Chrysotile asbestos from different geographic regions was characterized by
57Fe Mössbauer and FT-IR spectroscopies, and FE-SEM coupled with EDS. Mössbauer spectra showed incorporation of Fe(II) and ...Fe(III) into the crystal structure of chrysotile. The Fe(II)/Fe(III) ratios were calculated. The Fe(II) occupied the octahedral Mg(II) positions. Broadening of Mössbauer lines corresponding to the Fe(III) doublet indicated a possible presence of Fe(III) in tetrahedral and octahedral positions. In all samples magnetite (Fe
3−
x
O
4) was found as associated mineral. Changes in the FT-IR spectra of chrysotiles were assigned to structural incorporation of metal ions, such as iron or aluminium ions. The morphology of chrysotile asbestos was inspected by FE-SEM.
Materials producing strain in a magnetic field are known as magnetoelastic or magnetostrictive materials. A new type of material that is able to produce giant strain in a nonhomogeneous magnetic ...field has been developed. In these magnetic-field-sensitive gels (ferrogels) fine colloidal particles having superparamagnetic behavior are incorporated into a highly swollen elastic polymer network. Magnetic properties of ferrogels have been investigated using electron microscopy, static magnetization measurements, and Mössbauer spectroscopy. Analysis of the data yielded information on the superparamagnetic behavior of ferrogels and made it possible to estimate the size distribution of the magnetic cores of magnetite particles made by chemical precipitation and built into a chemically cross-linked polyvinyl alcohol matrix. The results are interpreted on the basis of a core–shell model.
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 "'(-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,'(-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.
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.
Chemical and structural properties of the rust formed by corrosion of steel in water and (NH4)2SO4 solutions at 20 °C for time periods up to 6 months were investigated by X-ray diffraction, Fourier ...transform IR spectroscopy and 57Fe Mössbauer spectroscopy. Three oxide phases, y-FeOOH (lepidocrocite), Fe304 (magnetite) and a-FeOOH (goethite) were detected in the rust samples. The distribution of these phases in the rust was dependent on the time of corrosion and the concentration of (NH4)2SO4. 57Fe Mössbauer spectroscopy indicated the substoichiometric character of magnetite (Fe3_I04). Magnetite was not observed in the rust generated in 2M (NH4)2SO4 solution. Fourier transfrom IR spectroscopy was particularly useful in the detection of very small amounts of goethite and lepidocrocite in the rust. The strong influence of (NH4)2SO4 electrolyte on the corrosion of steel in aqueous medium was explained as a cumulative effect of two aggresive ions, NH4+ and SO42-.
Oxide phases generated during the synthesis of NiFe2O4 from aqueous Ni(N03)2/Fe(N03)3 solution were characterized by X-ray diffraction, Fourier transform IR spectroscopy and 57Fe Mössbauer ...spectroscopy. Nitrate salts and a-Fe203 were observed in the samples prepared at temperatures up to 300 °C. The formation of nickel ferrite was observed at temperatures of 500 °C and higher. Stoichiometric NiFe2O4 was obtained at 1350 °C. NiO and cx-Fe203 were intermediate phases in the process of nickel ferrite formation. A decreased hyperfine magnetic field was observed for a-Fe2Oa prepared at lower temperatures. Decomposition of nitrate groups was followed by Fourier transform IR spectroscopy.
Formation of oxide phases in the system Fe203-Sm203 was investigated. The samples were prepared by the solid state reactions at two molar ratios of Fe203 and Sm203. The following oxide phases were ...detected by X-ray diffraction: C-Sm203, B-Sm203, a-Fe203, SmFe03 and Sm3Fe5012. For the molar ratio Fe203 : Sm203 = 1:1, SmFe03 was detected as one of the oxide phases at temperatures up to 800 °C and as a single phase at 1000 °C and higher temperatures. For the molar ratio Fe203 : SnigCtj = 5:3, SmFe03 was the intermediate phase up to 1200 °C, and Sm3Fe50i2 was found as a single phase at 1300 °C. The oxide phases containing iron ions were characterized by 57Fe Mössbauer spectroscopy. The formation of SmFe03 and Sm3Fe5012 phases, as end products of the solid state reactions in the system Fe203-Sm203, was also investigated by IR spectroscopy.
