Deflagration of hydrazine perchlorate

The deflagration of hydrazine perchlorate, both pure and with fuel and catalyst additives, has been investigated. Hydrazine perchlorate will deflagrate reproducibly if a few percent fuel is present. The deflagration process is catalyzed by copper chromite, potassium dichromate, and magnesium oxide. Deflagration rates have been measured photographically from 0.26 to 7.7 atm. A liquid layer was observed at the surface in these experiments. Vaporization rate measurements from 180°-235° C. have yielded the expression... 

The thermal decomposition of hydrazine perchlorate has been investigated, and ammonium perchlorate was found to be a major product (13). We know of no studies of the self-deflagration of hydrazine perchlorate. The results reported here are concerned with studies of pure hydrazine perchlorate and hydrazine perchlorate containing small amounts of additives. 

Deflagration of Hydrazine Perchlorate-Additive Mixtures. Fuel Additives. In the case of ammonium perchlorate, it has been found (2) that at pressures below that at which pure ammonium perchlorate will sustain deflagration, ammonium perchlorate-fuel mixtures containing of the order of 5% fuel do deflagrate smoothly. Paraformaldehyde was the most effective fuel additive in promoting deflagration, and for that reason experiments were performed with mixtures of hydrazine perchlorate and various formaldehyde polymers. 

Other fuel-type additives were effective in promoting the deflagration of hydrazine perchlorate. Experiments have been performed with thiourea and naphthalene. The results of the deflagration experiments for preheated pure hydrazine perchlorate and for the hydrazine per-chlorate-fuel mixtures are summarized in Table III and Figure 2. The strands used were all pressed to about 95% of the crystal density—i.e., to a density of about 1.85 grams/cc. 

Effects of Catalysts. It has been found that copper chromite, potassium dichromate, and magnesium oxide promote the deflagration of hydrazine perchlorate. Since none of these additives has any fuel content, they must be considered to be catalysts. The results of experiments with these additives are shown in Table IV. Experiments were performed both with pressed (p 1.9 grams/cc.) and tamped (p 1.1. grams/cc.) strands. 

Figure 2. Rate of deflagration of hydrazine perchlorate with a small amount of fuel...

Mechanism of Deflagration of Hydrazine Perchlorate. One approach to the mechanism of hydrazine perchlorate deflagration is to consider whether it fits the classification of a vaporization-type process like ammonium perchlorate where the material vaporizes without decomposition, and exothermic gas phase reactions occur with resultant heat transfer to the condensed phase. The alternative to a process of this type is one wherein heat production occurs in the molten zone as a result of condensed phase reactions. 

Tlie deflagration of Hydrazine Perchlorate was studied by l.evy, von Elbe and co-wotkers [111]. They found that it could be catalysed by copper chromite, potassium dicluomatc and magnesium oxide. The entropy of vapourization and dissocial ion ... 

The mixtures of hydrazine perchlorate and the fuels or catalysts were prepared by mixing the hydrazine perchlorate shot with the finely ground other ingredients in an ordinary vee mixer for several hours. The uniform deflagration rates observed with the various mixtures attest to the homogeneity of strands prepared in this way. 

Figure 3. Tracing of thermocouple record of hydrazine perchlorate deflagration wave. Strand composition 94.5% hydrazine perchlorate, 5% Delrin, 0.5% magnesium oxide density 1.85 grams/cc. pressure 0.5 atm. deflagration rate 0.09 cm./sec.

Flame Temperature Measurements. Thermodynamic calculations of the nature of the products of hydrazine perchlorate self-deflagration at a series of processes were performed by an IBM-7090 computer program. The results are shown in Table V. The calculations were made assuming... 

Since it has been found that the self-deflagration of ammonium perchlorate does not lead to the products calculated on the basis of thermodynamic equilibrium, we felt it desirable to measure the flame temperature for hydrazine perchlorate. A flame temperature appreciably different from that calculated would indicate a nonequilibrium distribution of products which would require investigation. 

Preliminary experiments were performed in which lengths of 1-mil platinum wire were stretched through the center of tamped strands of hydrazine perchlorate. Examination of the wire after deflagration showed that the passage of the flame had melted it. The melting point of platinum is 2042° K. and the heat loss by radiation was estimated at about 40° K. This placed the flame temperature as somewhere above 2082° K. 

The experiments performed in this program are grouped into (a) experiments in which vaporization rates of pure hydrazine perchlorate were measured (b) deflagration rate measurements (c) temperature profile measurements (d) flame temperature measurements. 

A General Description of the Hydrazine Perchlorate Deflagration Process. Let us first describe the deflagration process for hydrazine perchlorate from the above results. It is a process characterized by the formation of a molten zone which is quite turbulent and foamy it is a very erratic process, particularly for the pure material, and it is subject to very potent catalysis by copper chromite and potassium dichromate and to moderate catalysis by magnesium oxide. The process is comparatively reproducible in the presence of small amounts of fuel, and the rate obtained apparently does not depend on the nature of the fuel but only on the ambient pressure. It can be expressed by r — 0.22P where f is in cm./sec. and P in atmospheres. This corresponds to a rate, at 1 atm., some 15 times greater than that calculated by extrapolation for ammonium perchlorate (16). However the process is unstable at pressures above about 7 atm. and steady deflagration cannot be attained above this pressure. 

The main features of our results which are inconsistent with the above picture are the very erratic nature of the deflagration of pure hydrazine perchlorate and the turbulent behavior of the molten zone. It is difficult to see how, for example, small amounts of impurities could affect the vaporization process from the turbulent molten layer. In other words, if the deflagration depends on vaporization it appears that it should be more reproducible. Contrariwise, if condensed phase reactions are important, then the presence of small amounts of impurities which could catalyze these reactions could easily be important in deciding whether deflagration occurred or not. The turbulent, foaming appearance of the molten zone also suggests that gas evolution—i.e., reaction, is occurring within the body of the molten liquid. 

We feel that the erratic deflagration behavior of pure hydrazine perchlorate is attributable to the presence or absence of small amounts of impurities that catalyzed the condensed phase process, which implies that when the condensed phase process did not occur, deflagration would not propagate. The function of the fuels then would be to allow exothermic oxidation-reduction reactions to occur in the condensed phase... 

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