Search

This work deals with the problem of synthesis and investigation of the structure and properties of polymer calcium phosphate biopolymer suspensions, their use to obtain film samples containing drugs, and the study of the kinetics of drug release from the polymer matrix. The compositions were synthesized using the method of mechano-acoustic activation. The use of the mechano-acoustic activation technique and ultrasonic dispersion makes it possible to synthesize calcium phosphate compounds in aqueous media, to modify the synthesized products with drugs and bioactive substances, and to form biocompositions for the manufacture of bone implants.

H2O absorption lines broadened by air pressure were recorded in the 5900–6100-cm−1 spectral region with the use of a Bruker IFS 125 HR spectrometer. The intensities and broadening and shift coefficients of H2O absorption lines are determined for the Voigt profile and the modified Voigt profile which takes into account the dependence of the broadening on the speed of the colliding molecules. The atmospheric transmission is calculated with the use of H2O line parameters from different versions of the HITRAN and GEISA spectroscopic databases and our new data. Model spectra are compared with atmospheric solar spectra measured with a ground-based Fourier spectrometer. It is shown that the use of our new data on H2O absorption line parameters improves the agreement between the model and measured atmospheric spectra.

The effect of the partial substitution of M = Ti, V, Cr, Zr, and Nb for Fe in the Pr2Fe17 and Tm2Fe17 alloys on their structural, magnetic, and magnetocaloric properties have been studied using magnetic measurements, X-ray, and neutron diffraction. The character of substitution of Ti, V, Cr, Zr, and Nb atoms for Fe atoms, along with the differences in atomic radii of these elements, substantially affects variations of the lattice parameters and Curie temperatures of the Tm2Fe17 – xMx and Pr2Fe17 – xMx alloys. The Curie temperature of all the substituted alloys increases; the rate of the increase in the Curie temperature of the Tm2Fe17 – xMx alloys is twice that of the Pr2Fe17 – xMx alloys. The magnetic moment of iron atoms MFe and the magnetocaloric effect –ΔSM decrease for the substituted Tm2Fe17 – xMx and Pr2Fe17 – xMx alloys and become close in the case of all M.

Работа посвящена проблеме синтеза и изучения структуры и свойств полимерных кальций-фосфатных биополимерных суспензий, получению на их основе пленочных образцов с лекарственными веществами и изучению кинетики их высвобождения из полимерной матрицы. Синтез композиций осуществляли с помощью метода механоакустической активации. Применение техники механоакустической активации, ультразвукового диспергирования позволяют проводить синтез кальций-фосфатных соединений в водных средах и модифицировать синтезированные продукты лекарствами, биоактивными веществами и формировать биокомпозиции для изготовления костных имплантатов. Ключевые слова: механоакустическая активация, кальций-фосфатные соединения, биополимерные композиты, гидроксиапатит, порфирины.

The oxidation resistance of detonation spraying coatings of the FeAlCr/Al2O3 powder fabricated by mechanically assisted self-propagating high-temperature synthesis using aluminothermic reactions of oxide reduction is investigated. The powder has a sufficiently homogeneous composite structure consisting of chromium-alloyed ordered B2-FeAl and fine inclusions of α-Cr2O3 and α-Al2O3. The detonation coatings sprayed on stainless steel substrates have a typical layered structure without cracks and spalling. The coating thickness is 250–300 μm, and microhardness is in a range of 5.9–6.1 GPa. Coatings of the synthesized powder mainly inherit its structure and phase composition, although certain aluminum and chromium oxidation occurs when spraying. The features of the cyclic and isothermal oxidation of coatings in air in a temperature range of 900–1000°C are studied. It is established that the oxidation resistance of detonation coatings of the synthesized powder after oxidation in air for 48 h at 950°C is close that of coatings formed from the FeAl‒FexAly powder with an aluminum content of 45 wt %. At the same time, the linear thermal expansion coefficient (LTEC) of FeAlCr/Al2O3 coatings is closer to the LTEC of the base material, while their creep resistance is higher when compared the latter due to the presence of fine refractory oxide inclusions. It is assumed that α-Cr, Cr2O3, and numerous fine alumina inclusions present in the synthesized powder (and which form when spraying) accelerate the protective film, formation suppressing hematite nucleation and growth at early oxidation stages at temperatures up to 950°C.

The H2O absorption lines broadened by air pressure were recorded using Bruker IFS 125 HR Fourier spectrometer in the 5900-6100 cm–1 spectral region. The intensities, broadening and shift coefficients of H2O absorption lines were retrieved for lineshape profile taking into account a dependence of the broadening on collision molecules speed. The atmospheric transmission was calculated with use of H2O line parameters from the HITRAN spectroscopic database and our data. A comparison with the atmospheric solar spectra measured using a ground-based Fourier spectrometer was carried out.

Structure and properties of detonation gun sprayed (DS) coatings from the synthesized FeAlSi/Al2O3 powder have been investigated. The powder was manufactured through a mechanically assisted self-propagating high-temperature synthesis route. A small addition of nanosized SiO2 particles to the reaction mixture for the synthesis of FeAl-FeAl2 eutectoid refines the thickness of B2-FeAl lamellar grains in the synthesized powder. Silicon arisen from the aluminothermic reduction of SiO2 during the synthesis is preferentially located in the B2-phase. High-quality coatings with porosity less than 1 vol% and nanocomposite structure have been obtained from the synthesized powder using a computer-aided ‘Perun-S’ detonation gun complex. Phase composition of the coatings includes B2-FeAl, hercinite FeAl2O4, FeAl2, A2-Fe-based solid-solution, Al2O3, and probably complex Fe2.95Si0.05O4 oxide. It is formation of nanocomposite structure with the mean crystallite size of main components in the range of ≈9–15 nm that seems to be responsible for the lower microhardness of the coatings from the FeAlSi/Al2O3 powder than that of the basic Fe-Al eutectoid composition. As-sprayed coatings from the synthesized FeAlSi/Al2O3 powder demonstrate good room and elevated temperature erosion behavior. Oxide dominated erosion with mixed brittle-ductile wear behavior is thought to occur in the coatings at 550 °C. The proposed powder modification is found to be beneficial for the oxidation resistance of DS coatings in air at 950 °C. Promoting of alumina formation during oxidation and the corresponding decline in Fe2O3 content in the oxide scale are considered as the main reasons for the slower oxidation kinetics of the FeAlSi/Al2O3 coatings as compared with those of the basic Fe-Al eutectoid composition.

Hydroxyapatite was synthesized in conditions of mechanoacoustic treatment of an aqueous reaction mixture consisting of ammonium hydrogen phosphate and calcium nitrate using a commercially available rotary pulsation apparatus. Mechanoacoustic treatment of the reaction mixture was found to lead to the formation of nanosized hydroxyapatite particles with a predominant mean diameter of about 20 nm. Purification of technical hydroxyapatite to remove traces of ammonium nitrate by thermal processing at 350°C is proposed. The crystalline phase of hydroxyapatite was found not to be dominant in the structure. The porosity of hydroxyapatite amounted to about 75% with a mean pore diameter of 2.8 × 103 nm. Thermal processing of hydroxyapatite in aqueous medium was found to yield a paste-like form. Hydroxyapatite paste had no cytotoxicity and did not prevent cell adhesion, though it almost completely inhibited cell spreading.

The GdTi0.05Fe0.95-xMnxSi, х = 0–0.95 intermetallic compounds with a tetragonal crystal structure of the CeFeSi type (space group P4/nmm, N 129, tP6) have been studied. The lattice parameter c and the Curie temperature TC increase quickly, whereas the lattice parameter a is almost unchanged in the system when the content of Mn increases. The saturation magnetization, magnetocaloric effect MCE and refrigerant capacity RC change non-monotonically with a dip at intermediate compositions that is presumably due to the canted ferrimagnetic structure of these compounds. The MCE and RC vary in a field changing to 17 kOe within the small ranges of 1.6–2.7 J/kgK and 60–117 J/kg around TC, respectively, while TC changes in a wide range around the room temperature from 160 to 360 K.

The GdFe1-xTixSi (x = 0–0.2) intermetallic compounds have been studied. They crystallize into the tetragonal CeFeSi (P4/nmm)–type structure. With increasing Ti content, the Curie temperature TC and the lattice parameter c increase quickly for x = 0–0.1 and then, more moderate because of the solubility limit, whereas the saturation magnetization at 4 K and the lattice parameter a remain almost unchanged. The theoretical DFT + U calculations showed that the growth of Ti content affects the electronic structure of GdFe1-xTixSi by significantly increasing the density of electron states at the Fermi level N(EF). At the same time, the total magnetic moment does not change because both Fe and Ti are non-magnetic in these intermetallic compounds. The growth of the density of electron states near the Fermi level is accompanied by the rapid growth of TC in the GdFe1-xTixSi system.

The behavior of detonation and plasma coatings in conditions of dry friction against titanium alloy OT-4 and stainless steel 07Kh16N6 has been studied. The detonation coatings show significantly better tribological properties than the plasma coatings. This is probably due to the presence of aluminum and titanium nitrides possessing high wear resistance in the detonation coatings. Oxidation of the plasma and detonation coatings at a temperature of 900°C in air has been examined. The detonation and plasma coatings exhibit greater oxidation resistance than uncoated titanium alloy VT-16.

The GdFe1-x Ti x Si, x=0-0.2 intermetallic compounds with a tetragonal crystal structure of the CeFeSi (P4/nmm)-type have been studied. It was obtained that the lattice parameter c and the Curie temperature increase quickly, whereas the lattice parameter a is almost unchanged in the system with increasing of Ti content. The GdFeSi compound is easily magnetized along the [001] axis, the field of magnetic anisotropy equals to ~3.8 kOe at T = 90 K. The saturation magnetization does not change in the GdFe1-x Ti x Si system.

The paper examines the phase formation of detonation coatings sprayed from mechanically alloyed Ti–50 Al–25 B powder. It is shown that coatings with different phase compositions and functional properties can be consolidated from this activated powder by varying process conditions (including gas composition during detonation spraying). Three types of composite coatings with different structures are obtained: TiB and TiB2 inclusions are distributed in an intermetallic matrix (Al3Ti, γ-TiAl); inclusions of oxides and oxynitrides are additionally present in the same structure; inclusions of borides, Al, and Ti are distributed in a mixture of intermetallic and nitride (TiN, AlN) phases.

A new composition for electrovacuum lead glass with a 20 wt. % PbO has been synthesized. The system of loading the charge and glass scrap into a furnace and a new system of tube shaping are described. The effect of the moisture content of the charge and the temperature on volatilization of PbO, Na2O, and K2O is investigated. It is shown that an artificially formed protective layer on the surfaces of discharge channels considerably reduces the volatilization of PbO, Na2O, and K2O from the liquid glass. Practical recommendations are presented.

Using synchrotron-based in situ X-ray diffraction, the structural changes of LiCoO 2 , LiCo 0.5 Ni 0.5 O 2 , and LiNi 0.65 Co 0.25 Mg 0.05 Ti 0.05 O 2 cathode materials during charge in the voltage range of 3.5 to 5.2 V have been studied. When a LiCoO 2 cathode was charged above 4.5 V, a new intermediate phase O1a was observed, before the terminal phase O1 was formed around 4.8 V. In the X-ray diffraction spectra for LiCo 0.5 Ni 0.5 O 2 and LiNi 0.65 Co 0.25 Mg 0.05 Ti 0.05 O 2 cathode materials, Bragg peaks representing the O1 structure were also observed. The amounts of O1 structure formed at the end of charge (5.2 V for LiNi 0.65 Co 0.25 Mg 0.05 Ti 0.05 O 2 and 5.0 V for LiCo 0.5 Ni 0.5 O 2 ) were increased with increasing Co content.

A Synchrotron x-ray source was used for In Situ x-ray diffraction studies during charge on a new LiMg{sub 0.125}Ti{sub 0.125}Ni{sub 0.75} cathode material synthesized by FMC Corp. It had been demonstrated by Gao that this new material has superior thermal stability than LiNiO{sub 2} and LiCo{sub 0.2}Ni{sub 0.8}O{sub 2} at over-charged state. In this current paper, studies on the relationship between the structural changes and thermal stability at over-charged state for these materials are presented. For the first time, the thermal stability of these materials are related to their structural changes during charge, especially to the formation and lattice constant change of a hexagonal phase (H3). The spectral evidence support the hypothesis that the improvement of thermal stability is obtained by suppressing the formation of H3 phase and reducing the shrinkage of its lattice constant c when charged above 4.3 V.

A new class of materials has been synthesized. The compound showed a reversible capacity of and stable cycling was demonstrated. Differential scanning calorimetry studies showed much improved thermal stability of these materials in their totally charged states in contact with electrolyte. The exothermic peak at in a charged electrode containing was drastically reduced asx increases in . No exotherm was observed below for in its totally charged state. We believe that the use of these materials will improve the overall safety of batteries. ©1998 The Electrochemical Society