Silicon-Based Coating Slows Spread of Fire


A team of researchers from North Carolina State University recently found an application for a silene material that can be applied to surfaces like wood, creating a barrier between combustible molecules and flame.

The paper was recently published in the journal Angewandte Chemie.

About the Research

According to a release from the university, the researchers developed a technique that utilizes the molecule-thin protective layer to control how heat interacts with the processed material.

“Fire is a valuable engineering tool—after all, a blast furnace is only an intense fire,” said Martin Thuo, corresponding author of a paper on the work and a professor of materials science and engineering at NC State. “However, once you start a fire, you often have little control over how it behaves.

“Our technique, which we call inverse thermal degradation (ITD), employs a nanoscale thin film over a targeted material. The thin film changes in response to the heat of the fire, and regulates the amount of oxygen that can access the material.

“That means we can control the rate at which the material heats up—which, in turn, influences the chemical reactions taking place within the material. Basically, we can fine-tune how and where the fire changes the material.”

ITD reportedly starts with a target material, such as cellulose fiber, which is then coated with a nanometer thick layer of molecules. These coated fibers are then exposed to an intense flame, which causes the outer surfaces of the molecules to combust and raise the temperature in the immediate vicinity, the researchers say.

However, the inner surface of the molecular coating chemically changes, creating an even thinner layer of glass around the cellulose fibers. This glass reportedly limits the amount of oxygen that can access the fibers, preventing the cellulose from bursting into flames and allowing them to burn slowly from the inside out.

“Without the ITD’s protective layer, applying flame to cellulose fibers would just result in ash,” Thuo explained. “With the ITD’s protective layer, you end up with carbon tubes.

“We can engineer the protective layer in order to tune the amount of oxygen that reaches the target material. And we can engineer the target material in order to produce desirable characteristics.”

The university says that the team conducted proof-of-concept demonstrations with cellulose fibers to produce microscale carbon tubes. They could reportedly control the thickness of the carbon tube walls by:

  • Controlling the size of the cellulose fibers they started with;
  • Introducing various salts to the fibers (which further controls the rate of burning); and
  • Varying the amount of oxygen that passes through the protective layer.

“We have several applications in mind already, which we will be addressing in future studies,” Thuo said. “We’re also open to working with the private sector to explore various practical uses, such as developing engineered carbon tubes for oil-water separation – which would be useful for both industrial applications and environmental remediation.”

Thuo told Dezeen in an interview that the coating could be used to help fight wildfires, with the possibility of erecting perimeter walls coated in the nanomaterial around settlements to keep the fire out and to give firefighters more time.

His work on applying the material has also reportedly been aimed towards “semi-permanent structures,” but has been working with architects and other scientists with plans to build entire structures to test how the coating would function in a “disaster.”

The coating is also reportedly “almost undetectable,” applied using an oil-like solvent in a spray or applied as a fume in a chamber. It also had success in keeping out water and insects, the team found.

Where other fireproofing techniques involve using paints that release chemicals to suppress the fire or thick cement-like coating, this nanocoating uses small chemical reactions that do "not have toxic emissions on burning", according to Thuo.

Thuo added that the material is not meant to make buildings completely fireproof—only to slow the flame and give inhabitants and firefighters more time.

Co-authors of the research include Dhanush Jamadgni and Alana Pauls, Ph.D., students at NC State; Julia Chang and Andrew Martin, postdoctoral researchers at NC State; Chuanshen Du, Paul Gregory, Rick Dorn and Aaron Rossini of Iowa State University; and E. Johan Foster at the University of British Columbia.


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