Energetic Materials Based on W/PTFE/Al: Thermal and Shock-Wave Initiation of Exothermic Reactions

The parameters of combustion synthesis and shock-wave initiation of reactive W/PTFE/Al compacts are investigated. Preliminary thermodynamic calculations showed the possibility of combustion of the W/PTFE/Al system at high adiabatic temperatures (up to 2776 °C) and a large proportion of condensed combustion products. The effect of the Al content (5, 10, 20, and 30 wt%) in the W/PTFE/Al system on the ignition and development of exothermic reactions was determined. Ignition temperatures and combustion rates were measured in argon, air, and rarefied air. A correlation between the gas medium, rate, and temperature of combustion was found. The shock initiation in W/PTFE/Al compacts with different Al content was examined. The extent of reaction in all compacts was studied by X-ray diffraction. The compositions with 10 and 20 wt% Al showed the highest completeness of synthesis after combustion and shock-wave initiation.

EFFECT OF BORON ON THE COMBUSTION CHARACTERISTICS OF METALLIZED HIGH-ENERGY MATERIALS

The paper presents the results of thermodynamic calculations of the effect of pure boron additives on combustion characteristics of high-energy materials (HEM) based on ammonium perchlorate, ammonium nitrate, active fuel-binder, and powders of aluminum Al, titanium Ti, magnesium Mg, and boron B. The combustion parameters and the equilibrium composition of condensed combustion products (CCPs) of HEM model compositions were obtained with thermodynamic calculation program “Terra.” The compositions of solid propellants with different ratios of metals (Al/B, Ti/B, Mg/B, and Al/Mg/B) were considered. The combustion temperature Tad in a combustion chamber, the vacuum specific impulse J at the nozzle exit, and the mass fraction ma of the CCPs for HEMs were determined.

IGNITION, COMBUSTION, AND AGGLOMERATION OF HIGH-ENERGY MATERIALS BASED ON ALUMINUM AND BORON

The burning rate control of the high-energy materials (HEM) is mainly achieved by introducing the catalysts in composite solid propellant as well as by partial or complete replacement of ammonium perchlorate (AP) and ammonium nitrate by nitramines that change the equivalence ratio of formulation, or by varying the particle size of oxidizer and metal fuels. Promising metallic fuels are highly dispersed aluminum powders, which are characterized by different dispersity and passivation method, as well as bimetallic powders or mixtures of aluminum and other metals, their alloys, and metal powders with various coatings. In this study, the Al-based, Al/B-based, and Al/Fe-based HEM compositions have been used for comparative analysis of the ignition, combustion, and agglomeration characteristics. At the use of boron additive in the Al-based HEM, the ignition time is decreased by a factor of 1.2-1.4 and the burning rate is virtually unchanged as compared with that for the Al-based HEM. However, the agglomeration is significantly enhanced, which is manifested in the increase in the agglomerate particle content in condensed combustion products (CCP), increase in the agglomerate mean diameter, and increase in the unburned metal fraction in agglomerates.

Morphologic, chemical, and spectral analyses of combustion products of micro- and nano-dispersed particles of aluminium borides

This study presents the findings of an investigation of flame propagation in air suspension of nanodispersed polyboride particles, and provides spectral, morphological, and mass-spectrometric analyses of condensed combustion products generated during an air suspension combustion.

Transformation of Combustion Nanocatalysts inside Solid Rocket Motor under Various Pressures

In this paper, the dependences of the morphology, particle sizes, and compositions of the condensed combustion products (CCP) of modified double-base propellants (1,3,5-trimethylenetrinitramine (RDX) as oxidizer) on the chamber pressure (<35 MPa) and nickel inclusion have been evaluated under a practical rocket motor operation. It has been shown that higher pressure results in smaller average particle sizes of the CCPs. The CCPs of Ni-containing propellants have more diverse morphologies, including spherical particles, large layered structures, and small flakes coated on large particles depending on the pressure. The specific surface area (SSA) of CCPs is in the range of 2.49 to 3.24 m2 g−1 for propellants without nickel are less dependent on the pressure, whereas it is 1.22 to 3.81 Ni-based propellants. The C, N, O, Al, Cu, Pb, and Si are the major elements presented on the surfaces of the CCP particles of both propellants. The compositions of CCPs from Ni-propellant are much more diverse than another one, but only three or four major phases have been found for both propellants under any pressure. The metallic copper is presented in CCPs for both propellants when the chamber pressure is low. The lead salt as the catalyst has been transformed in to Pb(OH)Cl as the most common products of lead-based catalysts with pressure lower than 15 MPa. When pressure is higher than 5 MPa, the nickel-based CCPs has been found to contain one of the following crystalline phases: Pb2Ni(NO2)6, (NH4)2Ni(SO4)2·6H2O, C2H2NiO4·2H2O, and NiO, depending on the pressure.

Effect of organic coatings of nanoaluminum on the burning rate of mixed compositions

Mixed compositions based on ammonium perchlorate, inert fuel-binder and nanosized aluminum, encapsulated with organic compounds, have been experimentally studied. The study of aluminum powders using scanning electron microscopy and transmission electron microscopy was carried out. The oxidation of aluminum powders was investigated by differential thermal and thermogravimetric methods. The chemical composition of the condensed products was determined by X-ray diffraction. The laws of mixed composition combustion were determined in a wide pressure range. The possibility of controlling the burning rate and the content of condensed combustion products by using encapsulated nanoaluminum is shown.

Exploratory investigations on metal-based fuels for air-breathing propulsion

Air-breathing solid fueled propulsion devices represent rugged, cheap, and rather simple options, out of the ramjet (RJ) category, which can contribute to volume containment and structural weight reduction. In the case of a ducted rocket, a fuel-rich propellant is burned in a primary combustion chamber and part of the oxidizer is taken from the atmosphere to complete the combustion inside a ram burner before exhaust. The use of metal additives contributes to the development of high-energy density materials, featuring better volumetric specific impulse. Metal powders are characterized by high energetic content per unit volume but can feature issues of difficult ignition, generation of condensed combustion products (CCPs), and incomplete combustion. The present work discusses a series of exploratory investigations on aluminum-based pyrolants. Thermochemical analyses, calorimetric investigations, and combustion tests will be considered, looking at improvements introduced by metal addition.