Advancing Propulsion for Hypersonic and Space Rockets
#JetFuel
Advancing Propulsion for Hypersonic and Space Rockets
#JetFuel
Research Terms
Amorphous Materials Energetic Materials Metallic Materials Superconducting and Magnetic Materials Materials Characterization Materials Processing Surface Science Thin Films Nanotechnology Vacuum Technology Solid State Chemistry Crystallography Magnetic Technology Tribology Applied Physics Electron Microscopy
Industries
University of Central Florida researchers have developed a propellant made for firearm cartridges and other applications. The propellant can produce a predetermined pressure curve that rises more gradually to a maximum pressure and then maintains that pressure throughout the entire time that the bullet travels through the barrel. At the same time, it reduces felt recoil and wear and tear on the firearm. The propellant can be produced safely and inexpensively and transported with minimal risk. It accommodates a wide variety of handgun, rifle, and shotgun cartridges, as well as other applications that use a propellant.
Technical Details
The UCF invention is a propellant made from a flexible sheet, an ignitable material, and a firearm casing. In one example, the flexible sheet is nitrocellulose, and the ignitable material comprises thermite compositions. Thermite is on one side of the flexible sheet in a pattern of triangles. Each triangle’s base is adjacent to one edge of the sheet, and the corresponding apex is adjacent to the other side of the sheet. The flexible sheet is rolled around a nonburnable tube and placed within the firearm casing.
When the nonburnable tube is disposed over the primer pocket, ignition products from the primer travel through the tube, igniting the propellant. The size and shape of the triangles, as well as the amount of surface area covered by thermite, determine the variety of pressure curves that are producible for different firearm cartridges as well as for other applications.
Although the primary factor determining burn rate is the shape of the triangles and the amount of surface area covered by the thermite, other factors, such as layer thickness and total deposition thickness, can also contribute to a predetermined burn rate.
Researchers at the University of Central Florida and Columbia University have developed a novel thin film process for metal deposition (single crystal ruthenium, Ru) to achieve low resistivity in semiconductor interconnects. They observed 40 percent lower resistivity in bulk materials and expect to see a similar or greater advantage in nanowires. The invention provides for lower resistivity wires and nanowires. It can also support applications in electronic and optical devices that use an anisotropy of electrical conductivity. Ru thin films are important for next-generation semiconductor interconnects (nanowires) due to their low resistivity and high melting temperature.
Technical Details
The invention comprises a device and methods for creating ruthenium (Ru) thin films with a crystallographic surface net that promotes non-perpendicular c-axis orientations. While Ru films typically form with the c-axis perpendicular to the surface of a substrate or as a polycrystalline film with a random crystallographic orientation, the invention enables the configuration of net crystallographic surfaces that promote non-perpendicular c-axis orientations of Ru. The substrate may be formed with a metal-terminated surface in certain arrangements.
In one example, researchers achieved a low-resistivity crystal structure orientation by placing a few monolayers of high oxygen affinity metal (aluminum) on the insulating substrate before the deposition of the Ru. This induced the single crystal Ru film to grow with the c-axis parallel to the substrate plane. In certain embodiments, the c-axis can be arranged to be a) parallel to a film plane, or b) no more than about 10 degrees from parallel to a film plane.
Stage of Development
Prototype available.
Researchers at the University of Central Florida have a process for preparing composite thermite particles that enable thermite reactions to release more energy quicker for greater propulsion and more powerful explosions. The thermite composition can be used in propellant and explosive devices permitting significantly better control of the ignition and propagation phases of the thermite reaction.
Thermite is a type of pyrotechnic composition of a metal and a metal oxide, which produces a highly exothermic reaction, known as a thermite reaction, when ignited by heat. Unlike known techniques for forming thermite compositions, the inventors have created a process that enables the shearing of the thermite components without any significant initiation of the thermite reaction. Quickly conducting low temperature milling avoids atomic level mixing of the starting materials. As a result, the stored total energy of the resulting particles is increased as compared to conventionally milled thermite compositions, and the speed of energy release can be increased.
Technical Details
Developed in the early 1960s, the reagents for thermite reactions are both solid materials, metal and metal oxide, which do not readily permit mixing and require substantial preheating. This innovation presents a process for the preparation of composite thermite particles from a plurality of pressed composite particles that form a convoluted lamellar structure with alternating layers of metal and metal oxide. The procedure includes introducing metal oxides and complementary metals capable of reducing the metal oxide. The materials are then milled at a cryogenic temperature (i.e., below -50 C) to form a convoluted lamellar structure. The average layer thickness is generally between 10 nm and 1 micrometer and the molar proportions of the metal oxide and metal are generally within 30 percent of being stoichiometric for a thermite reaction.
While similar to organic reagents in the amount of energy released per unit weight, inorganic reagents are able to release up to 5 times more energy per unit volume, (energy density) thus requiring less space for the same amount of force released. Still, organic energetic materials have a faster reaction velocity, or burn rate, than inorganic materials. In order to increase the burn rate of the material the effective interface (area in which the two components are touching one another) must be improved upon.
To do so the invention utilizes a method for which the two components are stacked on top of one another in thin nanolayers, while avoiding any potential interfacial reacted zones of thickness. These zones are made of already reacted materials often caused by excess water vapor left inside the vacuum chamber during the manufacturing process, and will greatly decrease the effective interface between the two components. By substantially increasing the effective interface and virtually eliminating prematurely reacted zones, the invention was able to reach burn rates of up to 180 m/s utilizing inorganic reagents.
Advantages
This technology from the University of Central Florida reduces the presence of water vapor by nearly a hundred times, which allows for much thinner interfacial regions between the nanolayers, a higher stored energy density, and a reaction velocity that is five times faster than conventional designs. In addition, the controlled application of intense amounts of heat through regulated rapid heat release improves welding, soldering, and brazing, without damaging the peripheral materials.
Technical Details
To create these energetic materials and thin film explosives, layered MIC deposition is accomplished through the contact of two different solid reactants, such as copper oxide and aluminum, which releases heat, resulting in a self-propagating reaction. This is done by sputtering in a vacuum chamber at a low pressure, helping in the reduction of water vapor content. Additionally, pure chemical inert gas is used for sputtering to provide higher purity and prevent water vapor contamination. Moreover, the thickness of the interfacial region over the entire surface area of reactants is less than 2 nanometers, providing higher reaction velocity.
