Investigation of the Aluminum Nitride Formation During the Aluminum Nanopowder Combustion in Air

The phase formation sequences, intermediate and final products of aluminum nanopowder combustion are studied. The experiments were performed in the Budker Institute of Nuclear Physics, Siberian Branch of the Russian Academy of Sciences, Novosibirsk, at the “Precision Diffractometry II” station (SR beamline No. 6 of the VEPP-3 electron storage ring). The main combustion product was found to be aluminum nitride. In the combustion of aluminum nanopowder aluminum ?-oxide is the first to form, and aluminum nitride arises next. The formation of aluminum nitride probably occurs by successive replacement of oxygen by nitrogen from the aluminum oxide. The use of synchrotron radiation with high photon flux made it possible to determine with moderate time resolution the sequence of stages of formation of crystalline products during combustion of the aluminum nanopowder

Investigation of the Aluminum Nitride Formation During the Aluminum Nanopowder Combustion in Air

The phase formation sequences, intermediate and final products of aluminum nanopowder combustion are studied. The experiments were performed in the Budker Institute of Nuclear Physics, Siberian Branch of the Russian Academy of Sciences, Novosibirsk, at the “Precision Diffractometry II” station (SR beamline No. 6 of the VEPP-3 electron storage ring). The main combustion product was found to be aluminum nitride. In the combustion of aluminum nanopowder aluminum ?-oxide is the first to form, and aluminum nitride arises next. The formation of aluminum nitride probably occurs by successive replacement of oxygen by nitrogen from the aluminum oxide. The use of synchrotron radiation with high photon flux made it possible to determine with moderate time resolution the sequence of stages of formation of crystalline products during combustion of the aluminum nanopowder

The Influence of K4[Fe(CN)6] Aerosol on the Flame Speed of Methane-air Flame

AbstractThe influence of 1% aerosol of the water solution of potassium ferrocyanide K4[Fe(CN)6] on the flame speed of stoichoimetric methane- air flame, stabilized over the Mache-Hebra burner, has been studied experimentally and by computer simulation. The flame speed was measured at atmospheric pressure and the temperature 93°C. Addition of the aerosol of the water solution of potassium ferrocyanide results in significantly greater reduction of the flame speed of stoichiometric methane-air flame, compared to aerosol addition without the salt. Modeling the flame speed with the mechanism GRI-Mech 3.0 shows this effect to be caused by the presence of potassium atoms in the composition of this salt. The results obtained account for effectiveness of applying fine aerosol of the water solution of K4[Fe(CN)6] in extinguishing fires

Particularities of spatial kinetics of hybrid thorium reactor installation containing the long neutron source based on magnetic trap

In this work, we study the features of the spatial kinetics of installation as a hybrid thorium reactor with an elongated plasma neutron source based on a magnetic trap. The active zone of the installation under study consists of an assembly of hexagonal fuel blocks of a unified design and a long solenoid with a high-temperature plasma column passing through the axial region of the core. Combining engineering expertise in creating nuclear reactors with a physics-technical potential for obtaining high-temperature plasma in a long magnetic trap we ensure the solution of the multidisciplinary problem posed. These studies are of undoubted practical interest, since they are necessary to substantiate the safety of operation of such hybrid systems. The research results will allow optimizing the active zone of the hybrid system with leveling the resulting offset radial and axial energy release distributions. Results of our study will be the basis for the development of new and improvement of existing methods of criticality control in related systems such as "pulsed neutron source - subcritical fuel assembly"

Neutron data field in a fission reactor core with fusion neutron source at pulse-periodic operation

Results are presented on the distinctive features of the energy release dynamics in the hybrid thorium reactor operating in combination with the neutron source based on the extended magnetic mirror trap. In the reactor core configuration under study, the high-temperature plasma column is formed in a pulse-periodic mode. At a certain duty cycle (pulse ratio) of the plasma column formation, it can be expected that the fission "wave" will be formed diverging from the axial region of the system and propagating in the radial direction in the fuel assembly (blanket). Under such conditions, in order to correct the resulting offset of the energy release distribution, it is necessary to optimize the fuel composition of the assembly in order to obtain the most appropriate radial distributions of physical parameters. The studies are carried out on the basis of the full-scale model of the reactor core, in which the axial region is modified: the extended magnetic mirror trap operating as a source of fusion neutrons is installed in the reactor core axial region

High-Quality Graphene Using Boudouard Reaction

Following the game-changing high-pressure CO (HiPco) process that established the first facile route toward large-scale production of single-walled carbon nanotubes, CO synthesis of cm-sized graphene crystals of ultra-high purity grown during tens of minutes is proposed. The Boudouard reaction serves for the first time to produce individual monolayer structures on the surface of a metal catalyst, thereby providing a chemical vapor deposition technique free from molecular and atomic hydrogen as well as vacuum conditions. This approach facilitates inhibition of the graphene nucleation from the CO/CO2 mixture and maintains a high growth rate of graphene seeds reaching large-scale monocrystals. Unique features of the Boudouard reaction coupled with CO-driven catalyst engineering ensure not only suppression of the second layer growth but also provide a simple and reliable technique for surface cleaning. Aside from being a novel carbon source, carbon monoxide ensures peculiar modification of catalyst and in general opens avenues for breakthrough graphene-catalyst composite production

Scenarios of combustion of plane hydrogen microjets at sub- and supersonic velocities

Experimental data on diffusion combustion of plane hydrogen microjets emanating from a slotted micronozzle at subsonic and supersonic velocities are reported. Four scenarios of diffusion combustion of the hydrogen microjets are presented. As is found, the stabilization of subsonic combustion of the hydrogen microjet is related to the origination of a “bottle-neck” configuration of flame while in supersonic conditions the flow pattern is dominated by supersonic cells. Hysteresis of the diffusion combustion of plane hydrogen microjet is found depending on its ignition far from or close to the nozzle exit and velocity variation

Features of the formation of a flame at a collision of two laminar gas jets

The results of studies of the interaction process of two colliding axisymmetric microjets of propane/butane mixture with and without diffusion combustion are presented. The outflow of the gas mixture was carried out through round tubes at the same velocities. During the experiment, the transverse position of the tubes was varied while maintaining the angle between them. The features of the formation of the resulting jet depending on the transverse position of the tubes are defined. When the tubes are in the same plane, the resulting jet is formed in a plane orthogonal to it. This process is observed during the interaction of burning and non-burning jets. At increasing velocity of the jets, a region of local gap of the flame front was found

The effect of methyl pentanoate addition on the structure of a non-premixed counterflow n‑heptane/O2 flame

The influence of methyl pentanoate (MP) addition to n-heptane on the species pool in a nonpremixed counterflow flame fueled with n-heptane at atmospheric pressure has been investigated experimentally and numerically. Two non-premixed flames in counterflow configuration have been examined: (1) n-heptane/Ar (5.3%/94.7%) vs O2/Ar (24.1%/75.9%) and (2) n-heptane/MP/Ar (2.5%/2.5%/95%) vs O2/Ar (19.6%/80.4%). Both flames had similar strain rates and stoichiometric mixture fractions to allow an adequate comparison of their structures. The mole fraction profiles of the reactants, major products, and intermediates in both flames were measured using flame sampling molecular beam mass spectrometry. These experimental data were used for validation of a detailed chemical kinetic mechanism, which was proposed earlier for prediction of combustion characteristics of n-heptane/iso-octane/toluene/MP mixtures. The addition of MP to n-heptane reduced the flame temperature and the peak mole fractions of many flame intermediates, responsible for the formation of polycyclic aromatic hydrocarbons, specifically, of benzene, cyclopentadienyl, acetylene, propargyl, and vinylacetylene. Significant discrepancies between the calculated and measured mole fractions of cyclopentadienyl and benzene were found. A kinetic analysis of the reaction pathways resulting in formation of these intermediates in both flames and a sensitivity analysis of cyclopentadienyl and benzene were carried out to understand the origins of the observed discrepancies. The peak mole fractions of the major flame radicals (H, O, OH, CH3) were found to decrease with MP addition. The influence of MP addition on the relative contributions of the primary stages of n-heptane consumption is discussed