Abstract: The paper presents the studies on evaluation of the influence of modified additives of Y2O3-, ZrO2- and Li2O3-type on heat-conductive properties of aluminium-nitride ceramics used as circuit boards. Sintering of the studied samples was carried out using AlN powders and the powders of the modifying additives, mixed in the ball mill based on the spark plasma sintering system “SPS”. Density and heat conductivity were measured for the obtained samples. It was ascertained that the most significant level of heat conductivity was obtained when using the additive mixture made of 7 wt. % of Li2O3 and 3wt. % of Y2O3, which reaches the level of 160 W/m·K. In addition, the results of the studies show that the addition of the modified powders leads to a significant increase of density; the additive consisting of 7wt.% of Li2O3 and 3wt.% of Y2O3 produces the greatest effect.
Abstract: Mechanical strength of carbon fiber reinforced composites made of thermoplastic-thermosetting polymer matrix reinforced by carbon fibers has been determined. High mechanical strength has been revealed in tensile and compression tests both along and across the fibers. Specificity of fracturing in fiber-thermoplastics-thermosetting composition has been revealed. The effect of fiber bundling type on fracturing has been addressed.
Abstract: The results of theoretical and experimental studies of the synthesis process by the electric sintering of aluminum is a matrix composite. The mathematical model takes into account the conjugate heat transfer and porosity evolution.
Abstract: The paper studies the impact of gaseous water on the stability of micron aluminum powders in time at room temperature using the method of gravimetric analysis. The stability was studied using methods of thermal analysis during heating up to 1200 °С in air. The composition of products was analyzed using X-ray diffraction analysis. It was found out that the stability of micron aluminum powders depends on partial pressure of water vapor: the increase of pressure results in decreased stability of powders. The work gives recommendations for storing micron aluminum powders.
Abstract: The paper provides data on the structures and specifications of laser printers for 3D metal printing. The printers were engineered in Research and Educational Center "Modern manufacturing technologies" in Tomsk Polytechnic University, Tomsk, Russia. The essential difference of the given printers is their laser power. The experimental research has shown that the setups with a more powerful laser (500W) enable synthesizing the objects of higher quality in a shorter period of time. The paper also presents data on forming samples structure with the use of 3D printing.
Abstract: The influence of dispersivity of micron-sized industrial Al powders with interval of the particles diameter of 0.18-11.0 μm on their resistance to oxidation in the saturated water vapor atmosphere at its different partial pressures has been studied. It was experimentally shown the effect of increasing the stability of powders with a higher proportion of submicron particles to oxidation when exposed to water vapor, which consists in reducing the degree of oxidation with increasing dispersivity of Al powders under the same exposure conditions to water vapor. Enhancing the stability of submicron and nanoparticles of Alto oxidation with water vapor was explained by the formation on the particle surface a special charge state of the oxide film (double electric layer) which slows the diffusion of oxidant to the metal core of particles.
Abstract: The work analyses gas media (activators) and their influence on the process of circular aluminizing of nickel-based heat-proof alloys of grade ZhS. The paper studies the structure and properties of coatings in ZhS alloys after circular aluminizing in initial gas media NiCl2+NH4Cl, AlCl3+NH4Cl, NiCl2 and NH4Cl. The analysis of the formation of gas medium in the muffle of the circulation setup allows excluding unwanted inclusions (nitrogen, aluminum oxide) and their occurrence in coatings, which lead to their embrittlement and early cracking.
Abstract: The problems of hydrogen energetic as well as a method of high pure hydrogen obtaining are presented in the paper. It was suggested to use the reaction of aluminium nanopowder with water, as the reaction proceeds with high rate even at ambient conditions (the rate of hydrogen emission reached 18 ml/(s∙g)) and high degree of conversion (up to 100 %). The unreasonableness of the replacement of aluminium nanopowder to coarse-grained powder in this reaction due to the low efficiency is shown in the article. As a solution for pure hydrogen obtaining, a phenomenon of self-heating of aluminum nanoparticles and the resulting hydrogen, as well as the effect of its high-temperature diffusion through the membrane of ultrahigh molecular weight polyethylene were used.
Abstract: The article represents the results of thermal hardening of the stannic bronze alloyed with nickel without quenching. The samples were obtained by molding into a metal form applying centrifugal way of molding. Metallographic and phase analyses were carried out to define the mechanism of thermal hardening. The aging mode was chosen to ensure the maximum hardness of stannic bronze with nickel additives of the chosen structure.
Abstract: A method for synthesis of chloropyridines from pyridinyl trifluoromethanesulfonates in acetonitrile in the presence of hydrochloric acid was developed. One-pot synthesis of chloropyridines from aminopyridines via diazotization was presented. Pyridyl triflates were obtained in this reaction in situ. This method provides good yields of the target products.