Energetic materials, structure

Structure 20 and salts 115 and 116 are formed by condensation of nitric oxide with diethylmalonate. Arulsamy and Bohle warn that this new type of compact ring structure forms dense crystals, and compounds 20, 115, and 116 are potential energetic materials which decompose violently at high temperatures <2002AGE2089>. 

Structure and Properties of Energetic Materials, Hrsg. Liebenberg, D.H., Armstrom, R.W. und Gilman, J.J., Materials Research Society (MRS), Pittsburgh, USA, 1993 (Symposium Series Vol. 293)... 

From among the different classes of compounds considered in this work, most of the computational work was done on amines, while less examples are found for nitro compounds and very few for nitroso ones. The different studies may be classified into several major areas (1) conformational analysis and structural investigation (2) spectroscopic experiments and study of chemical effects (3) investigation of chemical reactions mechanism (4) heats of formation and density calculations, especially of high energetic materials. In the following sections we will concentrate on molecular mechanics based research studies, or on such where molecular mechanics calculations played a... 

Energetic materials with strained or caged structures are often much more difficult to synthesize compared to their open chain counterparts. This presents a further challenge to researchers of new energetic materials - while new compounds can be synthesized on a laboratory scale, and their properties and performance tested, the complexity of the synthetic routes may render their use as explosives nonfeasible. This particularly applies to polynitropolycyclic hydrocarbons because the direct nitration of these hydrocarbons is not a feasible route of introducing nitro groups without considerable decomposition. 

Analyses of the structures and properties of a large number of energetic materials reveal that a combination of amino and nitro groups in a molecule often leads to better thermal stability, lower sensitivity to shock and impact, and increased explosive performance because of an increase in crystal density. Such observations are attributed to both intermolecular and intramolecular hydrogen bonding interactions between adjacent amino and nitro groups. Some modern triazole-based explosives have been designed and synthesized with this in mind. 

When reactant R of an energetic material reacts to generate product P, heat is released (or absorbed). Since the chemical bond energy of R is different from that of P, the energy difference between R and P appears as heat. The rearrangement of the molecular structure of R changes the chemical potential. The heat of reaction at... 

A schematic representation of the combustion wave structure of a typical energetic material is shown in Fig. 3.9 and the heat transfer process as a function of the burning distance and temperature is shown in Fig. 3.10. In zone I (solid-phase zone or condensed-phase zone), no chemical reactions occur and the temperature increases from the initial temperature (Tq) to the decomposition temperature (T ). In zone II (condensed-phase reaction zone), in which there is a phase change from solid to liquid and/or to gas and reactive gaseous species are formed in endothermic or exothermic reactions, the temperature increases from T to the burning surface temperature (Tf In zone III (gas-phase reaction zone), in which exothermic gas-phase reactions occur, the temperature increases rapidly from Tj to the flame temperature (Tg). 

Molecules in which fuel and oxidizer components are chemically bonded within the same structure are suitably predisposed for the formulation of energetic materials. Nitropolymers are composed of O-NO2 groups and a hydrocarbon structure. The bond breakage of O-NO2 produces gaseous NO2, which acts as an oxidizer fragment, and the remaining hydrocarbon structure acts as a fuel fragment. NC is a typical nitropolymer used as a major component of propellants. The propellants composed of NC are termed nitropolymer propellants . 

HMX and RDX are energetic materials that produce high-temperature combustion products at about 3000 K. If one assumes that the combustion products at high temperature are HjO, Nj, and CO, rather than COj, both nitramines are considered to be stoichiometricaUy balanced materials and no excess oxidizer or fuel fragments are formed. When HMX or RDX particles are mixed with a polymeric hydrocarbon, a nitramine pyrolant is formed. Each nitramine particle is surrounded by the polymer and hence the physical structure is heterogeneous, similar to that of an AP composite pyrolant... 

Materials synthesis is a necessary component in the development of advanced technologies for national security and homeland defense. For instance, new composites, nanoscale molecules and compounds, and polymers are needed for tougher, explosion- or puncture-resistant materials that can be employed in buildings, garments, bridges, and other products and structures. Personal protective materials could be enhanced with new chemical adsorbents filter materials, impermeable membranes, artificial sutures, and improved energetic materials for... 

There have been a number of model studies on these types of compounds with computational analysis being applied to assist in the understanding of molecular structure and reactivity as well as in the estimation of the potential of molecules to act as high energetic materials or molecular building blocks. 

The heat transfer in the combustion wave structure of an energetic material is illustrated in Fig. 3.10. The heat flux feedback from zone III to zone II by conductive heat transfer, = kg (dTIdx), is given by Eq. (3.46), and the heat flux feedback from zone II to zone I by conduction heat transfer, dT/dx), is given by... 

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