Prospects of Using Boron Powders As Fuel. III. Influence of Polymer Binders on the Composition of Condensed Gasification Products of Model Boron-Containing Compositions

Combustion, Explosion, and Shock Waves - The effect of polymer binders on the thermal behavior, combustion, and composition of condensed gasification products of model boron-containing compositions...     

Nanomaterials for Heterogeneous Combustion

Nanophase materials and nanocomposites, characterized by an ultra fine grain size (less than 100 nm) have attracted wide spread interest in recent years by virtue of their unusual mechanical, electrical, optical, magnetic, and energetic properties. Studies have shown that the thermal behavior of nano‐scaled materials is quite different from micron‐sized powders. Nanosized metallic and explosive powders have been used as solid propellant and explosive mixtures to increase efficiency. At the same time recent studies reveal that the presence of nanosized metals in propellants does not necessary translate into an increased burning rate and burning temperature. The reasons of this effect are far from being clear. This paper presents a new approach to the production of nanocomposites of some energetic materials – ammonium nitrite, cyclotrimethylene trinitramine (RDX), and aluminum – by the vacuum co‐deposition technique. The thermal behavior of the synthesized nanopowder and nanocomposites is investigated. A substantial difference in burning rate of RDX nanopowder has been found in comparison to micron‐sized material. Experimental results allow investigating the effects of nanosized materials on the combustion characteristics.     

Nanosized components of energetic systems: Structure,thermal behavior,and combustion

Ultrafine and nanosized powders of oxidizers and metals are considered as promising ingredients for the development of new highly effective solid rocket propellants. An ultrafine ammonium perchlorate (AP) powder and nanosized aluminum were produced by mechanical activation and investigated using electron and atomic force microscopy and X-ray powder and thermal analyses. It is shown that the activation energy of nanoaluminum oxidation is considerably lower than that for the micron-size powder, and the activation energy of the high-temperature decomposition for standard AP exceeds that for ultrafine AP. The exponent in the burning rate law decreases, and the burning rate increases by an order of magnitude if micron-sized aluminum is completely replaced by nanoaluminum in stoichiometric compositions containing ultrafine AP. __________ Translated from Fizika Goreniya i Vzryva, Vol. 43, No. 1, pp. 60–65, January–February, 2007.     

Novel Melt‐Castable Energetic Pyrazole: A Pyrazolyl‐Furazan Framework Bearing Five Nitro Groups

Continuing advances in energetic pyrazole construction foster further its rational use. This work establishes an approach for the first synthesis of nitropyrazole that bear both furazan and trinitromethyl moieties. The approach to the installation of the C(NO₂)₃ group exploits the destructive nitration of N‐acetonyl group. The target 3‐(3,4‐dinitro‐1‐(trinitromethyl)‐1H‐pyrazol‐5‐yl)‐4‐methylfurazan ( 6 ) has promising explosive properties.     

5‐Amino‐3,4‐dinitropyrazole as a Promising Energetic Material

The nitrogen‐rich energetic compound 5‐amino‐3,4‐dinitropyrazole (5‐ADP) was investigated using complementary experimental techniques. X‐ray diffraction indicates the strong intermolecular hydrogen bonding in 5‐ADP crystals. Compound exhibits low impact sensitivity (23 J) and insensitivity to friction. The activation energy of thermolysis determined to be 230±5 kJ mol⁻¹ from DSC measurements. Accelerating rate calorimetry indicates the lower thermal stability (173 °C) of 5‐ADP than that of RDX, which is probably the main concern about using this compound. 5‐ADP also exhibits good compatibility with common energetic materials (viz. TNT, RDX, ammonium perchlorate), including an active binder. The burning rate of 5‐ADP monopropellant is higher than that of benchmark HMX, while the pressure exponent 0.51±0.04 is surprisingly low. Addition of ammonium perchlorate does not affect the pressure exponent of 5‐ADP, while the burning rate increases. The 5‐amino‐3,4‐dinitropyrazole exhibits a notable combination of combustion performance, low sensitivity, and good compatibility, which renders it as a promising energetic material.     

Processing of experimental data using discretization of their domains

A method for processing observation data based on their discretization and graphical analysis is proposed. The purpose of the processing is to determine and model the functional relationship between the inputs and output of an experimental object. The case of a series of experiments is considered.     

Synthesis of Energy-Rich Nanomaterials

For the first time, vacuum condensation was used to prepare nanomaterials for high-energy systems. At the first stage of the study, nanodispersed ammonium nitrate and RDX were obtained, and chemically pure crystallites of either substance with a mean size of 50 nm were subsequently extracted from the powders obtained. At the second stage, simultaneous vacuum evaporation and condensation of the two components were used to obtain a composite material containing nanocrystal-force microscopy were employed to identify the phase composition of the crystallites and determine their morphology and sizes. The crystallite size of the synthesized two-component composite material is shown to be no greater than 100 nm. Key words: nanoparticles, nanocomposites, energy materials, vacuum condensation, combustion.     

Influence of Particle Size and Mixing Technology on Combustion of HMX/Al Compositions

In this work, two widely used components of high‐energy condensed systems – HMX and aluminium – were studied. Morphology, thermal behaviour, chemical purity and combustion parameters of HMX as a monopropellant and Al/HMX as a binary system were investigated using particles of different sizes. It was shown that in spite of the differences in composition and particle size, combustion velocities are almost identical for micrometer‐sized HMX (m‐HMX) and ultrafine HMX (u‐HMX) monopropellants under pressure from 2 to 10 MPa. Replacement of the micrometer‐sized aluminium with ultrafine one in the system with m‐HMX leads to a burning rate increase by a factor of 2.5 and the combustion completeness raise by a factor of 4. Two mixing techniques to prepare binary Al/HMX compositions were applied: conventional and ‘wet’ technique with ultrasonic processing in liquid. Applying wet mixing results in a burning rate increase of 18% compared to the conventional mixing for systems with ultrafine metal. The influence of the component's particle size and the composition microstructure on the burning rate of energetic systems is discussed and analysed.