This review explores recent research regarding mesophase pitch (MP). Spinnable mesophase pitch (SMP) was used as a model pitch for MP in all experiments. We explain some phenomenological results of the lyotropic liquid crystalline properties of the SMP, which show that the MP behaves as a typical lyotropic liquid crystal. The mesogenic and solvent components of SMP are defined. We define the threshold concentration (TC) as the minimum amount of mesogenic component necessary for SMP to achieve 100 vol% anisotropy. We also report the TCs of various SMPs and discuss the effects of the solvent component. Concerning the identity of the mesogenic component, we discuss quantitative correlations between the size of the layered molecular stacking units and the anisotropic content of the SMP. Research has shown that a layered molecular stacking unit larger than a specific size corresponds to the mesogenic component of the MP. We discuss a novel method for the manufacture of SMPs using our understanding of MP as a lyotropic liquid crystal, which comprises thermal mixing of optimal amounts of the mesogenic and solvent components that were prepared separately under different conditions. This method enables the properties of each component to be optimized without involving a costly hydrogenation process. Finally, we discuss how this approach can be used to increase SMP yield by modifying the contents of the anisotropic mesogenic and solvent components.

Transparent antennas have attracted much attention because they can meet the demands of the Internet of Things (IoT) and fifth generation (5G) mobile communication technologies. From this point of view, intensive research and development has been carried out to produce materials with high optical transparency and low electrical resistance. Research on graphene transparent antennas is reviewed along with our experimental demonstration. The unique features of graphene as a material for transparent antennas are introduced and compared to the characteristics of metal-based and metal-oxide transparent conductors. The challenges involved in the fabrication of transparent antennas using graphene films grown by chemical vapor deposition (CVD) are described. Fabrication techniques of transparent antennas (transfer and patterning methods) and techniques to decrease the sheet resistance of the graphene films (stacking and doping methods) are described. The performance of the CVD graphene transparent antennas we have fabricated are presented.

In recent years, in order to accurately predict the mechanical properties of carbon fiber-reinforced plastic by computer-aided engineering, it has become important to understand the mechanical properties of carbon fiber as a reinforcement material. Since carbon fiber is a material whose properties are highly anisotropic, information on tensile properties only in the axial direction of the fiber is not sufficient for predicting composite properties, and tests to obtain properties in various directions are desired. This paper discusses the anisotropy of carbon fibers by presenting the results of our previous tests on carbon fiber monofilaments, including observation of the changes in fiber diameter, dynamic and static torsion tests, torsion-tension tests, transverse crush tests, axial compression tests and three-point bending tests, and finite element method analysis using elastic moduli obtained from these tests.

Nitrogen-doped zeolite-templated carbon (N-doped ZTC) is synthesized using NaY zeolite as a template and with acrylonitrile (AN) and propylene as the respective nitrogen and carbon sources. AN is directly mixed with the dried zeolite for adsorption and the mixture is heated to synthesize polyacrylonitrile (PAN) inside the zeolite micropores. Each AN adsorption and polymerization step require only 1 h and both steps were performed in a single container. The resulting zeolite/PAN composite was then subjected to chemical vapor deposition using propylene to fill the zeolite pores with carbon. Subsequently, heat treatment was used for carbonization and the zeolite was removed with hydrofluoric acid. The N-doped ZTC has three-dimensionally ordered and interconnected micropores with a uniform pore size of 1.2 nm, inheriting the structural regularity of the zeolite. The optimum volume of AN is determined to be the same as the total pore volume of the zeolite, which accounts for the high surface area of 3680 m² g⁻¹ and high structural regularity with a N/C molar ratio of 0.015. The performance of the N-doped ZTC as an electric double-layer capacitor electrode was evaluated using an organic electrolyte and showed a superior performance to undoped ZTC and maintained a high capacitance retention up to 2 A g⁻¹.

The surface properties of carbons significantly influence their performance when they are used as lithium-air battery cathodes. This study used carbon nanofiber sheets derived from polyacrylonitrile (PAN) nanofiber sheets and prepared by electrospinning (ES-CNF) as a model cathode to investigate the influence of surface properties. The sheet structure enabled sufficient access of O₂ to the carbon surface. For this investigation, five types of ES-CNF sheets having different surface properties were prepared by varying the heat-treatment temperature from 800 to 2200 °C. A portion of the heat-treated samples were further treated with nitric acid. The surface properties of the obtained samples were analyzed in detail by temperature programmed desorption analysis conducted under vacuum in the temperature range 100–1800 °C. The results indicated that discharge and charge voltages depend on the number of edge-H and the type and number of carbon functional groups. Oxygen-containing functional groups on the carbon promoted not only the surface-route deposition of Li₂O₂, which can be charged (decomposed) at voltages below 3.7 V, but also undesired side reactions, which can increase the charge voltage up to over 4.0 V. Furthermore, it was also found that carboxyl or phenol/ether groups effectively promote surface-route reactions much more efficiently than N-containing functional groups (NCFGs) and carbonyl groups. The knowledge obtained in this study can be utilized as a new guideline to design cathode carbon for lithium-air batteries.