Showing papers on "Ammonium perchlorate published in 2010"

Hierarchical ZnO Nanorod-Assembled Hollow Superstructures for Catalytic and Photoluminescence Applications

Abstract: In this study, hierarchically complex hollow cage-like superstructures assembled by ZnO nanorods have been successfully constructed with water-soluble biopolymer sodium carboxymethyl cellulose as crystal growth modifiers. The number of the hollow cage could be adjusted from single-cage, double-cage, multi-cage to connected-cage. A possible formation mechanism of the hollow superstructures has also been proposed. The catalytic study shows that these ZnO superstructures have good abilities to enhance propellant combustion of ammonium perchlorate (an important oxidizer used in solid rocket propellants), by decreasing its decomposition temperature to as low as 285 °C. Photoluminescence studies reveal that the increase in the cage number leads to an increase in the relative photoluminescence intensity around 500 to 700 nm, which might be attributed to the increase in radiative defects at the interface of the components of the ZnO hollow structure with the growth in cage number.

Microstructure Effects in Aluminized Solid Rocket Propellants

Abstract: Experiments concerning the ballistic characterization of several nanoaluminum (nAl) powders are reported. Most studies were performed with laboratory composite solid rocket propellants based on ammonium perchlorate as oxidizer and hydroxyl-terminated polybutadiene as inert binder. The ultimate objective is to understand the flame structure of differently metallized formulations and improve their specific impulse efficiency by mitigating the two-phase losses. Ballistic results confirm, for increasing nAl mass fraction or decreasing nAl size, higher steady burning rates with essentially the same pressure sensitivity and reduced average size of condensed combustion products. However, aggregation and agglomeration phenomena near the burning surface appear noticeably different for microaluminum (μAl) and nAl powders. By contrasting the associated flame structures, a particle-laden flame zone with a sensibly reduced particle size is disclosed in the case of nAl. Propellant microstructure is considered the main controlling factor. A way to predict the incipient agglomerate size for μAl propellants is proposed and verified by testing several additional ammonium perchlorate/hydroxyl-terminated polybutadiene/aluminum formulations of industrial manufacture.

Kinetic Stability and Propellant Performance of Green Energetic Materials

Abstract: A thorough theoretical investigation of four promising green energetic materials is presented. The kinetic stability of the dinitramide, trinitrogen dioxide, pentazole, and oxopentazole anions has been evaluated in the gas phase and in solution by using high-level ab initio and DFT calculations. Theoretical UV spectra, solid-state heats of formation, density, as well as propellant performance for the corresponding ammonium salts are reported. All calculated properties for dinitramide are in excellent agreement with experimental data. The stability of the trinitrogen dioxide anion is deemed sufficient to enable synthesis at low temperature, with a barrier for decomposition of approximately 27.5 kcal mol−1 in solution. Oxopentazolate is expected to be approximately 1200 times more stable than pentazolate in solution, with a barrier exceeding 30 kcal mol−1, which should enable handling at room temperature. All compounds are predicted to provide high specific impulses when combined with aluminum fuel and a polymeric binder, and rival or surpass the performance of a corresponding ammonium perchlorate based propellant. The investigated substances are also excellent monopropellant candidates. Further study and attempted synthesis of these materials is merited.

The effect of specific surface area of TiO2 on the thermal decomposition of ammonium perchlorate

Abstract: The thermal decomposition of ammonium perchlorate (AP) is considered to be the first step in the combustion of AP-based composite propellants. In this report, the effect of the specific surface area of titanium oxide (TiO2) catalysts on the thermal decomposition characteristics of AP was examined with a series of thermal analysis experiments. It was clear that the thermal decomposition temperature of AP decreased when the specific surface area of TiO2 increased. It was also possible that TiO2 influences the frequency factor of AP decomposition because there was no observable effect on the activation energy.

Synthesis of nitrogen-doped ZnO nanocrystallites with one-dimensional structure and their catalytic activity for ammonium perchlorate decomposition

Abstract: In this study, nitrogen-doped ZnO (N-doped ZnO) nanocrystallites with a one-dimensional structure were synthesized successfully via an advanced wet chemical technique, and their microstructures were characterized by SEM, HRTEM, XRD, and XPS. The catalytic performance of the as-synthesized samples was evaluated by investigating their effect on the thermal decomposition of ammonium perchlorate (AP) by DSC and TG. Results indicate that the morphologies of N-doped ZnO nanocrystallites mainly depend on the presence of urea in the raw materials. Nanocrystallites with peculiar morphology, in which numerous nanorods with a diameter of 40–50 nm arrange orderly and symmetrically in hollow nanotubes with a diameter of 200–800 nm and thickness of 20–30 nm, can be produced when urea is used as a raw material. The as-synthesized N-doped ZnO sample with peculiar morphology drives the thermal decomposition peak of AP decrease about 163 °C with a strong decomposition heat about 1,325 J/g, and the activation energy also decreases from 178.22 to 93.51 kJ/mol. The enhanced catalytic activity of N-doped ZnO sample can be attributed to oxygen vacancies and other defects induced by the doping of nitrogen.

Preparation of CoFe 2 O 4 nanocrystallites by solvothermal process and its catalytic activity on the thermal decomposition of ammonium perchlorate

Abstract: Nanometer cobalt ferrite (CoFe2O4) was synthesized by polyol-medium solvothermal method and characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), and selected area electron diffraction (SAED). Further, the catalytic activity and kinetic parameters of CoFe2O4 nanocrystallites on the thermal decomposition behavior of ammonium perchlorate (AP) have been investigated by thermogravimetry and differential scanning calorimetry analysis (TG-DSC). The results imply that the catalytic performance of CoFe2O4 nanocrystallites is significant and the decrease in the activation energy and the increase in the rate constant for AP further confirm the enhancement in catalytic activity of CoFe2O4 nanocrystallites. A mechanism based on an proton transfer process has also been proposed for AP in the presence of CoFe2O4 nanocrystallites.

Performance of Ammonium-Perchlorate-Based Composite Propellant Containing Nanoscale Aluminum

Abstract: Several composite propellant mixtures of hydroxyl-terminated polybutadiene, ammonium perchlorate, and aluminum were prepared with and without the addition of small percentages of nanoscale aluminum and tested in a strandburneratpressuresupto34.5MPa.Theeffectofmonomodalversusbimodalammoniumperchlorateparticle size, coarse aluminum particle size, nano aluminum particle size, and coarse-to-fine ratios on burning rate and manufacturability were explored. A significant conclusion of the present study is that the addition of nanoscale aluminum does not always ensure an increase in the propellant’s burning rate when produced using conventional methods. It was observed that over the range of mixtures and pressures explored, a bimodal oxidizer is required for the nanoscale aluminum to affect the burning rate, and that a monomodal oxidizer tended to nullify any influence of thenanoscalealuminum.Insomecases,theadditionofnanosizedaluminumdecreasedtheburningrate.Thelevelof burning-rateincreaseordecreasedependedonthebimodalormonomodalammoniumperchlorateparticlesizes,the coarse aluminum particle size, and the pressure range.

Performance evaluation of commercial copper chromites as burning rate catalyst for solid propellants

Abstract: Copper chromites are well known as burning rate catalysts for the combustion of composite solid propellants, used as a source of energy for rocket propulsion. The propellant burning rate depends upon the catalyst characteristics such as chemical composition and specific surface area. In this work, copper chromite samples from different suppliers were characterized by chemical analysis, FT-IR spectroscopy and by surface area measurement (BET). The samples were then evaluated as burning rate catalyst in a typical composite propellant formulation based on HTPB binder, ammonium perchlorate and aluminum. The obtained surface area values are very close to those informed by the catalyst suppliers. The propellant processing as well as its mechanical properties were not substantially affected by the type of catalyst. Some copper chromite catalysts caused an increase in the propellant burning rate in comparison to the iron oxide catalyst. The results show that in addition to the surface area, other parameters like chemical composition, crystalline structure and the presence of impurities might be affecting the catalyst performance. All evaluated copper chromite samples may be used as burning rate catalyst in composite solid propellant formulations, with slight advantages for the SX14, Cu-0202P and Cu-1800P samples, which led to the highest burning rate propellants.

Stoichiometric analysis of ammonium nitrate and ammonium perchlorate with nanosecond laser induced breakdown spectroscopy

Abstract: We present our results on the stoichiometric analysis of ammonium nitrate (AN) and ammonium Perchlorate (AP) studied using laser induced breakdown spectroscopy (LIBS) with nanosecond pulses. The LIBS spectra collected for AP and AN, without any gating and using a high resolution spectrometer, exhibited characteristic lines corresponding to O, N, H, C, and K. The Oxygen line at 777.38 nm and three Nitrogen lines (N 1 , N 2 , N 3 ) at 742.54 nm, 744.64 nm, 747.12 nm were used for evaluating the Oxygen/Nitrogen ratios. The intensities were calculated using area under the peaks and normalized to their respective transition probabilities and statistical weights. The O/N 1 ratios estimated from the LIBS spectra were ~4.94 and ~5.11 for AP and O/N 3 ratios were ~1.64 and ~1.47 for AN obtained from two independent measurements. The intensity ratios show good agreement with the actual stoichiometric ratios - four for AP and one for AN.

Nanodispersed metal powders in high-energy condensed systems

Abstract: The results of earlier published Russian and foreign works concerning the use of nanodispersed metal powders in high-energy condensed systems (HECSs) are analyzed and generalized. Modern technological achievements allow one to produce powders of aluminum, boron, and other metals, as well as their alloys and oxides, and make them commercially available. This has resulted in a boom in studies on the possibility of improving HECS characteristics by introducing metal nanopowders in Russia, Europe, Canada, and the United States. The results of some works show that introducing nanopowders of alumina and other metals into rocket propellants, explosives, and pyrotechnic compositions increases their combustion rate and detonation properties. The composition of a double-base propellant (in which the liquid fuel contains 50–150-nm boron nanoparticles and a liquid mixture of hydrogen peroxide and ammonium nitrate is used as an oxidizer) and the composition of a solid rocket propellant based on polybutadiene with end hydroxyl groups, ammonium perchlorate, and 13.0–15.0% boron nanoparticles (which improve the combustion and increase the conversion of the propellant) are of some interest.

Investigation of combustion of HEM with aluminum nanopowders

Abstract: A number of problems related to the utilization of nanosize aluminum powders as a combustible component of perspective compositions of high-energy materials is considered. The technology of producing nanopowders using the technique of conductor electrical explosion and the method of dispersed powder composition analysis are shown. The results of experimental studies of conductive and radiant ignition of model propellant compositions containing aluminum nanopowder, as well as the results of investigating the rate of stationary and non-stationary combustion of the given systems, are given. The results of an investigation of the ignition and combustion of ecologically safe propellant systems based on a dual oxidant (ammonium perchlorate and ammonium nitrate, which partially replaces it) containing aluminum nanopowder are demonstrated.

Computational study on nitronium squarate - potential oxidizers for solid rocket propulsion?

Abstract: The enthalpies of formation for solid ionic nitronium squarate, [NO2]2[C4O4], and covalent squaric acid dinitrate ester, O2N-C4O4-NO2, were calculated using the complete basis set (CBS-4M) method of Petersson and coworkers in order to obtain very accurate energies. The covalent form (O2N-C4O4-NO2) was identified as the more stable isomer. The combustion parameters with respect to possible use as ingredients in solid rocket motors for both stable species were calculated using the EXPLO5 code. The performance of an aluminized formulation with covalently bound dinitrate ester (O2N-C4O4-NO2) was shown to be comparable to that of ammonium perchlorate/aluminum. This makes squaric acid dinitrate ester a potentially interesting perchlorate-free and environmentally benign oxidizer for solid rocket propulsion.

Method for producing solid composite aluminized propellants, and solid composite aluminized propellants

Abstract: The present invention mainly relates to a method for producing a solid composite propellant (with a polyurethane binder filled with ammonium perchlorate and aluminum). Typically, the ammonium perchlorate charge of the propellant is obtained from at least two charges each having a specific single mode particle size distribution. It is thus possible to reduce the thrust oscillations and the alumina deposits at the rear bottom of the engine. The invention also relates to a solid composite propellant, to solid propellant charges, and to related rocket engines.

Ageing behaviour of composite rocket propellant formulations inves- tigated by DMA, SGA and GPC

Abstract: Solid rocket propellants (SRP) based on HTPB / AP / Al (binder hydroxyl terminated polybutadiene / ammonium perchlorate / aluminium powder) are at time the choice to achieve high performance with high specific impulses. Such propellants change their properties with time. Ageing mechanisms are: after-curing, chain rupture by mechanical overload during temperature cycling, oxidative hardening together with loss in strain capability, oxidative chain scissioning, dewetting between particulate fillers (especially AP) and binder matrix. In this work DMA (Dynamic Mechanical Analysis) in torsion mode and Sol-Gel-Analysis (SGA) have been employed together with SEM (Scanning Electron Microscopy) and GPC (Gel Permeation Chromatography) to elucidate the ageing behaviour of four HTPB-based SRP, whereby the particle size of aluminium powder was changed also. The accelerated ageing range was between 60°C and 90°C with ageing times adjusted to a thermal equivalent load of 15 to 20 years at 25°C. The investigations with DMA revealed distinct changes in the shape of the loss factor curve. The loss factor gives the part of applied deformation energy, which is consumed by the sample. The other part is transported through the sample to the response detector. Detailed analysis of the shape of the loss factor showed that three parts of molecular rearrangement types can be identified during the total transition of the material from energy-elastic to the entropy-elastic state. The results of SGA showed a complex change in soluble or extractable polymeric binder part. Both cross-linking and to some part also chain scissioning occur, which could be recognized by the changes of the molar mass distribution functions of the extractable binder part.

Assessing the Mixedness of Composite Solid Rocket Propellants Using Fluorescent Particles

Abstract: A new diagnostic technique was developed for assessing the effectiveness of mixing techniques of solid composite propellants using nanoparticle additives. The diagnostic uses nanosized quantum dots in suspension or micron-sized powders that are mixed into the propellant in place of the additives. Upon exposure to an ultraviolet light source, the particles fluoresce, hence serving as tracers to assess the uniformity of the mixture and therefore the effectiveness of the mixing procedure. Collection of the image using a digital camera provides data on intensity variations in the fluorescent signal, allowing for quantitative assessment of uniformity and mixedness. Various mixtures involving hydroxyl-terminated polybutadiene binder and ammonium perchlorate oxidizer were manufactured at various levels of mixing to test the diagnostic. In addition to confirming the uniformity of the nanosized particles using the target mixing procedure, variations in mixing quality and comparisons between mechanically and hand-mixed propellants showed distinct differences correlating to the mixedness of each propellant that was supported with data from burning rate studies. The present diagnostic can therefore also be used to assess the mixedness of propellants that do not contain nanoparticle additives. Other potential applications include curing agent dispersion assessment and linking homogeneity to mixedness and mechanical properties.

Synthesis, characterization and catalytic effect of bimetallic nanocrystals on the thermal decomposition of ammonium perchlorate

Abstract: Bimetallic nanocrystals, viz., Cu-Co, Cu-Fe and Cu-Zn, have been prepared by hydrazine reduction in ethylene glycol and characterized by X-ray diffraction, transmission electron microscopy and energy dispersive X-ray analysis. The particle size of the nanocrystals is found to be of the order of 10-38 nm. These nanocrystals have been found to have a significant catalytic effect on the thermal decomposition of ammonium perchlorate and also on the burning rate of composite solid propellants. The catalytic characteristics have been attributed to the large surface area and the active chemical nature of the bimetallic nanocrystals.

Thermal Behavior and Non-isothermal Decomposition Reaction Kinetics of NEPE Propellant with Ammonium Dinitramide

Abstract: Thermal decomposition behavior and non-isothermal decomposition reaction kinetics of nitrate ester plasticized polyether NEPE propellant containing ammonium dinitramide (ADN), which is one of the most important high energetic materials, were investigated by DSC, TG and DTG at 01 MPa The results show that there are four exothermic peaks on DTG curves and four mass loss stages on TG curves at a heating rate of 25 K·min−1 under 01 MPa, and nitric ester evaporates and decomposes in the first stage, ADN decomposes in the second stage, nitrocellulose and cyclotrimethylenetrinitramine (RDX) decompose in the third stage, and ammonium perchlorate decomposes in the fourth stage It was also found that the thermal decomposition processes of the NEPE propellant with ADN mainly have two mass loss stages with an increase in the heating rate, that is the result of the decomposition heats of the first two processes overlap each other and the mass content of ammonium perchlorate is very little which is not displayed in the fourth stage at the heating rate of 5, 10, and 20 K·min−1 probably It was to be found that the exothermal peak temperatures increased with an increase in the heating rate The reaction mechanism was random nucleation and then growth, and the process can be classified as chemical reaction The kinetic equations of the main exothermal decomposition reaction can be expressed as: dα/dt=101277(3/2)(1−α)[−ln(1−α)]1/3 e−1723×104/T The critical temperatures of the thermal explosion (Tbe and Tbp) obtained from the onset temperature (Te) and the peak temperature (Tp) on the condition of β0 are 46141 and 45802 K, respectively Activation entropy (ΔS≠), activation enthalpy (ΔH≠), and Gibbs free energy (ΔG≠) of the decomposition reaction are −702 J·mol−1·K−1, 12619 kJ·mol−1, and 12931 kJ·mol−1, respectively

Composite Rocket Propellants Based on Thermoplastic Elastomer Binders

Abstract: The objective of this paper is to present new binder systems that can be applied in composite rocket propellants, to improve properties of these propellants not only for better performance, but also to reduce waste and pollution. These novel systems are based on the thermoplastic elastomer (TPE) binders, which consists of copolymers with the addition of a plasticizer, and additives. The effect of the novel TPE binder systems on the burning rate and mechanical properties of AP based propellants was studied. The results show that propellants based on the novel TPE binders have a better energy performance than today’s workhorse hydroxyl terminated polybutadine/ammonium perchlorate propellant, exhibit a similar range of burning rate, possess appropriate mechanical properties, and exhibit good processing and aging characteristics at low cost.

Conductivity and Thermal Behavior of Proton Conductor Based on Poly(vinylpyrrolidone) Complexed with Ammonium Perchlorate

Abstract: Electrical, thermal and mechanical studies were carried out on proton conducting electrolytes, based on poly(vinylpyrrolidone) (PVP) with ammonium perchlorate (NH4ClO4). Considering both the conductivity and manageability of films, the optimal PVP and NH4ClO4 weight ratio was 7:3 with 15 wt% water, exhibiting a protonic conductivity of 0.91×10−44 Scm−1 at 30°C and 1.12×10−2 Scm−1 at 80°C. Thermal studies showed that the crystallites of excess NH4ClO4 were formed inside the electrolyte, but they were decreased significantly with increasing water content. Cellulose was mixed to improve the mechanical strength of the hydrated samples. In a reinforced matrix of PVP/Cellulose complexes, the water retention property was improved significantly, thus exhibiting a slower decrease in conductivity over time.

Onset and development of convective burning in highly porous charges of ammonium perchlorate and its mixtures with aluminum

Abstract: The onset and development of convective burning in the charges with a high porosity prepared from the finely dispersed ammonium perchlorate and its mixtures with aluminum ASD-4 is studied. The experiments were carried out in a constant volume bomb with the record of the pressure-time history and in the confinement with a slit, which makes it possible to perform simultaneously the photographic and piezometric recording of the process. Special attention is given to the mixtures with the increased aluminum content. The minimum lengths of samples are determined at which convective burning or explosion occur. The dependence of these lengths on the aluminum concentration in the mixture is determined. The possibility of convective burning and low-velocity detonation in ammonium perchlorate without the combustible additive is shown. It is established that the introduction of aluminum causes the ignition of the dispersed suspension behind the front of convective burning with the formation of the brightly glowing high-pressure zone (the secondary wave), which intensively expands in both sides from the place of origin. When the secondary wave overtakes the front of convective burning, the low-velocity detonation appears. The obtained results are of interest for explosion safety of the mixtures of ammonium perchlorate with aluminum and for designing generators of high-temperature suspensions with aluminum particles.