Showing papers on "Ammonium perchlorate published in 1968"

The burning mechanism of ammonium perchlorate-based composite solid propellants

Abstract: : Theories of propellant burning are briefly reviewed in the light of previous studies of the burning behavior and flame structure of composite ammonium perchlorate (AP) propellant. Those studies showed that the granular diffusion flame (GDF) theory conforms to the known structure of the propellant flame, and is quantitatively valid for a wide class of practical AP propellants, much more so than any other theory proposed for composite propellants.

Role of Point Defects in the Thermal Decomposition of Ammonium Perchlorate

Abstract: The thermal decomposition of ammonium perchlorate has usually been described in terms of chemical reactions with the point defect structure of the solid ignored. Both the isothermal and adiabatic decompositions have been reinvestigated over the temperature range 200 to 450°C. There is a good correlation between the isothermal d. c. electrical conductance of single crystals, and of conductance as a function of temperature with the extent of decomposition, indicating that charge carriers play a significant role in the thermal decomposition. The study of the electrical conductivity as a function of temperature has resulted in the assignment of a probable defect structure to ammonium perchlorate: cationic Frenkel type below 250°C and Schottky disorder at higher temperatures. This suggests an explanation for the phenomenon of only 30% decomposition below 250°C and 100% above this temperature.

Contribution of solid-phase heat release to AP composite-propellant burning rate.

Abstract: Experimental and analytical approaches were applied to deduce the solid-phase surface temperature of ammonium perchlorate (AP) and to evaluate the effect of AP solid-phase decomposition rate on burning rate. Several batches of AP, of various particle sizes, were modified by irradiation with 9.8 X 10 rad of Co and by thermal shock in liquid N2. Under slow heating rates, both types of modified AP decompose several times faster than conventional AP. However, propellants containing the modified AP burned at the same rate as propellants containing conventional AP. A mathematical model was developed to re-examine Beckstead and Hightower's observations of the crystallographic phase transition from orthorhombic to cubic structure in burning AP. By considering the effects of both conductive heat transfer and subsurface heat release, along with transients after AP extinguishment, a calculated solidphase surface temperature of approximately 442°C was obtained. No change in surface temperature was calculated when upper limit values of subsurface heat-generation rates were considered. Since subsurface heat generation did not affect calculated surface temperature and since AP modified to have higher decomposition rates did not affect propellant burning rate, it is concluded that AP subsurface reactions are not a factor in controlling propellant burning rate at pressures above 500 psi.

Effects of X‐ and Γ‐Ray Radiation on the Thermal Decomposition of Solid Orthorhombic Ammonium Perchlorate. II. Kinetics and Discussion

Abstract: The experimental data obtained by thermally decomposing unirradiated and irradiated orthorhombic ammonium perchlorate in the temperature range 193°–238°C has been carefully analyzed. Most of this data consists of pressure vs time curves of the total evolved gas or that not trapped at −95°C or lower, obtained with powders and millimeter‐size crystals. All of these curves can be described by the Avrami–Erofeyev equation. The increase in the acceleratory period rate, which is induced by, and is proportional to, x‐ or γ‐ray irradiation prior to decomposition, can be attributed to the introduction of additional decomposition sites, an increase in the rate that each nucleus grows, or a combination of these. Independent microscopic examination of partially decomposed crystals also indicates that irradiation has increased the concentration of decomposition nuclei. In addition, the p vs t curve analysis shows that irradiation has increased the rate that potential decomposition sites are converted to active sites. ...

Combustion characteristics of crystalline oxidizers.

Abstract: : Various modifications to the monopropellant solid oxidizer ammonium perchlorate are described. Cation replacement, or 'doping' of AP by Sr(++) ion and deuteration to provide ND4ClO4 did not alter the burning rate from that of pure NH4ClO4 at 14.7 psia. Hydrated aluminum sulfate shows an ability to extinguish AP combustion at the 5% level, whereas 2% does not even alter the burning rate at atmospheric pressure. The theoretical adiabatic combustion species for AP and dihydroxy glyoxime (DHG) at 1, 34 and 68 atmospheres are given. DHG produces fuel rich rather than oxygen rich monopropellant combustion species.

Process for producing cross-linked propellants

Abstract: Chemically modified double base propellant formulations containing a phenol-blocked diisocyanate as cross-liking agent are cross-linked by unblocking the diisocyanate during propellant cure. A typical formulation contains nitrocellulose, nitroglycerin, ammonium perchlorate or cyclotrimethylene trinitramine, aluminum and a prepolymer of polyglycoladipate and 2,4-tolylene diisocyanate.

Ignition and Combustion of Solid Rocket Propellants

Abstract: Publisher Summary The application of solid propellants to rocket motor applications represents one specific example of using a change in the chemical state of matter taking place under controlled conditions for practical gain. Other examples include the combustion of coal and wood for a wide variety of applications, the ablation of material for heat shields, the use of packed catalytic reactors and of fluidized-bed reactors, and the explosive combustion of dust particles. One unique characteristic of solid rocket propellants that distinguishes them from all other solid fuels is the incorporation of sufficient reducing and oxidizing components within the solid phase to effect the transformation to gaseous products. Composite propellants are made by embedding a finely divided solid oxidizing agent in a plastic, resinous, or elastomeric matrix. The matrix material usually provides the fuel for the combustion reaction, although solid reducing agents are sometimes included. A third type of propellant, the composite modified-double-base propellant, represents a combination of the other two types. These propellants are made from mixtures of nitroglycerine and nitrocellulose or similar materials, but with crystalline oxidizers, such as ammonium perchlorate also included in the matrix. Development of a theoretical analysis of the combustion mechanism of double-base propellants gave birth to the model of the combustion zone. Because of the decomposition of the solid ingredients, the initial exothermic decomposition reactions could be analyzed as a single reaction occurring at the propellant surface. The initial products of decomposition vaporize and undergo partial oxidation reactions. This gives rise to a boiling porous reaction zone, commonly called the “fizz reaction” zone, which can be visually observed on the propellant surface.

Mixing process and extrusion of solid propellants

Abstract: An improved extrudable, high energy solid propellant composition consisting essentially of the copolymer of vinylidene fluoride and perfluoropropylene (Viton), an inorganic oxidizer such as ammonium perchlorate, potassium perchlorate or ammonium nitrate, and a metal powder such as aluminum, beryllium, magnesium or zirconium. This composition is extrudable into any suitable shape and has a very high percentage theoretical maximum density so as to be practical for utilization in rocket motors for propulsion.

Decomposition and deflagration of ammonium perchlorate

Abstract: : The report contains studies of the behavior of pure single crystals of ammonium perchlorate: decomposition in vacuum, high heating rate decomposition at atmospheric pressure, self-deflagration in nitrogen atmospheres and deflagration in methane atmospheres.

The thermal decomposition of ammonium perchlorate: a literature review

Abstract: : The review includes the following topics: Stoichiometry of thermal decomposition; Stoichiometry of deflagration; Crystal structure and transformation; Sublimation; Low temperature reaction mechanisms (electron transfer, proton transfer, activation energy); High temperature reaction mechanisms; Effect of impurities, particle size, and lattice defects.

Solid Propellant Rockets

Abstract: Solid propellants are of two basic types: composites and double base propellants. The latter consist of a backbone of nitrocellulose (guncotton) onto which a quantity of nitroglycerine has been absorbed, resulting in a leathery propellant which can be cast or extruded into desired shapes.

Thermal Analysis of Ammonium Perchlorate and of its Mixtures with Inorganic Substances

Abstract: Solid mixtures containing ammonium perchlorate diluted with reputedly inert substances SiC, SiO2, TiO2, Al2O3 and the salts: KCl, NaCl, BaCO3, CaCO3 respectively were studied by TGA and DTA. Undiluted NH4ClO4 and the perchlorates of K, Na, Ba, Ca were also examined. The two known temperature regions of NH4 ClO4 thermolysis were confirmed. The first DTA exotherm of NH4ClO4 seems to be related to its limited decomposition; it can be suppressed by an ammonia atmosphere, by thermal cycles, or by heat-dissipating conditions. The second exotherm is related to the change of the decomposition mechanism of HClO4 above 330°. TGA rate curves of stoichiometric mixtures of NHClO4 with salts show two peaks due to decomposition of NH4ClO4 and one peak due to the MeClO4 formed on heating. The formation of MeClO4 is confirmed by visual observations and by DTA. Thermal cycles followed by DTA of stoichiometric mixtures of (NH4ClO4 + KCl), (NH4ClO4 + BaCO3) reveal the systematic formation of MeClO4 at the expense of NH4ClO4. For (NH4ClO4 + NaCl), (NH4ClO4 + CaCO3) there appear in the vicinity of the transition endotherm of NH4ClO4 new reversible endotherms difcontaining NH4ClO4. Only after their thermal decomposition do the transition endotherms of MeClO4 appear.

Solid propellants containing burning rate depressants

Abstract: This patent described novel solid ammonium perchlorate containing propellant compositions containing powerful burningrate depressants which are potential bases, that is, compounds which are capable of releasing free bases. The burning-rate depressants of this invention do not reduce the specific impulse of the propellant, nor do they interfere with cure reactions or adversely affect the physical properties of the cured propellant.

A Study on the Mechanism of the Thermal Decomposition of Ammonium Perchlorate

Abstract: The thermal decomposition of ammonium perchlorate in the presence of potassium chloride and chromium (III) oxide was investigated using K36 Cl and51 Cr2 O3 to elucidate the reaction mechanism. Two simultaneous routes are suggested for the decomposition. It was found that double decomposition in vacuo between potassium chloride and ammonium perchlorate does not result in the formation of potassium perchlorate. Chromium (III) oxide was not oxidized by ammonium perchlorate, but oxidation to the hexavalent state took place when potassium chloride was present.

Effect of catalytic additives on the burning of ammonium perchlorate and certain of its mixtures

Abstract: Potassium bichromate is the most effective catalyst of the burning of ammonium perchlorate and its mixtures with coke. Chromic oxide is less effective as a catalyst and accelerates the burning of the perchlorate only in the pressure range up to 500 atm. The effect of chromic oxide on the burning of a mixture of perchlorate and coke is positive over the enture range of pressures studied.

Study of the Thermal Behavior of Solid Propellants by Differential Scanning Calorimetry

Abstract: The complex combustion of composite (heterogeneous) solid propellants has not as yet been described in a practical combustion model. The main interest in establishing such a model is the need for a priori knowledge of the effect of changes in physical properties and chemical composition of solid propellants on the ballistic parameters of a rocket motor. If one contends that solid phase reactions are important and possibly even controlling in this complex combustion process, a study of the thermal behavior of solid propellants and their individual ingredients is essential to understanding their combustion process.

Deflagration and deflagration limits of single crystals of ammonium perchlorate

Abstract: : Using a new technique, the deflagration pressure limit was measured by imposing a known linear temperature gradient along the length of the ammonium perchlorate sample and igniting the warmer end. The pressure was adjusted so that the flame would not propagate through the entire solid, and the length remaining unburned determined the limiting solid temperature corresponding to the set pressure. The AP single crystal deflagration rates were measured using high-speed motion photography and were essentially the same in helium and nitrogen ambient atmospheres. In direct contrast to the catalytic effect of KMnO4 on AP thermal decomposition, a preliminary study showed that 0.4-2.0 mole % KMnO4 isomorphously substituted into the AP crystal lattice prevented deflagration from occurring.

Correlations between Deflagration Characteristics and Surface Properties of Nitramine-Bas ed Propellants

Abstract: The deflagration of RDX propellant has been investigated at pressures up to 5000 psi with various particle sizes of RDX and under the influence of burning-rate modifiers. The transi- tion point for change in slope of the burning-rate curve is shifted to lower pressure by burn- ing-rate retarders or by decreasing the particle size of the explosive. This effect is related to changes in the burning surface of the propellant. An increase in RDX particle size and/or burning-rate catalysts enhances the formation of surface depressions during burning. Burn- ing-rate accelerators lower the decomposition temperature and the activation energy of the thermal decomposition of the propellant, whereas a burning retarder raises the decomposition temperature. It is concluded that for the burning rate of nitramine propellants the physical conditions at the burning surface and its decomposition characteristics are of importance. LTHOUGH various models have been developed to describe the combustion mechanism of solid composite propellants, there is still a controversy as to whether the burning rate of composite propellants is controlled by a gas- phase reaction1?2 or by a solid-phase decomposition reac- tion.3"5 For double-base propellants, it is believed that the surface decomposition reactions control the rate of burning and that the decomposition of the surface is caused by the heat fed back from the hot flame.6 Composite propellants based on organic explosives, such as RDX (cyclotrimethylene trinitramine) and HMX (cyclo- tetramethylene tetranitramine) with an oxygen balance of 66.7% and PETN (pentaerythritol tetranitrate) are inter- mediates between conventional composite propellants and double-base propellants. In the composite propellant based on an organic explosive, the binder cannot be considered a fuel as it is in propellants with an inorganic oxidizing agent. The difference between the two propellant systems is demonstrated by a comparison of the adiabatic flame tem- peratures of RDX (3292°K) and polyester-RDX propellant (1571°K) with AP (ammonium perchlorate) (1405°K) and polyester-AP propellant (2311°K). In the RDX propellant, the binder acts as a coolant, reducing the burning rate of the explosive, whereas in the AP propellant, the binder burns with the oxidizer, resulting in high flame temperature and high burning rate. In contrast to the gas-phase model de- veloped for AP propellants, 1 it is assumed here that, for the RDX propellant, the condensed-phase exothermic decom- position reaction of RDX provides a self-sustainin g heat source and is important for burning-rate control. A characteristic feature of the explosive powders, RDX, HMX, and PETN is a transition from slow, steady burning to rapid, unsteady burning at a pressure that varies with the explosive and with the explosive's pore size.7*8 A convec- tive mechanism has been reported as a possible explanation for the rapid burning of RDX, HMX, and PETN above the transition pressure. According to this theory proposed by Taylor, the transition point is based on the ratio between the thickness of the molten layer and the pore diameter of the

Heterogeneous decomposition of ammonium perchlorate-catalyst mixtures using pulsed laser mass spectrometry.

Abstract: Pulsed ruby laser mass spectrometry technique for flash pyrolysis of ammonium perchlorate-catalyst mixtures

Inhibitors of combustion and ammonium nitrate and ammonium perchlorate and their mixtures

Abstract: : The inhibiting effect of ammonium salts, such as ammonium carbonate, oxalate, citrate, tartrate or fluoride, and a reducing agent, such as diphenylamine on the burning rate of ammonium nitrate or ammonium perchlorate was investigated. It was thought that the effect of easily dissociating ammonium salts would consist of shifting the equilibrium of the reaction to the left, while the effect of diphenylamine would be either a reduction or a binding of the acid formed in the dissociation, thus inhibiting the further oxidation of ammonia. This assumption was verified experimentally by the combustion of ammatol 80/20 (taken instead of pure ammonium nitrate which does not burn in the bomb) or ammonium perchlorate with or without the additives mentioned above, taken in the amount of 5%; the combustion took place at varying pressures up to 1000 atm in a constant pressure bomb.