the Fermi level. The enhanced spin-lattice relaxation rates in the case of more graphitized samples heat-treated at 1400 and 1600 degreesC are expected to arise from the involvement of the localized edge-state electrons. In the less-graphitized 1200 degreesC heat-treated sample, however, the corrugated nature of the graphene planes is likely to hinder such fast-relaxation processes.