In this work, we comprehensively investigated the influence of Indium doping on the structure, magnetic and functional properties of strontium M-type hexaferrites SrFe12-xInxO19 nanoparticles (where x = 1.7, 1.8, 2.0). Colloidally stable SrFe12-xInxO19 nanoparticles (similar to 10 nm) were synthesized using a combination of the citrate method and high-energy ball milling. We demonstrate that doping reduces both the specific saturation magnetization and, especially, the coercivity to values compatible with high-frequency fields used in biomedicine. This enables the potential use of SrFe12-xInxO19-based materials as hyperthermia agents. The materials, when coated with Pluronic F-127 polymer, exhibited low cytotoxicity, supporting their biomedical applicability. The SLP parameters of the synthesized samples ranged from 3.5 to 6.4 W/g and depended on the doping level. Importantly, the materials possess a heating limit of 42-52 degrees C, eliminating the risk of overheating healthy tissues during hyperthermia. This maximum heating temperature results from a strong reduction in the Curie temperature induced by Indium doping. Furthermore, a complete correlation between the areas of the minor magnetic hysteresis loops and the SLP parameters indicates that heating under an alternating magnetic field is primarily due to remagnetization losses.

The influence of the lanthanide cation type and calcination temperature on the crystal, local, and electronic structures of both individual and high-entropy (HE) Ln chromates/chromites (Ln = La - Yb, and Y) prepared by a coprecipitation is studied by using synchrotron X-ray diffraction, X-ray absorption fine structure spectroscopy, Raman and Fourier transform infrared spectroscopies, scanning electron microscopy with energy-dispersive Xray spectroscopy, simultaneous thermal analysis, and inductively coupled plasma atomic emission spectroscopy. Calcination of X-ray amorphous precursors at 550 degrees C resulted in the formation of individual LnCrO4 chromates with monoclinic (sp. gr. P21/n for Ln = La) or tetragonal (sp. gr. I41/amd for Ln = Sm - Yb, Y) structure. The PrCrO4 and NdCrO4 samples were a mixture of monoclinic and tetragonal phases. The HE LnCrO4 chromates were characterized by tetragonal structure regardless of the Ln3+ cation type involved. A further increase in temperature >= 650 degrees C led to the formation of Ln chromites having the orthorhombic symmetry (sp. gr. Pnma for LaCrO3, sp. gr. Pbnm for individual Ln = Pr - Yb, Y, and HE chromites). For all synthesized LnCrO3 samples, the lattice parameters, unit cell volumes, Cr-O-Cr bond angles, average Ln-O distances diminish with decreasing the Ln3+ cation radius. On the contrary, the octahedral distortions within CrO6 units increase with decreasing the Ln3+ cation radius. An analysis of the electronic structure showed the presence of an oxidation state (3+) for both Ln and Cr cations in all synthesized precursors and Ln chromites, and Cr5+ for Ln chromates. The local environment of the Ln3+ and Cr3+ cations in HE Ln chromites is close to that of similar ions in individual compounds. The local environment of the La3+ cation in La-containing compounds differs significantly from that of Ln3+ cations in other Ln chromites (Ln = Nd, Sm, Eu, Gd, Dy, Ho, Yb, Y).

This study investigates the seed-mediated growth of CoFe2O4 nanoparticles by continuously injecting Co(acac)₂ and Fe(acac)₃ precursors into triethylene glycol under thermal decomposition conditions. We focused on the effects of precursor injection speed and synthesis temperature. The optimal injection rate was 40 mL/h, with higher rates causing excessive secondary nucleation, while lower rates led to nanoparticle aggregation due to faster ligand stripping than monomer adsorption. A novel growth mechanism was proposed, involving secondary nucleation and clusterization, where new seeds adsorb onto growing nanoparticles, aided by the absence of strong stabilizers. Growth kinetics were analyzed using the Arrhenius equation, yielding an activation energy of 40.8 kJ/mol. Temperature also played a critical role in crystallite growth and nucleation. As temperature increased, crystallite size grew from 3.4 ± 0.2 nm at 185 °C to 10.1 ± 0.5 nm at 265 °C, with minimal change in nanoparticle size measured by TEM. Magnetic measurements showed an increase in saturation magnetization, when the reaction temperature was increased. Same impact of temperature on coercive force was also observed. This increase was attributed to crystallite sizes exceeding the 7 nm threshold for CoFe2O4 and low lattice strain. According to hyperthermia measurements the heating ability improved with larger crystallite size and higher Ms, but excessive Hc​ for samples at 265 oC reduced efficiency. The findings enable precise control over nanoparticle growth and nucleation, allowing tailored synthesis of single- or polycrystalline CoFe2O4 with controlled magnetic properties. These advancements hold promise for a wide range of biomedical applications, including magnetic hyperthermia.

Aluminium nitride (AlN) thin films are grown by reactive sputtering on Silicon (Si) with (111) orientation at low temperature (<= 450 degrees C) for piezoelectric-based micro-electromechanical systems (MEMS). The grown AlN thin films were polycrystalline wurtzite hexagonal structure with a high texture coefficient for the (002) plane of orientation. The leakage current density by the current-voltage (I-V) measurement was found to be as low as 1.6 x10(-6) A cm(-2) in the grown films. The trapped charges are crucial in controlling these electrical characteristics, and low interface trap density (6.72 x10(10) cm(-2) eV) was observed for the sputtered AlN grown at a substrate temperature of 300 degrees C. This study on the structural and electrical properties of AlN/Si (111) at low substrate temperature is compatible with the complementary metal oxide semiconductor (CMOS) process for constructing piezoelectric-based MEMS devices for various applications.

This paper presents a study of microstructure formation in bioresorbable Fe-Mn-Si alloys for temporary implants under high-pressure torsion (HPT) at room temperature and at 300 °C. The effect of silicon on the mechanism of microstructure formation under HPT and, as a consequence, on the mechanical, corrosion and biological properties of the alloys is studied. It is established that Si promotes martensitic transformation. HPT leads to an increase in the microhardness values of the studied alloys from ~1560 MPa in the initial state to ~5500 MPa (160–560 HV) due to structure refinement and phase transformation. An increase in the electrochemical corrosion rate of Fe-Mn-Si alloys to ~0.5 mm/year is established due to grain refinement to nanosize and the formation of strain-induced martensite. In vitro cytotoxicity and induced hemolysis studies showed that Fe-Mn, Fe-Mn-3.7Si, and Fe-Mn-5Si alloys after annealing and HPT can be characterized as biocompatible.

The mechanical properties of spark plasma sintered Ni, such as hardness, tensile strength, compression resistance at 25 and 750 degrees C while maintaining good ductility and dynamic impact wear resistance were greatly improved by applying high-energy ball milling and introducing a small amount of amorphous boron as a reactive additive. An excellent combination of properties has been achieved by forming a submicron microstructure and nanocrystalline h-BN reinforcing layers.

A new dual-functional implant based on gellan-xanthan hydrogel with calcium-magnesium silicate ceramic diopside and recombinant lysostaphin and bone morphogenetic protein 2 (BMP-2)-ray is developed. In this composite, BMP-2 is immobilized on microparticles of diopside while lysostaphin is mixed directly into the hydrogel, providing sustained release of BMP-2 to allow gradual bone formation and rapid release of lysostaphin to eliminate infection immediately after implantation. Introduction of diopside of up to 3% (w/v) has a negligible effect on the mechanical properties of the hydrogel but provides a high sorption capacity for BMP-2. The hydrogels show good biocompatibility and antibacterial activity. Lysostaphin released from the implants over a 3 h period efficiently kills planktonic cells and completely destroys 24 h pre-formed biofilms of Staphylococcus aureus . Furthermore, in vivo experiments in a mouse model of critically-sized cranial defects infected with S. aureus show a complete lack of osteogenesis when implants contain only BMP-2, whereas, in the presence of lysostaphin, complete closure of the defect with newly formed mineralized bone tissue is observed. Thus, the new implantable gellan-xanthan hydrogel with diopside and recombinant lysostaphin and BMP-2 shows both osteogenic and antibacterial properties and represents a promising material for the treatment and/or prevention of osteomyelitis after bone trauma.

The processing route of Sm2Fe17 carbides is shorter than that of nitrides, which can potentially be used for cost-effective mid-performance magnets’ production. The magnetic properties of Sm2Fe17Cx compounds can be controlled at the annealing step, which allows them to be used for a variety of applications. In this work, X-ray diffraction (XRD) analysis, Mössbauer spectroscopy, scanning and transmission electron microscopy (SEM, TEM) and vibrating sample magnetometry (VSM) were used for characterization of the structure and magnetic properties of Sm2Fe17Cx compounds. The powder samples were prepared by high-energy ball milling of Sm2Fe17 mixtures with carbon nanotubes (CNT) or graphite with subsequent annealing. The formation of Sm2Fe17Cx compounds after annealing was followed by the formation of α-Fe and amorphous Sm2O3. The hyperfine field values of Fe atoms of all the Sm2Fe17 lattice sites increased by 12% on average after annealing that was caused by carbon diffusion. The coercivity of the samples peaked after annealing at 375 °C. The samples with CNT demonstrated an increase of up to 14% in coercivity and 5% in specific remanence in the range of 250–375 °C annealing temperatures.

A ferrocene-containing oligoorganosiloxane with a number-average degree of polymerization of 8.8 and a number-average molecular weight of 3200 is synthesized by hydrolytic condensation of 3-aminopropyltriethoxysilane followed by chemical modification of the resulting oligomer with acetylferrocene. Its structure is characterized by MALDI-TOF, NMR and IR spectroscopy. 1H NMR spectroscopy shows the predominance of more thermodynamically stable units containing anti-configuration Schiff bases. Using IR spectroscopy as well as experimental determination of surface energy and its polar (acid-base) and dispersion components, the covalent immobilization of ferrocene-containing oligoorganosiloxane on a glass surface after heating at 110 degrees C is shown. The formed coating provides hydrophobization, acid-base indifference of the glass surface and serves as a precursor for the formation of magnetically soft materials after pyrolysis in argon already at 350 degrees C. The main stages of ferrocene-containing oligoorganosiloxane thermal destruction in an inert atmosphere and the formation of a mixture of iron and silicon oxides during its thermal oxidative destruction are established by combination of TGA/DTA, IR spectroscopy and elemental analysis. The proposed approach opens up new possibilities for functionalizing silicates surfaces, creating magnetic glasses, as well as regulating surface energy and its components.

Tool-grade steels designed for the manufacture of hot-forming dies have been studied. An economically alloyed modified steel 70Kh3G2FTR(m) is proposed, which has a fine metal base structure with uniform carbide hardening in the heat-treated state. The comparative structural studies with traditional tool-grade steels (5KhGM, 4Kh5MFS) at different stages of heat treatment, as well as the statistical analysis of mechanical properties (hardness and toughness) from thermal hardening parameters, allowed us to develop an optimal heat treatment technology, which provided the required indicators for the structure, hardness, and heat resistance of the material. It is shown that 70Kh3G2FTR(m) steel retains its strength and the effect of microalloying at elevated operating temperatures, which is confirmed by data from transmission electron microscopy, dynamic mechanical analysis, and thermophysical properties in the field of operating temperatures up to 400 °C, as well as studies of the samples’ texture under thermal exposure. The assessment of the mechanical properties, wear resistance, and economic effect of the introduction of the developed material and its thermal hardening technology make it possible to reasonably recommend 70Kh3G2FTR(m) steel as a rational replacement for traditional materials.

Ultra-small iron oxide nanoparticles (USNPs) have attracted particular attention in the past 15 years as perspective contrast agents for MRI. Unfortunately, the synthesis of such small nanoparticles with high contrast properties and water dispersibility is still challenging. This paper presents a study on the influence of synthetic conditions on the structure and the properties of hydrophilic iron oxide nanoparticles obtained by a simple single-step thermal decomposition in diethylene glycol at 230–235 °C. The samples were studied using X-ray diffraction, Mössbauer and infra-red spectroscopy, transmission electron microscopy, vibrating sample magnetometry, MRI, and dynamic light scattering. All the obtained samples are of spinel structure (Fd-3 m), specific to both magnetite and maghemite. With an increase in the synthesis time from 1 to 8 h, the crystallite size of the series with C(Fe(acac)3) = 30 mM changed from 1.8 ± 0.2 to 4.7 ± 0.5 nm, the average size according to TEM changed from 3.3 ± 0.8 to 3.8 ± 0.4 nm, and the saturation magnetization from 13.9 ± 0.3 to 83.3 ± 1.7 A•m2/kg, which is close to the values of bulk iron oxide. The same tendency was revealed with the increase in the concentration of C(Fe(acac)3) from 30 to 120 mM for 1 h of synthesis. An increase in the synthesis time for 60- and 120-mM solutions did not significantly change the crystallite size and the magnetic properties. It was shown that the samples obtained using this approach have unexpectedly high values of r2-relaxivity, up to 235 mM−1•s−1, which the highest published for USNPs. The studied method of water-soluble USNPs is promising for use in creating T2-contrast agents for MRI.

The synthesis and detailed study of six series of high-entropy complex oxides containing lanthanides (Ln) and transition metals with the general formula Ln(2)M(2)O(7) (Ln = La-Yb, and Y; M = Ti, Zr, and Ce) with the number of different Ln cations not less than six in each case are reported. The influence of synthesis conditions (types of the Ln(3+) and M4+ cations, calcination temperature) used in the synthesis via either coprecipitation or sol-gel method on the crystal and local structures of target materials is comprehensively surveyed. The studies were carried out using a combination of long- (s-XRD), medium- (Raman, FT-IR, SEM-EDS) and short-range (XAFS) sensitive techniques, as well as AES-ICP and STA. It was established that the ratio of the cation radii gamma = (r) over bar (3+)(Ln)/(r) over bar (4+)(M) is the main factor that determines the type of initially formed crystal structure. In the boundary region (gamma similar to 1.42-1.47), the average radius of lanthanide cation ((r) over bar (3+)(Ln)), along with the (r) over bar (3+)(Ln)/(r) over bar (4+)(M) ratio, also plays a significant role in the type of the resulting crystal structure of the high-entropy lanthanide complex oxides. The presence of inhomogeneity in the distribution of elements in precursors significantly affects the phase composition of the resulting high-entropy oxides. An increase in the calcination temperature promotes not only the occurrence of subsequent phase transitions, but also an increase in the single-phase nature of the resulting high-entropy complex rare-earth oxides. At the same time, the cations included in the composition retain some independence, despite the fact that they occupy one crystallographic position in the resulting crystal structure.

For the first time, the formation of Al@Al2O3 core-shell nanowires with a width of 50-160 nm and a length of 0.1-1.1 mu m was observed on the surface of oxidized Al particles when heated to 900 and 1000 degrees C. The nanowires were characterized by SEM-EDS, X-ray diffraction, XPS, and TEM. In addition, temperature-activated nanowire growth was monitored in-situ using TEM. Based on experimental observations and molecular dynamics simulations, an Al@Al2O3 core-shell nanowire formation model controlled by the pressure-assisted diffusion of Al2O intermediates was proposed. The modeling indicated the potential formation of Al2O suboxide molecules at the internal interface between Al2O3 shell and the Al melt at a temperature of 900 degrees C, followed by their diffusion through the nanopores of the oxide shell to the surface. There they underwent disproportionation into Al and Al2O3, which ultimately led to the formation of nanowires. The directed nanostructure growth from the surface is elucidated by the pressure gradient between the excess pressure inside the Al2O3/Al particles and the ambient pressure. The obtained results can be used in the creation of micro- and nanoelectronics products, for the manufacture of sensors and catalysts, as well as for the synthesis of Al-based composites reinforced with nanostructures.

In this work, a new two-stage scalable method for the synthesis of magnetite nanoparticles for biomedical applications is proposed. The influence of the milling time, medium, and surfactants on the formation of the structure, magnetic, and functional properties of magnetite nanoparticles has been studied. Comprehensive investigation of the formation of the structure and properties of magnetite nanoparticles has been carried out using X-ray diffraction analysis, scanning and transmission electron microscopy, Mössbauer spectroscopy, measurements of magnetic properties, specific loss power (SLP), and cytotoxicity. It was shown that the milling medium of water with the addition of trisodium citrate is a harsher milling condition compared to octadecene-1 with the addition of oleic acid. Continuous milling for 50 h allowed to obtain a fraction of colloidally stable nanoparticles at the level of 80–90%. Harsher milling conditions led to the formation of a larger fraction of superparamagnetic particles, which reduced the coercivity and SLP. The maximum SLP value of 1140 W/g was reached by large particles, while nanoparticles had decreased SLP values of 100–190 W/g, which was completely determined by the coercivity dependence. Different synthesis conditions allowed obtaining particles with different cytotoxicity against PC-3 cells.

In this work, the methods of X-ray diffraction analysis (XRD), transmission electron microscopy (TEM), Mo ssbauer spectroscopy (MS), magnetic properties measurements and specific loss measurements (hyperthermia) were used for the investigation of the structure and properties of Fe 3-x Co x O 4 nanoparticles. The Fe 3-x Co x O 4 nanoparticles were synthesized by using high-energy ball milling of Fe and Co mixed with water and surfactant additives. Co substitution increased the coercivity of the samples and changed the kinetics of oxidation process. The presence of cobalt ferrite was verified by MS. TEM images of synthesized samples demonstrated 5-50 nm particle size. Specific loss related heating effect depended mostly on the ratio between the samples coercivity and the amplitude of the high-frequency field. Specific loss power (SLP) and intrinsic loss power (ILP) values reached 164 W/g and 1.57 nH.m 2 /kg, respectively.

The parent compound BaBiO3 of bismuthate high-temperature superconductors (HTSCs) BaBi(Pb)O3 and Ba(K)BiO3 with perovskitelike structure exhibits unusual electronic and structural properties, which can be satisfactorily explained if we assume that all charge carriers are in the paired state. However, the prior experiments and the first-principle calculations only indirectly indicate the existence of paired charge carriers in BaBiO3. In this work, we report the direct evidence of initially paired electrons and holes in the upper antibonding Bi 6s−O2pσ* orbital of the neighboring octahedral complexes in the ground state of BaBiO3 using the time-resolved x-ray absorption spectroscopy (XAS) to monitor the electron dynamics after the femtosecond resonant 633 nm laser excitation. We observe strong changes in the oxygen K-edge XAS preedge region, defined by the Bi6s−O2pσ* orbitals. We interpret them as a fast (≤0.3 ps) breaking of charge carrier pairs and slower (0.3–0.8 ps) lattice rearrangement from the distorted monoclinic structure into the new metastable state with a cubic lattice, which persists at least up to 60 ps after the excitation. Analysis of the intermediate state at the fast excitation shows that the bond disproportionation and monoclinic distortion of BaBiO3 structure are energetically favorable due to the charge carrier pairing. Thus the compound BaBiO3 forms a new quantum state that we define as a local pair density wave. Taking into account a large number of similarities between bismuthate and cuprate high-temperature superconductors, we believe that our work will give a new impetus to understanding the nature of superconductivity in perovskite HTSCs. Published by the American Physical Society 2024

The influence of Yb3+ cations substitution for Pr3+ on the structure and catalytic activity of (Pr1−xYbx)2Zr2O7 powders synthesized via coprecipitation followed by calcination is studied using a combination of long- (s-XRD), medium- (Raman, FT-IR, and SEM-EDS) and short-range (XAFS) sensitive methods, as well as adsorption and catalytic techniques. It is established that chemical composition and calcination temperature are the two major factors that govern the phase composition, crystallographic, and local-structure parameters of these polycrystalline materials. The crystallographic and local-structure parameters of (Pr1−xYbx)2Zr2O7 samples prepared at 1400 °C/3 h demonstrate a tight correlation with their catalytic activity towards propane cracking. The progressive replacement of Pr3+ with Yb3+ cations gives rise to an increase in the catalytic activity. A mechanism of the catalytic cracking of propane is proposed, which considers the geometrical match between the metal–oxygen (Pr–O, Yb–O, and Zr–O) bond lengths within the active sites and the size of adsorbed propane molecule to be the decisive factor governing the reaction route.

The effect of the melt cooling rate on the atomic ordering of austenite and, as a consequence, on the martensitic transformation of a nonstoichiometric alloy of the Ni-Mn-In system has been studied. In situ TEM observations revealed differences in the mechanism of phase transformations of the alloy subjected to different cooling conditions. It is shown that during quenching a high density of antiphase boundaries (APB) is formed and the alloy is in the austenite–martensitic (10M and 14M) state up to a temperature of 120 K. In a slowly cooled alloy, a lower APB density is observed, and a two-stage transformation, L21/B2 → 10M → 14M, occurs in the range of 150–120 K.

Nowadays, magnetoelectric nanomaterials are on their way to finding wide applications in biomedicine for various cancer and neurological disease treatment, which is mainly restricted by their relatively high toxicity and complex synthesis. This study for the first time reports novel magnetoelectric nanocomposites of CoxFe3−xO4-BaTiO3 series with tuned magnetic phase structures, which were synthesized via a two-step chemical approach in polyol media. The magnetic CoxFe3−xO4 phases with x = 0.0, 0.5, and 1.0 were obtained by thermal decomposition in triethylene glycol media. The magnetoelectric nanocomposites were synthesized by the decomposition of barium titanate precursors in the presence of a magnetic phase under solvothermal conditions and subsequent annealing at 700 °C. X-ray diffraction revealed the presence of both spinel and perovskite phases after annealing with average crystallite sizes in the range of 9.0–14.5 nm. Transmission electron microscopy data showed two-phase composite nanostructures consisting of ferrites and barium titanate. The presence of interfacial connections between magnetic and ferroelectric phases was confirmed by high-resolution transmission electron microscopy. Magnetization data showed expected ferrimagnetic behavior and σs decrease after the nanocomposite formation. Magnetoelectric coefficient measurements after the annealing showed non-linear change with a maximum of 89 mV/cm*Oe with x = 0.5, 74 mV/cm*Oe with x = 0, and a minimum of 50 mV/cm*Oe with x = 0.0 core composition, that corresponds with the coercive force of the nanocomposites: 240 Oe, 89 Oe and 36 Oe, respectively. The obtained nanocomposites show low toxicity in the whole studied concentration range of 25–400 μg/mL on CT-26 cancer cells. The synthesized nanocomposites show low cytotoxicity and high magnetoelectric effects, therefore they can find wide applications in biomedicine.

The synthesis and detailed study of six series of high-entropy complex oxides containing lanthanides (Ln) and transition metals with the general formula Ln2M2O7 (Ln = La-Yb, and Y; M = Ti, Zr, and Ce) with the number of different Ln cations not less than six in each case are reported. The influence of synthesis conditions (types of the Ln3+ and M4+ cations, calcination temperature) used in the synthesis via either coprecipitation or sol–gel method on the crystal and local structures of target materials is comprehensively surveyed. The studies were carried out using a combination of long- (s-XRD), medium- (Raman, FT-IR, SEM-EDS) and short-range (XAFS) sensitive techniques, as well as AES-ICP and STA. It was established that the ratio of the cation radii γ = r̄Ln3+/r̄M4+ is the main factor that determines the type of initially formed crystal structure. In the boundary region (γ∼ 1.42–1.47), the average radius of lanthanide cation (r̄Ln3+), along with the r̄Ln3+/r̄M4+ ratio, also plays a significant role in the type of the resulting crystal structure of the high-entropy lanthanide complex oxides. The presence of inhomogeneity in the distribution of elements in precursors significantly affects the phase composition of the resulting high-entropy oxides. An increase in the calcination temperature promotes not only the occurrence of subsequent phase transitions, but also an increase in the single-phase nature of the resulting high-entropy complex rare-earth oxides. At the same time, the cations included in the composition retain some independence, despite the fact that they occupy one crystallographic position in the resulting crystal structure.