Chemical state

About: Chemical state is a research topic. Over the lifetime, 2378 publications have been published within this topic receiving 78183 citations.

Initial Stage Oxidation and Surface Morphology of Modified 9Cr–1Mo Steel at High Temperatures in Air

Abstract: Modified 9Cr–1Mo steel was oxidized in air at 550 and 750 °C for 25, 100, 250 and 500 h and the oxide scales formed were analysed. The surface morphology and the chemical state of the oxide scales were evaluated using scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS), respectively. The different exposure temperatures and time showed significant variations on the surface morphologies, the nature of oxide scale, and oxide constituents. The energy dispersive X-ray spectroscopic (EDS) analysis revealed the segregation of Mn at 750 °C even for short exposure time. Grazing incidence X-ray diffraction (GIXRD) patterns revealed the scales to be enriched with haematite and less intense magnetite peaks. Detailed XPS characterization indicated the presence of mixed oxides of iron (Fe), chromium (Cr) and manganese (Mn) in the oxide scales. The Fe–Cr spinel in the oxide scale offered resistance to oxidation of the steel, whereas Mn–Cr spinel was deleterious in nature as it promoted cracking and formation of blisters.

Adhesive bonding of alumina air-abraded Ag-Pd-Cu-Au alloy with 10-methacryloyloxydecyl dihydrogen phosphate.

Abstract: The aim of this paper is to study changes in the Ag-Pd-Cu-Au alloy surfaces by alumina air-abrasion process and effect of those changes on the adhesive bonding characteristic. Surface roughness, surface composition and chemical state of the alumina air-abraded alloys were analyzed by a confocal laser scanning microscope, an energy dispersive X-ray spectroscopy and an X-ray photoelectron spectroscopy. The results showed that the alumina air-abrasion changed the alloy surface by mechanical roughening, alumina remain and copper oxidation. Effect of the changes in the alloy surface on the adhesive bonding characteristic was examined by using a methyl methacrylate/tri-n-butylborane derivative (MMA/TBB) resin cement with the 10-methacryloyloxydecyl dihydrogen phosphate (MDP) contained primer. The shear bond strength test results indicated that the surface oxidation by the abrasion is the main contributor that improved the adhesive bonding rather than other effects such as mechanical roughening or alumina remain.

Corrosion resistance of Fe2O3-Cr2O3 artificial passive films formed with LP-MOCVD

Abstract: Fe2O3-Cr2O3 artificial passive films were formed with a low pressure MOCVD technique using iron (III) acetylacetonate and chromium (III) acetylacetonate. The relationships between the crystal structure, the chemical state of the constituent elements, and the corrosion resistance of the films were examined in acid solutions. The films deposited above 300°C hardly dissolved in 1.0 M HCl and those deposited below 250°C, however, easily dissolved in the same solution. The dissolution rate of the films in solution increased with decreasing substrate temperature. When polarized cathodically in 1.0 M H2SO4, the films deposited below 250°C dissolved due to the reduction of the Fe2O3 component in the films. The reduction of the Fe2O3 component was, however, suppressed on the films deposited above 300°C. Therefore, with increasing crystallinity and the amount of M-O type chemical bonds, the corrosion resistance of the films increases in HCl and H2SO4 solutions.