Satoshi Matsuda

Pressure effects on nanotubes formation using the submerged arc in water method

Synthesis of multi-walled carbon nanotubes (MWCNTs) by an arc discharge between two graphite electrodes submerged in water under controlled pressure (from 400 to 760 Torr) is reported. Transmission and scanning electron microscopy investigations of the arc discharge product collected from the bottom of the reactor revealed high concentrations of MWCNTs at all pressures. Dynamic light scattering (DLS) on suspensions containing MWCNTs showed that the mean diameter of the nanotubes increases with decreasing pressure. Raman spectroscopy analysis reveals that the relative amount of disordered carbon is significantly less in the low-pressure samples. Furthermore, the yield of the deposit was found to be independent of the pressure. These results suggest that the physical properties of MWCNTs formed by the submerged arc can be controlled by varying the pressure.

Effect of nitrogen plasma-based ion implantation on joint prosthetic material

Abstract In total hip arthroplasty (THA), Ultra High Molecular Weight Polyethylene (UHMWPE) wear debris generated at the articular surface has been recognized as a long-term cause of loosening and failure of artificial hip joints due to osteolysis. The technique of ion implantation has been used to improve wear resistance of the metal femoral head. The Plasma-Based Ion Implantation (PBII) technique is more suitable for complex shaped implants such as femoral head and femoral prosthesis due to three-dimensional ion implantation effects. The effect of pulse voltage and cooling of the substrate of the PBII process for Co–Cr-based materials were examined in terms of wear resistance by the pin-on-disc wear test. The wear resistance of Co–Cr alloy with high nitrogen-ion implantation dose was superior to the untreated Co–Cr alloy. Their corrosion resistance has also been examined with an anodic polarization measurement. High dose and cooling of PBII process proved to be effective in enhancing corrosion resistance of Co–Cr alloy. In this study, it was confirmed that the improvement of wear and corrosion resistance of Co–Cr alloy modified by PBII, as well as high pulse voltage and cooling of the substrate for PBII were the most effective treatments.

Mode I and II delamination fatigue crack growth behavior of alumina fiber/epoxy laminates in liquid nitrogen

Mode I and II interlaminar fracture toughness and delamination fatigue crack growth behavior were investigated with unidirectional alumina fiber (ALF)/epoxy laminates at 77 K in liquid nitrogen. The mode I fracture toughness values at 77 K were higher than those at room temperature in laboratory air (RT). Although initial values of the fracture toughness under mode II loading was higher at 77 K than those at RT, the propagation values of the fracture toughness was insensitive to the test temperature. The fatigue crack growth threshold at 77 K under mode I loading was higher than that at RT. The stress ratio dependency under mode II loading at 77 K was completely different from that at RT. Then, the increase of the fatigue crack growth resistance at 77 K from that at RT was observed only under stress ratio, R=0.1. The difference of the fracture mechanism due to the test temperature and the loading mode was discussed on the bases of fracture mechanics and microscopic fracture mechanism consideration.

Adhesive strength and mechanisms of epoxy resins toughened with pre-formed thermoplastic polymer particles

The aim of this study was to characterize the adhesive properties of epoxy resins toughened with pre-formed polyamide-12 particles in comparison to the conventional approach using core–shell rubber particles. Dicyandiamide-cured diglycidyl ether of bisphenol-A was used as the base epoxy resin. The T-peel adhesive strength of the toughened resin containing 20 phr polyamide-12 particles was about 3-times higher than that of the unmodified resin. In the case of rubber toughening, the improvement in adhesive strength tended to reach a plateau, even after improvement in the resin toughness itself. Besides, the polyamide particle toughening utilizes the bulk resin toughness for the peel adhesive strength, even in a thin adhesive layer between the substrates. The polyamide particles embedded in epoxy resin matrix were fractured after bridging cracks and stretching in the peel process. The crack-bridging mechanism by the pre-formed thermoplastic polymer particles was operative behind the crack-tip and would, therefore, experience a relatively small constraint by the presence of rigid metal substrates in comparison to conventional rubber toughening. The requirements for the polymer particles to work as a modifier using the bridging mechanism would be good adhesion to the epoxy matrix, high toughness and a relatively lower modulus of elasticity than that of matrix resin.

Mode II interlaminar properties under static and fatigue loadings for CF/epoxy laminates with different fiber-surface treatment

The effect of fiber-surface treatment on delamination fatigue under mode II loading was investigated for unidirectional CF/epoxy laminates. Two types of laminates were made from surfacetreated or surface-non-treated carbon fiber, and a common epoxy matrix. Tests were carried out using end notched flexure (ENF) specimens. Stabilized mode II static tests showed that the fracture toughness of the surface-treated CFRP was 30% higher than that of non-treated CFRP. Fatigue crack growth resistance of the surface-treated CFRP was higher than that of non-treated CFRP at higher crack growth rate. However, the effect of fiber surface treatment was negligible near the threshold region. At higher growth rate, interfacial fracture occurred prior to the matrix fracture near the crack tip for the non-treated CFRP. Then, the fracture mechanism was controlled by the interfacial fracture. On the other hand, the resin fracture with plastic deformation occurred prior to the interfacial fracture near the crack tip for the surface-treated CFRP. Then, the fracture mechanism was controlled by the resin fracture. Near the threshold region, the ratio of the resin fracture was rather large without respect to the fiber-surface treatment. The main fracture mechanisms near the threshold region were only controlled by the matrix resin. This fact was well correlated to the fact that the threshold value was insensitive to the fiber-surface treatment.

Composite Materials. Effect of Fiber Surface Treatment on Mode II Delamination Fatigue for CF/Epoxy Laminates.

Effect of fiber surface treatment on delamination fatigue under mode II loading was investigated for unidirectional CF/Epoxy laminates. Two types of laminates were made from surface-treated-carbon fiber or surface-non-treated fiber, and a common epoxy matrix. Tests were carried out using end notched flexure (ENF) specimens. Stabilized mode II static tests showed that the fracture toughness of the surface-treated CFRP was 30% higher than that of non-treated CFRP. Fatigue crack growth resistance of the surface-treated CFRP was higher than that of non-treated CFRP at higher crack growth rate. However, the effect of fiber surface treatment was negligible near the threshold region. At higher growth rate, the interfacial fracture occurred prior to the matrix fracture near the crack tip for the non-treated CFRP. Then, the fracture mechanism was controlled by the interfacial fracture. On the other hand, the resin fracture with plastic deformation occurred prior to the interfacial fracture near the crack tip for the surface-treated CFRP. Then, the fracture mechanism was controlled by the resin fracture. Near the threshold region, the ratio of the resin fracture was rather large without respect to the fiber-surface-treatment. The main fracture mechanisms near the threshold region was only controlled by the matrix resin. This fact was well correlated to the fact that the threshold value was insensitive to the fiber surface treatment.