The various ionizing radiations (electrons, protons, heavy charged particles, X-ray and gamma radiation) are the damaging factors for microelectronic products. The common used material for radiation ...protection is lead. Recently, Bi deposition has become an interest for the electrochemical community because of bismuth's unique electrical, physical and chemical properties. There is a limited number of authors dealing with Bi films onto metallic substrates by electrochemical deposition. The electrochemical deposition conditions and Bi coatings structure were examined. X-ray diffraction patterns for all samples were indexed to rhombohedral Bi. Coatings with a signified texture (012) are formed in electrolyte without additives. With gelatin adding the growth texture changes and the most intense reflex becomes (110). It was found that gelatin concentration increasing from 0.1 to 0.5 g/L leads Bi microstructural refinement from 4-20 μm to 50 nm-2 μm, respectively. The protection efficiency of shields based on Bi under 1,6–1,8 MeV electron radiation energy was measured. The electron beam attenuation efficiency was estimated by the changing of current-voltage characteristics of semiconductor test structures which were located behind the shields and without them. It has been determined that optimal protection effectiveness and mass-dimensional parameters have Bi shields with 2 g/cm2 reduced thickness and 156 attenuation coefficient.
•Examined the conditions of electrochemical Bi deposition and the structure of Bi coatings.•Established critical influence of gelatin adding in electrolyte on Bi structure.•Measured the protection efficiency of shields based on Bi under 1,6–1,8 MeV electron irradiation.
•The range of solid solutions of Ti-doped Ba-hexaferrites was expanded to 2.00.•Ti-doped Ba-hexaferrites BaFe12−xTixO19 magnetic state interpretation was given.•Mechanism of occupation nonequivalent ...crystallographic positions by Ti was determined.•The spin-glass component of the magnetic phase state is fixed.•The critical magnetic field of the spin-glass component disappearance was found.
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A number of solid solutions based on BaFe12−xTixO19 M-type barium hexaferrite doped with titanium cations up to x = 2.00 were obtained using conventional ceramic technology. The phase composition, crystal structure and unit cell parameters were refined by the Rietveld method using powder X-ray diffraction data up to T = 900 K. It was found that all the compositions have a magnetoplumbite structure satisfactorily described by P63/mmc space group (No. 194). With increasing temperature and doping concentration, the unit cell parameters increase almost monotonically. The minimum volume of V ~ 696.72 Å3 was determined for the composition with x = 1.00 at T = 100 K, while the maximum value of V ~ 714.00 Å3 is observed for the composition with x = 2.00 at T = 900 K. The mechanism of occupation nonequivalent crystallographic positions with titanium cations is established. The spin-glass component of the magnetic phase state is fixed. The Tdif temperature of the difference between the ZFC-FC curves decreases with an increase in the concentration of titanium cations and the magnetic field from ~237.2 K to ~ 44.5 K, while the Tinf inflection temperature of the ZFC curve increases from ~21.0 K to ~23.8 K. With an increase in the doping concentration, both the Dav average and Dmax maximum clusters grow up to ~ 100 nm. As the magnetic field increases above the critical value, the spin-glass component disappears. For compositions with x > 1.00, the magnetization is not saturated in fields up to 6 T. Along with the formation of the spin-glass component, doping with titanium cations for barium hexaferrite lowers the TC Curie temperature down to T ~600 K. The Ms spontaneous and Mr remanent magnetizations, as well as the Bc coercivity, decrease with increasing doping concentration almost monotonically, while the latter has an inflection point at x = 1.00. The minimum values of spontaneous and remanent magnetization, as well as coercivity, are observed for the composition with x = 2.00 and amount to Ms ~17.7 emu/g, Mr ~1.9 emu/g, and Bc ~3.9 × 10−3 T, respectively. An interpretation of the magnetic state of the doped BaFe12−xTixO19 barium hexaferrite is given taking into account the mechanism of occupation nonequivalent crystallographic positions with titanium cations.
Magnetic nanoparticles based on Fe3O4 and their modifications of surface with therapeutic substances are of great interest, especially drug delivery for cancer therapy includes boron-neutron capture ...therapy. The results of boron-rich compound (carborane borate) attachment to previously aminated by (3-aminopropyl)-trimethoxysilane iron oxide nanoparticles are presented. Energy-dispersive X-ray analysis and Fourier transform infrared spectroscopy with attenuated total reflection (ATR) accessory confirmed change of nanoparticles elemental content after modification and formation of new bond between Fe3O4 and attached molecules. Scanning and transmission electron microscopy showed that Fe3O4 nanoparticles average size is 18.9 nm. Phase parameters were investigated by powder X-ray diffraction, Fe3O4 nanoparticles magnetic behavior was evaluated by Mössbauer spectroscopy. Chemical and colloidal stability was studied using simulated body fluid (phosphate buffer – PBS). Modified nanoparticles have excellent stability in PBS (pH = 7.4), characterized by X-ray diffraction, Mössbauer spectroscopy and dynamic light scattering. Fe3O4 biocompatibility was elucidated in-vitro using cultured mouse embryonic fibroblasts. The obtained results show the increasing of IC50 from 0.110 mg/ml for Fe3O4 to 0.405 mg/ml for Fe3O4-Carborane nanoparticles. Obtained data confirm biocompatibility and stability of synthesized nanoparticles and potential to use them in boron-neutron capture therapy.
•Fe3O4 nanoparticles (NPs) with 18.9 nm average size were synthesized and modified with APTMS.•NPs were characterized using FTIR, SEM, TEM, XRD, DLS, Mössbauer spectroscopy and VSM methods.•Modified NPs have excellent stability in simulated body fluid.•Carborane borate with 21 boron atoms was immobilized on NPs through the ionic interaction.•Synthesized modifed NPs are excellent candidates for using in boron-neutron capture therapy.
M-type hexagonal ferrites with heterovalent substitutions (Nd3+-Zn2+ and Ti4+) were synthesized. X-Ray diffraction (XRD) powder patterns of Sr(Nd,Zn)xFe12-xO19 and BaFe12-xTixO19 (0.1 ≤ x ≤ 1.0) ...confirmed the single phase constitution of all investigated samples. High frequency magnetic (permeability), electrical (permittivity), and resonant properties were analyzed. Unexpected behavior in the permittivity and permeability as a function of frequency was observed. Appearance of two peaks for samples with x = 0.1 and 0.9 indicated mixed oxidation state for the Fe ions. Behavior for Sr(Nd,Zn)xFe12-xO19 (0.3 ≤ x ≤ 0.7) confirms the occurrence of the anomalous quantum effect, namely charge disproportionation. The permeability behavior of Ti-substituted samples with a double Fe oxidation state was theoretically discussed in terms of spin states crossover. The behavior of reflection losses for Sr(Nd,Zn)xFe12-xO19 and BaFe12-xTixO19 (0.1 ≤ x ≤ 1.0) samples was discussed in terms of the modalities of charge ordering in heterovalent substituted M-type hexaferrites.
•Heterovalent substituted M-type hexaferrites were synthesized and investigated.•Double oxidation states for Fe ions were established.•Electrodynamics characteristics were explained based on quantum effects.
Present paper reports about the strong correlation of the heat treatment conditions (annealing), crystal structure parameters, microstructure and magnetic properties evolution in nanosized BaFe12O19 ...M-type hexaferrites or BaM nanohexaferrites. Samples of the BaM nanohexaferrites were obtained using sol-gel method with further annealing in the range 600–1100 °C. All investigated samples were single phase and described by the P63/mmc space group. Unusual and non-linear behavior of the lattice parameters with annealing temperature increasing from 600 to 1100 °C was explained by the competition of the increase in the average crystallite size (decrease in the surface tension effect) and increase in the level of their chemical homogeneity (anionic stoichiometry). Increase of the heat treatment temperature leads to increase of the microstructure parameters (average crystal size and specific surface area) and non-linear changes in magnetic properties. Correlation of the annealing temperature and magnetic properties was discussed in terms of the structural features.
•BaM nanohexaferrites were synthesized using sol-gel method with further annealing.•Strong correlation between average crystal size and annealing temperature was established.•Non-linear behavior of the structure and magnetic properties after annealing was observed.•All changes in BaM were discussed in terms of the morphology evolution.
Ni nanopillars (Ni NPs) composite material formation technology embedded in porous anodic alumina by electrochemical deposition is presented in this paper. The morphological and structural properties ...of the composite material were investigated using scanning electron microscopy, atomic force microscopy, X-ray diffraction. The corrosion resistance of the nanocomposite materials has been studied by potentiodynamic polarization curves analysis and polarization resistance method. The composite represents the array of vertically ordered Ni NPs with the identical size in alumina matrix. XRD investigation indicates that Ni NPs are polynanocrystalline material with 18 nm crystallite size. It has been shown that Ni NPs and the composite material have sufficient corrosion resistance in a 0.9% aqueous NaCl solution. Porous alumina is the neutral and protective component of the composite. These nanocomposite materials can be excellent candidates for practical use in electronics, sensorics, biomedicine.
•Unique technology of anodic alumina matrix formation has been developed.•Composite based on Ni nanopillars in anodic alumina matrix has been produced.•Method for corrosion resistance investigation for nanomaterials has been proposed.•First time corrosion resistance properties for Ni nanopillars have been performed.•Ni nanocomposites show unexpected corrosion resistance properties.
The Dy-substituted Co1/2Ni1/2(Fe2-xDyx)O4 (0.00 ≤ x ≤ 0.08) spinels were obtained in nanosized form. Correlation between chemical composition, crystal structure, magnetic properties and ...electrodynamics properties was investigated. The features of the fine crystal structure were investigated using neutron powder diffraction. Magnetic properties were studied utilizing vibration sample magnetometry in the wide temperature and magnetic field ranges. Electrodynamic properties were measured in high-frequency range of 2–18 GHz using vector network analyser. This data was used for reflection losses calculations. There was observed high resonant reflection in the range of 2–6 GHz due to electromagnetic radiation absorption. The weakening of the reflected radiation was explained by the domain boundary resonance. This explanation correlates well with the data of the microstructure analysis. The nature of absorption due to domain boundary resonance in low dimensional magnetic oxides was given. A strong correlation between the level of chemical substitution and amplitude-frequency characteristics for investigated Co1/2Ni1/2(Fe2-xDyx)O4 (0.00 ≤ x ≤ 0.08) spinels was detected.
•Nanosized Dy-substituted Ni–Co spinels were synthesized using sol-gel method.•Strong correlation between composition and microstructure was observed.•Behaviour of the magnetic properties was analysed in terms of the magnetic structure frustration.•Reflection losses correlates well with composition and crystal size distribution.•The weakening of the reflected radiation was explained by the DBR.
•BaFe12−xTixO19 (x ≤ 1) hexaferrites polycrystalline ceramics was investigated.•Substitution model by titanium cations was defined.•Mossbauer and Raman spectrometry was established.•The saturation ...magnetization decreasing with substitution level increasing was shown.•Dielectric constant and dielectric loss tangent values and temperature dependence were measured.
Titanium substituted BaFe12−xTixO19 (x ≤ 1) barium hexaferrites have been synthesized using the solid phase method. The phase purity and the crystal structure of the obtained solid solutions have been studied by X-ray diffraction. It was found that the unit cell parameters change a non-monotonically. The a parameter has a maximum of 5.896 Å at x = 0.25 and then it decreases almost linearly down to 5.886 Å at x = 1. The c parameter almost linearly increases from 23.216 Å up to 23.282 Å with x increasing. It has been discovered that titanium cations are located in the following positions: 4fIV tetrahedral and octahedral 4fVI and 12k ones. Results of the Mossbauer and Raman spectrometry confirm the established substitution mechanism. The homogeneous ferrimagnetic ordering is detected by magnetic measurements down to ~35 K. Below this temperature the noncollinear magnetic structure is formed as a result of Fe2+ cations change in the spin state from high to low configuration. Magnetization for all the samples is saturated at room temperature in fields of ~1 T. The saturation magnetization decreases from ~70.6 emu/g for x = 0.25 to ~56.7 emu/g for x = 1. The real part of the dielectric constant has value of ~0.2 for all the samples and gradually decreases at heating from room temperature up to ~500 K, after which it begins to increase sharply. The dielectric loss tangent has a maximum in the region of ~500 K and reaches a value of ~0.25 at a frequency of 104 Hz. With increasing the substitution level, the dielectric constant and the dielectric loss of all the samples increase.
Mn0.5Zn0.5(EuxNdxFe2-2x)O4 ferrite nanoparticles (FNP) were obtained by ultrasonic (USM) and sol-gel (SGM) methods. It was observed that SGM allows us to produce nanoparticles with the average ...crystal size of 10–40 nm and the specific surface area of 5–7.5 × 104 m2/g with a strong correlation between the chemical composition (x) and the crystal size distribution. At the same time using USM, we obtained nanoparticles with the average crystal size of 3–15 nm and the specific surface area of 1.5–1.7 × 105 m2/g without a strong correlation between Eu/Nd concentration and the crystal size distribution. The specific surface area and average crystal size are the main factors determining the antiproliferative activity of FNP. The anti-cancer activity of FNP was investigated both on cancerous cells, human adenocarcinoma cells and human colorectal carcinoma cells. It was established that samples obtained using USM were more effective in producing cytotoxic effects on cancer cells. Thus, we confirm a strong correlation between the main microstructure parameters for Mn0.5Zn0.5(EuxNdxFe2-2x)O4 ferrite nanoparticles.
•Structure vs. temperature for BaFe12−xInxO19 x = 0.1, 1.2 was investigated.•Atomic coordinates and lattice parameters were Rietveld refined.•Exchange interactions vs. structure were ...investigated.•Magnetic and dipole moments at different position per iron ion were defined.•Spontaneous polarization for these compositions was established at 300 K.
Crystal and magnetic structure of the doped BaFe12−xInxO19 samples were refined by the results of investigations using high resolution neutron powder diffraction and vibration sample magnetometry at different temperatures. The refinements were realized in frame of two space groups. The P63/mmc (No 194) centrosymmetric nonpolar and P63mc (No 186) noncentrosymmetric polar space groups were used. The unit cell parameters, ionic coordinates, thermal isotropic factors, occupation positions, bond lengths and bond angles, microstrain values were established. The magnetic and dipole moments were also defined. It is established that the In3+ cations may be located only in the Fe1 – 2a and Fe2 – 2b crystallographic positions with equal probability for the sample with lowest substitution level x = 0.1. At the x = 1.2 substitution level about half of the In3+ cations occupies the Fe5 – 12 k positions. For the last sample the remaining half of the In3+ cations is equiprobably located in the Fe1 – 2a and Fe2 – 2b positions. The spontaneous polarization was established for these compositions at 300 K. It is studied the influence of the type of substitutive cation and structural parameters on the Fe3+(i) – O2− – Fe3+(j) (i, j = 1, 2, 3, 4, 5) indirect superexchange interactions with temperature. With substitution level increase the superexchange interactions between the magnetic positions inside and outside the sublattices are broken which leads to a decrease in the value of their magnetic moments.
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