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Researchers discover razor-like 'nanoblades'

Posted: 27 Sep 2007 ?? ?Print Version ?Bookmark and Share

Keywords:nanoblade? fuel cell? energy storage?

The September 2007 issue of the Journal of Nanoscience and Nanotechnology detailed the discovery of razor-like nanoblades that could be applied in energy storage and fuel cell technology.

Researchers at the Rensselaer Polytechnic Institute (RPI) claim that the nanoblades are first-of-their-kind magnesium nanomaterials that challenge the conventional wisdom about nanostructure growth.

The sharp nanometer-scale surface is different from other nanomaterials created using oblique angle deposition, according to lead researcher Gwo-Ching Wang, professor and head of physics, applied physics and astronomy at RPI.

The team's nearly two-dimensional structure changes the traditional understanding of oblique angle deposition, which was previously thought to create only cylindrical structures like nanorods or nanosprings.

Unlike 3D springs and rods, nanoblades are extremely thin, with relatively large surface areas. They also are surprisingly dispersed for a uniform nanomaterial, with one to 2?m in between each blade, Wang said.

The materials could be extremely useful for energy storage, particularly hydrogen storage, Wang said. In order to store hydrogen, a large surface area is needed to provide room for the material to expand as more hydrogen atoms are stored. The vast surface area of each nanoblade, coupled with the large spaces between each blade, could make them ideal for storage applications.

To create the nanoblades, the researchers used an oblique angle vapor deposition fab technique that builds nanostructures by vaporizing magnesium. Vaporized atoms are deposited on the surface at an angle. As the deposition angle changes, the structure of the material deposited on the surface also changes.

According to the report, when the magnesium was deposited directly onto a surface at zero degrees, the blades were flat, flakey structures overlapping one another. When the deposition angle was increased blade-like structures became apparent. The nearly vertical structures resembled nanoscale razor blades. From the side, the nanoblades resemble an overgrown lawn with thin, blade-like spires. At a 75 angle, the nanoblades had a thickness of as little as 15nm and a width of a few hundred nanometers.

Slide view of RPI's nanoblades

The researchers monitored the blades as they were growing using a reflection high-energy electron diffraction technique to create a surface pole figure or image. RPI's technique differs from other diffraction techniques such as X-rays by monitoring a material's surface structure as it grows. X-rays and other technologies measure the entire material, from the tip of the new growth straight through to the substrate on which the material is growing.

Tracking the surface evolution of the material provides insight into how the structure evolves over time and helps scientists understand the mechanism of nanostructure formation. This could allow engineers to recreate ideal nanomaterials in the future. The creation of surface pole figures was particularly important in understanding the growth of nanoblades, as the surface morphology changed dramatically over time.

The RPI researchers are now looking at ways to coat the magnesium nanoblades with metallic catalysts to trap and store hydrogen.

- Nicolas Mokhoff
EE Times

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