<p>Development of complex aerospace systems often takes decades of research and testing. High  performing propellants are important to the success of rocket propulsion systems. Development  and testing of new propellants can be expensive and dangerous. Full scale tests are often required  to understand the performance of new propellants. Many industries have started using data science  tools to learn from previous work and conduct smarter tests. Material scientists have started using  these tools to speed up the development of new materials. These data science tools can be used to  speed up the development and design better propellants. I approach the development of new solid  propellants through two steps: Prediction of delivered performance from available literature tests,  prediction of ideal performance using physics-based models. Random Forest models are used to  correlate the ideal performance to delivered performance of a propellant based on the composition  and motor properties. I use Parsimonious Neural Networks (PNNs) to learn interpretable models  for the ideal performance of propellants. I find that the available open literature data is too biased  for the models to learn from and discover families of interpretable models to predict the ideal  performance of propellants. </p>

<p>The ignition of energetic materials, and specifically solid propellants, is a complex process</p> <p>that must be safe, consistent, and precisely controlled. There is a wide range of applications with</p> <p>specific ignition requirements for solid propellants including inflation of airbags, propulsion</p> <p>systems (including rockets), as well as arm and fire devices. Currently, electrical or percussion</p> <p>pyrotechnic igniters are most the commonly used ignition systems. These systems must be</p> <p>carefully designed to deliver the proper amount of energy to a specified surface area of the</p> <p>propellant. A photon light source (i.e. flash or laser-based, ranging from UV to IR wavelengths)</p> <p>can potentially be used to ignite energetic materials with lower input energy and more precise</p> <p>spatial and temporal control, thereby improving safety and reliability by eliminating electrical</p> <p>systems used in pyrotechnic igniters. In addition, they could be potentially safer from stray</p> <p>electrical charges causing unintentional ignition.</p> <p>The purpose of this work is to further explore the potential of optical ignition for energetic</p> <p>systems and identify ideal materials that can be used for optical ignition. In order to identify</p> <p>optically sensitive materials, we will study ignition energies, ignition delays, flame temperatures,</p> <p>and other combustion characteristics for possible energetic materials. This research addresses a</p> <p>gap in understanding of optical ignition for energetic materials, as finding and integrating materials</p> <p>that are optically sensitive while still being practical can be extremely challenging. These</p> <p>challenges include: (1) a lack of absorptivity to optical wavelengths in the UV to low-IR range,</p> <p>and subsequently, a very high sensitivity to input energy at the absorptive wavelengths that makes</p> <p>sustained ignition difficult, (2) a need for full density materials in practical energetic systems,</p> <p>while optically sensitive materials are exceedingly difficult to ignite as packing density increases</p> <p>due to heat transfer, and (3) the lack of research regarding novel fuels/oxidizers for the specific</p> <p>purpose of optical ignition.</p> <p>Metal/fluoropolymer energetic materials have been of interest to the energetic materials</p> <p>community for many years. Due to fluorine’s excellent oxidizing ability, they can be used in</p> <p>composite materials with metal fuels to produce energetic materials for a wide variety of</p> <p>applications. Polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), polycarbon</p> <p>13</p> <p>monofluoride (PMF), and terpolymers such as tetrafluoroethylene, hexafluoropropylene, and</p> <p>vinylidene fluoride (THV) have already seen extensive use in applications ranging including</p> <p>protective coatings, strain gauges, and electronics. However, when combined with metals such as</p> <p>lithium, magnesium, aluminum, or titanium, they also present an opportunity for a wide variety of</p> <p>energetic materials. For this study, metal/fluoropolymer composites present a novel opportunity</p> <p>for exploring optical ignition of widely absorptive, full-density energetic materials. This work will</p> <p>characterize the combustion and sensitivity of metal/fluoropolymer composites to provide novel</p> <p>materials for optical ignition of energetics.</p> <p>Specifically, this work will begin with finding a suitable energetic composite that is optically</p> <p>sensitive. Once this material has been identified, research will be done to thoroughly characterize</p> <p>the optically sensitive composite by looking at additive manufacturability, flame temperatures, and</p> <p>ignition sensitivities from various methods and formulations. Once the material has been</p> <p>thoroughly characterized, it will be implemented into solid propellants to test the feasibility of the</p> <p>material in practical energetic systems. Finally, the lessons learned from this work will be applied</p> <p>to novel formulations to identify new optically sensitive energetic composites.</p>

<p dir="ltr">Tailorable energetics are energetic materials that can be modified to alter their performance and sensitivity. Examples of tailoring energetic materials include additive manufacturing, manufactured hot spots, switchable energetics, and cocrystallization. Developing novel energetic material is a difficult and cost intensive process, because of this, tailoring the performance and sensitivity of existing energetic materials is critical for continued improvement. Additive manufacturing has provided new methods for generating complex geometries of composite materials. Additive manufacturing of composite materials through direct-ink-write (DIW) experiences extrusion limitations due to the high viscosities of highly solids loaded mixtures; the limitations being more severe with smaller syringe tip diameter. A novel printing technique called vibration-assisted printing (VAP) was developed as a method to extend the extrudability limits and extrusion speeds observed with direct-ink-write systems. Printability envelopes were shown in previous work to extend extrudability of monomodal glass bead composites in VAP systems over conventional DIW systems. This study compares the mass flowrates and extrudability limits for bimodal mixtures of glass beads suspended in a hydroxyl-terminated polybutadiene (HTPB) binder for both VAP and DIW printing as a function of volume percent solids loading. The bimodal glass bead mixtures showed a linear response in extrusion rate versus solids loading for both VAP and DIW systems. The VAP system was able to print higher volume loadings than the direct-ink-write system. In addition to extending the extrudability limits, the mass flowrate for the VAP system was significantly higher at all volume loadings tested compared to the DIW. Interestingly, bimodal mixtures were shown to extrude quicker than the monomodal mixtures at all volume loadings and across both printing systems.</p><p><br></p><p dir="ltr">Inhomogeneities within explosives affect the sensitivity and detonation wave shape of energetic materials. The influence of voids on explosive initiation has been well documented; however, the effects that voids between 0.1 mm and 10 mm have on a propagating detonation wave remains largely unexplored. The effect of single cylindrical voids on detonation wave shape and re-initiation was examined here using manufactured voids in a rubberized 1,3,5-trinitro-1,3,5-triazinane (RDX) explosive. Two streak imaging techniques were fielded to investigate void influence. For the first, back-surface streak imaging, the location of the void on the samples was changed and the resulting change in detonation wave shape at the downstream breakout was captured using a streak camera in cut-back experiments. The results from this experiment showed the effects of an initial jet form for short cut-back distances and as shock propagation progressed, the jet formation was absorbed by the unaffected portions of the wave front. The second method, top-surface streak imaging, was used to investigate the re-initiation/downstream propagation of the detonation front and the detonation velocity of the rubberized explosive. These experiments were compared to similar experimental results from machined voids in PBX 9501, a 1,3,5,7-tetranitro-1,3,5,7-tetrazocane (HMX)-based explosive, to investigate the interaction of a detonation wave with a 0.5 mm void for different explosives. The experiments were also compared to simulations using a multi-dimensional and multi-material hydrodynamic code (CTH). These results showed the influence that small features can have on detonation wave shaping and how explosive properties play a key role in that interaction. In addition to air-filled voids, this study examined the effects of 0.5 mm diameter voids filled with different inert metals on the detonation wave shape for an RDX-based rubberized explosive. The metals selected for experiments were 1066 aluminum, brass, copper, and tungsten. Experimental results showed that the extent of detonation wave shaping was closely tied to the density differential between the bulk explosive and metal insert. Simulations were performed using CTH to further analyze material inclusions. Forty-four different filler materials were simulated to isolate the driving factors for wave shaping of the detonation front. The main factors of interest were bulk sound speed, shock impedance, and filler material density. Understanding the influence of material inclusions on detonation performance and wave shape allows for tailoring of detonations as well as characterizing how unintentional defects will alter the explosive.</p><p><br></p><p dir="ltr">Improving the safety of explosive materials through the synthesis of insensitive explosives has been studied extensively. However, little work has focused on creating switchable explosives. A switchable explosive is normally insensitive to detonation, and therefore safe to handle and transport, but can be sensitized when needed to create a functional explosive. Similarly, it may be desired to desensitize an explosive to prevent its function. This study examined the ability to create a switchable RDX-based rubberized explosive using thermally-expandable microspheres (TEMs). The addition of TEMs to the explosive formulation allowed for microstructural changes and potential hot spot locations such as voids to form as the microspheres expanded. Small voids (less than about 10 µm) are more likely to be critical hot spots when shocked, and likewise larger voids are less likely to ignite successfully (sub-critical) when shocked. Consequently, both sensitization and desensitization are possible. The rubberized explosive considered here with unexpanded microspheres was unable to sustain a detonation for the size used, but after specific heating followed by cooling to produce small voids, a detonation was achieved. That is, the TEMs addition to the RDX-based rubberized explosive resulted in an explosive that is detonation insensitive when unheated but becomes a functional explosive after it is sensitized through heating. This paves the way to create insensitive explosive formulations with on-demand switchable detonation function through the incorporation of thermally-expandable microspheres. Desensitization was also demonstrated with specific heating of TEMs in an initially detonable explosive charge. And finally, we also demonstrated that deflagration can be affected by heating TEMs.</p><p><br></p><p dir="ltr">Energetic cocrystallization is a technique that produces a cocrystal that is formed using two known explosives to potentially gain the benefits of one or both without the drawbacks for a particular application. A comparison of cocrystals to a physical mixture of the same coformers can be considered. Cocrystals have unique material properties and crystal structure, whereas a physical mixture is just a mixed combination of the known materials at the same molar ratio. This study used photon Doppler velocimetry (PDV) to compare the particle velocity for 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane (CL-20) and 1-methyl-3,5-dinitro-1,2,4-triazole (MDNT) at a 1:1 molar ratio for both a cocrystal and a physical mixture of the two energetic materials. This cocrystal was previously shown to detonate faster than a physical mixture. However, the PDV results here were not consistent with this result. In addition to measuring output particle velocity with PDV, the cocrystal was characterized to examine phase purity and possible signs of deterioration of the material over time. Evaluating the cocrystal with Fourier-transform infrared spectroscopy (FT-IR), bomb calorimetry, and powder X-ray diffraction (PXRD) allowed for more accurate comparison and greater confidence in the particle velocity measurements obtained in these experiments. The most significant difference in the material characterization results was the difference in enthalpy of formation, as the material tested in this study had a substantially lower enthalpy of formation than previously measured for a CL-20/MDNT cocrystal.</p>

<p> Inclement challenges of a changing climate and humanity's desire to explore extraterrestrial environments both necessitate efficient methods to obtain freshwater. To accommodate next generation water technology, there is a need for understanding and defining the energy efficiency for unconventional water sources over a broad range of environments. Exergy analysis provides a common description for efficiency that may be used to evaluate technologies and water sources for energy feasibility. This work uses robust thermodynamic theory coupled with atmospheric and planetary data to define water capture efficiency, explore its variation across climate conditions, and identify technological niches and development needs.  </p> <p><br></p> <p> We find that desalinating saline liquid brines, even when highly saline, could be the most energetically favorable option for obtaining water outside of Earth. The energy required to access water vapor may be four to ten times higher than accessing ice deposits, however it offers the capacity for decentralized systems. Considering atmospheric water vapor harvesting on Earth, we find that the thermodynamic minimum is anywhere from 0x (RH≥ 100%) to upwards of 250x (RH<10\%) the minimum energy requirement of seawater desalination. Sorbents, modelled as metal organic frameworks (MOFs), have a particular niche in arid and semi-arid regions (20-30%). Membrane-systems are best at low relative humidity and the region of applicability is strongly affected by the vacuum pumping efficiency. Dew harvesting is best at higher humidity and fog harvesting is optimal when super-saturated conditions exist. Component (e.g., pump, chiller, etc.) inefficiencies are the largest barrier in increasing process-level efficiency and strongly impact the regions optimal technology deployment. The analysis elucidates a fundamental basis for comparing water systems energy efficiency for outer space applications and provides the first thermodynamics-based comparison of classes of atmospheric water harvesting technologies on Earth.</p>

<p dir="ltr">Phosphor thermography is an effective technique for making spatially resolved temperature measurements on surfaces, however little consideration has been given to incorporating the phosphors inside crystalline materials to make internal measurements. Doing so would grant optical access to the phosphors through the crystal. In this work, we prepared a thermographic energetic composite via fast crash encapsulation of BaMgAl₁₀O₁₇:Eu (BAM) in ammonium perchlorate (AP) crystals, which enabled the use of phosphor thermography to spatially resolve the temperature of the energetic composite. We demonstrate that the temperature measurements show good agreement with thermocouple measurements. The ability to calibrate the material was also demonstrated and compared to the response in dynamic thermal environments. Usability limits as well as thermal stability issues of the composite were also investigated and discussed. The successful encapsulation of BAM within AP and demonstration of thermographic behavior in the composite, indicate the viability of using encapsulation as a method to produce thermographic energetic composites.</p>

<p dir="ltr">Nanoparticles have seen immense development in the past several decades due to their intriguing physicochemical properties. The modern chemist is interested not only in methods of synthesizing nanoparticles with tunable properties but also in the chemistry that nanoparticles can drive. While several methods exist to synthesize nanoparticles, it is often advantageous to put nanoparticles on a variety of conductive substrates for multiple applications (such as energy storage and conversion). Despite enjoying over 200 years of development, the electrodeposition of nanoparticles suffers from a lack of control over nanoparticle size and morphology. Understanding that structure-function studies are imperative to understand the chemistry of nanoparticles, new methods are necessary to electrodeposit a variety of nanoparticles with control over macro-morphology but also microstructure. When a nanodroplet full of a metal salt precursor is incident on the electrode biased sufficiently negative to drive electroplating, nanoparticles form at a shocking rate (on the order of microseconds to milliseconds). We start with the general nuts-and-bolts of the experiment (nanodroplet formation and methods for electrodeposition). The deposition of new nanomaterials often requires one to develop new methods of measurement, and we detail new measurement tools for quantifying nanoparticle porosity and nanopore tortuosity within single nanodroplets. Owing to the small size of the nanodroplets and fast mass transfer, the use of nanodroplets also allows the electrodeposition of high entropy alloy nanoparticles at room temperature. Electrodeposition in aqueous nanodroplets can also be combined with stochastic electrochemistry for a variety of interesting studies. We detail the quantification of the growth kinetics of single nanoparticles in single aqueous nanodroplets. Nanodroplets can also be used as tiny reactors to trap only a few molecules, and the reactivity of those molecules can be electrochemically probed and evaluated with time. Overall, this burgeoning synthetic tool is providing unexpected avenues of tunability of metal nanoparticles on conductive substrates. Moreover, there is little understanding of how ion transfer can affect the fundamental of nanoparticle synthesis with nanodroplet-mediated electrodeposition. This thesis details different experiments performed to study the role of ion transfer during the nucleation and growth of nanoparticles.</p>

Despite the central importance of porous electrodes to any advanced electrochemical system, there is no clear answer to “<i>How to make the best electrode</i>?”. The source of ambiguity lies in the incomplete understanding of convoluted material interactions at smaller – difficult to observe length and timescales. Such mesoscopic interactions, however, abide by the fundamental physical principles such as mass conservation. The porous electrodes are investigated in such a physics-based setting to comprehend the interplay among structural arrangement and off-equilibrium processes. As a result, a synergistic approach exploiting the complementary characteristics of controlled experiments and theoretical analysis emerges to allow mechanistic insights into the associated mesoscopic phenomena. The potential of this philosophy is presented by investigating three distinct electrochemical systems with their unique peculiarities.

Conselho Nacional de Desenvolvimento Científico e Tecnológico / Organic and inorganic materials have been used as adsorbent materials of aquatic pollutants due to their both good adsorption capacities and physical and chemical stabilities. In this work, the ligand 3-aminopropytrimethoxysilane was immobilized on silica gel surface, with consecutive reactions with glutaraldehyde and chitosan. All materials were characterized by TG/DTG, DSC, FTIR, DRX and MEV, where the presence of the silica-immobilized chitosan was evidenced. The adsorption kinetics of the anionic dye remazol blue (AR) on the cross linked silica/chitosan (Sil-Quit-R) was studied in the temperature range of 25 - 55 ºC and initial dye concentration of 23 - 800 mg L-1. The results were best fitted to both the pseudo second-order Ho and McKay and the Avrami models. The AR dye adsorption at chemical equilibrium were best described using the three-parameter Redlich-Peterson I, Sips, Tóth, Baudu I and five-parameter Fritz-Schlunder IV models. From these results, the heterogeneity of the Sil-Quit-R adsorption sites was evidenced. The adsorption enthalpies (ΔadsH) were all endothermic and increased with the increasing of adsorption temperature. The negative values for ΔadsG have indicated that the adsorption processes are spontaneous. The adsorption entropies (ΔadsS) were all positive and increased with the increasing of adsorption temperature. From the thermodynamic viewpoint, the positive ΔadsS values were the adsorption driving force. The adsorption capacity of Sil-Quit-R was good, mainly related to the adsorption results at low dye concentrations in solution. / Matrizes orgânicas e inorgânicas têm sido utilizadas como materiais para remoção de poluentes aquáticos, dada às suas boas capacidades de adsorção e estabilidades físicas e químicas. Neste trabalho, foi sintetizado e caracterizado o material híbrido orgânico/inorgânico Sílica/Quitosana Reticulado (Sil-Quit-R) através da formação de ligações cruzadas, sendo caracterizados por TG/DTG, DSC, FTIR, DRX e MEV e avaliada as suas interações com o corante Azul de Remazol (AR). Na avaliação da cinética de interação do corante (AR) na (Sil-Quit-R), foi feita entre 25 e 55ºC, nas concentrações do corante entre 23 a 800 mg.L-1. Os modelos de Difusão Intrapartícula e de Avrami mostraram os melhores ajustes. Evidenciaram-se também várias etapas cinéticas de difusão em relação ao tempo de contato. As adsorções nos equilíbrios químicos foram mais bem descritas pelos modelos de três parâmetros ajustáveis de Redlich-Peterson I, Sips, Tóth, Baudu I e para o modelo de cinco parâmetros ajustáveis de Fritz-Schlunder IV. Esses resultados evidenciaram a heterogeneidade dos sítios de adsorção da Sil-Quit-R. Os valores das entalpias de adsorção (ΔadsH) foram maiores que zero indicando processos endotérmicos e aumentaram com o aumento da temperatura de adsorção. Os valores negativos de ΔadsG indicaram a espontaneidade dos processos de adsorção. As entropias das adsorções (ΔadsS) foram positivas e aumentaram com o aumento da temperatura de adsorção, sendo, termodinamicamente, a força motriz dos processos de adsorção. As capacidades de adsorção máximas do material podem ser consideradas bem evidenciadas com um qemax em todas as concentrações e temperaturas, principalmente quando o corante Azul de Remazol estava presente em baixas concentrações em solução.

<div>The work discussed in this document seeks to integrate conductive additives with energetic material systems to offer an alternative source of ignition for the energetic material. By utilizing the conductive properties of the additives, ohmic heating may serve as a method for preheating and igniting an energetic material. This would allow for controlled ignition of the energetic material without the use of a traditional ignition source, and could also result in easier system fabrication.</div><div>For ohmic heating to be a viable method of preheating or igniting these conductive energetic materials, there cannot be significant impact on the energetic properties of the energetic materials. Various mass solids loadings of graphene nanoplatelets (GNPs) were mixed with a reactive mixture of aluminum (Al)/polyvinylidene fluoride (PVDF) to test if ohmic heating ignition was feasible and to inspect the impact that these loadings had on the energetic properties of the Al/PVDF. Results showed that while ohmic heating was a plausible method for igniting the conductive energetic samples, the addition of GNPs degraded the energetic properties of the Al/PVDF. The severity of this degradation was minimized at lower solids loadings of GNPs, but this consequently resulted in larger voltage input requirements to ignite the conductive energetic material. This was attributable to the decreased conductivities of the samples at lower solids loading of GNPs.</div><div>In hopes of conserving the energetic properties of the Al/PVDF while integrating the conductive additives, additive manufacturing techniques, more specifically fused filament fabrication, was used to print two distinct materials, Al/PVDF and a conductive composite, into singular parts. A CraftBot 3 was used to selectively deposit Conductive Graphene PLA (Black Magic) filament with a reactive filament comprised of a PVDF binder with 20% mass solids loadings of aluminum. Various amounts of voltage were applied to these conductive energetic samples to quantify the time to ignition of the Al/PVDF as the applied voltage increased. A negative correlation was discovered between the applied voltage and time to ignition. This result was imperative for demonstrating that the reaction rate could be influenced with the application of higher applied voltages.</div><div>Fused filament fabrication was also used to demonstrate the scalability of the dual printed conductive energetic materials. A flexural test specimen made of the Al/PVDF was printed with an embedded strain gauge made of the Black Magic filament. This printed strain gauge was tested for dual purposes: as an igniter and as a strain sensor, demonstrating the multi-functional use of integrating conductive additives with energetic materials.</div><div>In all, the experiments in this document lay a foundation for utilizing conductive additives with energetic materials to offer an alternative form of ignition. Going forward, ohmic heating ignition may serve as a replacement to current, outdated methods of ignition for heat sensitive energetic materials.</div>

In the ternary system CsCl – NaCl – H2O, at a temperature of 298.15 K, a double salt with the stoichiometric formula CsCl∙2NaCl∙2H2O(cr) is known to be formed. This double salt and the anhydrous CsCl(cr) are the end-members of a solid solution. For the pure double salt, the solubility constant was determined. The obtained value was applied to calculate the solubility diagram also of the quaternary system CsCl – NaCl – KCl – H2O and the quaternary-reciprocal system Cs+, Na+ || Cl−, SO42− – H2O. The solubility constant together with a solid solution between CsCl·2NaCl·2H2O(cr) and CsCl(cr) were implemented in THEREDA, which extends the applicability of the existing cesium dataset.