A new membrane ion-selective electrode (ISE) based on the use of the diclofenac-toluidine blue ion associate (IA) as an electrode substance (EAS) is developed. It is shown that the optimal concentration of IA in the PVC membrane is 5 – 11%. The effect of the plasticizer content on the linearity and steepness of the electrode function, as well as on the lower limit of diclofenac ion determination is studied. The best ratio of a plasticizer to PVC is (1.0 – 1.5):1. The content of the plasticizer is obviously related to the electrode lifetime which is mainly determined by the frequency of usage being 7.0 – 7.5 months on the average. The best sensor characteristics were obtained using the following composition: ion associate — 7%, dibutyl phthalate — 56%, PVC — 37%. The electrochemical sensor has a linear dynamic range of 5.0 Ч 10^–4 – 5.0 Ч 10^–2 M, electrode slope of 46.0 mV/pc with a lower detection limit of 3.2 Ч 10^–5 M, and response time <15 sec. The low-cost sensor is easy to use, exhibits fast response, wide range of the electrode function linearity, high selectivity to diclofenac and can be used for at least seven weeks. The new method of diclofenac determination is developed and tested on model solutions and pharmaceuticals.

Flame spectrophotometry is one of the main methods for determining alkali and alkaline earth metals in solutions. Chemical analysis by the flame photometric method have become of great importance for estimation of trace elements content and for work on small quantities of sample. The most important disadvantages of flame spectrophotometry are different types of interference (spectral, chemical, and physical). The paper considers mainly the physical interference which directly relates to the state of the sample itself and includes solution temperature, viscosity, surface tension, and vapor pressure. These effects are interdependent and not easily isolated for study. The addition of a substance increases the viscosity of the solution, which affects aerosol formation, transport, droplet size distribution, evaporation rate and flame temperature. All that leads to a decrease in the intensity of light emission. In the present article, the effect of phenylalanine on the sodium determination by the flame photometric method in the field of dilute solutions was studied. A decrease in the photocurrent emission of sodium in its joint determination with phenylalanine was found. The main reason is the increase in viscosity. It leads to a reduction in the spraying rate in the analyzer and a diminution in the analytical response of the device. The systematic type of errors in determining the concentration of sodium in the presence of phenylalanine is proved.

The evolutionary development of structural heat-resistant superalloys has led to creation of high-temperature niobium-silicon based natural composite materials (CM) which are promising for manufacturing of aircraft gas turbine engine blades with an operating temperature of up to 1350°C. To impart the necessary properties (heat resistance, heat resistance, creep resistance, fracture toughness, manufacturability, etc.) CM are doped with modifiers, e.g., B, Ge, Sn, Zr. When using the technology of mechanical alloying for production of niobium-silicon based composites Fe and Ni can enter the material as technical impurities. The quality of materials is the first concern in the aerospace industry. Accurate determination the matrix, alloying and impurity elements in the CM composition is necessary for quality control of the semi-products and off-the-shelf CM. We improved the method of ICP AES with microwave sample preparation for determination of the chemical composition of niobium-silicon based composite materials. The analytical lines of B, Ge, Sn, Zr, Fe, and Ni free of significant spectral overlap are used. The range of the determinable contents (wt.%) is: Nb — 40 – 80; B, Ge, Zr — 1 – 5; Sn — 1 – 2.5; Fe — 0.01 – 10; Ni — 0.01 – 5. To evaluate the metrological characteristics of the method, model solutions similar in composition to the composites analyzed, prepared from certified solutions of the ions, were used as reference samples. State standard reference samples of ferroniobium and titanium alloys similar in composition to Nb – Si based CM were used to verify the accuracy of the technique in spiked tests. The repeatability and intermediate precision indices did not exceed 2 and 4 %rel., respectively, for all the elements studied.

Three-dimensional matrices of biodegradable polymers are promising materials for regenerative medicine. They are widely used in restoring the integrity and functions of tissues and organs using bio-artificial tissue engineering structures. We present the results of studying the structure of porous bioresorbable polymer matrices for tissue engineering using X-ray microtomography. Samples were obtained by supercritical fluid plasticization of D,L-polylactide with subsequent foaming in cylindrical molds. The tomographic method makes it possible to construct a three-dimensional voxel model of the object under study and gain apart from the estimate on the integral matrix porosity (characteristic data obtained by traditional sorption procedures) additional information about the size and spatial distribution of pores thus providing a possibility of optimization of the process parameters for production of polylactide matrices required for specific biomedical applications of architectonics, as well as forecasting the processes of their bioresorption in enzymatic media. The experiments were carried out on a laboratory microtomograph (Mo anode, the scan time of the sample is 120 min, the detector pixel size is 9 μm). Tomographic reconstruction was performed by algebraic method. The binarization procedure required for calculation of the structural characteristics of studied matrices was implemented by the method with the choice of a global threshold. Calculations of the porosity and homogeneity of the porosity distribution in the bulk, as well as estimation of the specific surface area of pores revealed the isotropy of the spatial structure of polylactide matrices.

Powder materials are widely used in the manufacture of electrochemical elements of thermal chemical sources of current. Electrochemical behavior of the powders depends on the shape and size of their particles. The results of the study of the microstructure and particles of the powders of vanadium (III), (V) oxides and lithium aluminate obtained by transmission electron and atomic force microscopy, X-ray diffraction and gas adsorption analyses are presented. It is found that the sizes of vanadium (III) and vanadium (V) oxide particles range within 70 – 600 and 40 – 350 nm, respectively. The size of the coherent-scattering regions of the vanadium oxide particles lies in the lower range limit which can be attributed to small size of the structural elements (crystallites). An average volumetric-surface diameter calculated on the basis of the surface specific area is close to the upper range limit which can be explained by the partial agglomeration of the powder particles. Unlike the vanadium oxide particles, the range of the particle size distribution of the lithium aluminate powder is narrower — 50 – 110 nm. The values of crystallite sizes are close to the maximum of the particle size distribution. Microstructural analysis showed that the particles in the samples of vanadium oxides have a rounded (V₂O₃) or elongated (V₂O₅) shape; whereas the particles of lithium aluminate powder exhibit lamellar structure. At the same time, for different batches of the same material, the particle size distribution is similar, which indicates the reproducibility of the technologies for their manufacture. The data obtained can be used to control the constancy of the particle size distribution of powder materials.

Structural degradation of the material upon long-term thermal and force impacts is a complex process which includes migration of the grain boundaries, diffusion of the active elements of the external and technological environment, hydrogen embrittlement, aging, grain boundary corrosion and other mechanisms. Application of the fractal and multifractal formalism to the description of microstructures opens up wide opportunities for quantitative assessment of the structural arrangement of the material, clarifies and reveals new aspects of the known mechanisms of structural transformations. Multifractal parameterization allows us to study the processes of structural degradation from the images of microstructures and identify structural changes that are hardly distinguishable visually. Any quantitative structural indicator can be used to calculate the multifractal spectra of the microstructure, but the most preferable is that provides the maximum range of variation in the numerical values of the multifractal components. The results of studying structural degradation of steel 15Kh5M upon continuous duty are presented. It is shown that structural degradation of steel during operation under high temperatures and stresses is accompanied by enlargement of the microstructural objects, broadening of the grain boundaries and allocation of the dispersed particles which are represented as point objects in the images. The processes of structural degradation lead to an increase in the range of changes in the components of the multifractal spectra. High values of complex indicators of structural arrangement indicate to an increase in heterogeneity and randomness at the micro-scale level, but at the same time, to manifestation of the ordered combinations of individual submicrostructures. Those structural transformations adapt the material to external impacts and provide the highest reliability and fracture resistance of the material.

Survivability, service life and operational safety of the engineering structures are determined by their damage rate which is mainly regulated by the presence and development of the crack-like defects in the material. Kinetic dependences describing the development of multidirectional semi-elliptic surface cracks with allowance for the anisotropy of the material properties are proposed proceeding from experimental data and numerical solutions. The obtained results are required in studying kinematic problems in nonlinear mechanics of a continuous anisotropic medium. Refining parametric equations for elastoplastic deformation anisotropy are proposed. Functional dependences of the parameters of the kinetic diagrams of low-cycle fracture on the mechanical properties of the material are presented for a wide class of welded joints of austenite stainless cyclically stable steels (12Kh18N10T). The processes of developing inclined semi-elliptic surface cracks in the continuums of welded joints under non-linear boundary loading conditions are studied. We have carried out combined computational, experimental and numerical studies of the stress-strain state in the vicinity of the contour of stationary and growing surface semi-elliptic cracks randomly oriented in space under elastoplastic nominal cyclic loading taking into account the anisotropy of the material properties. The functional distribution of the inhomogeneity parameter of the mechanical properties of the material, which affects accumulation of the local plastic strains and direction of developing the elastoplastic fracture is obtained and presented in the form of the kinetic equation of nonlinear fracture mechanics. Comparison of the experimental results and numerical calculations of the stress-strain state along the contour of the cracks under study in nonlinear boundary loading conditions revealed a good agreement between the intensities of relative elastoplastic deformations at their surface points with allowance for the deformation anisotropy. Calculations of the elastoplastic fracture resistance of the critical elements of the equipment with allowance for considered factors of nonlinear fracture mechanics and heterogeneity of the properties can improve the accuracy of evaluation of their strength, service life and survivability.

Experimental study of the shape memory polymer composite is carried out as a part of scientific and technological work aimed at development of the new promising reflectors for space antenna. The studied material consists of three-layered carbon biaxial fabric St 12073 impregnated with a polyurethane-based Diaplex MP5510 polymer matrix. This material is intended for manufacturing a frame used in the construction of a precise composite reflector of space antenna. When opening the reflector to the transport position, the rim activated by heating recovers a previously specified shape thus increasing the rigidity of the reflector at the periphery and enhancing the accuracy of the reflecting surface. To study the functional and mechanical properties of the rim material in manufacturing and operating conditions, experimental tests were carried out on the samples with different schemes of reinforcement: [0₃], [0/±60] and [0/±45]. The main goal of the study is to determine the degree and rate of the shape recovery, reinforcement angles, deformation rate and exposure time in the strained state. The developed test program included several stages. At the first stages, tests were carried out for fixing and restoring the shape upon three-point bending of flat samples at a strain rate of 1, 5, and 10 mm/sec and exposure of the specimens in deformed state for 24, 48, and 96 h. According to the results the material with the reinforcement angles [0₃] was accepted as optimal for the rim design, as it has maximal shape recovery parameters. For the selected material at the final stage of the study, the elastic modulus and tensile strength were determined at operating temperatures –50, +20, and +60°C. The tests showed that the studied polymer composite material has the desired shape memory properties and is promising for the rim manufacturing provided the heat insulation during operation.

The mechanical properties of structural metallic materials are the most important indicators of their quality. Different methods (i.e., the methods of Shore, Brinell, Rockwell, Leeb, Vickers, method of instrumental indentation, and others) are currently used for determination of the hardness — one of the most important mechanical characteristics of structural metal materials. Among them is the method of dynamic indentation first developed at the Institute of Applied Physics of the National Academy of Sciences of Belarus. With the goal of further developing of the method of dynamic indentation, we propose the procedures aimed at increasing the accuracy of assessing the hardness of structural metallic materials: parameters of the contact interaction of the indenter with the sample material (Brinell hardness values) were measured using a dynamic indentation (DI) device; the values of surface and volumetric dynamic hardness were calculated taking into account the characteristics obtained using a DI device; a comparative analysis of hardness estimates obtained by different approaches was carried out. As a result of the comparative analysis of the methods, as well as their experimental testing, it was shown that an increase in the accuracy of hardness assessment can be achieved by using the «energy» approach based on assessing the ratio of the total work to the volume of the recovered indentation upon dynamic indentation of structural metal materials. The use of the «energy» approach provided obtaining the sample standard deviation of the volumetric dynamic hardness values, which, in turn, was significantly lower than the sample standard deviation of the surface dynamic hardness values and data of the dynamic indentation device, which directly affects an increase in the accuracy of hardness estimation during dynamic indentation of structural metal materials. Proceeding from the «energy» approach, a new algorithm for processing the initial signal is proposed when the dynamic hardness is determined using a dynamic indentation device.

We consider the data fitting problem under uncertainty, which is not described by probabilistic laws, but is limited in magnitude and has an interval character, i.e., is expressed by the intervals of possible data values. The most general case is considered when the intervals represent the measurement results both in independent (predictor) variables and in the dependent (criterial) variables. The concepts of weak and strong compatibility of data and parameters of functional dependence are introduced. It is shown that the resulting formulations of problems are reduced to the study and estimation of various solution sets for an interval system of equations constructed from the processed data. We discuss in detail the strong compatibility of the parameters and data, as more practical, more adequate to the reality and possessing better theoretical properties. The estimates of the function parameters, obtained in view of the strong compatibility, have a polynomial computational complexity, are robust, almost always have finite variability, and are also only partially affected by the so-called Demidenko paradox. We also propose a computational technology for solving the problem of constructing a linear functional dependence under interval data uncertainty and take into account the requirement of strong compatibility. It is based on the application of the so-called recognizing functional of the problem solution set — a special mapping, which recognizes, by the sign of the values, whether a point belongs to the solution set and simultaneously provides a quantitative measure of this membership. The properties of the recognizing functional are discussed. The maximum point of this functional is taken as an estimate of the parameters of the functional dependency under construction, which ensures the best compatibility between the parameters and data (or their least discrepancy). Accordingly, the practical implementation of this approach, named «maximum compatibility method», is reduced to the computation of the unconditional maximum of the recognizing functional — a concave non-smooth function. A specific example of solving the data fitting problem for a linear function from measurement data with interval uncertainty is presented.