22 research outputs found
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Synthesis and Performance Characterization of a Nanocomposite Ternary Thermite: Al/Fe2O3/SiO2
Making solid energetic materials requires the physical mixing of solid fuels and oxidizers or the incorporation of fuel and oxidizing moieties into a single molecule. The former are referred to as composite energetic materials (i.e., thermites, propellants, pyrotechnics) and the latter are deemed monomolecular energetic materials (i.e., explosives). Mass diffusion between the fuel and oxidizer is the rate controlling step for composite reactions while bond breaking and chemical kinetics control monomolecular reactions. Although composites have higher energy densities than monomolecular species, they release that energy over a longer period of time because diffusion controlled reactions are considerably slower than chemistry controlled reactions. Conversely, monomolecular species exhibit greater power due to more rapid kinetics than physically mixed energetics. Reducing the diffusion distance between fuel and oxidizer species within an energetic composite would enhance the reaction rate. Recent advances in nanotechnology have spurred the development of nano-scale fuel and oxidizer particles that can be combined into a composite and effectively reduce diffusion distances to nano-scale dimensions or less. These nanocomposites have the potential to deliver the best of both worlds: high energy density of the physically mixed composite with the high power of the monomolecular species. Toward this end, researchers at Lawrence Livermore National Laboratory (LLNL) developed nano-particle synthesis techniques, based on sol-gel chemistry, for the production of thermite nanocomposites
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Formulation and Performance of Novel Energetic Nanocomposites and Gas Generators Prepared by Sol-Gel Methods
In the field of composite energetic materials, properties such as ingredient distribution, particle size, and morphology affect both sensitivity and performance. Since the reaction kinetics of composite energetic materials are typically controlled by the mass transport rates between reactants, one would anticipate new and potentially exceptional performance from energetic nanocomposites. We have developed a new method of making nanostructured energetic materials, specifically explosives, propellants, and pyrotechnics, using sol-gel chemistry. A novel sol-gel approach has proven successful in preparing nanostructured metal oxide materials. By introducing a fuel metal, such as aluminum, into the nanostructured metal oxide matrix, energetic materials based on thermite reactions can be fabricated. Two of the metal oxides are tungsten trioxide and iron(III) oxide, both of which are of interest in the field of energetic materials. Due to the versatility of the preparation method, binary oxidizing phases can also be prepared, thus enabling a potential means of controlling the energetic properties of the subsequent nanocomposites. Furthermore, organic additives can also be easily introduced into the nanocomposites for the production of nanostructured gas generators. The resulting nanoscale distribution of all the ingredients displays energetic properties not seen in its micro-scale counterparts due to the expected increase of mass transport rates between the reactants. The unique synthesis methodology, formulations, and performance of these materials will be presented. The degree of control over the burning rate of these nanocomposites afforded by the compositional variation of a binary oxidizing phase will also be discussed. These energetic nanocomposites have the potential for releasing controlled amounts of energy at a controlled rate. Due to the versatility of the synthesis method, a large number of compositions and physical properties can be achieved, resulting in energetic nanocomposites that can be fabricated to meet specific safety and environmental considerations
Structures of 1,1′,3,3′-Tetra(2-methyl-2-nonyl)ferrocenium(1+) Oxoanion(1−) Salts. Layered Materials with Alternating Ionic and Low-Dielectric Paraffin-Like Domains Through Which Anion Diffusion is Rapid
The unprecedented interdigitated and layered structures
of 1,1′,3,3′-tetraÂ(2-methyl-2-nonyl)Âferrocene
(DEC) and the oxoanion ferrocenium salts DEC<sup>+</sup>NO<sub>3</sub><sup>–</sup>, DEC<sup>+</sup>ClO<sub>4</sub><sup>–</sup>, and DEC<sup>+</sup>ReO<sub>4</sub><sup>–</sup> were determined
by single-crystal X-ray diffraction. The four structures are similar
except that the three DEC<sup>+</sup> salts have layers of XO<sub><i>n</i></sub><sup>–</sup> oxoanions stuffed between
the layers of interdigitated ferrocenium ions. The perpendicular distances
between layers of Fe atoms are 8.530, 9.108, 9.009, and 9.158 Ã…
for DEC, DEC<sup>+</sup>NO<sub>3</sub><sup>–</sup>, DEC<sup>+</sup>ClO<sub>4</sub><sup>–</sup>, and DEC<sup>+</sup>ReO<sub>4</sub><sup>–</sup>, respectively. The structures also contain
layers of rigorously coplanar Fe and X atoms that are tilted 65.4,
75.9, 61.9, and 61.1° from the aforementioned layers of Fe atoms
for DEC, DEC<sup>+</sup>NO<sub>3</sub><sup>–</sup>, DEC<sup>+</sup>ClO<sub>4</sub><sup>–</sup>, and DEC<sup>+</sup>ReO<sub>4</sub><sup>–</sup>, respectively. The local environments
of the XO<sub><i>n</i></sub><sup>–</sup> oxoanions
consist of networks of C–H···O hydrogen bonds,
and the structures exhibit channels through which these anions could
diffuse. Facile diffusion of these anions in thin films of DEC<sup>+</sup>XO<sub><i>n</i></sub><sup>–</sup>, with structures
that appear to resemble the crystal structures, has been demonstrated
Structures of 1,1′,3,3′-Tetra(2-methyl-2-nonyl)ferrocenium(1+) Oxoanion(1−) Salts. Layered Materials with Alternating Ionic and Low-Dielectric Paraffin-Like Domains Through Which Anion Diffusion is Rapid
The unprecedented interdigitated and layered structures
of 1,1′,3,3′-tetraÂ(2-methyl-2-nonyl)Âferrocene
(DEC) and the oxoanion ferrocenium salts DEC<sup>+</sup>NO<sub>3</sub><sup>–</sup>, DEC<sup>+</sup>ClO<sub>4</sub><sup>–</sup>, and DEC<sup>+</sup>ReO<sub>4</sub><sup>–</sup> were determined
by single-crystal X-ray diffraction. The four structures are similar
except that the three DEC<sup>+</sup> salts have layers of XO<sub><i>n</i></sub><sup>–</sup> oxoanions stuffed between
the layers of interdigitated ferrocenium ions. The perpendicular distances
between layers of Fe atoms are 8.530, 9.108, 9.009, and 9.158 Ã…
for DEC, DEC<sup>+</sup>NO<sub>3</sub><sup>–</sup>, DEC<sup>+</sup>ClO<sub>4</sub><sup>–</sup>, and DEC<sup>+</sup>ReO<sub>4</sub><sup>–</sup>, respectively. The structures also contain
layers of rigorously coplanar Fe and X atoms that are tilted 65.4,
75.9, 61.9, and 61.1° from the aforementioned layers of Fe atoms
for DEC, DEC<sup>+</sup>NO<sub>3</sub><sup>–</sup>, DEC<sup>+</sup>ClO<sub>4</sub><sup>–</sup>, and DEC<sup>+</sup>ReO<sub>4</sub><sup>–</sup>, respectively. The local environments
of the XO<sub><i>n</i></sub><sup>–</sup> oxoanions
consist of networks of C–H···O hydrogen bonds,
and the structures exhibit channels through which these anions could
diffuse. Facile diffusion of these anions in thin films of DEC<sup>+</sup>XO<sub><i>n</i></sub><sup>–</sup>, with structures
that appear to resemble the crystal structures, has been demonstrated
Structures of 1,1′,3,3′-Tetra(2-methyl-2-nonyl)ferrocenium(1+) Oxoanion(1−) Salts. Layered Materials with Alternating Ionic and Low-Dielectric Paraffin-Like Domains Through Which Anion Diffusion is Rapid
The unprecedented interdigitated and layered structures
of 1,1′,3,3′-tetraÂ(2-methyl-2-nonyl)Âferrocene
(DEC) and the oxoanion ferrocenium salts DEC<sup>+</sup>NO<sub>3</sub><sup>–</sup>, DEC<sup>+</sup>ClO<sub>4</sub><sup>–</sup>, and DEC<sup>+</sup>ReO<sub>4</sub><sup>–</sup> were determined
by single-crystal X-ray diffraction. The four structures are similar
except that the three DEC<sup>+</sup> salts have layers of XO<sub><i>n</i></sub><sup>–</sup> oxoanions stuffed between
the layers of interdigitated ferrocenium ions. The perpendicular distances
between layers of Fe atoms are 8.530, 9.108, 9.009, and 9.158 Ã…
for DEC, DEC<sup>+</sup>NO<sub>3</sub><sup>–</sup>, DEC<sup>+</sup>ClO<sub>4</sub><sup>–</sup>, and DEC<sup>+</sup>ReO<sub>4</sub><sup>–</sup>, respectively. The structures also contain
layers of rigorously coplanar Fe and X atoms that are tilted 65.4,
75.9, 61.9, and 61.1° from the aforementioned layers of Fe atoms
for DEC, DEC<sup>+</sup>NO<sub>3</sub><sup>–</sup>, DEC<sup>+</sup>ClO<sub>4</sub><sup>–</sup>, and DEC<sup>+</sup>ReO<sub>4</sub><sup>–</sup>, respectively. The local environments
of the XO<sub><i>n</i></sub><sup>–</sup> oxoanions
consist of networks of C–H···O hydrogen bonds,
and the structures exhibit channels through which these anions could
diffuse. Facile diffusion of these anions in thin films of DEC<sup>+</sup>XO<sub><i>n</i></sub><sup>–</sup>, with structures
that appear to resemble the crystal structures, has been demonstrated