T. V. Dubovik

Phase interaction between ZrB2–SiC composite ceramics and oxide melts

The paper studies the mechanism of interaction between ZrB2–ZrSi2–SiC composites and dross-type oxide melts formed during the combustion of low-reactive carbons containing oxide rocks up to 30–40 vol.%. It is established that silicon carbide from the surface layer of the composite interacts with iron oxides to form spherical precipitates of the FeSix phase at 1350–1550°C in the wetting process and in contact with the dross during 10–50 h. At the composite–dross interface, a thin (~7.5–30.0 μm) layer of ZrO2 and SiO2 oxides forms (depending on the amount of SiC and ZrSi2) and serves as a protective film preventing the composite ceramics from corrosion in the oxide melts. The optimum composition of the ZrB2–ZrSi2–SiC ceramics that can be used as corrosion-resistant in oxide melts is determined.

Structure and Properties of Titanium Carbide Based Cermets with Additives of Other Carbides

The properties of wear-resistant cermets based on titanium carbide with additives of other carbides produced by two techniques are investigated. These techniques are: pressure sintering of powder mixture of the starting components (TiC, VC, Mo2C, NbC, Ni, and Cr) and pressure sintering of powder mixture of pre-synthesized solution of the starting carbides ((Ti, V, Mo, and Nb)C with additives of Ni and Cr. It is determined that cermets produced by the second technique possess more homogenous and fine-dispersed structure. The latter determines its higher mechanical strength, hardness, crack resistance, heat stability, and wear resistance, in comparison with the properties of cermets produced by the first technique.

Phase composition and properties of hot-pressed AlN–BN materials

The effect of hot-pressing temperature on the phase composition and properties of AlN–BN materials with addition of Y2O3 or SiC is studied. The composites have higher density and mechanical strength than the hot-pressed AlN–BN material without additions and retain its good insulating properties, thermal and chemical resistance, and adequate machinability.

Effect of Y2O3 and SiO2 additions on the phase formation and properties of the hot-pressed boron carbonitride composite

The dependence of phase composition and properties of the BCN composite with additions of Y2O3 and SiO2 (quartz glass) on hot-pressing temperature is studied. It is established that new strengthening phases form with the composite during reaction pressure sintering. The optimum conditions for producing the BCN composite are found. The BCN composite has high thermal strength, oxidation resistance, and electrical insulating properties.

Phase Formation in Sintering of Materials Based on Silicon Nitride with Li2CO3 and AlN Additives

We have studied the phase formation processes occurring in sintering of materials based on silicon nitride with lithium carbonate and aluminum nitride or Al powder additives. We have studied samples of different compositions that were sintered at 1450, 1550, and 1750°C under a nitrogen atmosphere. We have established that the phase composition depends on the sintering temperature, the composition of the starting charge, and also the amount and the nature of the Al-containing additives.

Study of Phase Formation Processes in the Systems Li ― N, Si3N4 ― Li3N, Si3N4 ― Li3N ― Y2O3

We have studied phase formation processes in the systems Li ― N and Si3N4 ― Li3N. By nitriding lithium powder at temperatures of 400-600°C, we obtained lithium nitride Li3N with a composition approaching stoichiometric. In the system Si3N4 ― Li3N in the temperature range 300-1300°C, the ternary compounds Li8SiN4 (500°C), Li5SiN3, Li2SiN2 (900°C), and LiSi2N3 (1300°C) are formed. The studied properties of the hot-pressed composite material of the system Si3N4 ― Li3N ― Y2O3 allow us to provisionally assign it to the class of solid electrolytes.