Ceramic nanofibers can be tangled into a sponge that looks like a cotton ball. Source: Brown UniversityResearchers at Brown University have developed a lightweight sponge-like materials made from nanoscale ceramic fibers that are porous, compressible and heat-resistant.

The sponge substance could be used for future water purification systems or flexible insulating materials.

“The basic science question we tried to answer is how can we make a material that’s highly deformable but resistant to high temperature,” says Huajian Gao, a professor in Brown University’s School of Engineering. The researchers were able to tangle ceramic nanofibers into a sponge using inexpensive materials that are scalable to be made into large quantities.

While ceramic is a very brittle material, at the nanoscale, the cracks and flaws becomes so small that it takes much more energy to activate them and cause them to spread. The fibers have a deformation mechanism that enables the material to deform without breaking, researchers say.

The material made from the ceramic nanofibers have the potential to be deformed and flexible while maintaining the heat resistance that makes ceramics useful in high temperature applications. The problem is that such materials are not easy to make.

How They Did It

One way to create nanofibers is through a process called electrospinning, but this doesn’t work well with ceramics and other options—such as 3-D laser printing—is expensive and time consuming.

Instead, researchers used a method called blow-spinning that uses air pressure to drive a liquid solution containing ceramic material through a tiny syringe aperture. As the liquid emerges, it solidifies into nanoscale fibers that are collected in a spinning cage. The material is then heated and burns away the solvent material leaving a mass of tangled ceramic nanofibers that looks like a cotton ball.

The researchers yielded sponges from a variety of different types of ceramics and found the sponges were able to rebound after compressive strain up to 50%, something standard ceramic material can’t do. The spongers also maintained its heat resilience at temperatures up to 800 degrees Celsius.

These characteristics would lead this material to be used as an insulating material where flexibility is important such as firefighters’ clothing. It could also be used in water purification where the sponge could absorb 50 times its weight in water containing organic dye. In 15 minutes, the sponge was able to degrade the dye under illumination. When the sponge was wrung out, it could then be reused.

“The process we used for making these is extremely versatile; it can be used with a great variety of different types of ceramic starting materials,” says Hui Wu, a researcher at Tsinghua University in China that helped with the project. “So we think there’s huge prospect for potential applications.”

The full research report can be found in the journal Science Advances.