Geneva R. Peterson

Ionic Polymers as a New Structural Motif for High-Energy-Density Materials

Energetic materials have been used for nearly two centuries in military affairs and to cut labor costs and expedite laborious processes in mining, tunneling, construction, demolition, and agriculture, making a tremendous contribution to the world economy. Yet there has been little advancement in the development of altogether new energetic motifs despite long-standing research efforts to develop superior materials. We report the discovery of new energetic compounds of exceptionally high energy content and novel polymeric structure which avoid the use of lead and mercury salts common in conventional primary explosives. Laboratory tests indicate the remarkable performance of these Ni- and Co-based energetic materials, while DFT calculations indicate that these are possibly the most powerful metal-based energetic materials known to date, with heats of detonation comparable with those of the most powerful organic-based high explosives currently in use.

Metal-Organic Frameworks (MOFs) as Safer, Structurally Reinforced Energetics

Second-generation cobalt and zinc coordination architectures were obtained through efforts to stabilize extremely sensitive and energetic transition-metal hydrazine perchlorate ionic polymers. Partial ligand substitution by the tridentate hydrazinecarboxylate anion afforded polymeric 2D-sheet structures never before observed for energetic materials. Carefully balanced reaction conditions allowed the retention of the noncoordinating perchlorate anion in the presence of a strongly chelating hydrazinecarboxylate ligand. High-quality X-ray single-crystal structure determination revealed that the metal coordination preferences lead to different structural motifs and energetic properties, despite the nearly isoformulaic nature of the two compounds. Energetic tests indicate highly decreased sensitivity and DFT calculations suggest a high explosive performance for these remarkable structures.

Solvent-tuned hierarchical porosity in nitrocellulose aerogels

We describe the simple preparation of nitrocellulose gels and high surface area (300 + m(2) g(-1)) aerogels and their hierarchical pore structures. The solvent in which the gels form greatly influences the pore geometry and size distribution of the gels in both the macro- and mesopore domains.

Rapid preparation of high surface area iron oxide and alumina nanoclusters through a soft templating approach of sol–gel precursors

A facile, one-pot and organic-solvent free strategy for the synthesis of Fe2O3/Fe3O4 and Al2O3 nanoparticles has been explored. Our synthesis combines the simple preparation of small particles from an epoxide assisted, sol–gel method with the rapid through-put of soft-template processing to yield highly porous metal oxides. The role of the supporting dextran template is investigated and is found to be crucial in tuning surface area and morphological shape. In all, we show this process to be a simple, low-cost approach that could be amended to other metal systems. The resulting porous Fe and Al materials was investigated using gas adsorption/desorption analysis, scanning electron microscopy and transmission electron microscopy. The annealed materials were analyzed using powder X-ray diffraction.

Thermal tuning of advanced Cu sol–gels for mixed oxidation state Cu/CuxOy materials

In this report, we describe new conditions for the formation of copper gels and aerogels via epoxide addition to CuBr2 in dimethylformamide (DMF). These CuBr2-derived sols undergo a rapid gel transition and result in materials that have enhanced mechanical properties when compared with the gels derived from CuCl2. Additionally, upon air-annealing, they convert to nanoscopic CuO at temperatures much lower than the CuCl2 analogues. Moreover, annealing under nitrogen results in copper species with reduced oxidization states including Cu2O and metallic Cu. The ratio of copper oxidation states can be controlled by simple modification of the thermal program used to anneal the materials. The thermal reduction of the copper is attributed to retained DMF ligands in the as-prepared aerogels which was confirmed by FTIR spectroscopy. These aerogel materials were characterized by powder X-ray diffraction (PXRD), physisorption, thermogravimetric analysis (TGA), and temperature programmed reduction (TPR).

Development of a carbon-supported Sn–SnO2 photocatalyst by a new hybridized sol–gel/dextran approach

Carbon-supported Sn–SnO2 photocatalysts have been prepared for the first time using the newly designed dextran-mediated, epoxide-assisted sol–gel method. By coupling dextran with the epoxide assisted sol–gel technique we have established an easily modulated one-pot synthesis that demonstrates tunable carbon content with concerted production of a biphasic system. In effect, this method targets efficient development of photocatalysts that are metal-incorporated and catalyst-supported, very few methods such as this exist in the literature. This method eliminates traditional treatment steps required to create porous xerogels thereby eliminating days of processing. The formation of nanostructured sol–gels by epoxide-driven polycondensation was achieved using propylene oxide or glycidol, and the effects of the epoxide and dextran were explored in the formation of SnO2 and Sn–SnO2 carbon composite nanomaterial. The photocatalytic activity of selected SnO2 and Sn–SnO2 carbon composites were tested for the degradation of Rhodamine B (RhB). The biphasic systems show higher photocatalytic activity than the pure SnO2 systems, a result of both increased heterojunction sites between metallic tin and tin oxide that lower recombination rates, in addition to the incorporation of a carbon network that displays increased dye adsorption. The original methods developed here should be further explored to access improved catalytic material.

Controllable thermal degradation of 2,4,6-trinitrotoluene (TNT) by absorption and confinement into mixed metal sponges

In this work, we report the absorption and confinement of 2,4,6-trinitrotoluene (TNT) in porous metals (Ag, Ag/Al, and Ag/Cu), and the effect of the physical properties of the metal on the calorimetric properties of TNT using thermogravimetric analysis and differential scanning calorimetry. The surface area and pore size distribution of the confiners were calculated to determine their effect on both the onset temperature and the rate at which TNT volatilizes. Confinement of TNT into the mixed metal sponges was confirmed by scanning electron microscopy. Overall, this study provides an insight into the fundamental factors influencing the properties of energetic materials under confinement that could potentially allow for more controlled and reliable degradation techniques depending on the characteristics of the porous material.