Detonation of energetic materials

This chapter describes experimental and theoretical approaches for understanding shock compression, low velocity initiation, hot spot formation, shock initiation and detonation of energetic materials and nanotechnology energetic materials on the femtosecond time scale and at the level of individual molecules. Particular attention is paid to models that combine chemistry, mechanics and quantum behavior. Suggestions are made for future work in key areas. 

Decomposition, Combustion, and Detonation Chemistry of Energetic Materials, Hrsg. Brill, T.B., Russel, RB., Tao, W.C., Wardle, R.B., Materials Research Society (MRS), Pittburgh, PA, USA, 1996 (Symposium Series Vol. 418)... 

Despite the many successes in the thermochemical modeling of energetic materials, several significant limitations exist. One such limitation is that real systems do not always obtain chemical equilibrium during the relatively short (nanoseconds-microseconds) time scales of detonation. When this occurs, quantities such as the energy of detonation and the detonation velocity are commonly predicted to be 10-20% higher than experiment by a thermochemical calculation. 

The physicochemical properties of explosives are fundamentally equivalent to those of propellants. Explosives are also made of energetic materials such as nitropolymers and composite materials composed of crystalline particles and polymeric materials. TNT, RDX, and HMX are typical energetic crystalline materials used as explosives. Furthermore, when ammonium nitrate (AN) particles are mixed with an oil, an energetic explosive named ANFO (ammonium nitrate fuel oil) is formed. AN with water is also an explosive, named slurry explosive, used in industrial and civil engineering. A difference between the materials used as explosives and propellants is not readily evident. Propellants can be detonated when they are subjected to excess heat energy or mechanical shock. Explosives can be deflagrated steadily without a detonation wave when they are gently heated without mechanical shock. 

In contrast to the detonation of gaseous materials, the detonation process of explosives composed of energetic solid materials involves phase changes from solid to liquid and to gas, which encompass thermal decomposition and diffusional processes of the oxidizer and fuel components in the gas phase. Thus, the precise details of a detonation process depend on the physicochemical properties of the explosive, such as its chemical structure and the particle sizes of the oxidizer and fuel components. The detonation phenomena are not thermal equilibrium processes and the thickness of the reachon zone of the detonation wave of an explosive is too thin to identify its detailed structure.[i- i Therefore, the detonation processes of explosives are characterized through the details of gas-phase detonation phenomena. 

R.S. Miller "Research on New Energetic Materials" in MRS Decomposition, Combustion, Detonation Chemistry of Energetic Materials, Brill, Russell, Tao, Wardle (eds.), 1996. 

D. H. Tsai, Proceedings of the Materials Research Society Symposium on Decomposition, Combustion and Detonation Chemistry of Energetic Materials , 418, Pittsburgh, PA, (1996) p. 281. 

A critical characteristic of energetic materials is the Chapman-Jouguet (CJ) state. This describes the chemical equilibrium of the products at the end of the reaction zone of the detonation wave before the isentropic expansion. In the classical ZePdovich-Neumann-Doring (ZND) detonation model, the detonation wave propagates at constant velocity. This velocity is the same as at the CJ point which characterizes the state of reaction products in which the local speed of sound decreases to the detonation velocity as the product gases expand. 

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