Iron(III) salts with saturated monocarboxylic acids: formic, acetic, butyric, valeric, and enanthic acids are synthesized. The compounds obtained are characterized by elemental analysis, infrared (IR) spectroscopy, and differential scanning calorimetry. As a result of thermal decomposition of the synthesized carboxylates, iron-containing nanocomposites are obtained, which are studied by scanning and transmission electron microscopy, elemental analysis, infrared (IR) spectroscopy, energy-dispersive X-ray and Mössbauer spectroscopy, and X-ray phase analysis. The magnetic properties of the obtained nanocomposites are studied.

Known preparation methods of the magnetic sorbents based on exfoliated graphite (EG) with metallic phase take several hours and requires the use of a large amount of reducing gas at a high temperature, which is not technologically advanced. The aim of the work is to obtain EG modified with iron, cobalt, and nickel using new simple method. This method includes the thermal treatment in nitrogen atmosphere of the mixture of expandable graphite, Mn+ nitrates (Mn+ = Fe3+, Co2+, Ni2+) and melamine. The thermal decomposition of melamine leads to formation of ammonia, which reduces the products of the Mn+ nitrates decomposition (α-Fe2O3, Co3O4/CoO, NiO) to metallic iron, cobalt and nickel. The use of different amount of melamine as reducing agent leads to the formation of mixtures with different compositions containing iron oxides Fe3O4, FeO, metallic iron α-Fe, Fe-C alloy γ-(Fe,C) and iron carbide Fe3C, which were confirmed by Mossbauer spectroscopy. Metallic Co and Ni on the EG surface is formed in nitrogen atmosphere by reduction with carbon even without melamine. Obtained EG/Fe has the highest saturation magnetization of 54.7emu/g. EG/Co and EG/Ni have lower saturation magnetization of 40.1 and 12.0emu/g, which is due to lower saturation magnetization of the individual metals.

Exfoliated graphite (EG) is a promising sorbent for oil and organic pollutants, which has a high sorption capacity and hydrophobicity. Modifying the EG with ferrimagnetic compound allows EG with sorbed oil to be collected from the water surface with the use of a magnetic field. The aim of this work is to obtain a sorbent based on exfoliated graphite with ferrimagnetic maghemite (gamma-Fe2O3) and investigate its structure and functional properties. The preparation of iron-containing EG includes the impregnation of expandable graphite with a FeCl3 water solution and the thermal treatment of impregnated expandable graphite at temperatures between 400 and 1000 degrees C. Mossbauer spectroscopy, X-ray diffraction analysis, scanning electron microscopy and energy dispersive X-ray spectroscopy show the evolution of the iron-containing phase from FeOCl to the mixture of alpha-Fe2O3 and gamma-Fe2O3, which grants magnetic properties to the samples. EG obtained at 1000 degrees C has a saturation magnetization of 22.7 emu g(-1). High macropore and meso-/micropore volume investigated by mercury porosimetry and nitrogen adsorption-desorption method results in a high sorption rate and sorption capacity of EG up to 30 g g(-1) toward oil and liquid hydrocarbons. At the same time, the EG sorption capacity toward water is ten times lower.(c) 2023 Elsevier B.V. All rights reserved.

The spreading of microbial pathogens with more and more resistance to traditional low-molecular antibiotic agents demands new approaches to antibacterial therapy. The employment of bacteriophage enzymes capable of breaking bacterial cell walls has attracted much interest within this context. The specific features of the morphology of Gram-negative bacteria prevent the effective direct usage of lytic enzymes and require assistance from additional helpers to facilitate cell lysis. The current work is devoted to the study of boosting the lysis of Escherichia coli (E. coli) JM 109 and MH 1 strains induced by Lys394 bacteriophage endolysin by means of rod-like (56 × 13 nm) magnetic nanoparticles (MNPs) activated by a non-heating low-frequency magnetic field (LF MF) with a frequency of 50 Hz and a flux density of 68.5 mT in a pulse–pause mode (1 s on and 0.3 s off). According to theoretical assumptions, the mechanism of MNP assistance is presumably based upon the disordering of the outer membrane that facilitates enzyme permeation into peptidoglycans to its substrate. It is found that the effect of the LF MF reaches an almost a twofold acceleration of the enzyme reaction, resulting in almost 80 and 70%, respectively, of lysed E. coli JM 109 and MH 1 cells in 21 min. An increase in the membrane permeability was proven by two independent experiments employing β-lactamase periplasmic enzyme leakage and Nile Red (NR) hydrophobic dye fluorescence. It is shown that the outer membrane disordering of E. coli caused by exposure to LF MF nanoparticle movement leads to almost complete (more than 80%) β-lactamase release out of the cells’ periplasm to the buffer suspension. Experiments with NR (displaying fluorescence in a non-polar medium only) reveal a drastic reduction in NR fluorescence intensity, reaching a change of an order of magnitude when exposed to LF MF. The data obtained provide evidence of changes in the bacterial cell wall structure. The result shown open up the prospects of non-heating LF MF application in enhancing enzyme activity against Gram-negative pathogens.

An Erratum to this paper has been published: https://doi.org/10.1134/S1063783421130011

n Erratum to this paper has been published: https://doi.org/10.1134/S1063783421130011

The cation distribution and magnetic properties of polycrystalline ВаFe12–xSnxO19 (х = 0.0, 0.1, 0.3, 0.6, 0.9 and 1.2) ferrites have been studied for the first time by Fe57 and Sn119 Mössbauer spectroscopy. It was shown that doping of BaFe12O19 with tin is performed with limited heterovalent isomorphism according to the scheme 2Fe3+Sn4+ + Fe2+. It was found that intense heterovalent isomorphic substitutions occur in the 12k site of the BaFe12-xSnxO19 hexaferrite in the range of 0.1 < x < 0.6; less significant substitutions observed in the 4f2 and 2a sites. It was established that the heterovalent isomorphic substitution of tin for iron in BaFe12- xSnxO19 is limited by the values of x in range х = 0.6–0.9 Measurements of the magnetic parameters of the obtained samples were performed. The possibility of practical application of the synthesized ferrites is discussed.

Reactive sputtering of permalloy typically reduces crystallite size in films, if the concentration of reactive gas is low. This advances magnetic properties: decreases coercivity and increases good in-plane magnetic anisotropy. But oxygen is rarely applied for this purpose. Here, peculiar deposition conditions, including the geometry of the vacuum deposition system and large polymer substrate, allowed for the deposition of supermalloy with unusually high admixture of oxygen. Evolution of both static and dynamic magnetic properties with an increase in oxygen concentration proved to be dealt with the balance between grain size, surface structure, disordering of atomic structure and internal stresses. The critical concentration when supermalloy shows indications of oxidation is 5% of O2. Coercivity, resistivity, roughness and ferromagnetic resonance frequency are the parameters that are most sensitive to oxidation.

An Erratum to this paper has been published: https://doi.org/10.1134/S1063783421130011

The cation distribution and magnetic properties in polycrystalline ferrites of BaFe 12 – x Sn x O 19 ( x = 0, 0.1, 0.3, 0.6, 0.9, and 1.2) are first studied using Mössbauer spectroscopy of Fe 57 and Sn 119 . It is shown that doping of BaFe 12 O 19 with tin is performed with restricted heterovalent isomorphism according to the 2Fe 3+ → Sn 4+ + Fe 2+ reaction. It is found that intense heterovalent isomorphic substitutions in the 12 k position of the BaFe 12 – x Sn x O 19 hexaferrite are in the range of 0.1 < x < 0.6; and less significant substitutions are in the 4 f 2 and 2 a positions. It is found that the limit of heterovalent isomorphic substitution of iron with tin in BaFe 12 – x Sn x O 19 is in the range of x = 0.6–0.9. The magnetic parameters of the samples are measured. The possibility of practical application of the synthesized ferrites is discussed.

The series M0.5(1+x)FexZr2−x(PO4)3 (M—Ni, Cu, Mn) with Sc2(WO4)3-related structure (SW) were prepared using Pechini technique and characterized by powder X-ray diffraction analysis, SEM, EDX, IR, and Mössbauer spectroscopy. The concentration and temperature limits of solid solution formation were determined, lattice parameters were calculated, and their dependencies on the phosphate’s composition were studied. The crystal structure of the phosphate Mn0.65Fe0.3Zr1.7(PO4)3 (x = 0.3) was refined by the Rietveld method basing on the powder X-ray diffraction data. The compound crystallizes in monoclinic symmetry (space group P21/n) with lattice parameters: a = 8.7941(12), b = 8.9379(16), c = 12.4353(21) Å, β = 90.126(24)°, V = 977.49(27) Å3. Thermal expansion coefficients of the ceramics Cu0.5(1+x)FexZr2−x(PO4)3 were determined. The volume expansion coefficients of the compounds vary in the range (4.4–10.8)∙10−5 K −1.

Spray pyrolysis of an aqueous solution of iron nitrate, proceeded with reduction of the product in hydrogen, gave iron powder with micron-sized hollow particles. Coating these iron particles with SiO2 through tetraethyl orthosilicate hydrolysis prevented interparticle electrical contacts and suppressed DC percolation. This material shows a high ferromagnetic resonance frequency of 18 GHz, low permittivity, and weighs 20% less than common carbonyl iron. Potential microwave applications are for inductors and electromagnetic interference shielding designs.

Получен магнитный сорбент на основе терморасширенного графита, модифицированного ферритом магния, путем пропитки окисленного графита в смешанном растворе FeCl3 и Mg(NO3)2 с последующей термообработкой пропитанного окисленного графита на воздухе. Методами рентгенофазового анализа и мессбауэровской спектроскопии показано, что структура феррита магния представляет собой обращенную шпинель со степенью инверсии 0.59. Намагниченность насыщения полученного терморасширенного графита, содержащего феррит магния, составляла 16.1 эме/г, в то время как его сорбционная емкость по отношению к нефти достигала 54 г/г. При прессовании терморасширенного графита до плотности 0.03 г/см3 его сорбционная емкость уменьшалась до 26 г/г, дальнейшее увеличение плотности приводило к значительному снижению сорбционной способности образца.

A magnetic sorbent based on exfoliated graphite modified with magnesium ferrite has been prepared by impregnating oxidized graphite in a mixed solution of FeCl3 and Mg(NO3)2, followed by heat treatment of the impregnated oxidized graphite in air. X-ray diffraction and Mössbauer spectroscopy results demonstrate that the structure of the magnesium ferrite is an inverse spinel with a degree of inversion of 0.59. The saturation magnetization of the magnesium ferrite-containing exfoliated graphite is 16.1 emu/g, whereas its oil sorption capacity is as high as 54 g/g. Compaction of the exfoliated graphite to a density of 0.03 g/cm3 reduced its sorption capacity to 26 g/g. Further increasing the density of the material led to a considerable decrease in its sorption capacity.

Due to the macropore structure and the hydrophobic properties, exfoliated graphite (EG) is considered as a perspective sorbent for oil and liquid hydrocarbons from the water surface. However, there is the problem of EG collection from the water surface. One of the solutions is the modification of EG by a magnetic compound and the collection of EG with sorbed oil using the magnetic field. In this work, the method of the two-stage preparation of exfoliated graphite with ferrite phases is proposed. This method includes the impregnation of expandable graphite in the mixed solution of iron (III) chloride and cobalt (II) or nickel (II) nitrate in the first stage and the thermal exfoliation of impregnated expandable graphite with the formation of exfoliated graphite containing cobalt and nickel ferrites in the second stage. Such two-stage method makes it possible to obtain the sorbent based on EG modified by ferrimagnetic phases with high sorption capacity toward oil (up to 45-51 g/g) and high saturation magnetization (up to 42 emu/g). On the other hand, this method allows to produce the magnetic sorbent in a short period of time (up to 10 s) during which the thermal exfoliation is carried out in the air atmosphere.

New La/Zn substituted strontium ferrites Sr(2 −x)La x [Fe(2 − x)Zn x ]O5, (0 ≤ x ≤ 0.3) with brownmillerite- type structure are obtained and studied via X-ray phase analysis and Mössbauer spectroscopy. Depending on the conditions of synthesis, substituting Zn2+ cations can either mainly occupy tetrahedral positions in a brownmillerite structure, or be uniformly distributed between the tetrahedral and octahedral positions. It is shown that they are reversibly oxidized by atmospheric oxygen at elevated temperatures.

Iron powder particles were coated with a thin SiO2 shell for protection of corrosion. Dynamic magnetic behavior of the as-synthesized material was studied in comparison with uncoated metal in terms of frequency dispersion of the microwave permeability and permittivity. A uniform 100-nm SiO2 shell provides durable corrosion resistance to a 4.5-μm carbonyl iron powder. The shell was deposited through tetraethyl orthosilicate hydrolysis of technical grade chemicals. It was shown that the shell did not influence the magnetic properties of the iron powder. Electron microscopy, particle size analysis, and γ-resonance spectroscopy were applied in the study. The deposited SiO2 decreased the microwave permeability value and prevented percolation conductivity in a composite with a paraffin wax dielectric matrix.

Structural characteristics and magnetic properties' of ZnxFe3-xO4 (where x = 0; 0.09; 0.18; 0.45; 1) nanoparticles were studied with X-ray diffraction (XRD), transmission electron microscopy (TEM), infrared spectroscopy (IR) and vibrating sample magnetometry (VSM). Oxidation of Fe2+ ions, redistribution of Zn2+ and Fe3+ ions between octahedral and tetrahedral sites, and the formation of cation vacancies in spinel-type cubic structure of the obtained ZnxFe3-x-y square O-y(4) substitutional solid solutions were revealed by Fe-57 Mossbauer spectroscopy. The nano particles synthesized via a modified sol-gel method using inorganic precursors have a size of 4-10 nrn, single-phase composition, superparamagnetic behavior at room temperature (300 K) and a relatively hydrophilic surface to form stable aqueous suspensions. The maximum magnetization of 59 emu/gat 300 K corresponds to Zn0.18Fe2.82O4 composition. The listed features make the materials promising candidates for various biological and medical applications such as contrast-enhanced magnetic resonance imaging, hyperthermia of pathological tissues, controlled drug release, and separation of nucleic acids.