Showing papers on "Ammonium perchlorate published in 2013"

Improvement of thermal decomposition properties of ammonium perchlorate particles using some polymer coating agents

Abstract: This research aimed to investigate the optimum conditions for modification of thermal decomposition properties of ammonium perchlorate (AP) particles through microencapsulation techniques. A solvent/non-solvent method has been used to perform microencapsulation of AP particles with some polymer-coating agents such as viton A and nitrocellulose (NC). Differential scanning calorimetry, thermogravimetry, and scanning electron microscopy have been exploited to investigate the thermal properties, heat of decomposition, and coating morphology of pure and coated samples. The preliminary results revealed that AP microparticle could be effectively coated with both NC and viton, but the latter significantly and unfavorably attenuated heat of decomposition of AP so NC was chosen as an appropriate coating agent for modification of thermal properties of AP. The thermal analysis of NC-coated samples, prepared at optimized coating conditions, showed that its first stage decomposition temperature increases about 12 °C with respect to uncoated sample and reaches to 305 °C. Also, the apparent activation energy (E), ΔG ≠, ΔH ≠, and ΔS ≠ of the decomposition processes of the pure and coated AP particles at the optimum conditions were obtained by non-isothermal methods that proposed by ASTM and Ozawa. Finally, the results of this investigation showed that microencapsulation of AP particles with fibrous NC enhance its heat of decomposition (~120 J g−1) with no obvious effect on kinetic parameters and thermal decomposition temperature.

Synthesis of FeTiO3 nanosheets with {0001} facets exposed: enhanced electrochemical performance and catalytic activity

Abstract: Ionic-liquid-assisted solution chemistry was initiated to prepare FeTiO3 nanosheets with {0001} polar facets exposed predominantly, which yielded improved electrochemical performance and excellent catalytic activity towards thermal decomposition of ammonium perchlorate.

Experimental data and model predictions of aluminium agglomeration in ammonium perchlorate-based composite propellants including plateau-burning formulations

Abstract: Sixteen propellant formulations based on ammonium perchlorate (AP), hydroxyl-terminated polybutadiene, and aluminium particles have been tested for size distribution of aluminium agglomerates emerging from their burning surface. The formulations are based on a bimodal size distribution of AP particles. Ten of the formulations exhibit one or two plateaus/mesa in their burning rate variation with pressure (zero/negative pressure exponent of burning rate). The relevant formulation variables, namely, coarse and fine AP sizes and coarse-to-fine ratio, aluminium size and content, and two different curing agents, have been varied. Tests are performed in the 1–10 MPa pressure range. A direct correlation between burning rate and agglomerate size exists for propellants with normal burning rate trends but a neutral or inverse correlation is observed for those exhibiting plateau burning behaviour. Larger the parent aluminium size, lesser the agglomeration, as expected; but the effect of aluminium content is non-monotonic. The coarse AP size influences the aluminium agglomerate size as expected from the pocket model regardless of plateau burning effects. The agglomerate size decreases with increase in fine AP size, however. A computer model developed earlier at this laboratory for prediction of aluminium agglomerates based on three-dimensional packing of particles and deduction of AP particles with attached leading edge diffusion flames is applied to the present formulations. The model under-predicts the agglomerate size, only marginally for propellants that do not exhibit plateau burning rate trends, but substantially, otherwise. This is because it does not take into account effects of binder melt flow and is independent of the curing agent of the binder.

Catalytic effect of commercial nano-CuO and nano-Fe2O3 on thermal decomposition of ammonium perchlorate

Abstract: Size reduction of the catalyst increases the surface area, and hence, the catalytic activity is also increased. The decrease in temperature of decomposition of ammonium perchlorate in the presence of nano-copper oxide and nano-ferric oxide is investigated within the scope of this study. Different mixes of ammonium perchlorate with nano-ferric oxide and nano-copper oxide were prepared. Differential scanning calorimetry test results show that addition of nanometer-sized ferric oxide and copper oxide leads to a significant decrease in higher decomposition temperature of ammonium perchlorate. The most significant decrease in the decomposition temperature was observed in the presence of 3% of nano-copper oxide.

Nano-Ammonium Perchlorate: Preparation, Characterization, and Evaluation in Composite Propellant Formulation

Abstract: Nanomaterials are finding applications in explosives and propellant formulations due to their large surface area and high surface energy. This high surface energy is responsible for the low activation energy and increase in burning rate of the composition. Therefore, a successful attempt has been made to prepare nano-ammonium perchlorate using a nonaqueous method by dissolving ammonium perchlorate (AP) in methanol followed by adding the dissolved AP to the hydroxyl-terminated polybutadiene (HTPB), homogenization, and vacuum distillation of the solvent. The nano-AP thus formed was characterized using a NANOPHOX particle size analyzer (Sympatec, Germany), transmission electron microscopy (FEI, Hillsboro, OR), X-ray diffraction (PANalytical B.V., The Netherlands) and scanning electron microscopy (Ikon Analytical Equipment Pvt. Ltd., Mumbai, India) for particle size, purity, and morphology, respectively. The thermal behavior of nano-AP was also studied using differential thermal analysis–thermo gravimetric an...

Agglomeration Characteristics of Aluminum Particles in AP/AN Composite Propellants

Abstract: Most solid rockets are powered by ammonium perchlorate (AP) composite propellant including aluminum particles. As aluminized composite propellant burns, aluminum particles agglomerate as large as above 100 μm diameter on the burning surface, which in turn affects propellant combustion characteristics. The development of composite propellants has a long history. Many studies of aluminum particle combustion have been conducted. Optical observations indicate that aluminum particles form agglomerates on the burning surface of aluminized composite propellant. They ignite on leaving the burning surface. Because the temperature gradient in the reaction zone near a burning surface influences the burning rate of a composite propellant, details of aluminum particle agglomeration, agglomerate ignition, and their effects on the temperature gradient must be investigated. In our previous studies, we measured the aluminum particle agglomerate diameter by optical observation and collecting particles. We observed particles on the burning surface, the reaction zone, and the luminous flame zone of an ammonium perchlorate (AP)/ammonium nitrate (AN) composite propellant. We confirmed that agglomeration occurred in the reaction zone and that the agglomerate diameter decreased with increasing the burning rate. In this study, observing aluminum particles in the reaction zone near the burning surface, we investigated the relation between the agglomerates and the burning rate. A decreased burning rate and increased added amount of aluminum particles caused a larger agglomerate diameter. Defining the extent of the distributed aluminum particles before they agglomerate as an agglomerate range, we found that the agglomerate range was constant irrespective of the added amount of aluminum particles. Furthermore, the agglomerate diameter was ascertained from the density of the added amount of aluminum particles in the agglomerate range. We concluded from the heat balance around the burning surface that the product of the agglomerate range and the burning rate was nearly constant irrespective of the added amount of aluminum particles. Moreover, the reduced burning rate increased the agglomerate range.

Synthesis, complexation of 1,2,3-(NH)-triazolylferrocene derivatives and their catalytic effect on thermal decomposition of ammonium perchlorate

Abstract: Ferrocenyl 1,2,3-triazoles 3a–3f and their Cu(II) or Zn(II) complexes have been synthesized and characterized. Compound 3d was structurally determined by X-ray crystallography. The DTA and TG measurements confirm the obvious catalytic effect of the representative compounds 3a and 3b on the decreasing of the decomposition temperature of ammonium perchlorate (AP) (by 32.3 and 36.2 °C respectively), whereas the Cu or Zn complexes of 3a lowers the thermal decomposition temperature of AP more dramatically, by 60.6 and 61.9 °C respectively. So ferrocenyl 1,2,3-triazoles 3a–3f and their Cu(II) or Zn(II) complexes are a kind of potentially high-burning-rate catalyst.

Nanoparticles of Transition Metals as Accelerants in the Thermal Decomposition of Ammonium Perchlorate, Part 62

Abstract: Four transition metal nanoparticles (TMNs) of 3d series (Cu, Co, Ni, and Fe) were prepared by hydrazine reduction of metal chloride in ethylene glycol at 60°C and characterized by X-ray diffraction (XRD). The XRD pattern showed average particle sizes for Cu, Ni, Co, and Fe of 16.7, 40.5, 27.4, and 35.0 nm, respectively. The activity of these TMN accelerants on the thermal decomposition of ammonium perchlorate (AP) was investigated using thermogravimetry (TG), differential scanning calorimetry (DSC), and ignition delay studies. Isothermal TG data were used to evaluate the kinetic parameters by model fitting as well as an isoconversional methods. The activation energy for thermal decomposition of AP was found to be 66.8, 68.7, 78.5, and 85.4 kJmol−1, respectively, for Co, Cu, Ni, and Fe, when they were mixed with AP. Hence, the order of activity was found to be Co > Cu > Ni > Fe. The accelerant effect of nanoparticles of TMNs was found to be better than their respective nano-oxides.

Preparation, characterization, and catalytic activity of rare earth metal oxide nanoparticles

Abstract: In present study, a series of rare earth metal oxide (CeO2, Pr2O3, and Nd2O3) nanoparticles have been prepared by sol–gel route using Ce(NO3)3·6H2O, Pr(NO3)3·6H2O and Nd(NO3)3·6H2O, and citric acid as precursor materials. Powder X-ray diffraction, scanning electron microscopy, and transmission electron microscopy are employed to characterize the size and morphology of the nano oxide particles. The particles are spherical in shape and the average particle size is of the order of 11–30 nm. Their catalytic activity was measured on the thermal decomposition of ammonium perchlorate and composite solid propellants (CSPs) by thermogravimetry (TG), TG coupled with differential thermal analysis (TG–DTA), and ignition delay measurements. The ignition delays and activation energies are found to decrease when rare earth metal oxide nanoparticles were incorporated in the system. Addition of metal oxide nanoparticles to AP led to shifting of the high temperature decomposition peak toward lower temperature and the burning rate of CSPs was also found to enhance. However, E a activation energy for decomposition was also found to decrease with each catalyst.

The diffusion flame structure of an ammonium perchlorate based composite propellant at elevated pressures

Abstract: Examination of the surface behavior and flame structure of a bimodal ammonium perchlorate (AP) composite propellant at elevated pressure was performed using high speed (5 kHz) planar laser-induced fluorescence (PLIF) from 1 to 12 atm and visible surface imaging spanning 1–20 atm. The dynamics of the combustion of single, coarse AP crystals were resolved using these techniques. It was found that the ignition delay time for individual AP crystals contributed significant to the particle lifetime only at pressures below about 6 atm. In situ AP crystal burning rates were found to be higher than rates reported for pure AP deflagration studies. The flame structure was studied by exciting OH molecules in the gas phase. Two types of diffusion flames were observed above the composite propellant: jet-like flames and v-shaped, inverted, overventilated, flames (IOF) lifted off the surface. While jet-like diffusion flames have been imaged at low pressures and simulated by models, the lifted IOFs have not been previously reported or predicted. The causes for the observed flame structures are explained by drawing on an understanding of the surface topography and disparities in the burning rates of the fuel and oxidizer.

Mesoporous Copper Oxide as a New Combustion Catalyst for Composite Propellants

Abstract: The use of powder additives to modify the burning rates of solid propellants and other energetic materials has been the topic of much study for several decades. This paper reports the discovery of the enhancement of the performance of ammonium perchlorate-based composite propellants by means of employing mesoporous copper oxide powder as a new burning rate catalyst in comparison to conventional (nonporous) copper oxide fillers. The burning rate measurements, obtained by the strand burner method, show that, with the addition of mesoporous fillers of copper oxide in aluminized composite propellants, higher rates (in excess of 22 mm/s at 7 MPa) are found over a broad pressure range. It was noticed that these high burning rates were accompanied by a more stable combustion, decreasing considerably the pressure index (0.40 versus 0.55). The thermal characterization of these highly energetic composite materials was also carried out by differential scanning calorimetry and thermogravimetric analysis, demonstrati...

Effects of Aluminum Nanoparticles on Thermal Decomposition of Ammonium Perchlorate

Abstract: The effects of aluminum nanoparticles (AlNs) on the thermal decomposition of ammonia perchlorate (AP) were investigated by DSC, TG-DSC and DSC-TG-MS-FTIR. Addition of AlNs resulted in an increase in the temperature of the first exothermic peak of AP and a decrease in the second. The processing of non-isothermal data at various heating rates with and without AlNs was performed using Netzsch Thermokinetics. The dependence of the activation energy calculated by Friedman's isoconversional method on the conversion degree indicated the decomposition process can be divided into three steps. They were C1/D1/D1 for neat AP, determined by Multivariate Non-linear Regression, and changed to C1/D1/F2 after addition of AlNs into AP. The isothermal curves showed that the thermal stability of AP in the low temperature stage was improved in the presence of AlNs.

Asymmetric Carbamate Derivatives Containing Secondary Nitramine, 2,2,2‐Trinitroethyl, and 2‐Fluoro‐2,2‐dinitroethyl Moieties

Abstract: In this work, the syntheses of 2, 2, 2-trinitroethyl-(2-nitro-2-azapropyl)carbamate (5), its analogue 2-fluoro-2, 2-dinitroethyl(2-nitro-2-azapropyl)carbamate (6), and the corresponding 2, 2, 2-trinitroethyl(2-nitro-2-azapropyl)nitrocarbamate (7) and 2-fluoro-2, 2-dinitroethyl(2-nitro-2-azapropyl)nitrocarbamate (8) are presented. The compounds were characterized thoroughly by vibrational spectroscopy (IR and Raman), multinuclear NMR spectroscopy, mass spectrometry, elemental analysis, differential scanning calorimetry measurements and single-crystal X-ray diffraction. In addition, the hitherto unknown low-temperature crystal structures of the starting materials 2-nitro-2-azapropyl chloride (1) and 2-nitro-2-azapropyl isocyanate (2) are presented. Owing to the positive oxygen balance of the carbamate derivatives, their suitability as potential oxidizers in energetic formulations with aluminium as the fuel is investigated and discussed. Standard enthalpies of formation were calculated at the CBS-4M level of theory. With these values and the experimental densities from room-temperature pycnometer measurements, several detonation parameters, such as the detonation pressures and velocities of the crude materials as well as the specific impulses of their formulations with aluminium, were computed by using the EXPLO5 (V6.01) computer program and compared with those of the corresponding mixtures with ammonium perchlorate as the oxidizer. Furthermore, the sensitivities towards impact, friction and electrostatic discharge were determined by using the BAM drop-hammer and friction tester as well as a small-scale electrical discharge device

Preparation of Magnesium‐based Hydrogen Storage Materials and Their Effect on the Thermal Decomposition of Ammonium Perchlorate

Abstract: Magnesium-based hydrogen storage materials (MgH2, Mg2NiH4, and Mg2Cu-H) were prepared and their structures were determined by XRD and ICP investigations. Mg2NiH4 has a monoclinic crystal structure and Mg2Cu-H is a mixture of MgCu2 and MgH2. The effects of magnesium-based hydrogen storage materials on the thermal decomposition of ammonium perchlorate (AP) were studied by thermal analysis (DSC). It was found that magnesium-based hydrogen storage materials show obvious boosting effects on the thermal decomposition of AP. The thermal decomposition peak temperature of AP was decreased, while the heat release of the decomposition of AP was increased. It was revealed that the effects of magnesium-based hydrogen storage materials on the decomposition of AP become stronger with increasing content. The influence mechanism on the thermal decomposition of AP is suggested as follows: hydrogen released from magnesium-based hydrogen storage materials and Mg, Ni, or Cu react with the decomposed products of AP.

Optimization of Potassium Dinitramide Preparation

Abstract: The synthesis of potassium dinitramide (KDN), an intermediate in the ammonium dinitramide (ADN) synthesis, was optimized to reduce the costs of the ADN synthesis in order to facilitate competitiveness of this oxidizer with ammonium perchlorate (AP). The optimal conditions for the synthesis of KDN like feedstock molar ratio, nitration time, and temperature were determined. KDN was obtained in ca. 48 % yield. The modifications introduced allowed to reduce feedstock consumption and energy intensity of the process.

Combustion Behavior of Solid Oxidizer/Gaseous Fuel Diffusion Flames

Abstract: The diffusion flame combustion behavior of several solid oxidizers (ammonium nitrate, phase-stabilized ammonium nitrate, ammonium perchlorate, and ammonium dinitramide) in combination with a hydrocarbon fuel (ethylene) was examined. The oxidizers were first analyzed by differential scanning calorimetry, thermal gravimetric analysis, and evolved gas analysis to gain an understanding of their basic decomposition characteristics. Next, an opposed flow burner was used to establish a diffusion flame between the decomposition products of the oxidizer(s) and the fuel. Regression rates of the solid oxidizer were measured by a linear variable displacement transducer as a function of fuel flow rate. Ammonium dinitramide demonstrated the highest linear regression rate characteristics by up to two orders of magnitude, followed by ammonium perchlorate, phase-stabilized ammonium nitrate, and finally ammonium nitrate. When comparing mass burning rates, ammonium perchlorate compares favorably to solid fuels such as hydro...

Intermolecular interaction of a neutral polymeric bonding agent containing n-vinylpyrrolidone units with ammonium perchlorate and keto-rdx

Abstract: The interaction of a new neutral polymeric bonding agent (NPBA) containing N-Vinylpyrrolidone units with two types of oxidizers (ammonium perchlorate and Keto-RDX) was investigated by X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR). NPBA forms a layer of film on the surface of oxidizers. The paper gives hypothetical mechanisms for improving significantly mechanical properties by addition of the neutral polymeric bonding agent (NPBA).

High-Pressure Burning Rate Studies of Solid Rocket Propellants

Abstract: Increasedrocketmotorperformanceisamajordriverinthedevelopment of solid rocket propellant formulations for chemical propulsion systems. The use of increased operating pressure is an option to improve performance potentially without the cost of reformulation. A technique has been developed to obtain burning rate data across a range of pressures from ambient to 345 MPa. The technique combines the use of a low loading density combustion bomb with a high loading density closed bomb technique. A series of nine ammonium perchlorate (AP) based propellants were used to demonstrate the use of the technique, and the ‘

Modeling Composite Solid Propellant with Catalytic Additives

Abstract: This paper presents current work on improving the accuracy of solid composite propellant modeling to include catalytic additives and using it to develop a better understanding of the working mechanism of burning rate enhancement. To this end, isolating the physical mechanism where the catalyst impacts the composite propellant burning rate was studied. To accomplish this goal, a parametric study was conducted by systematically varying different aspects of the burning that are covered by the simple model. The results from the model were compared to experimental data collected from propellants formulated in the authors’ laboratory both with and without catalytic nanoparticle additives, namely TiO2. Some variations of the TiO2 additive tested included powder that was produced by spray-drying with and without heat treating as well as titania that was premixed into the binder before making the ammonium perchlorate (AP)/binder mixture. The propellants are compared to two ammonium perchlorate and hydroxyl-terminated polybutadiene (HTPB) baselines with 80% and 85% solids loading. Advancements on the Beckstead-Derr-Price (BDP) model to incorporate catalytic additives were accurately demonstrated using the technique outlined in this paper. This study determined that the catalyst primarily impacted the condensed phase by increasing the reaction rate of the condensed-phase AP; this conclusion was based on the fact that only changes in the condensed-phase AP reaction rate produced the pressure dependence and absolute magnitude of the increased burning rates due to the TiO2-based additive that were seen in the data. In contrast, an unrealistically high increase in the pressure dependence was found if the binder kinetics were modified to match the observed burning rates, and changes in the primary flame kinetics only varied the slope of the burning rate curve; these results are not supported by the experimental data. Furthermore, an empirical constant (Ωc) was found to model the effect of the additives on the AP reaction rate in the form of a burning-ratemagnitude modifier. Typically, an increase of around 50 to 60% in the reaction rate was observed for the use of nano-titania in an 85% AP propellant.