Showing papers on "Ammonium perchlorate published in 1998"

Perchlorate reduction by a mixed culture in an up-flow anaerobic fixed bed reactor

Abstract: HAP-1 is a Gram-negative microaerophile which reduces perchlorate to chloride by the proposed pathway ClO4 to ClO3 to ClO2 to Cl + O2. A cost-effective perchlorate treatment process has been established using a consortium of facultative anaerobic organisms and W. succinogenes HAP-1. The mixed anaerobic bacterial culture containing W. succinogenes HAP-1 was examined for the ability to form a biofilm capable of perchlorate reduction. An up-flow anaerobic fixed bed reactor (UAFBR) was packed with diatomaceous earth pellets and operated at residence times of 1.17 and 0.46 h to insure a viable biofilm had attached to the diatomaceous earth pellets. Reduction rates of perchlorate to chloride in the UAFBR could be maintained at 1 g of perchlorate reduced h−1 L−1. Studies with the same bacterial consortium in continuously stirred tank reactors (CSTR) generally reduced 0.5–0.7 g of perchlorate h−1. Viable cell counts were performed periodically on the diatomaceous earth pellets and demonstrated that the W. succinogenes HAP-1 population was maintained at 28–47% of the total microbial population. Scanning electron micrographs demonstrated that the external and internal surfaces of the diatomaceous pellets were densely colonized with microbial cells of multiple cell types. This is the first report of an anaerobic mixed culture forming a biofilm capable of perchlorate reduction.

Energetics of ammonium perchlorate decomposition steps

Abstract: Energy minima and enthalpies at 298 and 800 K were computed for 37 atoms, molecules and ions that have been implicated as intermediates in the thermal decomposition of ammonium perchlorate. These data permit the calculation of ΔH(298 K) and ΔH(800 K) for hundreds of reactions that may be involved; 39 of these are listed, and several possible decomposition pathways are outlined. The computations were carried out at the density functional B3PW91/6-3ll+G(2df) level, which we found to be effective for systems containing several oxygen and/or chlorine atoms in close proximity. ΔH(298 K) and ΔH(800 K) are found to differ by less than 1.0 kcal mol−1. We have identifiied an intermediate complex in the sublimation of ammonium perchlorate (believed to be the first decomposition step) which accounts for the activation energy of sublimation being considerably less than its overall enthalpy change.

Mechanical and burning properties of highly loaded composite propellants

Abstract: An improvement in the performance of solid rocket motors was achieved by increasing the oxidizer content of HTPB-based solid propellants. To minimize the adverse changes in the mechanical and rheological properties due to the increased amount of hard solid particles in the soft polymeric binder matrix, the optimum combi- nation of the particle sizes and volume fractions of the bimodal ammonium perchlorate and the aluminum powder in the solid load was obtained from the results of testing a series of propellant samples prepared by using ammonium perchlorate in four different average particle sizes, 9.22, 31.4, 171, and 323 mm. The maximum packing density of solids in the binder matrix was determined by changing the sizes and the volume fractions of fine and coarse ammonium perchlorate at constant solid loading. The aver- age size (10.4 mm) and concentration of aluminum powder used as metallic fuel were maintained constant for ballistic requirements. Optimum sizes and fine-to-coarse ratio of ammonium perchlorate particles were determined to be at mean diameters of 31.4 and 323 mm and fine-to-coarse ratio of 35/65. Solid content of the propellant was then increased from 75 to 85.6% by volume by using the predetermined optimum sizes and fine to coarse ratio of ammonium perchlorate. Mechanical properties of the propellant samples were measured by using an Instron tester with a crosshead speed of 50 mm/ min at 257C. The effect of oxidizer content and fine-to-coarse ratio of oxidizer on the burning rate of the propellant was also investigated by using a strand burner at various pressures. From experiments in which the size and the fine-to-coarse ratio of ammo- nium perchlorate were changed at constant solid loading, a minimum value of initial modulus was obtained for each fine-to-coarse ratio, indicating that the solids packing fraction is maximum at this ratio. The tensile strength and the burning rate increase, while the elongation at maximum stress decreases with increasing fine-to-coarse ratio of ammonium perchlorate. Experiments in which the total solid loading was increased at constant fine-to-coarse ratio of ammonium perchlorate show that the modulus, the tensile strength and the burning rate increase, while the elongation at maximum stress decreases with increasing solid loading. Propellants having solid loading of up to 82% exhibit acceptable mechanical properties and improved burning properties suitable for rocket applications. q 1998 John Wiley & Sons, Inc. J Appl Polym Sci 67: 1457-1464, 1998

The Details of Combustion of Ammonium Perchlorate Propellants: Leading Edge Flame Detachment

Abstract: The transition from particle flamelet burning to premixed flame burning of ammonium perchlorate (AP)/hydrocarbon (HC) binder propellants is identified with detachment of the oxidizer/fuel (O/F) flamelet from the stoichiometric tip of the diffusion field over the AP particle. The conditions (pressure, particle area, local stoichiometry) for detachment are revealed by singular regions of the burning rate versus pressure curves for selected bimodal propellants.

Particle-free, gas-producing mixture

Abstract: The invention relates to a particle-free, gas-producing mixture for use in a gas generator for a safety device, in particular for a vehicle-occupant restraint system, with a total water content of the gas-producing mixture of at most 0.3%, consisting of: a) an energy-rich fuel with an oxygen value of not less than -35%; b) an oxidant mixture of ammonium nitrate and ammonium perchlorate, wherein the ammonium nitrate is contained in a proportion of 35 to 50 wt. %, and the ammonium perchlorate in a proportion of 3 to 10 wt. %, in each case relative to the total weight of the mixture; c) optionally, relative to the total weight of the mixture, a phase-stabilizing additive for the ammonium nitrate in a proportion of at most 5 wt. % relative to the weight of the ammonium nitrate; d) 0 to 3 wt. % combustion moderators relative to the total weight of the mixture, and e) 0 to 5 wt. % processing aids relative to the total weight of the mixture.

Low temperature autoignition composition

Abstract: The present invention relates to a low temperature autoignition composition for safely initiating combustion of a main pyrotechnic charge in a gas generator or pyrotechnic device exposed to flame or a high temperature environment. The low temperature autoignition compositions of the invention include a mixture of an oxidizer and a powdered metal, wherein the oxidizer includes silver nitrate or a comelt or mixture comprising silver nitrate and at least one of an alkali metal nitrate, an alkaline earth metal nitrate, a complex salt nitrate, a dried, hydrated nitrate, an alkali metal chlorate, an alkali metal perchlorate, an alkaline earth metal chlorate, an alkaline earth metal perchlorate, ammonium perchlorate, sodium nitrite, potassium nitrite, silver nitrite, a complex salt nitrite, a solid organic nitrate, a solid organic nitrite, or a solid organic amine, and where the metal fuel and oxidizer are present in amounts sufficient to provide an autoignition composition having an autoignition temperature of no more than about 232° C. The present invention also relates to a method for initiating a gas generator or pyrotechnic composition in a gas generator or pyrotechnic device exposed to flame or a high temperature environment. In the method of the invention, the gas generator or pyrotechnic composition is placed in thermal contact with a low temperature autoignition composition of the invention.

Modeling and rheology of HTPB based composite solid propellants

Abstract: The propellant with the minimum viscosity required for a defect-free casting can be obtained by proper selection of the size and fractions of solid components leading to maximum packing density. Furnas' model was used to predict the particulate composition for the maximum packing density. Components with certain size dispersions were combined to yield a size distribution that is closest to the optimum one given by Furnas for maximum packing. The closeness of the calculated size distribution to the optimum one was tested by using the least square technique. The results obtained were experimentally confirmed by viscosity measurement of uncured propellants having HTPB binder and trimodal solid part accordingly prepared by using aluminum (volumetric mean particle diameter of 10.4 μm) and ammonium perchlorate with four different sizes (volumetric mean particle diameters: 9.22, 31.4, 171, and 323 μm), The experimental measurements showed that the compositions for the minimum viscosity are in good agreement with those predicted by using the model for maximum packing. The propellant consisting of particles with mean diameters of 10.4, 31.4, and 323 μm was found to yield the minimum viscosity. This minimum viscosity was observed when the fraction of the sizes with respect to total solids was 0.141, 0.300, and 0.559, respectively.

Ammonium perchlorate composition with chlorine scavenger

Abstract: This invention relates to gas-generative compositions consisting essentially of ammonium perchlorate with a chlorine scavenger, such as strontium nitrate, barium nitrate, potassium nitrate, or lithium carbonate, the combination being present in an amount of about 30 to about 95 % by weight, up to about 5 % by weight of a binder, up to about 5 % by weight of a burning rate catalyst, together with an organic fuel, such as guanidine nitrate. The fuel is in an amount complementary to the combined weight of ammonium perchlorate, burning rate catalyst, chlorine scavenger, and binder, at an oxidation ratio of 0.90 to 0.98. The invention also includes the method of inflating an inflatable device by generating gas employing the noted composition and a gas generator in which the gas-generative composition is that of the present invention.

Thermal Decomposition Behavior of Ammonium Perchlorate and of an Ammonium-Perchlorate-Based Composite Propellant

Abstract: The thermal decomposition of ammonium perchlorate (AP) and ammonium-perchlorate-based composite propellants is studied using the simultaneous thermogravimetric modulated beam mass spectrometry (STMBMS) technique. The main objective of the present work is to evaluate whether the STMBMS can provide new data on these materials that will have sufficient detail on the reaction mechanisms and associated reaction kinetics to permit creation of a detailed model of the thermal decomposition process. Such a model is a necessary ingredient to engineering models of ignition and slow-cookoff for these AP-based composite propellants. Results show that the decomposition of pure AP is controlled by two processes. One occurs at lower temperatures (240 to 270 C), produces mainly H2O, O2, Cl2, N2O and HCl, and is shown to occur in the solid phase within the AP particles. 200(micro) diameter AP particles undergo 25% decomposition in the solid phase, whereas 20(micro) diameter AP particles undergo only 13% decomposition. The second process is dissociative sublimation of AP to NH3 + HClO4 followed by the decomposition of, and reaction between, these two products in the gas phase. The dissociative sublimation process occurs over the entire temperature range of AP decomposition, but only becomes dominant at temperatures above those for the solid-phase decomposition. AP-based composite propellants are used extensively in both small tactical rocket motors and large strategic rocket systems.

Use of a mixture of non-hygroscopic organic fuel and inorganic nitrate, chlorate or perchlorate oxidizing agent as the igniter for gas generators in safety devices, especially vehicle air-bag systems

Abstract: A gas-generating mixture of: (a) fuel consisting of non-hygroscopic organic compound(s) with a m.pt. of at least 150 deg C; and (b) oxidizing agent(s) selected from alkali or alkaline earth metal nitrates, chlorates and perchlorates, ammonium nitrate or ammonium perchlorate is used as the igniter in a gas generator for a safety system.

Metal Agglomeration in Solid Propellants Combustion

Abstract: This article is a continuation of the work (Rashkovsky, 1998).The solution method of equation of metal agglomeration in solid propellants combustion theory is suggested. Itis based on statistical tests method (Monte Carlo method). Different agglomeration mechanisms have been investigated and agglomerates probability density function for different ammonium perchlorate (AP) particles spectra have been obtained, as well as dependencies ofaverage mass agglomerates diameter upon average mass diameter of AP particles. It is shown, that mass agglomerates distribution is of polymodal nature, which corresponds to knownexperimental data. Effect of different factors on agglomerates dispersity has been investigated. This paper includes analysis of different calculated schemes. Besides, the peculiarities of Monte Carlo method applying and common recommendations, necessary for making new calculation models of the metal agglomeration process in composite solid propellants combustion are considered. The effect o...

Pyrotechnic mixtures generating non-toxic gases based on ammonium perchlorate

Abstract: The invention concerns pyrotechnic mixtures generating non-toxic gases characterised in that they essentially consist of a cross-linkable reducing binder based on epoxy resin or silicone resin, an oxidising filler based on ammonium perchlorate and a chlorine scavenger such as sodium nitrate and energetic additives consisting of a cupric compound such as cupric oxide or basic copper nitrate and of a nitrogenated organic compound such as, for example, nitroguanidin or guanidine nitrate. The filler can also contain potassium perchlorate. Said compositions burn at moderate temperatures generating gases rich in nitrogen and poor in nitrogen oxides and carbon monoxide. They are most suitable as pyrotechnic load for gas generators designed to inflate protective air bags for motor vehicle passengers.

Morphology of Polymer-Salt Complex Films Crossover from Fractal to Compact Aggregation

Abstract: In this paper we present a study of the variation of morphology of polyethylene oxide (PEO) films complexed with ammonium perchlorate (NH4ClO4) formed by evaporating a methanolic solution. Films with salt concentration x = 0 - 0.35 (x is the weight fraction of salt) were prepared for the morphology study. The wide varitey of structures obtained were systematically studied by photographs and polarizing microscopy. Some preliminary studies of x-ray diffraction, differential scanning calorimetry and variable temperature polarizing microscopy have also been done to identify the various phases present in the films.

Effect of Burning Rate Modifiers on Subatmospheric Flame Temperatures of AP/HTPB Composite Solid Propellants

Abstract: Using 30 um. pt and Pt 13 percent Rh thermocouples, flame temperatures of uncatalysed andcatalysed ammonium perchlorate/hydroxyl-terminated polybutadiene (AP/lffPB) composite solidpropellants were measured under subatmospheric conditions. Ferric oxide F e 2 and copper chromite(CC) were the catalysts used. The study demonstrates that Fe2O3 catalysed propellant, notwithstandingits least combustion efficiency undt;r subatmospheric conditions and weak gas-phase flame, has themaximum burning rate enhancement. This is argued to be due to the increased surface and subsurfacereactions caused by Fe2O3. CC-catalysed propellant burns to the least subatmospheric pressure withminimum loss in combustion efficiency indicating that this class of propellant may be more suitablefor base-bleed applications.

Fast neutron activation analysis of high energy materials and polymers

Abstract: Fast neutron activation analysis (FNAA) technique using 14 MeV neutrons has been applied to estimate nitrogen, chlorine, oxygen and aluminium in explosives and propellants. FNAA also has been employed to determine nitrogen, oxygen, chlorine and fluorine in various polymers. The technique is fast, accurate, nondestructive and non-hazardous in analysing elements in explosives and propellants compared to a number of chemical methods which are time consuming, less accurate, suitable for single elemental analysis and do not measure oxygen directly. In this paper FNAA technique, its theory and application for estimation of elements in high energy materials carried out in the laboratories of the authors have been reviewed. The method also helped to determine the differential distribution of aluminium and ammonium perchlorate in aluminized explosives and rocket propellants. Modification of polyepichlorohydrin to polyglycidylazide was followed by FNAA more accurately than IR spectral analysis.

Analysis of Trace Level Perchlorate in Drinking Water and Ground Water by Electrospray Mass Spectrometry

Abstract: The recent discovery of perchlorate contamination in the ground water of several western states has resulted in widespread concern over the quality of drinking water supplies. Ammonium perchlorate has been found in commercial fertilizers and is used as the oxidizer and main ingredient in solid rocket propellants, fireworks, and munitions. The current acceptable level for the presence of perchlorate in drinking water is 18 parts per billion (ppb). However, it has been found at concentrations as high as 0.37% in ground water near munitions manufacturing and testing facilities.1–11 Perchlorate contamination has also been found in areas such as Texas, where fertilizers are used to maintain land for cattle farming. Two of the main ingredients in these commercial fertilizers, potash and Chilean nitrate, have been shown by Air Force Research Laboratory to contain up to 0.57% by weight perchlorate. Although these deposits contain the necessary ingredients for fertilizers, they are also a very rich source of perchlorate.9–11

Pyrotechnic compositions generating non-toxic gases based on ammonium perchlorate

Abstract: The invention concerns pyrotechnic mixtures generating non-toxic gases characterised in that they essentially consist of a cross-linkable reducing binder based on epoxy resin or silicone resin, an oxidising filler based on ammonium perchlorate and a chlorine scavenger such as sodium nitrate and energetic additives consisting of a cupric compound such as cupric oxide or basic copper nitrate and of a nitrogenated organic compound such as, for example, nitroguanidin or guanidine nitrate. The filler can also contain potassium perchlorate. Said compositions burn at moderate temperatures generating gases rich in nitrogen and poor in nitrogen oxides and carbon monoxide. They are most suitable as pyrotechnic load for gas generators designed to inflate protective air bags for motor vehicle passengers.

Effect of Catalyst Addition on Subatmospheric Burning Surface Temperature of Composite Propellants

Abstract: The subatmospheric burning with its higher catalytic effectiveness, lower temperature gradient, and slower combustion wave offers a Ž tting environment to study the effect of catalysts on the burning surface temperature of composite propellants. Using platinum and platinum-13% rhodium 7.5m thermocouples in uncatalyzed as well as copper–chromite-catalyzed ammonium perchlorate/hydroxyl-terminated polybutadiene composite propellants, the subatmospheric-burning surface temperatures were measured. The results of the present experimental study are in close agreement with the established trend; the surface temperature increases with the increase in pressure. Some experimental studies of others failed to give an observable change in surface temperature with pressure. This is argued to be because of the dimensional inadequacy of detectors in the very high-temperature-gradient environment. The measured surface temperature of the catalyzed propellant is signiŽ cantly higher than that of the uncatalyzed one. The study shows that the increased surface and subsurface heat release caused by catalyst addition causes this temperature enhancement.

Stability and Concentration Verification of Ammonium Perchlorate Dosing Solutions

Abstract: : Stability and concentration verification was performed for the ammonium perchlorate dosing solutions used in the on-going 90-Day Oral Toxicity Study conducted by Springborn Laboratories, Inc. (SLI Study No. 3433.1) and the Neurobehavioral Development study conducted by Argus Research Laboratories, Inc. (SS No. 7757A2l0-1096-25F). A sensitive and selective ion chromatography (IC) method for the analysis of perchlorate (ClO4)(-) and nitrate (NO3)(-), a possible interference anion, was developed to support these studies. The method development, and validation data more than sufficiently demonstrated that the IC method was capable of detecting both perchlorate and nitrate at 0.003 microgram/mL (5 ppb) in reagent water with excellent accuracy and precision. Ion chromatographic analysis of the stability solutions showed that under controlled room temperature, relative humidity and light intensity, ammonium perchlorate was stable in reagent water for at least 109 days. The concentrations of the ammonium perchlorate dosing solutions (0.05 to 200 micrograms/mL) were verified by IC analysis to be within an acceptable range of +/- 10%.

Perchlorate Literature Review and Summary: Developmental Effects, Metabolism, Receptor Kinetics and Pharmacological Uses.

Abstract: : Perchlorate is a monovalent anion found as a soil and groundwater contaminate on government contractor sites and, more recently, on an Air Force site. Perchlorate is dissociated from the salt, ammonium perchlorate, which is an efficient oxidizer used in solid rocket propellant systems. This review was undertaken to evaluate the available information on developmental and reproductive effects, thyroid iodide receptor kinetics, pharmacological uses of perchlorate outside the treatment of Graves' disease, and absorption, distribution, metabolism and excretion of perchlorate. Summarization of the available information and conclusions make the data more accessible to toxicologists and review panels for consideration in study prioritization and future reference dose development.

Particle-free gas generating mixture

Abstract: A gas generating mixture with 0.3% moisture content contains a fuel such as dry nitroguanidine with an oxygen value of not less than 35%, 35-50% NH4NO3 and ammonium perchlorate as oxidizing agents, 5% ZnO or CuO as phase stabilizer, 0 to 3% carbon black as combustion moderator and 0 to 5% of a processing additive such as polyethylene glycol.

Method and decomposing mixture for decomposition of solid rocket fuel

Abstract: FIELD: rocket fuel disposal. SUBSTANCE: safe disposal of solid rocket fuel based on ammonium perchlorate, aluminum, octagen, and hydrocarbon binders resulting in release of the above components is accomplished by treating rocket fuel with decomposing mixture containing organic solvent, activator, polar organic cosolvent, and cementation inhibitor, followed by separating and purifying released components. Ammonium perchlorate, aluminum, and octagen are further used as commercial products. EFFECT: improved efficiency and safety of process. 4 cl, 1 dwg, 1 tbln