Breakup of steady-state detonation in hydrogen-air mixtures under the action of propane admixtures

Minor amounts of propane effectively inhibit the detonation of hydrogen-air mixtures at atmospheric pressure. Controlled variation of the amount of the admixture provides means to break up the steady-state detonation wave at a preset distance from the place of its origination and to regulate its velocity in a certain range. This is possible due to the branched chain character of the combustion reaction in the detonation mode. Propane is not inferior to propylene in the effectiveness of action on detonation and, owing to its low cost and higher availability, is preferable as a means of preventing the explosion and detonation of hydrogen-air mixtures.     

Surface modification of detonation nanodiamonds by the perfluorobutyl radical

The method was developed for surface defunctionalization of detonation nanodiamonds by substitution of a perfluorinated organic radical for hydroxyl and carboxyl groups. Size-mass distributions of modified particles of detonation nanodiamonds in water and toluene were studied     

Determination of heats of detonation and influence of components of composite explosives on heats of detonation of high explosives

The heats of detonation of 20 simple high explosives and explosive mixtures were determined by means of an adiabatic detonation calorimeter designed by the authors. The results indicated that the performance of the instrument was reliable and the experimental data were very accurate. For explosive mixtures, there was a linear accumulative relationship between the heats of detonation of the explosive mixture and its components. Accordingly, the heats of detonation of explosive mixtures could be calculated directly from the heats of detonation of simple explosives and the characteristic heats of other components. The experiments showed that the gold or brass shell of the cylindrical charge could be substituted by a thick-walled porcelain shell, which had the advantage of cheapness.

     

1,3,5,7-四硝基金刚烷结构和性能的理论研究

在DFT-B3LYP/6-31G*水平下求得1,3,5,7-四硝基金刚烷的全优化分子几何和电子结构. 经简谐振动分析求得其IR谱并作归属. 由统计热力学求得其不同温度下的热力学性质. 以非限制性半经验MO方法探讨其热解机理, 求得各反应通道的过渡态和活化能, 发现热解始于侧链C—NO₂键的均裂. 还基于理论计算密度和生成热, 以Kamlet-Jacobs方程估算其爆速和爆压.     

六硝基六氮杂三环十二烷的结构和性能--HEDM分子设计

The compound Hexanitrohexaazatricyclododecane was designed and calculated by using the density functional theory method at the B3LYP/6-31G level. According to the calculated results, there are two optimized conformational structures, boat (α) and chair (β). It is found that the former is more stable based on the analysis of total energies, frontier molecular orbital energies and Mulliken populations. The IR spectra were obtained and assigned by means of normal-mode analyses. Thermodynamic properties at 200-800 K were provided using the statistical thermodynamics method. Finally, the detonation velocity and detonation pressure were predicted by Kamlet formula based on the calculated theory density and heat of formation. The predicted detonation velocity and detonation pressure of α conformer are 9.46 km/s and 41.74 GPa, while those of β are 9.34 km/s and 40.02 GPa, respectively.     

Biological activity of detonation nanodiamond and prospects in its medical and biological applications

The present review summarizes and analyzes recent advances in the field of medical and biological applications of detonation nanodiamond and, on this basis, considers most promising ways of creation of anticancer and antimicrobial drugs, diagnostic agents, and nanocompositions for orthopedic surgery. In addition, progress in the surface chemistry of detonation nanodiamond is discussed and problems related to purposeful surface modification with a view to obtain detonation nanodiamond with desired properties ensuring their successful application in biology and medicine are considered.     

Synthesis and Study of Nanodispersed Carbon in the Combustion of Acetylene in a Flow Detonation Tube

Nanodispersed carbon was obtained via high-temperature combustion of acetylene–oxygen mixtures in a flow-through tubular chamber in cyclic detonation waves (“pulsed detonation”) at a constant propagation velocity (D_det ≈ 2150 m s^–1). It was found that the position of a plateau in the curve describing how the detonation velocity depends on the content of oxygen in the starting detonation mixture in the range 15–30% coincides with the range of descending branches of the dependences of the specific adsorption surface area and adsorption of dibutyl phthalate by aggregated particles. Various physicochemical methods of analysis (X-ray diffraction analysis, Raman spectroscopy, high-resolution transmission electron microscopy, etc.) were used to comparatively examine the properties of nanodispersed carbon and of the known industrially produced domestic and foreign brands of technical-grade carbon. The conditions were found in which detonation nanocarbon particles are obtained in a certain range of parameters of micro- and macrostructures with improved morphology and basic electrical properties.

     

Critical detonation diameters of highly dispersed energetic substances

The relationship between the critical detonation diameters of energetic substances and their specific surface area was revealed from the results of studying the detonation ability of a series of energetic substances [pentaerythritol tetranitrate (TEN), cyclotrimethylenetrinitramine (RDX), cyclotetramethylenetetranitramine (HMX), 2,4,6-trinitrophenylmethylnitramine (tetryl), benzotrifuroxan (BTF), hexanitrohexaazaisowurtzitane (CL-20), dinitrodifurazanylfuroxan (DNTF), dinitrodifurazanylfurazan (NTF), 1,1-diamino-2,2-dinitroethene (FOX-7)]. A mathematical expression for this relationship was suggested. The critical detonation diameters of highly dispersed (micrometer particles) energetic substances were determined by experiments and calculations. These diameters are in the range 0.06–0.8 mm, which makes these substances suitable for use in aerospace engineering, priming systems, detonation manifolds, and explosion logic devices.     

Counterion condensation in hydrosols of single-crystalline detonation nanodiamond particles obtained by air annealing of their agglomerates

The pattern of previously recorded dependences of the specific surface charge and electrophoretic mobility of monodisperse detonation nanodiamond particles on pH of aqueous KCl solutions suggests that counterions are condensed on the particle surface. Counterion condensation is considered in terms of the Levin model, and the experimental ratios between the densities of the electrokinetic and surface charges of dispersed particles, as well as the fractions of condensed counterions, are calculated as depending on pH and KCl concentration in nanodiamond hydrosols. The obtained dependences lead to the conclusion that counterion condensation on the surface of detonation nanodiamond particles does indeed take place.     

The relationship between the kinetic data of the low-temperature thermolysis and the heats of explosion of inorganic azides

The primary chemical processes of the thermal decomposition and detonation change of inorganic azides possessing explosive character is considered by means of the linear relationship between the activation energies, E, of the initial stage of low-temperature thermolysis, and the heats of explosion of these substances. Also, the possibility of applying E values in the estimation of the initiation capability of azides is considered.     

Adsorption and structural characteristics of the surface of modified nanodiamond powders

The adsorption of benzene and water vapors on the surface of detonation nanodiamond powders that differed in particle size, degree of their strong aggregation, and chemical state of their surface was studied. Specific features of the processes of adsorption of polar and nonpolar molecules on chemically modified surfaces of nanodiamonds are analyzed.     

Computational Investigation on the Surface Electronic Density, Morphology and Detonation Property of 1,1-Diamino-2,2-dinitroethylene （FOX-7） Crystal

The present study constructed and optimized FOX-7 crystal using a novel technique including grand canonical monte carlo (GCMC), density functional theory (DFT) and molecular dynamics (MD) methods. Therein, the crystal density, atomic and electronic actions were considered. The results showed that the 1.96 g?cm-3 FOX-7 crystal has the highest stability and detonation properties, such as the total crystal energy, surface electronic density, friction sensitivity, detonation pressure, and so on. These results are close to the experimental data.     

The effect of simple electrolytes on coagulation of hydrosols of monodisperse negatively charged detonation nanodiamond

The influence of the concentration of potassium and barium chlorides on the aggregation stability of a hydrosol of monodisperse negatively charged detonation nanodiamond with particle sizes of 4?5 nm obtained by annealing of its agglomerates in air has been studied by turbidimetry. The experimental results have been discussed within the classical and generalized Derjaguin?Landau?Verwey?Overbeek theories. The analysis of the pair interaction potentials calculated for ultradispersed particles of detonation nanodiamond has led to the conclusion that the coagulation occurs by the barrier mechanism in the primary potential minimum. It has been assumed that the structural component of the interparticle interaction energy contributes to the total balance of the surface forces.     

改性硝酸铵爆轰安全性研究 Ⅰ.CaCO3和MgSO4对硝酸铵爆轰安全性的影响

将碳酸钙和硫酸镁改性的硝酸铵按照工业炸药配方配制成铵油(ANFO)炸药，以8号雷管起爆，对硝酸铵的爆轰安全性进行了评价。采用恒温热分解和示差扫描量热法，研究了改性硝酸铵及铵油炸药的热分解行为。测定了改性硝酸铵的比表面积以解释爆轰结果。得出如下结论：硝酸铵含40％的碳酸钙，或25％碳酸钙和5％硫酸镁的混合物，所配制的铵油炸药不能被8号雷管起爆。碳酸钙同硝酸铵发生复分解反应放出NH3、H2O和CO2气体，反应程度与碳酸钙的含量、温度和时间成正比。虽然硝酸铵中加入碳酸钙后提高了ANFO炸药的热稳定性，但由于上述气体的逸出增加了改性硝酸铵的比表面积。因此，在硝酸铵中加入少量的碳酸钙不能达到爆轰安全性的要求。硫酸镁与硝酸铵形成复盐，可减缓硝酸铵和碳酸钙之间复分解反应的速度．有利于降低硝酸铵的起爆感度。     

Branched-chain nature of hydrogen combustion in the detonation mode

Minor admixtures of the simplest hydrocarbons can prevent detonation and break down a steady-state detonation wave in hydrogen-air mixtures at atmospheric and higher pressures. Therefore, the determining role in the appearance and propagation of the detonation wave is played by the branched mechanism and, accordingly, by the competing chain branching and termination reactions. Without taking into account these reactions, combustion theory cannot explain the basic regularities of the process, including the concentration limits of detonation.     

Natural limit of the number of copper ions chemisorbed on the surface of a detonation nanodiamond

The upper limit of the amount of copper ions that can be grafted to the detonation nanodiamond surface has been calculated. A maximum of 34 wt% copper can be grafted to carboxylated and hydroxylated 5 nm nanodiamonds. The results of calculations have been compared with the experimental and published data.     

Regularities in the consumption of the initial reactants in various kinetic regimes

Using hydrogen oxidation as an example, it is demonstrated that, when gas ignition is prevented by means of inhibition, there is practically no consumption of the initial reactants because reaction chains do not form for lack of time and the rates of intermolecular reactions are insignificant. When the propagating flame and detonation wave are partially suppressed, the inhibitor is consumed only in chain termination reactions involving reactive intermediate species. Oxygen is additionally consumed in its reactions with products of incomplete inhibitor conversion.     

Substituent effects on the properties related to detonation performance and sensitivity for 2,2',4,4',6,6'-hexanitroazobenzene derivatives

To look for superior and safe high energy density compounds (HEDCs), 2,2',4,4',6,6'-hexanitroazobenzene (HNAB) and its -NO(2), -NH(2), -CN, -NC, -ONO(2), -N(3), or -NF(2) derivatives were studied at the B3LYP/6-31G* level of density functional theory (DFT). The isodesmic reactions were applied to calculate the heats of formation (HOFs) for these compounds. The theoretical molecular density (ρ), detonation energy (E(d)), detonation pressure (P), and detonation velocity (D), estimated using the Kamlet-Jacobs equations, showed that the detonation properties of these compounds were excellent. The effects of substituent groups on HOF, ρ, E(d), P, and D were studied. The order of contribution of the substituent groups to P and D was -NF(2) > -ONO(2) > -NO(2) > -N(3) > -NH(2). Sensitivity was evaluated using the nitro group charges, frontier orbital energies, and bond dissociation enthalpies (BDEs). The trigger bonds in the pyrolysis process for all these HNAB derivatives may be Ring-NO(2), Ring-N═N, Ring-NF(2), or O-NO(2) varying with the attachment of different substituents. BDEs of trigger bonds except those of -ONO(2) derivatives are relatively large, which means these compounds suffice the stability request of explosives. Taking both detonation properties and sensitivities into consideration, some -NF(2) and -NO(2) derivatives may be potential candidates for HEDCs.     

Computational investigation of the heat of formation, detonation properties of furazan-based energetic materials

The heats of formation (HOFs) for a series of furazan-based energetic materials were calculated by density functional theory. The isodesmic reaction method was employed to estimate the HOFs. The result shows that the introductions of azo and azoxy groups can increase the HOF, but the introduction of azo group can increase the more HOF, when compared with azoxy group. The detonation velocities and detonation pressures of the furazan-based energetic materials are further evaluated at B3LYP/6-31G* level. Dioxoazotetrafurazan and azoxytetrafurazan may be regarded as the potential candidates of high-energy density materials because of good detonation performance. In addition, there are good linear correlations between OB and detonation velocities, and OB and detonation pressures. The energy gaps between the HOMO and LUMO of the studied compounds are also investigated. These results provide basic information for the molecular design of novel high-energy density materials.     

Molecular dynamics and kinetic study of carbon coagulation in the release wave of detonation products

We present a combined molecular dynamics and kinetic study of a carbon cluster aggregation process in thermodynamic conditions relevant for the detonation products of oxygen deficient explosives. Molecular dynamics simulations with the LCBOPII potential under gigapascal pressure and high temperatures indicate that (i) the cluster motion in the detonation gas is compatible with Brownian diffusion and (ii) the coalescence probability is 100% for two clusters entering the interaction cutoff distance. We used these results for a subsequent kinetic study with the Smoluchowski model, with realistic models applied for the physical parameters such as viscosity and cluster size. We found that purely aggregational kinetics yield too fast clustering, with moderate influence of the model parameters. In agreement with previous studies, the introduction of surface reactivity through a simple kinetic model is necessary to approach the clustering time scales suggested by experiments (1000 atoms after 100 ns, 10 000 atoms after 1 μs). However, these models fail to reach all experimental criteria simultaneously and more complex modelling of the surface process seems desirable to go beyond these current limitations.