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Zeitschriftendaten
Format
Zeitschrift
eISSN
1508-5791
Erstveröffentlichung
25 Mar 2014
Erscheinungsweise
4 Hefte pro Jahr
Sprachen
Englisch

Suche

Volumen 62 (2017): Heft 2 (June 2017)

Zeitschriftendaten
Format
Zeitschrift
eISSN
1508-5791
Erstveröffentlichung
25 Mar 2014
Erscheinungsweise
4 Hefte pro Jahr
Sprachen
Englisch

Suche

21 Artikel
Uneingeschränkter Zugang

Synthesis and characterization of iron oxide magnetic nanoparticles

Online veröffentlicht: 09 Jun 2017
Seitenbereich: 73 - 77

Zusammenfassung

Abstract

Small particles of magnetite, i.e. 7.5, 13.4 and 14.1 nm in diameter, were obtained by the method of co-precipitation. The crystal structure and size distributions were determined by means of transmission electron microscopy and X-ray diffraction. The magnetic properties of the nanoparticles were tested by Mössbauer spectroscopy within the temperature range from 3 K to room temperature (RT). The Mössbauer study of magnetic nanoparticles reveals relaxation behaviour related to the existence of the superparamagnetic phase. The blocking temperature depends on the sizes of the nanoparticles and the ammonia concentration.

Schlüsselwörter

  • Mössbauer effect
  • superparamagnetic nanoparticles
Uneingeschränkter Zugang

Mössbauer and magnetic studies of FeCoNiCuNbSiB nanocrystalline alloys

Online veröffentlicht: 09 Jun 2017
Seitenbereich: 79 - 84

Zusammenfassung

Abstract

Nanocrystalline Fe80-x-yCoxNiyCu1Nb3Si4B12 alloys were prepared by the annealing of amorphous ribbons. Primary crystallization of the alloys annealed at temperatures of between 500 and 550°C was studied by X-ray diffraction and Mössbauer spectroscopy. Magnetic properties of the alloys were investigated using a hysteresis loop tracer and vibrating sample magnetometer. The annealed ribbons are composed of a two-phase nanostructure consisting of bcc Fe-based grains embedded in an amorphous matrix. Conversion electron Mössbauer spectroscopy (CEMS) measurements reveal a more advanced crystallization process in the surface layers when compared with the volume of the ribbons. The degree of saturation magnetization of the nanocrystalline alloys is of about 1.5 T. The coercive field varies from 1.0 to 6.5 A/m and peaks at an annealing temperature of 525°C. Magnetic softening of the nanocrystalline alloys observed after annealing at 550°C is correlated with a volume fraction of the nanocrystalline bcc phase.

Schlüsselwörter

  • amorphous ribbons
  • nanocrystalline alloys
  • Mössbauer spectroscopy
  • soft magnetic properties
Uneingeschränkter Zugang

Microstructure and magnetic properties of amorphous Fe51Co12Si16B8Mo5P8 alloy

Online veröffentlicht: 09 Jun 2017
Seitenbereich: 85 - 89

Zusammenfassung

Abstract

Microstructure and thermomagnetic characteristics of the amorphous Fe51Co12Si16B8Mo5P8 alloy in the as-quenched state and after 1 h of annealing at 573 K and 773 K are studied. The structural investigations performed by Mössbauer spectroscopy and X-ray diffractometry confirmed the amorphous structure of the analysed materials. An increase in the annealing temperature up to 773 K does not lead to crystallization of the amorphous alloy. Only structural rearrangement that causes changes in the topological short-range order and annealing out of free volume is observed. This behaviour was confirmed by modifications of the shapes of hyperfine field distributions derived from the corresponding Mössbauer spectra of the investigated alloys. The Curie temperatures of the as-quenched and annealed Fe51Co12Si16B8Mo5P8 alloy at 573 and 773 K are 400, 405 and 421 K, respectively.

Schlüsselwörter

  • microstructure
  • Mössbauer spectroscopy
  • magnetic properties
  • Curie point
Uneingeschränkter Zugang

Features of the structural and magnetic properties of Pb(TixZr1–xO3)-NiFe1.98Co0.02O4 in the polarized state

Online veröffentlicht: 09 Jun 2017
Seitenbereich: 91 - 94

Zusammenfassung

Abstract

Composites with a 90%Pb(TixZr1-xO3)-10%NiFe1.98Co0.02O4 composition have been synthesized. It has been established that the polarization of samples resulting from exposure to an electric field for 1 hour of 4 kV/mm in strength at a temperature of 400 K leads to crystal structure deformation. The compression of elementary crystal cells in some areas during polarization of the sample creates conditions suitable for the enhancement of magnetic exchange interactions. It has been found that the polarization process of such compositions leads to increases in specific magnetization and magnetic susceptibility. The analysis of Mössbauer spectra has shown that the polarization of the 90%Pb(TixZr1-xO3)-10%NiFe1.98Co0.02O4 composite leads to significant changes in the effective magnetic fields of iron subspectra in various positions.

Schlüsselwörter

  • Mössbauer effect
  • X-ray diffraction
  • lead zirconate titanate (PZT)
  • unpolarized and polarized states
  • specific magnetization
  • magnetic susceptibility
  • effective magnetic fields
Uneingeschränkter Zugang

Structural properties of Mn-substituted hercynite

Online veröffentlicht: 09 Jun 2017
Seitenbereich: 95 - 100

Zusammenfassung

Abstract

In this work spinel series with the general formula Fe1-xMnxAl2O4 (where x = 0, 0.3, 0.5 and 0.7) were synthesized and characterized with respect to their structure and microstructure. X-ray diffractometry (XRD) was used to identify the phase composition that revealed a single phase spinel material. Rietveld refinements of the XRD patterns were carried out in order to determine the lattice and oxygen positional parameters of the spinel compounds. Mössbauer effect measurements were performed at room temperature to determine the local chemical environment of the Fe ions, their valences, and degrees of spinels inversion. It was shown that an increase in the Mn content led to a decrease in the ratio of Fe2+ to Fe3+. The results obtained from Mössbauer spectroscopy (MS) were used to establish the chemical formulas of the synthesized spinels. Finally, the microstructure that was observed using scanning electron microscopy (SEM) showed a compact microstructure with an octahedral crystal habit.

Schlüsselwörter

  • FeAl2O4
  • MnAl2O4
  • hercynite
  • spinel
  • galaxite
  • Mössbauer spectroscopy
Uneingeschränkter Zugang

57Fe Mössbauer spectroscopy investigations of iron phase composition in fluidized beds from the ELCHO power plant in Chorzów, Poland

Online veröffentlicht: 09 Jun 2017
Seitenbereich: 101 - 107

Zusammenfassung

Abstract

The study investigates the physical and chemical properties of fly ash and bottom ash from a power plant ELCHO in Chorzów, Poland. Coal combustion products generated in the process of combustion in circulating fluidized beds (CFBs) are considerably different from fly and bottom ashes obtained from dust furnaces and multi-layer ones. The composition of the iron-bearing phase in the waste of circulating fluidized bed combustion was determined using Mössbauer spectroscopy and X-ray powder diffraction (XRD) methods.

Schlüsselwörter

  • Mössbauer spectroscopy
  • fly ash
  • bottom ash
Uneingeschränkter Zugang

Thermodynamic properties of dilute Co-Fe solid solutions studied by 57Fe Mössbauer spectroscopy

Online veröffentlicht: 09 Jun 2017
Seitenbereich: 109 - 115

Zusammenfassung

Abstract

The Co1-xFex alloys where x ranges from 0.01 to 0.06 were measured at room temperature using transmission Mössbauer spectroscopy (TMS). The analysis of the obtained data allowed the determination of the short-range order (SRO), the binding energy Eb between two iron atoms in the studied materials using the extended Hrynkiewicz-Królas idea and the enthalpy of solution HCo-Fe of Fe in Co. The results showed that the Fe atoms dissolved in a Co matrix interact repulsively and the estimated value of HCo-Fe = -0.166(33) eV/atom. Finally, values of the enthalpy of solution were used to predict the enthalpy of mixing for the Co-Fe system. These findings were compared with corresponding data given in the literature, which were derived from calorimetric experiments and from the cellular atomic model of alloys described by Miedema.

Schlüsselwörter

  • Mössbauer spectroscopy
  • binding energy
  • short-range order
  • enthalpy of solution
  • enthalpy of mixing
  • binary alloys
Uneingeschränkter Zugang

Compositional dependence of hyperfine interactions and magnetoelectric coupling in (BiFeO3)x-(BaTiO3)1–x solid solutions

Online veröffentlicht: 09 Jun 2017
Seitenbereich: 117 - 122

Zusammenfassung

Abstract

In this work the compositional dependence of hyperfine interactions and magnetoelectric coupling in (BiFeO3)x-(BaTiO3)1-x solid solutions where x = 0.5-0.9 fabricated from commercial BaTiO3 in terms of the solid-state sintering method at various temperatures and over different time periods is described. In general, as the content of BaTiO3 increases, a decrease in the hyperfine magnetic field (Bhf) at 57Fe nuclei was observed. However, for samples exhibiting lower homogeneity in which the ions of Bi3+ and Fe3+ are replaced by Ba2+ and Ti4+ with lower probability, higher values of Bhf are obtained. For the sample where x = 0.6 that exhibits the coexistence of rhombohedral, regular and tetragonal phases, the highest value of the αME coefficient (3.57 mV/A) was observed, which is more than three times higher when compared to the hitherto published results.

Schlüsselwörter

  • hyperfine interactions
  • magnetoelectric coupling
  • Mössbauer spectroscopy
Uneingeschränkter Zugang

Spin reorientation process in Tm2–xHoxFe14B – analysis of conical arrangement based on Mössbauer spectra

Online veröffentlicht: 09 Jun 2017
Seitenbereich: 123 - 127

Zusammenfassung

Abstract

The spin reorientation process in the Tm2-xHoxFe14B series of compounds was studied using 57Fe Mössbauer spectroscopy over the temperature range 5.2-320 K with a focus on the analysis of conical spin arrangement. Each compound was studied by precise Mössbauer scanning in the vicinity of the transition and during the transition. By applying computer simulations based on the simplified Yamada-Kato model, as well as on some literature data for R2Fe14B (R = Tm, Ho) compounds, the above series was selected for studies as it contains compounds with different spin arrangements (axial, planar, conical). It was a crucial requirement for obtaining unambiguous angular dependences when applying a simultaneous fitting procedure of Mössbauer spectra. Such an extended procedure was applied which allowed the temperature dependence of the angle describing the position of the magnetization vector to be obtained. The results were compared with those from theoretical simulations. The spin arrangement diagram was constructed. A conical spin arrangement was confirmed over a wide temperature range.

Schlüsselwörter

  • permanent magnetic materials
  • Mössbauer effect
  • spin reorientation
  • spin diagrams
Uneingeschränkter Zugang

Mössbauer and heat capacity studies of ErZnSn2

Online veröffentlicht: 09 Jun 2017
Seitenbereich: 129 - 133

Zusammenfassung

Abstract

Heat capacity results obtained for the intermetallic compound ErZnSn2 were re-analysed to also consider, apart from the classical Debye model, the anharmonicity of the crystal lattice and the proper set of Einstein modes. The 119mSn Mössbauer technique was applied to derive the hyperfine interaction parameters characteristic of the two inequivalent crystallographic Sn sites in the compound studied. Quadrupole interaction constants, as measured by 119mSn Mössbauer spectroscopy, allowed for estimations of Vzz components of the electric field gradient tensor that exist at both Sn sites in the discussed compound.

Schlüsselwörter

  • ternary rare-earth intermetallics
  • heat capacity
  • Mössbauer spectroscopy
Uneingeschränkter Zugang

Hyperfine interactions and some thermomagnetic properties of amorphous FeZr(Cr)NbBCu alloys

Online veröffentlicht: 09 Jun 2017
Seitenbereich: 135 - 140

Zusammenfassung

Abstract

In this research, we studied the magnetic phase transition by Mössbauer spectroscopy and using vibrating sample magnetometer for amorphous Fe86-xZr7CrxNb2Cu1B4 (x = 0 or 6) alloys in the as-quenched state and after accumulative annealing in the temperature range 600-750 K. The Mössbauer investigations were carried out at room and nitrogen temperatures. The Mössbauer spectra of the investigated alloys at room temperature are characteristic of amorphous paramagnets and have a form of asymmetric doublets. However, at nitrogen temperature, the alloys behave like ferromagnetic amorphous materials. The two components are distinguished in the spectrum recorded at both room and nitrogen temperatures. The low field component in the distribution of hyperfine field induction shifts towards higher field with the annealing temperature. It is assumed that during annealing at higher temperature, due to diffusion processes, the grains of α-Fe are created in the area corresponding to this component. Both investigated alloys show the invar effect and the decrease of hyperfine field induction after annealing at 600 K for 10 min is observed. It is accompanied by the lowering of Curie temperature.

Schlüsselwörter

  • amorphous Fe-based alloys
  • invar effect
  • Mössbauer spectroscopy
Uneingeschränkter Zugang

Preliminary results of 57Fe Mössbauer spectroscopy of metamict samarskite after one-hour high temperature annealing in argon

Online veröffentlicht: 09 Jun 2017
Seitenbereich: 141 - 144

Zusammenfassung

Abstract

The preliminary results of 57Fe Mössbauer spectroscopy and X-ray diffraction (XRD) of fully metamict samarskite dated at ~1500 Ma, which absorbed α-dose of 6.5 × 1017 α-decay mg-1, are reported after one-hour annealing at 673, 873, 1173 and 1373 K in argon atmosphere. Metamict minerals contain radioactive elements that degrade their crystal structures over geological time. All the Mössbauer spectra obtained can be fitted to two quadrupole doublets assigned to Fe2+ and Fe3+ in octahedral positions. The relative contribution of Fe2+ (Fe2+/Fe) reaches a minimum of 0.10 at 1173 K.

Schlüsselwörter

  • samarskite
  • metamict minerals
  • Mössbauer spectroscopy
  • recrystallization
Uneingeschränkter Zugang

Identification of iron-bearing minerals in basalts and pillow lavas of the Kaczawa Mountains using 57Fe Mössbauer spectroscopy

Online veröffentlicht: 09 Jun 2017
Seitenbereich: 145 - 148

Zusammenfassung

Abstract

The Kaczawa Mountains along with the Kaczawa foothill comprise a complicated geological unit that is called the Kaczawa metamorphic (Sudetes, SW Poland). The aim of our work was to identify the iron-bearing minerals in samples of basalts and pillow lavas from the Kaczawa metamorphic using 57Fe Mössbauer spectroscopy. Based on the preliminary results, the Fe3+/Fe2+ ratio in the samples was determined.

Schlüsselwörter

  • Kaczawa Mountains
  • Mössbauer spectroscopy
  • basalts
  • pillow lavas
Uneingeschränkter Zugang

Effect of BaTiO3 concentration on structural and magnetic properties of mechanically activated BiFeO3-BaTiO3 system

Online veröffentlicht: 09 Jun 2017
Seitenbereich: 149 - 152

Zusammenfassung

Abstract

In this research, the mechanical activation method is proposed as an alternative process of preparation of the (BiFeO3)1-x-(BaTiO3)x solid solutions with various concentrations of barium titanate (x = 0.1÷0.9). However, mechanical milling itself does not allow obtaining the desired products and additional thermal treatment is needed to complete the solid-state reaction. In the present studies, X-ray diffraction and 57Fe Mössbauer spectroscopy were applied as complementary methods in order to study the structural and magnetic properties of materials. The investigations revealed that an increase of BaTiO3 concentration causes changes in the crystalline and hyperfine magnetic structure of the studied (BiFeO3)1-x-(BaTiO3)x system.

Schlüsselwörter

  • solid solutions
  • mechanical activation
  • X-ray diffraction
  • Mössbauer spectroscopy
Uneingeschränkter Zugang

A comparative study of hyperfine interactions in Aurivillius compounds prepared by mechanical activation and solid-state sintering

Online veröffentlicht: 09 Jun 2017
Seitenbereich: 153 - 157

Zusammenfassung

Abstract

X-ray diffraction and Mössbauer spectroscopy techniques were used to study the structure and hyperfine interactions of multiferroic Aurivillius compounds Bim+1Ti3Fem-3O3m+3. Samples were synthesized by two methods, that is, the solid-state sintering at various temperatures and mechanical activation in a high-energy ball mill. The compounds were obtained from a mixture of three polycrystalline powder oxides, that is, TiO2, Fe2O3 and Bi2O3. At room temperature, the Aurivillius compounds are paramagnetic materials with orthorhombic crystal structure. The c lattice parameter of the unit cell depends linearly on the m − number of layers with perovskite-like structure. Based on the Mössbauer studies, it is concluded that the hyperfine interactions parameters do not change with m number.

Schlüsselwörter

  • Aurivillius compounds
  • solid-state sintering
  • mechanical activation
  • Mössbauer spectroscopy
  • hyperfine interactions
Uneingeschränkter Zugang

An example of the application of Mössbauer spectroscopy for determination of concentration of iron in lyophilized brain tissue

Online veröffentlicht: 09 Jun 2017
Seitenbereich: 159 - 163

Zusammenfassung

Abstract

Mössbauer spectroscopy is not routinely used for the determination of the concentration of iron. However, as this method does not need any pre-treatment of samples before measurements, it may be of extreme importance for the assessment of iron in samples, which can then be used for further investigations. Biological samples are a good example, however, as the concentrations of iron are very low in these, it is important to exclude possible artefacts from the background spectrum related to iron present in the counter and cryostat windows. The aim of this study was to compare two methods of determination of the amounts of iron in investigated sample: one, in which the background spectrum was subtracted from the sample spectrum measured, and the other, in which the obtained non-elaborated spectrum was fitted with two doublets - a doublet for the measured sample and a doublet for the background spectrum. Three samples containing known amounts of natural iron (400, 800 and 1600 μg) and a sample of lyophilized human brain tissue obtained from globus pallidus were assessed. Both methods led to the creation of a very good calibration curve with a correlation coefficient of 0.99. Although both methods gave similar results for the concentration of iron in the sample, the subtraction of the background spectrum had a significantly lower error of the final result.

Schlüsselwörter

  • Mössbauer spectroscopy
  • background spectrum
  • iron concentration
  • brain tissue
  • calibration curve
Uneingeschränkter Zugang

Synthesis and characterization of AgFeO2 delafossite with non-stoichiometric silver concentration

Online veröffentlicht: 09 Jun 2017
Seitenbereich: 165 - 170

Zusammenfassung

Abstract

The simple co-precipitation method was used to prepare AgxFeO2 delafossite with non-stoichiometric silver concentration in the range of x = 0.05-1. The obtained material was investigated using X-ray powder diffraction and 57Fe Mössbauer spectroscopy at room temperature. The structural and hyperfi ne interaction parameters were recognized in relation with decreasing silver concentration. The study revealed that the delafossite structure of AgxFeO2 was maintained up to x = 0.9; as the range of silver concentration was decreased to 0.05 ≤ x ≤ 0.8, a mixture of AgFeO2, Fe2O3 or/and FeOOH was formed.

Schlüsselwörter

  • delafossite
  • silver ferrite
  • co-precipitation
  • hyperfine interactions
  • Mössbauer spectroscopy
Uneingeschränkter Zugang

Metallurgical quality evaluation of the wind turbine main shaft 42CrMo4 steel: microscopic and Mössbauer studies

Online veröffentlicht: 09 Jun 2017
Seitenbereich: 171 - 176

Zusammenfassung

Abstract

In this paper, the results of the complex examination of the 42CrMo4 steel samples are presented. The samples were taken from the metallurgical forging prepared for the production of the wind turbine main shaft. The samples underwent Mössbauer spectroscopic analysis, as well as the measurement of its mechanical characteristics such as hardness and strength are analysed. Conversion electron Mössbauer spectrometry confirmed phase purity and isotropy of the investigated 42CrMo4 steel. The method provided accurate results, proving Mössbauer spectrometry to be an effective tool for the wind turbine main shaft analysis.

Schlüsselwörter

  • metallurgical forging
  • wind turbine
  • Mössbauer spectrometry
Uneingeschränkter Zugang

Crystal structure and Mössbauer effect in multiferroic 0.5BiFeO3-0.5Pb(Fe0.5Ta0.5)O3 solid solution

Online veröffentlicht: 09 Jun 2017
Seitenbereich: 177 - 181

Zusammenfassung

Abstract

Multiferroic 0.5BiFeO3-0.5Pb(Fe0.5Ta0.5)O3 solid solution is a material that exhibits ferroelectric and antiferromagnetic orderings in ambient temperature. The solid solution was obtained as a result of a conventional reaction in a solid state. The obtained material is a dense, fine-grained sinter whose surface was observed by scanning electron microscopy (SEM) and stoichiometry was confirmed by energy dispersive X-ray spectroscopic (EDS) analysis. According to the X-ray powder diffraction (XRD) measurements, the main phase is R3c space group with admixture of Pm-3m regular phase. Small contribution of pyrochlore-like phase was also observed. Mössbauer spectroscopy suggested random distribution of Fe3+/Ta5+ cations in the B sites of ABO3 compound. Reduction of the magnetic hyperfine field with an increase in the substitution of Ta5+ in Fe3+ neighbourhood was also observed.

Schlüsselwörter

  • BiFeO3
  • crystal structure
  • hyperfine interactions
  • multiferroics
  • solid solution
Uneingeschränkter Zugang

Investigation of magnetite Fe3O4 nanoparticles for magnetic hyperthermia

Online veröffentlicht: 09 Jun 2017
Seitenbereich: 183 - 186

Zusammenfassung

Abstract

The paper presents the investigation of magnetic nanoparticles (MNPs) dedicated to hyperthermia application. The crystal structure and size distributions have been determined by means of transmission electron microscope (TEM) and X-ray diffraction (XRD). Magnetic properties of the nanoparticles were tested by Mössbauer spectroscopy together with calorimetric experiments. The Mössbauer spectroscopic study of MNPs revealed the existence of a superparamagnetic phase. The relative contribution of the relaxing component to the total spectrum at room temperature was about 10%. The heating effect of these MNPs under alternating magnetic field was examined. The temperature increase has reached 5°C in 10 min. The preliminary temperature rise suggests that the investigated materials are applicable for hyperthermia.

Schlüsselwörter

  • Mössbauer effect
  • superparamagnetic nanoparticles
  • hyperthermia
Uneingeschränkter Zugang

Iron-containing phases in metallurgical and coke dusts as well as in bog iron ore

Online veröffentlicht: 09 Jun 2017
Seitenbereich: 187 - 195

Zusammenfassung

Abstract

Several samples of dusts from steel and coke plants (collected mostly with electro filters) were subjected to the investigation of content of mineral phases in their particles. Additionally, sample of bog iron ore and metallurgical slurry was studied. Next, the magnetic susceptibility of all the samples was determined, and investigations of iron-containing phases were performed using transmission Mössbauer spectrometry. The values of mass-specific magnetic susceptibility χ varied in a wide range: from 59 to above 7000 × 10−8 m-3·kg−1. The low values are determined for bog iron ore, metallurgical slurry, and coke dusts. The extremely high χ was obtained for metallurgical dusts. The Mössbauer spectra and X-ray diffraction patterns point to the presence of the following phases containing iron: hematite and oxidized magnetite (in coke and metallurgical dusts as well as metallurgical slurry), traces of magnetite fine grains fraction (in metallurgical dusts), amorphous glassy silicates with paramagnetic Fe3+ and Fe2+ ions, traces of pyrrhotite (in coke dusts), α-Fe and nonstoichiometric wüstite (in metallurgical slurry), as well as ferrihydrite nanoparticles (in bog iron ore). For individual samples of metallurgical dusts, the relative contributions of Fe2+/3+ ions in octahedral B sites and Fe2+ ions in tetrahedral A sites in magnetite spinel structure differs considerably.

Schlüsselwörter

  • metallurgical dusts
  • coke dusts
  • bog ore
  • phase analysis
  • Mössbauer spectrometry
  • magnetic susceptibility
21 Artikel
Uneingeschränkter Zugang

Synthesis and characterization of iron oxide magnetic nanoparticles

Online veröffentlicht: 09 Jun 2017
Seitenbereich: 73 - 77

Zusammenfassung

Abstract

Small particles of magnetite, i.e. 7.5, 13.4 and 14.1 nm in diameter, were obtained by the method of co-precipitation. The crystal structure and size distributions were determined by means of transmission electron microscopy and X-ray diffraction. The magnetic properties of the nanoparticles were tested by Mössbauer spectroscopy within the temperature range from 3 K to room temperature (RT). The Mössbauer study of magnetic nanoparticles reveals relaxation behaviour related to the existence of the superparamagnetic phase. The blocking temperature depends on the sizes of the nanoparticles and the ammonia concentration.

Schlüsselwörter

  • Mössbauer effect
  • superparamagnetic nanoparticles
Uneingeschränkter Zugang

Mössbauer and magnetic studies of FeCoNiCuNbSiB nanocrystalline alloys

Online veröffentlicht: 09 Jun 2017
Seitenbereich: 79 - 84

Zusammenfassung

Abstract

Nanocrystalline Fe80-x-yCoxNiyCu1Nb3Si4B12 alloys were prepared by the annealing of amorphous ribbons. Primary crystallization of the alloys annealed at temperatures of between 500 and 550°C was studied by X-ray diffraction and Mössbauer spectroscopy. Magnetic properties of the alloys were investigated using a hysteresis loop tracer and vibrating sample magnetometer. The annealed ribbons are composed of a two-phase nanostructure consisting of bcc Fe-based grains embedded in an amorphous matrix. Conversion electron Mössbauer spectroscopy (CEMS) measurements reveal a more advanced crystallization process in the surface layers when compared with the volume of the ribbons. The degree of saturation magnetization of the nanocrystalline alloys is of about 1.5 T. The coercive field varies from 1.0 to 6.5 A/m and peaks at an annealing temperature of 525°C. Magnetic softening of the nanocrystalline alloys observed after annealing at 550°C is correlated with a volume fraction of the nanocrystalline bcc phase.

Schlüsselwörter

  • amorphous ribbons
  • nanocrystalline alloys
  • Mössbauer spectroscopy
  • soft magnetic properties
Uneingeschränkter Zugang

Microstructure and magnetic properties of amorphous Fe51Co12Si16B8Mo5P8 alloy

Online veröffentlicht: 09 Jun 2017
Seitenbereich: 85 - 89

Zusammenfassung

Abstract

Microstructure and thermomagnetic characteristics of the amorphous Fe51Co12Si16B8Mo5P8 alloy in the as-quenched state and after 1 h of annealing at 573 K and 773 K are studied. The structural investigations performed by Mössbauer spectroscopy and X-ray diffractometry confirmed the amorphous structure of the analysed materials. An increase in the annealing temperature up to 773 K does not lead to crystallization of the amorphous alloy. Only structural rearrangement that causes changes in the topological short-range order and annealing out of free volume is observed. This behaviour was confirmed by modifications of the shapes of hyperfine field distributions derived from the corresponding Mössbauer spectra of the investigated alloys. The Curie temperatures of the as-quenched and annealed Fe51Co12Si16B8Mo5P8 alloy at 573 and 773 K are 400, 405 and 421 K, respectively.

Schlüsselwörter

  • microstructure
  • Mössbauer spectroscopy
  • magnetic properties
  • Curie point
Uneingeschränkter Zugang

Features of the structural and magnetic properties of Pb(TixZr1–xO3)-NiFe1.98Co0.02O4 in the polarized state

Online veröffentlicht: 09 Jun 2017
Seitenbereich: 91 - 94

Zusammenfassung

Abstract

Composites with a 90%Pb(TixZr1-xO3)-10%NiFe1.98Co0.02O4 composition have been synthesized. It has been established that the polarization of samples resulting from exposure to an electric field for 1 hour of 4 kV/mm in strength at a temperature of 400 K leads to crystal structure deformation. The compression of elementary crystal cells in some areas during polarization of the sample creates conditions suitable for the enhancement of magnetic exchange interactions. It has been found that the polarization process of such compositions leads to increases in specific magnetization and magnetic susceptibility. The analysis of Mössbauer spectra has shown that the polarization of the 90%Pb(TixZr1-xO3)-10%NiFe1.98Co0.02O4 composite leads to significant changes in the effective magnetic fields of iron subspectra in various positions.

Schlüsselwörter

  • Mössbauer effect
  • X-ray diffraction
  • lead zirconate titanate (PZT)
  • unpolarized and polarized states
  • specific magnetization
  • magnetic susceptibility
  • effective magnetic fields
Uneingeschränkter Zugang

Structural properties of Mn-substituted hercynite

Online veröffentlicht: 09 Jun 2017
Seitenbereich: 95 - 100

Zusammenfassung

Abstract

In this work spinel series with the general formula Fe1-xMnxAl2O4 (where x = 0, 0.3, 0.5 and 0.7) were synthesized and characterized with respect to their structure and microstructure. X-ray diffractometry (XRD) was used to identify the phase composition that revealed a single phase spinel material. Rietveld refinements of the XRD patterns were carried out in order to determine the lattice and oxygen positional parameters of the spinel compounds. Mössbauer effect measurements were performed at room temperature to determine the local chemical environment of the Fe ions, their valences, and degrees of spinels inversion. It was shown that an increase in the Mn content led to a decrease in the ratio of Fe2+ to Fe3+. The results obtained from Mössbauer spectroscopy (MS) were used to establish the chemical formulas of the synthesized spinels. Finally, the microstructure that was observed using scanning electron microscopy (SEM) showed a compact microstructure with an octahedral crystal habit.

Schlüsselwörter

  • FeAl2O4
  • MnAl2O4
  • hercynite
  • spinel
  • galaxite
  • Mössbauer spectroscopy
Uneingeschränkter Zugang

57Fe Mössbauer spectroscopy investigations of iron phase composition in fluidized beds from the ELCHO power plant in Chorzów, Poland

Online veröffentlicht: 09 Jun 2017
Seitenbereich: 101 - 107

Zusammenfassung

Abstract

The study investigates the physical and chemical properties of fly ash and bottom ash from a power plant ELCHO in Chorzów, Poland. Coal combustion products generated in the process of combustion in circulating fluidized beds (CFBs) are considerably different from fly and bottom ashes obtained from dust furnaces and multi-layer ones. The composition of the iron-bearing phase in the waste of circulating fluidized bed combustion was determined using Mössbauer spectroscopy and X-ray powder diffraction (XRD) methods.

Schlüsselwörter

  • Mössbauer spectroscopy
  • fly ash
  • bottom ash
Uneingeschränkter Zugang

Thermodynamic properties of dilute Co-Fe solid solutions studied by 57Fe Mössbauer spectroscopy

Online veröffentlicht: 09 Jun 2017
Seitenbereich: 109 - 115

Zusammenfassung

Abstract

The Co1-xFex alloys where x ranges from 0.01 to 0.06 were measured at room temperature using transmission Mössbauer spectroscopy (TMS). The analysis of the obtained data allowed the determination of the short-range order (SRO), the binding energy Eb between two iron atoms in the studied materials using the extended Hrynkiewicz-Królas idea and the enthalpy of solution HCo-Fe of Fe in Co. The results showed that the Fe atoms dissolved in a Co matrix interact repulsively and the estimated value of HCo-Fe = -0.166(33) eV/atom. Finally, values of the enthalpy of solution were used to predict the enthalpy of mixing for the Co-Fe system. These findings were compared with corresponding data given in the literature, which were derived from calorimetric experiments and from the cellular atomic model of alloys described by Miedema.

Schlüsselwörter

  • Mössbauer spectroscopy
  • binding energy
  • short-range order
  • enthalpy of solution
  • enthalpy of mixing
  • binary alloys
Uneingeschränkter Zugang

Compositional dependence of hyperfine interactions and magnetoelectric coupling in (BiFeO3)x-(BaTiO3)1–x solid solutions

Online veröffentlicht: 09 Jun 2017
Seitenbereich: 117 - 122

Zusammenfassung

Abstract

In this work the compositional dependence of hyperfine interactions and magnetoelectric coupling in (BiFeO3)x-(BaTiO3)1-x solid solutions where x = 0.5-0.9 fabricated from commercial BaTiO3 in terms of the solid-state sintering method at various temperatures and over different time periods is described. In general, as the content of BaTiO3 increases, a decrease in the hyperfine magnetic field (Bhf) at 57Fe nuclei was observed. However, for samples exhibiting lower homogeneity in which the ions of Bi3+ and Fe3+ are replaced by Ba2+ and Ti4+ with lower probability, higher values of Bhf are obtained. For the sample where x = 0.6 that exhibits the coexistence of rhombohedral, regular and tetragonal phases, the highest value of the αME coefficient (3.57 mV/A) was observed, which is more than three times higher when compared to the hitherto published results.

Schlüsselwörter

  • hyperfine interactions
  • magnetoelectric coupling
  • Mössbauer spectroscopy
Uneingeschränkter Zugang

Spin reorientation process in Tm2–xHoxFe14B – analysis of conical arrangement based on Mössbauer spectra

Online veröffentlicht: 09 Jun 2017
Seitenbereich: 123 - 127

Zusammenfassung

Abstract

The spin reorientation process in the Tm2-xHoxFe14B series of compounds was studied using 57Fe Mössbauer spectroscopy over the temperature range 5.2-320 K with a focus on the analysis of conical spin arrangement. Each compound was studied by precise Mössbauer scanning in the vicinity of the transition and during the transition. By applying computer simulations based on the simplified Yamada-Kato model, as well as on some literature data for R2Fe14B (R = Tm, Ho) compounds, the above series was selected for studies as it contains compounds with different spin arrangements (axial, planar, conical). It was a crucial requirement for obtaining unambiguous angular dependences when applying a simultaneous fitting procedure of Mössbauer spectra. Such an extended procedure was applied which allowed the temperature dependence of the angle describing the position of the magnetization vector to be obtained. The results were compared with those from theoretical simulations. The spin arrangement diagram was constructed. A conical spin arrangement was confirmed over a wide temperature range.

Schlüsselwörter

  • permanent magnetic materials
  • Mössbauer effect
  • spin reorientation
  • spin diagrams
Uneingeschränkter Zugang

Mössbauer and heat capacity studies of ErZnSn2

Online veröffentlicht: 09 Jun 2017
Seitenbereich: 129 - 133

Zusammenfassung

Abstract

Heat capacity results obtained for the intermetallic compound ErZnSn2 were re-analysed to also consider, apart from the classical Debye model, the anharmonicity of the crystal lattice and the proper set of Einstein modes. The 119mSn Mössbauer technique was applied to derive the hyperfine interaction parameters characteristic of the two inequivalent crystallographic Sn sites in the compound studied. Quadrupole interaction constants, as measured by 119mSn Mössbauer spectroscopy, allowed for estimations of Vzz components of the electric field gradient tensor that exist at both Sn sites in the discussed compound.

Schlüsselwörter

  • ternary rare-earth intermetallics
  • heat capacity
  • Mössbauer spectroscopy
Uneingeschränkter Zugang

Hyperfine interactions and some thermomagnetic properties of amorphous FeZr(Cr)NbBCu alloys

Online veröffentlicht: 09 Jun 2017
Seitenbereich: 135 - 140

Zusammenfassung

Abstract

In this research, we studied the magnetic phase transition by Mössbauer spectroscopy and using vibrating sample magnetometer for amorphous Fe86-xZr7CrxNb2Cu1B4 (x = 0 or 6) alloys in the as-quenched state and after accumulative annealing in the temperature range 600-750 K. The Mössbauer investigations were carried out at room and nitrogen temperatures. The Mössbauer spectra of the investigated alloys at room temperature are characteristic of amorphous paramagnets and have a form of asymmetric doublets. However, at nitrogen temperature, the alloys behave like ferromagnetic amorphous materials. The two components are distinguished in the spectrum recorded at both room and nitrogen temperatures. The low field component in the distribution of hyperfine field induction shifts towards higher field with the annealing temperature. It is assumed that during annealing at higher temperature, due to diffusion processes, the grains of α-Fe are created in the area corresponding to this component. Both investigated alloys show the invar effect and the decrease of hyperfine field induction after annealing at 600 K for 10 min is observed. It is accompanied by the lowering of Curie temperature.

Schlüsselwörter

  • amorphous Fe-based alloys
  • invar effect
  • Mössbauer spectroscopy
Uneingeschränkter Zugang

Preliminary results of 57Fe Mössbauer spectroscopy of metamict samarskite after one-hour high temperature annealing in argon

Online veröffentlicht: 09 Jun 2017
Seitenbereich: 141 - 144

Zusammenfassung

Abstract

The preliminary results of 57Fe Mössbauer spectroscopy and X-ray diffraction (XRD) of fully metamict samarskite dated at ~1500 Ma, which absorbed α-dose of 6.5 × 1017 α-decay mg-1, are reported after one-hour annealing at 673, 873, 1173 and 1373 K in argon atmosphere. Metamict minerals contain radioactive elements that degrade their crystal structures over geological time. All the Mössbauer spectra obtained can be fitted to two quadrupole doublets assigned to Fe2+ and Fe3+ in octahedral positions. The relative contribution of Fe2+ (Fe2+/Fe) reaches a minimum of 0.10 at 1173 K.

Schlüsselwörter

  • samarskite
  • metamict minerals
  • Mössbauer spectroscopy
  • recrystallization
Uneingeschränkter Zugang

Identification of iron-bearing minerals in basalts and pillow lavas of the Kaczawa Mountains using 57Fe Mössbauer spectroscopy

Online veröffentlicht: 09 Jun 2017
Seitenbereich: 145 - 148

Zusammenfassung

Abstract

The Kaczawa Mountains along with the Kaczawa foothill comprise a complicated geological unit that is called the Kaczawa metamorphic (Sudetes, SW Poland). The aim of our work was to identify the iron-bearing minerals in samples of basalts and pillow lavas from the Kaczawa metamorphic using 57Fe Mössbauer spectroscopy. Based on the preliminary results, the Fe3+/Fe2+ ratio in the samples was determined.

Schlüsselwörter

  • Kaczawa Mountains
  • Mössbauer spectroscopy
  • basalts
  • pillow lavas
Uneingeschränkter Zugang

Effect of BaTiO3 concentration on structural and magnetic properties of mechanically activated BiFeO3-BaTiO3 system

Online veröffentlicht: 09 Jun 2017
Seitenbereich: 149 - 152

Zusammenfassung

Abstract

In this research, the mechanical activation method is proposed as an alternative process of preparation of the (BiFeO3)1-x-(BaTiO3)x solid solutions with various concentrations of barium titanate (x = 0.1÷0.9). However, mechanical milling itself does not allow obtaining the desired products and additional thermal treatment is needed to complete the solid-state reaction. In the present studies, X-ray diffraction and 57Fe Mössbauer spectroscopy were applied as complementary methods in order to study the structural and magnetic properties of materials. The investigations revealed that an increase of BaTiO3 concentration causes changes in the crystalline and hyperfine magnetic structure of the studied (BiFeO3)1-x-(BaTiO3)x system.

Schlüsselwörter

  • solid solutions
  • mechanical activation
  • X-ray diffraction
  • Mössbauer spectroscopy
Uneingeschränkter Zugang

A comparative study of hyperfine interactions in Aurivillius compounds prepared by mechanical activation and solid-state sintering

Online veröffentlicht: 09 Jun 2017
Seitenbereich: 153 - 157

Zusammenfassung

Abstract

X-ray diffraction and Mössbauer spectroscopy techniques were used to study the structure and hyperfine interactions of multiferroic Aurivillius compounds Bim+1Ti3Fem-3O3m+3. Samples were synthesized by two methods, that is, the solid-state sintering at various temperatures and mechanical activation in a high-energy ball mill. The compounds were obtained from a mixture of three polycrystalline powder oxides, that is, TiO2, Fe2O3 and Bi2O3. At room temperature, the Aurivillius compounds are paramagnetic materials with orthorhombic crystal structure. The c lattice parameter of the unit cell depends linearly on the m − number of layers with perovskite-like structure. Based on the Mössbauer studies, it is concluded that the hyperfine interactions parameters do not change with m number.

Schlüsselwörter

  • Aurivillius compounds
  • solid-state sintering
  • mechanical activation
  • Mössbauer spectroscopy
  • hyperfine interactions
Uneingeschränkter Zugang

An example of the application of Mössbauer spectroscopy for determination of concentration of iron in lyophilized brain tissue

Online veröffentlicht: 09 Jun 2017
Seitenbereich: 159 - 163

Zusammenfassung

Abstract

Mössbauer spectroscopy is not routinely used for the determination of the concentration of iron. However, as this method does not need any pre-treatment of samples before measurements, it may be of extreme importance for the assessment of iron in samples, which can then be used for further investigations. Biological samples are a good example, however, as the concentrations of iron are very low in these, it is important to exclude possible artefacts from the background spectrum related to iron present in the counter and cryostat windows. The aim of this study was to compare two methods of determination of the amounts of iron in investigated sample: one, in which the background spectrum was subtracted from the sample spectrum measured, and the other, in which the obtained non-elaborated spectrum was fitted with two doublets - a doublet for the measured sample and a doublet for the background spectrum. Three samples containing known amounts of natural iron (400, 800 and 1600 μg) and a sample of lyophilized human brain tissue obtained from globus pallidus were assessed. Both methods led to the creation of a very good calibration curve with a correlation coefficient of 0.99. Although both methods gave similar results for the concentration of iron in the sample, the subtraction of the background spectrum had a significantly lower error of the final result.

Schlüsselwörter

  • Mössbauer spectroscopy
  • background spectrum
  • iron concentration
  • brain tissue
  • calibration curve
Uneingeschränkter Zugang

Synthesis and characterization of AgFeO2 delafossite with non-stoichiometric silver concentration

Online veröffentlicht: 09 Jun 2017
Seitenbereich: 165 - 170

Zusammenfassung

Abstract

The simple co-precipitation method was used to prepare AgxFeO2 delafossite with non-stoichiometric silver concentration in the range of x = 0.05-1. The obtained material was investigated using X-ray powder diffraction and 57Fe Mössbauer spectroscopy at room temperature. The structural and hyperfi ne interaction parameters were recognized in relation with decreasing silver concentration. The study revealed that the delafossite structure of AgxFeO2 was maintained up to x = 0.9; as the range of silver concentration was decreased to 0.05 ≤ x ≤ 0.8, a mixture of AgFeO2, Fe2O3 or/and FeOOH was formed.

Schlüsselwörter

  • delafossite
  • silver ferrite
  • co-precipitation
  • hyperfine interactions
  • Mössbauer spectroscopy
Uneingeschränkter Zugang

Metallurgical quality evaluation of the wind turbine main shaft 42CrMo4 steel: microscopic and Mössbauer studies

Online veröffentlicht: 09 Jun 2017
Seitenbereich: 171 - 176

Zusammenfassung

Abstract

In this paper, the results of the complex examination of the 42CrMo4 steel samples are presented. The samples were taken from the metallurgical forging prepared for the production of the wind turbine main shaft. The samples underwent Mössbauer spectroscopic analysis, as well as the measurement of its mechanical characteristics such as hardness and strength are analysed. Conversion electron Mössbauer spectrometry confirmed phase purity and isotropy of the investigated 42CrMo4 steel. The method provided accurate results, proving Mössbauer spectrometry to be an effective tool for the wind turbine main shaft analysis.

Schlüsselwörter

  • metallurgical forging
  • wind turbine
  • Mössbauer spectrometry
Uneingeschränkter Zugang

Crystal structure and Mössbauer effect in multiferroic 0.5BiFeO3-0.5Pb(Fe0.5Ta0.5)O3 solid solution

Online veröffentlicht: 09 Jun 2017
Seitenbereich: 177 - 181

Zusammenfassung

Abstract

Multiferroic 0.5BiFeO3-0.5Pb(Fe0.5Ta0.5)O3 solid solution is a material that exhibits ferroelectric and antiferromagnetic orderings in ambient temperature. The solid solution was obtained as a result of a conventional reaction in a solid state. The obtained material is a dense, fine-grained sinter whose surface was observed by scanning electron microscopy (SEM) and stoichiometry was confirmed by energy dispersive X-ray spectroscopic (EDS) analysis. According to the X-ray powder diffraction (XRD) measurements, the main phase is R3c space group with admixture of Pm-3m regular phase. Small contribution of pyrochlore-like phase was also observed. Mössbauer spectroscopy suggested random distribution of Fe3+/Ta5+ cations in the B sites of ABO3 compound. Reduction of the magnetic hyperfine field with an increase in the substitution of Ta5+ in Fe3+ neighbourhood was also observed.

Schlüsselwörter

  • BiFeO3
  • crystal structure
  • hyperfine interactions
  • multiferroics
  • solid solution
Uneingeschränkter Zugang

Investigation of magnetite Fe3O4 nanoparticles for magnetic hyperthermia

Online veröffentlicht: 09 Jun 2017
Seitenbereich: 183 - 186

Zusammenfassung

Abstract

The paper presents the investigation of magnetic nanoparticles (MNPs) dedicated to hyperthermia application. The crystal structure and size distributions have been determined by means of transmission electron microscope (TEM) and X-ray diffraction (XRD). Magnetic properties of the nanoparticles were tested by Mössbauer spectroscopy together with calorimetric experiments. The Mössbauer spectroscopic study of MNPs revealed the existence of a superparamagnetic phase. The relative contribution of the relaxing component to the total spectrum at room temperature was about 10%. The heating effect of these MNPs under alternating magnetic field was examined. The temperature increase has reached 5°C in 10 min. The preliminary temperature rise suggests that the investigated materials are applicable for hyperthermia.

Schlüsselwörter

  • Mössbauer effect
  • superparamagnetic nanoparticles
  • hyperthermia
Uneingeschränkter Zugang

Iron-containing phases in metallurgical and coke dusts as well as in bog iron ore

Online veröffentlicht: 09 Jun 2017
Seitenbereich: 187 - 195

Zusammenfassung

Abstract

Several samples of dusts from steel and coke plants (collected mostly with electro filters) were subjected to the investigation of content of mineral phases in their particles. Additionally, sample of bog iron ore and metallurgical slurry was studied. Next, the magnetic susceptibility of all the samples was determined, and investigations of iron-containing phases were performed using transmission Mössbauer spectrometry. The values of mass-specific magnetic susceptibility χ varied in a wide range: from 59 to above 7000 × 10−8 m-3·kg−1. The low values are determined for bog iron ore, metallurgical slurry, and coke dusts. The extremely high χ was obtained for metallurgical dusts. The Mössbauer spectra and X-ray diffraction patterns point to the presence of the following phases containing iron: hematite and oxidized magnetite (in coke and metallurgical dusts as well as metallurgical slurry), traces of magnetite fine grains fraction (in metallurgical dusts), amorphous glassy silicates with paramagnetic Fe3+ and Fe2+ ions, traces of pyrrhotite (in coke dusts), α-Fe and nonstoichiometric wüstite (in metallurgical slurry), as well as ferrihydrite nanoparticles (in bog iron ore). For individual samples of metallurgical dusts, the relative contributions of Fe2+/3+ ions in octahedral B sites and Fe2+ ions in tetrahedral A sites in magnetite spinel structure differs considerably.

Schlüsselwörter

  • metallurgical dusts
  • coke dusts
  • bog ore
  • phase analysis
  • Mössbauer spectrometry
  • magnetic susceptibility

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