Shock heating

Fiber-Optic Pins. In one version of the fiber-optic pin (Benjamin et al., 1984), a small microballoon, 0.25 mm in diameter, filled with a noble gas such as argon or xenon is attached to the end of an optical fiber. When the pin is impacted, the shock heats the gas in the microballoon producing a flash which is channeled to a recording system via optical fibers. Some of the useful features of this pin are... 

Shock-wave loading of solids is normally accomplished by either projectile impact, such as produced by guns or by explosives. The shock heating and compression of solids covers a wide range of temperatures and densities. For example, the temperature may be as high as a few electron volts (1 eV =... 

Chemical Reactivity - Reactivity with Water No reaction Reactivity with Common Materials Avoid contamination with combustible materials, various inorganic and organic acids, alkalies, alcohols, amines, easily oxidizable materials such as ethers, or materials used as accelerators in polymerizations reactions Stability During Transport Extremely explosion-sensitive to shock, heat and friction. Self-reactive Neutralizing Agents for Acids and Caustics Not pertinent Polymerization Not pertinent inhibitor of Polymerization Not pertinent. 

Ignition of Clouds of Particles in Shock Heated Oxygen , ProcRoySoc(London), 62 (1967)... 

Pb Azide (LA), which is the most important expl used in detonators (Ref 11), although extremely sensitive to shock, heat, and friction, is not sufficiently sensitive to stab action to insure 100% reliability in firing from the stab action. Consequently, the priming mixt is used as a first-fire layer in these units. RDX (cyclotri-methylenetrinitramine), also known as Cyclo-nite, is contained as the output charge of the typical stab detonator. Its output results in a detonation of other expls (Ref 11)... 

Extremely sensitive to shock, heat or minor friction, it has exploded very violently when touched with a glass rod or spatula. 

It must be handled with care because it may explode or become incandescent on sudden heating or shock. Heating at 207min caused a violent explosion at around 120°C [1]. Preparative and handling precautions have been detailed [2],... 

The nitride explodes violently on exposure to shock, heat, water or dilute acids. 

A pre-supernova model of a 9Mq star is taken from Nomoto [3], which forms a 1.38 Mq O-Ne-Mg core. We link this core to a one-dimensional implicit La-grangian hydrodynamic code with Newtonian gravity. The equation of state of nuclear matter (EOS) is taken from Shen et al. [4]. We find that a very weak explosion results, where no r-processing is expected. In order to examine the possible operation of the r-process in the explosion of this model, we artificially obtain an explosion with a typical energy of 1051 ergs by application of a multiplicative factor (= 1.6) to the shock-heating term in the energy equation. 

Explosive A materials that releases pressure, gas, or heat suddenly when subjected to shock, heat, or high pressure. 

Studies82 of the visible emission from shock-heated CS2 confirm this the temperature dependence of the emission shows that the upper state involved lies ap-... 

The thermal decomposition of N02 has been studied222-224 in the temperature range 1400-2300 °K by the shock-tube technique. Changes in the concentration of N02 in shock-heated argon-diluted N02 were monitored by visible absorption222 or visible emission224 spectrophotometry. The data fitted a complex rate law of the form... 

S02 is a very stable oxide and its thermal decomposition is only measurable at the very high temperatures attained in a shock tube. A study357 of the time-dependence of light emission from shock-heated S02/Ar mixtures in the region of 3000 °K has shown that S02 is removed in accordance with a sigmoid-shaped concentration-time curve typical of a chain or autoaccelerated reaction. The induction period observed357 prior to the onset of detectable decomposition corresponded closely with the time for the formation of a fixed concentration of O (or SO) calculated from the rate expression (Table 24) for the unimolecular decomposition... 

Emission from shock-heated S02 arises from three electronically excited states 3B1, 1B2, 1B1, populated by collisions from the 1A1 ground state and, for finite extents of dissociation, by the recombination of O and SO360. Equilibrium between the emitting states and the ground state... 

The decomposition of dinitrogen tetrafluoride in shock-heated nitrogen has also been investigated146. At 400 °C and a total concentration of 7 x 10 2 mole. I-1 the apparent first-order rate coefficient, kss,... 

Methyl, ethyl and propyl perchlorates, readily formed from the alcohol and anhydrous perchloric acid, are highly explosive oils, sensitive to shock, heat and friction [1], Many of the explosions which have occurred on contact of hydrox-ylic compounds with cone, perchloric acid or anhydrous metal perchlorates are attributable to the formation and decomposition of perchlorate esters [2,3,4], Safe procedures for preparation of solutions of 14 sec-alkyl perchlorates are described. Heated evaporation of solvent caused explosions in all cases [5], l-Chloro-2-propyl, iram-2-chlorocyclohexyl, l-chloro-2-propyl, 1,6-hexanediyl, hexyl, and 2-propyl perchlorates, prepared by a new method, are all explosive oils [6],... 

Most of the isolated diacyl (including sulfonyl) peroxides are solids with relatively low decomposition temperatures, and are explosive, sensitive to shock, heat or friction. Several, particularly the lower members, will detonate on the slightest disturbance. Autocatalytic (self-accelerating) decomposition, which is promoted by tertiary amines, is involved [1]. Solvents suitable for preparation of safe solutions of diacetyl, dipropionyl, diisobutyryl and di-2-phenylpropionyl peroxides are disclosed [2], The class is reviewed, including hazards and safety measures [3], Cyclic diacyl peroxides are more stable, but scarcely to be trusted. Individually indexed compounds are ... 

A few diazonium salts are unstable in solution, and many are in the solid state. Of these, the azides, chromates, nitrates, perchlorates (outstandingly), picrates, sulfides, triiodides and xanthates are noted as being explosive, and sensitive to friction, shock, heat and radiation. In view of their technical importance, diazonium salts are often isolated as their zinc chloride (or other) double salts, and although these are considerably more stable, some incidents involving explosive decomposition have been recorded. 

Rarefaction waves are generated circumferentially at the tube as the detonation leaves then they propagate toward the tube axis, cool the shock-heated gases, and, consequently, increase the reaction induction time. This induced delay decouples the reaction zone from the shock and a deflagration persists. The tube diameter must be large enough so that a core near the tube axis is not quenched and this core can support the development of a spherical detonation wave. 

On pp 289-310 (Ref 21), A.G. Gaydon, Shock-Tube Studies of Processes of Electronic Excitation in Gases reported that the spectrum-line reversal temperature in shock-heated gases can be used to obtain information about efficiencies and processes of electronic excitation of metal atoms at high temperatures. For excitation by molecules, the electronic excitation temperature tends to follow the effective vibrational temperature of the molecules, and reversal temperatures may be low near the shock front if. the vibrational relaxation time is appreciable. Although excitation of metal atoms by cold inert gases has a very small effective cross-section, it is shown that at 2500°K the cross-sections of excitation of Cr or Na by Ar or Ne are around 1/20 of the gas-kinetic cross-sections... 

Reversal-temperature measurements of the Na and Cr lines in simple molecular gases, shock-heated to 2000-3000°K and to 0,2-2 atmospheres agree excellently with temperatures calculated from the measured shock velocity. Thus in these cases, collision processes are rapid enough to maintain effective equilibrium between ground and excited state populations despite radiatio n losses. In some shock tube work, however, the reversal temperature is initially above the equilibrium value, probably owing to delay in dissociation of the molecules, so that the temperature in translation and in internal degrees of freedom of the molecules is initially too high... 

The high flame front velocities prior to attainment of the steady state probably result from the transient conditions between the combustion front and shock front. Sufficient data were lacking to show whether the shock-heated gas ignited spontaneously, immediately behind the shock front, or whether the flame front overtook the shock front. In any event, the combustion wave finally moves along with the shock wave, thus forming a detonation wave... 

Here the TNT sample is compressed at very low pressures from V=1 cc/g to V X).62 cc/g (crystal density). Further compression (increase in pressure) then causes the sample to expand This can only mean that some heat effect is overcoming this compression. Since it can be shown that uniform shock heating at pressures of the order of a few kbars is very small, this heat effect must be produced by exothermic chemical reaction at or very near the shock front. Thus shock Hugoniots for reactive materials can provide information on the presence or absence of chemical reaction at the shock front... 

The main ideas of Campbell et al (Ref 1 la) are best summarized by reference to the figure above (Fig 8 of Ref 11a). The entering shock heats and compresses the LE. After an induction time or delay of t, thermal explosion and detonation occur at the shock entry face where the LE has been hot longest. This de-... 

G. Molecular Halogen Emission in Shock-Heated Gases... 

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