A model of thermodynamics of a reacting mixture of rarefied gases and a suspension of condensed species is developed by using statistical physics methods. An
NVT
ensemble is considered for ...determining the detailed equilibrium chemical composition, and the minimum of the free energy of the mixture of possible species is found numerically. Tabular data for the species are used for determining the enthalpy and free energy of chemical compounds. An algorithm that allows the Chapman–Jouguet detonation parameters to be determined for a wide range of combustible mixtures is developed. The model is tested through comparisons of the predicted and experimental detonation velocities. Good agreement for mixtures with oxygen excess is demonstrated. For compositions with the formation of a significant amount of condensed carbon, the predicted and experimental detonation velocities agree reasonably well.
The paper presents the characteristics of impact diamonds from the Popigai meteorite crater, formed by martensite transformation of graphite-bearing gneisses due to meteorite impacts. These diamonds ...have a nanopolycrystalline structure and consist of two phases, i.e., cubic (diamond) and hexagonal (lonsdaleite). They are distinguished by phenomenal abrasion resistance, on average twice as high as the abrasion resistance of single-crystalline diamonds. The work considers the possibility of producing similar diamonds by explosion. It is noted that diamonds, which are most similar in structure, are produced through exploding a composition of graphite and hexogen; lonsdaleite is present in the material obtained in this way. However, in any case, diamonds produced by explosion are very small in size, incomparable with natural ones.
Conducts of high-speed x-ray experiments on recording the interaction of shock waves in structural materials with synchrotron radiation are discussed using polycarbonate and magnesium as an example. ...The regimes of reflection of a shock wave from an obstacle, of collision of counter-propagating shock waves in a cylinder, and of descent of a shock wave from the lateral surface of the cylinder toward its center have been implemented. Differences in the mechanics of mass fluxes arising in polycarbonate and magnesium on exposure to shock waves have been shown.
Over the past two decades, LIH SB RAS and BINP SB RAS have jointly conducted experiments on time-resolved (TR) small-angle x-ray scattering (SAXS) with detonating high explosives. The purpose of ...these experiments is to restore the dynamics of carbon species condensation to diamond nanoparticles by analyzing series of SAXS patterns behind the detonation front measured in real time with fast detectors. This knowledge is crucial for the development of reliable detonation models. In this paper, we compare SAXS patterns of identical nanodiamond samples measured at the TR-SAXS extreme state of matter end-station (BINP SB RAS) in the static mode under realistic conditions simulating fast real-time measurements with polychromatic SR beam and traditional SAXS BioMUR beamline at the Kurchatov Synchrotron Radiation Source (NRC "Kurchatov Institute") with monochromatic synchrotron radiation (SR) beam. These experiments confirm that the size of scattering inhomogeneities determined in dynamic experiments with single bunch exposure with polychromatic SR beam is correct.
Explosion in the planetary interior and the ejection of the part of outer layers of the planet into orbit to form a satellite makes it possible to explain the elemental and isotopic composition of ...the Moon. Satellite formation has been simulated for a two-dimensional geometry using molecular dynamics methods for up to hundreds of thousands particles. The particles are asteroid-size bodies (diameter of about 100 km) which interact with each other according to Newton's law. The properties of the compact material are described by a short-range potential. A number of calculations with varying initial conditions have shown the scenario of the explosive origin of the Moon to be realistic and preferred over other hypotheses.
A discrete element model of granular compaction is presented, in which only the elastic interaction force is taken into account. Granules are considered as a set of nodes that can break or link with ...each other. The nodes are arranged in an fcc lattice. The model is applied for the numerical assessment of the strength characteristics of a granular material. It is shown that the tensile strength of the material depends on the diameter of granules. The extrusion of the compacted material is numerically simulated.
The features of near-threshold mode of initiating by gas-tight piston and high- enthalpy gas flow was evaluated for a powder density explosive PETN. Both methods lead to the development of detonation ...in about 10 μs time. The synchrotron radiation diagnostics have shown that the initial stages of the process were significantly different, that diversity being caused by the influence of the gas flow in the pores of the charge. In this work, the effect of the gas flow on the mode of initiation was studied experimentally.
The paper presents a technique for introducing carbon nanotubes into high explosives (HEs). For a number of explosives (trinitrotoluene, pentaerythritol tetranitrate, benzotrifuroxan), it was ...possible to achieve the appearance of conductivity by adding a small amount (up to 1% by mass) of single-walled carbon nanotubes TUBALL COAT_E H2O (CNTs) produced by OCSiAl. Thus it is possible to reduce the sensitivity of explosives to static electricity by adding an insignificant part of conductive nanotubes. This will increase safety of HEs during production and application and will reduce the number of accidents.
RDX containing a small amount of single-walled carbon nanotubes is obtained by the method of co-precipitation out of a solution. The detonation of this composition is studied by an electromagnetic ...method of mass velocity measurement and by a high-resolution electroconductivity method. A clearly expressed chemical spike is observed. Preliminary indications of reaction acceleration in the presence of nanotubes are obtained. The electroconductivity measurements are complicated because of the noticeable conductivity of the original material; if this factor is taken into account, the electrical conductivity profiles behind the detonation front are similar to those observed for pure RDX. Possible reasons for the influence of nanotubes on detonation characteristics are discussed.
Detonation of Ultrafine Explosives Ershov, A. P.; Andreev, V. V.; Kashkarov, A. O. ...
Combustion, explosion, and shock waves,
05/2021, Letnik:
57, Številka:
3
Journal Article
Recenzirano
Detonation of PETN and HMX with a particle size of about 1
m was investigated by an electromagnetic method. At an initial density of 0.9–1.2 g/cm
3
, the von Neumann spike was either weak or not ...observed at all. This indicates a fast reaction whose time is outside the experimental resolution (about 5 ns). Electrical conductivity measurements provided only a rather rough upper-bound estimate of the reaction time (less than tens of nanoseconds). Density measurements using synchrotron radiation showed that the initiation of PETN with an air shock wave led to an almost instantaneous initiation of detonation, without an acceleration stage. In general, the results of the study confirm that the chemical reaction rate in ultrafine explosives is increased.
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