Researchers at the U.S. Air Force Research Laboratory are seeking to patent a novel process for manufacturing a type of material called preceramic polymer-grafted nanoparticles, or “hairy nanoparticles” (HNP).
An HNP is a hybrid material consisting of a polymer shell bound to a solid nanoparticle core. The polymer—a chain of repeating molecules—forms the “hair” around the nanoparticle, which is roughly the size of a small virus.
Although HNPs have been around for many years, what makes this one different is the type of polymer being attached to the core particle. It is a pre-ceramic polymer, a special class of polymer used in the formation of high-performance ceramic fibers and composites.
“The special polymer used in our process is what sets our work apart,” said project lead Dr. Matthew Dickerson. “Researchers have made these sort of hairy nanoparticles in the past, but they’ve used organic polymers like polystyrene. Our polymer is different; it’s inorganic because it contains silicon. It’s a bit like silicones (caulk), which have a backbone of silicon and oxygen repeats, but ours has a backbone of silicon and carbon repeats.”
This silicon and carbon chemistry allows the polymer to convert to a silicon carbide ceramic when heated to high temperatures.
The HNPs that result from this special process will be used in the manufacture of aircraft parts made of ceramic composite material.
“Ceramic composites are used for high-temperature U.S. Air Force applications that benefit from materials that are lower in density than metals, including jet engine and hypersonic vehicle components,” said Dickerson. “The HNPs we synthesized are envisioned for those type of applications.”
This special hybrid material, however, is not made by simply mixing the polymer and nanoparticles together and hoping for the best.
“A simple mixture would result in something like a putty or a brittle mixture,” said Dickerson, “but the hybrid material we end up with flows more like molasses so it will more easily flow into a porous ceramic.”