A new composite developed by NASA and Rice University, TX, researchers should aid in the design of advanced rocket engine components that must withstand high-heat conditions. Fuzzy fibers of silicon carbide strengthen the materials already used for this application by forming strong interlocking connections where the fibers tangle. This property makes the composite less prone to cracking and seals it to prevent oxygen from changing the fiber’s chemical composition.

The researchers embedded silicon carbide nanotubes and nanowires into fiber surfaces. The exposed parts of the fibers are curly and act like the hooks and loops that make Velcro so valuable—but on the nanoscale.Silicon carbide nanotubes attached to separate silicon carbide fibers entangle each other in this electron microscope image. Image credit: The Ajayan Research Group, Rice University

The Velcro-like hooks and loops are grown by bathing silicon carbide fiber in an iron catalyst, followed by water-assisted chemical vapor deposition, to embed a carpet of carbon nanotubes directly into the surface. After heating the fibers in silicon nanopowder at high temperature, the carbon nanotubes are converted to silicon carbide “fuzz.”

The fuzzy fibers are intended to upgrade the strong, light and heat-resistant silicon carbide fibers that, when put in ceramic composites, are being tested for robust nozzles and other parts in rocket engines. The ceramic matrix composites should also make entire turbo engines significantly lighter by eliminating use of nickel superalloys and attendant cooling systems.

Testing showed the fibers easily bounced back from high compression applied with a nano-indenter, confirming their ability to resist breaking down for longer amounts of time. Heat trials demonstrated that plain carbon nanotubes burned away from the fibers, but the silicon carbide nanotubes easily resisted temperatures of up to 1,000° C (1,832° F).