The ability to map plastic deformation around high strain gradient microstructural features is central in studying phenomena such as fatigue and stress corrosion cracking. A method for the visualization of plastic deformation in electron back-scattered diffraction (EBSD) data has been developed and is described in this article. This technique is based on mapping the intragrain misorientation in polycrystalline metals. The algorithm maps the scalar misorientation between a local minimum misorientation reference pixel and every other pixel within an individual grain. A map around the corner of a Vickers indentation in 304 stainless steel was used as a test case. Several algorithms for EBSD mapping were then applied to the deformation distributions around air fatigue and stress corrosion cracks in 304 stainless steel. Using this technique, clear visualization of a deformation zone around high strain gradient microstructural features (crack tips, indentations, etc.) is possible with standard EBSD data.

Misorientation mapping for visualization of plastic deformation via electron back-scattered diffraction.

The time-dependent hydrogen evolution reaction (HER) on Ni electrodes shows a large increase in electrode over-potential with time. This is ascribed to hydride formation at active Ni cathode surfaces. Hydride formation was detected by x-ray diffraction, morphological changes at the electrode surfaces, and resulting changes in secondary electron emissivities. Nickel electrodes annealed for 2 h in an argon atmosphere at 1000 o C after HER did not show x-ray lines assigned to hydride

http://repositorio.unicamp.br/jspui/bitstream/REPOSIP/99546/1/2-s2.0-0026654334.pdf

Hydride Effect On The Kinetics Of The Hydrogen Evolution Reaction On Nickel Cathodes In Alkaline Media

Effects of solution temperature on the kinetic nature of passive film on Ni were investigated using polarization test, Mott–Schottky analysis and electrochemical impedance spectroscopy to reveal why the corrosion resistance of Ni is degraded with an increase in solution temperature. The increase in the corrosion rate of Ni with solution temperature was confirmed by the increase in the passive current density and also in the steady-state current density. Mott–Schottky analysis revealed that the passive film formed on Ni exhibits a p-type semiconducting characteristics irrespective of the solution temperature, and the concentration of cation vacancy in the passive film increases with temperature. By optimizing the reduced PDM (point defect model) on the experimental impedance data, base rate constants and transfer coefficients for the charge transfer reactions occurring at the metal/film and film/solution interfaces were extracted, and the Warburg coefficient for the cation vacancy transport was also determined. According to the calculated kinetic parameters (rate constants for the interfacial reactions, diffusivity of cation vacancy, etc.), the mechanism for the degradation of corrosion resistance of Ni with solution temperature was explained.

http://ma.ecsdl.org/content/MA2012-02/22/2179.full.pdf

Effects of Solution Temperature on the Kinetic Nature of Passive Film on Ni

We report various synchrotron radiation laboratory based techniques used to characterize cement based materials in nanometer scale. High resolution X-ray transmission imaging combined with a rotational axis allows for rendering of samples in three dimensions revealing volumetric details. Scanning transmission X-ray microscope combines high spatial resolution imaging with high spectral resolution of the incident beam to reveal X-ray absorption near edge structure variations in the material nanostructure. Microdiffraction scans the surface of a sample to map its high order reflection or crystallographic variations with a micron-sized incident beam. High pressure X-ray diffraction measures compressibility of pure phase materials. Unique results of studies using the above tools are discussed—a study of pores, connectivity, and morphology of a 2,000 year old concrete using nanotomography; detection of localized and varying silicate chain depolymerization in Al-substituted tobermorite, and quantification of monosulfate distribution in tricalcium aluminate hydration using scanning transmission X-ray microscopy; detection and mapping of hydration products in high volume fly ash paste using microdiffraction; and determination of mechanical properties of various AFm phases using high pressure X-ray diffraction.

/pdf/advanced-nanoscale-characterization-of-cement-based-x66sakao0c.pdf

Advanced Nanoscale Characterization of Cement Based Materials Using X-Ray Synchrotron Radiation: A Review

Review—Factors Influencing Sulfur Induced Corrosion on the Secondary Side in Pressurized Water Reactors (PWRs)

The role of local strains from prior cold work on stress corrosion cracking of α-brass in Mattsson's solution

Plastic and elastic strains in short and long cracks in Alloy 600 studied by polychromatic X-ray microdiffraction and electron backscatter diffraction

The Role of Local Strains from Prior Cold Work on Stress Corrosion

Laue diffraction measurements made using polychromatic synchrotron x-radiation have revealed significant changes to the microscopic strain distributions in an Alloy 600 (UNS N06600) tube following ...

Jaganathan Ulaganathan

Papers

The role of local strains from prior cold work on stress corrosion cracking of α-brass in Mattsson's solution

Plastic and elastic strains in short and long cracks in Alloy 600 studied by polychromatic X-ray microdiffraction and electron backscatter diffraction

The Role of Local Strains from Prior Cold Work on Stress Corrosion

Mapping of Microscopic Strain Distributions in an Alloy 600 C-Ring After Application of Hoop Stresses and Stress Corrosion Cracking

Communication—Dissolution Measurement of Ni (111) in an Acidic Solution Using X-ray Reflectometry