Important contributions of high resolution transmission electron microscopy (HRTEM) using many-beam techniques in the determination of atomic-scale structure of a variety of materials are reviwed. In particular, the key roles of HRTEM in the structure analysis of oxide superconductors are emphasized presenting experimental results of direct identification of cations and oxygen vacant sites. The achievement of HRTEM in the studies of alloy structures is described with particular attention to incommensurate modulation, short-range order and local lattice distortion associated with phase transitions. The capability of computer-aided signal processing is discussed in connection with interpretation of HRTEM images taken with diffuse scattering. HRTEM studies of zeolites are also briefly presented. In view of future prospects, it is highly desirable that recording apparatuses of HRTEM image provide higher sensitivity, higher quality and higher quantitative ability than those available traditionally.

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Melt atomization is almost only the production method of alloy powders and has come into use for various spray-form types due to their P/M applications. P/M materials are usually qualified by both alloy design and powder characteristics for the P/M industrial use, especially in the production of high alloy powders.
Extensive merits reducing chemical segregation, refining crystal grain and precipitates, producing supersaturated or amorphous solid solutions for alloy design can be obtained by applying these powders. Typical atomization methods (water-, gas- and centrifugal atomization) are reviewed in terms of their principles, operation parameters, the related powder morphologies together with P/M applications.

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The thermoelastic martensitic transformation undergone in shape-memory alloys is considered to be thermodynamically reversible. However, the existence of irreversible heat dissipated is made evident in the special case of several Cu–based alloys which display a complex transformation from b.c.c. to a mixture of 18R and 2H martensites. The simultaneous growth of both the martensites is suggested as the main responsibility for the irreversible behaviour. In this sense, as a first approach, the entropy production associated to the irreversible heat is related to the degree of coexistence, and shows a maximun for a structure consisting of 50% 18R and 50% 2H.

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Pseudoelastic behavior and electric resistivity changes during a tensile straining-unloading sequence were observed in a polycrystalline Cu–Zn–Al shape memory alloy (SMA), at various temperatures above A_f. The results were compared to those predicted on the basis of the ‘modified’ Taylor scheme and data from single crystals in regard to the yield stress, resistivity changes with strain and stress hysteresis. The scheme has been demonstrated to be successful in predicting the yield stress of polycrystalline SMA, although some disagreement was noticed between the observation and the prediction. Similar disagreements were found in the results other than yield stress, and they tended to be larger with increasing test temperature. They were consistently interpreted as a result of the formation of an auxiliary martensite other than that found in single crystals. The present scheme is useful in relating the pseudoelastic behavior of single and polycrystalline SMA quantitatively to each other, and also in providing information on deformation mechanisms which participate exclusively in the deformation of polycrystalline SMA.

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Creep tests and high temperature tensile tests were carried out on the coarse-grained dispersion-hardened Al–Al₂O₃–Zr alloy which had an anisotropy of strength due to the recrystallization texture. Three types of specimens were used for the tests, each of which had a specimen axis orientation of 0, 45 or 90 degrees against the rolling direction, respectively. Relations between the critical stress for creep deformation and the proof stress were examined.
The existence of critical stress for creep deformation, σ_c, was recognized at temperatures from 573 to 773 K. The specimens of 0 degree orientation had the highest critical stress and creep strength, and the specimens of 90-degree orientation had the lowest ones. It was shown that the creep deformation could be explained as being controlled by the self-diffusion of Al when it was taken into account that σ_c decreases with the rise of temperature. The temperature dependence of σ_c was thought to be due to the interaction between dislocations and impurity atoms which segregated on the interface between dispersed particles and the matrix. Ratios of σ_c to the 0.1 and 0.01% proof stresses at room temperature, which were thought to be a criterion of the Orowan stress, were in the range from 0.5 to 0.8. Each ratio was nearly constant at the same temperature independent of the axis orientation. The ratio decreased gradually with the rise of temperature, which showed that the interaction between the dislocations and the dispersed particles changes with the rise of temperature.

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TiN coupons coated with Al₂O₃ films of about 2.6 μm formed by a chemical vapor deposition technique were oxidized in a purified oxygen flow at atmospheric pressure in a temperature range 1073 to 1273 K. The film is protective at 1073 K for at least up to 185 ks. Though the film decreases the oxidation rate at the other temperatures, it shows breakaway kinetics. The time before breakaway, t_b, increases as the film thickness increases, while it decreases as the oxidation temperature increases. During the oxidation a small number of rutile aggregates grow on the film, while porous massive rutile grows under the film. The mass gain due to the oxidation after t_b corresponds mainly to the growth of the massive rutile, implying enhanced transport of oxygen into the substrate. The oxidation rate is higher than that of alloys which form α-Al₂O₃ scales as a rate-limiting layer. This difference is explained in terms of structural changes. A possible reason for the breakaway is also given in terms of the formation of gaseous products, such as nitrogen and nitrogen oxide, which can introduce mechanical defects in the film.

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The effects of high concentration CO and CO₂ on the hydrogen permeation characteristics of the palladium membrane have been investigated using pure H₂, H₂-10%CO, H₂-50%CO and H₂-50%CO₂ in the temperature range of 423 to 723 K and the pressure range of 0.9 to 250 kPa. The feed and bleed gases were analyzed using a quadrupole mass spectrometer. The surfaces of the samples were analyzed by means of Auger electron spectroscopy. The deterioration of the hydrogen permeability and diffusivity in the palladium membrane was observed in the case of using H₂–CO(10%,50%)gases below 523 K and showed a concentration dependence of CO, while only a slight deterioration was observed in the case of using a H₂-50%CO₂ gas below 473 K. The results can be explained in terms of the difference in the adsorption energy of CO and CO₂ at the palladium surface. The deterioration in hydrogen permeability by the contaminant gases can be attributed to the decrease in effective area for H₂ dissociation by the weak adsorption of CO.

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Equilibrium distribution ratios of Cu(II) between sulfuric acid solutions and xylene solutions of Acorga P-5100 as a β-hydroxyoxime extractant have been measured in the range of initial aqueous Cu(II) concentrations from 25 to 500 mol/m³. In order to explain the data based on the law of mass action, a model has been described with special attention to the aqueous phase formulation, wherein Pitzer’s estimation equations for free activity coefficients of the ions in the aqueous phase are employed. The apparent extraction constant has been determined as logK_e=1.73±0.09, enabling us to predict the distribution ratios with excellent accuracy. A comparison with the previous study has shown that this model is consistent among nitrate, chloride and sulfate systems. Ratios of the activity of Cu(II) to the square of the activity of the hydrogen ion in the H₂SO₄–CuSO₄–H₂O system have been compared between estimated values and literature data. The result supports the effectiveness of Pitzer’s equations as a tool for the prediction of equilibrium distribution ratios.

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Nb₃Al superconducting wires were successfully fabricated by a newly developed method, in which thin chips of Nb sandwiched by Al were used as a starting material. The fabrication process and the effects of several factors on the critical current density are presented. An optimized heat treatment yields J_c of ∼10⁸ A/m² at 4.2 K and 18.8T, T_c of 17 K and B_C2^* of 23.2T at 4.2 K. A further increase in J_c can be expected, since there is no evidence of saturation of it with increasing reduction ratio. This method having advantages of good workability, relatively low reduction ratio and simplicity of processing seems to be straightforward to the practical processing of the Nb₃Al wire.

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Partial structure factors of GeO₂ glass are estimated from the anomalous X-ray scattering data at the Ge K absorption edge and the conventional neutron diffraction results, and calculations of the partial radial distribution functions are presented for Ge–O and O–O and Ge–Ge pairs.

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A low pressure casting of a La₅₅Al₂₅Ni₂₀ melt into a copper mold was found to bring about an amorphous bulk in cylindrical or sheet form. The maximum diameter of the amorphous cylinder and the maximum thickness of the amorphous sheet with a width of 5.0 mm were about 3.0 and 2.3 mm, respectively. In comparison with the thermal properties of a melt-spun amorphous La₅₅Al₂₅Ni₂₀ ribbon, the amorphous bulks had a higher onset temperature and a smaller heat evolution of irreversible structural relaxation, but there was no distinct difference in glass transition and crystallization behavior. Thus, the amorphous phase produced by casting had a more relaxed atomic configuration as compared with that for the melt-spun ribbon, but there was no difference in the specific heat curves during reheating for both of the samples heated up to the supercooled liquid region. This is believed to be the first evidence that amorphization takes place by casting into a copper mold. The amorphization allows us to reconfirm an extremely large glass-forming capacity of the La–Al–Ni amorphous alloy as previously found by the present authors.

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Microstructure and magnetic properties of Fe–rich Fe–Hf alloy films produced by rf sputtering have been investigated as a function of Hf content. The films in the concentration range 1–6 at%Hf have a nonequilibrium bcc phase with fine grains of 5 to 20 nm and exhibit high saturation magnetization and soft magnetic properties. In particular, the bcc Fe_95.6Hf_4.4 film annealed at 673 K for 3.6 ks exhibits a saturation magnetization of 1.9 T and an effective permeability of 1800 at 1 MHz.

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