This article describes results of the residual stress measurements in different iron alloys using a few non-destructive techniques based on X-ray diffraction. It was shown that the results provide useful information for understanding the microstructural phenomenon in each alloy, although these techniques are not universally applicable to various cases. In this paper, the residual stresses formed during stress-induced martensitic transformation and its reverse transformation in shape memory alloys, the residual stresses balancing between two phases in duplex stainless steels and the residual stresses formed by inhomogeneous plastic strains in polycrystalline twin-induced plasticity steels are shown. It is important to select an adequate method according to the phenomena and properties of interest in iron alloys. The residual stresses formed in a high-entropy alloy containing iron are also presented, taking into account into the inhomogeneity in bulk. The residual stresses and related microstructural data in materials in structures and device components are considered to be effective parameters for evaluating their mechanical properties. While modern diffraction measurement methods are relatively easy to be operated, it is noted that the results include issues related to the microstructure of the materials. These issues should also be discussed in the residual stress measurements at different scales, and reliable fundamental data related to residual stress considering the microstructure would be necessary for discussion.

A spectral measurement system using a sub-THz source in the bandwidth up to 100 GHz, obtained by multiplying and amplifying a frequency-variable signal in the GHz band operated by a silicon semiconductor device, was constructed in conjunction with a frequency-tunable single-frequency THz source using GaP, which has been developed previously, in a transmission and reflection optical arrangement. The absorption spectra of ferrous corrosion products and the reflective imaging of metal fragments hidden behind concrete plate were measured. These results of the sub-THz and THz waves suggest that the interior of building structures can be inspected non-destructively based on the dielectric constant-based absorption and reflection of corrosion products and metals inside the concrete and metal surface under coating respectively, which have a high transmission property.

Identifying a crystal structure of alumina (Al₂O₃) scale is critical for evaluating the performance of heat-resistant alloys because α-Al₂O₃ is stable and protective against high-temperature oxidation and corrosion but θ- and γ-Al₂O₃ provide poor oxidation resistance. Conventional methods to identify crystal structures of Al₂O₃ scales are time-consuming. Herein, the author proposes a method to rapidly identify crystal structures of Al₂O₃ scales on β-NiAl by obtaining their cathodoluminescence (CL) spectra. α-, θ-, and γ-Al₂O₃ can be identified by detecting a sharp peak at 695.8 nm and 686.3 nm, and a broad peak at around 700 nm, respectively, in CL spectra. Concentrations of α-, θ-, and γ-Al₂O₃ scales can be determined roughly from intensities of these peaks. This method can be applied to areas ranging from the millimeter to micrometer scale, and the acquisition time for the CL spectra was less than 10 s. The results indicate that obtaining CL spectra contributes to the identification of crystal structures of Al₂O₃ scales on heat-resistant alloys and a reduction in time to evaluate the performance of heat-resistant alloys.

Blistering occurs when oxide scale swells during oxidation at steel high temperatures. Blistered scale causes surface defects when steels are rolled. An assumption has been proposed that the pressure of CO and CO₂ gas generation beneath the scale causes blisters. This study the qualitative measurements of the gas pressure beneath the oxide scale were tried. A stainless tube was set in order to connect to the beneath the scale during oxidation. Positive pressures were confirmed beneath oxide scale. Also gas permeability through FeO mono-layer scale was obtained.

The environmental resistance of pure iron was evaluated with oxygen and hydrogen sensor installed after the oxidation furnace. The amount of introduced oxygen was precisely controlled by oxygen pump-sensor at the front stage of the oxidation furnace and the reaction with hydrogen was analyzed. As a result, when oxygen was supplied, a reaction between hydrogen and oxygen occurred, but when sufficient oxygen was not supplied, a hydrogen-vapor environment was created and oxidation was not accelerated. However, when the amount of supplied oxygen was excessive, the environment became oxygen-water vapor environment and the oxidation was accelerated. At that time, it was clarified that the oxidation by oxygen was dominant under the oxygen-water vapor environment, and the mass gain increased. In addition, the border of the region dominated by oxygen oxidation and that by steam oxidation was clarified by precisely controlling the amount of supplied oxygen by the oxygen pump-sensor.

To understand the anisotropy of properties in FeCo-V alloy sheets, the Young's modulus, texture, and residual stress of samples of different treatments were investigated using the X-ray diffraction method. In the cold-rolled alloy sheets, the anisotropy of Young's modulus in different directions within the sheet plane was similar to that of the annealed samples at 600 °C, although there was some variation. The anisotropy of the Young's modulus was different from that of the cold-rolled and annealed samples at low temperatures. According to the results of texture measurements on alloy sheets subjected to each treatment, the direction of the lower Young's modulus almost corresponds to a specific texture component, suggesting that the texture component affects the anisotropy of the Young's modulus. X-ray diffraction rings from alloy sheets are used in the residual stress measurement, which may contain information on the process of alloy sheets and changes in the texture due to heat treatment. Residual stress shows anisotropy within the surface of cold-rolled alloy sheets, indicating high compressive residual stress in the rolling direction and in the transverse direction. In general, lower residual stress in the sheets annealed at 600 °C may be related to dislocation rearrangement in the alloys. Furthermore, in the samples annealed at 850 °C, recrystallization and related phenomena are reflected in the deviation from the plot for residual stress, which may also affect the texture.

Fe-Ga alloys are expected as a magnetostrictive material. Currently, Fe-Ga single crystals have been fabricated by the Czochralski method. Thermophysical properties of the Fe-Ga melt are necessary for the improvement of the crystal growth technique, however, these have not measured to date. The aim of this study was therefore to measure the density and surface tension of Fe-Ga melts using electromagnetic levitation technique. It is possible to measure thermophysical property of sample melts at undercooling condition using the electromagnetic levitation method. The density and surface tension of the Fe-Ga decreased with increasing temperature including supercooling temperature region. The molar volume of the Fe-Ga melt is smaller than the molar volume calculated assuming ideal solution. The surface tension of the Fe-Ga melt was in good agreement with the surface tension calculated from Butler model.

In this study, total reflection X-ray fluorescence (TXRF) spectra of dry residues of 10 μL, 100 µL, 200 µL, and 400 μL droplets of a solution containing 10 μg L⁻¹ of Cr on hydrophobic film coated sample holders were measured by a portable TXRF spectrometer, and these spectra were compared. The net intensity of the Cr Kα peak per the concentration of Cr in the sample solution (counts / μg L⁻¹) increased with an increase in the volume of a droplet of the sample solution. This was because the mass of Cr in the dry residue increased with an increase in the volume of a droplet of the sample solution. This enhancement in the net intensity of the Cr Kα peak per the concentration of Cr led to a significant improvement in the detection limit expressed as the concentration of Cr. Detection limits for Cr obtained from the measurements of the dry residues of 10 μL, 100 µL, 200 µL, and 400 μL droplets of the sample solution were 2.1 μg L⁻¹, 0.30 μg L⁻¹, 0.13 μg L⁻¹, and 0.09 μg L⁻¹, respectively. Measuring the dry residue of a large volume droplet of a water sample would be useful for the analysis of trace elements in the sample.

As part of the research on metal aqua and chloro complexes in hydrochloric acid solutions, which is one of the fundamentals in the development of marine resource and the hydrometallurgical process, we have investigated distributions and structures of metal aqua and chloro complexes have been analyzed. The adsorption behavior of manganese species on anion exchange resin was investigated to understand the approximate distribution of manganese aqua and chloro complexes and found that anionic manganese complexes are formed in the concentrated hydrochloric acid solutions. The UV-vis absorption spectra of the manganese species in hydrochloric acid solutions at 298 K were collected for analysis of complex formation behavior. It was determined that the number of complex species to be three using the first derivative test. A series of UV-vis absorption spectra was analyzed using the thermodynamic model fitting analysis. As the results, the distribution of manganese aqua and chloro complexes and their stability constants were determined. The XANES and EXAFS spectra of individual species were obtained dividing a series of the spectra by the distribution of complexes in matrix form. The individual EXAFS spectra were examined using FEFF fitting analysis. The three manganese aqua and chloro complexes are [Mn^II(H₂O)_x]²⁺ (x = 4, 5, or 6), [Mn^IICl₂(H₂O)₄]⁰, and [Mn^IICl₄]²⁻. Only [Mn^IICl₂(H₂O)₄]⁰ was confirmed to have an octahedral structure. The structures of the rest of complexes were not clearly determined.

Pt L3 edge XANES spectra of various kinds of platinum compounds were recorded using a laboratory-type X-ray absorption spectrometer. In order to investigate precision and the accuracy for oxidation state analysis of platinum species with a simple method, the white line intensity was evaluated by least squares fitting using four kinds of profile functions (Gaussian, Lorentzian and two types of pseudo-Voigt functions) and one arctangent function for continuum state. Differences in estimated values and the deviations depending on the type of profile function adopted were discussed. White line intensity could be determined easily and reproducibly using pseudo-Voigt function where a fraction of Lorentzian function is variable. The relationship between oxidation number of Pt compounds and white line area obtained by pseudo-Voigt method are the most preferable. The height of the white line for divalent compounds varies greatly in some cases, and then it is inappropriate to apply the height to estimation of the oxidation number of unknown samples. The changes in platinum species of silica supported Pt(NH₃)₄Cl₂ of a catalyst precursor during air calcination was examined by in-situ XANES. The platinum species exist as divalent species up to 473 K, and changed to zero-valent between 473 and 573 K. The present in-situ laboratory XAFS experiment and the oxidation state analysis is consistent with SR XAFS studies by other research group.

X-ray spectra scattered to 90°were measured for various scatterers of 5-mm thick B₄C, acrylic, titanium, iron, zirconium, and lead plates, and their combinations such as B₄C(5 mm thick) on acrylic plate (1 or 5 mm thick). The degree of polarization was estimated from the observed X-ray spectra at 0°and 90°. Using the best scatterer as an X-ray polarizer for each sample, polarization X-ray fluorescence (XRF) spectra of various samples such as cabtyre cable, book cover made of synthetic-resin, and steel making slag, compared with non-polarization XRF spectra. Toxic elements in some samples were more sensitive for polarized XRF, while other samples were more sensitive for non-polarized XRF. The reasons for such contradicted experimental results were discussed. Most of the measurements were performed by 15 mW X-ray tube power for polarization XRF, and by 3 mW for non-polarized XRF. The meanings of lowest power XRF measurements in the literature were also discussed. This kind of low power experiments may open the possibility of easy way of experiments, and non-invasive XRF analysis for cultural heritage.