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...     

Quality control of heat treatment of 60C2A steel bars using the electromagnetic-acoustic method

The patterns of changes in the main parameters of longitudinal and transverse waves in bars that were produced of spring steel and subjected to heat treatment under different conditions were investigated using the electromagnetic-acoustic method of ultrasound excitation and reception.     

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.     

Molecular dynamics study of nanoscale structure formation in droplet spreading on solid surfaces

Spreading of nanosized droplets was simulated on the basis of the isothermal molecular dynamics. A conclusion is made that the nanoscale droplet evolution has many common features with the macroscopic spreading. At the same time, some structure formation processes are revealed specific for the nanosized region. Observed effects include: the pyramid-like structure formation, the orientational ordering and the parquet cluster structure formation in nanodroplets composed of rod-like molecules, the replication of the structured (heterogeneous) surfaces represented by high- and low-energy segments such as striped substrates and surfaces with quadratic high- and low-energy inclusions.     

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.     

Aluminum/HMX nanocomposites: Synthesis,microstructure, and combustion

Combustion, Explosion, and Shock Waves - Aluminum particles with a diameter of ≈50 nm were synthesized by means of the Gen-Miller flow-levitation method with alumina or trimethylsiloxane...     

Comparative Analysis of Boron Powders Obtained by Various Methods. I. Microstructure and Oxidation Parameters during Heating

This paper describes a study of boron powders and powder compounds, obtained by various methods, including metallothermal, electrolytic, and borane cracking methods. The crystal state, particle size and microstructure, presence and composition of impurities, and chemical composition of the oxide layer of boron particles are profoundly investigated. The effects of the above-mentioned characteristics on the particle oxidation parameters during heating with a constant rate are analyzed. The determining influence of chemical composition of the particle surface layer on the initial temperature of their intense oxidation is established. It is shown that the maximum increase in the mass and heat release value during oxidation of the boron powders is almost independent of microstructural features, crystal state, and chemical composition of and oxide layer thickness of the particles, and cannot serve as indicators of completeness of boron oxidation during heating.     

Evaluation of residual stresses in rims of wagon wheels using the electromagnetic-acoustic method

A technique for testing residual stresses in the rims of solid-rolled wagon wheels with an ultrasonic method using the electromagnetic-acoustic method of exciting-receiving acoustic signals is described. An engineering solution that makes it possible to obtain trains of bottom signals using electromagnetic-acoustic transducers is proposed. The results from determining residual stresses in new and used wagon wheels are presented.     

Premembrane treatment of drainage waters from dumps of solid domestic wastes

We examined the efficiency of pretreatment, prior to membrane purification, of drainage waters from domestic refuse dumps using oxidants, adsorbents, coagulants, and flocculants. We determined the optimum pH values for coagulatory processes and the optimum coagulant concentrations, and found that the most effective coagulant for these drainage waters was basic aluminum sulfate. Results of our experiments on a pilot facility incorporating units for coagulation and the reverse-osmosis desalting of the refuse dump drainage waters demonstrated the possibility of obtaining a permeate that met the requirements prescribed for discharge into the sewerage system.