Hideshi Miura

High Performance Titanium Alloy Compacts by Advanced Powder Processing Techniques

In this paper, two kinds of advanced powder processing techniques such as Metal Injection Molding (MIM) and Direct Laser Forming (DLF) were introduced to fabricate complex shaped Ti alloy parts which have been widely used for various industrial and medical applications because of their excellent characteristics of low density, high corrosion resistance and high biocompatibility but need high processing cost because of poor workability. The MIM process has been tried to strengthen Ti-6Al-4V alloy compacts by addition of fine Mo, Fe and Cr powders, and enhanced tensile strength of 1030 MPa with 15.1 % elongation was obtained by an addition of 4 mass%Cr because of the microstructural modification but also the solution strengthening in beta phase. DLF process has been tried to improve the honeycomb porous structure from Ti-6Al-7Nb powder material, and the honeycomb structure with 300 m holes showed good mechanical compatibility and superb biocompatibility in osteoblasts culturing.

Development of improved solid oxide fuel cell electrolyte sheet by microimprinting for layered material

At present, the solid oxide fuel cell (SOFC) is attracting much attention because it possesses the highest power generation efficiency among many types of fuel cell, and SOFC emits only water that does not harm the environment. Recently, the electrolyte structure for SOFC has been processed into various forms to increase the efficiency of SOFC. In this work, we tried to improve the performance of SOFC by changing the mesostructure on the interfaces between the electrolyte and electrodes. This hundred-micrometer-scaled mesostructure has been proposed to increase the reaction on the interfaces. However, there has been no effective method of fabricating the cells with the microstructure along the interfaces. We have already proposed the micro powder imprint (?PI) method to create fine patterns on ceramic samples. In this study, the ?PI method for layered material was newly developed to fabricate the micropatterns on both sides of an electrolyte sheet. The optimization of process parameters, such as compounding ratio, debinding temperature, and sintering temperature, was examined to obtain desired wavy patterns on both surfaces of the electrolyte sheet.

Fabrication of Ti-6Al-7Nb Alloys by Metal Injection Molding

The metal injection molding process was applied to produce Ti-6Al-7Nb alloys using 3 types of mixed powders. The first is a mixture of Ti and Al-Nb pre-alloyed powders, the second is a mixture of Ti, Ti-Al alloy and Nb powders, and the third is a mixture of elemental powders of Ti, Al and Nb. The sintered compacts using the first and second powders showed higher density and mechanical properties than the compacts using the third powder which showed many large pores formed due to the dissolution of Al particles during the sintering steps. Eventually, the compacts using a mixture of Ti+Al-Nb or Ti+Ti-Al+Nb powders showed tensile strength of above 800MPa and elongation of above 10%, which are similar to the properties of wrought materials.

Magnetic Micro Actuator Using Interactive Force between Magnetic Elements

In micro electro mechanical system (MEMS) field, there have been used many kinds of actuators. Among them, the magnetic actuator has some advantages. As magnetic micro actuators do not need electric wiring for energy supply, the structure can be simple and be downsized easily. However, the magnetic force would be very small with downsizing, which is the main problem for conventional magnetic actuators. We propose a new type actuator using magnetic interaction force between magnetic elements to solve this matter. This actuator can work even if it gets smaller, because the interaction force is dominant in a microscopic region. We fabricated the actuator by a casting process with photolithography using the SU-8 resist material. Then, the structure was fabricated by casting the mixture of poly(dimethylsiloxane) (PDMS) and a magnetic powder material. The beam type actuator works successfully and also shows interesting behavior. We can control the behavior of this actuator by changing the arrangement of magnetic elements on the structure. We also show theoretical evaluation of the deformation of the present actuator.

Effects of Resist Thickness and Viscoelasticity on the Cavity Filling Capability in Bilayer Thermal Embossing

Poly(methyl methacrylate) (PMMA) bilayer structures are employed as resists to investigate deformation of polymers by microthermal embossing. Owing to the dispersion of Fe3O4 particles in the upper layer, the distinct interface profiles of each layer resist can be observed by scanning electronic microscope (SEM). Deformation and replication fidelity are attributed to a variety of factors in the imprinting process. In particular, the thickness of each resist layer and the viscoelasticity of different molecular weight polymers play the most crucial roles among these factors. Based on experimental results, we improved the deformation models of imprinting for bilayer PMMA material and evaluated the models via specific parameters: the degree of deformation of the lower layer (DL), the fraction of cavity filling of the lower layer (FL), and variation in the fraction of the upper layer thickness (Ki). The final pattern of the upper or lower layer may be implicated in micro electro mechanical systems (MEMS).

Magneto-FEM analysis for micro actuator using array of magnetic elements

This paper reports a magnetic actuator using interaction between micro magnetic elements. It was already reported that the present actuator can work even if the structure was miniaturized to nano-scale. In the present work, simple fabrication process with photolithography and PDMS casting was employed to obtain beam type structures with micro array of magnetic elements on their surface. Two samples with simple grid patterns were prepared for testing. These samples had the same grid pattern but different orientation, which caused directly opposite bending deformation under the same applied magnetic field. We used magneto finite element method (FEM) to explain the behavior of the present actuators.

Laser Forming of Ti-6Al-7Nb Alloy Powder Compacts for Medical Devices

Titanium and its alloys have been widely used for medical and aerospace applications because of their excellent attributes of light metal, high strength, high corrosion resistance and high biocompatibility. Especially, Ti-6Al-7Nb alloy has been developed as a more suitable biomaterial to replace Ti-6Al-4V alloy, because vanadium is toxic element to the biological body. However, it is not easy to fabricate the complex shaped and precise parts by the conventional methods due to their poor castability and machinability. In this study, laser forming technique has been applied to solve the above problems. The precise structure was obtained by optimizing the laser forming parameters. Using this technique, a honeycomb structure was fabricated　effective to grow the neighboring tissue and also encourage osseointegration. Finally, mouse osteoblasts were cultured on the formed structures, resulted in the effectiveness of the honeycomb structure for biocompatibility.

Improvement of Solid Oxide Fuel Cell by imprinted patterns on eelectrolyte

This paper reports an improved interfacial structure between electrode and electrolyte of Solid Oxide Fuel Cell (SOFC). We employed an imprint process to give fine patterns onto a ceramic electrolyte sheet. The imprint process is a powerful tool to transcribe nano- to micro-patterns on materials. In the present work, a sheet of ceramic compound material was prepared, and micro patterns were given on the sheet. After debinding and sintering, dense ceramic sheet with fine patterns were obtained. We prepared three kinds of electrolyte sheets with different surface patterns using this technique. After applying anode and cathode layers, the three fuel cell samples were assembled to test the cell performance. It was resulted that the finer pattern caused the best performance in the three samples.

Evaluation and Analysis of Distortion of Complex Shaped Ti-6Al-4V Compacts by Metal Injection Molding Process

Titanium and its alloys have been widely used for medical and aerospace applications because of their excellent attributes of high specific strength, corrosion resistance, and biocompatibility. However, it is not easy to produce the complex shaped parts due to their poor castability and machinability. Metal injection molding (MIM) is one of suitable processing technique to produce the complex shaped parts in order to reduce the manufacturing cost. In this study, complex shaped Ti-6Al-4V compacts was prepared by MIM process for airplane application. The effects of high molecular binder content and different compact’s set-up during thermal debinding on the distortion of complex shaped compacts were measured and evaluated. The binder with 10 % APP (Atactic polypropylene) was found to have better shape retention for the parts. Furthermore the results indicate that high distortion occurs at early stage of thermal debinding process. The use of supports during thermal debinding can significantly reduce the distortion of the final parts.

Density Gradient Materials by Direct Metal Laser Sintering

The direct metal laser sintering process was applied to produce density gradient materials of stainless steel 316L. In order to understand the mechanism of forming porous structure, the influence of laser power, scan rate and scan pitch on the porosity were investigated by measuring density of produced samples and observing cross-sectional microstructures. Laser power greatly affected to the porosity by forming clusters of melted metal powders. It was found that the size change of clusters plays a role in forming porous structure. Eventually, three dimensional sample owing density gradient structures was manufactured.