Steel coated with diamond film is excellent material specifically for cutting tools. However, direct diamond deposition has been considered difficult. In the present study, a stainless steel surface was mechanically processed to directly deposit diamond on it. Diamond film was rarely obtained when the steel surface was rasped with sandpaper, metal file, or ground with a flat drill. In most cases, amorphous carbon was deposited on the surface. On the other hand, high-quality diamond was often deposited when regularly arranged pits were created on the surface using a drill. In this case, the diamond was deposited on the lips of the pits and the flat (nonprocessed) areas between (rather than on the inside of) the pits. The quality of diamond film obtained in the present work is the best reported for direct diamond chemical vapor deposition (CVD) on steel. It is an important discovery that high-quality diamond film can be directly deposited on steel surfaces via simple mechanical surface processing without interlayer or seeding.

Hydrogen is a candidate of alternative fuels and evaluated for fuel cell (FC) applications. As a hydrogen storage system, metal hydride (MH) is attracting attention due to its high energy volume density and safety. To apply fuel cells and metal hydride to electrically power assisted bicycles, a previous study has evaluated load weight and power demand through experiments conducted on existing electrically power assisted bicycles. Focusing on such energy supply system, this study designs metal hydride cartridge and investigate temperature changing when exhaust heat from fuel cell is supplied to metal hydride, which release hydrogen with absorbing heat. First, the negative effect of the exhaust heat supply to the fuel cell on the fuel cell performance is investigated and we proposed the usage of method to mitigate the effect. Next, the structure of MH cartridge is designed from weight and volume of the MH cartridge and exhaust flow rate of the FC, and we proposed a structure in which multiple small cylinders are stacked. Finally, FC exhaust heat was supplied to the designed dummy cartridge, and the amount of heat supply according to the FC output and power generation time was evaluated.

Based on past studies, many reaction models have been used to replicate the thermal degradation of plastic polymers. In this work, we analyse the change in yield using two types of reaction model, the first-order reaction model and the two-step consecutive reaction model of three plastic samples under an isothermal heating condition. This is due to the difficulty of using conventional method such as KAS, FWO or Coats-Redfern method which requires a heating rate. It is found that the first-order reaction model is more suited to replicating the yield curve under a low temperature while the consecutive reaction is more suitable under a high temperature. For example, using the first-order reaction model, we were able to replicate the yield curve of polystyrene, polyethylene and polypropylene under the temperature 593 K ≤ T_S < 623 K，643 K ≤ T_S < 693 K and 623 K ≤ T_S < 653 K respectively while anything higher than that can only be replicated using the two-step consecutive reaction model. The apparent activation energy in this study has to be separated using three different reaction rate K₁, K₂ and K₃ which shows a range of 106 ~ 396 kJ/mol.