Rigid thermal insulation material fabricated from carbon fiber felt has been used for high temperature applications such as heating in an artificial graphite furnace, e.g., silicon semiconductor manufacture. In this study, the high temperature electrical resistivity of rigid thermal insulation materials, one of its important properties, was measured by a prototype device developed by the author, and factors influencing it are investigated. The resistivity of rigid thermal insulation decreased by 60% during heating to 2000 °C. For temperatures above 2200 °C, different behaviors were observed between argon and nitrogen atmospheres. In the case of an Ar atmosphere, the high temperature resistivity decreased steeply as the temperature increased from 2200 to 2500 °C, but this was not observed when the atmosphere was changed to nitrogen. On the other hand, such a difference in the high temperature resistivity behavior above 2200 °C between Ar and N₂ atmospheres was barely noticeable for isotropic graphite and glass-like carbon.

Carbon fibers were prepared from a solution of ash-free coal (Hyper Coal; HPC), which was obtained by thermal-extraction from coal. The HPC used as a raw material was soluble in organic solvents, providing viscous and conductive solutions. Carbon precursor fibers were prepared by electro-spinning from a HPC/pyridine solution followed by carbonization at 900 °C. The carbon fibers were obtained as non-woven sheets. Evaluation of the pore structure of the resulting carbon fiber sheets based on Ar gas adsorption/desorption measurements showed that they contained a large number of ultrafine micropores (< 0.70 nm) without any activation treatment. It was also possible to obtain carbon fibers by thermal melting of the HPC, but in that case no pores were observed. Hence, carbon fibers with pores were obtained without any activation treatment only if they were prepared by electro-spinning from an organic solution of the HPC. These results indicate that we have developed a new preparation method for microporous carbon fibers without an additional activation process.

The nitrogen-doping of carbon materials has attracted attention as a technique for improving their electrical and chemical properties. In this study, nitrogen-doped porous carbon was prepared using penta-ethylene-hexa-amine (PEHA) as both carbon and nitrogen sources, and FeCl₃ as a catalyst. The use of FeCl₃ enabled carbonization and graphitization at relatively low temperatures within a short time of 3 min. It was revealed that the crystallinity of the carbon material obtained by heat treatment at 900 °C was relatively high, based on the XRD analysis. Its specific surface area was 280 m²/g and the nitrogen content was 4.2 at. %. The electrtic double-layer capacitance per unit mass of the obtained carbon in a sulfuric acid electrolyte solution was 190 F/g at a current density of 50 mA/g, retaining a high value of 175 F/g even at a high current density of 1000 mA/g. In addition, this carbon exhibited a high areal specific capacitance of 0.68 F/m². This superior performance, showing a large capacitance despite the small surface area, could be due to the nitrogen-doping. This carbon material would be the most suitable material for the electrode of an electric double layer capacitor (EDLC) because of its high conductivity and crystallinity, and the high nitrogen content that induces a large pseudo-capacitance.

Activated carbon was produced from banana peel by chemical activation with K₂CO₃. The impregnated K₂CO₃ influenced the carbonization behavior at temperatures below 500 °C and caused the specific surface area to increase between 400 and 500 °C. At temperatures above 700 °C, the char was gasified by the K₂CO₃, so that the specific surface area increased rapidly between 700 and 800 °C and decreased between 800 and 900 °C because of the excess gasification. The activated carbon produced at an impregnation ratio of 1.0 and a carbonization temperature of 800 °C had the maximum specific surface of 2445 m²/g. The amount of adsorbed methane on this activated carbon at 3.0 MPa was 265 mL (s.t.p.)/g, which is almost the same as that of a commercial activated carbon with an almost identical pore structure. The production of such an activated carbon from banana peel using K₂CO₃ is important because K₂CO₃ is much easier to handle than KOH.

Carbide derived porous carbons (CDCs) have attracted significant attention for electrode materials of electric double layer capacitors (EDLCs). The purposes of this thesis are to improve the performance of capacitors using the CDCs and establish an inexpensive manufacturing method of the CDCs. In Chapter 1, the background and purposes of this study have been introduced. In Chapter 2, the nanostructures of various CDCs have been characterized. In Chapter 3, by focusing on the silicon carbide derived porous carbons (SiC-CDCs) because of their cost and availability of their raw material, steam activation of the SiC-CDCs was conducted and their nanostructures were evaluated. In Chapter 4, EDLCs using the obtained SiC-CDCs were fabricated and electrochemically evaluated. In Chapter 5, using the SiC-CDCs, lithium ion capacitors (LICs) were prepared and evaluated to enhance the energy density of capacitors. Moreover, the floating durability of LICs was improved using the activated SiC-CDCs surface-modified by heat treatment. In Chapter 6, to obtain affordable SiC-CDCs, the SiC-CDCs was fabricated from rice husk as raw material, which is a common agricultural waste material.