V. E. Loryan

Aluminum Combustion in Nitrogen

The process of nitration of aluminum and aluminum‐containing mixtures in the regime of self‐propagating high‐temperature synthesis with a high pressure (up to 300 MPa) of the reacting gas (nitrogen) is considered. The dependences of ignition temperatures and also burning temperatures and burning rates of these initial mixtures on test conditions (nitrogen pressure and composition of the initial mixture) are studied. The dependence of the burning rate of initial mixtures on factors affecting spreading of the liquid component (melt containing aluminum and nitrogen) over the surface of the second component (aluminum nitride or titanium diboride), such as the equilibrium wetting angle, interaction at the interface, and melting of the second component, is studied. The microstructure and some properties of materials obtained are examined. Based on these studies, the combustion mechanism is determined, a mechanism of phase formation in combustion of these mixtures is suggested, and the structure of the combustion wave is determined.

SHS under high pressure of nitrogen gas: Feasibility of nitrides melting

Under some certain conditions, SHS reactions yielding AlN, BN, and Si3N4 under high pressure of nitrogen gas can be accompanied by fusion of reaction products. Upon appropriate choice of filler, compact materials with a porosity of around 10% can be readily synthesized by SHS nitridation under pressure.

SHS in preliminary structured compacts: II. Ti-2B and Ti-Al blends

Stepwise densification of Ti-2B and Ti-Al blends was used to prepare green compacts with an ordered structure. The latter ones were then used to explore combustion synthesis in these mixtures with special emphasis on the possibility of inheriting a structure of green compact by a combustion product. It has been demonstrated that, at some certain conditions, an ordered structure of green compact can be inherited by a combustion-synthesized product.

Uniaxial compression of Ti, B, and T-B powders: Structurization in case of spherical Ti particles

Explored was the uniaxial compression of Ti, B, and T-B powders. The density of compressed samples as a function of their mass was found to be non-monotonous in its character. This observation agrees with predictions of earlier model calculations for compression of ideal spherical particles.

Sintering of SHS-produced α-Si3N4, α-SiAlON, and β-SiAlON

Explored was the sintering of SHS-produced α-Si3N4, α-SiAlON, and β-SiAlON in the presence of sintering aids such as Y2O3 and Al2O3. Process conditions were optimized to prepare sintered sialon ceramics with a high relative density and good strengths characteristics.

On Combustion of Boron in Nitrogen Gas

Investigated was the nitridation of boron-containing powder compacts with nitrogen gas in a high-pressure SHS reactor. The porosity of combustion products was calculated and measured as a function of green porosity and composition. Calculated data were found to reasonably agree with experiment.

Aluminothermic SHS of ferrochromium from ore concentrate: Influence of Al content of green composition on phase segregation

59 Over the past decades, the existing methods for production of ferrochromium [1–5] have been supple mented by SHS processes for production of alloying agents [6] and ferroalloys [6–8]. In this work, we explored the applicability of SHS method to fabrica tion of ferrochromium from chromium ore concen trate by metallothermic SHS. The powders of the ore concentrate (from Shorzha deposit, Armenia) used in our experiments are charac terized and Tables 1, 2. Al powders of ASD 1 brand were 98% pure and had a mean particle size of below 50 μm. Since the are concentrate contained the oxides (Al2O3, MgO, CaO) that could not be reduced with Al, the formers were excluded from material balance cal culations. Despite a relatively low content of Si con taminant in green composition (4.07%, Table 1) its contribution to the reaction energetics was taken into account. Combustion synthesis of ferrochromium was carried out by the following scheme (stoichiometric coefficients are given in wt %):

Ceramic Material Based on Domestic Silicon Nitride Powder Prepared by an SHS Method

Research results are presented for development of hot-pressed high-temperature heat-resistant ceramic material based on silicon nitride in the system Si3N4–MgO, and physicomechanical properties are determined over a wide temperature range.

SHS in preliminary structured compacts: I. Ni-Al blends

Stepwise densification of non-activated and mechanically activated Ni-Al blends was used to prepare green compacts with an ordered structure. The latter ones were then used to explore combustion synthesis in these mixtures with special emphasis on the possibility of inheriting a structure of green compact by a combustion product. It has been demonstrated that, at some certain conditions, an ordered structure of green compact can be inherited by a combustion-synthesized product. This observation can be expected to open up new horizons for synthesis of new intermetallics with an ordered macrostructure.

Formation of Catalytically Active Metal-Ceramic Membranes for the Hybrid Reactor

Porous metal-ceramic membranes were prepared by self-propagating high-temperature reduction from a mixture of Ni- and Co-oxide and Al powders. The obtained membranes were catalytically active and contained ultra-disperse Ni and Co nanoparticles 10 – 20 nm in size on the surfaces of open pores.