Corrosion of Polycrystalline Fe-Si Alloys Studied by TMS, CEMS, and XPS

CORROSION ◽  
10.5006/2676 ◽  
2018 ◽  
Vol 74 (6) ◽  
pp. 623-634 ◽  
Author(s):  
Rafał Idczak ◽  
Karolina Idczak ◽  
Robert Konieczny

The high-temperature corrosion behavior of three polycrystalline Fe-Si alloys containing approximately 4, 5, and 10 at% Si was studied using transmission Mössbauer spectroscopy (TMS), conversion electron Mössbauer spectroscopy (CEMS), and x-ray photoelectron spectroscopy (XPS). The XPS measurements reveal the strong segregation process of silicon atoms to the surface. Moreover, the obtained XPS results suggest that the presence of adsorbed oxygen on the Fe-Si surface effectively enhances the silicon segregation process. On the other hand, the obtained TMS and CEMS spectra show that even 10% of silicon atoms dissolved in the iron matrix do not prevent high-temperature corrosion of the studied Fe-Si alloys. During exposure to air at 870 K, a systematic growth of an α-Fe2O3 compound was observed. Finally, the Mössbauer results show that, during exposure to air, oxygen atoms diffuse to the studied polycrystalline materials not only through the oxide/metal interface on the surface but also along the grain boundaries. Such effects result in the formation of iron oxides in deeper parts of the alloy.

Nanomaterials ◽  
2019 ◽  
Vol 9 (1) ◽  
pp. 100 ◽  
Author(s):  
Anton Zubrik ◽  
Marek Matik ◽  
Michal Lovás ◽  
Zuzana Danková ◽  
Mária Kaňuchová ◽  
...  

The continued decrease in water quality requires new advances in the treatment of wastewater, including the preparation of novel, effective, environmentally friendly, and affordable sorbents of toxic pollutants. We introduce a simple non-conventional mechanochemical synthesis of magnetically responsive materials. Magnetic lignite and magnetic char were prepared by high-energy ball co-milling from either raw Slovak lignite or coal-based char together with a ferrofluid. The products were characterised by X-ray diffraction, electron microscopy, 57Fe Mössbauer spectroscopy, X-ray photoelectron spectroscopy (XPS), volumetric magnetic susceptibility, and low-temperature nitrogen adsorption, and both magnetic carbons were comparatively tested as potential sorbents of As(V) oxyanions and Cd(II) cations in aqueous solutions. The magnetic char was an excellent sorbent of As(V) oxyanions (Qm = 19.9 mg/g at pH 3.9), whereas the magnetic lignite was less effective. The different sorption properties towards arsenic anions may have been due to different oxidation states of iron on the surfaces of the two magnetic composites (determined by XPS), although the overall state of iron monitored by Mössbauer spectroscopy was similar for both samples. Both magnetic composites were effective sorbents for removing Cd(II) cations (Qm (magnetic lignite) = 70.4 mg/g at pH 6.5; Qm (magnetic char) = 58.8 mg/g at pH 6.8).


1990 ◽  
Vol 42 (4) ◽  
pp. 2188-2192 ◽  
Author(s):  
M. G. Smith ◽  
R. D. Taylor ◽  
M. P. Pasternak ◽  
H. Oesterreicher

2003 ◽  
Vol 629 (10) ◽  
pp. 1787-1794 ◽  
Author(s):  
V. Ksenofontov ◽  
S. Reiman ◽  
M. Waldeck ◽  
R. Niewa ◽  
R. Kniep ◽  
...  

1994 ◽  
Vol 91 (1) ◽  
pp. 595-599 ◽  
Author(s):  
ö. Helgason ◽  
H. P. Gunnlaugsson ◽  
K. Jónsson ◽  
S. Steinthórsson

1993 ◽  
Vol 15 (3-4) ◽  
pp. 211-224 ◽  
Author(s):  
E. Kuzmann ◽  
Z. Homonnay ◽  
S. Nagy ◽  
M. Gál ◽  
A. Vértes

57Fe,119Sn, and151Eu Mössbauer spectroscopy was used to study the chemical structure, phonon mode changes, and low-temperature phase transformation around the Tcas well as suppression of superconductivity in high-temperature superconductors and related compounds. Anomalous temperature-dependent changes in the total57Fe spectral area fraction and in the Mössbauer line shift were simultaneously found around the Tcin a EuBa2(Cu0.9957Fe0.01)3O7-dsuperconductor. These anomalous changes were attributed to phonon softening and low-temperature phase transformation occurring around the superconducting transition. Significant differences were observed between the57Fe Mössbauer spectra of superconducting EuBa2(Cu0.9957Fe0.01)3O7-dand the isostructural non-superconducting PrBa2(Cu0.9957Fe0.01)3O7-d. The differences were interpreted in connection with the suppression of superconductivity (by hole filling or hybridization of Pr, Cu and O states) in the Pr-containing compound. The unusually high isomer shift value observed in the Pr-containing material can give evidence for the charge transfer mechanism between the Cu(1) chains and the Cu(2) planes and for its role in the suppression of superconductivity.


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