Oxide formation and conversion on carbon steel in mildly basic solutions

Surface oxide film growth and conversion processes on carbon steel were studied using a range of electrochemical techniques and ex situ surface analyses. The electrochemical study included (i) cyclic voltammetry as a function of various scan conditions and (ii) 7-day potentiostatic oxidation at a range of potentials while periodically performing Electrochemical Impedance Spectroscopy. Carbon steel surfaces at various stages of electrochemical oxidation were examined by SEM, Raman and X-ray photoelectron spectroscopy (XPS). These studies yield a consistent picture of film formation/conversion processes on carbon steel at pH 10.6, which is different to that reported for basic solutions (pH > 13). Oxide film formation/conversion mechanisms for three potential regions are proposed. In region I (≤−0.6 V vs SCE), the main oxide formed is Fe₃O₄ which grows via a solid-state process; in region II (−0.5 V ≤ E (vs SCE) ≤ −0.2 V), continuous growth of the Fe₃O₄ layer is accompanied by its anodic conversion to a more maghemite (γ-Fe₂O₃)-like phase near, or at, the oxide/solution interface by a similar solid-state mechanism to that described for region I; in region III (0.0 V < E (vs SCE) < 0.4 V), the anodic conversion of this Fe₃O₄/γ-Fe₂O₃ oxide to γ-FeOOH leads to a significant structural change, which can lead to film fracture and the introduction of enhanced transport pathways in the film.     

Determinants of exercise intention and behavior during and after phase 2 cardiac rehabilitation: An application of the theory of planned behavior.

Objective: To evaluate the theory of planned behavior (TPB) as a framework for understanding exercise motivation during and after Phase 2 cardiac rehabilitation (CR). Design and Participants: Patients (57 men and 24 women) completed a TPB questionnaire that included attitudes, subjective norms, perceived behavioral control, and exercise intentions pre- and post-Phase 2 CR. Results: During Phase 2 CR, regression analyses indicated that attitude, subjective norm, and perceived behavioral control (PBC) explained 38% of the variance in exercise intention while intention explained 23% of the variance in exercise adherence. At postrehabilitation follow-up, attitudes, subjective norm, and PBC explained 51 % of the variance in exercise intention while intention explained 23% of the variance in exercise adherence. Conclusion: The TPB is a useful framework for understanding exercise intentions and behavior both during and after Phase 2 CR. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of γ-radiation versus H2O2 on carbon steel corrosion

The effect of ionizing radiation on steel corrosion is an important materials issue in nuclear reactors. In the presence of ionizing radiation water decomposes into both oxidizing and reducing species (e.g., OH, H₂O₂, O₂⁻) whose net interactions with steels are not fully understood. The effect of radiation on the corrosion kinetics of carbon steel has been studied at pH 10.6 and room temperature, using electrochemical and chemical speciation analyses. The present study investigates the effect of γ-radiation on carbon steel corrosion and compares it with that of chemically added H₂O₂, which is considered to be the key radiolytically produced oxidant at room temperature. Various oxide films were pre-grown potentiostatically on carbon steel electrodes, and then exposed to either γ-radiation at a dose rate of ∼6.8 kGy h⁻¹ or to H₂O₂ in a concentration range of 10⁻⁶ to 10⁻² M. The corrosion kinetics were studied by monitoring the corrosion potential (E_CORR), and periodically performing linear polarization (LP) and electrochemical impedance spectroscopy (EIS) measurements.     

Double perovskite Cs2AgBiBr6 radiation sensor: synthesis and characterization of single crystals

Journal of Materials Science - Single crystals of lead-free halide double perovskite Cs2AgBiBr6 sensor material manifest a remarkable potential for application in radiation detection and imaging....