Critical parameters of a micro-hotspot model of the laser-pulse initiation of the explosive decomposition of energetic materials

The work continues a series of studies of the micro-hotspot model a thermal explosion. The dependences of the critical energy fluence and the temperature of the reaction kernel in pentaerythritol tetranitrate (PETN) on the radius of aluminum nanoparticles at half-maximum pulse durations of 10 to 150 ns are calculated. For each pulse duration, there is an optimal nanoparticle radius at which the critical energy fluence is minimal. The dependences of these parameters on the pulse duration are derived. It is shown that there is a universal relationship, independent of the pulse duration, between the normalized critical energy fluence and the nanoparticle radius.     

Analysis of conditions for determining the thermophysical characteristics of energetic materials by the laser pulse method

An analysis of conditions for determining the thermophysical characteristics of energetic materials by the laser pulse method is performed. Based on the results of numerical solution of the heat conduction problems for a sample of a material irradiated with a short heating laser pulse corresponding to actual experimental conditions, the time dependences on the sample surface temperature are determined. The heat pulse duration required to determine the thermophysical properties of materials and the ignition delay time are compared. It is shown that the determination of the thermophysical characteristics of a typical energetic material by the laser pulse method is possible at pulse durations of no longer than 0.24 s.     

An experimental setup with controllable tuning parameters for studying the Kondo systems

The Kondo physics has been studied since the 1960 s in condensed matter physics[1,2],which is mainly determined by two competing factors namely the Kondo effect and the Ruderman-Kittel-Kasuya-Yosida(RKKY)interaction.     

Inhibition of explosive decomposition of acetylene

An experimental study of the inhibition of the exothermic decomposition of acetylene diluted with household propane+butane mixture and hydrogen was performed. Acetylene-inhibitor mixtures were heated behind reflected shock waves. The shock wave was generated by the detonation wave initiated in a stoichiometric acetylene-oxygen mixture. The minimum volumetric inhibitor concentrations capable of suppressing the self-decomposition of acetylene were determined.     

An experimental setup with controllable tuning parameters for studying the Kondo systems

We investigate the effects of high pressure and physical aging on the boson peak and thermal expansion of a typical metallic glass. Specifically, the thermal expansion coefficient and boson peak intensity monotonically decrease during physical aging.With the increase of high pressure, the boson peak intensity and the thermal expansion coefficient coincidently experience an incipient decrease and then a subsequent increase. The boson peak intensity shows an approximately linear relationship with the thermal expansion coefficient. The thermal expansion can be affected by structural relaxation or rejuvenation, which can reflect the flow units variation and atomic packing of a metallic glass. Our results indicate a direct link between structural relaxation or rejuvenation and fast boson peak dynamics, providing insights into the boson peak behavior and structural heterogeneity of metallic glasses.     

Curvilinear deflagration of energetic materials

The effects of material interface curvature on deflagration of a homogeneous solid energetic material (EM) is studied in a limit when the radius of curvature is much larger than the deflagration front thickness. Under the assumption of quasi-steady burning, a method of matched asymptotics is employed do derive first-order curvature corrections to the mass flux across the gas–solid interface as well as to the interface temperature. As an illustration, a problem of quasi-steady spherical particle deflagration is solved numerically and the simulation results are used to verify those obtained through asymptotic analysis. An algorithm for a fully-coupled unsteady solver suitable for EM deflagration simulation is presented. Numerical solution of the unsteady spherical particle deflagration is used to show that the assumption of quasi-steady deflagration is valid.     

Absorption spectra and spectral-kinetic characteristics of the fluorescence of Sanguinarine in complexes with polyelectrolytes and DNA

The absorption spectra and stationary and time resolved fluorescence spectra of the isoquinoline alkaloid sanguinarine are studied in aqueous media and during interactions with synthetic polyelectrolytes (polystyrene sulfonate and polyallylamine) and a natural polyelectrolyte (DNA).     

The explosive working of materials in the USSR

Abstract

The studies of the processes related to working the materials by explosive energy were initiated in the Soviet Union during the World War II. The process of armour piercing by shaped charges developed at the beginning of the twentieth century in the United States and in Germany was investigated. The investigations were carried out by a research team of Academician M. A. Lavrentiev in Kiev in 1944–1946 and several modifications of the explosive welding phenomenon were detected'. In the mid-fifties, investigation of explosive powder compaction were begun in Moscow by Professor Yu. N. Riabinin². In the early sixties, M. A. Lavrentiev undertook a large-scale research program on explosive hardening and welding in Novosibirsk¹. Later, explosive powder compaction was also included into the research program³. The first attempts to investigate the strength of the explosive chambers relate to the same period⁴.     

Modernized setup for studying the interaction of ions with energies to 40 keV with the surface

A modernized setup for studying the ion-surface interaction is briefly described. The main ion channel implemented on the “Large MEPhI mass monochromator” with an ion energy range of 1–40 keV makes it possible to obtain ion beams with (EM/Z) ≤ 4000 keV × a.m.u. Operation with intermediate-energy hydrogen ions allows obtaining information on the thickness of layers of atoms with masses differing from substrate atoms, by analyzing energy spectra of protons scattered from two- or three-layer targets. The use of new digital power units and relevant control programs also allows automation of the ion beam control and makes it possible to perform ion-beam experiments using preliminarily developed irradiation programs.     

Computational modelling of multi-material energetic materials and systems

ABSTRACT

In this paper, we present a systematic roadmap for developing a robust and parallel multi-material reactive hydrodynamic solver that integrates historically stable algorithms with new and current modern methods to solve explosive system design problems. The Ghost Fluid Method and Riemann solvers were used to enforce appropriate interface boundary conditions. Improved performance in terms of computational work and convergence properties was achieved by modifying a local node sorting strategy that decouples ghost nodes, allowing us to set material boundary conditions via an explicit procedure, removing the need to solve a coupled system of equations numerically. The locality and explicit nature of the node sorting concept allows for greater levels of parallelism and lower computational cost when populating ghost nodes. Non-linear numerical issues endemic to the use of real Equations of State in hydro-codes were resolved by using more thermodynamically consistent forms allowing us to accurately resolve large density gradients associated with high energy detonation problems at material interfaces. Pre-computed volume tables were implemented adding to the robustness of the solver base.     

Flame structure and combustion chemistry of energetic materials

A review of experimental studies of the structure of the flame of a number of energetic materials (EMs), such as ammonium perchlorate, ammonium dinitramide, RDX, HMX, and some model composite propellants on their bases, is presented. Experimental techniques for studying the flame structure of EMs, probe mass spectrometry and the thermocouple method, are described. An analysis of experimental data on the flame structure and combustion chemistry and a comparison of them with simulations within the framework of modern mechanisms of chemical reactions in EM flames are performed.     

Computational design of tetrazolone‐based high‐energy density energetic materials: Property prediction and decomposition mechanism

The density functional theory methods are used to design a series of new highly energetic tetrazolone‐based molecules by the combination of the linked tetrazolone framework and versatile substitutes. The molecular and electronic structures, physicochemical, and energetic properties were analyzed and predicted. The decomposition mechanisms were computationally simulated, and 3 potential decomposition channels were proposed. These newly designed tetrazolone‐based compounds show high densities (up to 2.08 g/cm³) and highly positive heats of formation (407.0‐1377.9 kJ/mol) due to all right content of nitrogen and oxygen. Most of them exhibit good detonation velocity (8.31‐9.62 km/s) and detonation pressure (32.40‐43.86 GPa), and some are comparative to excellent explosive CL‐20. Results show that compounds 6 , 10 , 11 , 12 , 15 , 16 , 17 , 22 , 23 , and 24 own superior detonation performance than widely used explosive HMX and may be promising candidates of green high‐performance energetic materials.     

飞秒激光精细加工含能材料

介绍了飞秒激光脉冲特点及其与物质相互作用机理, 论述了飞秒激光微加工含能材料技术特点及优势, 综述了飞秒激光加工含能材料技术及发展. 讨论了飞秒激光加工含能材料技术进一步发展所需的实验与理论研究工作以及相应的研究方案和关键技术. 关键词： 飞秒激光微加工 含能材料 冲击温度 冲击压强     

Development of a new experimental setup for studying collisions of keV-electrons with thick and thin targets

Development of a new lectron-recoil ion/photon coincidence setup for investigating some of the electron induced collision processes, such as electron bremsstrahlung, electron backscattering, innershell excitation and multiple ionization of target atoms/molecules in bombardment of electrons having energies from 2.0 keV to 30.0 keV with solid and gaseous targets is described. The new features include the use of a compact multipurpose scattering chamber, a time-of-flight spectrometer for detection of multiply charged target ions, a 45°-parallel plate electrostatic analyzer for measuring energy and angle of the ejected electrons, a room temperature high resolution Si-PIN photo diode X-ray detector for counting the collisionally induced photons, a coincidence data acquisition system consisting of a 200 MHz Pentium based 8K-multichannel analyzer and a standard network of a fast/slow coincidence electronics. In particular, the details of design, fabrication and assembly of indigenous components employed in the setup are presented. Selected experiments planned with the setup are mentioned and briefly discussed. A report on performance, optimization, efficiency, time resolution etc. of the time-of-flight (TOF) spectrometer and that of the 45°-parallel plate electrostatic analyzer (PPEA) is presented. Test spectra of electron-recoil ion coincidences, energy distribution of ejected electrons and characteristic plus non-characteristic X-ray spectrum are illustrated to exhibit the satisfactory performance of the developed setup.     

Promising energetic materials composed of nanosilicon and solid oxidizers

A method for production of mechanically activated energetic compositions consisting of nanosilicon and solid inorganic oxidizers is developed. For the compositions prepared, both high-speed burning and detonation are observed. The propagation of the reaction is accompanied by a high energy release, comparable to the heat of explosion of aluminized high explosives. The compositions are highly sensitive to thermal stimuli and capable of rapid deflagration-to-detonation transition. The results obtained in the work suggest that nanosilicon-based formulations as promising energetic materials for a wide range of applications, from initiating compositions in blasting caps to compositions for small charges in microsystem devices.     

不同材质的偏振成像特性实验研究

偏振成像具有很多强度成像所不具备的优势,在某种特定背景下能够更加突显目标,是研究地表、大气等领域的良好辅助手段。在红（670 nm）、绿（530 nm）、蓝（450 nm）这3种比较典型的可见光波段下,采用旋转偏振片求取斯托克斯矢量的方法,分别对草地,石板,沥青地面,玻璃,橡胶和铁板6种材质做了偏振特性成像实验,并对它们的偏振度以及偏振度对比度进行了详细分析。实验结果表明,在某种背景下,目标的某些部分在强度成像中不易观测到,而偏振图像具有足够的亮度信息,包含了丰富的细节信息,更加易于人眼识别;另外,偏振成像特性与目标材质、观测时刻、成像波段均有较大关系。     

Density-based kinetics for mesoscale simulations of detonation initiation in energetic materials

In this work we present one- and two-dimensional mesoscale simulations of detonation initiation in energetic materials. We solve the reactive Euler equations, with the energy equation augmented by a power deposition term. The reaction rate at the mesoscale is modelled using a density-based kinetics scheme, adapted from standard ‘Ignition and Growth’ models. The deposition term is based on previous results of simulations of void collapse at the microscale, modelled at the mesoscale as hot spots. For an isolated hot spot in a homogeneous medium, it is found that a critical size of the hot spots exists. If the hot spots exceed the critical size, initiation of detonation can be achieved. For sub-critical hot-spot sizes, we show that it takes a collection of hot spots to achieve detonation. We also carry out two-dimensional mesoscale simulations of random packs of HMX crystals in a binder, and show that the transition between no detonation and detonation depends on the number density of the hot spots, the initial radius of the hot spot, the post-shock pressure of an imposed shock, and the amplitude of the power deposition term.