The purpose of this study was to estimate the microbial properties of titanium and its alloys from two viewpoints: bacterial adhesion and antibacterial effect in vitro. The adhesion of oral bacterium, Streptococcus mutans (S. mutans) MT8148, on Ti, Ti-6Al-4V, and Ti-56Ni surfaces, was investigated by the scintillation counting of radioactivity of bacteria labelled with radio isotope. On the other hand, the influences of the materials on bacterial growth were determined by the optical density of bacterial suspensions. The numbers of bacteria adhered to Ti, Ti-6Al-4V, and Ti-56Ni were larger than that to glass and no differences among the materials at 7.2 ks (2 h). The number of adherent bacteria to the materials at 86.4 ks (24 h) was larger in Ti than in Ti-56Ni. No difference in relative growth of the bacteria among the materials was observed.

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It has been widely recognized that stainless steels may be subjected to localized corrosion by influences of microorganisms in seawater or river water as Microbially Influenced Corrosion (MIC). In this study, the effect of the surface treatment of stainless steels on the MIC behavior in the aerobic aqueous environment was investigated. The corrosion potentials and the polarization curves were measured on the polished, passivated, electropolished and electrolyzed specimens in the simulated MIC test solution. The corrosion potential ennoblement of the specimen electrolyzed in Fe(III)Cr(VI) containing solution was slight compared with other tested specimens and had high corrosion resistance in the natural seawater. The specimen suppressed the cathodic reaction in the polarization measurement. The surface film had a double layer structure which was composed of an Fe hydride outer layer and a Cr oxide inner layer. It was also made clear that the Fe(OH)₃ membrane was anion selective and Cr₂O₃ membrane adsorbed MoO₄²⁻ ions was cation selective from the results of membrane potential measurements. The cathodic polarization reaction of the bipolar membrane which consisted of the anion selective membrane in the outer layer and the cation selective membrane in the inner layer was suppressed, and it was corresponded to the cathodic polarization curve of the specimen electrolyzed in an Fe(III)Cr(VI)-containing solution. From these results, it can be considered that the surface film formed by electrolyzing is the bipolar membrane which suppresses the cathodic reaction. This surface film has high MIC resistance even if the cathodic reaction is accelerated by the aerobic bacterial metabolisms.

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It is known that iron-oxidizing bacteria (IOB) enhance corrosion of metals. But the influences of corrosion on IOB are still uncertain. The purpose of this study is to examine the effect of metal surface condition on the behavior of IOB.
The surfaces of Cu, Ni and SUS304 steel were observed by AFM (atomic force microscope) after 24 h immersion in water including IOB at pH 3. On the surfaces of Cu and Ni, corrosion was induced and many cells of IOB adhered. On the surface of SUS304 steel, corrosion was not induced and a few cells of IOB were observed.
The surfaces of SUS304 steel were observed by AFM after 48 h immersion in water including IOB at pH 2. Cells of IOB on the sites where no corrosion occurred did not segment. However, most of cells of IOB close to pits or intergranular corrosion sites segmented. Therefore, it seems that the corrosion activated IOB.
According to the above, the result is as follows:
1. IOB tend to adsorb on corrosion site.
2. IOB are activated by corrosion.

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The failure in the weld joint occurred in as little as, two months from the start-up of the sewage treatment plant. At the beginning of the failure analysis, crevice corrosion was considered as the main reason since the welding defects. But, the estimated corrosion rate of the welds was too fast. Then, metallurgical failure analysis to understand this behavior was carried out. Finally, it was concluded that the localized corrosion on the welds was a kind of Microbiologically Influenced Corrosion (MIC).
The first stage of a laboratory scale test using the stainless steel welds and the residual liquid obtainable from the MIC -affected effluent treatment plant was performed.
The test samples were exposed in the liquid and kept in an incubator at constant temperature. Corrosion pits were found on 316L, 308N (0.2 mass% nitrogen approximately) and 308 weld metal. The colonies of bacteria several μm in size near the corrosion pits were observed and the types of the bacteria was identified. The evaluation test of corrosion ability of the identified bacteria was planned. MIC susceptibility of the stainless steels used was evaluated.

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Recycling of materials is a key technology for environmental burden reduction or natural resources conservation in materials production. However, the energy consumption and environmental burden associated with recycling are frequently subject to be very severe. Thus, it is very important to evaluate the performance of the recycling process by obtaining quantitative information in which the condition is the best for covering the original purpose of recycling. This work is to propose a new assessment model for metal production and a recycling system. The model consists of three processes, smelting of ore, cascading of metal scrap and upgrading of metal scrap, and the present approach is to assess the total energy consumption of the metal production system, by introducing two equations for describing the relationships between the critical impurity content and the mass of production or scrap recycling. The upgrading process is requested in cases in which the content of the impurity should be reduced due to the quality demand of the corresponding metal market. According to the model, the total energy consumption in the metal production system can be described as a function of recycling rate and performance of the upgrading process. Model calculation was conducted using the cases of the aluminum and steel production process. The results suggest that the impurity removal efficiency and yield in the upgrading process are essential to reduce the energy consumption in these metal production systems. Especially, such points should be explicitly controlled in the aluminum recycling process. The potential capability of this model may not be overemphasized. It is rather surprisingly effective for the development of beneficial recycling of metals by obtaining several quantitative information required for the process design and its control.

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Fe cluster dispersed Fe-Cu granular films have been produced by an ionized cluster beam (ICB) technique. Magnetoresistance (MR) and magnetic properties were observed for Fe-Cu films produced at different acceleration voltages (V_a=0 and 2.5 kV). The chemical composition of the films prepared at V_a=2.5 kV is Fe-richer than the designed one, indicating the “resputtering” of Cu atoms from the deposited films. These films exhibit giant magnetoresistance (GMR), which does not saturate even at high fields: conduction-electrons suffer spin-disorder scattering. With increasing Fe concentration, the MR values of these granular films monotonically decrease, whereas those of the sputtered and thermally evaporated films show maxima at around 25 at%Fe. The disappearance of the MR maximum is ascribed to the presence of antiferromagnetic Fe clusters. In addition, the MR values of the ICB-deposited films prepared at V_a=2.5 kV are higher than those at V_a=0 kV, indicating that the former is smaller in the average cluster size than the latter.

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The dynamics of grain boundary movement is analyzed in two and three dimensions by constructing an atomic jump model. The driving force for the movement is obtained from the decrease of the grain boundary surface energy due to the reduction of the surface area. By considering the diffusion-like atomic jump across the grain boundary, the moving velocity is represented in a form of exp (-1/r), where r is the radius of the curved boundary. The model is applied to the description of the shrinkage behavior of an isolated spherical particle. When r is large, the simulation of the shrinkage behavior gives the nearly same results with the conventional parabolic law of grain growth. The present model also predicts the existence of the critical temperature at which the movement of grain boundary stops. The moving velocity increases with increasing temperature, until it reaches a maximum at a certain temperature and then starts decreasing to zero near the critical temperature.

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The effect of trace amounts of NaCl vapor on the oxidation behavior of pure Ti and Ti-6 mass%Al alloy was investigated by thermogravimetry in a temperature range from 923 to 1073 K. Observation and identification of scales were performed. In addition, hardness measurement of the metal substrate beneath the scale was performed. The formation of scales consisting of periodically stacked layers was observed for pure Ti after oxidation in O₂ without NaCl vapor. On the other hand, the addition of NaCl vapor resulted in the formation of scales consisting of a single layer without a continuous crack. The oxidation kinetics for pure Ti in O₂ containing NaCl vapor followed a parabolic rate law, and the oxidation rate increased with increasing concentration of NaCl vapor. The marker experiment showed that the rate-determining step in this parabolic oxidation was outward diffusion of titanium ions through a rutile TiO₂ layer. Therefore, NaCl vapor in O₂ appears to promote the outward diffusion of titanium ions through the scale. The oxidation rate for a Ti-6 mass%Al alloy, whose kinetics followed a parabolic rate law, also increased with increasing concentration of NaCl vapor. However, in the O₂ containing NaCl vapor the oxidation rate for the Ti-6 mass%Al alloy was lower than that for pure Ti. The decrease in the oxidation rate by aluminum addition to titanium seemed to be attributable to the fact that an inner layer consisting of α-Al₂O₃ formed at the oxide/metal interface inhibited the outward diffusion of titanium ions.

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Spark sintered WC-Co-5/10/20 vol%MoS₂ alloys have been developed as self-lubricating cemented carbides. Using these alloys, friction and wear tests are performed in a ring(counterface: WC-22 mol%Co)-on-disk(specimen: WC-Co-MoS₂) configuration in air. The dynamic coefficient of friction in the initial state of the test decreases with increasing MoS₂ content in the specimens. In particular, this value is remarkably decreased by the addition of 5 vol%MoS₂ to the alloy. The weight loss of the specimens shows a maximum value at 5 vol%MoS₂. On the other hand, the weight loss of the counterface material decreases with increasing MoS₂ content in the specimens. It is considered that the weight loss of the specimens is influenced by the following two factors caused by MoS₂ addition. (1) Lubrication effect due to the formation of the film including MoS₂; and (2) Accelerating effect of wear due to the increase of initial sites of fracture by the occurrence of depleted parts of MoS₂ on the surface of the specimens.

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Fabrication of crystalline Al₂O₃ films by the method consisting of ion beam sputtering of the Al target in an oxygen atmosphere and a simultaneous oxygen ion-irradiation toward the specimen surface was carried out.
At 573 K, the simultaneous oxygen ion-irradiation under 120 kV-0.077 A/m² conditions formed γ-Al₂O₃ crystal films, whereas amorphous Al₂O₃ was produced without oxygen ion-irradiation. At 1073 K, the γ-Al₂O₃ crystal was produced without oxygen ion-irradiation. On the other hand, ion-irradiation under 150 kV-0.103 A/m² conditions created the (α+θ)-Al₂O₃ crystal.
The γ-Al₂O₃ and (α+θ)-Al₂O₃ crystals were produced at low temperatures as compared with the conventional procedures such as PVD and CVD. Therefore the enhancement of crystallization of Al₂O₃ film by oxygen ion-irradiation was clarified.
Wear resistance tests using the ball-on-disk method showed that disks coated with crystallized Al₂O₃ films had higher resistance than the amorphous Al₂O₃-coated and non-coated disks with increasing hardness number.

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The film structure of Al-doped Fe-Ta-C magnetic thin films prepared on a single crystal Mn-Zn ferrite substrate was analyzed by high resolution TEM and an X-ray diffraction method.
The as-deposited Al-doped Fe-Ta-C magnetic thin films prepared after sputtering a Cr layer on a single crystal Mn-Zn ferrite substrate are crystalline. The as-deposited Cr underlayer is crystalline. These as-deposited magnetic thin films show a (100) Fe texture and are found to be composed of fine Fe grains by TEM obserbation. But epitaxal growth of Fe grains is not obserbed near the Cr surface. The magnetic thin film near the Cr surface is composed of microcrystals and these crystal grains are growing to the surface of the magnetic film. By annealing, the crystal orientation does not change. The Fe crystal grain size of the magnetic thin film after annealing is 6∼10 nm in diameter, and that of TaC is 1∼2 nm in diameter. A decrease in soft magnetism is due to the (100) Fe texture. The as-deposited magnetic film prepared on a SiO₂ underlayer film on the surface of a single crystal Mn-Zn ferrite substrate is in the amorphous state. After annealing, this film shows the (110) Fe texture and exhibits good soft magnetic characteristics. When a crystalline film is prepared on a ferrite substrate, the amorphous underlayer such as SiO₂ is useful for controlling a preferred orientation of the film.

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Rutile-type TiO₂/Al composites have hardenability due to the reaction between components by heat treatment in the solid state. It has been found that the reaction on the solid state is induced by impurity element in reinforcement such as Na, and the hardenability is considered practically useful. In the present work, for the purpose of defining the role of impurity on the reaction and of seeking for effective other impurities, the reactivities of various kinds of TiO₂/Al composites were examined by DSC and their reaction mechanisms were investigated. The composites were fabricated from pure Al and TiO₂ particles which were doped with small amounts of alkali or alkali-earth metal oxides. When the TiO₂ powder was doped with Na, K, Rb, Cs, Ca, Sr and Ba, the TiO₂/Al composites revealed an exothermic peak in the DSC curve at about 873 K. But the peak by the reaction in the solid state could not be observed in the case of the dopants of Li, Be and Mg. It was also found that the exothermic peak of the composites in the solid state was higher with increasing ionic radius of the dopants. It can be fairly certain that the dopant which induces the reaction forms an oxide complex on the surface of TiO₂, but not diffuses into TiO₂. From the experimental results, it can be considered that the oxide complex plays the role of a diffusion path of the Al ion to promote the reaction between TiO₂ and Al. The reaction mechanism of the composites in the solid state is explained by the formation of the oxide complex and the crystalline structure, which is produced on the surface of TiO₂ powder as alkali or alkali-earth metal oxides and by the diffusion behavior of the Al ion through the oxide complex and into the TiO₂ particle.

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Soft magnetic properties of Fe-38 mass%Ni-8 mass%Cr alloys are extremely influenced by a small amount of sulfur(S) and oxygen(O) in the alloys. In the cases of low S(≤9 ppm) and low O(≤24 ppm), the soft magnetic properties are as high as those of Fe-78 mass%Ni alloys. When the S content is more than 9 ppm or the O content is more than 24 ppm, however, they are substantially deteriorated. In this paper, the effects of a small amount of S and O on the soft magnetic properties of Fe-38 mass%Ni-8 mass%Cr alloys have been examined from a practical point of view. The results obtained are summarized as follows: After annealing at 1100°C in a dry hydrogen atmosphere (dew point: −45°C), the soft magnetic properties of an alloy containing high S(S=23 ppm) and an alloy containing high O(O=38 ppm) are inferior to those of a pure alloy (S=8 ppm, O=18 ppm). In the alloy containing high S, many MnS particles whose sizes are mainly smaller than 0.5 μm are precipitated. In the alloy containing high O, many oxide inclusions whose sizes are mainly 0.26∼0.75 μm exist. It is considered that in the alloy containing high S, the MnS precipitates whose sizes are smaller than 0.5 μm little interfere with domain wall displacement, while they interfere with grain growth. Thus, the alloy containing high S is inferior to the pure alloy in the soft magnetic properties. On the contrary, it is considered that in the alloy containing high O, the oxide inclusions whose sizes are larger than 0.5 μm interfere both with domain wall displacement and with grain growth. Therefore, the alloy containing high O is much inferior to the pure alloy in the soft magnetic properties. The results may indicate that the domain wall thickness of Fe-38 mass%Ni-8 mass%Cr alloys is about 0.5∼1 μm.

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