The goal of a reactive material (RM) projectile is to produce appreciable chemical potential energy on demand while additionally providing structural integrity for the application. Recent advances in diagnostics and analysis techniques present opportunities to examine energy partitioning from a RM projectile upon high velocity impact, fragmentation, and reaction. This study analyzes partitioning chemical energy into gas and condensed phase energies as a function of the solid oxidizer concentration within the RM projectile and the oxygen concentration in the gas environment. Projectiles were made by consolidating aluminum (Al) with varied concentrations of molybdenum trioxide (MoO3) powders, and ballistic impact experiments were performed in air and inert argon environments. The RM projectiles were launched at 1050 m/s into two different chambers. Pressure measurements were made in a semi-sealed calorimetric chamber to quantify gas phase energy conversion and thermography measurements were made using a visual chamber to quantify condensed phase energy conversion. The results show increasing MoO3 concentration promotes ignition, fragmentation, and more rapid gas energy conversion in an air environment. The opposite was observed in argon, increasing MoO3 concentration promotes condensed phase energy conversion. Processes responsible for controlling energy partitioning are discussed.

Metal combustion is a process accompanied by strong light emission. Correspondingly, radiative loss can significantly affect the overall energy balance, and needs to be considered in the global numerical models describing metal dust combustion. In this work, we experimentally estimated the fraction of radiative loss during aluminum (Al) dust combustion by studying the heat release in a modified constant volume bomb calorimeter that enabled the additional measurement of pressure. The previously developed method of dispersing powder ensured nearly 100% combustion efficiency. The contribution of the combustion energy to heating the gas inside the calorimeter bomb was determined by analyzing the measured pressure traces and found to be measurably lower than 100%. The energy loss was attributed to radiant heat transfer from burning metal particles to the bomb wall. Aluminum powders with median size ranging from 4 μm to 100 μm were studied. The estimated fraction of radiative loss depended on the particle size. Radiative loss saturated at nearly 50% for larger particles and gradually reduced with the particle size decrease below 20 μm. We related the observed radiative loss to a recently introduced process that occurs during metal combustion, namely condense-luminescence. The results shown here have important implications for the role of radiant energy exchange in metal particle combustion and will transform future approaches to harnessing metal oxidation energy for a multitude of applications.

Off-the-shelf calorimeters are typically used for hydrocarbon-based fuels and not designed for simulating metal powder oxidation in gaseous environments. We have developed a method allowing a typical bomb calorimeter to accurately measure heat released during combustion and achieve nearly 100% of the reference heat of combustion from powder fuels such as aluminum. The modification uses a combustible organic dispersant to suspend the fuel particles and promote more complete combustion. The dispersant is a highly porous organic starch-based material (i.e. packing peanut) and allows the powder to burn as discrete particles thereby simulating dust-type combustion environments. The demonstrated closeness of measured Al heat of combustion to its reference value is evidence of complete metal combustion achieved in our experiment. Beyond calorific output under conditions simulating real reactive systems, we demonstrate that the calorimeter also allows characterization of the temporal heat release from the reacting material and this data can be extracted from the instrument. The rate of heat release is an important additional parameter characterizing the combustion process. The experimental approach described will impact future measurements of heat released during combustion from solid fuel powders and enable scientists to quantify the energetic performance of metal fuel more accurately as well as the transient thermal behavior from combusting metal powders.

Intermetallic (aluminum and zirconium) and thermite (aluminum and molybdenum trioxide) projectiles were launched using a high velocity impact ignition testing system. The experiments were designed to simulate reactivity in high (argon) and low (air) altitude environments. The projectiles were launched into a chamber that included a steel target plate for projectile penetration before impacting a rear witness plate. The chamber was semi-sealed and instrumented for quasi-static pressure data. The results provide an understanding of energy release from the projectile materials and of the environmental influence on performance. The transient pressure traces provide insight into reaction kinetics. A bifurcation in transient pressure rise was an indication of a shift in reaction kinetics from the inherent reactive material to metal oxidation with the environment. The bifurcation was delayed by about 0.15 ms for the intermetallic relative to the thermite, evidence that the thermite reaction proceeded faster upon impact than the intermetallic. The two-step process (impact ignition of the reactive material followed by metal oxidation) was shown to produce higher energy conversion efficiencies than projectiles composed of pure fuel (i.e., aluminum) reported previously. Both reactive materials showed energy conversion efficiencies greater than 30% (for air) and 50% (for argon), and an explanation of underestimated efficiency and energy losses is provided. These results have implications for advancing formulations for ballistic applications. Structural reactive materials can be used to modify the effective reactivity of metal-containing formulations in varied atmospheric environments.

Particle fragmentation influences thermochemical energy conversion processes in different ways and is of significance in energy generation technologies. Different reactive material formulations trigger varied thermal response in extreme environments such as high velocity impact. This study investigated optical thermal response of powder gun launched intermetallic (Al:Zr) and thermite (Al:MoO3) projectiles us-ing pyrometry and thermography. Projectiles were launched at 1250 m/s into an air-filled chamber and impacted a steel witness plate to create a dust explosion. The pyrometer was configured to measure temperatures directly at the point of impact, while the thermographic system measured temperatures throughout the explosion chamber. Results show that impact temperatures ranged between 3500 and 4000 K, but that the dynamics of energy conversion were different for the intermetallic and thermite projectiles. The intermetallic exhibited secondary reactions due to fragmented debris impacting the walls of the chamber. The thermite exhibited greater gas generation, propelling the debris field, and producing a more stochastic response with faster spreading and dissipation of thermal energy. Unique features such as microexplosions within fragmented particles were also analyzed. While both reactive materials pro-duce similar temperatures, their mechanisms of energy conversion and release are different, indicating the potential of these materials for different ballistic applications. (c) 2022 Elsevier Ltd. All rights reserved.

Surface modification is used to dramatically alter the thermal properties of a bulk metallic material. Thermal barrier coatings (TBCs) are typically applied using spray deposition or laser-based techniques to create a ceramic coating on a metal substrate. In this study, an effective TBC is created directly on a metallic substrate by inducing surface chemical reactions. Aluminum-zirconium (Al-Zr) substrates are used to induce surface-limited reactions that produce a 75-80% decrease in bulk thermal conductivity and diffusivity, respectively. The substrates are cylindrical disks 12.6 mm diameter and 2 mm thickness. Thermal properties are measured using laser flash analysis (LFA) at incrementally elevated temperatures. Focused ion beam (FIB) slicing of the substrate coupled with scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX) show that the substrate oxidized only along the outer 20 μm of the bulk surface. The layer thickness is significantly less than typical TBCs that can range from 50 to 300 μm yet the 20 μm coating still achieves a dramatic reduction in thermal transport properties. Additionally, thermal analysis reveals a sequence of exothermic reactions starting at 439 °C that include both intermetallic (i.e., ZrAl3) and oxidation (i.e., Al2O3 and ZrO) reactions suggesting continuous surface bonding at the coating-metal interface. The onset of exothermic activity coincides with the transition in thermal properties measured using LFA. These results show that surface oxidation reactions could be used to dramatically alter the thermal transport properties of a metal substrate.

A high-velocity impact-ignition testing system was used to study the dynamic response of brittle thermite projectiles impacting an inert steel target at velocities of 850 and 1200 m/s. The projectiles included consolidated aluminum and bismuth trioxide that were launched by a propellant driven gun into a catch chamber equipped with high-speed imaging diagnostics. The projectiles passed through a break-screen at the entrance to the chamber and either fragmented upon penetrating the break-screen or remained intact prior to impacting the steel target. In all cases, the projectiles pulverized upon impact, and a reacting debris cloud spreads through the catch chamber. At lower impact velocities, the fragmented and intact projectiles produced similar flame spreading rates of 217–255 m/s. At higher impact velocities, the intact projectile produced the slowest average flame spreading rate of 179 m/s because debris rebounding was limited by the length of the projectile and the resulting debris field was highly consolidated in the radial direction. In contrast, the fragmented projectile rebounded into a well dispersed debris cloud with the highest, 353 m/s, flame spreading rate. A kinetic energy flux threshold was proposed as a means for describing the shift in observed debris dispersion and flame spreading rates. A reactivity model was developed based on particle burn times using a computational fluid dynamics code that incorporated heat transfer and particle combustion in a multiphase environment to understand how the particle size influenced flame spreading. Results from the model show a trade-off between faster reactivity and increased drag inhibiting movement for smaller particle debris.

Significant improvements have been achieved in metal-mediated processes, often utilizing catalytic quantities of a transition metal. In pharmaceutical companies, processes ensuing from these advances are widely utilized for the synthesis of new drug candidates in medicinal chemistry as well as for the preparation of active pharmaceutical ingredients on small and up to commercial scale. This chapter provides a comprehensive overview of catalytic methodologies that are most frequently employed in the synthesis of complex organic molecules. It covers cross-coupling reactions catalyzed by palladium in most cases. Examples of Ni, Fe as well as Cu-catalyzed coupling reactions are discussed. In addition to cross-coupling reactions, other reactions that are discussed include allylic alkylation, selected C—H bond functionalization, hydrogene borrowing, as well as metathesis reactions. Finally, the chapter examines nonmetal-mediated catalytic reactions such as organocatalysis and phase transfer catalysis.

A direct and selective method for the α,β-dehydrogenation of esters using palladium catalysis in the presence of free OH and NH functionalities is reported herein. Allyl-palladium catalysis allows for preservation of readily oxidizable functionalities such as amines and alcohols. Furthermore, an economical protocol using LDA was developed for the dehydrogenation of β-amino esters.

Hexahydro-1,3,5-trinitroso-1,3,5-triazine (TNX) is mostly known as a by-product in the environmental decomposition of RDX. The original chemistry to TNX was never optimized and thus resulted in low yields due to competitive degradation of the starting material. Enabled conditions to TNX were developed by optimizing pH effects and mitigating foaming by reactor geometry and stirring. The conditions presented herein allow for the inexpensive and simple production of multi-gram quantities of TNX. The isolated TNX obtained by our new method was characterized by (HNMR)-H-1, (CNMR)-C-13, DSC, and X-ray crystallography. A preliminary evaluation of the sensitivity of TNX towards impact and friction is also presented.

The synthesis of multigram quantities of small molecule PCSK9 inhibitor (R,S)-3 is described. The route features a safe, multikilogram method to prepare 5-(4-iodo-1-methyl-1H-pyrazol-5-yl)-2H-tetrazole (10). A three-component dynamic kinetic resolution between tetrazole 10, acetaldehyde, and isobutyric anhydride was catalyzed by a chiral DMAP catalyst to afford enantiomerically enriched hemiaminal ester (S)-12 on multikilogram scale. Magnesiation, transmetalation, and Negishi coupling provided access to Boc-intermediate (R,S)-13, which was deprotected to provide (R,S)-3 in multigram quantities.

The synthesis of (2-cyclooctyn-1-yloxy)acetic acid was enabled to allow for the simple and safe production of this material on multigram scale.

A novel cocrystal (NEX-1) of CL-20 and MDNT is presented herein. The CL-20:MDNT cocrystal, obtained in high yield by resonant acoustic mixing, shows new properties versus the discrete components. This is the first example of cocrystallization of CL-20 where the new material is less sensitive to friction than CL-20 itself, while demonstrating similar impact and ESD sensitivity. The CL-20:MDNT cocrystal shows promise in the production of new energetic materials of interest by the cocrystallization of well-characterized components.

The long-time elusive structure of the acid copper(II) salt intermediate in the production of DBX-1 is presented. The single-crystal X-ray shows infinite chains of copper(II) ions complexed by six 5-nitrotetrazolate anions are aligned along the sixfold axis. Hydronium ions are located on the threefold axis with additional neutral water molecules.

Copper(I) 5-nitrotetrazolate (DBX-1) has emerged in recent years as a primary explosive that could serve as a replacement for lead azide (LA), a widely used explosive that has fallen out of favor due to its toxicity and chemical compatibility issues. While there is a significant amount of interest in this material, the development of DBX-1 has been hampered by the tedious and poorly understood chemical process for its preparation. To consistently produce DBX-1, two explosive intermediates must be isolated, and one of them requires purification. In this article, we present an improved process for the synthesis of DBX-1. In this process, neither of these intermediates needs to be handled by an operator, and the purification step is no longer necessary. It would be practical to perform the entire process under remote control, a necessity for energetic material manufacturing. We discuss the implications of our findings for the development of a robust process for the reproducible production of high-quality DBX-1.

A practical synthesis of SGLT2 inhibitor candidate ertugliflozin (1) has been developed for potential commercial application. The highly telescoped process involves only three intermediate isolations over a 12-step sequence. The dioxa-bicyclo[3.2.1]octane motif is prepared from commercially available 2,3,4,6-tetra-O-benzyl-d-glucose, with nucleophilic hydroxymethylation of a 5-ketogluconamide intermediate as a key step. The aglycone moiety is introduced via aryl anion addition to a methylpiperazine amide. High chemical purity of the API is assured through isolation of the crystalline penultimate intermediate, tetraacetate 39. A cocrystalline complex of the amorphous solid 1 with l-pyroglutamic acid has been prepared in order to improve the physical properties for manufacture and to ensure robust API quality.

We describe the development of an efficient and scalable process for the preparation of fluorocyclobutane-containing H-3 antagonist, 1. The synthesis was accomplished by the chemoselective addition of a magnesium ate complex and an amine to a 1,4-ketoester in a one-pot sequence, followed by a diastereoselective carbonyl-directed fluorination. The chemoselective addition of the magnesium ate complex to the ketoester benefited from tight stoichiometric control, short addition times, and lower reaction temperatures, and thus was amenable to rapid mixing and excellent heat transfer in a flow reactor.