The nanostructure of MgO-templated carbon synthesized through the decomposition of magnesium citrate was examined, and its structural change induced by heat-treatment was traced using various analysis techniques. A high resolution TEM analysis revealed that the carbon consisted of hollow nanoparticles with a size of 10 nm where the thickness of the carbon walls (shells) is several nanometers. N₂ adsorption analysis indicated that the MgO-templated carbon before the heat-treatment was highly mesoporous and microporous with a BET specific surface area as large as 1600 m²/g. Such a porous structure was almost unchanged even for the carbon heat-treated at 2000 °C, although surface areas of activated carbons were usually decreased in the lower temperature ranges. Above 2000 °C, the carbon nanostructure observed by TEM changed so that it was similar to heat-treated glassy carbon which is normally non-graphitizable. The templated-carbon, however, was graphitized by multiphase graphitization process with three different (004) diffraction peaks of carbon. The reason why such inconsistency occurred was not clear, but could be because of the difference in the surface area which is negligible for glassy carbons but not for the MgO-templated carbon.

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A mesophase pitch-based submicron carbon-fiber web, non-woven fabric, was prepared using an aqueous solution of polyvinyl alcohol (PVA). The dispersion of mesophase pitch in the PVA solution was electrospun to form a web of submicron carbon fibers. The carbon-fiber web was heat-treated at 2800 °C in argon. The diameters of the carbon fibers were 200 to 800 nm. The XRD peak near 2θ=26°, which corresponds to the (002) diffraction peak of graphite, was broad and at slightly lower angle compared to that of the graphite powder because of the less crystalline nature and the smaller size of the mesophase pitch-derived graphitic particles. TEM observation indicated that the fiber consists of aggregates of mesophase pitch-derived small graphitic particles surrounded by an amorphous substance likely originating from the PVA.

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The relationships between the density measured by butanol immersion (real density D_R) and the XRD parameters were examined during the graphitization of three kinds of coke; pitch cokes with mosaic and needle-like textures and a petroleum coke. The heat treatment was performed at 2100∼3000 °C for 5∼960 min. The dependences of XRD parameters, c₀, L_c and L_a, on D_R were clearly different on the three cokes, particularly the dependence of c₀ on D_R being approximated linear. The results suggest that these relationships depend strongly on the origin of the cokes, either coal-tar pitch or petroleum and whether they have a mosaic or needle-like texture. In order to consider these relationships, crystal density D_C calculated from c₀ and a₀ was compared with observed D_R, suggesting that the volume of “closed voids” in the particle, which was calculated as (D_C-D_R)/D_C, and its change during graphitization was characteristic for each coke.

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Wood biomass charcoal loaded with calcium was produced and the effects of the conditions of calcium-loading and carbonization on the product properties were examined. Calcium on charcoal was mainly CaCO₃. In addition, the effects of calcium loading onto charcoal were examined for the removal of phosphorus from an aqueous solution. The amount of phosphorus removed increased with calcium loading while the amount removed by charcoal without calcium loading were small. Calcium phosphate would be produced on charcoal by the reaction of calcium on charcoal with phosphorus in aqueous solution.

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The electrical and thermal conductivities in the basal plane of graphite films prepared from aromatic polyimide films were evaluated with reference to previously measured electrical and thermal conductivities along their longitudinal directions at room temperature with the aid of magnetoresistance anisotropy measurement at 77 K. The average crystal-grain size of each graphite film was obtained from the relation between thermal conductivity and grain size originally derived by Klemens and Pedraza. It was found that at room temperature the crystal-grain boundary scattering of phonons could dominantly occur for crystal-grains with sizes smaller than ∼520 nm or the average d₀₀₂ value of grains larger than ∼0.3357 nm. When the grain size exceeds the intrinsic phonon mean free path in a single graphite crystal, i.e. ∼1760 nm, or the average d₀₀₂ value of the crystal-grains is less than ∼0.3357 nm, the three phonon process in thermal conduction becomes dominant. The mean free paths of carriers were found to be much shorter than those of phonons and it was shown that at 77 K grain sizes smaller than ∼220 nm could cause boundary scattering of carriers. The total carrier density at 77 K evaluated from the magnetoresistance and electrical conductivity data shows a decrease from the value of a single crystal of graphite as the crystallinity of the graphite film is reduced.

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A new ¹³C-NMR measurement technique, named fused-state ¹³C-NMR, has been developed. Using this technique, many aspects of carbonaceous mesophase have been elucidated: Constituents of soft mesophase have methyl and/or naphthenic groups whereas those of hard mesophase have no aliphatic groups. The order parameter of carbonaceous mesophase in the nematic phase is about 0.7. Very small molecules such as hexamethylbenzene and pyrene orientate in a carbonaceous mesophase. In a liquid crystalline phase, all oriented molecules in a carbonaceous mesophase (including the small molecules trapped in the mesophase) fluctuate around the orientation axis in the same manner. That is, an oriented molecule behaves as if it were trapped between two walls the distance between which is about 1.0 nm. The analyzed results rule out the assertion that soft mesophase is a gel and also rule out the existence of basic structural units. A constructed model for molecular ordering in a mesophase has clarified some pending questions on carbonaceous mesophase.

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Nanographene inherits unprecedented electronic and magnetic properties from graphene due to its electronic feature from massless Dirac Fermion. In addition, around the zigzag-shaped edges of nanographene sheet, a nonbonding π-electron state called edge state is generated and located at the Dirac point where the bonding π- and antibonding π^*-band contacts. The edge state gives a localized spin, which results in unconventional nanomagnetic features and chemical activity to the nanographene sheets. Activated carbon fiber (ACFs) is an ideal candidate to access the magnetism of nanographene experimentally, which features a disordered flexible 3D network of nanographite domains, assembled by loose stacking of 3 to 4 nanographene sheets with a mean in-plane size of 2 to 3 nm. Besides, a large amount of nanosized interstitial spaces (nanopores) are distributed between the nanographite domains. The presence of nanopores accommodates large amounts of guest molecules, where the host-guest interaction plays an important role in modifying the electronic and magnetic properties of not only the host nanographite but also the guest species. In addition, many oxygen-containing functional groups, most of which are hydrophilic, are bonded to the nanographene edges, such as carboxyl, carbonyl and phenol groups.
In view of magnetism, the research in this thesis focuses on the interaction between nanographene and nitric acid with strong electronaccepting nature. Some important phenomenon is observed, such as the charge transfer interaction between host and guest, the decomposition of HNO₃ molecules, and the behavior of decomposed magnetic species in the nanopores and their interactions with edge-state spins.

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This thesis describes the results of the investigations on the catalytic activity and their active sites of carbon alloy catalysts, where carbon alloy catalysts represent the carbon based catalysts prepared by introducing heterogeneous carbon structure or heteroatoms into carbon matrices. The reactions investigated here were electrochemical reduction of oxygen molecule (ORR) and two organic reactions, Knoevenagel reaction and transestrification reaction. The studies on the ORR activity revealed the importance of the defective structure due to the partial sp³-character of the carbon atoms constructing the catalysts. The studies on the catalytic activities for base-catalyzed organic reactions were conducted with nitrogen-doped carbon alloy catalysts, which estimated that the nitrogen containing active sites were associated with the oxygen functional groups. This thesis finally demonstrated the possibility of the carbon alloy catalysts for applying to the extended areas and provided a guideline for designing the high-performance carbon alloy catalysts.

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