To form a metallic luster on AZ31 magnesium alloy, it is necessary to optimize the surface morphology since the surface roughness affects the specular reflection of visible light, and the surface structure such as the film thickness and properties must be optimized so that light is not absorbed. We conducted experiments to analyze the relationship between surface roughness and specular reflection, and determined the range required to produce metallic luster. The ratio of the root mean square roughness σ to the wavelength of incident light λ was 0–0.067, and the ratio of the specular reflectivity R of the specimens to the specular reflectivity of a smooth surface R₀ was 0.54–1.0. The thickness of film to form a metallic luster was theoretically analyzed and found to be about 100 nm or less. The authors developed an optimum acid aqueous solution for treating the surface to form a metallic luster on the surface of AZ31 magnesium alloy. This treatment satisfied the range required to form a metallic luster identified theoretically, and formed a film with a stable structure that maintained its metallic luster. The treatment maintained the geometrical patterns such as the hair-line and blast finishing of several hundred nm or more. A sufficiently high-quality surface for exterior parts was obtained by improving the process, and the process was industrialized.

We report microstructure evolution and mechanical properties of Mg alloy AZ31 processed by a new severe plastic deformation technique which combines forward extrusion, equal channel angular extrusion (ECAE) and change channel angular extrusion (CCAE). Under all of the processing temperatures ranging from 623 K to 723 K, the grain size of the as-extruded sample was remarkably refined, which is attributed to the grain subdivision and dynamic recrystallization during the drastic deformation. We have also found the strength and tension-compression asymmetry were improved. Simultaneously, micro-fracture of tensile exhibited the characteristics of ductility, indicating plasticity of Mg alloy AZ31 was improved by compound channel extrusion.

The effects of Yb addition on the microstructure and mechanical properties of Mg-5Al alloy are investigated. The results indicate that the addition of Yb to the Mg-5Al alloy facilitates the formation of a thermally stable Al₂Yb phase, the refinement of the microstructure and the suppression of the volume fraction of Mg₁₇Al₁₂ phase in Mg-5Al alloy. Yb addition has little effect on the mechanical properties of the experimental alloys tested at room temperature. At elevated temperatures, however, the ultimate tensile strength (UTS) is significantly increased by Yb addition and Mg-5Al-1Yb has the highest UTS value than other experimental alloys. On the other hand, the yield strength (YS) increases at all tested temperatures due to the grain refinement and dispersion strengthening of the secondary phase. Meanwhile, the elongation (ε) of the experimental alloys decreases at all tested temperatures. Tensile fractographic analysis indicates that cleavage fracture is the dominant mechanism of the Mg-5Al and Mg-5Al-xYb alloys at room temperature. At elevated temperatures, however, the fracture mechanism of experimental alloys mainly changes from cleavage to quasi-cleavage fracture.

We investigated the influence of a change in the stacking sequence of the close-packed plane in a Mg₁₂ZnY long-period stacking ordered (LPSO) phase on its mechanical properties. A 14H-typed LPSO-phase crystal was fabricated by annealing a directionally solidified (DS) crystal with a 18R-typed LPSO-structure at 525°C for 3 days, and the temperature dependence and orientation dependence of the yield stress were examined via compression tests. (0001)⟨11\\bar20⟩ basal slip was identified as a dominant deformation mode, and deformation kink bands were formed under compression in the case of suppression of basal slip motion. The deformation mechanism of the 14H-typed LPSO-phase is almost similar to that of the 18R-typed LPSO-phase, even though a slight difference was observed at temperatures above 300°C.

The microstructure, texture and mechanical properties of Mg-1.5 mass%Zn-0.2 mass%Ce alloys extruded at different extrusion temperatures were investigated. A “rare earth (RE)” texture component, which laid at about 20° from ⟨2\\bar1\\bar10⟩ in an inverse pole figure, appeared in the as-extruded specimen, only when the extrusion temperature was set to 703 K. It is suggested that a high extrusion temperature of around 723 K is essential for the formation of RE texture component. Electron back-scatter diffraction (EBSD) measurements revealed that the RE texture component originated from dynamic recrystallized grains in the band microstructure around the unrecrystallized grains, in contrast to the results of previous studies, in which it originated from shear bands in the unrecrystallized grains. The specimen extruded at 703 K and subsequently annealed showed a lower yield stress and higher ductility than that extruded at 573 K and subsequently annealed, owing to the wider spread of texture originating from the RE texture component in the as-extruded specimen.

HFC125 is a potential substitutive to SF₆ in terms of its protective effectiveness, reduced GWP and cost. In the present study, corrosivity of HFC125 containing nitrogen atmosphere to the medium-carbon steel of C45E4 was examined by systematic experiments under the temperatures and HFC125 concentrations commonly used in Mg die-casting practice. For comparison, the corrosivity of SF₆ containing nitrogen atmosphere was examined in the identical conditions, followed by X-ray diffraction and X-ray fluorescence characterization of the corrosion products. The results show that the HFC125 containing nitrogen atmosphere was less corrosive to C45E4 than SF₆ containing one in long-playing corrosion under identical conditions. Oxidation was the major cause of the corrosion to C45E4 and HFC125 or SF₆ was of secondary contribution. HFC125 or its decomposition was deduced to corrode C45E4 to produce fluorides; SF₆ or its decomposition was deduced to react with C45E4 to produce sulfides.

Four kinds of Mg-x mass%Zn-y mass%Al (x=6, 8, 10, 12 and y=3, 4, 5, 6) alloys, each with a grain size of 2∼3 μm and containing quasicrystal phase particles, were successfully produced by casting and extrusion. These rare-earth free wrought processed magnesium alloys showed a reduction in mechanical asymmetry and a weak basal texture. Although the yield strength improved, the elongation decreased with increasing volume fraction of quasicrystal phase particle. The decrease in ductility was related to the existence of coarse quasicrystal phase particles. The strength was affected by the interface strength mechanism; however, the coherency strain in the quasicrystal phase was smaller than that in the conventional phase, due to the strong matching between the matrix and the quasicrystal phase.

Effects of the laser removal processing on corrosion resistance and conductivity for the magnesium alloy products anodized from the phosphate electrolytic solution were examined. The area where anodized coating was removed under the appropriate laser irradiated condition showed the excellent corrosion performance as well as good conductivity. This improvement of the conductivity is attributable to the removal of the anodized coatings whose conductivity is not good, and molten sputter then formed from the magnesium alloy substrate by means of the laser thermo processing becomes covered with the anodized coatings. Furthermore, this excellent corrosion resistance is based on the sacrifice corrosion protection by anodizing from the phosphate electrolytic solution.

Tensile tests and Charpy impact tests have been performed on pure cast Mg with hydrogen concentrations of 16–35 mass ppm, where hydrogen was mainly segregated at triple junction of grain boundaries. Tensile properties were not affected by the hydrogen concentration, but crack formation at grain boundaries was enhanced by an increase in hydrogen concentration. The Charpy impact tests showed that the Mg with a higher hydrogen concentration exhibited a higher ductile-brittle transition temperature and that the temperature dependence of the Charpy impact energy was in good agreement with that of fractography. Thus, the segregation of hydrogen at grain boundaries likely induced the intergranular fracture of Mg.

Magnesium-carbon powders and Magnesium-lithium powders were used as the anode materials for lithium ion batteries to investigate the structure and electrochemical behavior in room temperature. The composition of Mg-C powders contained 1:1 and 9:1. The powders and the thermal evaporated films of Mg-10Li were compared with Mg-C systems. In addition, Mg-10Li thermal evaporated film was used as the experimental materials to process the annealing treatment. The results show that Mg-C powders system had the interface effect of a Cu foil to reduce the electrochemical reaction. With increasing the carbon powder content, the charge-discharge characteristics of Mg-C powders was raised. Notably, the Mg-10Li specimen had better cycling properties than that of Mg-50C (1:1). After annealing at 200°C for 1 h, Mg-10Li alloy film not only increased the capacity, but also improved the charge-discharge cyclability.

Among the large number of superlattices, there is a special group which may be classified as long period superlattices, the copper-gold system provides a classical example of such structure. Despite that historically, the copper-gold alloys containing about 25 atom percent gold were among the first investigated alloys, it still represents a subject of numerous studies. In the present work, we study all the possible phase transitions in the binary intermetallic alloy Cu₃Au using differential scanning calorimetry (DSC) and differential dilatometry. A new important anomaly due certainly to a new ordered reaction has been detected at low temperature range by these two methods. To confirm this new reaction, we have used other techniques as high resolution transmission electron microscopy (HRTEM), electrical resistivity and microhardness measurements. The kinetics parameters as activation energy E_act and Avrami exponent n have also been calculated respectively by Starink and John Mehl Avrami Kolmogorov (JMAK) methods.

ZnO/In/ZnO tri-layer thin films were designed and fabricated by RF sputtering on copolymer substrate. Under an electrical current, the thermoelectric effect of direct current (DC) reduced the electrical resistance and improved the crystallization and Raman properties. Also, indium atoms had migrated into the ZnO matrix and a diffusion layer in the ZnO/In interface had grown. The electrical current induced temperature is ∼140°C and the copolymer substrate suffers no damage and so can be applied to the low temperature optoelectronic devices.

Thermal expansion, permeability, and magnetization measurements of ferromagnetic shape memory alloys, Ni₅₂Mn_12.5Fe_12.5Ga₂₃ and Ni₂Mn_0.75Cu_0.25Ga, were performed across the martensitic transformation temperature T_M and the reverse martensitic transformation temperature T_R. When cooling from austenite phase, a steep decrease in the thermal expansion due to the martensitic transformation was found for both alloys. Considering the permeability and magnetization results of Ni₂Mn_0.75Cu_0.25Ga, the region above T_M or T_R is the paramagnetic-austenite (Para-A) phase and the region below T_M or T_R is the ferromagnetic-martensite (Ferro-M) phase. Magnetic phase diagrams were constructed based on the results of the temperature dependence of thermal expansion. T_M and T_R increased gradually with increasing magnetic field. For Ni₅₂Mn_12.5Fe_12.5Ga₂₃ and Ni₂Mn_0.75Cu_0.25Ga, the shifts of T_M in magnetic fields (B) were estimated as dT_M⁄dB≈0.5 K/T and 1.2 T/K, respectively. The shifts of T_M indicate that the that magnetization influences martensitic transition and the increase of T_M in accordance with the magnetic fields is proportional to the difference between the magnetization of austenite phase with that of martensitic phase.

Thin films of Pd-Cu-Si metallic glassy alloys of varying composition were prepared by simultaneous three sources (Pd, Cu and Si) sputtering method using a rotating mechanism of substrates. Their H₂ responses were observed by measuring the electric resistance changes of them exposed in N₂ and H₂. In addition, their linear expansion coefficients (LECs) induced by absorbed hydrogen were also measured.
Contrary to a normal H₂ response transient with a rapid increase in electric resistance of a thin film, several thin films indicated abnormal H₂ response transients consisting of complex changes, an increase and a decrease, in electric resistance when the thin films were exposed in H₂. These thin films have higher Pd/Si atomic ratios than those indicated normal H₂ response transients. Additionally, by the characterization of the thin films, the existence of Pd-nanocrystals of about 2 nm in diameter was observed in the amorphous matrix which possibly includes Pd-clusters as well as Pd atoms.
The mechanism of the abnormal H₂ response transient can be explained by two conflicting behaviors in electric resistance of the thin films when they are exposed in H₂: a decrease by the formation of electrical contacts of Pd-nanocrystals connected with volume expanded Pd-clusters by hydrogen absorption and a following increase by hydrogenation of Pd-nanocrystals. Observed time lags between two conflicting behaviors can be explained by the different transfer speeds of hydrogen relating to two kinds of pathways: inside of Pd-nanocrystals and the amorphous matrix along which hydrogen atoms transfer in the structure.
The Pd-nanocrystals also affected on LEC and the H₂ response significantly. The thin films with them indicated much higher LEC than the thin films without them. However, the thin films with them did not indicate the high H₂ response expected from their high LEC. The result of LEC suggests that Pd-nanocrystals can absorb much more hydrogen atoms than Pd in an amorphous matrix. The Pd in an amorphous matrix is supposed to be Pd-clusters, randomly distributed Pd atoms and Pd atoms forming a trigonal prism that is a structural unit of the Pd-Cu-Si alloys. On the other hand, the high H₂ response according to the high amount of absorbed hydrogen can not be expected in the thin films with Pd-nanocrystals, due to a decrease in electric resistance by forming electrical contacts of the Pd-nanocrystals.

In this study, sintered bodies of ZrO₂ nanopowders were fabricated by combined application of magnetic pulsed compaction (MPC) and subsequent sintering and finally, their density and shrinkage were investigated. The Optimum mixing conditions of PVA, water, and TiO₂ nanopowder for compaction was found to be 1.8 mass% PVA, 10.7 mass% water, and 87.5 mass% of ZrO₂ powder at the sintered bulks. High pressure and rapid compaction using magnetic pulsed compaction (MPC), enhanced the density with increasing MPC pressure up to 3.5 GPa and significantly reduced the shrinkage rate (about 10–12% in this case) of the sintered bulks compared to the general process (about 18%).

Al-Si hypoeutectic alloys have excellent castability and sufficient strength in combination with other alloying elements. Especially, Al-Si alloy containing Mg used for high-quality die-casting is well-known as a high strength alloy brought by the appropriate heat treatment and consequential precipitation hardening of Mg₂Si intermediate phase. T6-heat treatment must be applied for maximum strength, but solution at high temperature and quenching treatment often conduct the product deformation and extra cost for fabrication. Therefore only artificial aging (T5-heat treatment) at comparatively lower temperature is mainly applied to industrial die-casting products. However, there are few studies on age hardening characteristics supplied by T5-heat treatment to Al-Si hypoeutectic alloys. To understand the age hardening behavior of Al-10 mass%Si-0.5 mass%Mg and Al-10 mass%Si-0.8 mass%Mg alloys in detail, microstructure observation and hardness measurement were performed. These alloys quenched in iced water, naturally aged at room temperature and artificially aged at 423–523 K, showed conspicuously age hardening behavior. Age hardening of Al-Si-Mg alloy generally considered to be the main cause of the precipitation-based hardening in α phase, nevertheless it was seen that precipitation occurred in α-Al+Si eutectic phase. Consequently, from the microstructure observation using SEM, it’s thought that the age hardening of these alloys was mainly composed of the hardness change in α-Al+Si eutectic phase.

It is important to identify residual strength against fatigue damage to ensure the structural integrity of plant components subjected to cyclic loading. In this study, the degree of fatigue damage induced in Type 316 stainless steel was estimated from the local change in crystal orientation (local misorientation) measured by electron backscatter diffraction (EBSD). Crystal orientations were identified by scanning the surfaces of samples that had been subjected to a fatigue test or a tensile test. The magnitude of the averaged local misorientation, M_ave, increased as the strain amplitude and the number of cycles increased, and the relationship between strain amplitude, number of cycles and M_ave was obtained. Moreover, from the correlation between M_ave and another parameter, MCD, which reflects the average of the orientation spread within the grains, it was shown to be possible to distinguish whether damage was caused by cyclic loading or monotonic loading. Further investigation of the local misorientation revealed that the amplitude of fatigue loading could be estimated from the statistical distribution of local misorientation averaged for each grain. It was concluded that fatigue damage (residual fatigue strength) could be quantified by EBSD measurements using the estimated strain amplitude and the relationship between strain amplitude, number of cycles and M_ave.

This work is focused on the influence of cold-rolling on the transformation and internal friction behavior of TiNi shape memory alloy. The DSC results show the endothermic peaks disappeared with the increasing of cold-rolling reduction and there was an exothermic peak around 330°C on the curve during the first heating process. The exothermic peak is associated with recrystallization of amorphous phase induced by cold-rolled work. During the second heating process, the endothermic peak showed up but the exothermic peak didn’t. These phenomena are confirmed by the internal friction results. During the first heating process, the transformation internal friction decreased with the increasing of the cold-rolling reduction and the internal friction augmentation appeared around 330°C which is related to recrystallization.

The effect of adding up to 4 mass% of strontium to Mg-5Al-3Ca alloys was investigated in terms of microstructural and mechanical properties. The major interdendritic intermetallic compounds of as-cast alloys changed from the Mg₂Ca phase to a combination of the (Mg,Al)₂Ca and Al₄Sr phases. The morphology of the interdendritic α-Mg/Al₄Sr eutectic phase also changed from a coarse lamellar structure at a low strontium concentration to a bulk-like ultrafine lamellar structure at a high strontium concentration (4 mass%). The creep resistance was improved by the addition of up to 2 mass% strontium but it was saturated at a higher strontium concentration.

AZ31 Mg alloy in a friction stir processed condition was deformed in tension at temperatures ranging from room temperature to 300°C in comparison with the same alloy in an extruded condition. It was found that friction stir processed AZ31 possesses excellent ductility at a comparatively low thermal exposure temperature (100°C) and a significant difference of strain hardening behavior compared with as extruded one. These results show that the formability of friction stir processed specimens is better than that of as extruded samples due to the differences in texture and microstructural features. In order to confirm these findings, the present study conducted tensile tests from room temperature to 300°C and verified the improvement in ductility. The effect of exposure temperature on formability will be discussed as well.

A new pyrometallurgical process for the recovery of metallic indium and tin from ITO scrap has been proposed based on the present thermodynamic study on the In-Sn-O ternary system. In the present study the phase relations and the equilibrium partial pressures of oxygen in the ternary system were determined at the temperature of 1173 K. Then by applying the Gibbs-Duhem equation to the phase relation of alloy-oxide equilibrium, the activities of the components were obtained at 1173 K using the equilibrium partial pressures of oxygen. Moreover, the vapor pressures of indium and tin were calculated at temperatures of 1173 and 1400 K to discuss the proposed process. The process consists of two stages of reaction: first is the reduction of ITO by CO to In-Sn alloy at a low temperature. Second is the preferential vaporization of indium at a high temperature due to the three orders of magnitude difference between the vapor pressure of indium and that of tin.

The aim of this work is to study MnO reduction by solid carbon. The influence of size of carbon particles, slag basicity, and bath temperature on MnO reduction was investigated. Fine Manganese ore particles were used as a source of MnO. Three sizes of carbon particles were used; 0.230 mm, 0.162 mm and 0.057 mm, binary basicity of 1 and 1.5 and temperatures of 1550, 1550 and 1600°C. Curves were drawn for Mn content in the bath as a function of time and temperature for the several studied parameters. The MnO reduction rates were determined using these data.

Continuous pearl-necklace-shaped In₂O₃ ceramic nanofibers with diameters around 30∼100 nm have been fabricated by electrospinning combined with annealing process used indium nitrate and poly(vinylpyrrolidone) (PVP) as raw materials. The specific surface area of In₂O₃ ceramic nanofibers comes up to 100 m²/g. The morphology and chemical structure of the as-prepared and calcined samples were analyzed by scanning electron microscopy (SEM), thermal gravimetric analysis (TGA), high-resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) techniques. The gas sensor fabricated by In₂O₃ ceramic nanofibers sintered at 700°C has special gas sensing properties including high response and selectivity, fast response and recovery time to ethanol gas.

Leaching of nickel garnierite ore with sulfuric acid resulted in a mixed sulfate solution of Co(II) and Ni(II) with high magnesium content. In order to find an optimum condition to separate cobalt, solvent extraction experiments have been performed from the synthetic leaching sulfate solution with the following composition: Co(II)=0.08 g/L, Ni(II)=4.4 g/L, Mg(II)=32.2 g/L. The effects of extraction variables on the separation of Co(II) from nickel and magnesium were investigated by using D2EHPA, PC88A, Cyanex272, and Alamine336. Saponifiaction degree of cationic extractants, extractant concentration, and volume ratio were changed. In our experimental range, extraction of nickel was negligible. Among the cationic extractants tested in this study, the highest separation factor between Co(II) and Mg(II) was obtained with saponified Cyanex272. Alamine336 in the presence of MgCl₂ extracted only Co(II), while the extraction percentage of Mg(II) was nearly zero.

A new cost-effective process to fabricate aluminide coatings was developed. Coating layers consisting of nickel aluminides could be formed by electrodeposition of Al layers from a dimethylsulfone-AlCl₃ electrolyte on Ni substrates and subsequent annealing in air or vacuum at temperatures of 700–1150°C. Analysis of the intermetallic layers by XRD, SEM and EDX indicated the formation of Al₃Ni and Al₃Ni₂ at 700°C, AlNi at 900°C and 1000°C, and AlNi and AlNi₃ at 1150°C. The Annealing atmosphere did not affect the resulting intermetallic products.

Aluminum-oleic acid composite nanoparticles with a mean diameter of 85 nm were successfully prepared by means of a wet chemical process. The Al/oleic acid molar ratio has effects the thickness of the oleic acid layer on Al nanoparticles. Al electrodes can be formed by firing an Al nanoparticle paste film at 600°C, and the firing temperature is about 300°C lower than that required for micrometer-sized Al particles. The electrode formed from commercial Al nanoaparticles is not electrically conducted because of the oxide layer Al nanoparticles; however, the film from the prepared Al nanoparticles for an Al/oleic acid molar ratio of 1:0.05 has a minimum specific resistance of 5.6 mΩ·cm.

The effect of shielding gas composition on the phase transformation and the mechanism of pitting corrosion of hyper duplex stainless steel (HDSS) welds was investigated in highly concentrated chloride environments. The resistance to pitting corrosion of a HDSS tube after welding with Ar shielding gas supplemented with N₂ was increased due to a decrease of the PREN (Pitting Resistance Equivalent Number) difference between the γ-phase and the α-phase in the weld metal and the heat affected zone. Cr nitrides (Cr₂N) were precipitated in the weld metal and the heat affected zone due to a high α-phase content. Cr-depleted zone adjacent to Cr₂N decreased the resistance to pitting corrosion.

The electrodeposition behavior of Sn–Cu alloys in a sulfate solution containing three additives, cresol sulfonic acid, benzal acetone, and nonionic alkyl polyethylene glycol ether surfactant, was investigated potentiostatically between +0.3 and −0.7 V vs. NHE at 298 K. The contact resistance of the alloys deposited on a Cu connector was evaluated. Cu in the alloys behaved as a more noble metal than did Sn, thus showing the typical feature of regular-type codeposition. In solutions containing additives, the difference in deposition potential between Cu and Sn decreased because Cu deposition was significantly suppressed by the additives. The alloys deposited in solutions containing additives exhibited smooth surfaces and were composed of Cu, Sn, Cu₆Sn₅, and Cu₃Sn phases in accordance with the equilibrium phase diagram of a binary Cu–Sn system. The contact resistance of the alloys increased by heating at 433 K, thus indicating that connecting reliability did not improve by plating with the stable metallic compound Cu₆Sn₅. The connecting reliability of a connector after abrasion was higher in deposited alloy films than in Sn reflow plating.

Improved corrosion resistance of steel sheets plated with zinciferous metal, and particularly 55% Al-Zn alloy coated steel sheets, has become necessary in recent years. However, 55% Al-Zn alloy coated steel sheets are susceptible to surface cracks during forming due to the hardness of the metallic coating. This research examined various non-chromate corrosion-preventive compounds for organic-inorganic composite coatings and found that a composite coating containing a mixture of Zn₃(PO₄)₂ and CaSiO₃ provided the highest corrosion resistance among all the additives tested. The corrosion mechanism was investigated by post-test analysis of the specimens by SEM, AFM, TEM and EDX, revealing that an amorphous surface layer, which was approximately 30 nm thick and contained Ca, Cr, P, Si, C, and O, had newly formed on the steel surface exposed after deformation of the coating. It is presumed that Ca²⁺ and HPO₄²⁻ were formed by dissolution of the CaO component in CaSiO₃ and hydrolysis of ZnO₃(PO₄)₂, respectively, and reacted to form an insoluble Ca-phosphoric acid compound which inhibited corrosion of the metal exposed by cracks.

Resistance microwelding of fine insulated copper wire to phosphor bronze thin sheet without prior removal of insulation is of increasing industrial importance for electrical connections in downsized electronic devices, but the understanding of the process is very limited. Therefore, this work aims to clarify the basic joining mechanism. The effects of main process parameters (welding current, weld time and electrode force) and joint microstructure were investigated by tensile testing, optical microscopy, scanning electron microscopy and energy dispersive X-ray spectroscopy. A welding mechanism with main process stages (cold wire deformation, insulation melting and displacing, and solid-state bonding) is proposed. It should be pointed out that there is no weld nugget forming at the faying surfaces.

Particles made by coating an insulating core with a thin layer (shell) of conducting materials, called core-shell particles, were recently proposed to realize materials with particular nano-scale structures. Such structures work as a “porous medium” of electric current, and their modified characteristics may be useful to improve some materials, such as transparent conducting films. We have already reported 2D simulation of such a conducting film with core-shell particles.
In this report, the basic feasibility of this idea is tested within the framework of the percolation model and the random register network model. The observed critical behavior and critical exponents of conductivity are also discussed, for the first time for 3D situations with core-shell particles.

Porous aluminum is expected to be applied as a multifunctional material in various industrial fields because of its light weight and high energy absorption. When aluminum alloy die castings are used as a starting material in the fabrication of porous aluminum, it can be expected that, by effectively using the gases intrinsically contained in the die casting to generate pores, porous aluminum can be fabricated by adding a small amount of blowing agent. In this study, while systematically varying the amount of blowing agent from 0 to 1.4 mass% that is added to ADC12 aluminum alloy die castings containing three different amounts of gases, porous aluminum is fabricated by the FSP (friction stir processing) route precursor method. Titanium(II) hydride powder is used as the blowing agent. The variations of porosity and pore structure with the amount of added blowing agent are investigated for each amount of gases contained in the die castings. On the basis of the results, it is shown that, by using a blowing agent of approximately 0.6 mass%, ADC12 porous aluminum with high porosity can be fabricated regardless of the amount of gases contained in the die casting.

Complex and thin-walled refractory metallic parts including molybdenum (Mo) rocket nozzle and crucible were fabricated using plasma spray forming (PSF) followed by hot isostatic pressing (HIPing). Optical microscope (OM), scanning electron microscope (SEM), Archimedes method, Vickers hardness and tensile tests have been employed to study microstructure, density, micro-hardness and mechanical properties of the parts. A lamellar structure consisting of vertical columnar grains, micron-sized pores, partially melted particles and rough interlamellar contacts with gaps of sub-micron sizes between lamellae were found in PSF Mo deposits. Relative density, micro-hardness and ultimate tensile strength (UTS) of the deposits were about 89%, 150 HV_0.025 and 44 MPa, respectively. After low-pressure and two-step HIPing, those changed up to about 92%, 250∼400 HV_0.025 (interior ∼ exterior layers), 93 MPa, and 97%, 325 HV_0.025 and 170 MPa, respectively. Moreover, a four-stage mechanism of HIPing for PSF parts including heating up, recrystallization, lamellae movement, plastic yielding and creep has been proposed and discussed in detail.

SiC membranes were prepared using curing of precursor polymer (polycarbosilane, PCS) film by electron beam irradiation in helium atmosphere. The membrane prepared via curing of PCS film coated using 10 mass% PCS solution for dip-coating followed by immersing it for 30 s in PCS solution, showed H₂ permeance of 3.1×10⁻⁷ mol/m²/s/Pa and the selectivity of 51 at 523 K. The H₂ permeance of the membrane was increased proportional to the temperature by the activated diffusion of H₂. It indicates SiC film without pinholes or cracks formed on the support. As the pyrolysis temperature of cured PCS film was increased, the selectivity of the membrane reached the maximum at 923 K.

Chloro-based volatile organic compounds (VOCs) are known to exert noxious effects on the environment, and their destruction by catalytic combustion, for example, accompanies a production of hydrochloric acid (HCl) that damages the catalyst. We have been interested in complete removal of VOCs by our system based on thermally activated oxide semiconductors (i.e., catalysts) such as Cr₂O₃, TiO₂, NiO, α-Fe₂O₃. In the present investigation, we have fundamentally studied the decomposition process of dichloromethane (CH₂Cl₂: DCM) and trichloroethylene (CHCCl₃; TCE) on the basis of the mass- and Raman spectra in an attempt to identify the formation temperature of HCl. Then, we found that the decomposition of DCM and TCE starts at about 100 and 200°C, respectively; whereas HCl is abruptly formed at a critical temperature of about 350°C in both compounds. Based on this result, we have optimized the operation temperature below 300°C for Cr₂O₃-impregnated honeycomb systems and achieved the complete removal of DCM and TCE that accompanies no formation of HCl.

A new process for producing ferromolybdenum powder master alloy without generating secondary pollutants by a two-step hydrogen reduction process involving MoO₃ and mill scale has been developed. In this process, mill scale which is an iron byproduct generated from the steel rolling process is used as an iron source. Experimentally, ferromolybdenum powder master alloy was produced by a two-step hydrogen reduction process: The first hydrogen reduction stage was carried at a horizontal furnace for 60 min at 848 K under a hydrogen gas at a partial pressure of 101.3 kPa, and the second hydrogen reduction stage was done at the same furnace for 40 min at 1123 K under the same hydrogen partial pressure. In the process, the reduction reactions of MoO₃ to MoO₂ and mill scale to Fe proceed simultaneously in the first reduction step, and then the reduction reaction of MoO₂ to Mo does in the second reduction step. The reaction rate of the second step in the two-step hydrogen reduction process of MoO₃-Fe₂O₃ mixture was also measured under isothermal condition in hydrogen atmosphere using TGA equipment. As an example, at 1173 K under a hydrogen partial pressure of 101.3 kPa, almost 100% of MoO₂ was reduced to Mo in 5 min. The nucleation and growth model were found to be applicable to the reaction rate. The reaction was first order with respect to hydrogen partial pressure and had an activation energy of 83.8 kJ/mol (20.1 kcal/mol).

Bragg-edge transmission imaging using a pulsed neutron source is expected to be a new method to investigate the crystallographic and metallographic structure of a material. This method has attracted the attention in the research field of material characterization for materials development and industrial applications because it non-destructively provides the images on the texture and the microstructure inside a material such as a thick steel bulk over the wide area of the material. For deducing such information from the Bragg-edge transmission spectrum, a data analysis code like a Rietveld analysis code for powder diffractometry is indispensable. So far, only the information on the crystallographic anisotropy has been deduced. However, this information is incomplete since both the preferred orientation and the crystallite size affect the Bragg-edge transmission spectrum. Therefore, we have developed a Rietveld-type analysis code, RITS, that allows us to obtain the information on preferred orientation and crystallite size at the same time. To examine the feasibility and the usefulness of the RITS code, we have analyzed the Bragg-edge transmission spectra of rolled and welded α-iron plates, and we have successfully obtained the preferred orientation data and the crystallite size data over the wide area of the bulk specimens.

The uptake of Cd(II) by waste calcite, a by-product of the carbonation of flue gas desulfurization (FGD) gypsum, was investigated in a batch experiment. The uptake of Cd(II) by and the dissolution of Ca(II) from the waste calcite particles were monitored simultaneously as a function of exposure time to 0.89 mM Cd(II) solution. The reagent-grade calcite particles were also examined for a comparative study. The waste calcite contained bassanite, dolomite, and muscovite as the major impurity phases. X-ray diffraction study revealed that the bassanite phase dissolved almost completely during the 1st hour of the exposure to the solution while other phases were intact for two days. The amount of removed Cd(II) was found to be proportionally related to dissolved Ca(II) reflecting the exchange nature of the adsorption. The use of waste calcite instead of reagent-grade calcite enhanced Ca(II) dissolution and thereby Cd(II) uptake significantly. The waste calcite removed about 90% of initial Cd(II) while reagent calcite removed only 6% during the exposure for 2 days to 0.89 mM Cd(II) solution. The enhanced Ca(II) dissolution and Cd(II) uptake by the waste calcite were attributed to the fast-dissolving bassanite phase which provides the substantial quantity of Ca(II) and sulfate ions to the calcite/solution interface.

The effects of Fe content and cooling rate on the solidification path and formation behavior of the Al₅FeSi (β) phase in Fe-containing eutectic Al-Si alloys were studied based on thermodynamic analysis and pertinent experiments. To predict solidification path in Fe-containing eutectic Al-Si alloys, the thermodynamic calculations in the Al-Si-Fe ternary system, including the high Fe region, were systematically performed using the Thermo-Calc program and updated database. To experimentally verify the predicted results, designed two eutectic Al-Si alloys with different Fe levels were solidified under slowly- and rapidly-cooled conditions, respectively. The cooling curves of the solidified alloys were recorded by thermal analysis. Microstructures of the casting samples were studied by the combined analyses of optical microscopy (OM) and scanning electron microscopy (SEM). For the slowly-cooled condition with the high Fe level, the primary β phase was mainly formed by the quasi-peritectic reaction of L+γ→α+β (656°C). For the rapidly-cooled condition with high Fe level, the primary β phase was mainly formed by the reaction of L→β (583∼649°C).

Red electrophosphorescent organic light-emitting devices using red phosphorescent dopant, and tris-(8-hydroxyquinoline)-aluminum (Alq₃) and 2,9-dimethyl-4,7 diphenyl-1,10-phenanthroline (BCP) electron injecting have been fabricated. A device with Alq3 as electron transport layer shows high turn-on voltage (@ 1 cd/m²) of 6.25 V, but a device with BCP does lower turn-on voltage of 5.0 V. Alq₃ and BCP have silimar lowest unoccupied molucular obital, 3.0 eV and 2.9 eV, which are the higher values than work function of Ba (2.7 eV). So, Ba cathode does not form energy barrier to inject electron to organic layer from simple energy band of view. However, these devices represent different injection properties, therefore we analyze the interface between organic layer and cathode. X-ray photoelectron spectroscopy depth profiling measurements reveal the strong chemical reaction and bonding of Ba with the C and O present in the Alq₃ molecules. Results show that the performance of the electrophosphorescent devices is mainly governed by the structure and the chemical reaction at the interface between Ba metal and electron-injecting material.

The effect of electroslag refining on removal of iron from commercial purity aluminum using KCl-NaCl-Na₃AlF₆ slag containing Na₂B₄O₇ was studied. The iron content decreases with the decrement of the remelting speed and the iron content can decrease from 0.42% to 0.20 mass% after electroslag refining. The chemical reaction between melt and slag to form Fe₂B in the electroslag refining process is the main reason for the reduction of iron content. Thermodynamic calculation of the chemical reaction theoretically accounts for the formation of Fe₂B spontaneously in the electroslag refining process. The ultimate strength and elongation of commercial aluminum are improved obviously after electroslag refining.

It is known that solid solution softening occurs in Fe-Si and Fe-Al alloys. In the present work, electronic structures of pure Fe, Fe-Si, Fe-Al, Fe-Cr and Fe-Co alloys are investigated by first-principle calculations to understand the solid solution softening mechanisms. The calculations suggested that the charge density is reduced and bond-breaking occurs easily at the solute and solvent atomic bonds in the softened Fe-Si and Fe-Al alloys, which results in solid solution softening.

Recovery of glass fibers from fiber reinforced plastics (FRP) has been tackled by our novel technology based upon thermally activated semiconductors such as Cr₂O₃, NiO, TiO₂, and α-Fe₂O₃. This is a scientifically proven technology which utilizes a vast number of thermally-generated oxidative holes for instantaneous decomposition of filler-free thermoplastic or thermosetting polymers. No shredding or grinding of the scrap FRP is necessary in the present system, nor is the use of organic solvents. FRP plates were simply placed in contact with powdered Cr₂O₃ and heated at about 350–500°C. As soon as the FRP was sufficiently heated, the polymer matrix began to decompose into H₂O and CO₂, leaving behind only glass fibers without any deterioration of their quality. The glass fibers were perfectly recovered, exactly in the original form of “chopped strand mat”. Our system can recover glass fibers as well as thermal energy.

Resistance spot welding has been performed in order to investigate the weld characteristics of boron-containing steel. With heat input increasing, the nugget width increased, which showed a direct proportion to shear tension strength. After welding process, the microstructure of the steels, mainly consisting of martensite in base material, was transformed to ferrite and tempered martensite in HAZ region, while weld zone is chiefly composed of martensite phase due to rapid quenching. The hardness was measured as about 550 Hv at weld zone, and 320 Hv in the region of heat affected zone in spite of 550 Hv of base material. It is deduced that the softening behavior occurred because heat input of welding caused phase transformation of martensite into tempered martensite and ferrite.

The master sintering curve (MSC) is an effective method to predict densification during sintering or hot pressing. In MSC, the sintered density is a unique function of the integral of a temperature function over time, irrespective of the heating path. As a practical application of the MSC, the Fe-based powder mixture consisting of 6 different metallic materials was used since it is one of the most common soft metal-bonds of the diamond tool industry. The effective activation energy of sintering was found to be 200.2 kJ/mol. It suggests that the dominant densification mechanism for the present metallic powder was the diffusion of Cu since the effective activation energy was in good agreement with that of self diffusion in Cu from literature. Three data sets having different heating rates merged onto a single curve when the density was plotted as a logarithmic function of Θ, the integral of temperature function over time. Thus, the density versus Θ profile can be used to predict the final density of Fe-based metallic powder at a given pressure regardless of heating history. The study was also extended to a range of pressures from 9.7 MPa to 58.1 MPa to generate the pressure-assisted master sintering surface (PMSS).