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The paper presents the results of an experimental study of an optical discharge plasma obtained by absorbing radiation from a pulsed-periodic radiation of a CO2 laser with a pulse repetition rate of 40 kHz and an average power of 1.6 kW. In order to increase the length of the breakdown plasma the laser beam (diameter 25 mm) was focused in the in an argon subsonic flow by a lens with a focal length f = 254 mm. To visualize the process, we used a FASTCAM SA-Z video camera (Type 480K), exposure time (1.0 µs), and shooting speed of up to 200,000 fps. The conditions for registering an optical scheme varied by using a Foucault knife, diaphragms, and light filters in order to develop optimal methods for obtaining data. The experimental results showed that the plasma dynamics has two successive stages: from the high-speed optical discharge propagation with absorption of radiation behind the laser supported detonation (LSD) wave front to the next less speed stage.

The purpose of the work presented is to study the processes of phase formation in mechanically activated Ti + Al powder mixture which was exposed to low doses of gamma radiation. A two-stage treatment of the initial powder mixture of the specified composition was conducted. At the first stage, the mixture was mechanically activated in order to achieve a high quality of contact between the reactants. At the second stage, the mixture was subjected to gamma irradiation in order to form a wide transition zone in the contact area. The irradiated mixture was heated by the external heating source. To study the processes of phase formation, the technique of time-resolved X-Ray diffraction was used. The comparative analysis of intermetallic phases formation sequences for irradiated and non-irradiated mixtures was carried out. It was found that the heterogeneous reactions pathways are significantly different for these cases. The detailed analysis of parallel and consecutives reactions was carried out at various stages of high-temperature synthesis taking into account the structure of the Ti–Al equilibrium diagram. It was found that the most probable mechanism of heterogeneous reaction in unirradiated mixture is the predominant dissolution of titanium with the formation of intermetallic phases TiAl, TiAl3. In the irradiated mixture, on the contrary, the flow of aluminum atoms dominates, which leads to the formation of the only synthesis product of the TiAl composition. In the case of forced cooling of the mixture after thermal explosion (TE), a uniform distribution of reactants is observed in the whole volume of the sample of the irradiated mixture which is similar in composition to the TiAl compound.

There are considered ecologically harmless technologies for nano-structural material obtaining by methods of mechanochemistry with carrying out a reaction of high-temperature synthesis in a metal matrix for the application of the powder material obtained in the course of gas-detonation coating processes which may substitute electroplate chromium coating. As a sputtered powder there was used SVS- mechanocomposite having Ti-C-NiCr in its composition. It is determined that the wear of piston rings with the developed coating is lower by 27%, than in similar rings with an electroplate chromium coating.

We have studied the effect of sintering temperature on the structural and phase transformations of alloys produced by the spark plasma sintering of Ti + 23.5 at % Al + 21 at % Nb powder mixtures at temperatures in the range 1100–1550°C. The sintered alloys have been characterized by X-ray diffraction, scanning electron microscopy, and energy dispersive X-ray spectroscopy (elemental X-ray mapping). The alloys sintered at temperatures of 1100 and 1200°C have been shown to have a nonuniform microstructure. According to electron microscopy results, the alloys consist of grains of the α2 and Nb2Al phases and small precipitates of the O-phase (intermetallic compound Ti2AlNb). In addition, there are particles of unreacted niobium and titanium. The alloys sintered at a temperature of 1300°C have a uniform lamellar structure.

Structural peculiarities of a powder composite mixture on the basis of aluminum and dispersion carbon structures intended for gas-detonation sputtering for an anti-friction purpose are investigated in the paper. As initial materials there was used an aluminum powder, carbon powder, boron carbide powder, powder slurry consisting of fullerenes C60 and ultra-dispersion diamonds in a certain ratio. The powder mixture obtained was subjected to a mechanical activation with the aid of a planetary ball mill of AGO-2S type. According to the results of the morphological analysis it was established that a composite mixture possesses a layer structure characteristic for powder mixtures subjected to a mechanical activation in the course of a long period of time. A mean size of obtained mechano-composite particles makes about 100…150 mkm. An X-ray structural investigation of a composite powder mixture formulations 70% Al+30%C+B4C and 70%Al + 30%C60 (total %) + B4C after mechanical activation revealed that boron carbide contributes well to the amorphization of a composite powder mixture. It is also established that after mechano-activation of the “Al+C+B4C” powder mixture during 4 min carbon transforms to an X-ray amorphous state to which testifies the presence of amorphous “halo” at small angles and carbon peaks disappeared completely. There is no carbon dissolution in aluminum and chemical compounds are not formed.

The structural and phase state of powder samples of compounds Ti3Al and TiAl has been investigated experimentally before and after the action of small doses of gamma irradiation. To study phase and structure parameters, the X-ray diffractometry has been used. It has been established experimentally that after the same conditions of gamma irradiation structural states of these compounds differ. It has been revealed that for compound Ti3Al small doses of gamma irradiation serve stimulators to form radiation-induced states. In the irradiated TiAl sample, a crystal-lattice distortion was observed with the retention of a high crystallinity of the structure and no signs of a special radiation-induced state were revealed.

An in situ synchrotron study of the specific features of the phase formation dynamics in mechanically activated 16 wt% Al + Ti powder composition is described, the high-temperature synthesis being carried out under the condition of high volume inflammation by means of inductive heating. The kinetics of the phase formation were registered with an experimental complex, especially designed, constructed and adjusted for the method of dynamic diffraction analysis in synchrotron radiation beams. It has been experimentally in situ shown that increasing the time of mechanical activation of the initial powder mixture reduces the temperature at which components start to react and the time of realization of the high-temperature synthesis. With the latter set at 1 min of mechanical activation, the temperature of the reaction in the mixture is T = 603°C; at 3 min of mechanical activation, T = 442°C; and at 7 min, T = 359°C. The maximum burning temperatures are: for 1 min of mechanical activation, T max = 1080°C; for 3 min, T max = 1003°C; and for 7 min, T max = 820°C. It was found that formation of both stable compounds Ti3Al, TiAl3, TiAl2, TiAl and metastable phases Ti9Al23, Ti5Al11, Ti2Al5, Ti3Al5 occurs at the stage of primary structure formation, before the system goes to thermal explosion. High-temperature synthesis of a mixture of the studied composition takes place without formation of a liquid phase, in the solid-phase combustion mode. It was found that the increase in the time of mechanical activation of the initial powder mixture contributes to the formation of a product with a dominant content of intermetallic compound Ti3Al. By synthesis of the powder mixture of composition 16 wt% Al + Ti, mechanically activated for 7 min, the content of Ti3Al in the final product was found to be 68%.

At present the development of methods of layer-by-layer and line-by-line synthesis of finished prototypes and functional products made of powder materials furthers introduction of these technologies into different areas of human activities from light to heavy industry and medicine. The research has been carried out to describe how gamma radiation of the Co60radioactive isotope and the mechanical activation makes an impact on the copper powder, as well as the nature of sintering by the layer-by-layer laser synthesis. The changes of the structure and properties of the powder, which generally affects the layer-by-layer laser process of products sintering, have been detected.

As a result of optical and pneumometric measurements is defined the flow shock wave structure that is formed by the optical breakdown, due to focused repetitively pulsed CO2 laser radiation when entering perpendicular to a supersonic (M = 1.36, 1.9) air flow direction. The dynamics of the bow shock formation in front of the energy input area is shown, depending on the frequency of energy impulse sequence. A flow structure is defined in the thermal wake behind pulsing laser plasma as well as wake’s length with low thermal heterogeneity. A three-dimensional configuration of the energy area is defined in accordance with pneumometric and optical measuring results. It is shown that Pitot pressure decreases in thermal wake at a substantially constant static pressure, averaged flow parameters weakly depend on the energy impulse’s frequency in range of 45-150 kHz.

New heterogeneous catalysts for synthesis of a biodiesel fuel, modified with strongly acidic groups, were developed. The catalysts are produced by pyrolysis and subsequent sulfation of fruit kernels and granulated porous copolymers and resins. The structural-sorption and catalytic properties of the materials obtained were studied in the reaction of catalytic re-esterification of rapeseed oil by methanol and ethanol. The conditions in which carbon materials with high content of surface acid groups are obtained were optimized.

Conditions of a static thermal explosion in mechanically activated Ti-C-Ni mixtures are studied. Mechanical activation of the mixtures in a planetary ball mill during 30–180 sec is found to reduce the reaction-initiation temperature by 1000–600°C, as compared with traditional self-propagating high-temperature synthesis. Results of x-ray diffraction analysis and electron microscopy of activated mixtures and thermal explosion products are described. The result of the synthesis is a TiC compound in a solid nickel matrix.

This paper considers the mechanisms of structure formation during gas detonation spraying of coatings of TiAl3 and Ni3Al intermetallic compounds produced under equilibrium and nonequilibrium synthesis conditions. The coating sprayed from TiAl3 has the same phase composition as the initial powder, regardless of the synthesis conditions. During spraying of Ni3Al, the structure of the coating also does not depend on the synthesis conditions and consists of two phases — Ni3Al and NiAl, with the crystal structure varying along the coating thickness. Comparative impact abrasion tests of the coatings showed advantages of TiAl3 coatings over coatings based on Ni3Al and titanium diboride.

The paper provides the comparative measurements of compressive strength of selective laser sintered copper samples. The optimal technological conditions of sintering samples were chosen. Pre-activation of copper powder affects the compression strength of samples because of the changing porosity and bulk density of the powder.

The ionization rate of argon in a relaxation zone behind the shock wave front was measured in stable flow regimes with Mach numbers above 11. Based on an analysis of the electron energy balance equation, it is suggested that high (as compared to the results of calculations) values of the avalanche ionization rate are related to the existence of an additional channel of the energy transfer during the associative ionization of argon atoms.

The state of argon plasma behind the shock wave front was experimentally studied in the flow regimes with Mach numbers M = 11−12. Using the results of simultaneous measurements of the optical emission and absorption at a wavelength of 10.6 μm, the electron temperatures in the relaxation zone and in the equilibrium region are evaluated.

The ionization rates of argon and krypton were measured in a relaxation zone behind the shockwave front for the Mach numbers corresponding to stable flow regimes close to the threshold for development of the flow instability of types I and II. The experimental rates of the avalanche ionization exceed theoretical predictions. It is suggested that the discrepancy is related to the existence of an additional channel for the energy transfer between particles.

An analysis is made of experimental data on the influence of a pulse-periodic optical discharge in a supersonic argon stream on the aerodynamic drag of streamlined objects. The interrelation established between the parameters of the laser radiation and the stream is used to determine the threshold frequency of the laser pulses which determines the transition to quasi-steady-state flow.

1. Chromoalumina and potassiumalumina catalysts for a low-temperature hydrogenation of ethylene show maximum activity after vacuum activation at 800–900°C. 2. The activities of boehmite and bayerite catalysts increase monotonically with an increase in the Cr2O3 content. The activities of catalysts based on hydrargillite and γ-Al2O3 (from boehmite) pass through a maxima at ∿7–9 mole % Cr2O3. 3. Gamma irradiation of boehmite and bayerite prior to impregnation reduces the catalytic activity, rendering the activity vs chromium content relation similar to that observed with γ-Al2O3- and HA-based catalysts. 4. Introduction of as much as 4 mole % K2O reduces the activity of BH-based chromoalumina catalysts, measurement being made after thermal treatment at optimal activation temperature.

1. A study was made of the effects of small additions (0.05–1.0 wt.%) of the iron-group metals upon the sintering of niobium and of some properties of the resultant alloys. 2. The hypothesis is advanced that Fe, Co, and Ni additions activate the sintering of niobium by bringing about localization of the free electrons of the niobium atoms in the 3d states, as a result of which the amount of free energy stored in the system niobium-addition metal diminishes. Nickel — the metal whose 3d level has the highest acceptor capacity — exerts the strongest activating influence.

1. A study was made of the influence of iron-group metal additions on the sinterability of tungsten powder at temperatures of 1000–2000°C. It is shown that the activating effect of these additions increases in the sequence Fe → Co → Ni. 2. It is demonstrated that the method of introducing an addition has no effect on the course of sintering of tungsten powder. 3. An explanation, based on the model of configurational localization of the valence electrons of atoms, is proposed for the mechanism of activated sintering of tungsten.

1. A study was made of the influence of palladium on the sintering of tungsten. It is shown that palladium additions activate the sintering process, the optimum parameters, from the viewpoint of attaining the highest density and strength, being a palladium content of 0.2% and a sintering temperature of 1600° C. 2. The results obtained are analyzed by regarding the sintering process as a process of energetic stabilization of the system being sintered. It is proposed that the activating action of a palladium addition consists in unlocalized electrons being transferred from the palladium atoms to the tungsten atoms. This is accompanied by an increase in the statistical weight of atoms of both types having stable electronic configurations.

Summary Thermal conversions of systems prepared by impregnation of aluminium hydroxides (boehmite, bayerite, hydrargillite) * and γ-Al 2 O 3 with chromic acid solutions, their catalytic activity in the low-temperature hydrogenation of ethylene at various stages of heating and their thermal stability at high calcination temperatures were studied. The pre-supports and γ-Al 2 O 3 prevent the thermal decomposition of the impregnated CrO 3 to various extents. The maximum decomposition temperatures of CrO 3 supported on γ-Al 2 O 3 , hydrargillite, bayerite and boehmite were observed to increase, the difference between these temperatures for γ-Al 2 O 3 and boehmite exceeding 100°C. Chromia-alumina catalysts attain their maximum activity in the low-temperature hydrogenation of ethylene after activation in vacuo at 800 to 900°C. The higher the chromia concentration, the greater is the activity of boehmite and bayerite catalysts, 10 to 15 wt.-% of Cr 2 O 3 providing maximum activities of hydrargillite- and γ-Al 2 O 3 -supported catalysts. The stabilizing effect of aluminium oxide with regard to the supported Cr 2 O 3 decreases drastically after calcination above the Tamman temperature (1000°C for Al 2 O 3 ). Both the unsupported Cr 2 O 3 and chromia-alumina catalysts are deactivated after calcination at the Tamman temperature (1200°C for Cr 2 O 3 ).