Silicon carbide ‘fuzz’ stands up to heat and abuse.
Scientists at Rice University have developed a fuzzy velcro-like material composed of silicon carbide nanotubes which stands up well to the punishing conditions in the aerospace industry. Working in collaboration with NASA, the research team’s new “fuzzy fibers” may protect the next generation of rocket engines from heat and damage.
The fibers can be used to strengthen the composite materials used in rocket engines to help them withstand the searing temperatures of up to 1600 degrees Celsius. Conventional ceramic composites already in use are spiked with silicon carbide fibers as well, but they run the risk of becoming brittle after exposure to oxygen, and cracking as a result. The solution brought forth by Rice University prevents this, partially by providing support for the fibers, and by sealing them from exposure to oxygen.
The fuzzy fibers make use of carbon nanotubes and nanowires, which are embedded into the surface of NASA’s fibers. The ends of these fibers stick out and form loops, similar to the fiber loops of velcro, but on a much smaller scale. Lead researchers Amelia Hart, a Rice graduate student, and Chandra Sekhar Tiwary, a Rice postdoctoral associate, say that the loops create “very strong interlocking connections where the fibers tangle.”
The discovery is a combined effort between Hart’s research, and that of NASA research engineer and paper co-author Janet Hurst. “She was partially converting silicon carbide from carbon nanotubes,” Hart said. “We used her formulation and my ability to grow nanotubes and figured out how to make the new composite.” The Rice university research team created the new material by bathing silicon carbide fibers in a solution containing an iron catalyst, and then used water-assisted chemical vapor deposition (CVD) to embed a carpet of carbon nanotubes directly into the surface of the fiber. By heating the fibers while covered in a silicon nanopowder, the carbon nanotubes became “fuzzy”.
The silicon carbon fibers in use by NASA are already capable of withstanding the required 1600 degree temperature, so the making the material fuzzy stands a good chance of making the material even more resistant to heat. The material isn’t just limited to NASA though; there are several conventional applications as well, including for the development of new jet engines: “Before they used silicon carbide composites, many engine parts were made of nickel superalloys that had to incorporate a cooling system, which added weight to the whole thing,” said Hart, “By switching to ceramic matrix composites, they could take out the cooling system and go to higher temperatures. Our material will allow the creation of larger, longer-lasting turbo jet engines that go to higher temperatures than ever before.”