ISIJ International
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ONLINE ISSN: 1347-5460
PRINT ISSN: 0915-1559

ISIJ International Vol. 29 (1989), No. 3

  • Energy Dispersive X-ray Microanalysis in the Analytical Electron Microscope

    pp. 179-190

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    DOI:10.2355/isijinternational.29.179

    A review is made on the quantitative microanalysis of thin samples in the analytical electron microscope (AEM) with the energy dispersive spectrometer (EDS). This review is concerned with a basic approach to the quantification and some applications to Ni base alloys.
    Covered first are the simplicity of the ratio method for the microanalysis of the samples and the importance of the experimental determination of k-factors needed in the ratio method. The way to estimate the effects of X-ray absoption and fluorescence is described by having examples from two typical Ni base alloys. For the correction of absorption, two methods are raised; one is the extrapolation method and the other is the differential X-ray absorption (DXA) method, both of which do not require the thickness measurement. Application to a unidirectionally solidified Ni-Al-Mo elutectic alloy is demonstrated, where the calculation of the minimum mass fraction (MMF) is included. Finally, a simple technique is shown to identify the particles of which sizes are smaller than the electron probe size.
  • Higher Order Laue Zone Patterns in Convergent Beam Electron Diffraction and Determinations of Local Lattice Parameters in α- and α2-phases of a Cu-20at%Al Alloy

    pp. 191-197

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    DOI:10.2355/isijinternational.29.191

    In order to clarify the applicability of higher order Laue zone (HOLZ) patterns in convergent beam electron diffraction to the determinations of local lattice distortions in two-phase alloys, we discussed experimental conditions affecting the accuracy, and observed HOLZ patterns of a Cu-20at%Al alloy, in which small particles of α2-phase with one dimensional long period superstructure are precipitated in the matrix of fcc α-phase. It was shown that the accuracy is affected by specimen thickness as well as beam direction, and that lattice parameters along the [100] and [010] axes can be determined from a [114] HOLZ patterm with an error less than one part in a thousand. The [114] HOLZ patterns were obtained both from small regions in α-matrix and α2-particles. Slight changes in lattice parameters were detected as a function of position with a high spatial resolution.
  • Structural Characterization of Non-crystalline Materials by the Anomalous X-ray Scattering (AXS) Method

    pp. 198-208

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    DOI:10.2355/isijinternational.29.198

    The fundamentals of anomalous X-ray scattering (AXS) and its potential power have been described with respect to the determination of the local chemical environment around a specific element as a function of radial distance in multi-component non-crystalline materials. The usefulness of this relatively new method using the anomalous dispersion effect of X-rays has been demonstrated by some selected examples of GeO2 oxide glass, Al–Ge–Mn metallic glass, and Bi2O3–CaO–Fe2O3 thin film oxide glass grown on a Si substrate. The feasibility study for crystalline materials by applying this AXS method was also given using the results of a high temperature oxide superconductor of Y–Ba–Cu–O, as an example.
  • Crystal Growth of the High-Tc Superconductor in the Bi–Sr–Ca–Cu–O System

    pp. 209-212

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    DOI:10.2355/isijinternational.29.209

    Small disc-like grains of the low-Tc (80 K) phase in Bi-based superconductors grow to larger, plate-like crystals of the high-Tc (110 K) phase during heating at the temperature higher than 870°C. In the SEM images of polished sections some phases other than the superconductive ones are observed always in the process of the crystal growth. According to the EPMA measurement they are identified as following three; Ca2CuO3, in which about 8% of Ca are substituted by Sr, (Sr1–z, Caz)3Cu5Ox (Z≅0.4), in which less than 2% of Bi is involved, and CuO. They show different colour under optical microscope. Based on the sequential change in their fraction it may be considered that Ca2CuO3 and/or (Sr1–z, Caz)3Cu5Ox react with the matrix low-Tc phase to produce the high-Tc one.
  • Characterization of Oxide Superconductor by Means of X-ray Diffractometry and X-ray Absorption Near Edge Structure

    pp. 213-222

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    DOI:10.2355/isijinternational.29.213

    A new class of copper oxide superconductors, Y–Ba–Cu–O and Bi–Sr–Ca–Cu–O systems are investigated by using X-ray diffractometry (the Rietveld analysis) and X-ray absorption measurements (XANES) with a special attention to Cu–O configurations. It is shown that a significant difference of the Cu–O configuration is directly related to superconducting properties in both systems.
    (1) In the Y–Ba–Cu–O system, the structure of superconducting orthorhombic phase is characterized by a linear alignment of Cu–O as well as its planar network. The degree of linear ordering of oxygen atoms causes a continuous change both in a structure from tetragonal to orthorhombic phase and in the electronic state of copper atom.
    (2) In the Bi–Sr–Ca–Cu–O system, some superconductor phases are present. Each phase has its peculiar critical temperature Tc. The crystal structures contain a planar network of Cu–O and the sequence of the Cu–O layers is directly related to Tc. The electronic state of copper atoms in superconductor phase is nearly identical to that of orthorhombic Y–Ba–Cu–O system.
  • Characterization of Porous Silicon Layers by Means of X-ray Double-crystal Diffractometry

    pp. 223-228

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    DOI:10.2355/isijinternational.29.223

    (111) and (100) p-type silicon wafers of 0.55 to 33 Ωcm resistivities were anodized in 50 wt% HF solution and formed porous silicon layers were investigated by using X-ray double-crystal diffraction techniques. The porous layer is shown to be a monolithic single crystal, and its lattice spacing is slightly larger than that of the unanodized substrate, resulting in elastic bending of the wafer. The difference in lattice spacing between the porous layer and the substrate was nearly identical independent of wafer orientation and wafer resistivity. The crystal lattice of porous silicon layer is found to be elastically distorted predominantly in the direction normal to the wafer surface. The lattice spacing of porous layer increased slightly with time and the crystalline quality degraded. The results suggest that stresses, generated by the growth of native oxide layers on pore surfaces, are responsible for the elastic lattice distortion of porous layer. It is also shown tht the crystalline quality of the porous layer produced on the (111) wafers appears superior to that of the (100) wafers for all the wafer resistivity studied.
  • Microstructure-PTCR Property Relationships in PbTiO3-TiO2 Ceramics

    pp. 229-233

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    DOI:10.2355/isijinternational.29.229

    Niobium doped PbTiO3–TiO2 ceramics show PTCR properties at the Curie temperature of PbTiO3 (490°C). This paper describes the relationships between PTCR characteristics and the microstructure of PbTiO3–TiO2 ceramics. PTCR properties depend on the firing conditions that vary the microstructure of PbTiO3–TiO2 ceramics. The PTCR properties disappear when TiO2 grains are connected each other from one end of the sample to the other. The resistivity–temperature characteristics of the interface between PbTiO3 and TiO2 grains are directly measured. It is found that PTCR characteristics are originated at the interface between PbTiO3 and TiO2 grains. On the basis of this idea, a new type of PTCR PbTiO3–TiO2 ceramics with the boundary layer structure is proposed.
  • Microstructural Characterization of Plasma-sprayed Oxide Ceramics

    pp. 234-239

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    DOI:10.2355/isijinternational.29.234

    Microstructural and microchemical characterization has been carried out on plasma-sprayed zircon (ZrSiO4) and alumina-chromia (Al2O3–5wt%Cr2O3) by transmission electron microscopy and energy dispersive X–ray analysis. The as–sprayed zircon coatings consist of zirconia and silica glass as a result of phase separation during rapid cooling in the plasma–spraying process. Zirconia shows a tetragonal structure for small particles and a monoclinic for large particles. The zircon coatings annealed at 1 300°C for 96 h in air show a mixture of zircon and monoclinic zirconia phases. Alumina–chromia coatings plasma–sprayed with N2 gas consist mainly of a polycrystalline alumina–chromia solid solution with a typical grain size of 0.4 μm. Fine precipitates are observed frequently along the grain boundaries in the coatings sprayed with Ar–H2 gas mixture or N2–H2 gas mixture. The fine precipitates are a metallic Cr–rich Cr–Al alloy formed by reduction of Cr2O3 and Al2O3 during the plasma-spraying process. These precipitates disappear during annealing at temperatures higher than 1 300°C for 96 h in air. The precipitates affect the wear resistance of the coatings.
  • Evaluation of Fracture Toughness and R-Curve Behaviour of Y-TZP Ceramics

    pp. 240-245

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    DOI:10.2355/isijinternational.29.240

    The fracture toughness of tetragonal zirconia polycrystals containing 2 and 3 mol% Yttria (Y-TZP) were evaluated by 4 measuring techniques which included (1) Double Cantilever Beam (DCB), (2) Vickers indentation technique by direct measurement of radial cracks or Single Indentation Technique (SIT), (3) from the strength dependence of the Vickers indentation load and crack length or the so called Modified Indentation Technique (MIT), and (4) Single Edge Pre-crack Beam (SEPB). There were considerable differences of K1c value between the different techniques with these being exaggerated for 2 mol% Y-TZP material. It was found that SEPB and DCB techniques gave the most conservative and consistent estimates of K1c. The SIT technique was very sensitive to the indentation load for 2Y-TZP, estimates of K1c decreasing with increasing load. It was found that K1c increased with the ratio of transformation zone size to crack length. Recommendations for determination of K1c of TZP materials are made. R-Curve behaviour and K1c in various environments were determined by the DCB technique. The monoclinic content of different specimen surfaces including as-sintered, as-polished and fracture surface have also been analysed by X-ray diffraction.
  • Characterization of Surface Segregation and Selective Oxidation of Manganese in Fe–30Mn–9Al Alloy with Auger Electron and Secondary Ion Mass Spectrometry

    pp. 246-252

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    DOI:10.2355/isijinternational.29.246

    Surface oxidation of an Fe–30Mn–9Al alloy has been performed in the temperature range between 295 and 671 K at low oxygen exposures from zero to saturation coverages under ultrahigh vacuum conditions. Chemical composition changes in the thin oxide layers formed during the oxygen uptake have been measured by means of Auger electron spectroscopy and the nature of the initial oxidation by secondary ion mass spectrometry. Preferential enrichment and oxidation of aluminum occurs at room temperature with concurrent depletion of iron from the surface layer. On increasing the temperature without oxygen exposure, enrichment of manganese in the surface layer becomes predominant above about 400 K. Oxygen exposure of the surface results in the formation of oxide layers of which the outermost part is enriched in manganese. It is shown that the manganese oxide formation at high oxygen pressures inhibits the formation of the protective aluminum oxide scale resistant to high temperature oxidation of Fe–Mn–Al alloys.
  • High Resolution and Analytical Electron Microscopy Study of Si3N4-Ni Bonded Interface

    pp. 253-258

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    DOI:10.2355/isijinternational.29.253

    A detailed characterization of the ceramic-metal interface was carried out for a Si3N4-Ni system bonded in vacuum at 1 273 K. High resolution electron microscopy and analytical electron microscopy were used in the characterization of the interface. Reaction products such as nickel silicides were not present at the interface. It was demonstrated that Si3N4 reacts with Ni in accordance with the solid-state reaction mechanism proposed in this study. The final reaction product is thought to be Ni with Si and N in solid solution.

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