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[en] Formation of the zirconium dioxide fibre crystal structure was studied by the methods of thermogravimetric, X-ray phase, chemical and petrographic analyses within a range from the indoor temperature to 2000 deg C. The fibres are obtained by extruding a mixture of zirconyl and calcium acetate aqueous solutions. It is shown that introduction up to 10 mol % (calculated for CaO) of calcium acetate as a stabilizing additive does not affect the rheological properties of the zirconyl diacetate solution; The fibres are moulded as continuous, transparent and elastic threads sufficiently strong for subsequent production operation. It is stated that formation of one-phase ZrO₂-base solid solution of the fluorite-type cubic structure with 6 mol % CaO content is observed already at a temperature of 800 deg C

[en] Efficiency of technical boron carbide grinding in magnetic-vortical apparatus and planetary mill is comparatively estimated. EXperimental dependences of the specific surface on the grinding period are described by the Khodakov equation. Efficiency of boron carbide grinding in the planetary mill is established to be an order higher than in the magnetic-vortical apparatus. However grinding in the planetary mill is accompanied by more intensive iron contamination. Dependence of briquette density on the pressure is studied for boron carbide powders produced by different methods. Boron carbide powder pressing is described by the logarithmic dependence of relative volume on pressure

[en] Interaction of zirconium and niobium carbides in homogeneity region with 12-n. solutions of nitric, hydrochloric and sulfuric acids has been studied. It has been established that in the acids which are not oxidants, zirconium and niobium carbides in homogeneity region are less chemically stable, than carbides of stoichiometric composition. It has been shown that chemical stability of carbides of finite composition is higher than chemical stability of the corresponding metals, and for carbides of non-stoichiometric composition the reverse is true

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[en] Methods of optical and electron microscopies as well as petrographic analysis were used to study morphological peculiarities of continuous polycrystalline zirconium dioxide fibres produced by extrusion of salt solutions. It is found that depending on the production process parameters the fibres can be produced having the following structure: homogeneous fine-grain (dsub(ef)=20 μm), ''bamboo'' structure consisting of monocrystals oriented along the fibre axis and heterogeneous structure composed of two-three zones represented by crystals of zirconium dioxide of various modifications and calcium zirconate. It is shown that the fibres posses a smooth brilliant surface and are optically transparent. The fracture is vitreous. Most commonly occurred defects are longitudinal and cross cracks, diameter nonuniformity and length distortion, surface cleavages and holes

No abstract available