Formation of Oxide Phases in the System Fe203-Sm203

Formation of oxide phases in the system Fe2O3-Sm2O3 was investigated. The samples wore prepared by the solid state reactions et two molar ratios of Fe203 and Sm203

FT-IR and Mossbauer Study of Corrosion of Steel in Tap and Mineral Water

The influence of carbonates on the process of corrosion of steel in aqueous media has been studied. The corrosion of steel in tap water and mineral water of three different chemical compositions (all for human use) was monitored for up to 6 months. Rust samples were analyzed using Fourier transform infrared (FT-IR) spectroscopy and 57 Fe Mossbauer spectroscopy. Some selected samples were also analyzed by X-ray powder diffraction (XRD).It was shown that the concentration of carbonates plays an important role in the corrosion of steel in aqueous media, both during short (days), and long times (months) of corrosion. For short times of corrosion in the presence of a high content of carbonates, the rust was found amorphous for XRD. It was proved that "\u27(-FeOOHwas absent in amorphous rust. The possible presence of ferrihydrite in this amorphous fraction is discussed taking into account the FT-IR and Mossbauer spectroscopic results. At a very high concentration of carbonates, after 6 month of corrosion,\u27(-FeOOHwas not found in the rust. Formation of a-FeOOH and Fe304 in corrosion products was also monitored. It was suggested that, in the very early stages of corrosion, carbonates can be structurally incorporated in the rust in the form of hydroxycarbonates, while in the later stages, they can modify the phase transformation by the mechanism of specific adsorption

Formation of Rust During the Corrosion of Steel in Water and (NH4)2S04 Solutions. Part II

Chemical and structural properties of the rust formed by corrosion of steel in water and (NH4)2S04 solutions at 20 °C for time periods up to 6 months were investigated by X-ray dittraction, Fourier transform IR spectroscopy and 67Fe Mossbauer spectroscopy

Stvaranje hrđe tijekom korozije čelika u vodi i otopinama (NH4)2S04. II.

Chemical and structural properties of the rust formed by corrosion of steel in water and (NH4)2S04 solutions at 20 °C for time periods up to 6 months were investigated by X-ray dittraction, Fourier transform IR spectroscopy and 67Fe Mossbauer spectroscopy.Kemijska i strukturna svojstva hrđe, stvorene korozijom čelika u vodi i otopinama (NH4)2S04 pri 20 °C u vremenskom periodu do 6 mjeseci, istraživana su difrakcijom X-zraka, FT-IR spektroskopijom i 57Fe Mossbauerovom spektroskopijom. U uzorcima hrđe detektirane su tri oksidne faze: lepidokrokit, magnetit i getit. Raspodjela tih faza u uzorcima hrde ovisila je o vremenu korozije i o koncentraciji (NH4)2SO4. 57Fe Mossbauerova spektroskopija pokazala je nestehiometrijski karakter magnetita (Fe3-x04). Magnetit nije opažen u hrđi koja je stvorena u otopini 2M (NH4)2S04. FT-IR spektroskopija pokazala se posebno pogodnom za određivanje malih količina getita i lepidokrokita u hrđi. Snažan utjecaj koncentracije (NH4)2S04 na fazni sastav hrđe objašnjen je kumulativnim efektom iona NH4+ i SO2- agresivnih u korozijskom smislu

Stvaranje hrđe tijekom korozije čelika u vodi i otopinama (NH4)2S04. II.

Chemical and structural properties of the rust formed by corrosion of steel in water and (NH4)2S04 solutions at 20 °C for time periods up to 6 months were investigated by X-ray dittraction, Fourier transform IR spectroscopy and 67Fe Mossbauer spectroscopy.Kemijska i strukturna svojstva hrđe, stvorene korozijom čelika u vodi i otopinama (NH4)2S04 pri 20 °C u vremenskom periodu do 6 mjeseci, istraživana su difrakcijom X-zraka, FT-IR spektroskopijom i 57Fe Mossbauerovom spektroskopijom. U uzorcima hrđe detektirane su tri oksidne faze: lepidokrokit, magnetit i getit. Raspodjela tih faza u uzorcima hrde ovisila je o vremenu korozije i o koncentraciji (NH4)2SO4. 57Fe Mossbauerova spektroskopija pokazala je nestehiometrijski karakter magnetita (Fe3-x04). Magnetit nije opažen u hrđi koja je stvorena u otopini 2M (NH4)2S04. FT-IR spektroskopija pokazala se posebno pogodnom za određivanje malih količina getita i lepidokrokita u hrđi. Snažan utjecaj koncentracije (NH4)2S04 na fazni sastav hrđe objašnjen je kumulativnim efektom iona NH4+ i SO2- agresivnih u korozijskom smislu

Formation of Oxide Phases in the System Fe203-Sm203

Formation of oxide phases in the system Fe2O3-Sm2O3 was investigated. The samples wore prepared by the solid state reactions et two molar ratios of Fe203 and Sm203

Formation of Rust During the Corrosion of Steel in Water and (NH4)2S04 Solutions. Part II

Chemical and structural properties of the rust formed by corrosion of steel in water and (NH4)2S04 solutions at 20 °C for time periods up to 6 months were investigated by X-ray dittraction, Fourier transform IR spectroscopy and 67Fe Mossbauer spectroscopy

Formation and Characterization of NiFe2O4

Synthesis of nickel ferrite, NiFe204, was performed applying the thermal treatment of the corresponding mixed metal hydroxides or the solid state reaction between NiO and a-Fe203. The samples were studied by X-ray diffraction, Fourier transform IR spectroscopy and 57Fe Mčssbauer spectroscopy. Ball-milling of NiFe204 caused a decrease of hyperfine magnetic fields corresponding to Fe3+ ions in tetrahedral and octahedral sites, an increase of the Mossbauer spectral line widths, as well as a slight increase of isomer shifts. It was supposed that the ball-milling of NiFe204 had more influence on the degree of inversion than on other structural properties of the spinel. It was found that the heating temperature, and not the heating time, had the ultimate effect on NiFe204 microstructure. Samples heated up to 500 °C showed a pronounced size-correlated diffraction line broadening, corresponding to the coherent domain size of about 13 nm, and rather small crystalline disorder. Samples heated at temperature s above "" 1000 °C had much larger crystallites, exhibiting very small disorder

Formation and Characterization of NiFe2O4

Synthesis of nickel ferrite, NiFe204, was performed applying the thermal treatment of the corresponding mixed metal hydroxides or the solid state reaction between NiO and a-Fe203. The samples were studied by X-ray diffraction, Fourier transform IR spectroscopy and 57Fe Mčssbauer spectroscopy. Ball-milling of NiFe204 caused a decrease of hyperfine magnetic fields corresponding to Fe3+ ions in tetrahedral and octahedral sites, an increase of the Mossbauer spectral line widths, as well as a slight increase of isomer shifts. It was supposed that the ball-milling of NiFe204 had more influence on the degree of inversion than on other structural properties of the spinel. It was found that the heating temperature, and not the heating time, had the ultimate effect on NiFe204 microstructure. Samples heated up to 500 °C showed a pronounced size-correlated diffraction line broadening, corresponding to the coherent domain size of about 13 nm, and rather small crystalline disorder. Samples heated at temperature s above "" 1000 °C had much larger crystallites, exhibiting very small disorder