The new foam is formed from hexagonal-boron nitride molecules, held together with polyvinyl alcohol. The foam has been developed at Rice University. The foam is light and made from two-dimensional molecular sheets. The foam was made using a freeze-drying process, which requires the use of sophisticated digitally controlled devices. This process creates the boron nitride foam; the addition of polyvinyl alcohol into the mix transforms it into a far more robust and useful material. Here the polyvinyl alcohol functions as a glue, helping to bind the boron nitride molecules as microscopic sheets into a lattice.
The developed foam is highly porous. The applications will include use inside air filters and as gas absorption materials. The aim is to soak up carbon dioxide and prevent it from being released into the atmosphere.
The technical process of freeze drying (correctly termed lyophilization) is a dehydration process typically that preserves materials. The process works by freezing the material and then reducing the surrounding pressure to allow the frozen water in the material to sublime directly from the solid phase to the gas phase. For this digital controls are required to allow the process to meet tightly defined parameters.
The following video reveals more about the foam:
Speaking with Controlled Environments magazine, one of the researchers, Dr. Chandra Sekhar Tiwary said that the addition of polyvinyl alcohol was critical to the development: “It helps make the foam stiff by gluing the interconnects between the hexagonal-boron nitride sheets – and at the same time, it hardly changes the surface area at all.”
In trials the foam was able to adsorb 340 percent of its own weight in carbon dioxide. Later the environmental pollutant gas can be evaporated out of the material and then reused repeatedly. The foam is capable of being reused for up to 2,000 cycles.
There may also be a further application for the foam. When it is coated with a different polymer, called PDMS the foam works as a shield from lasers. This means it could be used in biomedical, electronics and other applications. Another possibility is using the foam to help to separate oil from water, thus using the foam for addressing oil slicks.
The research findings have been reported to the American Chemical Society journal ACS Nano. The research paper is headed “Lightweight Hexagonal Boron Nitride Foam for CO2 Absorption.”
