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Abstract: High crystalline carbon nanofibers were prepared by using polymer blend technique. Naphthalene-based mesophase pitch (AR pitch) was dispersed finely in polymethylpentene matrix, spun by using a melt-blown spinning machine, stabilized at 160°C in an oxygen atmosphere and carbonized at 900°C in a nitrogen atmosphere. Bundles of the carbon nanofibers with ca. 100nm in diameter were obtained after removal of polymethylpentene at the carbonization process. No impurity carbon was observed. The carbon nanofibers consisted of fine carbon crystallites with preferred orientation along the fiber axis. After heating to 3000°C, the carbon crystallites grew drastically to have an interlayer spacing of 0.3367nm and a crystallite thickness of 56.9nm, respectively, with remarkable improvement of the preferred orientation of the crystallites. Advantages and disadvantages of the present method were discussed briefly. [Copyright &y& Elsevier]

The polymer blend technique is proposed as a method for designing fine carbon materials. In principle a blend consisting of polymers with and without carbon residue after heating is subjected to melt-spinning, stabilization and finally carbonization. A combination of two polymers and control of the blend texture are important for using the technique successfully. In this paper, three prepared fine carbon materials are introduced, i.e. carbon fibers including thin and long pores aligned parallel to the fiber, thin carbon fibers 200–300 nm in diameter and carbon nanotubes with 10–20-nm outer diameter. In particular the carbon nanotubes are described in detail to emphasize the great potential of the polymer blend technique. Further possibilities of the technique are also discussed briefly. [Copyright &y& Elsevier]

A deodorant was prepared by drying charcoal particles after dipping in aqueous H3PO4 solutions. The deodorization performances of the samples against NH3 and (CH3)3N odor gases were examined by a detection test tube method and compared with those of a conventional coconut shell-derived active carbon loaded with H3PO4 in the same manner. The charcoal particles with H3PO4 exhibited higher performances than those of the other against both the odor gases. Ammonia gas was caught on the sample surface through reaction with the loaded H3PO4 to form NH4H2PO4 and further (NH4)2HPO4 but the deodorization mechanism for (CH3)3N could not be decided. The high performances of the charcoal particles loaded with H3PO4 were due to its characteristic porous structure consisting of large pores, i.e., such pores were suited for loading a large amount of H3PO4 and were not apt to be blocked by the loaded H3PO4. Also large pores were not blocked by expansion of H3PO4 on the pore surface through the deodorization reactions. The active carbon being composed of a large number of micropores did not exhibit these advantages. [ABSTRACT FROM AUTHOR]

Abstract: Single domain graphite fibers of 50–500nm in diameter were prepared from a mesophase pitch mixed with a matrix polymer to form a polymer alloy. The alloy was then spun, stabilized, carbonized, and graphitized at 2900°C. The carbonized fiber had a circular or Y-shaped cross-section, but all of the graphitized carbon nanofiber (CNF) changed into an elliptical cross-section with an aspect ratio (major axis/minor axis) of 2.47. The CNF consisted of well-developed graphite layers ordered throughout the cross-section, as observed in a single crystal and the layer edges formed loops consisting of 5–10 layers. [Copyright &y& Elsevier]

Bromanil (BA) doping of a naphthalene pitch, a kind of soluble carbonaceous material, enhanced the photoresponse of the junction between this material and a ρ-type silicon substrate by about tenfold. Morphological and spectroscopic studies revealed that the enhancement was partly caused by an increase in the surface roughness of the carbonaceous films, and by the enhanced dissociation of excitons in the carbonaceous films upon the BA doping. [ABSTRACT FROM AUTHOR]

Three carbon materials having unique and precise shapes were prepared using a polymer blend technique and coating as an auxiliary technique. The polymer blend consists essentially of two kinds of polymers, i.e. a carbon precursor polymer and a decomposable polymer which disappears by pyrolysis without leaving a carbon residue. One of the carbon materials prepared is a carbon fiber including many thin pores, with diameters of sub-μm to 1 μm, elongated along the fiber axis. The next is a carbon tube including a large amount of thin carbon fibers aligned densely along the tube surface. The last one is a microscopic multi-walled carbon tube consisting of three or four walls. The preparation procedures and SEM photographs of these materials are presented and possible applications are discussed briefly. [Copyright &y& Elsevier]

Abstract: B-, N- and BN-doped carbons were prepared by the carbonization of poly(furfuryl alcohol) containing either BF3–MeOH complex, melamine or both. Various characterization techniques were conducted in order to understand the controlling factors for the electrocatalytic activity of carbons for oxygen reduction reaction (ORR). Analytical inspections of the obtained XRD profiles, such as the Diamond and the Hirsch methods, revealed that the doping of boron and nitrogen broadened the graphene size distribution; while it did not influence the stacking manner of graphenes. All doped carbons showed reductions in electrical conductivity by the factors of a quarter to a hundredth of the pristine carbons. Development of porosity was observed for the doped carbons. B1s and N1s XPS analyses revealed the presences of B–C bonds and B–N–C moieties in the BN-doped carbons. The oxygen reductive activity, which was assessed by the ORR current density normalized by BET surface area, was increased by the factors of 4–5 for B-doped and N-doped carbons, while a factor of 20 was attained for the BN-doped carbons. The ORR activity of the prepared carbons was found to be controlled by the presence of both the edge-N and B–N–C moieties, which were distinguished by XPS. [Copyright &y& Elsevier]

Abstract: In this study, we prepared a type of arylacetylene, poly(p-phenylene butadiynylene), PPPB, and studied its pyrolysis behavior. A pellet of PPPB maintained its shape and provided a carbonization yield of 94% by heat-treatment at 1000°C, although it experienced exothermal reaction and partial fusion at approximately 200°C. It was also found that PPPB did not show graphitization even when it was heat-treated at 3000°C. X-ray diffraction (XRD) study revealed the breakdown of the initial crystal structure of PPPB at 200°C and a formation of the carbon structure at above 650°C. By combining the results of TG–MS, FT-IR, and 13C NMR, a mechanism for pyrolysis of PPPB including the cross-link formation was proposed, which included a Diels–Alder type reaction between the terminal acetylene and the diene structure comprising of diacetylene and phenyl groups, which is facilitated by increased mobility due to the partial fusion and the presence of the terminal acetylene groups. [Copyright &y& Elsevier]

Abstract: Influences of the pore structure and the surface functionality of carbon substrates on the formation of ZSM-5 nanoparticles were studied. The inorganic substance formed on these carbons were identified as ZSM-5 by X-ray diffraction, which also revealed the presence of an amorphous silica phase. The fraction of crystalline phase, which was evaluated from XRD, was not affected by the pore structure; however, inorganic content depended on the pore structure of carbon: i.e. 14–17% for non- and microporous carbons, and 40–55% for mesoporous carbons. TEM observation revealed that the ZSM-5 deposited on these carbon substrates was in the form of nanoparticles with 10–20nm of diameters. The influence of the surface functionality on the formation of ZSM-5 nanoparticles was also studied with an activated carbon, of which surface functionality was modified by heat-treatment and nitric acid-treatment. A strong dependence of the fraction of crystalline phase on the treatments was observed; i.e. the heat-treatment increased the fraction and the acid-treatment decreased it. Finally, we clarified the controlling factors for the formation of ZSM-5 on carbon materials; the mesoporous surface area of carbon strongly affects the inorganic content and the total acidity of carbon influences the selectivity to ZSM-5 formation. [Copyright &y& Elsevier]

The structure, physicochemical properties and oxygen reduction abilities of carbons prepared by the carbonization of mixtures of ferrocene and poly(furfuryl alcohol) were studied. X-ray diffraction (XRD), Raman spectroscopy and transmission electron microscopy (TEM) studies revealed that the carbons thus prepared consisted of two components; amorphous and turbostratic shell-like components. The fraction, f sharp, obtained by the analysis of the (002) peak in XRD was found to be a parameter that represented the degree of formation of the shell-like components. The formation of the shell-like components induced an increase in the mesopore volumes. Electrical conductivity increased exponentially with f sharp, which indicated that the conduction process was governed by a percolation process of the conductive shell-like components. The amount of CO-desorption by O2-TPD technique showed a maximum desorption at f sharp=0.3, and the further development in the sharp component led to a decrease in the CO-desorption. Mössbauer spectroscopy technique revealed the presence of α-Fe, γ-Fe, Fe1- x O and Fe3C in the prepared carbons, which were soluble species to acids. The oxygen reduction activity was studied in a oxygen saturated sulfuric acid solution by rotating disk electrode voltammetry. The oxygen reduction potential varied with f sharp; initially it increased by f sharp=0.3 and then it decreased at higher f sharp values. This behavior was similar to that of CO-desorption, which meant the presence of an adequate degree of the development of the shell-like structure for maximizing oxygen adsorption. Removal of the surface metal component from the carbons by acid-washing resulted in no decrease in the oxygen reduction activities of the carbons. The nature of the active sites on the carbon materials is discussed. [ABSTRACT FROM AUTHOR]

Abstract: Carbon nanotubes (CNTs) were synthesized from fine three-layered copolymer microspheres using the polymer blend technique. Diameter of PMMA core/Poly(AN-co-MMA) shell-1/PMMA shell-2 microspheres, prepared by a radical soap-free emulsion polymerization of methylmethacrylate (MMA) and acrylonitrile (AN), was between 400nm and 500nm. Microspheres were subjected to melt-spinning at 305°C, stabilizing in oxygen at 220°C for 4h, and finally carbonizing at 1000°C for 30min. FE-SEM study of carbonized sample revealed the presence of CNTs arrays on carbon blocks. Similar arrays were observed in a comparative CNTs sample prepared from three-layered microspheres with the pure PAN shells-1 layers. HRTEM showed that the CNTs derived from copolymer microspheres had different structure when compared to the control sample, i.e. CNTs often adhered to each other and contained the internal compartments. The insufficient PMMA shell-2 coating of copolymer microspheres is believed to be a reason for CNTs adhesion. The possible mechanisms of the carbon block formation and the adhesion of CNTs are introduced. [Copyright &y& Elsevier]

Porous carbon having more than 2000 m2/g of BET specific surface area was synthesized by defluorination of polytetrafluoroethylene (PTFE) at 473 K using sodium metal. The porous carbon as-prepared had a large amount of narrow mesopores 2–3 nm in pore width, together with micropores. Control of the pore structure was attempted by simple heat-treatment of the carbon in nitrogen, and change of the porous structures was characterized by nitrogen adsorption techniques. As a result, it was found that the ratio between micro- and mesopores was easily varied. Electric double layer capacitance was measured as one of the applications for the mesoporous carbon with specific porosity, and the effect of pore control on capacitance was investigated. [Copyright &y& Elsevier]

Porous carbons were prepared by defluorination of poly-tetrafluoroethylene(PTFE) with various alkali metals and their porous structures were compared. Using sodium for defluorination resulted in a characteristic mesoporous carbon having a large mesopore volume with the narrow pore-size distribution of 2-3 nm diameter, in contrast to using potassium and rubidium which produced also mesoporous carbons but their pore-size distributions were wide spread. This difference seemed to be caused by the dispersion state of the alkali metal fluoride particles formed during defluorination. [ABSTRACT FROM PUBLISHER]

Highly mesoporous carbon material was prepared from defluorination of PTFE with lithium naphthalenide (LiC 10 H 8 ; radical anion), and its double layer capacitance was measured in 1.0 M LiClO 4 /propylene carbonate. The reaction product of PTFE film with LiC 10 H 8 had micro/nano domain structure consisting of one dimensional carbon chain (carbyne-like structure) and LiF. Although the carbon chain easily decomposed to amorphous carbon structure by chain crosslinking and LiF condensation through air exposure, highly mesoporous carbon was obtained by removal of fine LiF particles with dilute HClaq. This mesoporous carbon (PCPTFEr) showed larger capacitance (BET surface area: 1137 m 2 g −1 , capacitance: 123 F g −1 ) than activated carbon fiber with the almost same BET surface area (1151 m 2 g −1 , 74 F g −1 ). Additionally, PCPTFEr maintained the capacitance even at high current density. These properties of PCPTFEr can be due to the matrix carbon structure and, especially, the pore structure. [ABSTRACT FROM PUBLISHER]

Pore structure in carbon fibers prepared from a polymer blend has been investigated by measurements of small-angle X-ray scattering (SAXS). Generally, an application of the SAXS method to analyze the pore structure of carbon materials is not so easy, because that in carbon materials is complex and structure correlation between pores cannot be neglected. The polymer blend method does not use the activation process and makes it possible to control the size and concentration of pores dependent on the pore forming resin. It can be said that the present result is positioned as one of the most successful results among pore structure determinations by SAXS, and that the result will become a standard for the study of pore structure in carbon materials. [ABSTRACT FROM PUBLISHER]

Multi-wall carbon nanotubes (CNTs) with diameters between 10 nm and 20 nm were prepared by melt spinning, stabilizing and carbonizing of fine core/shell-1/shell-2 polymer microspheres. Microspheres were synthesized by three-steps soap free emulsion polymerization of methylmetacrylate (MMA) and acrylonitrile (AN) using potassium persulfate (KPS) as a polymerization radical initiator. The final composition of microspheres was PMMA core/PAN shell-1/PMMA shell-2 and diameter ca. 500 nm. The outer PMMA layer played the role of a matrix polymer. Microspheres were directly melt spun at ca. 300°C followed by stabilization of PAN at 220°C in oxygen and carbonization at 1000°C in nitrogen. TG-DTA study was used for clarifying the PAN thermal behavior during CNTs synthesis. SEM, TEM and HRTEM were used in characterizing the microspheres and CNTs morphology. [ABSTRACT FROM PUBLISHER]

Pore structure in carbon fibers prepared from a polymer blend has been investigated by measurements of small-angle X-ray scattering (SAXS). Generally, an application of the SAXS method to analyze the pore structure of carbon materials is not so easy, because that in carbon materials is complex and structure correlation between pores cannot be neglected. The polymer blend method does not use the activation process and makes it possible to control the size and concentration of pores dependent on the pore forming resin. It can be said that the present result is positioned as one of the most successful results among pore structure determinations by SAXS, and that the result will become a standard for the study of pore structure in carbon materials. [ABSTRACT FROM AUTHOR]

Highly mesoporous carbon material was prepared from defluorination of PTFE with lithium naphthalenide (LiC 10 H 8 ; radical anion), and its double layer capacitance was measured in 1.0 M LiClO 4 /propylene carbonate. The reaction product of PTFE film with LiC 10 H 8 had micro/nano domain structure consisting of one dimensional carbon chain (carbyne-like structure) and LiF. Although the carbon chain easily decomposed to amorphous carbon structure by chain crosslinking and LiF condensation through air exposure, highly mesoporous carbon was obtained by removal of fine LiF particles with dilute HClaq. This mesoporous carbon (PCPTFEr) showed larger capacitance (BET surface area: 1137 m 2 g -1 , capacitance: 123 F g -1 ) than activated carbon fiber with the almost same BET surface area (1151 m 2 g -1 , 74 F g -1 ). Additionally, PCPTFEr maintained the capacitance even at high current density. These properties of PCPTFEr can be due to the matrix carbon structure and, especially, the pore structure. [ABSTRACT FROM AUTHOR]

Porous carbons were prepared by defluorination of poly-tetrafluoroethylene(PTFE) with various alkali metals and their porous structures were compared. Using sodium for defluorination resulted in a characteristic mesoporous carbon having a large mesopore volume with the narrow pore-size distribution of 2-3 nm diameter, in contrast to using potassium and rubidium which produced also mesoporous carbons but their pore-size distributions were wide spread. This difference seemed to be caused by the dispersion state of the alkali metal fluoride particles formed during defluorination. [ABSTRACT FROM AUTHOR]

Multi-wall carbon nanotubes (CNTs) with diameters between 10 nm and 20 nm were prepared by melt spinning, stabilizing and carbonizing of fine core/shell-1/shell-2 polymer microspheres. Microspheres were synthesized by three-steps soap free emulsion polymerization of methylmetacrylate (MMA) and acrylonitrile (AN) using potassium persulfate (KPS) as a polymerization radical initiator. The final composition of microspheres was PMMA core/PAN shell-1/PMMA shell-2 and diameter ca. 500 nm. The outer PMMA layer played the role of a matrix polymer. Microspheres were directly melt spun at ca. 300°C followed by stabilization of PAN at 220°C in oxygen and carbonization at 1000°C in nitrogen. TG-DTA study was used for clarifying the PAN thermal behavior during CNTs synthesis. SEM, TEM and HRTEM were used in characterizing the microspheres and CNTs morphology. [ABSTRACT FROM AUTHOR]

The double layer capacitance of highly pure single-walled carbon nanotubes (SWCNTs) prepared by the HiPco™ process was measured in 1.0 mol dm−3 LiClO4/propylene carbonate solution. The unpurified SWCNT electrode was mainly composed of a bundle structure of SWCNTs with around 1.0 nm tube diameter, small amount of amorphous carbons, and Fe catalyst particles. The Fe catalysts in the surface of the SWCNT were removed by immersion in HClaq. The αs-SPE analysis of the N2 adsorption isotherms revealed that both the SWCNTs before and after the immersion in HClaq had relatively high specific surface areas of ∼500 m2 g−1 without microporosity although the tube ends were closed. The SWCNTs showed a gravimetric capacitance of around 45 F g−1. Thus, the specific capacitance per unit surface area was estimated to be around 10 μF cm−2, which was higher than that of conventional activated carbon fibers. Furthermore, the capacitance of the SWCNTs did not decrease even at high current density. This good rate property of the SWCNTs is related to the large area of the external surface (∼400 m2 g−1) on which ion adsorption/desorption can proceed fast because of no ion sieving. On the other hand, most of the Fe catalyst in the SWCNT could be removed by thermal oxidation followed by immersion in HClaq. However, the gravimetric capacitance of this purified SWCNT was not as great as that expected by the correlation of 10 μF cm−2. This is related to the formation of amorphous carbons caused by the thermal oxidation. [Copyright &y& Elsevier]