Material recycling occurs naturally when there are market incentives. When the economics of recycling is only marginal, government and institutional incentives are required. Here a simple framework for graphically representing the “cost-quality” dynamics of recycling is presented. Examples of policy and technology approaches are outlined based upon a recent study of several OECD countries \\citerf1 In addition large scale trends for these countries show the complex effects of wealth (GNP per capita) on recycling.

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It is required to develop innovative materials technology for environmentally benign manufacturing toward dematerialization. Recently, some barrier-free processes in a variety of materials such as steels, light metals, polymers, woods have been studied from the viewpoint of recycling for scraps and materials selection for poison-free materials, and forming for high performance materials. The present paper reviews the contents of the barrier-free processing. The key technologies of the barrier-free processing are the synthesis of harmless materials from scraps by dispersion control and the simultaneity of forming and microstructural control by in-process control.

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The most serious problem in the recycling of steel is the occurrence of surface hot shortness during hot deformation due to the mixing of Cu from scrap into steels. Tin accelerates the effect of Cu. The surface hot shortness is caused by liquid embrittlement, that is, formation of the liquid Cu-enriched phase through preferential oxidation of Fe atoms at the steel/scale interface during heating for hot deformation and penetration of this Cu-enriched phase into the grain boundaries. Decrease in the amount of the liquid Cu-enriched phase penetrating into grain boundaries can suppress the surface hot shortness. The amount of the liquid Cu-enriched phase penetrating into the grain boundaries can be reduced by the suppression of oxidation, occlusion of the Cu-enriched phase into the scale, back-diffusion of Cu into the steel matrix and suppression of penetration of the liquid Cu-enriched phase. Therefore, the effects of various elements and conditions of heating and deformation on the surface hot shortness, oxidation, amount of the Cu-enriched phase at the interface and the penetration were examined by tensile tests at high temperatures, thermogravimetry and optical microscopy. The conclusion can be summarized as follows. Silicon, Mn, S (+Mn) and B reduce the susceptibility to the surface hot shortness through decreasing the amount of Cu-enriched phase at the steel/scale interface. The effect of Si is significant. Carbon reduces the oxidation rate in LNG combustion gas. Phosphorus, Si, B and C reduce the susceptibility to the surface hot shortness through restraining the penetration of the Cu-enriched phase into grain boundaries. Heating at higher temperatures reduces the susceptibility mainly through a reduction in the amount of the Cu-enriched phase at the steel/scale interface, although the loss of steels by oxidation increases. A large grain size accelerates the surface hot shortness. A small amount of H₂O in air significantly accelerates the surface hot shortness. Effects of H₂O in heating atmosphere depend on the steel composition and more detailed research on this is desired. Very slow deformation does not cause liquid embrittlement through dynamical re-crystallization, while at a fast deformation rate the embrittlement is suppressed by an increase in the critical stress for the liquid embrittlement. Multiple methods using physical metallurgy suggested by the present research for suppressing the surface hot shortness should be applied together with other methods through separation, smelting and design of fabrication in order to promote the recycling of steels.

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Deformation and fracture mechanism during tensile testing is investigated for consolidated Fe–Cu alloy. Fe–Cu rapidly solidified powder in which copper is supersaturated is consolidated using groove rolling. Copper content, rolling temperature, and heat exposure condition are varied to obtain samples with various microstructures. The samples are subjected to tensile testing; some tests are suspended to observe the microstructure change during loading. The tensile behavior and the microstructure are correlated based on the obtained stress-strain curves and SEM observation. The difference of the stress-strain curve is explained from the morphology change of the microstructures and the following change of the microfracture behavior during loading.

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Cast strips of 0.1 mass%C steels with phosphorus contents ranging from 0.01 to 0.2 mass% have been produced by using a twin drum type continuous casting machine, and their microstructures have been characterized. Fine dendrite structure in the strips provides a fine dispersion of the segregated phosphorus regime. Phosphorus addition changes the α grain structure dramatically and decreases the γ grain size. The EPMA (Electron Probe Micro Analyzer) mapping and the diffusion analysis of phosphorus in the γ phase indicate the presence of a retained δ phase in the austenite temperature. The pinning effect of the δ-ferrite on the γ-grain growth must be kept in the temperature range of the rapid γ grain growth. The balance of strength and ductility for the cast strip is improved as the phosphorus content increases.

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The feasibility of intelligent utilization of iron-aluminum scraps is explored in this work. Through adding aluminum which is contained in the scraps to cast iron, the changes in wear resistance, heat resistance and damping property of aluminum-alloyed cast irons were systematically investigated. Superior properties were obviously manifested in the cast irons with certain aluminum contents. Iron-aluminum mixed scraps are expected to be utilized as a raw material for high quality cast irons.

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Aiming for actual dematerialization, mass flow must be optimized to make full use of the recyclable materials as input and to reduce total amount of wastes. Since the material efficiency is strongly dependent on their adaptivity to the design demand for recycled products, an effective recycling process must accompany the advanced materials processing and manufacturing to improve their original properties to the level above the demand. In the present paper, the light-mass non-ferrous metallic alloys such as aluminum alloys are targeted, to utilize their bulk wastes, which are often ejected from the electric parts or members, as an input material, and to aim for their reuse as an automotive part. Dense, high-strengthened aluminum alloy compact, or, green materials are handled in the present forming and manufacturing up to the final net-shape formation of products by sinter-forging. Selection of reused materials and in-process improvement of their properties are essential keys in this barrier-free processing. Possibility to replace the conventional processing with this barrier-free process lies in: (1) Reduction of in-process energy and mass consumption, (2) Flexibility to yield various kinds of products without any realignment of processes, and (3) Adaptive in-process material modification to design for products in practical use.

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A solid-state recycle processing for magnesium alloy waste has been developed by combining cyclic plastic working and direct hot forging under the short thermal explosion. AZ91D machined chips, which were employed as wasted materials in this study, were consolidated to the green compact with fine microstructures via bulk mechanical alloying (BMA) process, where the compaction and forward extrusion in the closed die were repeated at room temperature. To keep fine microstructures after hot forging, that is, to prevent from the matrix softening due to the grain and/or intermetallic growth, the thermal damage on the green compact in pre-heating before forging was controlled by using the infrared gold image rapid heating furnace. The hot forged AZ91D alloy showed superior mechanical properties such as hardness and ultimate tensile strength (UTS) to the cast one used as input raw materials. The same effects were recognized in the case of wasted Al–Si alloys via this process. The developed solid-state recycle processing revealed a possibility to improve the mechanical properties of the consolidated light alloys even in employing their wasted materials.

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As a candidate for the alternate of conventional, insoluble thermosetting resins that are matrix components of fiber reinforced plastics (FRP), soluble and heat-resistant aramids (wholly aromatic polyamides) were synthesized. To obtain rigid biphenyl-containing aramid, one-step procedure from dihalobiphenyl and aromatic diamine by palladium-catalyzed carbonylation-polycondensation was successfully applied. Reaction parameters, such as base, solvent, palladium-phosphine catalyst and CO pressure in the reaction of 2,7-dibromo-9,10-dihydrophenanthrene (1) and 4,4^′-diaminodipheyl ether (2a), were very important for successful synthesis. They affected the molecular weight of resulting aramid significantly. Under optimum conditions, poly[amino-1,4-phenyleneoxy-1,4-phenyleneaminocarbonyl(9,10-dihydro-2,7-phenanthrenediyl)carbonyl] (3a) was obtained in 99% yield with high molecular weight (polystyrene equivalent M_w=128100). The procedure was applied to some other diamines. The aramid 3a was heat-resistant and soluble in polar organic solvent. On the basis of thermal analysis, 10% weight loss temperature (T₁₀) of the aramid was 461°C. The tensile strength and tensile modulus were 48 MPa and 1.6 GPa, respectively; these properties are roughly in the same level as those of conventional unsaturated polyester resin. Judging from the data, aramid 3a is applicable for matrix of FRP. Some other aramids exhibited similar properties.

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The amounts of new wood used for housing construction and wood waste from demolished buildings was calculated using various scenarios of wood recycling. Diverse utilization of waste and increase in reuse rate was found to be effective to reduce the total amounts of final waste and the use of new wood materials. For recycling wood waste, the water vapor explosion (WVE) process was developed. In this process, wood materials were exploded from within by the force of water vapor generated by compression under high pressure and temperature and evaporation of the internal moisture, and they were separated into small wood elements. The WVE process was directly applied to the separation of Sugi (Cryptomeria Japonica) and Karamatsu (Laryx leptolepis) sawn timbers and slabs. The WVE of them produced small wood elements including fiber bundles, strands, and chips at certain experimental conditions (pressure, temperature, and compressing time). Fiber bundles were long, narrow and flexible elements, and it appeared that they could not be obtained by the conventional processes.

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Corrosion resistance and adhesion properties of a chromium–free (poison-free) coating using an urethane-base resin for AZ91E Magnesium alloy have been investigated by salt immersion tests and thermal and humid resistance tests. As a result of the salt immersion tests, the corrosion resistance of the chromium-free coated specimen was almost equal to that of the Chromium-based chemical conversion. Also, the thermal and humid resistance tests showed that no changes were found in the coating with an urethane resin base layer; however, exfoliation was observed in the coating with a phenolic resin base layer. In the coating with an urethane resin base layer, the boundaries between the base layer and the aluminum middle layer were relatively flat and there were no pores, though a lot of pores were observed between the base layer and the aluminum middle layer in the coating with a phenolic resin base layer. Therefore, it is suggested that the good adhesion properties of the chromium-free coating are related to the strong adhesion between the urethane resin base layer and the aluminum middle layer.

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Metal Injection molding (MIM) process is an advanced powder processing technique because of net shaping with shape complexity at low processing energy and 100% material utilization. This study has been performed to clarify and to optimize the relationship between the mechanical properties and the microstructures for the superhigh strengthening sintered low alloy steels (Fe–Ni system) by using MIM process. A 6 mass%Ni MIM steel showed excellent properties of 2000 MPa tensile strength, 5% elongation and 500 MPa fatigue strength. Instead of Fe–Ni, moreover, the Fe–Mn low alloy steel was investigated to obtain high performance properties, because Ni has a harmful influence upon the human body, for example, a Ni allergy.

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Automotive parts produced using a powder metallurgy (P/M) process are commonly used in automobiles because they can be produced without the use of machining and with a special alloy design. This paper describes how the P/M process can be applied to the production of environmentally friendly automotive parts. The paper begins with a discussion on how the utilization of P/M for net-shape manufacturing makes it possible to conserve both energy and materials due to the fact that machining is unnecessary. Evidence is then presented that shows that it is possible to produce warm-compacted automotive P/M parts with sufficient strength even without the use of special alloy elements and/or heat treatments. As a final example, magnet materials made using spark-plasma sintering are described. This spark-plasma sintering process makes it possible to create high-performance magnet parts that are highly energy efficient. Finally, taking into consideration the above-mentioned example, the ideal P/M process is discussed from an environmentally benign point of view.

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Mechanical alloying and pulse discharge sintering (MA-PDS) process was employed to fabricate MoSi₂ alloys with additions of Al, B or Nb alloy elements. Microstructure and mechanical properties of these alloys were investigated. An exothermic behavior was identified during milling. This process is related to the reaction of each element to synthesize intermetallic MoSi₂. The MoSi₂ alloys fabricated by MA-PDS process showed a very fine microstructure compared to that sintered from the commercial MoSi₂ alloy powders. Significant hardness increase was found due to the refinement of the binary MoSi₂ microstructure. Alloys made from powders milled in air show higher hardness compared to those in Ar gas. This was because of the oxides formed during milling process.

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A reliable fabrication process of non-silica glasses is required to suppress crystallization. The crystallization behavior of zinctellurite (ZnO–TeO₂) glass at different rates of heating and cooling were studied by an in situ high-temperature X-ray diffractometer (a rapid measurement system) and differential thermal analysis (DTA). The DTA results compared with the X-ray diffraction data resulted in crystallization and phase relations, during heating and cooling, of the glass. During the heating process, α-TeO₂ and ZnTeO₃ were found to crystallize first, followed by the crystallization of Zn₂Te₃O₈. While during the cooling process from melt, α-TeO₂ was found to crystallize first, followed by the crystallization of Zn₂Te₃O₈. The present study results in reliable data of the crystallization process and presents a possibility of an approach to make accurate T-T-T diagram which can show the crystallization tendency.

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In this paper we examine the product induced material flows through the product manufacturing system. Research strategies to reduce materials related environmental loads based upon this examination are suggested.

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In Industrial Ecology the core idea is to find symbiotic relationships where waste material from one company is being used by other companies and industrial ecosystems are created. Although the idea is simple, fundamental challenges exist related to the quality of the material, stability of the system, etc. A core question is how to assess of the “goodness” of such a system. In this paper, it is shown how ecological input-output analysis metrics can be used to analyze flows.

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In order to develop effective environmentally benign manufacturing and materials processing (EBM) in architecture, concept and procedures of integrated environment-conscious life-cycle design (Eco-LCD) are proposed and reported, for building structural composite materials, and components such as steel reinforced concrete (RC), and continuous fiber reinforced concrete (FRPRC), and/or systems such as external thermal insulation ones (ETI) using short-cut fiber reinforced cement composites (FRC) including thermal insulations as exterior thermal insulation panels.

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Although high performance materials offer many advantages in reducing overall material usage and waste generation, there are limitations that must be addressed to their use. These include problems in materials design, testing and evaluation, manufacturing processing and recycling. These limitations will be discussed.

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Continuous increase of the annual amount of steel scrap generated presents a problem to the sustainability of human society. The effective utilization of scrap is a serious problem to be solved in the near future, and the optimization of the global system of steel production should be considered from various viewpoints, particularly those of environmental load and material efficiency. For the consideration of a global system that contains many different kinds of flow, a criterion for evaluating the efficiency of the system is necessary for optimizing the utilization of materials in the system. The concept of exergy was adopted in this study and the application of exergy analysis to the evaluation of a complicated system was considered. A simulation model was developed for the steel industry in Japan and the exergy analysis of the Blast Furnace-LD converter (BF-LD) process and the Electric Arc Furnace (EF) process was conducted. The exergy loss was expressed as a function of parameters, such as the mixing rate of pig iron in the EF process and the total exergy loss in the system was calculated. The applicability of exergy as a criterion for the analysis of a production process and for evaluating material efficiency was discussed.

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In order to develop a new process of forming a carrier concentration gradient in PbTe only by using heat-treatment, the effect of heat-treatment on a carrier concentration n of the p-type PbTe has been investigated, and the p-type PbTe has been heat-treated using a temperature gradient. The as-grown stoichiometric PbTe was p-type with an n of 1.0×10²⁴ m⁻³. Vacuum thermal exposure with Te-rich PbTe at 900 K for 1 h increased the n of the stoichiometric PbTe to 5.1×10²⁴ m⁻³, which indicates that hole formation was achieved by thermal exposure at this temperature and duration. The thermally exposed stoichiometric PbTe was heat-treated in the temperature range of 400 to 900 K for a period of 24 h. The n decreased with an increasing heat-treatment temperature of between 300 and 500 K, while the n increased with an increasing heat-treatment temperature of between 500 and 900 K. A minimum n was measured at 500 K, above which the formation energy of holes was determined to be 16.4 kJ/mol. On the basis of these results, a 19 mm long thermally exposed stoichiometric PbTe was heat-treated using a temperature gradient of 340–900 K for a period of 24 h. A continuous change in n was formed in the PbTe, and a minimum value of n was determined to be at a position corresponding to the heat-treatment temperature of 500 K. A continuous gradient of hole production was successfully achieved in the p-type PbTe only by heat-treatment using a temperature gradient.

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Regional differences on the strategy against crisis to environment make a common frame invisible to promote the effective directions toward significant reduction of total mass requirement or dematerialization. This overview summarizes the intimate discussions, proposals and advisable comments at the first US-Japan Workshop on the Environmentally Benign Manufacturing and Materials Processing at Hawaii on the October 5th, 2001, in order to integrate the state-of-the-art research activities in both countries. In the discussion over the recyclable materials, value/cost-quality diagram is used to redefine the recycling process and to characterize various processes in the environmentally benign manufacturing. Influence of light-weight material selection on the dematerialization is discussed to find out a new direction. Importance of the trade-off-balancing on the high performance for long term use is reconsidered to search for a solution in the design of innovative manufacturing and materials processing. Mass flow analysis in the life cycle assessment is recognized as a tool to make eco-system design for industrial ecology. Several issues for further research are also argued to promote the related activities to the environmentally benign manufacturing and materials processing.

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Based on the review of ten years progress of ecomaterials’ research and development, a barrier free processing is proposed as a next step of ecomaterials. In the first place, the development of ecomaterial is reviewed. The concept of ecomaterial has been widely spread in the design of materials as life-cycle thinking and has been realized in the various area as a form of consumer material, commodity material and energy-transmission material with the keyword of “hazardous substance free”, “green environmental profile”, “higher recyclability” and “higher materials efficiency”. The importance of the connection of the ecomaterial with DfE (design for the environment) is emphasized as the next step. The existence of the barrier in the material processing technology between ecomaterial-selection and DfE is pointed out. The barrier on the input-flow of the process makes it difficult to use of environmental friendly raw materials. The barrier on the output-flow of the process prevents it from the flexible formability to give the shape to realize DfE. In order to solve those problems, a new research project, named as “Study on the Barrier-Free Processing of Materials for Life-Cycle Design for Environment”, has been launched.

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This paper describes magnetic properties and microwave absorption properties of polymer-protected cobalt nanoparticles. Cobalt nanoparticles were prepared using the thermal decomposition of dicobalt octacarbonyl in ethylene glycol. They were stabilized and dispersed by coexisting with poly(N-vinyl-2-pyrrolidone) (PVP), resulting in an average diameter of 45 nm. The X-ray diffraction (XRD) analysis revealed that the Co-PVP sample synthesized at 170°C for 3 h, with the mole ratio of cobalt:PVP=1:10 (mol : unit mole), consisted of two phases of hcp and fcc cobalt. Their saturation magnetization measured using a vibrating sample magnetometer (VSM) was 1.53×10⁻⁴ Wb·m·kg⁻¹. The compacted sample, produced from the PVP-protected cobalt nanoparticles, showed a reflection loss (R.L.) less than −20 dB at the frequency (matching frequency: f_m) of 0.54 and 0.64 GHz with the thickness (matching thickness: d_m) of 6.16 and 5.04 mm, respectively. Therefore, it is concluded that polymer-protected cobalt nanoparticles have a possibility for the use as microwave absorption materials.

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Ti–Cr–V alloys are known to absorb protium up to H/M=2. However, Ti–Cr–20 at%V alloys with more than 56 at%Cr content were found to absorb up to H/M=1. This paper aims to make clear the effects of compositions on formations of 1, 2 protorides in Ti–Cr–V alloys, and the structure of the mono-protorides. It was found that the mono-protorides with fcc and hcp structures exist. The mono-protoride with the fcc structure was different from the di-protoride with the FCC structure in the lattice constants. Some relationship between appearance of the mono-protorides and disappearance of the plateau regions in low hydrogen pressure regions was considered to exist. As a result, the appearance regions of 1, 2 protorides in Ti–Cr–V alloys were derived.

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Metallic thin films deposited on Si wafers were analyzed by EPMA under grazing-exit geometry. The experimental setup consisted of the conventional SEM and EDX. The exit angle was controlled by moving the EDX up and down. After the SEM observation, the electron beam fixed on the analyzed position. And then, the intensities of characteristic X-rays were measured as a function of exit angle. These angle dependences were analyzed by curve fitting of the simulated curves. As a result, the thickness and the density of thin films were evaluated. The difference of the density of chromium thin films prepared by different methods was found. The GE-EPMA measurement was performed for Au–Ag layers on the Si wafer. The thin-film characterization for each layer was independently performed at localized region on Ag and Au layers.

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The hydriding/dehydriding characteristics of a Mg-rich Mg–Ni–Nd alloy produced by melt-spinning and subsequent annealing have been investigated. This alloy absorbs ∼ 4.7 mass% hydrogen (H⁄M∼ 1.5) quickly between 423 and 573 K and wholly desorbs it at moderate speeds above 453 K. Transmission electron microscope observations and selected-area electron diffraction analyses of this alloy before and after hydriding demonstrate that it consists of multiple phases of Mg₂Ni and Nd-hydride precipitated uniformly in a nano-structured Mg matrix. The fast reaction kinetics is caused by an interplay between a catalytic action of the Nd-hydrides and the surrounding nano-sized Mg grains which quickly store or evolve hydrogen across the interfaces.

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Structures of as-cast and homogenized Ti_75−xAl₂₅Ni_x alloys before and after hydrogenation, the hydrogen content and the hydrogen desorption temperature of the hydrogenated Ti_75−xAl₂₅Ni_x alloys were investigated by a powder X-ray diffractometer (XRD) and a hydrogen analyzer. The hydrogen content of these alloys decreased with increasing Ni content, and was almost independent of the hydrogenation temperature and the structure of the alloys, but 50% hydrogen desorption temperature, T_d, varied widely with them. The formation of amorphous phases raised T_d. On the contrary, a drop in T_d was achieved by hydrogenation of a mixture alloy of the D0₁₉ and C14 Laves phases.

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Recently, sharply reduced magnetic moments were measured in Mn₁₃ and Mn₁₉ clusters with values of about 0.5 \\micro_B/atom, while other clusters had moments of 1 to 1.4 \\micro_B/atom. It was postulated that this sharply reduced magnetic moment results from the icosahedral growth sequence. We confirm the stability of the icosahedral structures. The icosahedral Mn₁₃ and Mn₁₉ clusters have several nearly degenerate low energy states, each with a low magnetic moment. It is shown that the mixture of ferromagnetic and antiferromagnetic coupling is responsible for the low net magnetic moments.

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Pulse discharge sintering (PDS) technique was employed to synthesize the ternary compound Ti₃SiC₂ from four starting powder mixtures. The experimental results demonstrated that when the starting material of 3Ti/Si/2C or 3Ti/SiC/C was used high content of the secondary phase, TiC, higher than 30 mass%, was found in the sintered material. When TiC powder as starting material was used (Ti/Si/2TiC) in the same stoichiometric composition, however, the final sintered product contained low TiC content of a few percent. Further adjusting the composition to the off-stoichiometric of 2Ti/2Si/3TiC, the content of the secondary phase TiC was further controlled to be around 1 mass%. In the materials sintered from Ti/Si/2TiC and 2Ti/2Si/3TiC an optimum sintering temperature exists at 1573 K, at which the highest Ti₃SiC₂ phase purity was achieved. When sintered at the optimum temperature a density of higher than 99% was obtained. At the optimum sintering temperature, both the phase purity and the density of the material sintered from 2Ti/2Si/3TiC showed very little dependence on the sintering time ranging from a few minutes to four hours, indicating the phase stability at this temperature.

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Compressive tests were conducted in vacuum at temperatures up to 1203 K, on the Ti₃SiC₂ samples synthesized from 2Ti/2Si/3TiC powder mixture through pulse discharge sintering technique. The compressive strength of Ti₃SiC₂ compound showed a monotonic decrease with increasing testing temperature. The Ti₃SiC₂ samples displayed obvious brittle fracture behavior at temperatures below 1073 K. When the testing temperature was above 1123 K, obvious pseudo-plastic deformation behavior was observed in the stress-strain curves. At these temperatures, after an initial pseudo-strain-hardening, a decrease in stress follows with further increasing strain. The pseudo-plastic behavior of Ti₃SiC₂ at temperature above 1123 K could be attributed to the basal plane slip, kink-band formation, delamination of layers at local sites, and intergranular cracking. Further increase in strain causes the growth and linkage of microcracks, which gives rise to the reduction of the real area of the cross section of specimen and hence lead to the “strain-softening” phenomenon.

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We have made X-ray and neutron diffraction experiments and magnetic susceptibility measurements for γ-MnPd alloys. The alloy containing 10.5 at%Pd shows a face center orthorhombic structure with a=0.3839, b=0.3780 and c=0.3717 nm and a non-collinear antiferromagntic structure with μ_a=0, μ_b=1.26 and μ_c=2.14 μ_B/Mn atom at 10 K. The crystal distortion occurs from the orthorhombic structure to a tetragonal structure with c⁄a<1 at 320 K, and finally to a cubic structure at 430 K. Another alloy with 13 at%Pd shows a face centered tetragonal with a=0.3800 and b=0.3846 nm (c⁄a=1.012) at 293 K, and transforms to a cubic structure at 350 K. More Pd rich alloy with 15 at% shows [c] structure down to 27 K. A phase diagram for γ-MnPd alloy system with 8–17 at%Pd is proposed.

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The crystallographic structure and morphology of electrodeposited Fe–Cr films under different bath conditions were studied in detail by using XRD, HRTEM and SEM. The crystallographic structures of the Fe–Cr electrodeposits were also compared with the Fe–Cr thermal equilibrium diagram. The results indicated that the crystallographic structure of electrodeposited Fe–Cr alloy film gradually changed from microcrystalline to amorphous with increasing Cr content. The deposited film exists as α-Fe solid solution when the Cr compositions of deposited films are below 3.1 at%, whereas, it existed as a meta-stable crystal when the Cr compositions of deposited films are from 4.5 at% to 22.4 at%, which have not been reported up to now. The deposited films with various Cr compositions from 22.9 at% to 74.4 at% chromium exist as amorphous phase. Hence, the crystallographic structure of the electrodeposited Fe–Cr alloy film is closely related to its thermal equilibrium diagram, but does not always agree with it.

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Using pure Ti powder with particle sizes from 300 to 500 \\micron prepared by the plasma rotating electrode process (PREP), porous pure Ti compacts for biomedical applications were synthesized by powder sintering, and microstructures and mechanical properties of the compacts were investigated in this study. Porous compacts having porosity of 19–35 vol% are successfully fabricated by controlling sintering condition. It is found that Young’s modulus and compressive yield strength decrease linearly with increasing porosity, and porous Ti compacts having porosity of about 30–35 vol% exhibit identical Young’s modulus of human bone.

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L1₂–(Al, Cr)₃Ti/Ti₂AlC composites have been prepared by the reactive arc-melting technique using elemental powders of Ti, Al, Cr, and C. Resulting composites have been reinforced using 4.5, 9, and 18 vol%Ti₂AlC in a matrix of L1₂ trialuminide Ti–61 mol%Al–13 mol%Cr alloy. The Ti₂AlC particles having a rod-like morphology of 1.5 \\micron width and 5–20 \\micron in length were homogeneously dispersed in the matrix. The matrix grain size was reduced through addition of Ti₂AlC particles. These composite materials have revealed higher mechanical properties (bending strength and fracture toughness) than that of the monolithic alloy. This improvement is attributed to the Ti₂AlC particles dispersion and to the fine grain of the matrix.

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Tritium distribution in V–4 mass%Cr–4 mass%Ti alloy has been observed by the tritium radioluminography, and the relation between the tritium distribution and the constituent elements of the alloy have been investigated. In the as-cast specimen, tritium concentration has been higher in the titanium enriched region, that is, the local tritium concentrations at the lower and higher titanium region are 156 and 202 mol ppb, respectively. The tritium distribution has shown a strong correlation with the titanium segregation in the interdendritic region. In the heat treated specimen, the tritium distribution has been rarely affected by the interdendritic titanium segregation. Tritium concentration at the central area and at the surrounding area in the specimen surface have been 209 and 147 mol ppb, respectively. It has been thought that this accumulation of tritium to the central area is caused by the Gorsky effect which generated due to the constraint condition of the stress field in the plate shaped specimen. In the heat treated specimen, the tritium distribution has been more strongly affected by the shape of the specimen than by the titanium segregation in it.

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The substitution of Mn for Fe in the goethite (α-FeOOH) framework and the excess addition of Mn beyond the solid-solubility limit, approximately 1.5 mol%Mn, contribute to the change of adsorptive properties for metal ions, Pb^II, Cu^II, and Zn^II, in aqueous solutions. Removal of Pb^II from the metal solution at pH 4 was enhanced by the excess addition of Mn in the synthetic process for Mn-substituted goethite. This enhancement was caused by the formation of a new composite adsorbent, α-(Fe, Mn)OOH particles with (Fe, Mn)₃O₄ precipitates on their surfaces.

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This paper describes the relationship between hydrogen pressure and temperature (P-T curve) in the HDDR treatment of the Sm₂Fe₁₇ compound. The P-T curve suggested that the HDDR condition of the Sm₂Fe₁₇ compound is more sensitive to temperature than that of the Nd₂Fe₁₄B compound. It was also found that the HDDR treatment of the Sm₂Fe₁₇ compound has to be controlled in the hydrogen pressure range of one order lower than that of the Nd₂Fe₁₄B compound, because of its lower optimum HDDR temperature. Using the P-T curve, new HDDR treatments named v-HD and s-DR, were carried out in order to induce anisotropic feature. However, the normalized remanence of the new HDDR treated powders was around 0.52, which suggested that the powders were almost magnetically isotropic.

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Temperature distributions and thermoelectrical performance of a porous FeSi₂ in a steady state of reciprocatory flow combustion have been examined. The temperature gradient between the hot and the cold side of the elements reached about 200 K/cm, resulting in high output power per density of 226 Wh/m². It has been also found that the incoming gases were preheated by the porous element to a temperature where combustion occurs and exhaust gases transferred the thermal energy to the element before leaving the element. This energy recirculation leads to an extension of the flammable limit for dilute fuel gases, equivalence ratio; φ=0.27. The low conversion efficiency of 0.033% would be attributed to the convective heat loss by the exhaust gases due to the small volumetric surface area inside the porous element.

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Influences of static strain on the damping capacity in Mn-based M2052 and Fe–6Al alloys were studied with the forced flexural oscillation method by using a dynamic mechanical analyzer (DMA). The static surface strain was applied on the 3-point bending specimens in the range of 1.0×10⁻⁵–2.0×10⁻⁴. The damping capacity of the M2052 alloy showed a continuous increase, but that of the Fe–6Al alloy showed a continuous decrease with increasing static strain in the range below 1.0×10⁻⁴. The variation of the damping capacity with increasing static strain was fitted with an exponential function, and the exponential index turned out to be 0.25 and −0.5 for the M2052 and Fe–6Al alloys, respectively. Static strains in the vicinity of 1.0×10⁻⁴ caused the formation of a damping peak, which accelerated the increase of the damping capacity in the M2052 alloy, but softened the decrease of the damping capacity in the Fe–6Al alloy. A significant reduction of the damping capacity appeared at static strains above 1.0×10⁻⁴ in both high damping alloys.

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This paper aims to develop the vanadium free Ti–Cr–X BCC solid solution alloys with high protium content. The effects of additional elements such as Mo, W, Nb and Ta to the phase formation on the Ti–Cr alloys were studied. It was found that Mo-added heat-treated alloys had the flattened plateau regions with the capacity of more than 2.2 mass% protium with maximum of 3.6 mass% protium content, which is equal to that of Ti–Cr–V alloys. It was found that the Ti–Cr–Mo alloys with BCC structure transformed to protide phase with BCC or FCC structure. The plateau pressure of the Ti–Cr–Mo alloys increased with increasing Mo content, but the lattice parameters decreased. The H/M ratio of the alloy with less than 10 at%Mo was 1.8 at 10 MPa hydrogen pressure and was almost unchanged with Mo content.

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The charging effect due to the electron irradiation in spherical SiO₂ particles of 250 nm in diameter has been analyzed by electron holography. Electron holograms of a charged SiO₂ particle on the side surface of the carbon film were simulated taking into account the electric shielding effect due to the carbon film. In order to compare the observed hologram and the simulated holograms quantitatively, the residual index between the observed and simulated images was evaluated. Through the quantitative analysis taking into account the shielding effect with the limited side surface area of the carbon film, the amount of the charge was evaluated to be 3.38×10⁻¹⁷ C for the current density of incident electron beam at 0.24 A/m² without an objective aperture.

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Ta/Si (100) and Cu/Ta/Si (100) film structures were fabricated by using ion beam deposition with a modified RF sputter-type ion source, in which a strong RF discharge was introduced in order to enhance the plasma density. For Ta/Si structures, Ta films were deposited at various bias voltages. When the substrate bias voltage was not applied, the Ta film showed a columnar structure and had a high resistivity of 2600 nΩm. On the other hand, when the substrate bias voltage of −50–−200 V was applied, the cross-sectional observation did not show columnar structure at all. In this case, film deposition was considered to be sufficient migration energy by the accelerated Ta⁺ ions. In particular, Ta films deposited at a bias voltage of −125 V had a very small resistivity of 360 nΩm. Thermal stability of Cu(100 nm)/Ta(50 nm)/Si films, where Ta plays a role of diffusion barrier, was evaluated after annealing in H₂ atmosphere for 60 min at various temperatures. Non-columnar structure Ta films deposited at substrate bias voltages of −50 V and −125 V were found to be stable up to 600°C, while columnar structure Ta films deposited at zero bias voltage degraded at 300°C. This result indicates that the thermal stability of the Ta films is mainly governed by the film microstructure of the deposited layer.

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Ab initio total energy calculations based on the local density approximation (LDA) and the adiabatic approximation has attracted considerable attention as a conceptually new method. It is capable of describing dynamically the stability and reactivity of clusters, surfaces and bulk materials at finite temperatures, in principle, without using any adjustable parameters. Consequently, Ohno et al. have developed the all-electron mixed-basis approach which is applicable to the molecular dynamics of objects in any atomic environment. Titanium Nitride has unique features, such as self-lubricity, high wear resistance, high melting point, and high hardness, and the application to artificial bone and cutting tools, among others, is expected. We calculated optimized structures of titanium nitride micro clusters and compared these with silicon nitride which is tetravalent also. Both TiN₂ and SiN₂ clusters form isosceles triangles. The Ti–N bondlengths in TiN and TiN₂ are much shorter than in the bulk.

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Gold cementation test was conducted without de-aeration by using zinc, copper and aluminium powders from an ammonium thiosulfate solution contained 8 mg/l Au. The amount of metal powder was varied in the range of 30–450 Metal/Gold mass ratio. The solution composition was 1–5 mol/l NH₄OH, 0.01–0.05 mol/l CuSO₄∗5H₂O, 0.2–0.4 mol/l (NH₄)₂S₂O₃ and pH 9.5–10.5. The results indicated that the gold was effectively recovered from a solution of lower ammonia and copper concentrations and higher thiosulfate concentration. The optimum reagent composition for the gold cementation from the ammonium thiosulfate solution was founded to be 1 mol/l NH₄OH, 0.01 mol/l CuSO₄∗5H₂O and 0.4 mol/l (NH₄)₂S₂O₃ at pH 9.5. 100% of gold was recovered by zinc and aluminium powders at a Metal/Gold mass ratio of 30. Copper powder recovered 93% of gold at a Metal/Gold mass ratio of 50. Zinc might re-generate thiosulfate concentration and precipitate most of copper in the solution. Aluminium precipitation might recover gold with less amount of copper deposition and some thiosulfate reduction. Copper precipitation reduced a small amount of thiosulfate concentration and greatly increased copper concentration. Ammonia concentration stayed constant during cementation process.

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Preferential nucleation of dynamic grains at triple junction (TJ) was investigated in copper tricrystal during high-temperature deformation. The nucleation of the dynamic grains at the TJ was observed at much lower strain than the peak strain where dynamic recrystallization (DRX) extensively took place. Further straining caused the incremental nucleation of dynamic grains on sliding grain boundaries accompanied by grain-boundary migration and serration. This occurred also at relatively lower strain than the peak strain. The DRX grains evolved to the most area of the tricrystal when deformed to about the peak strain. The observed preferential nucleation of DRX grains at the TJ was considered with relation of stress and deformation concentration there induced by folding and grain-boundary sliding.

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Experiments were conducted to determine the flow behavior of three materials at ultrahigh temperatures: an Al-6061 composite containing 20 vol% SiC whiskers and unreinforced Al-6061 and Al-1050 alloys prepared by casting. Tensile tests were performed at strain rates up to 5×10⁻¹ s⁻¹ and over a range of ultrahigh temperatures up to and above the temperatures where there is a small amount of liquid phase. High strain rate superplasticity was achieved in the composite material but not in the unreinforced alloys. For all three materials, it is shown that the true activation energy for flow changes from values of <200 kJ mol⁻¹ at the lower temperatures where there is no liquid phase to exceptionally high values in the presence of a liquid phase: these values are up to >1000 kJ mol⁻¹ for the composite and the Al-1050 alloy. It is concluded that exceptionally high activation energies are an inherent feature of flow in materials containing a small amount of discontinuous liquid at temperatures immediately above the onset of partial melting.

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A theory of local dynamics of liquid is developed in order to explain the glass transition and fragility of multi-component alloys as it relates to formation of bulk metallic glasses. Unlike the extended hydrodynamic theories in which liquid is regarded as a continuum body, the present approach focuses on the discreteness of the atomic structure and considers the stability of local topology of the network structure. This approach has led to the prediction of the glass transition temperature, melting and glass formability. We extend this approach to describe the effects of local topology on the atomic transport and glass transition and fragility of multi-component glasses. This theory leads to a picture of a strong liquid as a nano-scale composite of glass and liquid, and suggests compositional requirements for forming bulk metallic glasses.

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The effects of the titanium and oxygen concentration on the characteristics of inclusions and microstructure in low carbon wrought steels were investigated. Increasing the titanium concentration from 48 to 120 ppm promoted the formation of TiN particles and decreased the prior austenite grain size. The fraction of intragranular ferrite in the microstructure was relatively unchanged. When the oxygen concentration was increased from 50 to 130 ppm, the volume fraction and the number of inclusion increased. However, the fraction of intragranular ferrite in microstructures decreased abruptly above 80 ppm because the allotriomorph ferrite phase at the prior austenite grain boundary began to form.

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In the present work it has been found that the room temperature impedance of La_0.7Sr_0.3MnO₃ increases with increasing ac frequency from 7.38 to 110 MHz. The room temperature magnetoresistance ratio (R(0)–R(H))⁄R(0) for La_0.7Sr_0.3MnO₃ can reach 31.4% with H=4.92×10⁵ A/m at a frequency of 68.27 MHz. The frequency dependence of magnetoimpedance, as well as magnetoreactance and magnetoresistance, were investigated in detail.

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