Yoshio Fuwa

Tribological Characteristics of Carbon Nano-Fiber Dispersed Silicon Nitride Based Composites in High-Temperature Fuel

The effect of carbon nano-fiber (CNF) dispersion on the tribological behavior of Si3N4 based composites against bearing steel were investigated in kerosene. The friction coefficients were not affected by the CNF addition. On the other hand, the wear rates of Si3N4/CNF composites showed a minimum value on 3 mass% CNF additions. The primary wear mechanism of Si3N4 is considered to be controlled by oxidation wear of Si3N4 due to a trace amount of water as impurity in the kerosene.

Effect of Applied DC Voltage to Stainless Steel Pin and CNx Coated Disk in Pin-on-Disk Sliding Test on Tribological Properties

The effect of applied DC voltage on the friction and wear of CNx sliding against stainless steel pin in air was clarified. Friction coefficient decreased with the increasing negative voltage to apply to the ball and disk in air. On the other hand, positive voltage increased friction coefficient. Friction coefficient of CNx in air decreased from 0.22 to 0.05 by applying electric voltage of DC −200 V. Specific wear rate was decreased with the increasing applied positive and negative voltage. It was considered that the oxidation of CNx was controlled by electric field.Copyright

Effect of the Shear Strength of Coating of CNx on Friction Sliding Against Si3N4 Pin in Nitrogen

It was reported that CNx coating showed low friction coefficient less than 0.01 when it slid against Si3 N4 ball in dry N2 . It is suggested that the super-low friction was caused by the structural change of CNx surface to graphite-like structure during sliding in N2 . In this study, to investigate the effect of N2 gas on shearing and adhesive strength of CNx, micro scratching tests were examined in N2 and air with a diamond tip (radius = 2.0 μm). Main results are the followings: (1) CNx surface after sliding in N2 against Si3 N4 ball showed lower scratching friction coefficient in N2 than that in air. (2) Adhesive strength Si was estimated as 1/10 times lower than that in air.Copyright

A novel technique for evaluation of articular cartilage lubrication based on the surface plasmon resonance

Evaluation of lubrication in articular cartilage has been developed with various techniques in order to obtain reasonable explanations about this superb mechanism. However, a definitive theory about this mechanism of lubrication is not clear until present time. One of the most relevant restrictions for the comprehension of this mechanism is the difficulty to detect and to evaluate the surface layer of articular cartilage. Acquisition of images from the conventional techniques are not sufficient for the analysis of the surface layer conditions because the most of methods require the dehydration of specimens which change their physiological state. In addition, methods that allow the evaluation of articular cartilage in the aqueous environment do not provide sufficient and clear data for a definitive evaluation. In this work, we present the application of Surface Plasmon Resonance (SPR) principle in the evaluation of articular cartilage surface. In our apparatus, it is possible to acquire images of articular cartilage surface during the lubrication experiments and in the aqueous environment. Variations in the reflectance were used in order to identify the substances present in the surface layer, since the intensity of light depends on the chemical characteristics of the substances located on the articular cartilage surface. The correlation of friction behavior with the possible substances present in the surface layer of articular cartilage can contribute to clarify the mechanism of lubrication of articular cartilage.