The science of nano-technology is an emerging field with a host of novel and unique applications. Nanostructured materials are characterized by an ultra-fine microstructure having some physical feature less than 100 nanometers in size. This feature may be grain size, the diameter of a constituent particle or fiber, or a layer thickness. Following the initial discovery of the existence of the carbon nanotube, carbon, silicon-based, and other nanostructures have been an area of significant interest because of their unusual electrical and mechanical properties. Carbon nanotubes and silicon-based nanostructures offer promises for super strong materials and extremely small, fast computer chips, while doped silica nanofibers may offer new approaches for interconnects, transistors, luminescent devices, photo-detectors and chemical sensors.
However, major challenges have heretofore been unresolved, particularly with respect to developing efficient systems for (and methods of) production of ceramic nanostructured materials. Applications of silica, alumina and titania nanostructures may be enhanced by utilization of various alternative physical structures of these materials if various alternative physical structures could be produced efficiently. What are needed therefore are alternative morphologies and methods of fabrication of silica, alumina, and titania nanostructures, and other ceramic nanostructures.
To meet those needs, Babcock & Wilcox Technical Services Y-12, LLC (Oak Ridge, TN) scientists Edward B. Ripley, Roland D. Seals and Jonathan S. Morrell developed a 12 kW 2.45 GHz multi-mode microwave furnace capable of producing silica, alumina, and titania nanostructures, as well as other ceramic nanostructures. The workings of the furnace are detailed in U.S. Patent 7,622,189.
FIG. 4 is a flow chart (350) from the patent of the Babcock & Wilcox method for forming nano-ceramic nanostructures. The process begins in step 352 by disposing a metal catalyst particle on a substrate comprising a nano-ceramic material, such that a substrate interface is formed where the metal catalyst particle rests on the substrate. The substrate includes a material that dissolves in the metal catalyst particle at a temperature less than the boiling temperature of the metal catalyst particle. In step 354 the metal catalyst particle and the substrate are heated to a temperature between (1) a temperature at which at least a portion of the nano-ceramic material dissolves into the metal catalyst particle at the substrate interface and (2) the boiling point of the metal catalyst particle. In step 356, at least a portion of the nano-ceramic material is pumped from the substrate into the metal catalyst particle at the substrate interface until nanostructures made with the nano-ceramic material form on a polar site of the metal catalyst particle. The polar site is substantially opposed to the substrate interface (i.e., the polar site is substantially on the opposite side of the metal catalyst particle from the substrate interface). Finally, in step 358, the metal catalyst particle containing the pumped nano-ceramic material and the nanostructures is cooled to ambient temperature.