TAGS: Industrial Coatings
Researchers from the University of Nebraska–Lincoln and the Institute of Condensed Matter Chemistry of Bordeaux in France have developed a low-cost, scalable method for guarding carbon fiber against oxidation using protective coating. The approach represents a significant improvement over other antioxidation processes that are laborious, slow and expensive.
Coating Made of Chromium Carbide and Titanium Carbide
Dipping carbon fibers into a molten salt mixture containing titanium and chromium powders triggers a spontaneous reaction that leaves the fibers with a three-layer protective coating. The layers are made of chromium carbide and titanium carbide.
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We are trying to add surface layers that can separate carbon fibers from oxygen so that even under high temperatures, they won’t be burned,” Husker engineer Yongfeng Lu, an expert in carbon materials, said.
“Carbon fibers can be used in many ways — woven into textiles and in parts of buildings, airplanes, electronics equipment — but if they’re flammable, that poses a new risk to the system and limits those applications a lot.”
Single-step Process to Eliminate Flammability
To eliminate flammability, Lu’s team has devised a simple, single-step process that starts with melting a salt that is very similar chemically to table salt. After the salt crystals become a liquid, the researchers add titanium and chromium powders, which are known to withstand high temperatures. Carbon fibers are then added to the mix.
After a spontaneous reaction, the process yields a three-layer coating — made of chromium carbide and titanium carbide — that serves as a barrier against oxidation. The coating is multilayered because titanium and chromium each have different behaviors and reaction rates within the molten salt, leading to three distinct layers of end product. This triple coating confers extra protection when compared to a single layer.
When the researchers evaluated the coated carbon fibers against extreme temperatures — about 2,200 degrees Fahrenheit — and extreme environmental conditions they simulated with an oxyacetylene flame, they found that the carbon material maintained its structure. Lu said the next step is identifying just how fireproof the coated fibers are compared to their unprotected counterparts, and how long they can retain their most valuable properties under extreme conditions.
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We’ve found a recipe that can form three layers in a single state,” Lu said. “With one single dip, we can get three layers of coating.”
Source: University of Nebraska–Lincoln