V. V. Aleshin

Self-propagating synthesis of chromium acetylacetonate

After preliminary mechanical activation a mixture of solid chromium(III) chloride and sodium acetylacetonate becomes capable of reacting to form chromium acetylacetonate. The reaction may be carried out in the mode of a self-propagating process.

Conversion of ferrous compounds in a flameless combustion wave of hexogen-based systems filled with iron formate and other additives

The thermal decomposition of the energetic component and chemical reactions occurring at elevated temperatures in a flameless combustion wave of systems based on hexogen (filled with iron(II) formate and polyisocyanurate binding agent) afford a mixture of iron oxides and iron nitride as nanosized particles. The purposeful change in the ratio of the indicated basis components can provide individual Fe2O3, Fe3O4, or FeO in the conversion products. Additives of anthracene and hydroquinone to the initial composition can result in the formation of predominantly iron carbide in the products, whereas mainly iron nitrides are formed upon the addition of guanidine nitrate or 5-aminotetrazole. The addition of aluminum hydride components to the initial mixture results in the reduction of iron to the zero-valence state in the form of iron—aluminum intermetallic compounds.

Steam reforming of glycerol over composites containing nickel nanoparticles

Glycerol steam reforming catalyzed by new nickel nanoparticle-containing composites prepared via the low-temperature wave conversion of an energetic component is considered. For the μ-64.8%Ni/C and μ-41%Ni/C catalysts, even at moderate temperatures (520°C) the glycerol conversion is comparable with, or higher than, the conversion observed for the commercial 65% Ni/SiO2-Al2O3 catalyst. The composition of the resulting syngas is suitable for methanol synthesis. Above 700°C, the glycerol conversion is nearly complete and the hydrogen selectivity is up to 60%, making the new materials usable as catalysts in hydrogen production. It is possible to utilize 80% aqueous glycerol for obtaining syngas and hydrogen.

Extraction of Ti Powder from Ti–MgO–Mg(–CaO) Cakes Produced by Magnesiothermic Reduction

The extraction of Ti powder from SHS-produced Ti–MgO–Mg(–CaO) cakes by treatment in leaching solutions (HNO3, HCl, and NH4Cl) was explored and optimized in relation to such factors as concentration of leaching agent, leaching temperature, chemical resistance of target Ti powder, and extent of byproducts extraction. The type of leaching solution was found to affect the size, structure, and morphology of resultant Ti powder. Best results were obtained at 70°C with aqueous solutions of: (1) the nitric acid taken in a 6-fold excess to the Mg content of combustion product and (2) the ammonium chloride taken in a 20-fold excess to nominal Mg content.

Fine Ti Powders Through Metallothermic Reduction in TiO2–Mg–Ca Mixtures

Fine Ti powders were prepared through magnesiothermic reduction in TiO2–Mg–Ca mixtures under 4 MPa of Ar followed by acid leaching (with HCl or HNO3) and characterized by XRD, SEM/EDS, and chemical analysis. Thus prepared Ti powders exhibited the specific surface ranging between 7.0 and 30.0 m2/g. The produced Ti powders can find their application in pyrotechnics, powder metallurgy, and as raw material for SHS of inorganic compounds.

Burning of Mixtures of Copper Oxide with Titanium

This paper describes the study of the effect of physical and chemical properties of powder titanium and the equivalence ratio on the burning parameters of its mixtures with copper oxide. It is shown that the linear burning rate of such mixtures is significantly dependent on the brand of used titanium. Under normal conditions, the mixtures can stably burn with the content of copper oxide of not smaller than 13%. With an increase in the content of copper oxide to a stoichiometric ratio, there is a change of combustion regimes: multifocal, multifocal with detachment of solid residue, combination of convective and multifocal, multifocal with melt formation, flaming combustion, and fireball. It is determined that, in this system, there may be convective burning under atmospheric pressure in the absence of outer reinforcement.

Peculiarities of cellulose nitrate combustion in ballasted systems

The dependence of the combustion parameters of cellulose nitrate (nitrocellulose, NC) mixtures with magnesium oxide on the content of the energetic component was studied to reveal peculiarities of the combustion of NC in ballasted systems. It is experimentally shown that the combustion occurs in the flameless low-temperature region at the NC content in a mixture with magnesium oxide lower than 60%, and the reactive smoke reaction products can be ignited by a secondary thermal igniter heated to the temperature higher than 770 K. For the NC content in the initial mixture higher than 60%, a critical increase in the combustion temperature and velocity is observed due to the ignition of the reactive smoke products of NC decomposition inside the sample. The combustion of NC in the flame and flameless regimes is characterized by an intermediate isothermal stage at the temperature about 440 K corresponding to the temperature of onset of the fast NC decomposition. Thus, ballasting of a power material with an inert filler makes it possible to reveal and characterize the spatial and time stage character of its thermal decomposition under the combustion conditions.

Formation of nanosized particles of nickel and silver in a wave of flameless combustion of cellulose nitrate in ballasted systems

133 Wave transformation of systems consisting of energy rich solid compounds (cellulose nitrates, cyclotrimethylenetrinitramine (RDX), cyclotetrame thylenetetranitramine (HMX), N,N diethanolnitra mine dinitrate, and other similar compounds) dis persed in a medium of inorganic and organic ballasting components differs significantly from the combustion of the same energy rich compounds in individual form [1–4]. Unlike the classical self propagating high tem perature synthesis [5], the wave process in this case is driven by the heat released by the decomposition of the energy rich component.

Self-Propagation Low Temperature Flameless Combustion Synthesis of Ni and Al Nanoparticles: Time-Resolved XRD Study

The combustion of cellulose nitrate (NC) in ballasted mixtures containing an organic binder and nickel hydroxycarbonate (NiOHCO3) or silver carbonate (Ag2CO3) as precursors has been found to produce Ni or Ag nanoparticles. Formation of Ni and Ag nanoparticles in the wave of flameless combustion of NC was monitored by the time-resolved X-Ray diffraction (TRXRD) method. During the formation of the Ag nanoparticles, the diffraction patterns exhibited only signals from decreasing amounts of the precursor and newly simultaneously formed 20-30 nm silver particles. It has been detected that in the systems with NiOHCO3 the formation of the Ni 5-10 nm crystals proceeded via some 2-3 seconds diffraction-silent intermediate state of the whole system.

High-rate combustion of cellulose nitrate in filled polymer systems

It was found that, at a certain external pressure, the conventional slow flameless combustion of nitrocellulose in filled compositions can go over into a high-rate low-temperature mode, with a burning velocity increasing by more than 40-fold. It was shown that the critical external pressure at which the changeover of the combustion modes occurs decreases with the sample porosity. It was assumed that the high-rate combustion of nitrocellulose in filled systems proceeds by the well-known mechanism of convective combustion of energetic condensed systems with some specific features.