Shock-induced reaction

Preliminary analyses were carried out by the autliors, and a tentative DM method was developed. Using tliis tentative method some practical examples were investigated, among tliem the shock-induced reaction of Al + Ni fine powder mixture and the stress profile of HMX explosive powders under the action of shock waves. The calculated results using this model are in better agreement... 

W.G. Von Holle, C.M. Traver, Temperature measurements of shocked explosives by time resolved infrared radiometry-a new technique to measure shock-induced reaction. Seventh Symposium on Detonation, Annapolis, Maryland, 993-1003. 

Large-scale molecular dynamics simulations are producing information on shock-induced reactions on picosecond (ps) to nanosecond (ns) time scales and approaching micron spatial scales. We describe experiments using ultrafast laser methods to produce experimental data on similar time and space scales to help benchmark the simulations as well as motivate their expansion to larger scales and more complicated materials. 

R Ward, N Thadhani, P-A Persson. Shock-induced reaction synthesis-assisted processing of ceramics. In Ref. 8, p 294. 

That this is not always the case should be expected. In fact, if it was not for heterogeneous localization of some flow phenomena, it would be very diflicult to initiate secondary explosives, or to effect shock-induced chemical reactions in solids. Heterogeneous shear deformation in metals has also been invoked as an explanation for a reduction in shear strength in shock compression as compared to quasi-isentropic loading. We present here a brief discussion of some aspects of heterogeneous deformation in shock-loaded solids. 

Along a different line of research on shock compression of solids, namely, recovery experiments, great progress was also being made. Shock-induced recovery-type chemical reactions in encapsulated samples were first reported by Riabinin in 1956. Shock-induced metallographic transformation and the observation of twin bands in iron were first reported by Smith in 1958. Another major breakthrough was the shock-induced synthesis of diamond in 1961 by DeCarli and Jamieson. 

In this chapter The background of shock-induced solid-state ehemistry eonceptual models and mathematical models chemical reactions in shock-compressed porous powders sample preservation. 

In most cases of interest, shock-induced chemical reactions in solids are studied in mixtures of powders of the potential reactants. In the earlier description of conceptual models it was emphasized that the pores provide space in which the potential reactants can be more intimately mixed in order... 

Fig. 8.1. Shock-induced solid state chemical synthesis of a zinc ferrite has been studied over a wide range of temperature and pressure. The figure shows the location of conditions for which the reaction has been studied.

This chapter presents detailed and thorough studies of chemical synthesis in three quite different chemical systems zinc ferrite, intermetallic, and metal oxide. In addition to different reaction types (oxide-oxide, metal-metal, and metal oxide), the systems have quite different heats of reaction. The oxide-oxide system has no heat of reaction, while the intermetallic has a significant, but modest, heat of reaction. The metal oxide system has a very large heat of reaction. The various observations appear to be consistent with the proposed conceptual models involving configuration, activation, mixing, and heating required to describe the mechanisms of shock-induced solid state chemistry. 

Even in J-type shock models, it is not appropriate to use thermal rate coefficients because the internal degrees of freedom will cool rapidly (via radiation) in the low density medium, whereas the translational degree of freedom will cool much more slowly. Appropriate rate coefficients are then those in which only translation is strongly excited such rate coefficients can be considerably lower than thermal rates for systems in which vibrational energy is the most efficient at inducing reaction. 

Although thermal decomposition (and runaway) is often identified with the inherent reactivities of the chemicals involved, it must be emphasized that hazards can arise from induced reactions as discussed in Chapter 2. These induced reactions may be initiated by heat, contamination, or mechanical means (e.g., shock, friction, electrostatic spark). 

Gas-phase results provide insight into the reaction pathways for isolated HE molecules however, the absence of the condensed-phase environment is believed to affect reaction pathways strongly. Some key questions related to condensed-phase decomposition are as follows (1) How do the temperature and pressure affect the reaction pathways (2) Are there temperature or pressure-induced phase-transitions that play a role in the reaction pathways that may occur (3) What happens to the reaction profiles in a shock-induced detonation These questions can be answered with condensed-phase simulations, but such simulations would require large-scale reactive chemical systems consisting of thousands of atoms. Here we present results of condensed-phase atomistic simulations, which are pushing the envelope toward reaching the required simulation goal. 

Shock-induced Chemical Reactions in Heterogeneous Multi-Material Powder Mixtures. 

In thermal reactions at pressures above 10 torr, there is much evidence (21) that CH3 reacts with 02 to produce CH20 and HO radicals above about 400°C. Furthermore, Miyama and Takeyama (31) monitored HO production in the shock-induced oxidation of CH4 and observed that the induction time for HO production had an activation energy of 21.5 kcal. per mole. Reaction 3 may proceed with a 21 kcal. per mole activation energy, or HO production may be via... 

Planned experiments on shock-induced chemical reactions and detonations of explosives will be carried out with the nonlinear Raman techniques. Heterodyne detection of the transient products of such rapid reactions seems the most promising. 

Develop normally and are healthy. No difference in their reaction to endotoxin shock, however resist the lethal effects of shock induced by platelet-activating factor. Inflammation induced by arachidonic acid is markedly reduced (Chen et al. 1994 Argentieri et al. 1994). 

Many borides can be synthesized by novel synthetic methods, inclnding shock-induced chemical reactions, mechanical alloying by ball milling, and self-propagating high-temperature synthesis. In these methods, intimately mixed elemental powders are brought to react by a rapid pressure increase, mechanical deformation including local... 

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