Rensselaer Research ReviewWinter 2008
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Advances in Nanotechnologhy
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Crazing epoxy composites
Researchers at Rensselaer have discovered a new technique for provoking unusual crazing behavior in epoxy composites. The crazing could lead to tougher, more durable components
for aircraft and automobiles.
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This spring, Rensselaer continued its innovations in nanotechnology. Among those discoveries were:

Fitter Frames: Nanotubes Boost Structural Integrity of Composites

Professor Nikhil Koratkar, of Rensselaer’s Department of Mechanical, Aerospace, and Nuclear Engineering, has demonstrated that incorporating chemically treated carbon nanotubes into an epoxy composite can significantly improve the overall toughness, fatigue resistance, and durability of a composite frame. 

When subjected to repetitive stress, a composite frame infused with treated nanotubes exhibited a five-fold reduction in crack growth rate as compared to a frame infused with untreated nanotubes, and a 20-fold reduction when compared to a composite frame made without nanotubes.

This newfound toughness and crack resistance is due to the treated nanotubes, which enhance the molecular mobility of the epoxy at the interface where the two materials touch.  When stressed, this enhanced mobility enables the epoxy to craze — or result in the formation of a network of pillar-like fibers that bridge together both sides of the crack and slow its growth.

This discovery could lead to tougher, more durable composite frames for aircraft, watercraft, and automobiles. 

Slimmer, Stickier Nanorods Give Boost to 3-D Computer Chips

Researchers at Rensselaer Polytechnic Institute have developed a new technique for growing slimmer copper nanorods. These thinner copper nanorods fuse together, or anneal, at about 300 degrees Celsius. This relatively low annealing temperature could make the nanorods ideal for use in heat-sensitive nanoelectronics, particularly for “gluing” together the stacked components of 3-D computer chips.

Experimental 3-D computer chips are comprised of several layers of stacked components. Pei-I Wang, research associate at Rensselaer’s Center for Integrated Electronics, said these layers can be coated with thin nanorods, and then heated up to 300 degrees Celsius. Around that temperature, the thin nanorods anneal, turn into a continuous thin film, and fuse the layers together. This study was the first demonstration of slimmer nanorods enabling wafer bonding, according to Wang.

The slimmer copper nanorods were formed by periodically interrupting the growth process. The vapor-deposition process was occasionally halted, and the fledgling nanorods were exposed to oxygen. This resulted in a forest of nanorods with diameters between 10 nanometers and 50 nanometers — far smaller than the typical 100-nanometer diameter copper nanorods grown conventionally without interruption. 

Wang and the research group have filed for a patent for this new technology. The patent is currently pending.

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nanorods nanorods
Researchers found that interrupting the nanorod growth process results in thinner rods. Pictured are scanning electron images, at the same magnification, of copper nanorods that have been grown without interruption (left) and with six interruptions (right).
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“Advances in Nanotechnology”
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