Pluripotential cephalosporin antibiotics of different generations active against Gram-negative bacteria are used when treating urinary tract infections, mild and moderate pyelonephritis, acute otitis in children, etc. Rapid determination of cephalosporin antibiotics in the biological fluids is important to evaluate physiological and biochemical processes resulting from their metabolism in a human organism. Planar potentiometric sensors of different types — unmodified and modified with polyaniline (0.3 – 1%), NiZnFeO nanoparticles, and their binary mixes — are developed on the basis of associates of tetradecylammonium (TDA) with complex compounds silver (I) — β-lactam [Ag (I) – (β-lac)₂] which are sensitive to some cephalosporin antibiotics, i.e., cefazoline (Cef), cefuroksime (Cefur) and ceftriaksone (Ceftr). In the sensors of type I, electrode-active components (EAC) and modifiers were added to carbon-containing ink, whereas in type II sensors the polyvinylchloride plasticized unmodified and modified membranes based on [Ag₂(Ceftr)₂]₂ · 2TDA were used. Electroanalytic and operational characteristics of unmodified and modified planar sensors in aqueous solutions of cefazoline, cefuroxime, ceftriaxone and against the background of oral fluid were estimated. It is shown that introduction of the modifiers into sensor membranes leads to stabilization of their potential, increases angular coefficients of electrode functions, decreases the antibiotic detection limit to 1.7 Ч 10^–5 M, reduces the response time and potential drift. Nanoparticles of NiZnFeO appeared to be the most effective modifier. For the sensors of type II linearity of electrode functions is observed in the range of ceftriaxone concentrations of 3.1 Ч 10^–5 – 0.1 Ч 10^–1 M. Depending on the content of the electrode active components in the membrane phase of the unmodified planar sensors, the values of the angular coefficients of the electrode functions vary within 25 – 27 mV/pC and correspond to the values of the non-static value for doubly-charged ions. The linearity intervals of sensor electrode functions are identical at all EAC concentrations under study; as Ceas increases, potential drift and response time decreases. The developed planar sensors were used for determination of cephalosporin antibiotics in model aqueous solutions, medicinal preparations and oral fluid.

The possibility of improving the HPLC-UV determination of 1, 1-dimethylhydrazine (unsymmetrical dimethylhydrazine, UDMH) with preliminary derivatization with 2-nitrobenzaldehyde (2NBA) and 4-nitrobenzaldehyde (4NBA) in an aqueous medium when using micellar catalysis of the reaction to obtain the derivatives is studied. Conditions of UDMH derivatization (pH, concentrations of the reagent and surfactant (SAS), temperature and reaction time) were optimized. It is shown that complete derivatization occurs at room temperature during 45 and 30 min (for 2NBA and 4NBA, respectively) at pH 9 in the presence of 87 mM sodium dodecyl sulfate (SDS) and the excess content of the reagents. Ion chromatography was used to prove the quantitative yields under conditions of derivatization by the absence of UDMH in the reaction mixture. Micellar catalysis provides the completeness of derivatization carried out under milder conditions and in the region of low UDMH concentrations thus expanding the linear range of UDMH determination in water. ZORBAX Eclipse Plus C18 column (150 × 3.0 mm, 3.5 μm) was used for separation of the components. A mixture of acetonitrile and 10 mM ammonia buffer solution pH 7 (50/50 vol.%) at a flow rate of 0.7 ml/min in isocratic mode was used as a mobile phase. Detection of dimethylhydrazines (2NBA and 4NBA) was performed at 308 and 394 nm, respectively. The obtained detection limits of UDMH (S/N = 3) were 3 and 1.5 μg/L for 2NBA and 4NBA, respectively. Duration of chromatographic analysis was 15 min. The developed technique of water analysis provides simple, sensitive and reproducible HPLC-UV determination of UDMH in a concentration range of 5 – 1000 μg/L without additional preconcentration.

Expansion of the works on the synthesis and study of the structure of new intercalation compounds based on molybdenum disulfide (MD)with various organic molecules inclusions in the layered structures, entails the necessity of developing methods for rapid analysis of those compounds for molybdenum content. We developed a rapid method of RF analysis of such compounds using in bulk method in the range of 28 – 50% Mo content. Analytical signals were measured for MoKα line on a VRA-30 spectrometer («Karl Zeiss», Jena Germany, X-ray tube with Rh-anode operated in the mode of 35 kV, 15 mA). The molybdenum content is calculated using the derived constraint equation, the error of determination is ±2.5% Mo (abs.). In contrast to the traditional methods of external standard method with dilution used in the laboratory practice, the proposed method provides a satisfactory accuracy and reduces the duration of analysis from ~100 to ~20 min, the sample material being kept safe for further studies. Correctness of the method was confirmed for the batch of compounds by comparison of the obtained results and the data of XRF analysis with the dilution procedure.

Heat treatment (HT) is one of the main and most important stages of the technological cycle of manufacturing metal products. Residual stresses (RS) arising in metals upon their heat treatment significantly affect the service life of the products. The goal of the study is developing a technique for non-destructive acoustic testing of the residual stresses in steel samples. The method is based on the phenomenon of acoustoelasticity, i.e., the dependence of the acoustic characteristics on the parameters of the environment under study. The fields of residual stresses in rectangular samples made of die steel 5KhNM were formed using various HT modes, including cooling both in traditional media (water, oil, air) and using a water-air mixture (WAM). Control of the ratio of water-air parameters as well as the direction of the WAM flow provided the desired cooling rate and locality of the process. It is shown that the level of residual stresses decreases with the distance from the cooling plane, the microstructure and elastic characteristics of the material also change. The effect of cooling on the formation of temperature fields and the value of residual stresses was analyzed using computer simulation (CAE ANSYS program). The values of the characteristics of 5KhNM steel formed a set of input parameters in simulation. The simulation results proved the experimental data. Acoustic measurements carried out on the measuring and computing complex «ASTRON», provided determination of the velocities of elastic (longitudinal and transverse) waves and the elastic moduli of the material under study. The RS values obtained by the acoustic method were compared with the data obtained by the X-ray method. It is shown that the differences between the values measured by acoustic and X-ray methods do not exceed 10%. The results can be used in a production environment when measuring the residual stresses by the acoustic method in large-sized dies made of 5KhNM steel.

A comparative study of orientation distribution functions (ODF) calculated from direct pole figures (DPF) is carried out using a superposition of a large number of positive standard Gaussian normal distributions with the same scattering (Texxor program) and the method of arbitrary defined cells (ADC) (LaboTex program) to identify the advantages and shortcomings of each method. The comparison was carried out for the Santa Fee reference orientation (the previously calculated total PPF were used as the experimental PPF) and the measured incomplete PPF characterizing the recrystallization textures of 6016 aluminum alloy with a high degree of sharpness. The RP-factor was used as a criterion for evaluating the calculation errors for both programs: the difference between the intensities of the experimental and calculated PPFs averaged over each and all measured PPFs and referred to the corresponding experimental values on the pole figure. The values of the RP-factors depend on the method of the ODF reconstructing and the experimental errors of the measured pole figures of the materials under study. It is shown that the values of RP(0.5)-factor (normalized intensities used in the calculation, ≥0.5) for Santa Fee are 0.3 (Texxor) and 2.6 % (LaboTex) and the corresponding maximum values of the orientational density of ODF differ insignificantly (5.1 and 4.5, respectively). However, for measured incomplete PPF of the recrystallization texture of the aluminum alloy, they differ significantly (61.8 and 95.9), and the RP(0.5)-factor increases to 12.6 and 30.5%, respectively. Since the method of superposition of normal distributions provides a lower value of the RP(0.5)-factor compared to the ADC method, the ODF reconstruction using the Texxor program is preferable compared to LaboTex.

Titanium alloys are widely used as materials for the elements of nuclear power plants, which are subject to high reliability requirements. The goal of the study is to develop X-ray diffraction analysis of the phase composition of α- and near-α-titanium alloys. Surface treatment of the samples of titanium alloys PT-3V, PT-7M and VT1-0 was carried out by mechanical, electrochemical polishing and chemical etching. It is shown that PT-3V and PT-7M alloys are characterized by a mixed structure consisting of α- and α’-phases with precipitation of submicron particles of the β-phase along the grain boundaries. The results of X-ray diffraction analysis of the samples obtained on an X-ray diffractometer Shimadzu XRD-7000 (CuKα radiation) were compared with the data of metallography and electron microscopy. It is shown that the results of X-ray diffraction analysis strongly depend on the method, quality and duration of the surface treatment of the samples. Electrochemical polishing and acid treatment reduce the width of diffraction peaks and lead to a more pronounced manifestation of their «fine» structure thus demonstrating the presence of at least two crystalline phases in the alloys. «Splitting» of the main X-ray peaks of titanium is a consequence of the fine structure of primary X-ray radiation (Kα_1,2-doublet). Presence of «fine» structure of X-ray peaks and correlation between the intensities of different peaks appears to depend essentially on the mode and quality of surface treatment of the titanium alloy thus reducing the reliability of quantitative analysis of the phase composition of titanium alloys without verification of the results by direct methods of studying alloy structure.

We propose a new method for studying the effect of low-cycle fatigue on the evolution of the fracture mechanics parameters in conditions of loading plane specimens with stress concentrators. Three programs of loading with a constant value of the stress range and different values of the stress ratio, as well as two programs with a constant value of the stress ratio but different stress ranges are considered. One program is common for both cases. All the programs include uniaxial tension-compression. Each program was implemented by testing a batch of the same specimens from seven to nine in each. One specimen from each batch was assigned to assess the durability. The other specimens were brought to various stages of low-cycle fatigue in each program. Experimental data were obtained for cracks of different length which were modeled by a sequence of three narrow notches launched from a through hole in a rectangular specimen. Each notch was exposed to constant external load of the same level. The deformation response to a small increment in the notch length at a constant external load was measured at different stages of low-cycle fatigue using electronic speckle pattern interferometry. The interference fringe patterns used as initial experimental data provided determination of the tangential components of in-plane displacements directly on the notch sides and the values of notch opening were thus determined from the results of direct measurements. The transition from measured displacement components to the values of the stress intensity factor and T-stress was performed using the relationships of a modified version of the crack compliance method based on Williams formulation. Distributions of the fracture mechanics parameters along the notches were obtained at various stages of cyclic loading. The dependences of the crack mouth opening displacement, the stress intensity factor and the T-stress on the number of loading cycles are constructed for the notches of a fixed length at different stages of low-cycle fatigue. It is shown that experimental distributions of the stress intensity factor values over the life time practically coincide for all four combinations of the loading cycle parameters.

Steel-aluminum composite materials are widely used in technology due to perfect wedding of their weight efficiency and high mechanical properties. This is the reason for their wide application in the aerospace industry for manufacturing case-type parts of rockets, fuel tanks and elements of aviation armor. The goal of the study is analysis of the crack resistance and the mechanism of fracture of aluminum-steel composite material (20 vol.%) with a density of 2.85 g/cm^3. The matrix component of the material was obtained using a finely dispersed aluminum powder PAP-2. The reinforcing component was made of steel meshes woven from austenitic steel cable (08Kh17N13M2). The transverse bending strength of the obtained material (550 – 600 MPa) was calculated from the maximum load corresponding to the first jump (onset) of the crack nucleating in the matrix. The crack resistance of the composite material at the stage of fracture initiation (estimated using K_1c parameter) varied from 15 to 30 MPa · m^1/2. The crack resistance of the composite at the stage of fracture development was described using the specific effective fracture work γ_F ranged from 2 × 10⁴ to 8 × 10⁴ J/m². The latter parameter exceeds by the order of magnitude the value γ_F determined for steel St3, aluminum alloy D16T, and titanium alloy VT-5. The high value of γ_F (which is an advantage of the obtained composite) is attributed to high-energy-consuming mechanism of the material fracture provided by the increased energy consumption for the destruction of the bridges between the matrix aluminum layers by cutting them off with a cable resulting from the shear stresses, for overcoming the friction forces when pulling cable out of the matrix, and for shifting layered packets formed by diffusion-bonded aluminum scaly particles inside the matrix. The properties of the obtained steel-aluminum composite provide the expediency of using the material for lightweight structural elements operated under mechanical loading.

Tensile stresses present in the pipe steels exposed to corrosive environment can result in the corrosion cracking of the pipe material. The standard procedure used for assessing the susceptibility of steels to stress corrosion cracking (for about 720 h) often does not fully provide insight into the characteristics of the material. The goal of the study is developing of a more rapid test procedure which can provide a reliable and complete information about the material placed in a corrosive environment under stress. Accelerated test for stress corrosion cracking of pipe steels with a relative strain rate of ~10^–6 sec^–1 is proposed. The results of testing two materials at different deformation rates placed in different corrosive environments are presented. The tensile diagrams of the specimens tested in air and in corrosive environments containing hydrogen sulfide and carbon dioxide, as well as the measurement of the relative elongation and relative contraction of fractured specimens, were used to determine a degree of the susceptibility of the pipe steels which differ in the strength characteristics to stress corrosion cracking. It is shown that the degree of susceptibility of steel to stress corrosion cracking depends on the characteristics of the corrosive environment and the strength of the pipe steel. Tests under low rate of loading compared to tests with static load of the specimens revealed reduced duration of analysis from 720 – 1000 to 25 – 100 h.