Noboru Nakayama

Biocompatibility and bone tissue compatibility of alumina ceramics reinforced with carbon nanotubes

AIMS The addition of carbon nanotubes (CNTs) remarkably improves the mechanical characteristics of base materials. CNT/alumina ceramic composites are expected to be highly functional biomaterials useful in a variety of medical fields. Biocompatibility and bone tissue compatibility were studied for the application of CNT/alumina composites as biomaterials. METHODS & RESULTS Inflammation reactions in response to the composite were as mild as those of alumina ceramic alone in a subcutaneous implantation study. In bone implantation testing, the composite showed good bone tissue compatibility and connected directly to new bone. An in vitro cell attachment test was performed for osteoblasts, chondrocytes, fibroblasts and smooth muscle cells, and CNT/alumina composite showed cell attachment similar to that of alumina ceramic. DISCUSSION & CONCLUSION Owing to proven good biocompatibility and bone tissue compatibility, the application of CNT/alumina composites as biomaterials that contact bone, such as prostheses in arthroplasty and devices for bone repair, are expected.

Anisotropic Sm–Fe–N magnets produced by compression shearing method

Sm–Fe–N bulk magnet was produced by the compression shearing method. X-ray diffraction studies revealed that the magnet retained the original Sm2Fe17N3 phase structure without any appreciable decomposition of the Sm2Fe17N3 phase and that this phase had a pronounced crystallographic alignment. Magnetic measurements confirmed that the Sm–Fe–N magnet was magnetically anisotropic. The bulk anisotropic Sm–Fe–N magnet exhibited a high remanence value of 9.43kG with a high coercivity of 11.0kOe.

Tribological properties of Al–Si–Cu–Mg alloy-based composite-dispersing diamond nanocluster

This paper describes the tribological properties of diamond nanocluster-dispersed Al-Si-Cu-Mg composite with a comparison to those of diamond-like carbon (DLC)-coated Al-Si-Cu-Mg alloy. Al-Si-Cu-Mg composites containing diamond nanoclusters are fabricated in a powder metallurgy process combined with high-energy ball milling and dynamic consolidation. Friction measurements are made at various loads (0.02-0.2 N) and sliding speeds (0.05-5.0 mm/s) to examine the friction coefficient and wear width, compared to those of Al-Si-Cu-Mg alloy and a DLC-coated alloy. The results indicate that the friction coefficient and wear width of the composite have a tendency to reduce with a decrease in the load and sliding speed, and that they show lower values than DLC-coated samples at <0.1 N, and <0.5 mm/s. The topographical and frictional images in the composite are investigated with AFM, and the reduction of friction in the mesoscopic level can be observed in the diamond nanocluster-dispersed composite.

Consolidation of Nd-Fe-B melt-spun ribbon by compression shearing method

Commercially available Nd–Fe–B melt-spun ribbons (MQ powders) were consolidated at temperatures ranging from room temperature to 573K in ambient atmosphere by the compression shearing method. The resultant bulk materials consisted of the Nd2Fe14B phase together with a small amount of the soft magnetic α-iron phase. The bulk material consolidated at room temperature was magnetically isotropic as was the case for the MQ powders. On the other hand, the bulk material consolidated at 573K was found to be magnetically anisotropic and showed a remanence of 9.2kG, higher than that of the MQ powders.

Titanium Fiber Plates for Bone Tissue Repair

Titanium plates are widely used in clinical settings because of their high bone affinity. However, owing to their high elastic modulus, these plates are not suitable for bone repair since their proximity to the bone surface for prolonged periods can cause stress shielding, leading to bone embrittlement. In contrast, titanium fiber plates prepared by molding titanium fibers into plates by simultaneously applying compression and shear stress at normal room temperature can have an elastic modulus similar to that of bone cortex, and stress shielding will not occur even when the plate lies flush against the bones surface. Titanium fibers can form a porous structure suitable for cell adhesion and as a bone repair scaffold. A titanium fiber plate is combined with osteoblasts and shown that the titanium fiber plate is better able to facilitate bone tissue repair than the conventional titanium plate when implanted in rat bone defects. Capable of being used in close contact with bone for a long time, and even capable of promoting bone repair, titanium fiber plates have a wide range of applications, and are expected to make great contributions to clinical management of increasing bone diseases, including bone fracture repair and bone regenerative medicine.

Dynamic Molding of Powder Particles at Room Temperature

A new method of solidifying metal powder by dynamic molding under compression stress was developed. In the solidified specimen, recrystallization is suppressed, so that nanoscale crystal grains remain. The hardness of the specimen prepared by this process is increased relative to materials prepared by other methods. The material properties and preferred orientation of an aluminum plate with crystal grains 100−200 nm in diameter prepared by the new molding process are reported. The correlation between the crystal structure and properties of crystallization are clarified.

Consolidation of Ti Powder by a Compression Rotation Shearing System at Room Temperature - Effect of Pivot Rotation Speed on Consolidation

Ti has high strength, good corrosion resistance, is lightweight and shows good biocompatibility. It has thus been used extensively for mechanical and medical structural components. On the other hand, the disadvantages of Ti include a high melting point, ease of oxidization at high temperatures, low specific heat and low thermal conductivity. There are three specific problems associated with Ti metallurgy. The first is that powder metallurgical processing requires high temperatures and a high vacuum, the second is that samples produced by existing powder metallurgy techniques have a low density, and the third is the occurrence of burning because of a local temperature rise during the cutting process. Therefore, in the present work, a new high-speed, room-temperature molding process involving compression rotation shearing was developed. This method can be used for solidification of metal powders by enforced plastic flow and breaking of oxide films. Therefore, no external heat is required and the molding time is short. The proposed method represents an easy approach to consolidating high melting point metallic materials.

Friction and Mechanical Properties of Cluster Diamond Dispersed Epoxy Resin

Abstract In the present paper, epoxy resin based composite materials with nanosize diamond (graphite cluster diamond, GCD) added to constitute 0 - 5 vol.-% were prepared, with the aim of developing a solid lubricating composite material using epoxy resin as the matrix. The materials mechanical properties and friction coefficient were measured. Density measurement showed that the compacted GCD dispersed epoxy resin based composite had a relative density of 1·0. The bending modulus of elasticity remained constant, regardless of changes in the GCD content; however, the bending strength dropped rapidly as the volume fraction of the GCD was increased. The addition of GCD to the matrix system reduced the friction coefficient.

Mechanical and Electrical Properties of Carbon Nanofiber Dispersed Ti Composite Formed by Compression Shearing Method at Room Temperature

The materials used for fuel cell separators require a bending strength of more than 70 MPa. Therefore, the contact resistance is required to be 10 mΩ∙cm2, respectively. In the present study, vapor grown carbon nanofibers (VGCF) were added to Ti composite using the compression shearing method at room temperature. The mechanical properties of the compacted powder were then measured. The microstructure of the Ti/VGCF composite material was Ti with dispersed VGCF (not alloyed). In addition, the bending strength of all Ti/VGCF composites was more than 800 MPa, and the bending strength of 0-1 vol% VGCF composites was twice as much as that for Ti rolled material (ASTM grade 2). Ti/VGCF thin plates also exhibited excellent electrical property. The contact resistance of 5 vol% VGCF was found to be three times smaller than that of Ti rolled material. These properties make the Ti/VGCF composite material suitable as a separator material.

Fabrication of WS2-Dispersed Al Composite Material by Compression Shearing Method at Room Temperature

In this study, WS2-dispersed Al composite material was fabricated by Compression Shearing Method at Room Temperature, using various WS2 content ratios. The mechanical and friction properties of the WS2-dispersed Al composites were measured. As a result, the density measurements showed that the compacted WS2-dispersed aluminum composite had a relative density of 95 to 99%. Tensile strength of WS2-dispersed Al has 200 MPa. The friction coefficient of Al/0.5vol.%WS2 was 0.14, a reduction of 83%, in comparison with the 1.0 friction coefficient of the pure Al matrix material. The addition of WS2 to the matrix systems used reduced the friction coefficient. Therefore, WS2-dispersed Al composite material is useful for maintenance-free material of slide member.