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A template method for synthesis of B-doped graphene-like carbon nanomaterial (B-graphene-like carbon) with high surface area has been developed. In this method, magnesium oxide is used as a template where a carbon layer doped with boron atoms is deposited. Magnesium oxide carbonization was performed in an autoclave at 600 °C and 5 atm pressure using phenylboronic acid (FBA) dissolved in an ethanol-acetone mixture. Then, magnesium oxide from the С—B/MgO composite was dissolved in hydrochloric acid. The obtained B- graphene-like carbon was studied by IR spectroscopy, electron microscopy, XPS methods and quantum chemical calculations. B-graphene-like carbon contains 3–6 carbon layers and 0.2 wt% B. Structure of carbon net with embedded boron fragment has been proposed as the result of performed studies. [ABSTRACT FROM AUTHOR]

Covalent triazine frameworks (CTF) have been recently applied as supports for metal catalysts for different reactions. Varying the nature of the CTF support could improve catalytic properties due to a change in the nature of metal active sites presented in the form of single atoms and dispersed nanoparticles. To understand these changes, for the first time, 1 wt % Pd catalysts supported on hatnCTF and acacCTF prepared from hexaazatrinaphthylene-tricarbonitrile and malonyldibenzonitrile, respectively, were tested in formic acid decomposition in the gas phase. The results were compared with those obtained for a Pd/g-C3N4 catalyst. The catalysts were characterized by high-angle annular dark-field/scanning transmission electron microscopy, X-ray absorption near edge structure/extended X-ray absorption fine structure and X-ray photoelectron spectroscopy. The activity of the Pd/hatnCTF catalyst was significantly higher than those for Pd/acacCTF and Pd/g-C3N4, providing the reaction at a lower temperature by ∼60 K. The high performance of this catalyst was attributed to single-atom Pd2+–C1N3 sites, which are the main active Pd species in this sample. The Pd/acacCTF sample contained single-atom Pd2+–O4 sites and metallic Pd nanoparticles, while the Pd/g-C3N4 sample contained mainly metallic Pd nanoparticles. The selectivity toward H2 was high (>98%) for all catalysts even at 573 K. The obtained results could be useful for the development of different applications of CTF materials. [ABSTRACT FROM AUTHOR]

The unique physical and chemical properties of composite materials based on carbon nanofibers (CNFs) makes them attractive to scientists and manufacturers. One promising method to produce CNFs is catalytic chemical vapor deposition (CCVD). In the present work, a method based on carbon erosion (CE) of bulk microdispersed Ni-Cu alloys has been proposed to prepare efficient catalysts for the synthesis of CNF-based composites. The initial Ni-Cu alloys were obtained by mechanochemical alloying (MCA) of metallic powders in a planetary mill. The effect of MCA duration on the phase composition of Ni-Cu samples was studied by X-ray diffraction analysis and temperature-programmed reduction in hydrogen. It has been also revealed that, during such stages as heating, reduction, and short-term exposure to the reaction mixture (C2H4/H2/Ar) at 550 °C, the formation of a Ni-based solid solution from the initial Ni-Cu alloys takes place. The early stages of the CE process were monitored by transmission electron microscopy combined with energy-dispersive X-Ray analysis. It was found that the composition of the catalytic particles is identical to that of the initial alloy. The morphological and structural features of the prepared Ni-Cu-CNF composites were studied by scanning and transmission electron microscopies. The textural characteristics of the composites were found to be dependent on the reaction time. [ABSTRACT FROM AUTHOR]

A novel ultra-high-entropy rare earth orthoferrite (UHE REO) of Sc1/16Y1/16La1/16Ce1/16Pr1/16Nd1/16Sm1/16Eu1/16Gd1/16Tb1/16Dy1/16Ho1/16Er1/16Tm1/16Yb1/16Lu1/16FeO3 nominal composition was successfully synthesized for the first time through a simple and efficient solution combustion approach. PXRD, Raman, and 57Fe Mössbauer spectroscopy confirmed the high chemical and phase purity of the synthesized UHE REO (hereafter denoted as ΣREFeO3), which belonged to the Pnma space group, typical of the perovskite-like rare earth orthoferrites. Despite the fact that the main X-ray reflections, vibration modes, and spectral Mössbauer components unambiguously indicate the single-phase nature of the sample, the results of SEM and TEM make it possible to establish the presence of a main (about 50 nm) and a minor ultrafine (about 10 nm) fraction of ΣREFeO3 nanoparticles. The bimodal size distribution of nanoparticles was also reflected in the magnetic behavior of this substance: the presence of several sextet components in the Mössbauer spectra, the hard single-domain magnetic nature of the main fraction of 50 nm UHE REO nanoparticles, and the superparamagnetic state of the minor fraction of 10 nm UHE REO nanoparticles. Thus, the unusual features of nanostructured ΣREFeO3 can potentially be used for the creation of new generations of transformers, magnetic memory systems, magnetic screens, radio devices, etc. [ABSTRACT FROM AUTHOR]

The effect of support on the performance of Pd1Ag10/Al2O3 and Pd1Ag10/CeO2–ZrO2 catalysts in the selective hydrogenation of diphenylacetylene (DPA) was studied. Characterization of the catalyst by DRIFTS-CO and HRTEM revealed the formation of a PdAg single-atom alloy (SAA) structure on the surface of PdAg nanoparticles, with Pd1 sites isolated by Ag atoms. It was found that the use of CeO2–ZrO2 as a carrier makes it possible to increase the activity of the Pd1Ag10 catalyst by a factor of three without loss of selectivity compared to the reference Pd1Ag10/Al2O3. According to the HRTEM data, this catalytic behavior can be explained by an increase in the dispersion of Pd1Ag10/CeO2–ZrO2 compared to its Pd1Ag10/Al2O3 counterpart. As evidenced by DRIFTS-CO data, the high selectivity of the Pd1Ag10/CeO2–ZrO2 sample presumably stems from the stability of the structure of isolated Pd1 sites on the surface of SAA Pd1Ag10/CeO2–ZrO2. [ABSTRACT FROM AUTHOR]

Photocatalysts based on g-C3N4 have been investigated in the CO2 reduction reaction under visible light irradiation (λ = 397, 427, 452 nm). Photocatalysts were prepared by melamine calcination at 500–600 °C with further platinum deposition (0.1–1.0 wt.%). The effect of the preparation conditions of g-C3N4 and the method of platinum deposition on the physicochemical properties and activity of photocatalysts was studied. The photocatalysts were investigated by X-ray photoelectron spectroscopy, X-ray absorption spectroscopy, X-ray diffraction, high resolution transmission electron microscopy, UV-Vis spectroscopy, and low temperature nitrogen adsorption techniques. It has been found that the efficiency of CO2 reduction is governed by the surface area of g-C3N4 and the presence of platinum in the metallic state, while the optimal content of platinum is 0.5 wt. %. The highest rate of CO2 reduction achieved over Pt/g-C3N4 photocatalyst is 13.2 µmol h−1 g−1 (397 nm), which exceeds the activity of pristine g-C3N4 by 7 times. The most active photocatalysts was prepared by calcining melamine in air at 600 °C, followed by modification with platinum (0.5 wt.%). [ABSTRACT FROM AUTHOR]

The catalytic utilization of chlorine-organic wastes remains of extreme importance from an ecological point of view. Depending on the molecular structure of the chlorine-substituted hydrocarbon (presence of unsaturated bonds, intermolecular chlorine-to-hydrogen ratio), the features of its catalytic decomposition can be significantly different. Often, 1,2-dichloroethane is used as a model substrate. In the present work, the catalytic decomposition of trichloroethylene (C2HCl3) over microdispersed 100Ni and 96Ni-4W with the formation of carbon nanofibers (CNF) was studied. Catalysts were obtained by a co-precipitation of complex salts followed by reductive thermolysis. The disintegration of the initial bulk alloy driven by its interaction with the reaction mixture C2HCl3/H2/Ar entails the formation of submicron active particles. It has been established that the optimal activity of the pristine Ni catalyst and the 96Ni-4W alloy is provided in temperature ranges of 500–650 °C and 475–725 °C, respectively. The maximum yield of CNF for 2 h of reaction was 63 g/gcat for 100Ni and 112 g/gcat for 96Ni-4W catalyst. Longevity tests showed that nickel undergoes fast deactivation (after 3 h), whereas the 96Ni-4W catalyst remains active for 7 h of interaction. The effects of the catalyst's composition and the reaction temperature upon the structural and morphological characteristics of synthesized carbon nanofibers were investigated by X-ray diffraction analysis, Raman spectroscopy, and electron microscopies. The initial stages of the carbon erosion process were precisely examined by transmission electron microscopy coupled with elemental mapping. The segmented structure of CNF was found to be prevailing in a range of 500–650 °C. The textural parameters of carbon product (SBET and Vpore) were shown to reach maximum values (374 m2/g and 0.71 cm3/g, respectively) at the reaction temperature of 550 °C. [ABSTRACT FROM AUTHOR]

Mixed Ni-Al oxide catalytic precursors with different elemental ratios (20, 50, and 80 wt.% Ni0) were synthesized using green supercritical antisolvent co-precipitation (SAS). The obtained oxide precursors and metal catalysts were characterized in detail by X-ray diffraction (XRD) analysis, atomic pair distribution function (PDF) analysis, CO adsorption, and high-resolution transmission electron microscopy (HRTEM). It was found that the composition and structure of the Ni-Al precursors are related to the Ni content. The mixed Ni1−xAlxO oxide with NiO-based crystal structure was formed in the Ni-enriched sample, whereas the highly dispersed NiAl2O4 spinel was observed in the Al-enriched sample. The obtained metal catalysts were tested in the process of anisole H2-free hydrogenation. 2-PrOH was used as a hydrogen donor. The catalyst with 50 wt.% Ni0 demonstrated the highest activity in the hydrogenation process. [ABSTRACT FROM AUTHOR]

Synthesis and characterization of spherulite-like nanocrystalline titania with rutile structure (r-TiO2) are described herein. The r-TiO2 particles were synthesized via the convenient and low-cost hydrothermal treatment of TiO(C6H6O7) titanyl citrate. The r-TiO2 spherulites are micron-sized agglomerates of rod-shaped nanocrystals with characteristic sizes of 7(±2) × 43(±10) nm, oriented along (101) crystallographic direction, and separated by micropores, as revealed by SEM and TEM. PXRD and Raman spectroscopy confirmed the nanocrystalline nature of r-TiO2 crystallites. BET analysis showed a high specific surface area of 102.6 m2/g and a pore volume of 6.22 mm3/g. Photocatalytic performances of the r-TiO2 spherulites were investigated for the processes of methyl violet (MV) degradation in water and hydrogen evolution reaction (HER) in aqueous solutions of ethanol. The (MV) degradation kinetics was found to be first-order and the degradation rate coefficient is 2.38 × 10−2 min−1. The HER was performed using pure r-TiO2 spherulites and nanocomposite r-TiO2 spherulites with platinum deposited on the surface (r-TiO2/Pt). It was discovered that the r-TiO2/Pt nanocomposite has a 15-fold higher hydrogen evolution rate than pure r-TiO2; their rates are 161 and 11 nmol/min, respectively. Thus, the facile synthesis route and the high photocatalytic performances of the obtained nanomaterials make them promising for commercial use in such photocatalytic processes as organic contamination degradation and hydrogen evolution. [ABSTRACT FROM AUTHOR]

Double oxides with the structure of the Ruddlesden–Popper (R-P) layered perovskite An+1BnO3n+1 attract attention as materials for various electrochemical devices, selective oxygen-permeable ceramic membranes, and catalytic oxidative reactions. In particular, Sr2TiO4 layered perovskite is considered a promising catalyst in the oxidative coupling of methane. Our high-resolution transmission electron microscopy (HRTEM) studies of Sr2TiO4 samples synthesized using various methods have shown that their structure often contains planar defects disturbing the periodicity of layer alternation. This is due to the crystal-chemical features of the R-P layered perovskite-like oxides whose structure is formed by n consecutive layers of perovskite (ABO3)n in alternating with layers of rock-salt type (AO) in various ways along the c crystallographic direction. Planar defects can arise due to a periodicity violation of the layers alternation that also leads to a violation of the synthesized phase stoichiometry. In the present work, a crystallochemical analysis of the possible structure of planar defects is carried out, structures containing defects are modeled, and the effect of such defects on the X-ray diffraction patterns of oxides of the A2BO4 type using Sr2TiO4 is established as an example. For the calculations, we used the method of constructing probabilistic models of one-dimensionally disordered structures. For the first time, the features of diffraction were established, and an approach was demonstrated for determining the concentration of layer alternation defects applicable to layered perovskite-like oxides of the A2BO4 type of any chemical composition. A relation has been established between the concentration of planar defects and the real chemical composition (nonstoichiometry) of the Sr2TiO4 phase. The presence of defects leads to the Ti enrichment of particle volume and, consequently, to the enrichment of the surface with Sr. The latter, in turn, according to the data of a number of authors, can serve as an explanation for the catalytic activity of Sr2TiO4 in the oxidative coupling of methane. [ABSTRACT FROM AUTHOR]

According to our knowledge, single-atom Pd catalysts supported on covalent triazine frameworks (CTF) have not been studied in the production of hydrogen from formic acid. Therefore, we synthesized 1 wt % Pd single-atom catalysts based on CTF-1, pyCTF, and bipyCTF supports and tested them in the gas-phase decomposition of formic acid. The results were compared with those obtained for a Pd catalyst supported on mesoporous graphitic-type carbon (Pd/C) with nanoparticles (∼2.3 nm). The catalysts were characterized by high-angle annular dark-field/scanning transmission electron microscopy (HAADF/STEM), extended X-ray absorption fine structure/X-ray absorption near-edge structure (EXAFS/XANES), and X-ray photoelectron spectroscopy (XPS) methods. The following order of catalytic activity was obtained: Pd/CTF-1 > Pd/C > Pd/pyCTF ≥ Pd/bipyCTF. The best performance of the Pd/CTF-1 catalyst was associated with Pd2+–C2N2 sites. Pd2+–N4 sites formed on pyCTF and bipyCTF supports showed lower catalytic activity. The selectivity trend at temperatures above 500 K was as follows: Pd/bipyCTF > Pd/pyCTF > Pd/CTF-1 > Pd/C. For the Pd/bipyCTF catalyst, the selectivity reached 99.8%, which is very high for this temperature range. These results may be important for the development of CTF-based catalysts for hydrogen production reactions. [ABSTRACT FROM AUTHOR]

Calcium aluminates (CA) with a mayenite structure have attracted a growing interest during the last decades. The present paper reports the preparation of vanadia-mayenite composites performed via an impregnation of pure CA with ammonium vanadate solution. The properties of the prepared materials were explored by a low-temperature nitrogen adsorption/desorption technique, X-ray diffraction analysis, transmission electron microscopy, and spin probe method. As revealed, the addition of vanadium significantly affects the textural properties and the porous structure of mayenite. The blockage of micropores by vanadium species is supposed. The spin probe electron paramagnetic resonance technique based on the adsorption of 1,3,5-trinitrobenzene, phenothiazine, and diphenylamine has been applied to study the active sites on the surface of the composite samples. The results demonstrated an increase in the concentration of weak electron-acceptor sites when the vanadium loading was 10 wt%. X-ray diffraction analysis and transmission electron microscopy studies showed that the composites consist of few phases including mayenite, CaO, and calcium vanadates. [ABSTRACT FROM AUTHOR]

In this paper, the influence of surface modification on the characteristics and properties of AlN thin films on Si and glass-ceramics substrates is investigated. The surface modification was made at various parameters of argon cluster ions. By using XRD and Raman spectroscopy, it was shown that the obtained AlN films have a hexagonal structure with a characteristic direction of texturing along the c axis and slight deviations from it. A comparison of the AlN surface morphology obtained by atomic force microscopy before and after cluster processing was demonstrated. This demonstrated that the cluster ions with low energy per atom (E/N = 10 eV/atom) have a high efficiency of surface smoothing. A decrease in the intensity of the Raman peaks and an increase in their full-width after bombardment with cluster ions were found, which may be caused by a change in the physicochemical state of the surface. The optical properties, the quality of the boundaries, and the distribution map of the thickness of the functional layer of AlN were investigated by the methods of spectral and spatial resolution ellipsometry. By using the cross-sectional SEM, the direction of crystallite texturing was demonstrated. The influence of argon cluster ion bombardment on the stoichiometry of samples was analyzed by EDX spectroscopy. The results obtained demonstrate the efficiency of the cluster ion smoothing of polycrystalline thin films for microelectronics, particularly when creating surface acoustic wave resonators. [ABSTRACT FROM AUTHOR]

The work reported here was aimed at determining differences in redox properties of simple and double oxides. Comparison between the reduction of double oxides (Mn,Co)3O4 and simple oxides Co3O4 and Mn3O4 was performed using in situ X-ray diffraction (XRD), temperature-programmed reduction (TPR) and transmission electron microscopy (TEM). The double oxides with a ratio of cations Mn : Co = 1 : 1 were prepared by the coprecipitation method and contained a mixture of 50% MnCo2O4 and 50% CoMn2O4. It was shown that the mechanism of reduction of double oxides with hydrogen differs significantly from the processes occurring on simple oxides. For simple cobalt and manganese oxides, transformations Co3O4→ CoO → Co and Mn3O4→ MnO are observed under a hydrogen atmosphere. The reduction of mixed-metal oxides occurs in two steps. In the first step, at 300–450 °C, (Mn,Co)3O4 transforms to (Mn,Co)O solid solutions. In situ XRD under isothermal conditions illustrates that Co-rich Co2MnO4 oxide starts to be reduced to Co0.6Mn0.4O first, and then Mn-rich Mn2CoO4 passes into Mn0.6Co0.4O. In the second step, at 450–700 °C, the reduction of solid solutions (Mn,Co)O to metallic cobalt Co and MnO proceeds. Again, the reduction begins with transformation of Co-rich oxide with the Co0.6Mn0.4O structure. The temperature of appearance of the intermediate phase (Mn,Co)O shifts to the higher values as compared to those observed for CoO, and to lower temperatures as compared to MnO during simple oxide reduction. [ABSTRACT FROM AUTHOR]

Single‐atom catalysts with ionic Pd active sites supported on nitrogen‐doped carbon nanotubes have been synthesized with a palladium content of 0.2–0.5 wt %. The Pd sites exhibited unexpectedly high stability up to 500 °C in a hydrogen atmosphere which was explained by coordination of the Pd ions by nitrogen‐containing fragments of graphene layers. The active sites showed a high rate of gas‐phase formic acid decomposition yielding hydrogen. An increase in Pd content was accompanied by the formation of metallic nanoparticles with a size of 1.2–1.4 nm and by a decrease in the catalytic activity. The high stability of the single‐atom Pd sites opens possibilities for using such catalysts in high‐temperature reactions. Better off alone: A highly stable single‐atom Pd catalyst was synthesized by using N‐doped carbon nanotubes (N‐CNTs) as a support. The N‐CNTs stabilize Pd as isolated ions and the resultant catalyst shows high activity in the formic acid decomposition reaction. [ABSTRACT FROM AUTHOR]

Parahydrogen-induced polarization (PHIP) was successfully utilized to demonstrate the strong metal-support interaction (SMSI) effect for palladium supported on titania catalysts. Heterogeneous hydrogenation of 1,3-butadiene over Pd/TiO2 catalysts led to the formation of 1- and 2-butenes and butane, and hyperpolarized products were obtained if parahydrogen was used in the reaction. However, if the catalysts were reduced in H2 flow at 500 °C before the hydrogenation reaction, the observed polarization levels were significantly lower or even zero, which was indicative of the suppression of the pairwise addition of hydrogen route. This observation indicated the possibility to detect the SMSI effect by the PHIP technique. Moreover, by using X-ray photoelectron spectroscopy it was shown that Pd is partially present as Pd δ+ after reduction under a hydrogen atmosphere at 500 °C. These results were confirmed by transmission electron microscopy, which revealed the formation of Pd δ+ and the dissolution of Pd in the titania lattice. [ABSTRACT FROM AUTHOR]

Two types of photocatalysts, 1%Pt/Cd1−xZnxS/g-C3N4 (x = 0.2–0.3) and Cd1−xZnxS/1%Pt/g-C3N4 (x = 0.2–0.3), were synthesized by varying the deposition order of platinum, and a solid solution of cadmium and zinc sulfides onto the surface of g-C3N4. The characterization of photocatalysts showed that, for 1%Pt/Cd1−xZnxS/g-C3N4, small platinum particles were deposited onto a solid solution of cadmium and zinc sulfides; in the case of Cd1−xZnxS/1%Pt/g-C3N4, enlarged platinum clusters were located on the surface of graphitic carbon nitride. Based on the structure of the photocatalysts, we assumed that, in the first case, type II heterojunctions and, in the latter case, S-scheme heterojunctions were realized. The activity of the synthesized samples was tested in hydrogen evolution from triethanolamine (TEOA) basic solution under visible light (λ = 450 nm). A remarkable increase in hydrogen evolution rate compared to single-phase platinized 1%Pt/Cd1−xZnxS photocatalysts was observed only in the case of ternary photocatalysts with platinum located on the g-C3N4 surface, Cd1−xZnxS/1%Pt/g-C3N4. Thus, we proved using kinetic experiments and characterization techniques that, for composite photocatalysts based on Cd1−xZnxS and g-C3N4, the formation of the S-scheme mechanism is more favorable than that for type II heterojunction. The highest activity, 2.5 mmol H2 g−1 h−1, with an apparent quantum efficiency equal to 6.0% at a wavelength of 450 nm was achieved by sample 20% Cd0.8Zn0.2S/1% Pt/g-C3N4. [ABSTRACT FROM AUTHOR]

We explored the photoreforming of rice and corn starch with simultaneous hydrogen production over a Cd0.7Zn0.3S-based photocatalyst under visible light irradiation. The photocatalyst was characterized by UV–vis diffuse reflectance spectroscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. The influence of starch pretreatment conditions, such as hydrolysis temperature and alkaline concentration, on the reaction rate was studied. The maximum rate of H2 evolution was 730 μmol·h−1·g−1, with AQE = 1.8% at 450 nm, in the solution obtained after starch hydrolysis in 5 M NaOH at 70 °C. The composition of the aqueous phase of the suspension before and after the photocatalytic reaction was studied via high-performance liquid chromatography, and such products as glucose and sodium gluconate, acetate, formate, glycolate, and lactate were found after the photocatalytic reaction. [ABSTRACT FROM AUTHOR]

Magnetoelectric nanoparticles (NPs) present an important class of nanomaterials with a wide interest in piezocatalytic and biomedical applications. Herein, the results of magnetoelectric and magnetization measurements performed on core–shell NPs having magnetic core (MnFe2O4, MFO) and ferroelectric shell (Ba0.85Ca0.15Ti0.5Zr0.5O3, BCZT) synthesized by the microwave hydrothermal method are reported. Magnetic results are compared with the measurements on reference MFO NPs prepared under identical conditions. Detailed SQUID magnetometer measurements of the magnetization hysteresis loops M(H) down to 2 K reveal the existence of a clear exchange bias effect in pure MFO NPs attributed to the coexistence of ferromagnetic and antiferromagnetic short‐range interactions. When the magnetic core is covered by the thin ferroelectric BCZT shell, it is observed that 1) the shell suppresses the apparent bias effect and 2) induces an “extra” ferromagnetic magnetization at T < 20 K. The results indicate that this “extra” ferromagnetism has a 2D character and it is most likely related to the interface interactions between the MFO core and BCZT shell. Ferroelectric properties and strong magnetoelectric effect in core–shell NPs are revealed via piezoresponse force microscopy under magnetic field. The mechanisms of the observed effects are discussed. [ABSTRACT FROM AUTHOR]

The front cover artwork for Issue 17/2015 is a collaboration between the International Tomography Center (Russia) and the Boreskov Institute of Catalysis (Russia). The image shows that palladium catalysts supported on titania and reduced in H2 flow at 500 °C exhibit a SMSI (strong metal-support interaction) effect, which dramatically reduces the pairwise hydrogen addition activity. See the Communication itself at . [ABSTRACT FROM AUTHOR]

A novel ultra-high-entropy rare earth orthoferrite (UHE REO) of Sc 1/16 Y 1/16 La 1/16 Ce 1/16 Pr 1/16 Nd 1/16 Sm 1/16 Eu 1/16 Gd 1/16 Tb 1/16 Dy 1/16 Ho 1/16 Er 1/16 Tm 1/16 Yb 1/16 Lu 1/16 FeO 3 nominal composition was successfully synthesized for the first time through a simple and efficient solution combustion approach. PXRD, Raman, and 57 Fe Mössbauer spectroscopy confirmed the high chemical and phase purity of the synthesized UHE REO (hereafter denoted as ΣREFeO 3 ), which belonged to the Pnma space group, typical of the perovskite-like rare earth orthoferrites. Despite the fact that the main X-ray reflections, vibration modes, and spectral Mössbauer components unambiguously indicate the single-phase nature of the sample, the results of SEM and TEM make it possible to establish the presence of a main (about 50 nm) and a minor ultrafine (about 10 nm) fraction of ΣREFeO 3 nanoparticles. The bimodal size distribution of nanoparticles was also reflected in the magnetic behavior of this substance: the presence of several sextet components in the Mössbauer spectra, the hard single-domain magnetic nature of the main fraction of 50 nm UHE REO nanoparticles, and the superparamagnetic state of the minor fraction of 10 nm UHE REO nanoparticles. Thus, the unusual features of nanostructured ΣREFeO 3 can potentially be used for the creation of new generations of transformers, magnetic memory systems, magnetic screens, radio devices, etc .

This is a comprehensive study on the reinforcement of electrospun poly(3-hydroxybutyrate) (PHB) scaffolds with a composite filler of magnetite-reduced graphene oxide (Fe 3 O 4 -rGO). The composite filler promoted the increase of average fiber diameters and decrease of the degree of crystallinity of hybrid scaffolds. The decrease in the fiber diameter enhanced the ductility and mechanical strength of scaffolds. The surface electric potential of PHB/Fe 3 O 4 -rGO composite scaffolds significantly increased with increasing fiber diameter owing to a greater number of polar functional groups. The changes in the microfiber diameter did not have any influence on effective piezoresponses of composite scaffolds. The Fe 3 O 4 -rGO filler imparted high saturation magnetization (6.67 ± 0.17 emu/g) to the scaffolds. Thus, magnetic PHB/Fe 3 O 4 -rGO composite scaffolds both preserve magnetic properties and provide a piezoresponse, whereas varying the fiber diameter offers control over ductility and surface electric potential., Competing Interests: The authors declare no competing financial interest., (© 2022 The Authors. Published by American Chemical Society.)