Inductively coupled plasma mass spectrometry (ICP-MS) is used for separate determination of platinum and palladium on the surface and in the bulk of tin dioxide based nanocomposites. Synthesis of SnO2 matrices was conducted using deposition from the solution and flame spray pyrolysis (FSP). The modifiers were injected by impregnation via the dispersion of the matrix powders in the solutions of precursors in volatile solvents and subsequent evaporation of the solvent. It is shown that palladium is present on the surface of the nanocomposites regardless of the synthesis procedure. As the losses of the modifier after impregnation of SnO₂ synthesized by FSP method were obserbed, we concluded that the properties of the SnO₂ surface depend on the method of obtaining matrix. It was also shown that for the materials obtained by the method of deposition from the solutions 30 - 50% Pt are present on the surface and other 50 - 70% are distributed in the bulk of SnO₂. The use of pyrolysis in the flames makes it possible to increase the content of Pt on the surface up to 80%. The loss of Pt observed in both cases and attributed to the differences in the microstructure of SnO₂ results in the etherification of thin layers of phases of complex composition which affect the processes of superficial diffusion and evaporation. Reproducibility of the results of Pt and Pd determination indicates to a high degree of heterogeneity of the studied materials.

The analytical capabilities of arc atomic emission determination of As, Bi, Sb, Cu, Te in rare earth metals (REM) and their oxides after preparatory group concentration using S,N-containing heterochain polymer sorbent are studied on a high-resolution spectrometer “Grand- Extra” (“WMC-Optoelectron-ics” company, Russia). Sorption kinetics and dependence of the degree of the impurity extraction on the solution acidity are analyzed to specify conditions of sorption concentration. To optimize the procedure of arc atomic emission determination of As, Bi, Sb, Cu, and Te various schemes of their sorption preconcentration and subsequent processing of the resulted concentrate with the addition of a collector at different stages of the sorption process have been considered. Graphite powder is used as a collector in analysis of rare earth oxides due to universality and relative simplicity of the emission spectrum. Conditions of analysis and parameters of the spectrometer that affect the analytical signal (mass and composition of the sample, shape and size of the electrodes, current intensity and generator operation mode, interelectrode spacing, wavelengths of the analytical lines) are chosen. The evaporation curves of the determinable impurities were studied and the exposure time of As, Bi, Sb, Cu, and Te in the resulted sorption concentrate was determined. Correctness of the obtained results was evaluated using standard samples of the composition and in comparisons between methods. The results of the study are used to develop a method of arc chemical-atomic emission analysis of yttrium, gadolinium, neodymium, europium, scandium and their oxides in a concentration range of n x (10^-2 - 10^-5) wt.%.

Development of rapid method of spectral analysis capable of accompanying all the stages of nickel superalloy production is a hot topic of the analytical control of nickel superalloys. To ensure high accuracy of the results obtained by the methods of optical emission spectrometry and X-ray fluorescence spectrometry, reference materials (RM) adequate in composition to the analyzed samples are to be used. The lack of RM for novel grades of modern nickel alloys, entails the necessity of their development and certification. A methodical approach to the development and production of RM of new grades of nickel superalloys is presented. It is shown that production of the corresponding RM for spectral analysis apart from obvious requirement regarding the absence of defects (shells, cracks, nonmetallic inclusions, isolated zones differing in the content of alloying elements and impurities) requires also elimination of the areas of increased microporosity. In this case, the samples are rejected and melted down, the smelting modes of the CO blanks being adjusted if necessary. We have studied the structure and homogeneity of the manufactured RM and determined the certified values of the reference materials for nickel superalloys of the type VZhM, VKNA, etc. The potentiality of using the developed RM for optical emission spectroscopy with spark excitation and X-ray fluorescence analysis are considered. It is shown that optical emission spectroscopic analysis with spark excitation requires RM sets most close in composition to the analyzed samples when plotting a calibration characteristic, whereas when using X-ray fluorescence analysis, combined sets of RM are appropriate for analysis of the alloy grades similar in composition. The metrological characteristics of the reference materials of approved types (certified reference materials) for the spectral analysis developed at FSUE VIAM for the last seven years are presented.

The possibility of using an aqueous stratified system of antipyrine — sulfosalicylic acid — water for the selective isolation of scandium macro- and microquantities for subsequent determination is studied. The proposed extraction system eliminates the usage of toxic organic solvents. The organic phase with a volume of 1.2 to 2.0 ml, resulting from delamination of the aqueous phase containing antipyrine and sulfosalicylic acid is analysed to assess the possibility of using such systems for metal ions extraction. Condition necessary for the formation of such a phase were specified: the ratio of the initial components, their concentration, presence of inorganic salting out agents. The optimum ratio of antipyrine to sulfosalicylic acid is 2:1 at concentrations of 0.6 and 0.3 mol/liter in a volume of the aqueous phase of 10 ml. The obtained phase which consists of antipyrinium sulfosalicylate, free antipyrine and water, quantitatively extracts macro- and microquantities of scandium at pH = 1.54. Macro- and microquantities of yttrium, terbium, lanthanum, ytterbium and gadolinium are not extracted under the aforementioned conditions thus providing selective isolation of scandium from the bases containing yttrium, ytterbium, terbium, lanthanum, and gadolinium.

The effect of crystal anisotropy and defects of the structure formed upon mechanical cyclic deformation and thermal shock on acoustic parameters such as phase velocity, attenuation coefficient, Q-factor of bulk acoustic wave (BAW) has been studied in lanthanum-gallium tantalate (LGT, La₃Ta_0,5Ga_5,5O₁₄) anisotropic piezoelectric single crystals using inner friction (IF) method with multiple piezoelectric vibrator at a frequency of 10⁵ Hz. The anisotropy of the effective elasticity modulus (E), BAW phase velocity (V_p), attenuation coefficient and Q-factor was observed in anisotropic LGT single crystals. It is shown that cyclic deformation of LGT samples under a load of 2.5 kN with the number of load cycles up to 5 x 105 with a cycling frequency of 100 MHz and thermal shock (100 - 120°C) have no effect on the values of the effective elasticity modulus and phase velocity of the longitudinal BAW, respectively: for X-cut — E =111 GPa, V_p = 4250 m/sec; for Z-cut — E = 181 GPa, V_p = 5430 m/sec. The attenuation coefficient of the longitudinal BAW increased by 1.5 - 2 times after cyclic deformation for both X-and Z-cuts, which resulted in a two-fold decrease of the quality factor. Thermal shock has almost no effect on the attenuation coefficient and Q-factor for X-cut samples. For Z-cut samples thermal shock leads to a three-fold increase of the attenuation coefficient and decrease of the Q-factor. Sensitive elements of piezopressure sensors based on langatate should be protected from thermal shock at a temperature above 150°C, and the total number of the mechanical compression cycles of the material should not exceed 5 x 105 cycles at a frequency of 100 - 150 Hz with the loads not exceeding 2.5 kN.

Electric rolling (ER) is one of the ways in which the electromagnetic field and electric current can affect the deformation zone of metallic materials (powder, composite and compact). The results of studying the structure and properties of ER materials: compact metals (copper, aluminum and titanium), powder materials of the system Fe - Cr - Ni, powder compositions containing the particles of boron nitride, glass and graphite (fillers) with a metal matrix of nickel and nichrome are presented. The capabilities of ER with imposition of high density current 10⁸ - 10⁹ A/m² on the hot spot resulting in a significant improvement of the mechanical properties of the studied materials compared to conventional cold rolling are shown. Metallic materials made in the form of tapes were studied on a special installation for electric rolling. The method is based on imposing high-density current through a deformable material between the roll-electrodes at a temperature not exceeding the temperature of the recrystallization onset and assessing the contribution of the impact of high-density current and electrophysical parameters (heat capacity, density, electrical resistivity, and magnetic susceptibility) to an increase in the mechanical properties of materials upon electric rolling. The high density current is shown to increase in the strength of materials and expand the technological capabilities of rolling. New experimental and theoretical data of the study can be used in the developing the technology for producing metallic tape materials.

Qualitative and quantitative estimates of the temperature fields and level of the residual thermal stresses (RTS) in a steel substrate and hard-alloy coating obtained by electropulse technology (EPT) are presented. The estimation was carried out using the finite element method (FEM) and universal COMSOL Multiphysics® software to simulate applied problems. The results of the simulation showed that the higher the rate of mechanical loading, the smaller the depth of heat penetration into the substrate, the residual thermal stresses being localized in the zone of thermal influence near the interaction surface. At the same time, a thin layer of steel cannot cause considerable stresses in the bulk of the hard alloy. The stresses in the steel layer reach the yield point and the layer deforms without formation of large tensile stresses in the hard alloy. A criterion has been obtained that makes it possible to reveal the range of coating application parameters in which the impact of the steel substrate on the formation of residual thermal macro-stresses in the bulk of the hard-alloy coating is minimum. Electropulse equipment has been developed for application of the hard alloy coatings. Standard x-ray sin²Ψ-method (rotation method) is used for experimental evaluation of the macrostresses in the zone of the steel contact with the coating. Studies have shown that both radial and axial stresses are compressive; the maximum absolute values of the stress are observed in the radial direction in the outer layers of the coating, while the axial stresses relax near the free surface. Radial stresses in the outer layers of the coating reach a value of -210 MPa, and axial -110 MPa. The stresses in the coating layers contacting with steel are also characterized by rather high values, of the order of -160 ... -170 MPa. A high level of stress is attributed to the fact that the coating is formed under external pressure. At the same time the compressive stresses are favorable for a hard alloy, since it exhibits high values of the ultimate compression strength.

The results of comprehensive studies of multifactor processes, mechanisms and criteria for fracture at a variation of the crack-like defect state, loading conditions and mechanical properties of structural materials carried out in the 20^th - 21^st centuries are presented on the basis of monographic publications and articles published in the journal “Zavodskaya Laboratoriya. Diagnostika Materialov.” Crack resistance of materials and structures has become a key problem of the material science, technology, design, manufacture and service of structures. Fracture mechanics including estimation of the stress-strain and limiting states in a cracks tip formed a scientific basis of the crack resistance analysis Stress intensity factors (linear fracture mechanics) and strain intensity factors (nonlinear fracture mechanics) are accepted as the basic criteria of those states. The basic computational relations for construction of the fracture diagrammes which link the cracks growth with conditions of a static, cyclic, long-term, dynamic loading are presented. Parameters of computational relations are put into correspondence with the features of fracture processes on nano-, micro-, meso- and macrolevels. Prospects of the research and guidelines of further studing crack resistance are discussed.

A universal energy-intensive micromechanism of periodic splitting-rupture (PSR) is revealed which proceeds at the front of the fatigue cracks in metallic materials, providing their steady growth, forming T-shaped crack tip and striated microrelief of the fracture surface. The PSR micromechanism is caused by a critical (prior to fracture) fragmentated structure formed in the area of the crack front where the material is subjected to multiple and increasing plastic deformation. This universal prefracture structure is a final stage of the evolution of the deformational structures emerged in front of the fatigue crack at the stage of stable crack growth in metallic materials with different initial structural states. This is responsible for universality of PSR micromechanism and fatigue striations. Fatigue striations are the traces of extending crack front with T-shaped tip formed during brittle transverse microsplitting along the overstressed boundaries of critical fragmentated structure. Based on 3D finite element modeling of the stress-strain state in front of the cracks with T-shaped tip, it is established that the value and the location of maximum of normalized in-plain stresses (acting in front of crack tip in the plane of crack along the normal to its front) are close or coincide for the cracks of different configuration and different types of tensile load under condition that splitting in the T-shaped crack tip is considerably less than the crack length. Taking into account the PSR micromechanism and asymptotic stress distribution in front of T-shaped crack tip the physically based mathematical model for steady fatigue crack growth is developed along with the techniques for prediction of steady fatigue crack growth in full-scale components under simple and complex loading cycles.

A method of processing the results of tests for fretting fatigue drawn on the literature, is presented to determine a quantitative measure to be used in assessing the surface wear resistance in conditions of contact cyclic loading. Operation practice and experiments indicate to multiple micro-cracks of different sizes present on the contact surface. An assumption is made regarding the accidental character of the crack birth thus making possible the use of the mathematical statistics to obtain the characteristics treated as the mechanical properties of the crack resistance, which assess the resistance of contact fatigue material. The samples of three steel grades used for railway rail production are studied. The wear resistance is assessed through robust statistical characteristics under the assumption that occurrence of the surface defects is a random process. The loading is carried out in conditions of rolling friction with the balls spinning in the mandrel, thus forming an annular wear pad. As the load on the test rig is considered an analogue of the force action of the wheel on the rail, the wear resistance can become a quantitative measure of the quality of the rail steel. Measurements on each sample were made for three runs. The curves of the density of the defect area distribution on the wear surface of the samples are presented. Quantitative characteristics are proposed to estimate the fretting fatigue resistance of the metal, namely, the average crack area, standard deviation and the variation coefficient. Those characteristics are the parameters of statistical processing of experimental observations of the number and size of the surface cracks that occur under cyclic loading of the metal surface. The degree of significance of the observed damages is discussed to be used as an indicator when comparing different steels in the wear resistance. The results of the experiment made it possible to arrange three studied steels in a series of their fretting corrosion resistance: the Japanese steel has the greatest resistance to contact wear, then Russian steel and then Polish steel that exhibits the least resistance to contact wear.

A new statistical method for response steepest improvement is proposed. This method is based on an initial experiment performed on two-level factorial design and first-order statistical linear model with coded numerical factors and response variables. The factors for the runs of response steepest improvement are estimated from the data of initial experiment and determination of the conditional extremum. Confidence intervals are determined for those factors. The first-order polynomial response function fitted to the data of the initial experiment makes it possible to predict the response of the runs for response steepest improvement. The linear model of the response prediction, as well as the results of the estimation of the parameters of the linear model for the initial experiment and factors for the experiments of the steepest improvement of the response, are used when finding prediction response intervals in these experiments. Kknowledge of the prediction response intervals in the runs of steepest improvement of the response makes it possible to detect the results beyond their limits and to find the limiting values of the factors for which further runs of response steepest improvement become ineffective and a new initial experiment must be carried out.