- INTERACTION OF BORON FIBRES WITH ALUMINIUM MELT DURING METALLIZATION.
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The aim of the paper is to investigate interphase interactions on the fibre-melt interface boundary during metallization of boron fibres by aluminium. Using methods of selective etching and weighing it has been stated that chemical interaction of boron fibres with the aluminium melt develops in 2 stages: firstly - boron solution in liquid aluminium occurs, secondly - formation of chemical compounds AlB//2////, //A//l//B//1//2 on the interface boundary. Mechanical tests fractographic analysis have stated that if the fibre material is soluted in the melt then fibre strength raises due to the lower influence of surface defects; the appearance of aluminium borides on the interface boundary is followed by a decrease in the initial fibre strength.
- Chernyshova,Tylkina,Gelvich
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- X-ray investigation of the Al-B-N ternary system: Isothermal section at 1500 °C: Crystal structure of the Al0.185B6CN0.256 compound
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The equilibrium phase diagram has been established using X-ray powder diffraction for the ternary Al-B-N system over the whole concentration region at 1500 °C. No ternary compounds have been observed. The crystal structure of the Al0.185B6CN0.256 compound (Cmcm space group, Z = 8, a = 5.685(2) A?, b = 8.903(3) A?, c = 9.122(3) A?, V = 461.70 A?3, ρ = 2.563 g/cm3, μ = 0.17 mm-1, R = 0.0424 for 407 reflections with Fo > 4σ(Fo)) was determined from single crystal X-ray diffraction (automatic diffractometer BRUKER AXS CCD, Mo Kα radiation) and electron microprobe analysis. The structure is related to the Al0.61B6.50, Al0.253B6.37C and Al0.325B6C structures.
- Rizzoli,Salamakha,Sologub,Bocelli
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- Combustion in a system of conjugated layers and high-temperature synthesis of materials
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The possibility of constructing layered systems for high-temperature synthesis of materials is demonstrated. The cases of vertical and horizontal arrangement of layers, which ensure different types of a technological combustion of the initial reactant mixtures with or without subsequent interaction of the reaction products formed, are considered. The conditions are found for the synthesis of alkaline-earth metal titanates and aluminum borides in the layered systems.
- Ksandopulo,Baidel'Dinova
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- Boride phase formation in the production of Al-B master alloys
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The formation of boride phases is studied in the production of Al-B master alloys, which involves chemical reactions of KBF4 and aluminum melts. Boron is reduced from KBF4 and reacts with aluminum to form AlB12 and AlB2 depending on processing conditions. AlB12 forms at the Al/flux interface and subsequently reacts with aluminum to form AlB2 in a slow process while moving away from the Al/flux interface. In designed experiments, aluminum reacted with KBF4 droplets producing dense AlB12 shells trapping KAlF4 salt inside at high temperatures. In comparison, the majority of individual AlB2 particles is located near the Al/flux interface inside the aluminum matrix in a circular shape. Meanwhile, a uniform dispersion of AlB2 particles in the aluminum matrix is also observed away from the Al/flux interface. It is revealed that boron, after being reduced from KBF4 by aluminum, has a high tendency to build up at the Al/flux interface, forming AlB12 and subsequently transforming to AlB2.
- Wang, Xiaoming
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- Magnetization study of the ultra-hard material MgAlB14
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Magnetic susceptibility χ versus temperature T, magnetization M versus T, and isothermal M versus magnetic field H studies of the ultra-hard material MgAlB14 were carried out in search of superconductivity or ferromagnetism in this compound. Two types of samples were synthesized: (1) powder and (2) chemically substituted and unsubstituted hot pressed pellets prepared from mechanically alloyed powders. χ(T) measurements on a powder sample revealed temperature-independent diamagnetism with a Curie-Weiss impurity concentration equivalent to ～ 1mol% of spin-12 ions. In contrast, M(T) and M(H) data on the hot pressed samples, both substituted and unsubstituted, showed evidence of ferromagnetic transitions above ～ 330K. Scanning electron microscopy and Auger microprobe analysis of the hot pressed samples indicated that both substituted and unsubstituted samples contained significant concentrations of Fe impurities. We conclude that pure MgAlB 14 is neither a superconductor nor a ferromagnet above 1.8K and exhibits temperature-independent diamagnetism from 1.8K up to room temperature. The ferromagnetism observed in the hot pressed samples is likely due to Fe impurities abraded from the stainless steel mills used to mix the starting materials prior to hot pressing the samples.
- Hill,Johnston,Cook,Harringa,Russell
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