This Small Business Innovation Research (SBIR) Phase I Project is focused on research to develop reinforced silicon carbide hollow spheres. This effort will apply a modified version of its proprietary hollow sphere production process in combination with novel materials. Novel characteristics resulting from the hollow sphere structure to be realized include: low cost bulk production of individual loose hollow spheres, uniform shape, uniform dimensions, dimensional stability, and low apparent density. Additionally, the hollow spheres will possess the important structural and thermal characteristics of silicon carbide including extreme hardness, high thermal conductivity, low thermal expansion coefficient, thermal shock resistance, high abrasion resistance, high melting point, and high resistance to oxidation or corrosion caused by other materials. These hollow spheres will ultimately be used to form continuous complex net shapes.
The broader impact/commercial potential of this project will be the availability of lightweight, high-strength, high-temperature material structures not previously possible. Hollow silicon carbide spheres have commercial potential for high-performance applications, especially for net shape superstructures in supersonic and hypersonic aircraft, spacecraft, and missiles. These materials find specific applications in high-temperature environments, such as the exterior surfaces of space reentry vehicles, inside combustion chambers, and as nozzles in jet engines, rocket engines, and power generators. Hollow silicon carbide spheres have applications that include thermal insulation, impact absorption (armor), catalyst support, metal and gas filtration, automotive heat engines, and mechanical seals. The knowledge generated about silicon carbide during this project can also be transferred to other related materials such as boron carbide.
Deep Springs Technology (DST) of Toledo, Ohio has produced exceptionally strong, light-weight, hermetically sealed hollow silicon carbide spheres by its proprietary process. These spheres can be produced in a variety of different sphere diameters and wall thicknesses demonstrating this technologies propensity for customization; providing material properties needed for applications operating in extreme environments and markets. These hollow spheres have remained intact and undamaged after isotropic pressure loading in excess of 60,000 psi. Pressureless liquid phase sintering has also proven a viable method of shell wall densification, which was not previously thought possible for the formation of a dense wall hollow member. In addition to the excellent strength of DST’s hollow silicon carbide spheres they can be very lightweight. Low density, strong, hermetically sealed hollow silicon carbide spheres are of great interest to the buoyancy market for application in syntactic foam systems for the most demanding hadal zone (sub 6,000 meter) exploratory vehicles. Pressures at those depths can exist in excess of 16,000 psi. The silicon carbide shells can have a true sphere density as low as 0.3 g/cc providing an ideal filler for syntactic systems designed for deep water applications. Silicon carbide has excellent thermal resistance and is used in many high temperature applications. DST’s silicon carbide hollow shells can be used as an advanced thermal barrier by combing the natural thermal properties of silicon carbide with the insulative properties of a hollow shell.
