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Nickel sheet with nanoscale pores weighs less than titanium but is just as strong
January 30, 2019
Source: ASM International
In a new study published in Nature Scientific Reports, university researchers announce that they have fabricated a sheet of nickel with nanoscale pores that make it as strong as titanium but four to five times lighter. The scientists are from the University of Pennsylvania's School of Engineering and Applied Science, the University of Illinois at Urbana-Champaign, and the University of Cambridge.
The study was led by James Pikul, Assistant Professor in the Department of Mechanical Engineering and Applied Mechanics at Penn Engineering in Philadelphia. Bill King and Paul Braun at the University of Illinois at Urbana-Champaign, along with Vikram Deshpande at the University of Cambridge, contributed to the study.
Dr. Pikul's method starts with tiny plastic spheres, a few hundred nanometers in diameter, suspended in water. As the water is slowly evaporated, the spheres settle and stack like cannonballs, providing an orderly, crystalline framework. Using electroplating, the researchers then infiltrate the plastic spheres with nickel. Once the nickel is in place, the plastic spheres are dissolved with a solvent, leaving an open network of metallic struts. The empty space of the pores, and the self-assembly process in which they are made, make the porous metal akin to a natural material such as wood.
"We've made foils of this metallic wood that are on the order of a square centimeter,” Dr. Pikul says. "To give you a sense of scale, there are about a billion nickel struts in a piece that size." Because roughly 70 percent of the resulting material is empty space, its density is extremely low in relation to its strength. With a density on par with water, a brick of the material would float.
Just as the porosity of wood grain serves the biological function of transporting energy, the empty space in this "metallic wood" could be infused with other materials. For example, infusing the scaffolding with anode and cathode materials could enable this metallic wood to serve double duty as both a structure and a battery.
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