bluuebunny/crossref_metadata_2025 huggingface dataset:
Evaluation of Physical Properties on Functionally Graded Piping Joints Made from Cu and Austenitic Stainless Steel Powder
Authors: Nakano K. , Anzai T. , Yamaguchi Tomiko , Nishio Kazumasa
Published: October 2009

Welding materials, that the principal chemical component is nickel, are used usually for the welding between copper and austenitic stainless steels. But many kinds of mechanical or physical properties of welds between two materials will change largely. In this study, Functionally Graded Piping Joints (FGPJ) have been manufactured as an experiment using copper and austenitic stainless steel (SUS304) powder by a process based on HIP. This composition has been confirmed by absorbed electron and characteristics X-ray images of each mixed layer for FGPJ to be uniform or continuous. The following items have been investigated and compared with the linear law of mixture rule: Vickers hardness, thermal expansion, and thermal conductivity at a one-dimensional non-steady state etc. Those physical properties have been identified to depend on the mixing ratios of copper and austenitic stainless steel (SUS304). Pretty good agreements have been obtained between the experimental data and the calculated values according to the linear law of mixture rule.
Control of the Composition Profile of Tungsten-Copper Functionally Graded Materials for Fusion Technology Application
Authors: Raharijaona Jean Joel , Missiaen Jean Michel , Mitteau Raphael , Thomazic Aurelie
Published: October 2009

This work aims to process W-Cu FGM for fusion material applications, in particular plasma facing components (PFC). Currently, PFCs are made by multi-material assembly and rely on tungsten armour tile (high heat flux side) which needs to be cooled by the attachment to a heat sink (Cu-alloys). The interfaces in multi-material assembly are unfavourable for the application (high working temperature, thermal fatigue). The use of FGM can be a new promising way. The aim of this study is to analyze the effect of a composition/grain size variation on the liquid phase migration during liquid phase sintering of FGM, in order to control the final composition profile. Bi-layer materials are processed by powder metallurgy route. W-Cu compositions with 10 and 20wt%Cu and with different W-particle sizes are processed starting with attritor-milled W-CuO powder mixtures which are reduced at 350°C. Analysis of copper liquid phase migration for different composition/grain size associations indicates that the phenomenon is driven by differential sinterability in the gradient. The copper liquid migration depends on the differences in sinterability, on the available liquid and open porosity in the structure beyond the melting point of copper. From these analyses, a way to control the gradient profile of W-Cu structure can be proposed.
Fabrication of Metal Photonic Crystals with Graded Lattice Spacing by Using Micro-Stereolithography
Authors: Sano Daisuke , Kirihara Soshu
Published: October 2009

We designed micro-scale photonic crystal with or without graded lattice spacing composed of copper to control Terahertz (THz) waves. Designed structures were fabricated by using micro-stereolithography. By proper dewaxing and sintering process, pure copper photonic crystals were obtained. Transmission properties of THz waves propagating through the photonic crystals were measured by THz time-domain spectroscopy. Measured results showed good agreements with the simulated results.
Millimeter Wave Control Using TiO2 Photonic Crystal with Diamond Structure Fabricated by Micro-Stereolithography
Authors: Kaneko Masaru , Kirihara Soshu
Published: October 2009

The diamond photonic crystals with the periodic arrangement of high dielectric constant (ε=100) were fabricated, and photonic band gap properties in the millimeter waveguides were investigated. Acrylic diamond lattice structures with TiO2 dispersion at 40 vol. % were fabricated by Micro-stereolithography. The forming accuracy was 10m. After sintering process, TiO2 diamond lattice structures are obtained. The relative density reached 96%. The millimeter wave transmittance properties were measured with network analyzer and W-band millimeter waveguide. The band gap was measured between 90 GHz and 110 GHz in the Γ-X <100> direction, which was well agreed with the results calculated by the plane wave expansion method and simulated by the Transmission Line Modeling method.
Overview of Studies on Space Solar Power Systems and Elemental Technology Development
Authors: Suzuki Hiroaki , Kisara Katsuto , Niino Masayuki , Mori Masahiro
Published: October 2009

Japan Aerospace Exploration Agency (JAXA) has studied Space Solar Power Systems (SSPS) using laser and microwave beams for years since 1998. Current SSPS study undertaken by JAXA consists of three main subjects, SSPS concepts and architectures study, technology demonstration and elemental technology development. In current research of Laser based SSPS (L-SSPS), we have studied some elemental technologies such as ultralight film mirror, wavelength selective mirror, laser generator based on direct solar pumping solid-state laser diode, laser transmission property in atmosphere, photovoltaic generation converting laser energy to electricity and photocatalytic hydrogen generation. This paper presents the introduction of SSPS concepts and architectures study and elemental technology development of L-SSPS.
Topology Optimized Design of Functionally Graded Piezoelectric Resonators with Specified Resonance Frequencies
Authors: Rubio Wilfredo Montealegre , Silva Emílio Carlos Nelli , Paulino Glaucio H.
Published: October 2009

This work explores the design of piezoelectric resonators based on functionally graded material (FGM) concept. The goal is to design single-frequency Functionally Graded Piezoelectric Resonators (FGPR) subjected to the following requirements: (i) an assurance of the specified resonance frequency, and (ii) for most acoustic wave generation applications, the FGPR is required to oscillate in the piston mode. Several approaches can be used to achieve these goals; however, a novel approach is to design the piezoelectric transducer by using Topology Optimization Method. Accordingly, in this work, the optimal material gradation of an FGPR is found, which maximizes a specified and single resonance frequency subjected to a volume constraint. To track the desirable piston mode, a mode-tracking method utilizing the modal assurance criterion (MAC) is applied. The continuous change of piezoelectric, dielectric, and elastic properties is achieved by using the graded finite element (GFE) concept, where these material properties are interpolated inside the finite element using interpolation functions. The optimization algorithm is constructed based on sequential linear programming (SLP), and the concept of the Continuum Approximation of Material Distribution (CAMD) is considered. The software is implemented in MATLAB language. In addition, to illustrate the method, a two-dimensional FGPR is designed with plane strain assumption. Performance of designed FGPR is compared with non-FGPR performance.
Anode-Supported SOFCs with Electrolyte Thin Films Prepared by Spray Coating
Authors: Ding Chang Sheng , Lin Hong Fei , Sato Kazuhisa , Tsutai Yoshifumi , Iguchi Mabito , Hashida Toshiyuki
Published: October 2009

Dense gadolinium doped ceria (GDC) electrolyte thin films were prepared on porous NiO-GDC substrates by spray coating process. Microstructure of the GDC thin films and effect of preparation process on the microstructure were examined. SEM results show that uniform and dense GDC thin films with a thickness of approximately 1 μm were successfully prepared on porous NiO-GDC anodes. Anode-supported single cell with the thin GDC electrolyte film was tested using humidified hydrogen as a fuel, and exhibited relatively high electrical performance at low operating temperature (the maximum power density of 135 mW/cm2 at 600 °C). This means that the thin GDC film may be applicable to an electrolyte for anode-supported SOFCs. The experimental results suggest that the spray coating method developed in this study may offer a useful route for preparing thin and dense electrolytes of SOFCs.
Effect of Metal Gradient In Nano Wall of Stratified Type Photocatalyst
Authors: Hayashi Tsugumi , Baba Yohei , Taga Toshiharu , Yokoyama Shun , Suzuki Hiroaki , Takahashi Hideyuki , Niino Masayuki , Tohji Kazuyuki
Published: October 2009

Objective of study was the development of core-shell type ZnS-CdS photocatalyst with the stratified morphology. To form the stratified morphology, condition of the precursor is extremely important. For this purpose, three types of precursors, thus core-shell type, egg-shell type and uniform type, was tried to synthesize by utilizing the results of the calculation. The size of the synthesized precursor particles was about 40-100 nm. Main phase of the particle was gradually changed from ZnO (pH8.0) to Cd(OH)2 (pH9.5). Detailed analysis of the synthesized precursor was clearly demonstrated that these have the crystalline structure and each metal element was co-existed in one particle. Therefore, it could be concluded that core-shell type or uniform type precursor was successfully synthesized. Core-shell type ZnS-CdS stratified photocatalyst could be successfully synthesized by sulfurization for 1h, and it shows the high photocatalytic activity under visible light irradiation.
Sedimentation Behavior of Mixed Powder Slurry under High-Speed Centrifugal Force
Authors: Suzuki Hiroyuki Y.
Published: October 2009

Compaction behavior of two component slurry during High-speed Centrifugal Compaction Process (HCP) was observed. Slight amount of iron oxide powder is mixed into alumina slurry, then the slurry was sedimented in a centrifuge under rotational speed of up to 11,500 rpm. A “Y” letter shaped flow pattern was emerged in the cross section of the compact. The pattern was clearer with higher rotational speed, but indifferent to acceleration rate of rotation. A similar pattern was simulated when we presume bidirectional initial flow in centrifugal field, which indicated that the combination of Corioli’s force and bidirectional flows of powder and dispersing medium caused such flow pattern.
Solidification Structure and Hardness Distribution in Centrifugally Cast Aluminum Alloy Duplex Pipes
Authors: Ohmi Tatsuya , Iguchi Manabu
Published: October 2009

The solidification structure and hardness distribution in aluminum alloy duplex pipes produced by a two-step centrifugal casting have been investigated. In this process, two kinds of molten metals, i.e., the first melt and the second melt with a higher liquidus temperature were cast in sequence at a given interval into a rotating mold of a centrifugal caster. An Al-12mass%Si alloy was used for the first melt, and an Al-30mass%Ni or Al-32mass%Si-0.1mass%P alloy was used for the second melt. The second melt was cast after the solidified shell of the first melt had formed. The resultant cast pipes consisted of an outer side layer and a composite layer containing fine primary crystals. The outer side layer was a portion of the solidified shell of the first melt that survived after the contact with the higher-temperature second melt. The composite layer consisted of one or two layer(s). When the volume of the remelted part of the solidified shell was large, all the second melt mixed into the first melt and the resulted mixed melt formed the composite layer. On the other hand, the composite layer formed only from the second melt when the temperature of the solidified shell was low. In the intermediate case, the composite layer consisted of these two types of the layers.
Effects of the Processing Temperature of Centrifugal Casting on the Mechanical Properties of Al-Al3Ti FGMs
Authors: El Hadad Shimaa , Sato Hisashi , Sequeira P.D. , Watanabe Yoshimi , Oya-Seimiya Yoshihito
Published: October 2009

Formation of the compositional gradient in FGMs fabricated by centrifugal casting method depends mainly on the processing temperature and the applied centrifugal force. According to the initial state of the dispersed second phase at the processing temperature, CCM-FGMs can be classified into two categories. One is the FGM fabricated by centrifugal solid-particle method, and the other one is the FGM made by centrifugal in-situ method. In previous study, it has been reported that microstructure of Al-Al3Ti FGMs by centrifugal in-situ method was different from that by centrifugal solid-particle method. However, difference of mechanical property due to processing method is still unclear. In this study, mechanical properties, such as hardness and wear property of Al-Al3Ti FGMs fabricated by centrifugal solid-particle method and in-situ method were evaluated.
Investigation of the Mechanical Properties in Al/Al3Zr FGMs Fabricated by Centrifugal Casting Method
Authors: El Hadad Shimaa , Sato Hisashi , Watanabe Yoshimi
Published: October 2009

Al-5mass%Zr FGMs fabricated by centrifugal casting method (CCM) have a very interesting microstructure. Since the intermetallics compounds of Al3Zr are plate in shape, Al3Zr platelet particles are almost oriented normal to the applied centrifugal-force direction. Considering this microstructure, the mechanical properties of Al/Al3Zr FGMs would vary for the same sample depending on the particles orientation and their volume fraction in the tested position. In this study, some mechanical properties of Al/Al3Zr FGMs were investigated. Al/Al3Zr FGMs rings were produced by CCM, under applied centrifugal force of 30, 60 and 120G (units of gravity). Microstructural observation along the centrifugal force direction was carried out. The platelet Al3Zr particles were almost oriented normal to the applied centrifugal force direction. The volume-fraction of Al3Zr particles increases close to the ring surface. Moreover, this distribution range of Al3Zr particles becomes broader with decreasing the applied centrifugal force. The same distribution trends were also observed for the hardness values. The Compression tests were also performed for further investigation of the mechanical properties. Samples under G=30 showed the lowest the 0.2%proof stress while those cast under G=120 had the highest 0.2% proof stress.
Multi-Scale Phase Field Simulation of Disorder-Order Transition, Combined with Cluster Variation and Path Probability Methods
Authors: Ohno Munekazu , Chen Ying , Mohri Tetsuo
Published: October 2009

Multi-scale simulation of ordering process from electronic, atomistic scales to microstructural scale was carried out by hybridizing Phase Field Method (PFM) and Cluster Variation Method (CVM). The hybrid model was applied to disorder-L10 ordering process in Fe-Pd system. Furthermore, computation of relaxation constants in the PFM was attempted based on Path Probability Method (PPM) which is the time evolution version of the CVM, within a linearized analysis of order-order relaxation process.
Hydroxyapatite Coating on Ti-6Al-4V Alloy by an Electrolytic Process and with Heat-Treatment
Authors: Wang Cheng Li , Shih Wei Jen , Wang Szu Hao , Chang Kuo Ming , Li Wang Long , Hon Min Hsiung , Wang Moo Chin
Published: October 2009

The effect of the heat-treatment on the calcium phosphate deposited on Ti-6Al-4V substrate by an electrolytic process has been investigated. The calcium phosphate were deposited in a 0.04M Ca(H2PO4)2･H2O (MCPM) solution on Ti-6Al-4V substrate at 60 °C, 10V and 80 Torr for 1h, and calcined at different temperature for 4h. X-ray diffraction (XRD) and scanning electron microscopy (SEM) were used to characterized the deposited samples. The XRD pattern of as-deposited sample contain the phase of dicalcium phosphate (DCPD) and HAP. When calcined at 400 °C for 4 h, the DCPD phase is vanished and HAP becomes the major phase. The XRD pattern reveals that the intensity of HAP and Ca2P2O7 (CPP) decreases, but the β-TCP, CaO and rutile TiO2 also shows up.
Mechanical Properties of ZrO2 (Y2O3)-Al2O3 Nanocomposites with Addition of Hydroxyapatite Prepared by Spark Plasma Sintering
Authors: Li Shu Feng , Izui Hiroshi , Okano Michiharu , Zhang Wei Hua , Watanabe Taku
Published: October 2009

TZP-3Y20A/HA composites with addition of different volume fraction of hydroxyapatite (HA) were fabricated successfully using spark plasma sintering (SPS). The densification behavior and mechanical properties of composites are investigated as a function of sintering temperature and HA content respectively. The density of TZP-3Y20A composite increases steadily with temperature and a maximum value of 97.8% is obtained after sintering at 1400°C. Sintering the TZP-3Y20A/HA composites at 1400°C led to the decomposition of HA in the samples. Flexural strength, fracture toughness and Vickers hardness values increase with increasing sintering temperature, show decrease trend with increasing of HA content at the same temperature. They compared well with densities obtained at different sintering temperature. The maximum flexural strength, fracture toughness and Vickers hardness of 967.1 MPa, 5.27 MPam1/2 and 13.26 GPa were achieved for TZP-3Y20A composite respectively. Flexural strength, fracture toughness and Vickers hardness values of TZP-3Y20A/HA composite fell within the value range of dense HA and of TZP-3Y20A composite.
Preparation of W/Cu Functionally Graded Material
Authors: Wang Chuan Bin , Zeng Hao , Chen Y.G. , Shen Qiang , Zhang Lian Meng
Published: October 2009

A W/Cu system functionally graded material (FGM), which may be used as plasma facing component for fusion reactors, was prepared by inserting W-Cu layers with gradient composition between tungsten and copper alloy plates. W-Cu gradient layers were hot-press sintered from W-Cu powder mixtures added with zinc powder as the sintering aid, whose relative density increased with sintering temperature, reaching a value higher than 96% at 850°C. XRD and SEM measurements showed that the sintered W-Cu gradient layers were the mechanical mixtures of W and Cu. A wholly dense W/Cu system FGM was then obtained at 850°C by hot-press, whose composition and structure changed gradually. The finite element method (FEM) calculation showed that the residual stresses in the W/Cu FGM were effectively reduced as compared with the directly-bonded W/Cu joint.
Thermal Shock Behavior of Calcia Stabilized Zirconia Ceramics with Porosity Gradient Structure
Authors: Shen Qiang , Chen Chang Lian , Chen Fei , Liu Qi Wen , Zhang Lian Meng
Published: October 2009

Porous calcia stabilized zirconia ceramics (CSZC) with closed pores were presurelessly sintered by adding different contents of zirconia hollow balls. CSZC FGM with porosity gradient structure was then fabricated by laminating five layers with designed contents of zirconia hollow balls. The porosity, microstructure, and bending strength of the obtained CSZC samples were characterized. The results show that the hollow balls distribute uniformly and are well bonded with the matrix, and the porous structure is mainly composed of closed pores. The porosity of the CSZC increases linearly from 5.7 % to 31.6 % when the content of zirconia hollow balls increases from 0 % to 30 %, and the bending strength decreases rapidly from 297 MPa to 30 MPa. The thermal shock behavior of the CSZC and FGM was evaluated using air-quenching technique. It is shown that the residual bending strength of the quenched samples increases after several quenching cycles, and the samples are damaged by thermal shock after eight thermal cycles because of the production of monoclinic zirconia. FGM samples with porosity gradient structure can endure above twelve thermal shock cycles and exhibits better thermal shock resistance.
Fabrication of Al-Based FGM Containing TiO2 Nano-Particles by a Centrifugal Mixed-Powder Method
Authors: Inaguma Yoshifumi , Sato Hisashi , Watanabe Yoshimi
Published: October 2009

Centrifugal method is often applied as the fabrication process of Functionally Graded Materials (FGMs). This is because that this processing method can fabricate FGMs with large size, easily. However, this processing method has a serious problem, namely it is difficult to disperse particles with small size and low wet ability with matrix. Many of powders with nano or very fine particle size often have attractive attention as functional materials. Therefore the above problem of the centrifugal method should be improved. In this study, we proposed a centrifugal mixed-powder method as novel processing technique for the fabrication of FGM containing nano-particle. On first of this processing, powder mixture of functional nano-particle and matrix material is inserted into rotating mold. After that, matrix ingot is melted in crucible and then the molten matrix is poured into the rotating mold with powder mixture, and then, powder of matrix material will be melted by the heat from molten matrix poured from crucible. Finally, an FGM ring with functional nano-particles distributed on its surface can be obtained. Using this processing method, Al-based FGM containing TiO2 nano-particles on its surface could be fabricated. TiO2 particle has approximately 500nm in diameter. From microstructural observation, it was found that TiO2 particles were successfully distributed on surface of FGM ring. Also, hardness on the surface of the FGM ring was higher than that on inner part due to the dispersion hardening.
Effect of Casting Condition on Density and Hardness Gradients of Al-Al2Cu Alloy FGM Fabricated by Centrifugal In Situ Method
Authors: Tabushi Kenichi , Sato Hisashi , Watanabe Yoshimi
Published: October 2009

Functionally graded material (FGM) is a combined material that has a component gradient from one material at one surface to another material at the opposite surface. 　As one of the fabrication processes of FGM, centrifugal in-situ method has been proposed. Centrifugal in-situ method is a casting that centrifugal force is applied during solidification to both the primary crystal and the matrix. In a previous study, the density and hardness gradients of Al-3mass%Cu FGM ring fabricated by centrifugal in-situ method have been investigated. According to the study, Cu concentration within the FGM ring monolithically increases towards the ring's inner position, and its density also increases toward inner region. This is because the density of the primary -Al crystal is larger than that of the molten Al-Cu alloy in the early stage of solidification. Based on this solidification process, it is considered that the casting condition and the initial Cu concentration of Al-Cu master alloy affect on the density and hardness gradients in the Al-Cu FGM ring. In this study, effects of the casting condition on the density and hardness gradients of Al-Al2Cu FGM rings fabricated by the centrifugal in-situ method were investigated. It was found that density gradient of the Al-Al2Cu FGM rings increases with increasing Cu concentration of Al-Cu master alloys. Also, processing temperature for Al-Cu master alloy can control density gradient of Al-Al2Cu FGM rings. These phenomena were explained by variation of the densities of primary -Al and the molten Al matrix during the solidification.
Development of Compositional Gradient Simulation for Centrifugal Slurry-Pouring Methods
Authors: Kinoshita Keisuke , Sato Hisashi , Watanabe Yoshimi
Published: October 2009

Centrifugal slurry-pouring method has been proposed to fabricate the functionally graded materials (FGMs) with large compositional gradient. This processing method uses the two types of slurries (slurry 1 and slurry 2). The prepared slurry 1 containing one component, particle A, is firstly poured into the mold under the centrifugal force and then the slurry 2 containing two components, particle A and particle B, is poured into the mold. By this process, green body with gradient composition can be obtained and then green body will be sintered by Spark Plasma Sintering method. Finally, it is expected that FGM with gradient from 100% component A at one surface to 100% B at other surface can be fabricated. In this study, the graded distributions of the particle A and particle B within the slurry 2 under the centrifugal force were simulated analyzing the movement of particles in liquid. Moreover, Ti-SiO2 FGMs were experimentally fabricated. The Ti-SiO2 FGM has large compositional gradient on one side of FGM. However, when the size of solid-particle is small, it is difficult to form large compositional gradient in the FGM. This phenomenon obtained by experiment is in agreement with the calculated results. From this result, it is found that the centrifugal slurry-pouring method using different slurries is effective fabrication method for FGMs with large compositional gradient.
Preparation of Tungsten-Epoxy Composites and FGMs with Density Gradient
Authors: Zhang Lian Meng , Gao Ming , Luo Guo Qiang , Chen Zhuo , Shen Qiang
Published: October 2009

FGMs with density gradient are of great interest in field of dynamic high-pressure physics. In this paper, tungsten particles reinforced epoxy resin composites, and FGMs with density gradient were prepared by calendering technique. Microstructures of tungsten-epoxy composites with various tungsten contents were analyzed, and the density distribution of the FGMs was characterized. The results show that the distribution of tungsten particles in tungsten-epoxy composites is homogeneous, and the combination of tungsten particles with epoxy matrix is good. The density of tungsten-epoxy composites varies from 1.26gcm-3 to 4.0gcm-3, and the thickness of each layer is about 200μm. Tungsten-epoxy FGMs with density gradient were obtained by laminating thin layers of tungsten-epoxy composites with different tungsten contents. The highly enough bonding strength between these transition layers and good parallelism were achieved. The density distribution of the tungsten-epoxy FGMs can meet the demand of the power function equation of density and thickness.
A Trial of FGM Bearings with Solid Lubricant
Authors: Hashimoto Takashi , Kohri Hitoshi , Yumoto Atsushi , Shiota Ichiro
Published: October 2009

It is difficult to use an ordinary plain bearing under a high load or at a high friction speed because lubricant oil is pushed out from the friction surface or deterioration of the lubricant oil is caused by heat of friction. A solid lubricant, MoS2, is promising in such condition. When the lubricant is dispersed in a matrix, the solid lubricant is always supplied from the matrix. Such a composite bearing needs a back metal to maintain its shape. The heat of friction may cause a crack between the bearing and the back metal due to thermal stress. A bearing with low coefficient of friction is necessary to decrease the heat of friction, and an FGM structure is also promising to decrease the stress. The aim of this experiment is to fabricate and to examine friction properties of the composites. Cu was plated on the lubricant particles by electroless deposition. The lubricant volume fraction (hereafter Vf) was up to Vf 30 %. The Cu plated lubricant particles were hot-pressed to form a composite at 873 K under 30 MPa in a vacuum. Friction properties of the composites were determined by using a ball-on-disk type testing machine. The test was performed in the air without oil at room temperature. The solid lubricant in the composites was effective to decrease the coefficients of friction under a high load when the Vf was higher than 20 %.
Synthesis of Porous Silicon Nitride Ceramic with a Compositional Gradient
Authors: Knoll M. , Willert-Porada Monika
Published: October 2009

This paper summarises results of a study on graded surface layer composition in porous silicon nitride ceramics with a nominal Yb-silicate, Yb2SiO5-additive content of 3.2 mol%, corresponding to 10wt%. A compositional gradient of the additive is formed within the sintered part, depending upon the sintering conditions. The thickness and the phase content of the compositional gradient is significantly affected by the nitrogen activity of the sintering atmosphere. When argon gas is used during heating up and replaced by nitrogen upon soaking, the surface of the sintered ceramic is free of Yb2SiO5, whereas in N2-atmosphere a silicate-rich coating is found as surface layer of the porous silicon nitride ceramic. In presence of carbon and nitrogen, the surface is covered by SiC. In particular the Yb-silicate enriched surface layer can be used as base for an Environmental Barrier Coating, EBC, to protect the interior of the ceramic from hot gas corrosion.
Crossover from Metallic to Semiconducting in Pb2-xLnxRu2O7-δ (Ln = Eu, Sm) Compounds with Pyrochlore Structure
Authors: Masaki Kato , Imamaura Tetsuya , Fukatsu Miho , Ken Hirota
Published: October 2009

We study the synthesis and physical properties of Pb2-xLnxRu2O7- (Ln = Sm, Eu) compounds with pyrochlore structure. The lead-lanthanoid pyrochlores Pb2-xLnxRu2O7- (Ln = Sm, Eu) have been successfully synthesized by the solid-state reaction. All samples were characterized by X-ray diffraction, magnetic susceptibility, and electrical resistivity measurements. Magnetic susceptibility measurements showed that the spin-glass transition temperature, TSG, decreases with Ln content x and goes to zero at x = 0.2 and 0.6 for Sm and Eu, respectively. From electric resistivity measurements, a crossover from metallic to semiconducting behavior was observed in the range of 0.2 ≤ x ≤ 0.4 and 0.4 ≤ x ≤ 0.8 in Pb2-xSmxRu2O7- and Pb2-xEuxRu2O7-, respectively. These boundaries between metallic and insulating phases mostly correspond to values of x with TSG = 0. These metal-insulator transitions can be caused by the strongly correlated couplings between the itinerant 4d electrons which are possibly attributed to the magnetic frustration.
Ca3Co2O6 for High Temperature Side of Thermoelectric FGM
Authors: Uesugi Takeo , Kohri Hitoshi , Shiota Ichiro , Kato Masahiko , Ohsugi Isao J.
Published: October 2009

In modern age, much thermal energy is emitted from ceramic and/or steel industries. Their temperature range is between 500 K and 1300 K. Thermoelectric materials are promising to utilize the waste heat, because of no CO2 emission and long life due to no moving parts.
The thermoelectric properties of every thermoelectric material have temperature dependence and high performance appears at a specific temperature range. If the proper materials are placed and joined along the temperature gradient to form an FGM, the performance should be higher than a monolithic material.
The performance of a thermoelectric material is expressed by the dimensionless figure of merit ZT=α2ρ-1κ -1T, where α is the Seebeck coefficient, ρ is the electrical resistivity, κ is the thermal conductivity, and T is absolute temperature.
Thermoelectric oxides are suitable for high temperature materials because of chemical stability. NaxCoO2 shows relatively high ZT value in thermoelectric oxide at the temperature range below 800 K. Ca3Co4O9 shows ZT ~1 at 1000 K. Recently, it is reported that Ca3Co2O6 that is formed by decomposition of Ca3Co4O9 at 1173 K has high performance at 1300 K. The properties and fabrication condition of high density Ca3Co2O6 are, however, not reported in detail. In order to improve the thermoelectric properties and to shift the temperature range for Ca3Co2O6, we investigated the effects of element substitution.
In this experiment, the sintered Ca3Co2-xMxO6 (x=0 or 0.2, M= Mn, Mo or V) were prepared by solid-state reaction or hot pressing. Relative density of Ca3Co2O6 by hot-pressing (HP) was over 94% which is larger than one of Ca3Co2O6 by solid-state reaction (SSR). The resistivity of Mo- or V-substituted Ca3Co2O6 (HP-Mo or HP-V) were lower than one of non-substituted Ca3Co2O6 (HP). The resistivity of Mo-substituted Ca3Co2O6 (HP-Mo) showed the lowest value of 4.3×10-2 Ωcm in all specimens at 1181 K. The power factor α2ρ-1 of Ca3Co2O6 (HP-Mo) was 64.2 Wm-1K-2, which is the largest of all specimens at 1178 K, and this value is approximately 1.3 times higher than 48.8 Wm-1K-2 for Ca3Co2O6 (HP).
Characterization of Manganese Oxide-Enriched Surface Layers of Fe-Mn Alloys
Authors: Shinoda Kozo , Yamamoto Takamichi , Suzuki Shigeru , Uruga Tomoya , Tanida Hajime , Toyokawa Hidenori , Terada Yasuko , Takagaki Yasufumi
Published: October 2009

Alloying elements are added to steel for improving surface properties such as corrosion resistance. The alloying elements exhibit different chemical characters, and they are often enriched to the surface of the alloys during annealing at high temperatures. In this study, depth-resolved X-ray absorption spectroscopy (XAS) measurements were carried out using a two-dimensional detector with geometrical arrangement of grazing exit in detection of fluorescence X-ray emitted from sample surface, in order to characterize the enrichment and oxidation of manganese on the surface layers of an Fe-Mn alloy annealed under low oxygen partial pressure. This technique facilitates non-destructive measurement for characterizing the compositional distribution of manganese in the depth direction. The results showed that manganese was enriched to surface layers of the Fe-Mn alloys during annealing at high temperatures and formed as manganese oxide. The preferential oxidation of manganese by annealing under low oxygen partial pressure is considered the driving force for their enrichment on the alloy surface.
Alloy Compositional Gradation in Surface Layer and Oxidation Resistance on Chemical Synthesized FeCo Nanoparticles
Authors: Chon G.B. , Kodama D. , Shinoda Kozo , Suzuki Shigeru , Jeyadevan Balachamdran
Published: October 2009

X-ray photoelectron spectroscopy (XPS) has been used for analyzing the surface composition of polyol process-derived Fe30Co70, Fe50Co50, and Fe70Co30 alloy nanoparticles with diameters 50, 100 and 150 nm, respectively. These Fe-Co alloy particles have high oxidation resistance in the atmospheric environment even though their particle size is so small. The XPS results revealed that the concentration of iron at the surface of the as-synthesized Fe-Co alloy nanoparticles was lower than that in bulk and increased with increasing bulk cobalt composition, although the surface of nanoparticles was covered with native oxide layer formed during their exposure to atmosphere. This low concentration of iron and very thin oxide layer at the surface are considered to protect the particle from oxidation. The concentration of iron at the surface of Fe70Co30 nanoparticles increased when they were annealed at 573 K in N2 and H2 atmosphere. The results indicate that nonuniformity of the chemical composition between particle surface and core occurs during the formation of the same in polyol, and atomic diffusion at the surface of particle can occur even at relatively low temperature. The above is considered to arise from the difference in the chemical characteristics of iron and cobalt during co-precipitation in the polyol.
The Sensitivity of Strain Rate and Size Effect with Different Particle Volume Fraction in SiCp/Al Composite
Authors: Cao Dong Feng , Liu Li Sheng , Mei Hai , Zhang Qing Jie
Published: October 2009

In this paper the sensitivity of strain rate and size effect with different particle volume fraction in SiCp/Al Composite were studied through the experiment. Specimens with 40% and 30% SiC particle volume fraction were made. There are three types of particle sizes in each volume fraction. The sensitivity of strain rate and the effect of particle size in Al matrix composites reinforced with the different volume fraction were investigated, using the split Hopkinson pressure bar and Instron5882 universal material testing machine. The surface microstructure of the specimens in each composite was examined using optical microscopy and SEM. Through the strain-stress curves, the sensitivity of strain rate can be obtained. The experimental results show that the sensitivity of strain rate increases with the increasing of particle volume fraction. At the same volume fraction, the size effect were observed obviously and higher flow stresses were obtained in the composites reinforced with small particles than that in the composite with large particles.
Mixture Screening Design to Choose Formulations for Functionally Graded Fiber Cements
Authors: Dias Cleber M.R. , Savastano Holmer , Taqueda M.E.S. , John Vanderley M.
Published: October 2009

This work employing the screening strategy to examine thirteen mix proportions of six-component fiber cement formulations composed of ordinary Portland cement, ultra-fine cement, limestone filler, silica fume, cellulose and polyvinyl alcohol fibers. The vacuum de-watering technique was applied in the production of fiber cement specimens cured for 10 days and submitted to four-point bending tests. The mechanical properties such as limit of proportionality (LOP), modulus of elasticity (MOE), modulus of rupture (MOR) and specific energy (SE) were evaluated and these properties were correlated with the raw material fractions resulting in mixture rules. Results indicate that screening can be a promising methodology with which to generate coherent fiber cement mixture rules, optimize formulations in terms of costs and performance and even facilitate the choosing of formulations for functionally graded fiber cements.
Functionally Graded Thermal Barrier Coatings with Improved Reflectivity and High-Temperature Capability
Authors: Vaßen Robert , Kassner Holger , Stuke Alexandra , Mack Daniel Emil , Jarligo Maria Ophelia D. , Stöver Detlev
Published: October 2009

Conventional thermal barrier coating (TBC) systems consist of a duplex structure with a metallic bondcoat and a ceramic, heat isolative topcoat. In modern TBCs the ceramic topcoat is further divided into layers with different functions. One example is the double layer system in which conventional yttria stabilized zirconia (YSZ) is used as bottom and new materials as pyrochlores or perovskites are used as topcoat layers. These systems demonstrated an improved temperature capability compared to standard YSZ. Examples of such systems will be shown. In modern gas turbines the increased temperatures and gas pressures lead to an increased fraction of radiative heat flow. Coatings with increased reflectivity can be used to avoid the direct heating of the metallic substrates by this radiation. An effective method to produce such coatings is suspension plasma spraying. These reflective coatings are deposited on top of the TBC system and will lead to a further grading and improved performance of the coating.
Analysis and Simulation of FGM Thermal Barrier Coatings Hot Burner Testing
Authors: Gasik Michael M. , Kawasaki Akira
Published: October 2009

For FGM thermal barrier coatings thermal-mechanical fatigue due to temperature cycling is one of the critical parameters which determine the lifetime of the TBC. In Tohoku University, a method known as “hot burner test” has been developed and was implemented into the standard JIS H 7851. For further optimization of the testing conditions and selection of the parameters for comparison of different test results knowledge of temperature and heat flux inside the test jig is necessary. FEM analysis of the heat flux and temperature inside the 14 mm diameter test stainless steel jig has been performed. Homogenous YSZ top coat with NiCrAlY bondcoat as well as FGM TBC with different gradation profiles were compared. Distributions of the temperature and heat flux are critical at the edges of the test piece and thermocouples locations, which must be taken into account when comparing test data for coatings with rather different composition and structure. The largest stress gradients develop at the ceramic-metal interface (duplex) and near the edges of the TBC.
Thermomechanical Evaluation and Thermal Expansion Behavior of Plasma-Sprayed Thermal Barrier Coatings
Authors: Takagi Kenta , Kawasaki Akira , Harada Yoshio , Okazaki Masakazu
Published: October 2009

We are investigating the feasibility of measuring thermal expansion coefficient (CTE) of free-standing thermal barrier coatings with a practical thickness of several hundred micrometers by mean of a widespread thermomechanical analysis toward its industrial standardization. First of all, this study conducted the preliminary investigation for the accurate measurement of thin samples with dense yettria-stabilized zirconia (YSZ) ceramics. With a sample supporting jig and proper conditions, even the usual thermomechanical analysis could give the accurate CTE values of thin samples down to 0.3mm thick. Also it showed good reproducibility with small measurement error less than 5%. In actual, this modified method could provide the reasonable CTE values of plasma-sprayed YSZ samples with thickness of >0.3mm. Further investigation with this method found a slight monotonic decrease in the CTE with annealing. This decrease was estimated to arise from the continuous change of microstructure which still went on even after saturation of sintering shrinkage. All the results demonstrated the present method to be available for the industrial standard.
Prospect of YAG Laser Medium for Laser Space Solar Power System and Possible Application of Graded Structure for Efficient Cooling System
Authors: Shinohara Yoshikazu , Kisara Katsuto , Suzuki Hiroaki
Published: October 2009

Laser medium for solar-pumped solid laser of 10MW-1GW power is a key to realize Laser Space Solar Power System (L-SSPS). Since it is an ultrahigh power system operated in space, the laser medium must satisfy the conditions such as high efficiency, high power per weight or volume, excellent durability and maintainability, thermal equilibrium operation, and excellent long-range propagation of oscillated laser. YAG (Y3Al5O12) ceramics doped doubly with Nd and Cr is considered to be a suitable laser medium for L-SSPS at present. There are the following important points for L-SSPS application: 1) Optimization of the doping amount, 2) Process, 3) Temperature control. Feasibility of YAG ceramics is discussed from a view point of material science and proposed a YAG ceramics structure with graded distribution of dopants.
Thermal Fatigue Damage Evaluation of EB-PVD TBC Specimens - Its Potential and Problems
Authors: Okazaki Masakazu , Yamagishi S. , Sakaguchi Motoki , Okamura T.
Published: October 2009

Thermal fatigue damage evolution behavior in thermal barrier coatings (TBCs) was studied, by employing the originally designed two dimensional ring-shape TBC specimen. The TBC specimen consisted of Ni-based superalloy IN738LC substrate, bond coat, and 8 wt.% Y2O3-stabilized ZrO2 (YSZ) top coat. The top coat was fabricated by electron-beam physical vapor deposition (EB-PVD) method with 250 micron-meters in thickness. Three kinds of MCrAlY bond coat alloys were specified as an experimental variable. Through the work, special attention was paid not only to the failure life of TBC specimen, but also to the underlying failure mechanisms. Some problems have been also pointed out, on feeding back these experimental findings to engineering applications.
Postpartum Postural Orthostatic Tachycardia Syndrome in a Patient with the Joint Hypermobility Syndrome
Authors: Kanjwal Khalil , Karabin Beverly , Kanjwal Yousuf , Grubb Blair P.
Published: October 2009

Postural orthostatic tachycardia syndrome (POTS) commonly affects women of childbearing age. We report on a 37-year-old woman who developed symptoms of recurrent syncope in the postpartum period. Her head up tilt test and clinical presentation was consistent with POTS.
Adsorption in Simulated Moving Beds
Authors: Santana Cesar C. , Silva Ivanildo J. , Azevedo Diana C. S. , Barreto Amaro G.
Published: October 2009

Chromatographic separation is based on the differential affinity of the components to a surface of solid adsorbent. While the batch or elution chromatography has found the largest number of applications up to now, Simulated Moving Bed (SMB) chromatography as a continuous process is gaining more attention due to its advantages in terms of productivity and eluent consumption. SMB is a multicolumn, continuous adsorption separation process that increases throughput, purity and yield relative to batch chromatography. Designing SMB processes involves, among other tasks, the selection of the number of columns per zone and the proper selection of the flowrates (feed, desorbent, raffinate, extract and recycle) and of the switching times in each cycle of operation. Nowadays, SMB technology has been applied to separation and purification of proteins, enantiomers and sugars. Several advances to improve SMB technology efficiency includes new configurations of equipment designs to provide more degrees of freedom than the classical process and also the implementation of the use of solvent gradient, temperature gradient and of supercritical fluids as eluents. The rise of biotechnological products within the marketplace for pharmaceuticals is but one example of how recent developments in this area are making a major impact.
Affinity Chromatography–Fractionated andDNA‐Engineered Plasma Proteins
Authors: Radosevich Mirjana , Burnouf Thierry
Published: October 2009

Biopharmaceutical plasma protein products obtained by the industrial fractionation of human plasma or by DNA engineering technologies, most often relying on synthesis in mammalian cell lines, are essential, high‐value added medicines used to treat a variety of congenital or acquired blood coagulation, immunological, or metabolic disorders. The quality of these products is largely dependent upon the characteristics of their extraction procedures which have a direct impact on the protein impurity profile and pathogen safety. Affinity chromatography has developed into a key industrial tool to purify these therapeutic protein products, most particularly those present in trace amounts in plasma. While various immobilized affinity ligands, such as heparin, monoclonal antibodies, and, to a lesser extent, gelatine, have been used for many years to extract or polish coagulation factors, there is now a pronounced interest in the evaluation of specifically designed peptide or mixed‐mode ligands that could improve extraction productivity of a wider range of plasma products, including IgG, alpha 1‐antitrypsin (AAT), and “orphan drug” proteins, like some coagulation factors and anticoagulants. This paper reviews the current status in the use of affinity chromatography procedures in the industrial manufacture of plasma‐derived (PD) and recombinant‐protein therapeutic products.
Antibiotics: Polyketides
Authors: Ma Suzanne , Pickens Lauren B. , Tang Yi
Published: October 2009

Pioneering advances in the discovery and development of antibiotics in the last century have revolutionized the way we treat infectious diseases. Once lethal infections can now be successfully treated with naturally occurring small molecular‐weight molecules. Intensive natural product screening programs around the 1950s and 1960s resulted in the discovery of a host of clinically successful antibiotic products. Even today, most antibiotics in use are either naturally produced or semisynthetically derived from natural products. The polyketide class of compounds includes several highly successful antibiotics such as erythromycin, tylosin, and tetracycline. In the decades since their discovery, many advances have been made in the production of these compounds and elucidation of their biosynthetic pathways. Advances in molecular biology has led to the sequencing and characterization of many polyketide pathways and has greatly enhanced our knowledge of how these compounds are produced. Polyketide antibiotics of bacterial origin can be grouped into two major categories, type I and type II, based on the compound structures and biosynthetic mechanisms. Type I polyketides are synthesized by large multifunctional enzymes, while type II polyketides are assembled by dissociated enzymes. Mechanistic insights into these enzymatic machineries have laid the foundation for the rational biosynthetic engineering of novel antibiotics derivatives.