Researchers Develop New Pre-Ceramic Polymer
A water-like polymer has been developed that can facilitate the creation of high-temperature ceramics suitable for multiple applications.
Using five ingredients (silicon, boron, carbon, nitrogen and hydrogen), Gurpreet Singh, the Harold O. and Jane C. Massey Neff associate professor of mechanical and nuclear engineering at Kansas State University, has created a liquid polymer that can transform into a ceramic with valuable thermal, optical, and electronic properties. The water-like polymer, which becomes a ceramic when heated, also can be mass produced.
“This polymer is a useful material that really works,” Singh said. “Of all the materials that we have researched in the last five years, this material is the most promising. Now we can think of using ceramics where you could never even imagine.”
Singh is the lead inventor of the patent for “boron-modified silazanes for synthesis of SiBNC ceramics.” Romil Bhandavat, 2013 doctoral graduate in mechanical engineering, is a co-inventor. The engineers developed a clear polymer that looks like water and has the same density and viscosity as water, unlike some other silicon- and boron-containing polymers. As a pre-ceramic polymer, the liquid material has several important properties:
- Low density—can create lightweight ceramics
- Scalable—can be mass-produced in grams or kilograms
- Processing flexibility—can be poured into molds and heated to make complex ceramic shapes
The ceramic derived from this polymer has a random structure that is generally not observed in traditional ceramics. The silicon in the ceramic bonds to nitrogen and carbon but not boron, while boron bonds to nitrogen but not carbon, and carbon bonds to another carbon to form graphene-like strings. According to the researchers, this structure provides stability at high temperature (up to approximately 1,700°C) by delaying reaction with oxygen. In addition, the ceramic has a mass density three to six times lower than that of other ultra-high-temperature ceramics, such as zirconium boride and hafnium carbide.
“We have created a liquid that remains a liquid at room temperature and has a longer shelf life than other SiBNC polymers,” Singh said. “But when you heat our polymer, it undergoes a liquid-to-solid transition. This transparent liquid polymer can transform into a very black, glasslike ceramic.”
Because the polymer is a liquid, it is sprayable or can be used as a paint to make ceramic coatings. The ceramic can protect substrate materials or can create more efficient machinery that works in high-temperature environments such as steam turbines or jet engine blades. The polymer also may be used for the 3D printing of ceramic parts using a benchtop stereolithography (SLA) printer.
Another potential application is the creation of ceramic fibers. If the polymer is heated to approximately 50-100°C, it becomes a gel similar to syrup or honey. During this gel state, the polymer can be pulled into strings or fibers to create ceramic textiles or ceramic mesh.
When combined with carbon nanotubes, the polymer can create a black material that can absorb all light—even ultraviolet and infrared light—without being damaged. The combined nanomaterial can withstand extreme heat of 15,000 watts/cm2, which is about 10 times more heat than a rocket nozzle.
The polymer could be used to produce ceramic with tunable electrical conductivity ranging from insulator or semiconductor. In addition, the presence of silicon and graphene-like carbon in the ceramic can improve electrodes for lithium-ion batteries.
“Often, researchers have only looked at high-temperature properties,” Singh said. “We are among the few that looked at other properties—such as electronic, electro-chemical, thermal and optical properties—and exposed these properties in this material.”
Singh’s research has been supported by the National Institute of Standards and Technology radiometry team and the National Science Foundation. He is continuing to research the polymer’s possibilities for making ceramic fibers and battery electrodes. The patent was issued to the Kansas State University Research Foundation, a nonprofit corporation responsible for managing technology transfer activities at the university.