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Catalytic Role of Boron Nitride in the Thermal Decomposition of Ammonium PerchlorateGrossman, Kevin 01 January 2015 (has links)
The decomposition of Ammonium Perchlorate (AP), a strong oxidizer used in solid rocket propellant, is widely studied in an attempt to increase the burn characteristics of propellants. Many materials have been shown to catalyze its decomposition, but little is known about the mechanism by which AP decomposition becomes catalyzed. In this study, Boron Nitride (BN) nanostructures, a material previously unknown to act as a catalyst, is studied. The decomposition reaction is studied by thermo-gravimetric analysis / differential scanning calorimetry, X-ray photoelectron spectroscopy, fourier transform infrared spectroscopy, transmission electron microscopy and scanning electron microscopy. The goal of this study is to discover the activation energy of this catalyst reaction, intermediary products of the reaction, mechanism of reaction and end state of the boron nitride nanostructures (ie, if the BN acts as a true catalyst, or participates on the overall reaction and has some end state that*s different from the initial state). Four variations of BN have been synthesized using a hydrothermal process; BN nanoribbons, Boron Rich BN, Nitrogen-Rich BN, and high surface area BN. It is shown that the decomposition of AP is significantly altered when in the presence of BN and the mechanism through which BN catalyzes the decomposition is most likely the presence of oxidized nitrogen species on the BN material.
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Tailoring the physical properties of energetic materialsWard, Daniel W. January 2017 (has links)
Energetic materials are a class of material that have large amounts of chemical energy stored within their molecular structure. This energy is released upon decomposition, generally in the form of rapidly expanding, hot gases. They are therefore used for a wide range of applications such as; mining, military, and space exploration, and there is therefore a strong desire to improve the overall performance and safety of such materials. On account of reduced sensitivity to initiation by shock and impact, 2,4-dinitroanisole (DNAN) is a potential replacement for 2,4,6-trinitrotoluene (TNT) in melt-cast formulations for military applications. However, up to 15 % irreversible growth of DNAN has been previously observed upon thermal cycling and is a key reason why DNAN has not yet been universally accepted as a replacement for TNT. DNAN exhibits a complex system of polymorphism. One particular transition from DNAN-II to DNAN-III, which occurs at 266 K, has been observed in these studies to cause 8 - 10 % growth of DNAN-II pellets when temperature cycled for 30 cycles between 256 K and 276 K. What was even more concerning was the appearance of cracking of DNAN pellets after being temperature cycled. Doping the crystal structure of DNAN-II with related molecules, such as 2,4-dinitrotoluene or 2,4-dinitroaniline, was investigated in order to probe how steric and electronic factors affect the transition. The addition of varying amounts of 2,4-dinitroaniline suppressed this transition to varying extents and ultimately as low as 150 K with 10 mol% 2,4-dinitroaniline, and potentially eliminated entirely. This doped material has been designated as phase-stabilised DNAN (PS-DNAN). Temperature cycling of PS-DNAN was conducted over the same 256-276 K range, and this material showed no evidence of irreversible growth compared to undoped DNAN pellets, on account of suppression of the II-III transition. The production of PS-DNAN is therefore a possible route to avoiding problematic irreversible growth in DNAN formulations. Melt-casting of DNAN in a sealed environment consistently results in the metastable form-II, which has proven to be stable for in excess of 32 weeks. However, exposure to seeds of form-I, either via deliberate or accidental seeding, rapidly converted the material to the thermodynamically more stable form-I. This transition was accelerated by increasing temperature which rapidly converted pellets of DNAN-II to DNAN-I. When DNAN-I pellets were temperature cycled, they did not undergo a transition to form-III, and as a result did not illustrate irreversible growth. This presents another approach to avoiding problematic growth in DNAN-based materials. Whilst being one of the most widely used oxidisers in propellant formulations, ammonium perchlorate (AP) has several issues; the formation of porous ammonium perchlorate (PAP) can seriously affect the sensitivity of propellants, the hygroscopicity of AP makes handling and manufacture of formulations difficult, and spherical AP exhibits poor binding properties to the polymer binders used in propellant formulations. Several different approaches were taken to combat these issues. Co-crystallisation of AP was attempted in order to produce new AP co-crystals with reduced reactivity towards the formation of PAP. A theoretical based approach using COSMOtherm was used for rapid screening and selection of potential co-formers to be used in lab-based co-crystallisation trials. Co-crystallisation was attempted using multiple stoichiometries and multiple solvents by solvent evaporation, cooling crystallisation, and Resonant Acoustic Mixing methods. Unfortunately no new co-crystals were obtained, presumably on account of the ionic nature of AP which makes co-crystallisation difficult. The mass of untreated AP increased by 0.027% in a humid environment (90% RH) due to the uptake of water, which resulted in significant caking and hence hindering the processability of AP. In an attempt to counteract the hygroscopicity and improve the processability of AP, particles of AP were coated in graphene nanoplatelets using the technique of Resonant Acoustic Mixing. Low mixing energy (G-force) (30 G) resulted in poor coating of AP, but the flowability of this mixure after exposure to moisture was significantly enhanced, most probably as a result of graphene acting as an effective lubricant. Higher mixing energy (90-100 G) was required to break up agglomerates of graphene nanoplatelets and resulted in AP particles efficiently coated with graphene (APGR). Differential scanning calorimetry showed that the energy released upon decomposition of APGR was greater than pure AP, or AP mixed with graphene, due to the intimacy of the AP particle surface and the graphene coating.
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Microbial reduction of perchlorate with elemental ironSon, Ahjeong. January 2006 (has links)
Thesis (Ph.D.)--University of Delaware, 2006. / Principal faculty advisor: Daniel K. Cha, Dept. of Civil & Environmental Engineering. Includes bibliographical references.
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Decomposition of ammonium perchlorate encapsulated nanoscale and micron-scale catalyst particlesSpencer A Fehlberg (8774588) 29 April 2020 (has links)
<p>Iron oxide is the most common catalyst in
solid rocket propellant. We have previously demonstrated increased performance
of propellant by encapsulating iron oxide particles within ammonium perchlorate
(AP), but only nanoscale particles were used, and encapsulation was only
accomplished in fine AP (~20 microns in diameter). In this study, we extended the
size of particle inclusions to micron-scale within the AP particles as well the
particle sizes of the AP-encapsulated catalyst particles (100s of microns) using
fractional crystallization techniques with the AP-encapsulated particles as
nucleation sites for precipitation. Here we report catalyst particle inclusions
of micron-scale, as well as nanoscale, within AP and present characterization
of this encapsulation. Encapsulating micron-sized particles and growing these
composite particles could pave the way for numerous possible applications. A
study of the thermal degradation of these AP-encapsulated particles compared
against a standard mixture of iron oxide and AP showed that AP-encapsulated
micron-scale catalyst particles exhibited similar behavior to AP-encapsulated
nanoscale particles. Using computed tomography, we
found that catalyst particles were dispersed throughout the interior of coarse
AP-encapsulated micron-scale catalyst particles and decomposition was induced
within these particles around catalyst-rich regions.</p>
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Novel Nanostructures And Processes For Enhanced Catalysis Of Composite Solid PropellantsDraper, Robert 01 January 2013 (has links)
The purpose of this study is to examine the burning behaviour of composite solid propellants (CSP) in the presence of nanoscale, heterogenous catalysts. The study targets the decomposition of ammonium perchlorate (AP) as a key component in the burning profile of these propellants, and seeks to identify parameters of AP decomposition reaction that can be affected by catalytic additives. The decomposition behavior of AP was studied in the presence of titanium dioxide nanoparticles in varying configurations, surface conditions, dopants, morphology, and synthesis parameters with the AP crystals. The catalytic nanoparticles were found to enhance the decomposition rate of the ammonium perchlorate, and promote an accelerated burning rate of CSP propellants containing the additives. Furthermore, different configurations were shown to have varying degrees of effectiveness in promoting the decomposition behaviour. To study the effect of the catalyst’s configuration in the bulk propellant, controlled dispersion conditions of the nanoparticle catalysts were created and studied using differential scanning calorimetry, as well as model propellant strand burning. The catalysts were shown to promote the greatest enthalpy of reaction, as well as the highest burn rate, when the AP crystals were recrystalized around the nanoparticle additives. This is in contrast to the lowest enthalpy condition, which corresponded to catalysts being dispersed upon the AP crystal surface using bio-molecule templates. Additionally, a method of facile, visible light nanoparticle tracking was developed to study the effect of mixing and settling parameters on the nano-catalysts. To accomplish this, the titania nanoparticles were doped with fluorescent europium molecules to track the dispersion of the catalysts in the propellant binder. This method was shown to succesfully allow for dispersion and agglomeration monitoring without affecting the catalytic effect of the TiO2 nanoparticles.
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HHARJONO_MASTERS_THESIS-6.pdfHanson-Lee Nava Harjono (14232875) 09 December 2022 (has links)
<p>In an AP-HTPB propellant microstructure, the local strain rate depends on the AP crystal size and the material, while the local temperature rate depends on the impact velocity, AP crystal size, and the material. Larger AP crystals lead to higher local strain rates and higher local temperature rates, which means hot spots are more likely to occur in AP-HTPB propellants with more large AP crystals.</p>
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Effects of ammonium perchlorate exposure on the thyroid function and the expression of thyroid-responsive genes in Japanese quail embryos and post hatch chicksChen, Yu 05 August 2008 (has links)
Perchlorate ion interferes with thyroid function by competitively inhibiting the sodium-iodide symporter, thus blocking iodide uptake into the thyroid gland. In this study, the effect of perchlorate exposure on thyroid function and thyroid-responsive gene expression were examined in (1) embryos from eggs laid by perchlorate-treated Japanese quail hens and (2) perchlorate-treated young Japanese quail. I hypothesized that perchlorate exposure would decrease thyroid function and that the consequent hypothyroidism would alter the expression of thyroid sensitive genes. Laying Japanese quail hens were treated with 2000 mg/l and 4000 mg/l ammonium perchlorate in drinking water. Eggs from these hens were incubated. Embryos, exposed to perchlorate in the egg, were sacrificed at day 14 of the 16.5 day incubation period. Japanese quail chicks, 4-5 days old, were treated with 2000 mg/l ammonium perchlorate in drinking water for 2 and 7.5 weeks. Thyroid status was evaluated by measuring plasma thyroid hormone concentrations, thyroid gland weight and thyroidal thyroid hormone storage. Expression of thyroid-responsive genes was evaluated by measuring the mRNA levels of Type 2 deiodinase (D2) in the brain and liver, RC3/neurogranin mRNA level in the brain and Spot 14 mRNA level in the liver. Maternal perchlorate exposure led to embryonic hypothyroidism, demonstrated by thyroid hypertrophy and very low embryonic thyroidal TH storage. Embryonic hypothyroidism decreased body growth and increased D2 mRNA level in the liver (a presumed compensatory response to hypothyroidism) but did not affect the mRNA levels of D2 and RC3 in the brain. Spot 14 mRNA was not detected in embryonic liver.
In the second part of the study, quail chicks showed early signs of hypothyroidism after two weeks of 2000 mg/l ammonium perchlorate exposure; plasma concentration and thyroid gland stores of both T4 and T3 were significantly decreased. After 7.5 weeks of perchlorate exposure, all thyroid variables measured indicated that the chicks had become overtly hypothyroid. D2 mRNA level was increased, a compensatory response to hypothyroidism, and spot 14 mRNA level was decreased, a substrate-driven response in the liver of quail chicks after two weeks of perchlorate exposure. However, no difference was observed in the mRNA levels of D2 and spot 14 in the liver after 7.5 weeks of perchlorate exposure, suggesting there was some adaptation to the hypothyroid condition. The mRNA level of D2 and RC3 in the brain was not affected by perchlorate-induced hypothyroidism in quail chicks after either 2 or 7.5 weeks of perchlorate exposure. As in the embryos, this suggests the brain of chicks was "protected" from the hypothyroid body conditions. / Ph. D.
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Two-Dimensional Modeling of AP/HTPB Utilizing a Vorticity Formulation and One-Dimensional Modeling of AP and ADNGross, Matthew L. 16 August 2007 (has links) (PDF)
This document details original numerical studies performed by the author pertaining to the propellant oxidizer, ammonium perchlorate (AP). Detailed kinetic mechanisms have been utilized to model the combustion of the monopropellants AP and ADN, and a two-dimensional diffusion flame model has been developed to examine the flame structure above an AP/HTPB composite propellant. This work was part of an ongoing effort to develop theoretically based, a priori combustion models. The improved numerical model for AP combustion utilizes a “universal” gas-phase kinetic mechanism previously applied to combustion models of HMX, RDX, GAP, GAP/RDX, GAP/HMX, NG, BTTN, TMETN, GAP/BTTN, and GAP/RDX/BTTN. The universal kinetic mechanism has been expanded to include chlorine reactions, thus allowing the numerical modeling of AP. This is seen as a further step in developing a gas-phase kinetic mechanism capable of modeling various practical propellants. The new universal kinetic mechanism consists of 106 species and 611 reactions. Numerical results using this new mechanism provide excellent agreement with AP's burning rate, temperature sensitivity, and final species data. An extensive literature review has been conducted to extract experimental data and qualitative theories concerning ADN combustion. Based on the literature review, the first numerical model has also been developed for ADN that links the condensed and gas phases. The ADN model accurately predicts burning rates, temperature and species profiles, and other combustion characteristics of ADN at pressures below 20 atm. Proposed future work and modifications to the present model are suggested to account for ADN's unstable combustion at pressures between 20 and 100 atm. A two-dimensional model has been developed to study diffusion in composite propellant flames utilizing a vorticity formulation of the transport equations. This formulation allows for a more stable, robust, accurate, and faster solution method compared to the Navier-Stokes formulations of the equations. The model uses a detailed gas-phase kinetic mechanism consisting of 37 species and 127 reactions. Numerical studies have been performed to examine particle size, pressure, and formulation effects on the flame structure above an AP/HTPB propellant. The modeled flame structure was found to be qualitatively similar to the BDP model. Results were consistent with experimental observations. Three different combustion zones, based on particle size and pressure, were predicted: the AP monopropellant limit, the diffusion flame, and a premixed limit. Mechanistic insights are given into AP's unique combustion properties.
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Modeling Solid Propellant Ignition EventsSmyth, Daniel A. 13 December 2011 (has links) (PDF)
This dissertation documents the building of computational propellant/ingredient models toward predicting AP/HTPB/Al cookoff events. Two computer codes were used to complete this work; a steady-state code and a transient ignition code Numerous levels of verification resulted in a robust set of codes to which several propellant/ingredient models were applied. To validate the final cookoff predictions, several levels of validation were completed, including the comparison of model predictions to experimental data for: AP steady-state combustion, fine-AP/HTPB steady-state combustion, AP laser ignition, fine-AP/HTPB laser ignition, AP/HTPB/Al ignition, and AP/HTPB/Al cookoff. A previous AP steady-state model was updated, and then a new AP steady-state model was developed, to predict steady-state combustion. Burning rate, temperature sensitivity, surface temperature, melt-layer thickness, surface species at low pressure and high initial temperature, final flame temperature, final species fractions, and laser-augmented burning rate were all predicted accurately by the new model. AP ignition predictions gave accurate times to ignition for the limited experimental data available. A previous fine-AP/HTPB steady-state model was improved to predict a melt layer consistent with observation and avoid numerical divergence in the ignition code. The current fine-AP/HTPB model predicts burning rate, surface temperature, final flame temperature, and final species fractions for several different propellant formulations with decent success. Results indicate that the modeled condensed-phase decomposition should be exothermic, instead of endothermic, as currently formulated. Changing the model in this way would allow for accurate predictions of temperature sensitivity, laser-augmented burning rate, and surface temperature trends. AP/HTPB ignition predictions bounded the data across a wide range of heat fluxes. The AP/HTPB/Al model was based upon the kinetics of the AP/HTPB model, with the inclusion of aluminum being inert in both the solid and gas phases. AP/HTPB/Al ignition predictions bound the data for all but one source. AP/HTPB/Al cookoff predictions were accurate when compared to the limited data, being slightly low (shorter time) in general. Comparisons of AP/HTPB/Al ignition and cookoff data showed that the experimental data might be igniting earlier than expected.
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ADDITIVE MANUFACTURING OF VISCOUS MATERIALS: DEVELOPMENT AND CHARACTERIZATION OF 3D PRINTED ENERGETIC STRUCTURESMonique McClain (9178199) 28 July 2020 (has links)
<p>The performance of solid rocket
motors (SRMs) is extremely dependent on propellant formulation, operating
pressure, and initial grain geometry. Traditionally, propellant grains are cast
into molds, but it is difficult to remove the grains without damage if the geometry
is too complex. Cracks or voids in propellant can lead to erratic burning that
can break the grain apart and/or potentially overpressurize the motor. Not only
is this dangerous, but the payload could be destroyed or lost. Some geometries
(i.e. internal voids or intricate structures) cannot be cast and there is no
consistent nor economical way to functionally grade grains made of multiple propellant
formulations at fines scales (~ mm) without the risk of delamination between
layers or the use of adhesives, which significantly lower performance. If one
could manufacture grains in such a way, then one would have more control and
flexibility over the design and performance of a SRM. However, new
manufacturing techniques are required to enable innovation of new propellant
grains and new analysis techniques are necessary to understand the driving
forces behind the combustion of non-traditionally manufactured propellant.</p>
<p>Additive manufacturing (AM) has
been used in many industries to enable rapid prototyping and the construction
of complex hierarchal structures. AM of propellant is an emerging research area,
but it is still in its infancy since there are some large challenges to
overcome. Namely, high performance propellant requires a minimum solids loading
in order to combust properly and this translates into mixtures with high
viscosities that are difficult to 3D print. In addition, it is important to be
able to manufacture realistic propellant formulations into grains that do not
deform and can be precisely functionally graded without the presence of defects
from the printing process. The research presented in this dissertation
identifies the effect of a specific AM process called Vibration Assisted
Printing (VAP) on the combustion of propellant, as well as the development of
binders that enable UV-curing to improve the final resolution of 3D printed structures.
In addition, the combustion dynamics of additively manufactured layered
propellant is studied with computational and experimental methods. The work
presented in this dissertation lays the foundation for progress in the
developing research area of additively manufactured energetic materials. </p>
<p>The appendices of this dissertation
presents some additional data that could also be useful for researchers. A more
detailed description of the methods necessary to support the VAP process,
additional viscosity measurements and micro-CT images of propellant, the
combustion of Al/PVDF filament in windowed propellant at pressure, and microexplosions
of propellant with an Al/Zr additive are all provided in this section. </p>
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