Tag Archives: Northwestern University

Self-Healing Coating Protects Metals From Corrosion

It’s hard to believe that a tiny crack could take down a gigantic metal structure. But sometimes bridges collapse, pipelines rupture and fuselages detach from airplanes due to hard-to-detect corrosion in tiny cracks, scratches and dents. A Northwestern University team has developed a new coating strategy for metal that self-heals within seconds when scratched, scraped or cracked. The novel material could prevent these tiny defects from turning into localized corrosion, which can cause major structures to fail.

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Localized corrosion is extremely dangerous,” said Jiaxing Huang, who led the research. “It is hard to prevent, hard to predict and hard to detect, but it can lead to catastrophic failure.” Huang is a professor of materials science and engineering in Northwestern’s McCormick School of Engineering.

When damaged by scratches and cracks, Huang’s patent-pending system readily flows and reconnects to rapidly heal right before the eyes. The researchers demonstrated that the material can heal repeatedly — even after scratching the exact same spot nearly 200 times in a row.While a few self-healing coatings already exist, those systems typically work for nanometer- to micron-sized damages. To develop a coating that can heal larger scratches in the millimeter-scale, Huang and his team looked to fluid. “When a boat cuts through water, the water goes right back together,” Huang said. “The ‘cut’ quickly heals because water flows readily. We were inspired to realize that fluids, such as oils, are the ultimate self-healing system.” But common oils flows too readily, Huang noted. So he and his team needed to develop a system with contradicting properties: fluidic enough to flow automatically but not so fluidic that it drips off the metal’s surface.

The team met the challenge by creating a network of lightweight particles — in this case graphene capsules — to thicken the oil. The network fixes the oil coating, keeping it from dripping. But when the network is damaged by a crack or scratch, it releases the oil to flow readily and reconnect. Huang said the material can be made with any hollow, lightweight particlenot just graphene. “The particles essentially immobilize the oil film,” Huang said. “So it stays in place.”

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).

Source: https://news.northwestern.edu/

Megalibrary To Boost Discovery of New Materials

Different eras of civilization are defined by the discovery of new materials, as new materials drive new capabilities. And yet, identifying the best material for a given application—catalysts, light-harvesting structures, biodiagnostic labels, pharmaceuticals and electronic devices—is traditionally a slow and daunting task. The options are nearly infinite, particularly at the nanoscale (a nanometer is one-billionth of a meter) where material propertiesoptical, structural, electrical, mechanical and chemical—can significantly change, even at a fixed composition.

A new study published this week in the Proceedings of the National Academy of Sciences (PNAS) supports the efficacy of a potentially revolutionary new tool developed at Northwestern University to rapidly test millions (even billions) of nanoparticles to determine the best for a specific use.

Laser-induced heating of nanoparticles on micropillars for carbon nanotube growth

When utilizing traditional methods to identify new materials, we have barely scratched the surface of what is possible,” said Northwestern’s Chad A. Mirkin, the study’s corresponding author and a world leader in nanotechnology research and its applications. “This research provides proof-of-concept—that this powerful approach to discovery science works.”

The novel tool utilizes a combinatorial library, or megalibrary, of nanoparticles in a very controlled way. (A combinatorial library is a collection of systematically varied structures encoded at specific sites on a surface). The libraries are created using Mirkin’s Polymer Pen Lithography (PPL) technique, which relies on arrays (sets of data elements) with hundreds of thousands of pyramidal tips to deposit individual polymerdots” of various sizes and composition, each loaded with different metal salts of interest, onto a surface. Once heated, these dots are reduced to metal atoms forming a single nanoparticle at fixed composition and size.

By going small, we create two advantages in high throughput materials discovery,” said Mirkin, the executive director of Northwestern’s International Institute for Nanotechnology (IIN). “First, we can pack millions of features into square-centimeter areas, creating a path for making the largest and most complex libraries, to date. Second, by working at the sub-100 nanometer-length scale, size can become a library parameter, and much of the action, for example, in the field of catalysis, is on this length scale.”

Source: https://news.northwestern.edu/