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The catalytic activity of non-spherical shaped Fe3O4 nanoparticles synthesized by low cost co-precipitation method was tested. It was presented, that magnetite nanoparticles can be used to degrade not only Rhodamine B and Methylene Blue, but above all cancerogenic azo dye – Sudan I. It was confirmed, that the degradation of Rhodamine B can be described by pseudo-zero-order kinetic model, whereas degradation of Methylene Blue by pseudo-first-order kinetic model. The degradation mechanism of Sudan I by photo-Fenton reaction was proposed. It was noted, that this double-stage process can be associated with hydroxylation of Sudan I and degradation of derivates, such as 4′‑OH‑Sudan I and 6‑OH‑Sudan I. Therefore, it cannot be simple describe by one kinetic model. The introduction of hydroxyl group results in an increase of the absorbance, which in turn is associated with hyperchromic effect.

New compositions of Ca-based metallic glasses were studied in aim to reduce their rapid degradation in physiological body fluids. The studies were performed on Ca47Mg18Zn35-xAux (x = 0,1,3 at.%) samples in the form of plates. The effect of Au addition on the corrosion behavior of new Ca-based alloys in Ringer's solution was reported. It was found that the Ca47Mg18Zn34Au3 and Ca47Mg18Zn34Au1 glasses show more positive corrosion potential than Ca47Mg18Zn35 alloy. Moreover, samples with Au addition Ca47Mg18Zn34Au3 (0.18 ml/cm2) and Ca47Mg18Zn34Au1 (1.32 ml/cm2) exhibited significantly less hydrogen evolution rates than base alloy Ca47Mg18Zn35 (7.25 ml/cm2) after 7 h. The reduced hydrogen volumes of the alloys with Au addition indicated that they can be used for wide range of biomedical applications.

In this study, possibility of using different thermodynamic parameters, such as: ideal configurational entropy, mixing enthalpy, Gibbs free energy of mixing and mismatch entropy for determining chemical composition of Fe-Co based amorphous alloys was evaluated. The high role of entropy in formation of amorphous phase was confirmed, but maximization of the value of ideal configurational entropy did not allow to obtain fully amorphous alloy. The chemical composition of Fe35Co35Si11B19 amorphous alloy was determined based on minimization the value of Gibbs free energy of formation of amorphous phase – the new parameter proposed in this study. Herein, this new proposed parameter was also used to describe an influence of different chemical elements on glass forming ability of Zr, Cu and Fe based alloys. It was shown, that the Fe based amorphous alloys with the most negative value of Gibbs free energy of formation of amorphous phase were characterized by high thermal stability. The high thermal stability and glass forming ability of Fe35Co35Si11B19 amorphous alloy were confirmed by using differential thermal analysis, X-ray diffraction method, Mossbauer spectroscopy and differential scanning calorimetry. Additionally, influence of isothermal crystallization of Fe35Co35Si11B19 alloy on the structure and magnetic properties was described.

The corrosion behavior of Ca65−xMg10+xZn25 (x = 0,10) and Ca32Mg12Zn38Yb18 alloys was studied by potendiodynamic tests and electrochemical impedance spectroscopy in Ringer's solution. The solution of NaCl, KCl and CaCl2 components reacted with outer layer of alloys and produced corrosion products. The influence of Ca content on the hydrogen volume as a function of time was discussed. The measurements exhibited significantly less hydrogen evolution volumes for Ca55Mg20Zn25 alloy (5.0 ml/cm2) than for Ca65Mg10Zn25 glass (11.3 ml/cm2) after 2 h. The lowest value of hydrogen evolution was observed for Ca32Mg12Zn38Yb18 glass (1.1 ml/cm2). The hydrogen volume for Ca32Zn38Mg12Yb18 sample fulfilled the non-toxic amount of H2, which must be low than ~1 ml/h. The XPS survey spectra for the glassy samples after corrosion test in Ringer's solution represent the surface components. The corrosion products were identified as to be CaCO3, Mg(OH)2, CaO, MgO and ZnO compounds. In addition, the EDS and X-ray analysis of a layer of corrosion products after immersion tests in Ringer's solution identified calcium and ytterbium hydroxide, calcium carbonate and also calcium zinc hydroxide hydrate.

New resorbable Ca32Mg12Zn38Yb18-2xBxAux (x = 1,2) alloys were designed and prepared in order to verify their use for medical applications as potential short-term implants. Their amorphous structure containing some crystalline phases (CaZn, CaZn2 and MgZn) was determined by X-ray and neutron diffraction and electron microscopy methods. The biocorrosion behavior of the plates was tested by hydrogen evolution measurements, immersion, electrochemical polarization tests, and electrochemical impedance spectroscopy in Ringer’s solution at 37 C. The corrosion analysis was also supplemented by X-ray diffraction, photoelectron, and ICP-AES spectroscopy. The corrosion resistivity measurements revealed that the alloys manifest enhanced corrosion resistance. The corrosion current density for Ca32Mg12Zn38Yb18- 2xBxAux (x = 1, 2) alloys were 18.46 and 8.79 lA/cm2, which is lower than for pure Mg (47.85 lA/cm2) and Zn (33.96 lA/cm2). A decreasing tendency for hydrogen to evolve as a function of time was noted. The hydrogen evolution did not exceed 1 ml/cm2 over 1 h and average corrosion rate is calculated as 0.32 g/m2 . h for Ca32Mg12Zn38Yb14B2Au2 alloy after 312 h. The corrosion mechanism of the alloys includes an anodic dissolution, a hydroxide precipitation, corrosion product layer formation and corrosion propagation stage.

The corrosion activity of amorphous plates of Ca60Mg15Zn25 alloy was investigated. The biocompatible elements were selected for the alloy composition. The electrochemical corrosion and immersion tests were carried out in a multi-electrolyte fluid and Ringer's solution. Better corrosion behavior was observed for the samples tested in a multi-electrolyte fluid despite the active dissolution of Ca and Mg in Ringer's solution. The experimental results indicated that reducing concentration of NaCl from 8.6 g/dm3 for Ringer's solution to 5.75 g/dm3 caused the decrease of the corrosion rate. The volume of the hydrogen evolved after 480 min in Ringer's solution (40.1 ml/ cm2) was higher in comparison with that obtained in a multi-electrolyte fluid (24.4 ml/cm2). The values of opencircuit potential (EOCP) for the Ca60Mg15Zn25 glass after 1 h incubation in Ringer's solution and a multielectrolyte fluid were determined to be −1553 and −1536 mV vs. a saturated calomel electrode (SCE). The electrochemical measurements indicated a shift of the corrosion current density (jcorr) from 1062 μA/cm2 for the sample tested in Ringer's solution to 788 μA/cm2 for the specimen immersed in a multi-electrolyte fluid. The corrosion products analysis was conducted by using the X-ray photoelectron spectroscopy (XPS). The corrosion products were identified to be CaCO3, Mg(OH)2, CaO, MgO and ZnO. The mechanism of corrosion process was proposed and described based on the microscopic observations. The X-ray diffraction and Fourier transform infrared spectroscopy (FTIR) also indicated that Ca(OH)2, CaCO3, Zn(OH)2 and Ca(Zn(OH)3)2·2H2O mainly formed on the surface of the studied alloy., The work was supported by National Science Centre under research project no.: 2013/09/B/ST8/02129 .

The quaternary Ca 50 Mg 20 Cu 25 Zn 5 metallic glass in the form of ribbons and plates was successfully fabricated by melt-spinning and copper-mold casting. The structure characterization of the alloy in as-cast state was performed by using X-ray diffraction method. The Reverse Monte Carlo modeling was carried out to obtain structural model of the alloy in the form of ribbon. Moreover, the corrosion behavior of glassy plates was studied by electrochemical measurements and immersion tests in 1, 2 and 3.5% NaCl solution (pH = 5.4) at room temperature. As suspected the lowest corrosion activity of the alloy was observed in 1% NaCl solution. The post-corrosion tests were conducted by scanning electron microscopy and energy-dispersive X-ray spectroscopy to examine the corrosion products and chemical composition of the corroded surfaces. The XPS measurements were used to better understand corrosion behavior of the alloy after immersion during the open-circuit conditions. The corrosion surface products were identified to be CaO, MgO, Mg(OH) 2 and CaCO 3 components. The ZnO and CuO compounds were formed on the surface of glassy samples.

In this work, the compositions of Al-Ni-Fe alloys were determined based on thermodynamic parameters optimization. Decagonal quasicrystalline phase D -Al70.83Fe9.83Ni19.34 was identified in the alloy with the highest Gibbs free energy of solid solution formation, i.e., Al71Ni24Fe5. According to this, the configurational entropy and enthalpy of solid solution formation must reach equilibrium to form quasicrystals in Al-Ni-Fe alloys. Differential thermal analysis and X-ray diffraction were used to describe the crystallization mechanism as a function of Fe concentration. 57Fe Mossbauer spectroscopy was used to describe the Fe local environment in crystalline alloys and quasicrystals. Moreover, the influence of quasicrystalline phases on improving the corrosion resistance was investigated. Quasicrystalline Al71Ni24Fe5 alloy had a six-times lower corrosion rate than its crystalline counterparts. Although this alloy showed the best corrosion resistance, all high-pressure cast Al-Fe-Ni alloys displayed improved corrosion resistance.

In this work, bulk metallic glasses Ca60Mg20Zn20 (BMGs) in the form of plates were successfully prepared by the high-pressure die casting. The glassy alloy with the biocompatible elements Ca, Mg and Zn was produced as bioresorbable material for potential biomedical applications. The structure of bulk amorphous samples was confirmed by a conventional X-ray diffraction and a differential scanning calorimetry (DSC) method. The corrosion behavior of the glassy samples was studied by electrochemical measurements and immersion tests in a physiological and Ringer's solution. The results of immersion show that the volume of H2 evolved after 480 min in Ringer's solution (24.9 ml/cm2) is higher in comparison with the measurements conducted in a physiological fluid (13.1 ml/cm2). The open-circuit potential (EOCP) for the Ca60Mg20Zn20 glassy sample after 60 min of incubation in Ringer's solution and a physiological fluid was found to be − 1543 and − 1566 mV vs. a saturated calomel electrode (SCE). The electrochemical measurements indicated a shift of the corrosion potential (Ecorr) from − 1551 mV for sample tested in a physiological fluid to − 1527 mV for specimen immersed in Ringer's solution. In order to further understand the corrosion behavior of the studied material the X-ray photoelectron spectroscopy (XPS) measurements were used to determine the elemental composition of the corrosion products after polarization. The corrosion products were identified to be CaCO3, Mg(OH)2, CaO, MgO and ZnO. The uniform corrosion mechanism is considered. The energy-dispersive X-ray spectroscopy (EDS) results suggest that calcium and magnesium hydroxides and calcium oxides were mainly formed on the surface of studied alloy. The post-experiment analyses of surface morphology were conducted by a scanning electron microscopy.

In this work, bulk metallic glasses Mg 60 Cu 30 Y 10, Mg 65 Cu 20 Y 10 Zn 5 and Mg 65 Cu 20 Y 10 Ni 5 (BMGs) in the form of plates with thickness of 1 mm were successfully synthesized by the high-pressure casting. The microstructure of bulk glassy alloys was examined by high-energy synchrotron X-ray diffraction, scanning and high-resolution electron microscopy. The immersion and electrochemical polarization measurements in 5% NaCl solution revealed that the Mg-based metallic glasses manifested higher polarisation resistance than conventional crystalline Mg sample. The electrochemical results show that the single phase structure of metallic glasses has an important role for the corrosion behavior. Moreover, the addition of alloying elements (e.g. Cu, Ni) can change a corrosion potential into an anode direction. In order to further understand the corrosion behavior of the studied alloys, the XPS measurements were used to determine the elemental composition of corrosion products after polarization. The corrosion surface films were identified to be Mg(OH) 2 and MgO. The corrosion mechanism was also considered and described by observing a morphology of the corroded samples versus immersion time. The EDS, XPS and XRD results suggest that magnesium hydroxides/oxides and other oxides were mainly formed as corrosion products on the surface of studied alloy.

Selected soft magnetic amorphous alloys Fe 80 B 20 , Fe 70 Nb 10 B 20 and Fe 62 Nb 8 B 30 were produced by the melt-spinning and characterized by X-ray diffraction (XRD), transmission Mossbauer spectroscopy (MS), Reverse Monte Carlo modeling (RMC) and relative magnetic permeability measurements. The Mossbauer spectroscopy allowed to study the local environments of the Fe-centered atoms in the amorphous structure of binary and ternary glassy alloys. The MS provided also information about the changes in the amorphous structure due to the modification of chemical composition by various boron and niobium content. The RMC simulation based on the structure factors determined by synchrotron XRD measurements was also used in modeling of the atomic arrangements and short-range order in Fe-based model alloys. Addition of boron and niobium in the ternary model alloys affected the disorder in as-cast state and also influenced on the number of nearest neighbor Fe–Fe atoms, consequently. The distributions of Fe- and B-centered coordination numbers showed that N =10, 9 and 8 are dominated around Fe atoms and N =9, 8 and 7 had the largest population around B atoms in the examined amorphous alloys. Moreover, the relationship between the content of the alloying elements, the local atomic ordering and the magnetic permeability (magnetic after-effects) was mentioned.

The atomic structure of Fe 42 Co 20 Nb 8 B 30 glassy alloy was investigated using synchrotron high-energy X-ray diffraction (XRD), Mossbauer spectroscopy (MS) and Reverse Monte Carlo modeling (RMC). The RMC method basing on the results of XRD measurements was used for evaluating interatomic distances and coordination numbers in the local structure of quaternary alloy. The coordination numbers for Fe–Fe atomic pairs were additionally determined using Mossbauer spectroscopy investigations and Gonser et al. approach. The measured Mossbauer spectra of glassy alloy were decomposed into subspectra representing average Fe–Fe coordination numbers. A layer with thickness of 0.5 nm was extracted from the RMC configuration box containing 8000 atoms and short-range ordering in the investigated glassy alloy was analyzed within this fragment. Coordination polyhedra for Fe–Fe, Co–Fe, B–Fe and Nb–Fe atomic pairs are represented by the Bernal's tetrahedra and octahedral as well by the monocapped square antiprism with one atom missing and B-centered clusters related to the tricapped trigonal prisms. The presence of clusters with five-fold coordination for the Fe–Fe pairs is confirmed by analysis of the Mossbauer spectra using the Gonser approach.

Stabilization and modification of magnetite nanoparticles synthesized by the co-precipitation method were presented in these studies. The role of chemical treatment on the structure and properties of Fe3O4 nanoparticles was described. It was noted, that the functionalization of nanoparticles surface by malonic acid has a negative impact on the catalytic activity in Fenton and photo-Fenton processes. The decolorization rate decreases from 86% to 35% and from 93% to 85.5 % at the same reaction time for these processes, respectively. However, the magnetite nanoparticles stabilized by malonic acid have higher saturation magnetization and electrical conductivity. These changes were related to the removal of the oxidized surface layer and to the stabilization of iron ions by malonic acid molecules, which was confirmed by the analysis of Mossbauer spectra. The proposed modification also allowed to reduce the size of the agglomerated nanoparticles 10 times and to produce stable Fe3O4 NPs.

AlCoCrFeNiSi high entropy alloys (HEAs) with variable chromium and silicon content (AlCoCrFeNiSi, AlCoFeNiSi, AlCoCr0.5FeNiSi0.5, AlCoFeNiSi0.5) were prepared by two different methods to determine the influence of cooling rate on the structure and properties of the alloys. The structure of the alloys was investigated using X-ray diffraction method and scanning electron microscopy. The possible formation of a single bcc/B2 phase was confirmed. The addition of chromium and silicon causes significant changes in the structure of the alloys, with new crystallographic phases being formed. The formation of Cr3Si intermetallic phases and segregation of iron was observed for the studied alloys. The magnetic properties were examined using a vibrating sample magnetometer and Mossbauer spectroscopy. The highest saturation magnetization was stated for alloys with a bcc/B2 one phase structure. The Mossbauer spectra confirmed, that ferromagnetic and paramagnetic phases occur in all studied alloys. The highest contribution from ferromagnetic phases was observed for the AlCoFeNiSi0.5 and AlCoCr0.5FeNiSi0.5 HEAs. Additionally, the corrosion resistance of the alloys was investigated in 3.5% NaCl solution. It was noted, that the AlCoCrFeNiSi, in a form of plates, is characterized by the highest corrosion resistance.

In this paper the influence of copper addition on the formation of the amorphous phase and the nanocrystallization process of Fe79.8−xCo2CuxMo0.2Si4B14 (x = 0, 0.25, 0.5, 0.75, 1, 1.5, 2) ribbons was described. The formation of crystalline phases was described using differential scanning calorimetry, X-ray diffractometry, Mossbauer spectroscopy and transmission electron microscopy. It was confirmed that the addition of copper decreases the glass forming ability, while facilitating the process of nanocrystallization. The analysis of the Avrami exponent allowed to state, that for fully amorphous alloys the crystallization of the α-Fe phase is associated with diffusion-controlled growth with decreasing nucleation rate and the Fe2B phase with interface controlled growth with increasing nucleation rate. Additionally, with increasing copper addition onset temperature of crystallization of α-Fe phase shifts to lower values, whereas for second, Fe2B phase, these changes are not so visible. Optimization of the annealing process of toroidal cores made from amorphous ribbons with different copper content allowed to obtain nanocrystalline, soft magnetic materials characterized by low coercivity ~9 A/m and high saturation induction of about 1.6 T. Analysis of transmission electron microscope images and electron diffraction confirmed that high magnetic parameters are related to the coexistence of the amorphous and nanocrystalline phases, which was confirmed also by Mossbauer spectroscopy.

The atomic structure of Fe70Nb10B20 alloy in “as-cast” state and after annealing was investigated using high-energy X-ray diffraction (XRD), Mossbauer spectroscopy (MS) and high resolution transmission electron microscopy (HRTEM). The HRTEM observations allowed to indicate some medium-range order (MRO) regions about 2 nm in size and formation of some kinds of short-range order (SRO) structures represented by atomic clusters with diameter ca. 0.5 nm. The Reverse Monte Carlo (RMC) method basing on the results of XRD measurements was used in modeling the atomic structure of Fe-based alloy. The structural model was described by peak values of partial pair correlation functions and coordination numbers determined by Mossbauer spectroscopy investigations. The three-dimensional configuration box of atoms was obtained from the RMC simulation and the representative Fe-centered clusters were taken from the calculated structure. According to the Gonser et al. approach, the measured spectra of alloy studied were decomposed into 5 subspectra representing average Fe–Fe coordination numbers. Basing on the results of disaccommodation of magnetic permeability, which is sensitive to the short order of the random packing of atoms, it was stated that an occurrence of free volume is not detected after nanocrystallization process.

Objective The paper intends to present structural and magnetic behavior of ferromagnetic composites consisted of nanocrystalline powders obtained by annealing and milling of Fe78Si9B13 and Fe73,5Cu1Nb3Si13,5B9 metallic glasses. Methods The as-cast ribbons were subsequently milled using a high-energy ball mill. The prepared powders were separated into fractions with a particle mean diameter range of 200–500 µm, 75–200 µm and 25–75 µm and then annealed to obtain the nanocrystalline powder materials. The powder particles were mixed and consolidated with a polymer to obtain composites in the form of the toroidal cores. The following experimental techniques were used: scanning and transmission electron microscopy, X-ray diffraction and vibration sample magnetometry. Results The analysis of magnetic properties of the powders and the composites prepared from the powders revealed that the preparation process caused significant decrease in magnetic properties in a relation to ribbons in as-cast state. Conclusion The structure and magnetic properties of the examined materials could be improved by means of a right choice of milling time as well as a thermal treatment and by a decrease of the demagnetization effect. Practice implications The amorphous and nanocrystalline powders obtained by a milling of metallic glasses are an alternative to solid alloys and make it possible to obtain the ferromagnetic nanocomposites with controlled magnetic properties.

New magnesium-based bulk metallic glasses Mg60Cu30Y10 have been prepared by pressure casting. Glassy alloys were successfully annealed to become nanocomposite containing 200 nm crystallites in an amorphous matrix. The microstructure of bulk glassy alloy and nanocomposite obtained during heat treatment was examined by X-ray diffraction and scanning and high-resolution electron microscopy. Metallic glass has been also studied to explain the structural characteristics by the reverse Monte Carlo (RMC) modeling based on the diffraction data. The HRTEM images allow to indicate some medium-range order (MRO) regions about 2–3 nm in size and formation of local atomic clusters. The RMC modeling results confirmed some kinds of short range order (SRO) structures. It was found that the structure of bulk metallic glass formed by the pressure casting is homogeneous. The composite material contained very small particles in the amorphous matrix. Homogeneous glassy alloy had better corrosion resistance than a composite containing nanocrystalline particles in a glassy matrix.

A new class of CaZn-based bulk glassy alloys with minor addition of boron and enhanced corrosion resistance for use in bioresorbable materials is introduced. The CaMgZnYbB alloys represent a new family of biomaterials with potential applications in orthopedic implants with controlled degradation rates and corrosion in the human body. The effect of substituting Yb for B in the structure on the corrosion and mechanical properties of quinternary Ca32Mg12Zn38Yb18-xBx (x = 1,2,3 at.%) alloys was investigated using X-ray diffraction, high-resolution transmission electron microscopy, differential scanning calorimetry, immersion and electrochemical polarization, compressive tests, and hardness measurements. The corrosion behavior was also evaluated using electrochemical impedance spectroscopy and X-ray photoelectron spectroscopy. Microstructural investigations showed that the Ca32Mg12Zn38Yb16B2 alloy was mainly amorphous, while small reflections from nanocrystals were observed in Ca32Mg12Zn38Yb17B1 and Ca32Mg12Zn38Yb15B3. Electrochemical polarization and immersion tests in Ringer's solution at 37 °C revealed that the CaMgZnYbB alloys had significantly higher corrosion resistance than CaMgZn alloys. Electrochemical impedance spectroscopy of alloys showed only single capacitive loops. The corrosion products were identified as CaO, MgO, Mg(OH)2, and CaCO3. The compressive strengths of the alloys from 220 MPa to 283 MPa were suitable for implant applications.

The local atomic structure of the Fe 80 B 20 , Fe 70 Nb 10 B 20 and Fe 62 Nb 8 B 30 glasses prepared in the form of ribbons has been studied by wide-angle X-ray scattering. Structural information about the amorphous ribbons has been derived from analysis of the radial distribution functions using the least-squares curve-fitting method. The obtained structural parameters indicate that Fe–Fe, Fe–B, Fe–Nb and Nb–B contributions are involved in the near-neighbor coordination spheres. The possible similarities of the local atomic arrangement in the investigated glasses and the crystalline Fe 3 B, Fe 23 B 6 and bcc Fe structures are also discussed.

Recently bulk amorphous alloys have attracted great attention due to their excellent magnetic properties. The glass-forming ability of bulk amorphous alloys depends on the temperature difference (Δ T x ) between glass transition temperature ( T g ) and crystallization temperature ( T x ). The increase of Δ T x causes a decrease of the critical cooling rate ( V c ) and growth of the maximum casting thickness of bulk amorphous alloys. The aim of the present paper is to characterize the structure, the thermal stability and magnetic properties of Fe 36 Co 36 B 19 Si 5 Nb 4 bulk amorphous alloys using XRD, Mossbauer spectroscopy, DSC and VSM methods. Additionally the magnetic permeability μ i (at force H ≈ 0.5 A/m and frequency f ≈ 1 kHz) and the intensity of disaccommodation of magnetic permeability Δ μ / μ ( t 1 ) (Δ μ = μ ( t 1 = 30 s) − μ ( t 2 = 1800 s)), have been measured, where μ is the initial magnetic permeability measured at time t after demagnetisation, the Curie temperature T C and coercive force H c of rods are also determined with the use of a magnetic balance and coercivemeter, respectively. Fe–Co–B–Si–Nb bulk amorphous alloys were produced by pressure die casting with the maximum diameters of 1 mm, 2 mm and 3 mm. The glass transition temperature ( T g ) of studied amorphous alloys increases from 807 K for a rod with a diameter of 1 mm to 811 K concerning a sample with a diameter of 3 mm. The crystallization temperature ( T x ) has the value of 838 K and 839 K for rods with the diameters of 1 mm and 3 mm, respectively. The supercooled liquid region (Δ T x = T x − T g ) has the value of about 30 K. These values are presumed to be the origin for the achievement of a good glass-forming ability of the Fe–Co–B–Si–Nb bulk amorphous alloy. The investigated amorphous alloys in the form of rods have good soft magnetic properties (e.g. M s = 1.18–1.24 T). The changes of crystallization temperatures and magnetic properties as a function of the diameter of the rods (time of solidification) have been stated.