Because of its chemical stability and low cost, iron silicide is a promising thermoelectric material for use at high temperatures. Its performance, however, is poor compared with that of BiTe, PbTe, or SiGe, which are popular thermoelectric materials. We produced n-type FeSi₂ samples containing various oxides, which showed a good thermoelectric performance. We attempted to unify the parameters attributing to thermoelectric performance, and the electrical resistivity decreased while an adequate Seebeck coefficient was retained and the thermal conductivity was reduced. This results in a greater value of the Seebeck coefficient, particularly on addition of Sm₂O₃; the resulting figure of merit ZT was 0.56 at 868 K. Addition of Er₂O₃ gave a ZT value of 0.54 at 877 K, and the material showed a lower thermal conductivity of 2–2.5 W/m·K.

View full abstract

We examined the effect of addition of titanium nitride on thermoelectric performance of this material. The samples constructed of Y-doped SrTiO₃ and TiN were prepared by two steps of the solid-state reactions. SrTiO₃ with cubic perovskite structure was formed in all samples. The highest electric conductivity was found for Sr_0.9Y_0.1TiO₃-0.1TiN, whereas the largest absolute value in Seebeck coefficient was found for Sr_0.9Y_0.1TiO₃. Lower thermal conductivity was found for Sr_0.9Y_0.1TiO₃-0.1TiN. The ZT was calculated from the electric conductivity, the Seebeck coefficient, and the thermal conductivity. A high performance was shown in Sr_0.9Y_0.1TiO₃-0.1TiN, giving a high electric conductivity and a low thermal conductivity simultaneously. The highest value of ZT was obtained to be 0.26 at 1077 K for this sample.

View full abstract

Pb-filled Chevrel-phase sulfides PbMo₆S_8−y were prepared from PbS, Mo, and MoS₂. The single phase was formed in the nominal composition PbMo₆S_7.8 (8−y=7.8). While the secondary PbS and Mo phases were formed in sulfur-poor compositions, the secondary MoS₂ phase was formed in sulfur-rich compositions. The sintered sample had a positive Seebeck coefficient. The Seebeck coefficient and electrical resistivity increased with temperature. Furthermore, the thermal conductivity was dominated by the electronic thermal conductivity, and the complex crystal structure yielded a low lattice thermal conductivity. The thermoelectric figure of merit ZT increased with temperature, reaching a value of 0.08 at 850 K.

View full abstract

Temperature dependence of chemical potential was determined for n-type Bi₂Se₃ and p-type Bi₂Te₃ thermoelectric materials by means of angle resolved photoemission spectroscopy, and the determined chemical potential was compared with the measured thermoelectric power. We found that the temperature dependence of chemical potential is significantly large for the present materials and the large thermoelectric power is mainly caused by the chemical potential effect. This fact strongly indicates that the temperature dependence of chemical potential has to be properly understood to construct a guiding principle for developing new, practical thermoelectric materials.

View full abstract

Power generation performance of the thermoelectric module consisting of the Sb-doped Heusler Fe₂VAl alloy was evaluated. For the construction of the module, conduction type controlled Fe₂VAl alloys were prepared by adjusting the valence electron density. For the enhancement of thermoelectric properties of the n-type Sb-substituted Fe₂VAl alloy, Al site was additionally substituted by Si. In order to change the conduction type from n-type to p-type, additional Ti substitution for the V site was examined and large positive Seebeck coefficient was obtained. Power generation test of the module consisting of these alloys was conducted on a hot plate of 573 K in air. The maximum output power of the thermoelectric module consisting of 18 pairs of p-n junction was estimated to be 2.5 W. The reduction of thermal conductivity by the Sb-doping increased temperature difference at thermoelectric elements, resulting in the enhancement of output power.

View full abstract

In thermoelectric generation applications, the two indispensable conditions are the hot source and the cold source to provide the temperature difference for the generator. Thus, the waste heat recovery from various high temperature gas or steam turbines on ships by thermoelectric generators (TEG) is promising because the ocean naturally plays a role as an infinitely large cold source. Among other options, a pilot study of the applicability of thermoelectric generation to the boiler section of marine power plants is presented through CFD (Computational Fluid Dynamics) modeling. It is found that more than 600 W power may be produced from the waste heat of a 300 kW boiler but without an obvious loss of the system safety.

View full abstract

The reliability of lead-free electronic assemblies after board-level drop tests was investigated. The effects of different PCB (Printed Circuit Board) surface finishes, viz. ENIG (Electroless Nickel Immersion Gold) and ENEPIG (Electroless Nickel Electroless Palladium Immersion Gold), after reflow and thermal aging (1,000 h at 125°C) were studied. The increase of IMCs (Intermetallic Compounds) thickness after thermal aging in all of boards. However, as the change of the thickness of the IMC in the ENEPIG board before and after thermal aging was smaller than that of the ENIG board. The results of the drop test, ENEPIG board has greater reliability after reflow than the ENIG board and shows excellent characteristics under all conditions after thermal aging.

View full abstract

The Zn-In-Sn-O (ZITO) transparent conductive oxide (TCO) films were deposited onto indium/glass substrate by co-sputtering system. The bias-crystallization mechanism (BCM) was used to promote the quality of ZITO films. After biasing treatment (biased at 4 V for 20 min), the resistivity of ZITO film reduced from 3.08×10⁻⁴ Ω*cm to 6.3×10⁻⁵ Ω*cm. This reduction was attributed to the indium ions diffused into ZITO film using BCM. According to the Joule’s law and Ohm’s law, the required energy of biasing treatment was only 480 Joule. Comparing with traditional annealed treatment (annealing at 500°C for 20 min in vacuum required 9.8×10⁶ Joule), BCM had improved the conductivity of ZITO film in a short time at room temperature and possessed an excellent competitiveness of cost.

View full abstract

The dynamic electropulsing induced basal-texture evolution in an AZ61 magnesium alloy was studied by scanning electron microscopy, and backscattered electron microscopy techniques. It was found that electropulsing reduced residual stress inside the rolled magnesium alloy AZ61, which resulted in decreases of both twins and non-basal slips. Electropulsing improved mechanical properties of the alloy. The mechanism of the electropulsing induced texture evolution is discussed from the point of view of electropulsing dynamics.

View full abstract

The thermodynamic treatment, which is based on the difference of heat of formation among three extreme cases for the substitution of a quaternary element X, was applied to predict the substitution behavior of quaternary elements in Ni₃(Si,Ti). The heat of formation of a hypothetical ternary compound Ni₆SiTi in which X elements substitute for relevant sites was calculated by using a geometric model based on an extended Miedema’s theory. According to the prediction, Cr and W (6), Mn and Re (7), Fe and Os (8), Co and Ir (9), Pt (10), and Cu and Au (11) substitute for Ni atoms. Ge (14) substitutes for Si atoms. Zr and Hf (4), V, Nb, and Ta (5), Mo (6), and Al (13) substitute for Ti atoms. Ga (13) substitutes for Si or Ti atom. The prediction for Ta is consistent with the reported experimental result. Also, the solubility limits of quaternary elements for the Ti site in Ni₃(Si,Ti) are ranked in the sequence of Ta > Nb > V > Hf > Zr, and correlated with the size misfit parameter between Ti and the quaternary element X, and the difference in heats of formation between Ni₆SiTi and Ni₆SiX.

View full abstract

The dynamic friction properties of the extruded AZ31 magnesium alloy with the initial average grain size of 15 μm were investigated by the ring compression test at 473 and 523 K and in a strain rate range from 1.0×10⁻² to 3.0 s⁻¹. Two types of the tool, WC-Co tool (WC) and WC-Co coated with diamond like carbon tool (DLC) were used. At 523 K, few differences in terms of the friction coefficient were observed due to the difference with or without DLC. At 473 K, the friction coefficient for the sample deformed by DLC tool was smaller than that done by WC tool. The investigation of the texture near the surface of the tested work pieces with different tools reveals that the integration degree of the grains within 10 degree from ⟨0001⟩ direction to compressive axis in the sample deformed by the DLC tool was smaller than that done by WC tool. It was concluded that the larger friction could enhance alignment of the planes perpendicular to the compressive direction to the basal plane even if under same testing condition.

View full abstract

A study of the effect of chemical composition on microstructure and hardness of the as-cast and homogenized Zn-Al-Cu alloys was carried out. Five different composition alloys were prepared and they were homogenized at 623 K for 648 ks in order to eliminate the dendritic structure. Rockwell “B” hardness was determined in the as-cast and homogenized alloys. XRD diffraction analysis of the as-cast and homogenized alloys indicated the presence of the α, η, ε, θ, τ′ and β phases and α, η, ε, θ, and τ′ phases, respectively. The hardness of both the as-cast and homogenized alloys increased with the increase in volume fraction of the Cu-containing ε, θ, and τ′ phases. A multiple-linear regression analysis permitted to obtain the two equations, HRB_As-cast=97.5+6.8ln(at%Cu)-4.7ln(at%Zn) and HRB_Homogenized=52.1+3.6ln(at%Cu)-27.5ln(at%Zn), to assess the hardness in the as-cast and homogenized Zn-Al-Cu alloys.

View full abstract

Twin types in a room-temperature compressed magnesium alloy (Mg-3Al-1Zn) sample were identified by using electron backscattered diffraction (EBSD) technique, and the results indicate that most of the twins are {10\\bar12} twins and only a few of them are {10\\bar11} twins. In order to study the law of atomic motion in the {10\\bar11} twinning, we calculated the displacement vectors of the twinning atoms in the {10\\bar11} twinning and found that the atomic motion can be explained through a model named quadrangular prism-shaped atomic group (QPAG). In the QPAG model there exist two types of alternately distributed QPAG units totally. Though the rotational angle of the two types of QPAG units in the {10\\bar11} twinning is smaller than in the {10\\bar12} twinning, the relative displacement magnitude in the {10\\bar11} twinning is larger than in the {10\\bar12} twinning due to its more complicated atomic motion, and this should be the reason that the {10\\bar11} twinning is harder to occur than the {10\\bar12} twinning.

View full abstract

In conjunction with experimental simulation of metal forming, the development of model materials, by which forming simulation can be carried out at a low stress level at room temperature, was performed. The model materials are mixtures of microcrystalline wax, rosin, mineral oil and powder. The flow curves of the model materials show three typical configurations, i.e., work-softening type, steady state deformation type and work-hardening type, which are observed in metals and alloys. The above configurations of the flow curves of the model materials could be changed and controlled by adjusting powder content. The flow curves of the model material could be predicted accurately using the work-hardening rate equation determined in this work. As an application example, experiments on and visio-plasticity analyses of the plane strain backward extrusion of magnesium alloy and its model material, which represent the deformation property of work-softening type materials, were carried out. We confirmed that the material flow and strain conditions in both materials correspond to each other with sufficient accuracy for engineering purpose.

View full abstract

The effects of restricted slip conditions on both the Taylor factor and plastic work rate under the condition of tensile yielding have been analyzed in α-titanium alloys at low temperatures, using the full constraints model. The role of secondary slip systems, i.e., the ⟨a⟩ basal slip and ⟨c+a⟩ pyramidal slip, was clarified, when the ⟨a⟩ prismatic slip was dominant. Although no influence of secondary slip conditions on the Taylor factor was detected, the plastic work rate was sensitive to the operating secondary slip systems. When the basal system was chosen as the secondary slip system, the plastic work rate increased in all tensile axes, especially around ⟨0001⟩. In addition, no basal slip operation decreased the plastic strain energy. The plastic work rate was the highest along the ⟨0001⟩ tensile axis, and the operation of the ⟨c+a⟩ pyramidal slip was necessary to achieve plastic deformation along c axis. High elastic strain energy, therefore, must accumulate to a high level around ⟨0001⟩, because the pyramidal slip is hardly active owing to its very high critical resolved shear stress.

View full abstract

A hybrid molecular dynamics/coarse-grained-particle (MD-CGP) method is proposed for dynamic simulation of crack growth at finite temperatures. In the present method, the MD method is applied for the non-linear elastic region such as the crack tip and dislocation core, while the CGP method is applied for the surrounding linear elastic region. For coupling the atomistic and coarse regions, extra atoms and particles are placed, respectively, beyond the interface of the atomistic and coarse systems. They move according to the Langevin-type equation. The dissipation term in the Langevin-type equation contains the velocity difference between the atomistic and coarse systems. Hence, the coupling is achieved through the damped oscillation of the difference between the two systems. It is shown in a one-dimensional simulation that the present hybrid method achieves the non-reflecting boundary condition at the interface for the entire wavenumber range at finite temperatures. Two-dimensional crack growth simulations are performed using both the present hybrid MD-CGP method and full MD method for accuracy check. In the hybrid simulation, the location of the atomistic region shifts to follow the moving crack tip. In spite of such drastic operations, the results obtained by the present hybrid simulation agree very well with those by the full MD simulation. The hybrid MD-CGP method allows us to simulate very large systems without losing atomistic information at the singular point and non-linear region, with much lesser degrees of freedom than required for the full MD method.

View full abstract

The crevice corrosion resistance in high chloride and high acidic solution at high temperature in Ti-15Mo-5Zr and Ti-15Mo-5Zr-1Fe alloys and the tensile properties at ambient temperature in Ti-15Mo-5Zr-1Fe alloy were investigated in this study. The crevice corrosion resistance in Ti-15Mo-5Zr alloy with a Mo equivalency of 18.2 mass%, which was previously reported to show a combination of the high yield strength and the significant uniform elongation, was almost twice as high as that in Ti-15Mo alloy when the bond order (Bo) increased from 2.8126 to 2.8232. A linear correlation between the crevice corrosion resistance and the Bo was confirmed in the Ti-Mo base alloys with the Bo between 2.7900 and 2.8232. Although the high crevice corrosion resistance, Ti-15Mo-5Zr-1Fe alloy with a Mo equivalency of 21.2 mass% showed high yield strength but negligible uniform elongation due to the deformation by dislocation slip. This study suggested that the two parameters of the Mo equivalency and the Bo are useful for an optimization of strength, ductility and corrosion resistance in Ti-Mo base alloys.

View full abstract

The compressive deformation behavior and damage characteristics of ultrafine-grained (UFG) pure titanium produced by equal channel angular pressing (ECAP) and coarse-grained (CG) pure titanium were investigated and compared at temperatures ranging from 77 K (−196°C) to 873 K (600°C). It was found that the compressive stress-strain response and deformation damage morphologies exhibit quite different features for the UFG-Ti and CG-Ti, strongly depending upon the testing temperature. Different from the case of CG-Ti, the stress-strain curve of UFG-Ti exhibits a distinctive stage of strain softening, as the temperature is below recrystallization temperature (e.g. 77 K (−196°C) ∼423 K (150°C)). The yield stress and maximum flow stress of UFG-Ti are contrarily lower than those of CG-Ti, as the temperature is above recrystallization temperature. As compared to CG-Ti, UFG-Ti seems to exhibit more superior high-temperature deformation ability and a comparable low-temperature deformation capacity. The corresponding microstructural changes after compressive deformation of UFG-Ti and CG-Ti were also examined by TEM observations to interpret their differences in deformation micromechanisms.

View full abstract

The distribution of micro/nano-indentation hardness and microstructures of deformed Hadfield high manganese steel have been investigated by means of micro/nano-indentation tests, and optical and electron microscopic observations. Indentation tests demonstrated that there exists a very non-uniform distribution of hardness, with a hardness variation of ∼30% in different grains and in different regions of the same grain. Microscopic observations indicated that the large non-uniformity of micro/nano-hardness is caused mainly by the underlying non-homogeneous substructures (twins, dislocations, etc.), which are closely associated with the non-uniform work hardening in the deformed Hadfield steel, while the effects of the austenite grain boundary and the grain orientation of the indentation plane are not significant.

View full abstract

A novel method for iron removal from aluminum by electroslag refining using KCl-NaCl-Na₃AlF₆ flux containing P was studied. After electroslag refining, the Fe content in commercial purity aluminum decreased from 0.48% to 0.30 mass%, and the mechanical properties of commercial purity aluminum were improved, especially in tensile elongation increased by 33%. XRD and TEM analysis of the sludge indicated that the reaction between the melt and the molten slag to form Fe₂P in the electroslag refining process was the main reason for iron reduction. The thermodynamic phase diagram calculation for Al-Fe-P system accounts for the formation of Fe₂P theoretically in the electroslag refining process.

View full abstract

Fe₇₂B_14.4Si_9.6Nb₄ metallic glass particles and pure Fe particles were separately dispersed into the pure aluminum by the friction stir processing. The microstructure and mechanical properties of the stir zone were analyzed using XRD, SEM, TEM and Vickers hardness tests. As a result, it was found that the Fe metallic glass and pure Fe particles can be uniformly dispersed into the pure aluminum by friction stir processing and the mechanical properties of the stir zone can be improved due to the formation of precipitates.

View full abstract

Tungsten carbide-silicon carbide (WC-SiC) composites were pressure-sintered with a resistance-heated hot-pressing machine at a sintering temperature of 1600°C. The dense sintered bodies were obtained by the SiC addition ranging from 2–10 mol%. Below 4.85 mol% SiC, WC grains grew abnormally, exhibiting high aspect ratios and intersecting one another. There were no preferential orientations for the abnormal WC grains, which had an irregular plate-like morphology with a thickness of about 3 μm and lengths ranging from 50–100 μm. The Vickers hardness decreased with increasing SiC up to 4.85 mol% and increased above this concentration. The Vickers hardness in the range of 2–4.85 mol% SiC was much lower than that of pure WC, 25.3 GPa, and had a constant value of 20.5 GPa above 7.5 mol% SiC. The fracture toughness increased with the addition of SiC, but large amounts of SiC decreased the fracture toughness. The fracture toughness of the WC-SiC composites was higher than that of the pure WC.

View full abstract

A novel reactive technique has been employed to fabricate 2.0 mass%TiB₂/70Si-Al composite. The growth behavior of primary Si phase in the 2.0 mass%TiB₂/70Si-Al composite was investigated when the composite was heated in its semi-solid state. Both theoretical and experimental results have shown that the in-situ TiB₂ particles can refine effectively the primary Si phase and restrain the Si phase growth. The coarsening rate constant of the 2.0 mass%TiB₂/70Si-Al composite was calculated as 3.69×10⁻¹⁸ m³/s, which is less than that of 70Si-Al alloy (7.6×10⁻¹⁷ m³/s), suggesting that the in-situ TiB₂ particles can effectively pin the grain boundaries and arrest the migration of liquid film when the composite was heated in its semi-solid state.

View full abstract

The aim of this study was to elucidate the relationship between the surface roughness and osteoconductivity of anodized titanium surfaces. Before anodizing, titanium substrates with different surface roughness were prepared by wet-polishing. These substrates were anodized at various voltages in H₃PO₄, H₂SO₄, and NaOH aqueous solutions, and their surface roughness was controlled simultaneously at the micron level. Surface roughness of these coatings was expressed with the arithmetical means (Ra). The osteoconductivity of anodized samples was evaluated by in vivo tests. In in vivo tests, samples were implanted in rats’ tibia for 14 d. Anatase type TiO₂ films were formed on all of the anodized samples for in vivo tests. It was newly found that TiO₂ film with small Ra value exhibited high osteoconductivity than that with high Ra value, especially when Ra value was <0.3 μm. In addition, the osteoconductivity of anodized samples with Ra/μm >0.3 was not improved by anodizing, showing the same low osteoconductivity of as-polished samples. These tendencies were observed for all of the TiO₂ films regardless of the type of electrolytes.

View full abstract

In the focus of selective recovery of indium from waste flat panel display, we have studied chlorination treatment where ammonium chloride, NH₄Cl, has been used as chlorination reagent. Glass plate on which ITO is deposited, denoted hereafter as ITO glass, has been employed as model sample. It was found that indium could be successfully recovered from ITO glass in the form of volatile indium chloride by heating the mixture of ITO and NH₄Cl at the temperature of 400°C under inert atmosphere. The influence of process parameters, such as treatment temperature, milling condition of ITO glass and composition of NH₄Cl, was investigated in order to achieve high process efficiency.

View full abstract

This study attempted to investigate the high temperature tensile deformation behaviour of new Al-1%Mg-1.1%Si-0.8%CoNi heat resistant aluminium alloy. New aluminium alloy strengthened by Co-Ni based phase was manufactured by using powder ball milling and continuous casting, based on the alloy design & preliminary test. High temperature tensile tests were conducted at various temperatures from 298 K to 723 K. OM, SEM, EPMA, XRD, FIB and HR-TEM equipments were used to analyse microstructure, phases, and fracture surface. Microstructure of the new alloy mainly consisted of Al matrix and Co-Ni based phases (1∼8 μm). The Co-Ni based phase was analyzed and confirmed as (Ni, Co)₃Al₄ having incoherent interface with matrix. In high temperature tensile results, the new aluminium alloy didn’t show significant decrease (19.6%) of strength with increasing temperature (723 K), suggesting totally different behaviour vis-a-vis conventional A319 alloy (87.0% decrease of T.S.). Fractography observation results of new alloy represented the ductile fracture mode with dimples. Voids were mainly initiated at Co-Ni based strengthening phases. It was apparently observed that the strengthening effect of the (Ni, Co)₃Al₄ could be still maintained at high temperature of 723 K. The deformation mechanism of this alloy was also discussed.

View full abstract

Al-Mg-Mn cast plate was friction stir welded at different rotational speeds for studying the thermal stability of FSWed specimen. As-FSWed specimens possessed a typical fine grain structure, 5.5 μm at 450 rpm, 9.5 μm at 650 rpm and 12.8 μm at 850 rpm could be acquired. But for the specimens as raised up the rotational speed to 850–1650 rpm exerts little effect to the coarsening of grain size. On the other hand, a subsequent thermal exposure from 350 to 500°C for FSWed specimens will cause significant growth of fine dynamic recrystallization grains, especially as the rotational speed decreased to 450 rpm for the fixed traverse speed, 0.55 mm/s. Tensile properties revealed that extreme grain growth after thermal exposure at 500°C deteriorated the workability of the weld zone. It should be noted that a stored energy release by 300°C pre-annealing heat treatment was beneficial for avoiding extra grain coarsening. In this study, the optimum rotational speed for improving tensile properties pertaining to microstructural thermal stability could be recognized as 850 rpm.

View full abstract

Agglomerated coarse Al powders consisting of nanoparticles were synthesized by low energy ball milling process, and subsequently their structures were characterized in terms of agglomeration size, shape, and porosity depending on various milling time, ball size, and ball to powder weight ratio in order to optimize the process parameters. A higher milling time caused a decrease in the agglomeration size and their shape tends to become spherical while reducing the pore sizes. The agglomeration size was also reduced as the ball to powder weight ratio increased and the ball size decreased. The partial cold welding of the nanoparticles at lower milling time and fully cold welding of the nanoparticles at higher milling time were correspondingly responsible to produce larger and smaller agglomerations, respectively.

View full abstract

This study investigated changes in the chemical properties of carbonated waste cement, including the phase transformation, gel polymerization, and specific surface area, as well as cation exchange capacity (CEC) and the adsorption ability of heavy metal ions (Cr⁶⁺ and Cu²⁺). Highly crystalline calcite and highly polymerized silica gel with a three-dimensional network were found to form in carbonated waste cement. The specific surface area and the CEC of waste cement increased with an increase in the carbonation percentage. In addition was a linear relationship between the specific surface area and the carbonation percentage of the waste cement. When the carbonation percentage of waste cement was 35%, the CEC of the carbonated waste cement reached approximately 22 meq/100 g (The unit of [meq/100 g] is milliequivalent per 100 gram. The unit indicates the concentrations of electrolytes.). The increase of the CEC confirmed that carbonated waste cement could adsorb heavy metals.

View full abstract

The warping deformation along grain boundaries has been found for thin plates of Cu-1.8 mass%Be-0.2 mass%Co and Cu-1.8 mass%Be-0.2 mass%Co-0.03 mass%Mg alloys aged at 593 K for 3 h after cold rolling to 0% and 20% reduction, but not been detected for the two alloys aged at the same condition after cold rolling to 90% reduction, by surface roughness measurements. The aging produces γ′ precipitates in grains and discontinuous precipitation (DP) cells at grain boundaries in the two alloys after 0% and 20% cold-rolling, but no DP cells in the alloys after 90% cold-rolling. The addition of Mg or the increase in cold-rolling rate decreases the width of DP cells, resulting in reduction in the degree of warping deformation. The warping deformation along grain boundaries can be attributed to the difference between the length changes of the DP cell and the grain interior by the aging.

View full abstract

In this paper, the new transparent conductive material, Mg(OH)₂-C is analyzed by an ab initio quantum chemical calculation based on the density of states (DOS) with DV-Xα calculation. In this study the calculation of DOS for Mg(OH)₂ by DV-Xα calculation with Mg(OH)₂ cluster model was carried out first to assure the validity of our calculation. Next, it was hypothesized that Mg(OH)₂-C is modeled with MgOHOC cluster as well as the Mg(OH)₂ cluster. The expected behavior of the MgOHOC DOS well agrees with the experimental results for Mg(OH)₂-C, and the hypothesized MgOHOC model well explained the characteristics of the Mg(OH)₂-C. Moreover, replacing a part of the H atoms with C atoms in some of nonconductive hydroxide materials yields conductivity as well as our MgOHOC, because the reason of the MgOHOC conductivity appearance is the one by the replacements from the OH bond to the OC bond and the characteristics of Mg atom doesn’t especially take the part of the conductivity appearance.

View full abstract

This study provides new findings on the effects of blade speed (300 versus 450 rpm) using a three-blade flat impeller during dry powder granulation within a high shear mixer. It was possible to achieve roping behavior, which is recommended for achieving good liquid distribution and nucleation, with flat blades at two different impeller speeds.

View full abstract

The paper demonstrated the electrochemical corrosion properties of the oxide film of AZ91 Mg alloy subjected to plasma electrolytic oxidation (PEO) coating in an electrolyte containing zirconia and additional heat treatment. Surface observation revealed that a number of zirconia particles were successfully incorporated and were also uniformly distributed throughout the oxide film. After subsequent heat treatment, the relative fraction of Mg(OH)₂ decreased whilst the fraction of MgO increased in the oxide film due to the dehydration reaction at 423 K. From the results of electrochemical impedance spectroscopy, the excellent corrosion resistance of AZ91 Mg alloy could be achieved via PEO coating together with annealing treatment. Electrochemical response underlying corrosion response of the present alloy was discussed in relation to equivalent circuit model.

View full abstract

Plates of AISI 304 stainless steel were gas metal arc welded under the effect of an electromagnetic interaction. Samples of the heat affected zone were subjected to the double loop electrochemical potentiokinetic reactivation technique to evaluate the degree of sensitization (DOS). The as-received plates had a significant DOS whereas samples welded under electromagnetic interaction presented lower DOS as compared with samples plainly welded. The reduction in the DOS suggests that the electromagnetic interaction enables Cr redistribution in the austenitic grains during welding reducing Cr depleted zones.

View full abstract

Large amounts of silicomanganese slag are generated and discarded from the silicomanganese alloy smelting furnaces that treat ferromanganese slag to produce silicomanganese alloy, which contain 10–14 mass% Mn. It is thus important to find a possibility for recovering manganese from silicomanganese slag in terms of environmental and economic points of view. Upgrading of manganese from the silicomanganese slag for recycling the slag back to the silicomanganese furnaces must be necessary to decrease the slag volume which causes irregularities in their operation. In this study, a physical separation process for the upgrading of manganese from silicomanganese slag discarded has been suggested. The process first grinds silicomanganese slag between −500 μm and +75 μm, followed by the dry magnetic separation process to separate and concentrate manganese from the ground slag. Based on the results obtained, a manganese rich slag which contains over 20 mass% manganese was calculated to be separated and concentrated from silicomanganese slag under a magnetic field of about 6,000 Tesla using the proposed process. The manganese rich slag obtained should be used as a manganese resource for manufacturing silicomanganese alloy.

View full abstract

304 austenite stainless steel plate and HSLA steel plate were subjected to vacuum rolling cladding (VRC). The microstructure characteristic and properties of the clad interface were investigated in detail. During the VRC process, the clad interface was held at a high vacuum all the time, resulting in significantly decreased oxidation at the interface. A small amount of very fine oxide particles (diameter<0.5 μm) can be found at the clad interface, and no obvious defects were observed. The remarkable diffusion of Ni and Cr elements led to the formation of a transition zone with high hardness. The shear strength of the clad interface was as high as 487 MPa, and the fracture occurred at the HSLA steel near the transition zone. No cracks were found at the clad interface after the 180° bending tests with both outside and inside manners.

View full abstract

Superelasticity at temperatures between 77 K and 273 K in Cu-17Al-15Mn alloy was investigated. In this alloy, where no thermally-induced martensitic transformation appears, an excellent superelasticity with recovery strain of 8.5% was confirmed at 77 K. The critical stresses for stress-induced martensitic transformation decrease with decreasing temperature and its gradient becomes smaller at low temperatures due to the decrease of entropy change. The entropy change estimated at 77 K is −0.46 J/(mol·K), which is almost one-third of that at 221 K.

View full abstract