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The authors have studied a new method of intermetallic coating using a small TIG welder. This method is based on a reaction between small liquid beads produced from very thin metal wire and the substrate metal surface. The authors designed a computer-aided 3-dimensional micro welder (3DMW) for a previous study on freeform fabrication of intermetallics, and have applied it to this study on intermetallic coating. In this study, a predetermined length of thin aluminum wire was fed onto the titanium substrate surface, and a spark was stricken from a thin electrode of a W-Ce2O3 alloy to make a small aluminum liquid bead on the titanium substrate surface and to simultaneously melt a small area of the substrate surface beneath the liquid bead. All process conditions had been programmed beforehand, including the length of the wire feeding per spark, the position of the electrode, electric power, movement of the stage holding the substrate, etc. The liquid bead containing aluminum and titanium rapidly solidified on the titanium substrate surface producing titanium aluminides on it. Repetition of the aluminum wire feeding, the electrode positioning and the spark striking produced a coating layer consisting of sub-layers of TiAl3, TiAl and Ti3Al from the surface side to the substrate side. Vickers hardness and wear resistance of the coated sample were remarkably improved.

A newly developed freeform fabrication process named 3D Micro-Welding, which is a combined system of a micro-TIG welding and a layered manufacturing method, is demonstrated. Various refractory alloys such as Inconel, stainless steel, and Invar can be freeformed besides elemental metals like titanium. Small metal beads of ~1mm in diameter are formed by emitting micro arc to the top of a thin metal wire of 0.2mm diameter. A fused bead is welded to a metal substrate or previously formed beads. By continuing this process and building up beads layer by layer under the control of CAD/CAM system, 3D objects were produced. In this study, optimization of micro-welding parameters such as the waveform of pulsed arc current and electrode materials were investigated and simple 3D objects of Inconel 600, SUS 304, Invar 42 were formed. The interfaces between adjacent beads were joined well and no crack or pore existed in the formed objects. The density and Vickers hardness of Inconel 600 objects showed comparable values to the commercial Inconel alloy, however the yield strength and Young’s modulus was about 80% and 70% of that alloy, respectively.

Functionally structured material is a tailored material to have unique geometric structures and create new functions or high performances. Design and fabrication of 3D ceramic photonic crystals and fractals using CAD/CAM stereolithography are demonstrated as well as their unique functions of reflection and localization of electromagnetic waves as typical examples of functionally structured materials. The outlook of functionally structured materials is briefly discussed.

The three-dimensional (3D) photonic band gap material is a material that there exists a full photonic band gap in which waves are forbidden to propagate whatever the polarization or the direction of propagation. In order to obtain photonic bandgap in lower range, we focus on the fabrication of PBG materials of diamond structure with TiO2 powder mixed with SiO2. The inverse epoxy structure with periodic diamond lattices in millimeter order has been fabricated by stereolithographic rapid prototyping. TiO2 slurry was filled into the epoxy structure and then cold isostatic pressing was applied. After sintering at 700K for 5hrs, the epoxy was burnt out and the designed structure was maintained perfectly. The calculated band diagram shows that there exists an absolute photonic band gap for all wave vectors. The measurement of transmission from 10 to 20 GHz in <100> direction shows that a complete band gap is formed at about 14.7-18.5 GHz. The magnitude of the maximum attenuation is as large as 30 dB at 17 GHz.

Three-dimensional electromagnetic or photonic crystals with periodic variations of the dielectric constants were fabricated by using a rapid prototyping method called stereolithography. Millimeter-order epoxy lattices with a diamond structure were designed to reflect electromagnetic waves by forming an electromagnetic band gap in GHz range. Titania based ceramic particles were dispersed into the lattice to control the dielectric constant. The diamond lattice structures formed the perfect band gap reflecting electromagnetic waves for all directions. The location of the band gap agreed with the band calculation using the plane wave propagation method. The diamond structures with graded lattice spacing were successfully fabricated as well, resulting in the directional transmission of microwaves. The stretching ratio of the lattice spacing in the crystal structure was changed according to the electromagnetic band calculation. A microwave antenna head composed of the diamond structure with graded lattice spacing was fabricated which achieved the unidirectional transmission.

Three-dimensional electromagnetic or photonic crystals with periodic variations of the dielectric constants were fabricated by using a rapid prototyping method called stereolithography. Millimeter-order epoxy lattices with a diamond structure were designed to reflect electromagnetic waves by forming an electromagnetic band gap in GHz range. Titania based ceramic particles were dispersed into the lattice to control the dielectric constant. The diamond lattice structures formed the perfect band gap reflecting electromagnetic waves for all directions. The location of the band gap agreed with the band calculation using the plane wave propagation method. The diamond structures with graded lattice spacing were successfully fabricated as well, resulting in the directional transmission of microwaves. The stretching ratio of the lattice spacing in the crystal structure was changed according to the electromagnetic band calculation. A microwave antenna head composed of the diamond structure with graded lattice spacing was fabricated which achieved the unidirectional transmission.

Diastrophic dysplasia sulfate transporter (DTDST) is a sulfate transporter required for the synthesis of sulfated proteoglycans in the cartilage. Over 30 mutations have been described in the DTDST gene, which result in a continuous clinical spectrum of recessively inherited chondrodysplasias, including, in order of increasing severity, a recessive form of multiple epiphyseal dysplasia (rMED), diastrophic dysplasia (DTD), atelosteogenesis type II (AO‐II) and achondrogenesis 1B (ACG‐1B). Correlation between disease severity and residual sulfate transport activity has been reported. Here we report a patient with DTDST mutations, whose manifestations fell in a range between AO‐II and DTD. The patient was a compound heterozygote for the recurrent c.835C>T (p.R279W) and novel c.1987G>A (p.G663R) mutations. Immunocytochemical analysis in HEK293 cells showed that the p.G663R mutation was localized within the cytoplasm, and not to the cell membrane, suggesting p.G663R is a loss‐of‐function mutation. Our case supports the previously described correlation between the severity of the phenotype and the putative level of residual transport function. © 2006 Wiley‐Liss, Inc.

Menger-sponge is a three dimensional fractal structure with self-similar patterns. We fabricated the Menger-sponge structure composed of epoxy with titania-based ceramic particles dispersion by using a stereolithography CAD/CAM system. It has a cubic body of 27 mm in edge size with square through holes of 1, 3 and 9 mm. The structure is characterized with a fractal dimension D = 2.73 and a fractal stage 3. The electromagnetic wave response of the Menger-sponge was measured by using a network analyzer. Both reflection and transmission amplitudes of incident waves showed remarkable attenuations to -50 dB at 8 GHz simultaneously. The electric field intensity in the center holes in the Menger-sponge was measured by using a mono-pole antenna. The electromagnetic energy was localized in the central air cavity by forming the strong localization mode. The localized mode frequency can be controlled by changing the structure size, number of stage, and the effective dielectric constant. We call such fractal structures as the photonic fractal.

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Localization or confinement of electromagnetic or optical waves is reviewed briefly in respect to the wave interaction with the specific structures of periodic, random, and fractal (self-similar) geometries, which can enhance strong interference, scattering, and resonance of waves. The localization of microwave in photonic crystals with diamond structure and in photonic fractals with Menger sponge structure of dielectric media is reported and discussed about the difference of localization behaviors. These 3D structures are fabricated easily from liquid photosensitive resins or ceramic dispersed ones by a CAD/CAM stereolithography. The localization in photonic fractals is supported with several measurements of transmission, 90° wave scattering, electric field intensity profile, and FDTD (finite-difference time-domain) simulation for localized modes. An empirical equation to predict the localization frequencies shows good agreements with measured results as well. The localization in a photonic crystal can be explained by Bragg scattering, while that in a photonic fractal by resonance in the fractal cavity.

An entirely new functional material named photonic fractal has been developed. It can strongly localize electromagnetic waves in a dielectric fractal cube called Menger sponge without reflection and transmission. The wavelength and frequency of the localized mode can be predicted using a simple equation associated with the fractal geometry and the spatially averaged dielectric constant of the Menger sponge structure. A wide variety of applications to communication, information, energy, sensing, medical care, and other fields are considered. Design and fabrication of Menger sponge fractals with epoxy resin and ceramics, their electromagnetic wave responses, integration of photonic fractals as well as potential applications are reported.

When a surface of a titanium disk was melted in an atmosphere of pure nitrogen using a 3D Micro Welder which was designed by the present authors, the surface was nitrided to a depth of 90 to 260μm depending on the arc current of 6 to 24 A. The concentration of nitrogen in the nitrided layer was approximately 50 mol% at the surface, and the concentration decreased as the distance from the surface increased. A TiN layer was formed at the surface, and beneath the TiN layer, a dual phase layer of TiN and α-Ti was formed. Vickers hardness was approximately 1800 in the TiN layer and it varied from 900 to 200 in the dual phase layer as the distance from the surface increased.

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Abstract: Interdiffusion of copper and zinc alloys of Cu-28.5 at. pct Zn and Cu-4.9 at. pct Zn has been investigated under pressures from 0.101 to 3240 MPa in the temperature range from 1256 to 1377 K. The diffusion coefficients decrease with increasing pressure. The activation energy for impurity diffusion of zinc in copper increases with pressure. The ratio of the activation volume to the molar volume of copper is between 0.75 and 0.90. It is concluded that the impurity diffusion of zinc in copper occurs predominantly by the monovacancy mechanism at temperatures near the melting point of the alloy.

Abstract: The isobaric sections of the aluminium phase field in the Al-Ge system have been obtained experimentally at 0.1 MPa, 2.2 and 2.6 GPa. The solidus and solid solubility lines of the aluminium phase were determined by electron probe microanalysis of alloys quenched after equilibration at known temperatures and pressures. The aluminium phase field of aluminium was observed to expand with increasing pressure. This result was compared with the phase diagrams calculated on the basis of thermodynamic and volumetric data at 0.1 MPa. The calculations are in qualitative agreement with the experimental results.

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The influence of SiO2addition on the densification and microstructural development of high‐purity Si3N4during hot isostatic pressing (HIP) was studied. During HIP, densification was promoted, but the phase transformation from α‐Si3N4to β‐Si3N4was impeded by SiO2. Analysis using a simple model shows that the enhanced densification was mainly due to the viscous flow of SiO2. The microstructure changed remarkably at between 10 and 20 wt% SiO2additions. Analysis of the phase transformation kinetics suggests that the diffusion of Si3N4through SiO2glass is the ratecontrolling step for the transformation.

The role of high‐purity silica in the fracture of Si3N4at high temperatures has been investigated. The flexural strength at 1400°C was found to be greater than that at room temperature. Little plastic deformation was observed even when 10 wt% SiO2was added and the strain rate was decreased 2 orders of magnitude from that for a standard bend test. Microstructural observations revealed that the glassy phase was localized at intergranular pockets when SiO2additions were ≤ 10 wt%. High strength at 1400°C despite the presence of a fairly large amount of glassy phase is attributed to a high cavitation threshold in such glassy pockets consisting of high‐purity SiO2. However, the deformation behavior changed abruptly for SiO2additions of 10 and 20 wt%, which is explained by the morphological change of the glassy phase to thicker intergranular layers which allow macroscopic viscous flow.

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The impurity diffusion coefficients of Zr in β-Ti have been determined at temperatures from 1173 to 1773 K under pressures of 0.1 MPa and 1.0, 2.1, and 3.0 GPa using Ti/Ti-3.06 at. pct Zr diffusion couples. The Arrhenius plots of the diffusion coefficients exhibit strong curvature, and their degree becomes larger with increasing pressure. The activation volumes, ΔV, evaluated from the isothermal pressure dependence of the diffusion coefficient are 0.22 to 0.36 Ω, where Ω is the atomic volume of the host metal. The values of ΔV/Ω are very close to the ratio of 0.33 for self-diffusion in β-Ti reported by Jeffery and the ratios of 0.28 to 0.41 for W and Sn diffusion in β Ti reported by Arakiet al., whereas they are considerably smaller than that normally expected for diffusion in bcc metalsvia“simple” monovacancy mechanism. The increase in degree of curvature in the Arrhenius plot by pressure and the small values of ΔV/Ω can be interpreted in terms of the model of phonon-assisted diffusion jumpsviamonovacancies.

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Purpose: There are concerns that malalignment in total knee arthroplasty (TKA) occurs with less experienced surgeons. This study investigates the influence of surgical experience on TKA outcomes. Materials and methods: Nineteen patients (38 knees) who underwent bilateral TKA between 2011 and 2015 were included. A supervisor performed knee replacements associated with lower Knee Society Scores (KSS); trainee surgeons operated on the other knee. Knees were categorized into two groups: operations by the supervisor (group S) versus operations by trainee surgeons (group T). Range of motion (ROM), KSS, operative time, hip–knee–ankle angle, and femoral and tibial component angle were evaluated. Results: The mean operative time was 92.5 min in group S and 124.2 min in group T (p&lt; 0.01). The mean postoperative maximal flexion was 113.2° in group S and 114.2° in group T (not significant). The mean postoperative KSS was 92.9 in group S and 93.9 in group T (not significant). No significant differences between groups in terms of proportion of inliers for the hip–knee–ankle angle, femoral component angle, or tibial component angle were observed. Conclusions: Although operative time was significantly longer for trainee surgeons versus the supervisor, no significant differences in ROM, KSS, or component positioning between supervisor and trainee surgeons were observed. Level of evidence: IV (retrospective case series design).

NiAl/10‐mol%‐ZrO2(3Y) composites of almost full density have been fabricated via spark plasma sintering (SPS) for 10 min at 1300°C and 30 MPa. The former intermetallic compound, which contains a trace amount of Al2O3, has been prepared via self‐propagating high‐temperature synthesis. The composite microstructures are such that tetragonal ZrO2(∼0.2 μm) and Al2O3(∼0.5 μm) particles are located at the grain boundaries of the NiAl (∼46 μm) matrix. Improved mechanical properties are obtained: the fracture toughness and bending strength are 8.8 MPa·m1/2and 1045 MPa, respectively, and high strength (>800 MPa) can be retained up to 800°C.

Perovskite‐type (La1‐xSrx)MnO3(0 x0.3) was synthesized through the sol–gel process at low temperature (400° to 500°C). Poly(acrylic acid) (PAA) was used to make a gel from an aqueous solution of lanthanum, strontium, and manganese nitrates. The particle‐diameter distribution of the manganites had a maximum value of 0.3 to 0.7 μm, and a specific surface area of about 17.5 to 23.5 m2/g.

Pure b-sialon powders with the controlled z values (z = 2[?] 4) were successfully prepared from stoichiometric mixtures of constituent elements (Si, Al and SiO2) under a nitrogen pressure of 1 MPa by the combustion synthesis (CS) method. The raw materials were combusted with different ratios of a commercial sialon powder of z = 1 as a diluent (0, 10, 20, 30, 40, 50 wt %). Without diluent, the reactions temperatures were very high (> 2000 degC) and the product contained metal Si residue besides Sialon products. The combustion temperatures of nitridation reactions were controlled by using Sialon (z = 1) as a diluent. The combustion reactions completed at 50 wt% dilution, and pure b-sialon phases were synthesized. However, the individual peaks of b-Sialon (z = 1) diluent were also detected. Single-phase b-sialon powders were obtained by using the products as diluents and repeating the combustion for few times.

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