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Boron carbides of varied composition were synthesized through magnesiothermic SHS reaction at temperatures between 1500 and 2500°C and characterized by XRD. Variation in synthesis temperature was found to change the lattice parameters of boron carbide, which was associated with the disordering of the crystal structure.
Combustion of granulated 5Ti + 3Si mixtures in a flow of nitrogen gas can be performed in a single- or two-wave mode upon variation in the pressure of incoming gas flow. Suggested is the sequence of reaction stages taking place in wave I, wave II, and during cooling down.
The 2D model of coflow filtration combustion in a slit-like reactor suggested by us previously is analyzed in order to establish the influence of ignition conditions, combustion geometry, and gas flow parameters on the shape/number of fingers.
Suggested is a process, combination of thermal explosion (TE) with forced compaction (FC) termed TE-FC process, for synthesis of single-phase fine-grained pore-free compacts in the Ti-Al system. The TE-FC technique can be readily recommended for practical implementation.
Influence of ball/mill ratio on the characteristics of Ni-Al blends mechanically activated in a ball mill was explored. Burning velocity, microstructure of composite particulates, parameters of XRD diffraction patterns, density of green compacts, and their elongation during combustion were measured as a function of the overall mass ( m ) of the balls placed in the vial. Variation...
Analyzed was the behavior an aluminothermic SHS system in a rotating heat-insulated cylindrical reactor. Formulated is a model taking account interaction of centrifugal d’Alambert forces with Coriolis forces within a narrow melt-containing combustion zone. The penetration of centrifugally accelerated hot product particles into the fresh mixture was found capable of initiating, at some certain conditions,...
Dense nanocrystalline yttria ceramics without grain growth were obtained within a short densification period by a method combining SHS reaction and quick pressing (SHS-QP). The reactive mixtures consisting of Ni and Al with TiC as a diluent were used as a heat source. An yttria compact was inserted inside the reactants and warmed up by reaction heat at a heating rate of above 1300°C/min. When...
A new electrothermographic method, viz. high-speed temperature scanning, was applied to kinetic studies of reactions taking place in the Ni-Al system, including those after mechanical activation in a planetary ball mill. Treatment of the temperature profiles taken at different heating rates in terms of the Kissinger-Akahira-Sunose (KAS) approximation gave activation energy E for...
Rare earth ferrites exhibit remarkable magnetodielectric properties that are sensitive to the crystallite size. There is a major challenge to produce these materials in nanoscale due to particles conglomeration during the ferrite nucleation and synthesis. In this paper we report the fabrication of nanostructured particles of rare earth ferrites in the Me-Fe-O system (Me = Y, La, Ce, and Sm) by Solution-Combustion...
Temperature conditions for initiation of thermal explosion (volume reaction) in multilayer Ti/Al nanofoils were explored both experimentally and by numerical simulation. It is shown that there exists a critical heating rate below which thermal explosion of foil is not observed. Upon heating at rates above the critical value, the initiation temperature of thermal explosion (Tig) was found to decrease...
Harmful emissions from internal combustion engines and gas turbines can be markedly lowered upon addition of synthesis gas to hydrocarbon fuels such as natural gas. It has been suggested to perform the reactions of partial oxidation of methane as well as of dry and steam carbon dioxide reforming of methane in order to generate syngas directly in the combustion chamber of aircraft or car engines. In...
Solution-combustion synthesis and electroconductivity of calcium zirconate with glycine used as a fuel were explored. The reaction temperature was measured as a function of fuel to oxidant ratio (φ). Displacement of maximum combustion temperature Tm toward φ > 1.0 was observed. Maximum combustion temperature (856°C) was reached at φ = 1.3. An increase in φ above 1.0 leads to formation of carbon...
Influence of mechanical alloying on gas release during combustion of Ti + 2B films was studied experimentally. The volume of released gas and the rate of gas evolution were measured as a function of mechanoactivation duration and ambient atmosphere. Burning velocity of Ti + 2B films and gas release rate were found to depend on a volume of gas released during combustion, type of environment, and MA...
Polycrystalline Mg0.7 − 2xLixZn0.3Fe2 + xO4 (x = 0, 0.14, 0.21, 0.28, 0.35) thick films were prepared by simple screen printing technique. X-ray diffraction analysis confirmed that the samples had a spinel structure and texture analysis confirmed preferential orientation in the (311) plane. Doping with lithium caused a contraction in the lattice parameter obeying Vegard’s law. The variation in...
A 2D model of counterflow filtration combustion in a slit-like reactor was suggested. The gas permeability of product is assumed to be higher than that of fuel powder. The initially planar front of filtration combustion was found to lose its planarity and acquire the shape of finger(s). The mechanisms of finger(s) fading and confluence were described in detail and the parameters of the fingers formed...
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