United States. A team at Northwestern University has developed a new coating strategy for metal that heals in seconds when scratched, scraped or cracked. The new material could prevent these small defects from turning into localized corrosion, which can cause major structures to fail.
"Localized corrosion is extremely dangerous," said Jiaxing Huang, who led the research. "It's hard to prevent, it's hard to predict, and it's hard to detect, but it can lead to catastrophic failure."
When damaged by scratches and cracks, Huang's patent-pending system flows easily and reconnects to heal quickly before the eyes. The researchers showed that the material can be cured repeatedly, even after scratching the same place almost 200 times in a row.
The study was published in Research, the first Science Partner Journal recently launched by the American Association for the Advancement of Science (AAAS) in collaboration with the China Association for Science and Technology (CAST). Huang is a professor of materials science and engineering at Northwestern's McCormick School of Engineering.
While some self-healing coatings already exist, those systems generally work for damage from nanometers to microns. To develop a coating that can cure larger scratches on the millimeter scale, Huang and his team looked for fluids.
"When a boat goes through the water, the water comes back together," Huang said. "The 'cut' heals quickly because the water flows easily. We were inspired to realize that fluids, like oils, are the best self-healing system."
But ordinary oils flow too easily, Huang noted. Therefore, he and his team needed to develop a system with contradictory properties: fluid enough to flow automatically but not so fluid that they drip from the surface of the metal.
The team faced the challenge by creating a network of lightweight particles, in this case graphene capsules, to thicken the oil. The net corrects the oil coating, preventing it from dripping. But when the network is damaged by a crack or scratch, it releases the oil so that it flows easily and reconnects. Huang said the material can be made from any hollow, lightweight particle, not just graphene.
"The particles essentially immobilize the oil film," Huang said. "So it stays in place."
Areas of application
The coating not only sticks, but adheres well, even underwater and in harsh chemical environments, such as acid baths. Huang imagines it could be painted on bridges and ships that naturally submerge underwater, as well as metal structures near highly corrosive fluids spilled or spilled.
The coating can also withstand strong turbulence and adhere to sharp corners without giving way. When brushed onto a surface underwater, the coating continues evenly without trapping small air bubbles or moisture that often lead to holes and corrosion.
The Office of Naval Research (ONR N000141612838) endorsed "thickened oil barrier coatings with self-healing microcapsules." Graduate students Alane Lim and Chenlong Cui, a former member of Huang's research group, authored the paper.
Data Source Provider: Northwestern University.
