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1
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Positron Annihilation in Magnetite Nanopowders Prepared by Co-Precipitation Method

100%
Durak K., Wiertel M., Surowiec Z., Miaskowski A.
Acta Physica Polonica A
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2017
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vol. 132
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issue 5
1593-1597
EN
Nanosized iron oxide powders are materials considered with regard to its application in medical therapy called hyperthermia. Magnetite nanopowders with crystallite size varying from 6.6 to 11.8 nm have been prepared by the co-precipitation method. In this study a change of a crystallite size is driven mainly by varying of initial pH of water ammonia solution in which a process of magnetite precipitation runs. Crystallographic structures and phase composition obtained samples and the size of magnetite nanoparticles were determined by X-ray diffraction method. Positron lifetime spectroscopy has been used to assess defectiveness of microstructure. Experimental positron annihilation spectra were successfully resolved into three lifetime components. It appears that from point of view of microstructure the defects concentrations in studied nanopowder samples are very high which causes a saturation of positron trapping.
2
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Mössbauer and X-ray Diffraction Studies of Zr_{1-x}Ti_xFe_2 Laves Phase Compounds

100%
Budzyński M., Sarzyński J., Surowiec Z., Wiertel M.
Acta Physica Polonica A
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2001
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vol. 100
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issue 5
717-722
EN
Mössbauer spectroscopy of ^{57}Fe and X-ray diffraction measurements in the Zr_{1-x}Ti_xFe_2 phase have been made. Our X-ray diffraction spectra revealed that the samples have the cubic C15 crystal structure for low Ti concentration and the hexagonal C14 structure for high Ti concentration. In the range of 0.2≤xࣘ0.5 a mixture of both structures occurs. The investigated compounds are paramagnetic at RT for x>0.80 and magnetic for x
3
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B8-Type Solid Solutions of Manganese Antimonide and Cu, Zn, Al, or~Si

100%
Budzyński M., Mitsiuk V., Surowiec Z., Tkachenka T.
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vol. 125
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issue 3
840-842
EN
The solid solutions with B8-type of crystal structure were prepared in ternary systems MnSb(Zn), MnSb(Cu), MnSb(Al), and MnSb(Si). The ranges of B8 solid solutions existence are limited. The structural and magnetic characteristics were investigated by X-ray powder diffraction, magnetization measurements and the Mössbauer spectroscopy.
4
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The Influence of Reduction Process on the Iron-Molybdenum Nanoparticles in Modified MCM-41 Silica

100%
Surowiec Z., Wiertel M., Gac W., Budzyński M.
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vol. 125
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issue 3
846-849
EN
Iron-molybdenum silica mesoporous materials were obtained by the application of direct hydrothermal method. The influence of high temperature samples reduction in the H_2 flow on their structural and magnetic properties was studied. Four samples with different metal contents relative to silica were investigated. The study was carried out by means of X-ray diffraction, ^{57}Fe Mössbauer spectroscopy and the temperature programmed reduction method. With an increasing metals content, primary pores of MCM-41 transformed into the bottle-like pores, and then into the slit-like ones. Reduction and heat treatment caused the α-Fe, Fe_2Mo, and Fe-Mo alloy formation. Iron and molybdenum atoms after being released into the silica matrix, where they were embedded, create clusters or crystallites. It was observed that the high temperature reduction caused partial transformation of highly dispersed Fe-Mo oxides species initially embedded in silica walls into crystallites big enough to give magnetic sextet component in the Mössbauer spectra.
5
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^{57}Fe Hyperfine Interactions in the Sc(Fe_{1-x}Ni_x)_2 Laves Phases Synthesized under High Pressure

100%
Wiertel M., Surowiec Z., Budzyński M., Tsvyashchenko A.
Acta Physica Polonica A
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2008
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vol. 114
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issue 6
1517-1527
EN
The structural and microscopic magnetic properties of the pseudobinary Sc(Fe_{1-x}Ni_x)_2 system prepared under high pressure of 8 GPa were studied by X-ray diffraction and Mössbauer measurements in the range of 0.0 ≤ x ≤ 0.60. The samples for 0.0 ≤ x ≤ 0.10 have the hexagonal C14-type structure and those for 0.30 ≤ x ≤ 0.60 crystallize in the C15-type structure. Both the magnetic hyperfine field on ^{57}Fe and the Curie temperature decrease with the increasing Ni content and the system becomes paramagnetic for x ≈ 0.60 at room temperature. The form and temperature dependences of the Mössbauer spectra for 0.40 ≤ x ≤ 0.50 indicate the coexistence of paramagnetic and ferromagnetic regions in the samples and occurrence of magnetic clusters with a wide distribution of the Curie temperatures. It is interesting that T_C for the compounds obtained under high pressure are by about 100 K smaller in comparison with those for the isostructural samples produced under normal pressure even though interatomic distances are practically equal in the both types of compounds.
6
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The Synthesis and Properties of High Surface Area Fe_{2}O_{3} Materials

100%
Surowiec Z., Gac W., Wiertel M.
Acta Physica Polonica A
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2011
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vol. 119
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issue 1
18-20
EN
Two types of the silica materials were used for the preparation of iron oxides. The MCM-48 type silica support and wide-pore silica gel were impregnated with iron nitrates. The samples were investigated by the nitrogen adsorption/desorption method, X-ray diffraction, scanning electron microscopy, and ^{57}Fe Mössbauer spectroscopy. Redox properties were studied by the temperature programmed reduction method. Strongly dispersed hematite was evidenced on the supports. An application of the MCM-48 silica mesoporous materials led to the development of the oxide phases within the ordered porous structure. The detailed temperature programmed reduction studies evidenced slight differences of the redox properties of the species located within the silica templates and after their removal. Magnetic properties of iron oxides were related to the porous structure of the silica supports. The Mössbauer study of high surface area materials Fe/SiO_{2} and Fe/MCM-48 type silicate templates revealed existence of ferro- and superparamagnetic phases. The relative contribution of the superparamagnetic doublet component in Mössbauer spectra is 15% and 80% for Fe/SiO_{2}/c and Fe/MCM-48/c samples, respectively.
7
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Positron Annihilation in MnFe_2O_4/MCM-41 Nanocomposite

100%
Wiertel M., Surowiec Z., Gac W., Budzyński M.
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vol. 125
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issue 3
793-797
EN
In the paper results of studies of MnFe_2O_4/MCM-41 nanocomposites have been presented. The influence of manganese ferrite loading on changes of porous properties of mesoporous MCM-41 structure was studied by means of N_2 sorption/desorption method and positron annihilation lifetime spectroscopy. Disappearance of the longest-lived ortho-positronium component (τ_5) of pure MCM-41 mesoporous material in the positron annihilation lifetime spectra of MnFe_2O_4/MCM-41 measured in vacuum is a result of either o-Ps quenching or the Ps inhibition mechanism. Filling of pores in the studied nanocomposites by air at ambient pressure causes partial reappearance of the (τ_5) component except for the sample with maximum ferrite content. Both the (τ_5) component lifetime and intensity are suppressed together with increasing MnFe_2O_4 content by chemical quenching and inhibition of Ps formation occur. Observed anti-quenching effect of air is a result of two processes: neutralization of some surface active centres acting as inhibitors and considerably weaker paramagnetic quenching by O_2 molecules.
8
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Positron Annihilation Studies of Mesoporous Iron-Molybdenum Modified MCM-41 Silica

100%
Surowiec Z., Wiertel M., Gac W., Budzyński M.
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vol. 125
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issue 3
789-792
EN
Iron-molybdenum modified MCM-41 mesoporous materials were obtained by the application of direct hydrothermal method. An incorporation of iron and molybdenum ions in the synthesis stage led to structural changes of the MCM-41 support. With an increasing metals content, cylindrical pores of silica are destroyed. X-ray diffraction investigations indicated that both iron and molybdenum ions were first embedded in the silica walls and then formed highly dispersed species in the pores. The porous structure of the studied samples was examined by means of N_2 adsorption/desorption and PALS methods. The longest-lived o-Ps lifetime component remains constant but its intensity monotonically decreases, except for the sample with the highest metals content. These results indicate that an effect of o-Ps formation inhibition occurs.
9
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Magnetic Nanoparticles in MCM-41 Type Mesoporous Silica

88%
Surowiec Z., Bierska-Piech B., Wiertel M., Budzyński M., Goworek J.
Acta Physica Polonica A
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2008
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vol. 114
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issue 6
1605-1613
EN
Structural phase transformations and magnetic properties of mesoporous MCM-41 template modified with iron and nickel salts were studied by nitrogen physisorption, X-ray diffraction, Mössbauer spectroscopy and transmission electron microscopy. The FeNi-oxide or the bimetallic crystal structure is formed for low and high Ni concentrations, respectively. The average size of nanoparticles is about 10 nm. About 70% of particles exist in a superparamagnetic state at room temperature.
10
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Mössbauer Study of Cubic Phase in the Mn-Sb System

88%
Budzyński M., Goncharov V., Mitsiuk V., Surowiec Z., Tkachenka T.
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vol. 125
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issue 3
850-852
EN
Mössbauer spectroscopy was applied to investigate the structural and magnetic parameters of cubic phase in the Mn-Sb system. The validity of the model of triangular magnetic structure in Mn_3Sb has been confirmed.
11
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Effect of N₂⁺ Ion Implantation and Thermal Annealing on Near-Surface Layers of Implanted GaAs

88%
Kulik M., Surowiec Z., Rzodkiewicz W., Filiks J., Drozdziel A.
Acta Physica Polonica A
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2015
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vol. 128
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issue 5
918-922
EN
The surface of semi-isolating GaAs (100) was irradiated with a fluence of 6×10¹⁷ cm¯² of the N₂⁺ ion beam; then, the samples were thermally annealed at temperatures of 500, 700, and 900°C for 2 h in an argon gas flow. The surface roughness of implanted samples was investigated with the help of atomic force microscopy. Numerous hillocks, which caused a significant increase in surface roughness, were observed. The spectroscopic ellipsometry method was used for determination of pseudo-dielectric functions of the near-surface layers in the investigated samples and the thickness of native oxides covering the irradiated surface. It was observed that the shapes of disorder spectra of the dielectric functions of near-surface layers of implanted GaAs partly returned to their original state after the thermal annealing.
12
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Structure and Hyperfine Interactions in Aurivillius Bi_{9}Ti_{3}Fe_{5}O_{27} Conventionally Sintered Compound

88%
Mazurek M., Lisińska-Czekaj A., Surowiec Z., Jartych E., Czekaj D.
Acta Physica Polonica A
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2011
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vol. 119
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issue 1
72-74
EN
The structure and hyperfine interactions in the Bi_{9}Ti_{3}Fe_{5}O_{27} Aurivillius compound were studied using X-ray diffraction and Mössbauer spectroscopy. Samples were prepared by the conventional solid-state sintering method at various temperatures. An X-ray diffraction analysis proved that the sintered compounds formed single phases at temperature above 993 K. Mössbauer measurements have been carried out at room and liquid nitrogen temperatures. Room-temperature Mössbauer spectrum of the Bi_{9}Ti_{3}Fe_{5}O_{27} compound confirmed its paramagnetic properties. However, low temperature measurements revealed the additional paramagnetic phase besides the antiferromagnetic one.
13
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Structure and Magnetic Properties of Bi5Ti3FeO15 Ceramics Prepared by Sintering, Mechanical Activation and Edamm Process. A Comparative Study

64%
Jartych E., Pikula T., Mazurek M., Franus W., Lisińska-Czekaj A., Czekaj D., Oleszak D., Surowiec Z., Aksenczuk A., Calka A.
Archives of Metallurgy and Materials
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2016
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issue 2
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