Linear carbon chains (LCCs) encapsulated inside the hollow cores of carbon nanotubes (CNTs) have been experimentally synthesized and structurally characterized by Raman spectroscopy and transmission electron microscopy. However, in terms of electronic conductivity, their transportation mechanism has not been investigated theoretically or experimentally. In this study, the density of states and quantum conductance spectra were simulated through density functional theory combined with the non-equilibrium Green function method. The encapsulated LCCs inside (5,5), (6,4), and (9,0) single-walled carbon nanotubes (SWCNTs) exhibited a drastic change from metallic to semiconducting or from semiconducting to metallic due to the strong charge transfer between them. On the other hand, the electronic change in the conductance value of LCCs encapsulated inside the (7,4) SWCNT were in good agreement with the superposition of the individual SWCNTs and the isolated LCCs owing to the weak charge transfer.

Surfactant-wrapped separation methods of metallic and semiconducting single-walled carbon nanotubes (SWCNTs) can result in large changes in intrinsic physical and chemical properties due to electronic interactions between a nanotube and a surfactant. Our approach to synthesize SWCNTs with an electronic feature relied on utilizing carbon nanorings, [n] cycloparaphenylenes ([n]CPPs), which are the fundamental unit of armchair type SWCNTs (a-SWCNTs) that possess a metallic feature without any surfactants. To obtain long tubular structures from [n]CPPs, the host-guest complexes formed with well-aligned [n]CPP hosts and various fullerene guests on a silicon substrate were pyrolyzed under an ethanol gas flow at a high temperature with focused-ultraviolet laser irradiation. The pyrolyzed [n]CPPs were observed to transform from nanorings to tubular structures with 1.5–1.7 nm diameters corresponding to the employed diameter of [n]CPPs. Our approach suggests that [n]CPPs are useful for structure-controlled synthesis of SWCNTs.

TZM alloy having elongated coarse-grain structure was developed by three-step internal nitriding treatment at 1423 to 1873 K in and subsequent recrystallization treatment at 2173 K in vacuum. Some specimens were subjected to re-nitriding treatment at 1873 K for 16 h. After the recrystallization treatment, aspect ratio (L/W) of grains for rolling direction was about 50 at the maximum. Yield stress obtained at 1773 K after re-nitriding treatment was about 6 times as large as that of recrystallized specimen. Re-nitriding was very effective in the improvement in strength of TZM alloy having elongated coarse-grain structure.

In order to overcome the recrystallization embrittlement and irradiation embrittlement of Mo, which are major problems for its fusion applications, internally nitrided Mo alloys were prepared by a novel multi-step internal nitriding. Neutron irradiation was performed in the Japan Material Testing Reactor (JMTR). After irradiation, nitrided Mo alloys exhibited ower ductile-brittle transition temperature than irradiated TZM. These results suggested that multi-step internal nitriding was effective to the improvement in the embrittlement by irradiation. Transmission electron microscope observation revealed that TiN particles precipitated by nitriding acted as a sink for irradiation-induced defects.

For pure Molybdenum carburized in mixed gases of argon and carbon monoxide, microstructural observations were carried out. X-ray diffraction analysis for carburized specimens revealed that brittle - layer hardly formed in the case of low carbon monoxide concentration. Fracture strength of the specimen carburized at 1673 K for 16 h is about 550 MPa higher than that of the un-carburized specimen. SEM observation revealed that with increasing carburizing temperature, the region demonstrating a transgranular fracture mode progressed towards the center of specimen. This result means that the grain boundaries were strengthened by the grain boundary diffusion of carbon and the strength of grain boundaries exceeded that of grain itself.

Internally nitrided dilute W-Ti alloy specimens having a heavily deformed surface microstructure were prepared by a multi-step internal nitriding at 1573-2073 K. Primary nitriding below their recrystallization temperature induced a precipitation of ultrafine TiN particles. After secondary and tertiary nitriding, those precipitates grew into rod-like TiN with a length of 20-60 nm. The recrystallization temperature after nitriding was elevated above 2073 K. The yield strength at 1773 K obtained from nitrided W-0.5 mass% Ti alloy was about 5 times as large as that of the recrystallized specimen. DBTT of the nitrided alloys was about 373 K.

PCBN tools are used worldwide for machining of hardened steel parts in automotive industries. But in heavy interrupted cutting of hardened steel, the tool life is not so stable by sudden breakage of the cutting edge, and total cost of cutting by PCBN is not so economical compared to the grinding. To solve this problem, new PCBN has been developed. New PCBN has very fine and homogeneous microstructure to increase the toughness of sintered body that it provides a reliable tool life for heavy interrupted cutting.