August 23, 2017 2:03:21 pm
Scientists, including those of Indian origin, have created a reusable boron nitride foam that soaks up carbon dioxide, and may be used in air filters and as gas absorption material. Researchers at Rice University in the US discovered that freeze-drying hexagonal-boron nitride (h-BN) turned it into a macro-scale foam that disintegrates in liquids.
However, adding polyvinyl alcohol (PVA) into the mix transformed it into a far more robust and useful material. The foam is highly porous and its properties can be tuned for use in air filters and as gas absorption materials, according to researchers in the lab of materials scientist Pulickel Ajayan from Rice University.
The polyvinyl alcohol serves as a glue. Mixed into a solution with flakes of h-BN, it binds the junctions as the microscopic sheets arrange themselves into a lattice when freeze-dried. The one-step process is scalable, researchers said. “Even a very small amount of PVA works,” said Chandra Sekhar Tiwary, postdoctoral researcher at Rice.
“It helps make the foam stiff by gluing the interconnects between the h-BN sheets – and at the same time, it hardly changes the surface area at all,” said Tiwary, co-author of the research published in the journal ACS Nano. In molecular dynamics simulations, the foam adsorbed 340 per cent of its own weight in carbon dioxide. The greenhouse gas can be evaporated out of the material, which can be reused repeatedly, Tiwary said.
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Compression tests showed the foam got stiffer through 2,000 cycles as well. When coated with PDMS, another polymer, the foam becomes an effective shield from lasers that could be used in biomedical, electronics and other applications, he said. The researchers want to gain control over the size of the material’s pores for specific applications, like separating oil from water.
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