Materials Engineering and Technologies for Production and Processing

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Authors: D.A. Vinnik, S.A. Gudkova, R. Niewa
Abstract: Lead and aluminum substituted barium hexaferrite (Ba,Pb)Fe12–хAlхO19 single crystals were grown from lead oxide flux at 1260 °C as hexagonal plates with sizes of about 2 mm. A maximum substitution level of x = 4.82 was achieved for the first time for bulk single crystals. The variation of the unit cell parameters with Al content is in good agreement with literature data on exclusively Al substituted barium hexaferrite, while the substitution of Ba by Pb has hardly any influence. Similarly, Pb has only a negligible influence on the magnetic properties, while Al substitution significantly reduces the saturation magnetization in a very similar manner as known from Pb-free barium hexaferrite.
Authors: Viacheslav V. Avdin, E.P. Yudina, I.V. Krivtsov
Abstract: Hydrolysis products of aqueous yttrium nitrates obtained by sol-gel method at room temperature, under atmospheric pressure without any templates and structure directing agents were investigated by thermal analysis combined with mass spectrometry of thermolysis products, XRD and scanning electron microscope with elemental EDS analyzer. Formation of yttrium hydroxonitrocarbonates with various ratio depending on synthesis conditions was found. The samples obtained at 8.5 pH with hydrolysis time at least 40 min using ammonia water solution have the least quantity of impurities and demonstrates the most visible layered morphology. The most explicit layered morphology and the least amount of impurities were revealed in the samples obtained at 8.5 pH with hydrolysis time at least 40 min using ammonia water solution as a hydrolytic agent.
Authors: D.A. Vinnik, E.A. Trofimov, D.A. Zherebtsov
Abstract: This paper presents the results of the synthesis of compounds of BaO-Fe2O3 system and the results of the study of nature and the melting temperatures of the resulting compounds. Based on the analysis of published data, as well as the results of our studies the systematization of information on the BaO-Fe2O3 system was conducted and an updated phase diagram of this system was proposed.
Authors: V.M. Lipkin, Y.M. Berezhnoi, M.S. Lipkin
Abstract: This article presents the research on the effect of substrate nature and electrolysis modes on ultramicron and nanosized electrolytic powders formation regularities. It was found that the preliminarily electropolishing of titanium cathode in combination with impulse electrolysis mode for nickel and copper powders obtaining provides for the predomination of nanosized fraction. The presence of water soluble polymers in the electrolyte for copper powder obtaining, polyvinylpyrrolidone (PVP) and polyacrilamide (PAA) allows forming stable dendritic powders with low agglomeration. Using of powders stabilized by polymers allows obtaining compositions with uniform particle distribution across the whole volume of the sample which provides for heightened wear resistance of composition materials.
Authors: S.P. Samoilov, A.O. Cherniavsky
Abstract: Mechanical behavior of a molybdenum alloy for high-temperature application was investigated at monotonic loading up to fracture, stress-and strain-controlled cyclic loading and short-term creep (less than 9 hours) under the temperatures from 293 to 1773 K using Gleeble-3800 physical simulator. The tests show that plastic strain corresponding to the tensile strength of the material under monotonic loading is small enough (<1%) whereas residual plastic strain after fracture exceeds by 50%. Repeated loading decreases the tensile strength and yield stress, but increases stable (rising) part of stress-strain curve. Increase in the test temperature leads to the change in fracture type from ductile to quasi-brittle distributed at a temperature above 1673 K. Under relatively low temperatures the rheological properties of the material depend strongly on the material processing history. Obtained creep data allows putting up a thermo-activational type equation used to calculate the steady creep rate. Coupling with the known Hoff's model for the creep prefracture stage, this equations allow not only strain rate but also adequate estimation of fracture time.
Authors: A.N. Anikeev, I.V. Chumanov, V.I. Chumanov
Abstract: The current paper presents yttrium oxide wetting angle examination. The test was performed in accordance with two different methods: contact and noncontact heating. Upon completion of the test, microstructural and spectral analysis of substrate/metal contact areas was conducted. Test findings are listed in the Conclusions.
Authors: G.G. Mikhailov, L.A. Makrovets, L.A. Smirnov
Abstract: Fusibility curves of FeO–La2O3–Al2O3, FeO–Ce2O3–Al2O3, La2O3– Ce2O3–Al2O3 oxide systems are created based on the literature data and modern thermodynamic theories of oxide and metal melts. Admitting the oxide systems conjugation with the area of metal melts existence, we define oxide phases, which can maintain the equilibrium with metal melts of Fe–Ce–Al–O, Fe–La–Ce–Al–O systems. The surfaces of component solubility are created for above mentioned metal melts. For Fe–Ce–Al–O system it is established that the following phases can be at equilibrium with metal: Al2O3, Сe2O3, FeO∙Al2O3, Сe2O3∙11Al2O3, Сe2O3∙Al2O3, and the oxide melt (FeO, Al2O3, Сe2O3, СeO2). For Fe–La–Ce–Al–O system the following oxide phases can be at equilibrium with the liquid metal: La2O3, Al2O3, Сe2O3, La2O3∙Al2O3, Сe2O3∙11Al2O3, Сe2O3∙Al2O3, and the oxide melt (FeO, La2O3, Al2O3, Сe2O3, СeO2). Diagrams of active components consumption, which are used to establish the possibility of chosen equilibrium, are created for iron deoxidation with cerium and aluminium as well as with Ce and La at fixed Al content (0.01 wt. %).
Authors: V.N. Lozovskiy, B.M. Seredin, N.Yu. Arkhipova
Abstract: The article includes the analysis of the features related to local doping of silicon using electrically active doping agents by thermomigration of binary and ternary liquid zones as compared to doping by diffusion. The concentration range of doping by binary zone migration is found to be substantially narrower than that of doping by diffusion. Introduction of a third component to the liquid phase ena-bles expansion of the thermomigration doping range to the values exceeding the diffusion doping range by the same doping agent. For silicon crystals, this technological feature of thermomigration is produced by using GaxAl1-xSi and SnxAl1-xSi ternary zones. The crystal doping rate by thermomigration in techno-logically relevant situations was shown to exceed the rate of diffusion doping by orders of magnitude. The layers doped by thermomigration of stably moving liquid zones are structurally more perfect than diffusion layers.
Authors: G.G. Mikhailov, D.A. Zherebtsov
Abstract: The parameters of calcium and oxygen interaction in liquid iron are revised. The Vagner parameter values of several hundreds or dozens are proved to be wrong. The recommended value for the constant for the reaction of dissolved calcium and oxygen forming solid calcia is /CaO/=[Ca]+[O] is: lgK/CaO/=-34100/T + 13.46. Vagner parameter for the interaction of Ca and O in liquid iron should be expressed in units (we used =–1.41), not in hundreds. The equilibrium diagram of calcium and oxygen content in liquid iron is calculated at 1550-1700 °C and 0.00001-0.1 mass % Ca. The minimum oxygen content possible to be achieved at 1550 °C and 1 atm is about 0.001 mass %.

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