AbstractIn the course of synthesis and studies of properties of nanomaterials based on layered molybdenum disulfide, it becomes necessary to perform rapid elemental analysis and to return the material to customer promptly. In some cases, to improve catalytic or magnetic properties, it is required to modify nanoparticles of molybdenum disulfide by metal compounds. A procedure is proposed for rapid X-ray fluorescence determination of molybdenum and cobalt in the content range of 10–50% in similar compounds by a bulk method without dilution. Analytical signals have been measured at the wavelengths of the MoKα and CoKα lines using a VRA-30 spectrometer (Carl Zeiss, Germany, X-ray tube with Rh anode). The content of the metals has been calculated using the derived equations of interrelations. The error of determination is ±2.7% (abs.) for Mo and ±1.4% (abs.) for Co. Correctness of the procedure has been confirmed for a batch of synthesized compounds by comparison with XRF results with dilution. This rapid method makes it possible to simplify the procedure and to reduce the time of analysis by more than 4 times; here, the sample is retained and can be used for further research.

Abstract—β-Tricalcium phosphate (β-Ca3(PO4)2) based ceramics with a relative density of 20–21%, grain size from 200 to 600 nm, and compressive strength from 1.6 to 1.8 MPa have been produced by 1000°C firing of cement stone prepared from a powder mixture having a Ca/P molar ratio of 1.5 and consisting of hydroxyapatite (Ca10(PO4)6(OH)2), calcium citrate tetrahydrate (Ca3(C6H5O7)2·4H2O), and calcium dihydrogen phosphate monohydrate (Ca(H2PO4)2·H2O). The mixing liquid used to initiate chemical binding reaction in the powder mixture was distilled water. The phase composition of the cement stone included brushite (CaHPO4·2H2O) and unreacted starting materials. The presence of platelike calcium pyrophosphate (Ca2P2O7) particles, formed from platelike brushite (CaHPO4·2H2O) particles, impeded densification of the ceramics during firing and ensured the formation of an ultraporous structure. The submicron-grained microstructure and phase composition of the β-Ca3(PO4)2-based ceramics resulted mainly from heterophase interactions between the products of thermal decomposition of cement stone components. Offering sufficient strength, biocompatible and bioresorbable ultraporous submicron-grained β-Ca3(PO4)2-based ceramics can be recommended for use in regenerative medicine for bone tissue defect repair.

Abstract—A lightweight Ti20Al3Si9-based intermetallic alloy with porosity under 3% has been prepared for the first time by compaction in the self-propagating high-temperature synthesis (SHS) regime. The microstructure of the synthesis product has been studied by scanning electron microscopy and time-of-flight mass spectrometry. The content of the major phase, Ti20Al3Si9, in the alloy is 87 wt %, and that of the Ti3Al phase is 13 wt %. A mechanism has been proposed for phase formation in the ternary intermetallic system Ti–Al–Si during the SHS process. The increased microhardness of the alloy (9905 ± 450 MPa) is due to the formation of the Ti20Al3Si9 phase, rich in Si (about 28.13 at %).

Abstract—We report a comparative study of the chemical and thermal stability and mechanical properties of arc PVD TiN and Ti0.97Al0.03N coatings. Heating the coatings in vacuum to 600 and 700°C has been shown to cause an increase in crystallite size and a decrease in biaxial macrostress, lattice parameter, and lattice strain. These effects are due to thermally activated structure restoration processes associated with annihilation of defects generated during the growth of the coatings. The stress relaxation rate in the Ti0.97Al0.03N coating is higher because it contains a higher defect density. At 700°C, the Ti0.97Al0.03N solid solution undergoes spinodal decomposition into TiN and AlN (FCC). Unlike those of the TiN coating, the hardness and the parameters H3/E2 and H/E of the Ti0.97Al0.03N coating remain essentially unchanged as the annealing temperature is raised to 700°C, which is due to dispersion hardening as a result of the spinodal decomposition. The coatings exhibit similar behavior in acidic and alkaline media, but Ti0.97Al0.03N has a somewhat higher oxidation resistance in air at 550°C.

Abstract—This paper examines the effect of size parameters of magnesium hydroxide nanoparticles prepared by different methods on the formation of hydrosilicate nanoscrolls with the composition Mg3Si2O5(OH)4 under hydrothermal conditions, their geometric characteristics, and their thermal behavior. Magnesium hydrosilicate nanoscrolls with the chrysotile structure have been shown to form regardless of the hydrothermal treatment time and the method used to prepare magnesium hydroxide. At the same time, the nanoscroll length distribution and, especially, the nanoscroll diameter distribution depend on the method used to prepare magnesium hydroxide. In the case of hydrosilicate samples synthesized from Mg(OH)2 prepared by mixing reagents in microreactor with free impinging jets, the exothermic peak due to the conversion of magnesium hydrosilicate into magnesium silicate with the forsterite structure is located at a temperature of 817°C, whereas in the case of samples prepared from magnesium hydroxide synthesized via reverse precipitation the peak is shifted to higher temperatures (825°C).

Abstract—A highly porous material based on submicron titanium carbide powder has been prepared using a pore former. General mechanisms underlying the formation of the pore structure of the material have been identified as functions of the volume fraction of the pore former and sintering temperature, varied in the ranges 75–85% and 1200–1500°C, respectively. Increasing the porosity of the material has been shown to raise its permeability and reduce its strength. At a given porosity, raising the sintering temperature from 1200 to 1500°C allows a material with higher permeability to be obtained, which is accompanied by an increase in its strength.

Abstract—We have studied glass formation and crystallization in the CdO–B2O3–SiO2 system. Glasses were prepared in the composition range from 21.12 to 87.00 mol % CdO. No CdO–B2O3–SiO2 phase diagram has been reported to date, so glass preparation conditions were chosen using available phase diagrams of alkaline-earth borosilicate ternary systems and empirically. We have located the glass-forming region in the CdO–B2O3–SiO2 system and identified the crystalline phases forming during the glass preparation process.

Abstract—SiNx films with low mechanical stress have been grown in an inductively coupled plasma (ICP) reactor using a SiH4 + N2 + Ar gas mixture. Nitrogen-enriched SiNx films under compressive stress from –10 to –50 MPa have been obtained at [SiH4]/[N2] from 0.55 to 1.0 and an ICP source power of 600 W. All other deposition conditions being constant, raising the ICP source power leads to an increase in stress level from –125 MPa at 300 W to –625 MPa at 800 W. Varying the deposition temperature in the range 25–350°C has little effect on the stress level and refractive index of the films and the SiNx growth rate. We have assessed residual stress drift in the SiNx films during three weeks after deposition and the effect of deposition conditions on the percentage of oxygen in the films.

Abstract—A composite consisting of 80 mol % α''-Cd2.76Mn0.24As2 and 20 mol % MnAs has been synthesized and characterized by X-ray diffraction, differential thermal analysis, and microstructural analysis. The results demonstrate that the composite is a soft ferromagnetic material with a Curie temperature of 328 K. In the temperature range 4–300 K, its electrical conductivity shows metallic behavior. The composite has a high positive magnetoresistance, up to 600% in a magnetic field of 8 T. The nature of its magnetoresistance is determined by the Lorentz force, which suppresses the effect of the spin magnetic moments of the MnAs ferromagnet. Owing to the linear behavior of the temperature and magnetic field dependences of its electrical resistance, the composite is of practical interest for use as a material for temperature and magnetic field sensors.

AbstractBiosensor devices that include hybrid nanostructures as transducer surface modifiers meet current requirements for methods of research and determination of drugs, including antidepressants. Here, we consider the features of amperometric monoamine oxidase biosensors based on screen-printed graphite electrodes modified with nanocomposite consisting of C60/cobalt nanoparticles/amino derivative of a second-generation polyether polyol/chitosan in the determination of the tricyclic antidepressant amitriptyline. The best modifier was selected using transmission electron microscopy, scanning electron microscopy, electrochemical impedance spectroscopy, and differential pulse voltammetry. In the biosensor development, the conditions for applying the composite based on cobalt nanoparticles/amino derivative of polyether polyol to the electrode surface were varied: electrochemical deposition, sequential deposition by the layer-on-layer method, and deposition of a mixture. As an analytical signal of the biosensor, we used the peak of the electrochemical oxidation of hydrogen peroxide, which is formed during the enzymatic oxidation of serotonin under the action of monoamine oxidase. The operating principle of the biosensor is based on the inhibitory effect of amitriptyline on the catalytic activity of immobilized monoamine oxidase. For the selected modifier, the determined concentration range of amitriptyline is 1 × 10–4–1 × 10–8 mol/L and the lower limit of the determined contents is 5 × 10–9 mol/L under optimal operating conditions. Comparison of the results of the amitriptyline determination in a pharmaceutical preparation and urine that were obtained using a monoamine oxidase biosensor and the method of fluorescence polarization immunoassay (dilution of the tracer of 1 : 32, dilution of antibodies of 1 : 128, range of working concentrations from 5 × 10–8 to 5 × 10–9 mol/L), which has proven itself in the determination of medicinal substances, confirmed the correctness of the developed method.

AbstractNanoporous carbon (carbide-derived carbon (CDC)) has been prepared via high-temperature chlorination of a spherical NbC/C nanocomposite synthesized by a new process [19]. The CDC has been characterized by X-ray diffraction, Raman spectroscopy, scanning electron microscopy in combination with energy dispersive X-ray analysis, and transmission electron microscopy. Using nitrogen adsorption–desorption measurements, we have determined the average pore size (3.627 nm), pore size distribution, and total pore volume (1.215 cm3/g) in the CDC and calculated its specific surface area by the BET method (817.282 m2/g). The electrochemical behavior of the nanoporous carbon (CDC) has been studied using half-cell cyclic voltammetry measurements in the potential sweep range from –1.0 to +1.0 V vs. carbon and impedance spectroscopy.

Abstract—We have studied the effect of doping with tin and titanium cations on the electrochemical performance of lithium-rich cathode materials. Samples for this investigation were prepared via coprecipitation of precursors, followed by solid-state reaction with a lithium and tin (titanium) source. The cathode materials have been characterized by X-ray diffraction, scanning electron microscopy, and X-ray microanalysis and tested in lithium half-cells in galvanostatic cycling mode at various current densities. The titanium-doped material had a considerably higher specific discharge capacity (270 mAh/g) in comparison with the undoped and tin-doped materials (230 mAh/g). As the charge/discharge current was raised, the titanium-doped sample exhibited the best cycling stability among all of the materials. In addition, both doped materials had a smaller voltage hysteresis in comparison with the undoped sample.

AbstractLiquid chromatography–high-resolution mass spectrometry that combines the capabilities of highly selective separation of mixtures under study, valid detection of unknown substances, and high sensitivity is widely used for the detection of biologically active components in mixtures with a complex composition, to which biological fluids (blood, urine, etc.) belong. A method for the simultaneous extraction of highly polar biomarkers of nitrogen mustards such as N-triethanolamine (TEA), N-ethyldiethanolamine (EDEA), and N-methyldiethanolamine (MDEA) from urine followed by their determination by high-performance liquid chromatography (HPLC) combined with high-resolution tandem mass spectrometry is proposed. The mass spectra of fragmentation of protonated molecular ions of TEA, EDEA, and MDEA are studied, and possible structural formulas of the fragment ions are given. The conditions of the sample preparation of urine and mass spectrometric detection in the multiple reaction monitoring mode are optimized. The option of fivefold dilution with deionized water is chosen as a method of sample preparation of urine for the analysis. The separation of the components is performed in the reversed-phase chromatography mode with the retention times for TEA, EDEA, and MDEA of 2.00, 2.05, and 1.92 min, respectively. The time required to complete all the steps of the analysis of urine samples does not exceed 25 min. The detection limits of the biomarkers in urine are 1 ng/mL for TEA and 2 ng/mL for EDEA and MDEA. The developed approach makes it possible to determine the fact of application of specific nitrogen mustards in inquiry of possible exposure of a living organism to blister agents.

Abstract—We report the preparation of SmS@Y2O2S and Y2O2S@SmS ceramics with a core–shell nanostructure via 1123-K sulfidation of rare-earth oxides prepared by the sol–gel method, involving precipitation from starting metal nitrate solutions with NH4OH as a precipitant, followed by annealing of the resultant sulfide phases in an induction furnace at 1473 K. Using X-ray diffraction and scanning electron microscopy data, we have evaluated the average crystallite size in the materials and examined the morphology of the constituent phases in them. In addition, the short-range order in the coexisting nanostructures has been analyzed in detail using Raman spectroscopy and X-ray photoelectron spectroscopy data.

Abstract—X-ray photoelectron spectroscopy has been used to study structural evolution of zinc oxide synthesized by a sol–gel process adapted to flexible electronics. We assessed the effect of ultraviolet irradiation time on the atomic percentages of different Zn, O, and C species. Increasing the UV treatment time from 90 to 150 min has been shown to considerably reduce zinc concentration in the surface layer, which is accompanied by an increase in the percentage of carbon, predominantly in the form of highly oriented pyrolytic graphite. Photoactivation processes ensure completion of surface structure formation and lead to enrichment of the ZnO surface in oxygen with a binding energy of 531.5 eV, resulting in a zinc-deficient solid solution.

Abstract—Recently, the number of projects has grown connected with the application of high-temperature superconductors (HTSC) with exceptionally high current-carrying characteristics in strong magnetic fields. However, the thickness of the RBa2Cu3O7–x (R = REE, Y) superconducting layer is only 1–2% of the thickness of HTSC tape. Increasing the current-carrying characteristics owing to the thickness of the conducting layer is a promising approach. The fundamental problem of crystallite formation of a-oriented crystallites prevents the development of this approach. Such crystallites do not carry superconducting current along the substrate tape and interfere with the growth of c-oriented crystallites. This review presents existing methods of suppression of a-oriented growth, the basis of the creation of HTSC materials, and prospects of obtaining HTSC materials with high current-carrying characteristics.

Abstract—The phase complex of a ternary reciprocal system of lithium and rubidium bromides and chromates has been studied theoretically and experimentally for the first time. We have divided the phase complex into secondary phase compatibility triangles and obtained a linear phase tree, in which the vertices of each simplex describe crystallizing phases. Using the ion balance method, we have described chemical transformations and predicted crystallizing phases for mixtures with a preset composition. Using data for the bounding systems, we have constructed a computer 3D model of the phase complex and obtained polythermal and isothermal sections and liquidus surface isotherms. Using differential thermal analysis and X-ray diffraction, we have demonstrated adequacy of the proposed division into simplexes. Phase equilibria in the system have been studied experimentally, and we have determined the composition and melting point of ternary invariant points. The composition of the ternary eutectic E3 245 is recommended for use as a fusible electrolyte for electrochemical cells. Comparison of experimental data with prediction results derived from the model demonstrates adequacy of modeling of phase equilibria with the use of a 3D model.

Abstract—Using a variety of physicochemical characterization techniques, we have determined the composition and chemical formula of lanthanum and neodymium compounds with phthalic acid, synthesized for the first time. The compounds have been shown to have similar chemical formulas: La2(L)3·7H2O and Nd2(L)3·6H2O. We have examined the thermal destruction of the synthesized compounds. The proposed schematic structure of the La complex consists of zigzag 2D polymer layers, which are cross-linked by water molecules to form a 3D structure—a supramolecule.

Abstract—The conditions and kinetics of yttrium aluminum garnet (YAG) crystallization from an X-ray amorphous mixture of hydrated yttrium and aluminum compounds (with a stoichiometric yttrium to aluminum ratio) containing various functional groups have been studied by simultaneous thermal analysis, and temperature variations of the composition of conversion products have been monitored by X-ray diffraction. The technique used to analyze nonisothermal differential scanning calorimetry data in order to assess parameters and gain detailed insight into the mechanism of YAG formation can serve as a basis for predicting temperature and time conditions of formation of not only YAG but also other functional crystalline phases in designing modified and novel ceramic and glass-ceramic materials.

Abstract—We have studied the effect of monoclinic ZrO2 additions (1.5, 5, and 10 vol %) on the shrinkage kinetics of submicron α-Al2O3 powder. Ceramic samples were prepared by two-step spark plasma sintering (SPS). It has been shown that the two-step SPS process (heating to the temperature corresponding to 90% relative density and isothermal holding at this temperature) allows one to obtain ceramics with ultrafine-grained microstructure and high, near-theoretical density. Large ZrO2 additions (10%) lead to an increase in the activation energy for SPS and a decrease in grain-boundary deformation rate in the isothermal holding step.