David Kirkpatrick

March 27, 2009

Nanotubes strengthen epoxy composites

Filed under: Science, Technology — Tags: , , , — David Kirkpatrick @ 1:11 am

The lastest in carbon nanotube applications.

The release:

Fitter Frames: Nanotubes Boost Structural Integrity of Composites

Researchers at Rensselaer have discovered a new technique for provoking unusual crazing behavior in epoxy composites. The crazing, which causes the composite to deform into a network of nanoscale pillar-like fibers that bridge together both sides of a crack and slow its growth, could lead to tougher, more durable components for aircraft and automobiles.

New research finding could lead to more durable aircraft, automotive components

A new research discovery at Rensselaer Polytechnic Institute could lead to tougher, more durable composite frames for aircraft, watercraft, and automobiles. 

Epoxy composites are increasingly being incorporated into the design of new jets, planes, and other vehicles. Composite material frames are extremely lightweight, which lowers the overall weight of the vehicle and boosts fuel efficiency. The downside is that epoxy composites can be brittle, which is detrimental to its structural integrity. 

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 crazing behavior, and the bridging fibers it produces, dramatically slows the growth rate of a crack,” Koratkar said. “In order for the crack to grow, those fibers have to first stretch, deform plastically, and then break. It takes a lot of energy to stretch and break those fibers, energy that would have otherwise gone toward enlarging the crack.”

Results of the study were published this week in the journal Small.

Epoxy composites infused with carbon nanotubes are known to be more resistant to cracks than pure epoxy composites, as the nanotubes stitch, or bridge, the two sides of the crack together. Infusing an epoxy with carbon nanotubes that have been functionalized, or treated, with the chemical group amidoamine, however, results in a completely different bridging phenomenon.

At the interface of the functionalized nanotubes and the epoxy, the epoxy starts to craze, which is a highly unusual behavior for this particular type of composite, Koratkar said. The epoxy deforms, becomes more fluid, and creates connective fibers up to 10 microns in length and with a diameter between 100 nanometers and 1,000 nanometers.

“We didn’t expect this at all. Crazing is common in certain types of thermoplastic polymers, but very unusual in the type of epoxy composite we used,” Koratkar said. “In addition to improved fatigue resistance and toughness, the treated nanotubes also enhanced the stiffness, hardness, and strength of the epoxy composite, which is very important for structural applications.” 

Koratkar said the aircraft, boat, and automobile industries are increasingly looking to composites as a building material to make vehicle frames and components lighter. His research group plans to further investigate crazing behavior in epoxy composites, in order to better understand why the chemical treatment of nanotubes initiates crazing.

Co-authors of the paper include Rensselaer Associate Professor Catalin Picu, of the Department of Mechanical, Aerospace, and Nuclear Engineering; Rensselaer doctoral students Wei Zhang and Iti Srivastava; and Yue-Feng Zhu, professor in the Department of Mechanical Engineering at Tsinghua University in China.

Visit Koratkar’s Web site for more information on his nanomaterials research.

Published March 26, 2009

March 18, 2009

Nanorods boost 3D computer chips

Cool nanotech news in the world of chip manufacture.

The release:

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

Researchers at Rensselaer Polytechnic Institute have discovered a new method for growing slimmer copper nanorods, which can be used as a low-temperature bonding agent for holding together the layers of next-generation 3-D integrated computer chips. The 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 (top), with two interruptions (middle), and with six interruptions (bottom).

Researchers at Rensselaer Polytechnic Institute have developed a new technique for growing slimmer copper nanorods, a key step for advancing integrated 3-D chip technology.

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.

“When fabricating and assembling 3-D chips, and when bonding the silicon wafers together, you want as low a temperature as possible,” said Pei-I Wang, research associate at Rensselaer’s Center for Integrated Electronics. “Slimmer nanorods, by virtue of their smaller diameters, require less heat to anneal. These lower temperatures won’t damage or degrade the delicate semiconductors. The end result is a less expensive, more reliable device.” 

Experimental 3-D computer chips are comprised of several layers of stacked components. Wang 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.

Fundamental research concerning the slimmer nanorods was led by Toh-Ming Lu, the R.P. Baker Distinguished Professor of Physics at Rensselaer. Results of the study were recently published in the journal Nanotechnology.

Research into wafer bonding and incorporating the slimmer nanorods into 3-D integrated computer chips was led by James Jian-Qiang Lu, associate professor in the Department of Electrical, Computer, and Systems Engineering (ECSE) and the Center for Integrated Electronics (CIE) at Rensselaer. Results of the study were recently published in the journal Electrochemical and Solid-State Letters.

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. 

Vast forests, or arrays, of copper nanorods are produced by vapor deposition at an oblique angle. In a conventional setting, with an uninterrupted stream of copper atoms deposited in a vacuum onto a substrate, the deposition angle naturally results in taller, thicker nanorods.

Periodically interrupting the deposition, and exposing the copper nanorods to ambient air, however, leads to oxygen being absorbed into the surface of the nanorods. During subsequent depositions, this oxidized copper helps to prevent the vaporized copper atoms from migrating away from the very tips of the nanorods. This ensures the nanorods grow taller, without necessarily growing in diameter. The more growth interruptions, the thinner the resulting nanorods, Wang said.

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

Along with Wang and Toh-Ming Lu, co-authors of the Nanotechnology paper include Gwo Ching Wang, professor and chair of the Department of Physics, Applied Physics, and Astronomy at Rensselaer; Rensselaer physics graduate student Thomas C. Parker; and Tansel Karabacak, assistant professor in the Department of Applied Science at the University of Arkansas at Little Rock.

Co-authors of the Electrochemical and Solid-State Letters paper include Pei-I Wang, Toh-Ming Lu, James Jian-Qiang Lu, Parker, Karabacak, along with Rensselaer research associate Sang Hwui Lee, and Rensselaer Center for Integrated Electronics Senior Applications Engineer Michael D. Frey. 

Funding for the research reported in the Electrochemical and Solid-State Letters was provided by the New York State Foundation for Science, Technology and Innovation (NYSTAR) through the Interconnect Focus Center-New York.

Visit Toh-Ming Lu’s Web site for more information on advanced thin-film research, or James Jian-Qiang Lu’s Web site for more information on research into 3-D integrated semiconductors.

December 18, 2008

LED lighting news, part two

Okay, I’ve already posted one release on this very bit of news, but this one is a bit different — and it comes with pictures! So there you go.

It goes without saying, I’ve really been looking forward to cost-effective LED lighting for the home.

The release:

Researchers lay out vision for lighting ‘revolution’

LEDs and smart lighting could save trillions of dollars, spark global innovation

IMAGE: If all of the world’s light bulbs were replaced with energy-efficient LEDs for a period of 10 years, researchers say it would reduce global oil consumption by 962 million barrels,…

Click here for more information. 

Troy, N.Y. – A “revolution” in the way we illuminate our world is imminent, according to a paper published this week by two professors at Rensselaer Polytechnic Institute.

Innovations in photonics and solid state lighting will lead to trillions of dollars in cost savings, along with a massive reduction in the amount of energy required to light homes and businesses around the globe, the researchers forecast.

A new generation of lighting devices based on light-emitting diodes (LEDs) will supplant the common light bulb in coming years, the paper suggests. In addition to the environmental and cost benefits of LEDs, the technology is expected to enable a wide range of advances in areas as diverse as healthcare, transportation systems, digital displays, and computer networking.

“What the transistor meant to the development of electronics, the LED means to the field of photonics. This core device has the potential to revolutionize how we use light,” wrote co-authors E. Fred Schubert and Jong Kyu Kim.

IMAGE: If all of the world’s light bulbs were replaced with energy-efficient LEDs for a period of 10 years, researchers say it would reduce global oil consumption by 962 million barrels,…

Click here for more information. 

Schubert is the Wellfleet Senior Constellation Professor of Future Chips at Rensselaer, and heads the university’s National Science Foundation-funded Smart Lighting Center. Kim is a research assistant professor of electrical, computer, and systems engineering. The paper, titled “Transcending the replacement paradigm of solid-state lighting,” will be published in the Dec. 22, 2008 issue of Optics Express.

To read the full paper, visit: http://www.opticsinfobase.org/oe/abstract.cfm?uri=oe-16-26-21835.

Researchers are able to control every aspect of light generated by LEDs, allowing the light sources to be tweaked and optimized for nearly any situation, Schubert and Kim said. In general LEDs will require 20 times less power than today’s conventional light bulbs, and five times less power than “green” compact fluorescent bulbs.

If all of the world’s light bulbs were replaced with LEDs for a period of 10 years, Schubert and Kim estimate the following benefits would be realized:

 

  • Total energy consumption would be reduced by 1,929.84 joules
  • Electrical energy consumption would be reduced by terawatt hours
  • Financial savings of $1.83 trillion
  • Carbon dioxide emissions would be reduced by 10.68 gigatons
  • Crude oil consumption would be reduced by 962 million barrels
  • The number of required global power plants would be reduced by 280

 

With all of the promise and potential of LEDs, Schubert and Kim said it is important not to pigeonhole or dismiss smart lighting technology as a mere replacement for conventional light bulbs. The paper is a call to arms for scientists and engineers, and stresses that advances in photonics will position solid state lighting as a catalyst for unexpected, currently unimaginable technological advances.

“Deployed on a large scale, LEDs have the potential to tremendously reduce pollution, save energy, save financial resources, and add new and unprecedented functionalities to photonic devices. These factors make photonics what could be termed a benevolent tsunami, an irresistible wave, a solution to many global challenges currently faced by humanity and will be facing even more in the years to come,” the researchers wrote. “Transcending the replacement paradigm will open up a new chapter in photonics: Smart lighting sources that are controllable, tunable, intelligent, and communicative.”

Possible smart lighting applications include rapid biological cell identification, interactive roadways, boosting plant growth, and better supporting human circadian rhythms to reduce an individual’s dependency on sleep-inducing drugs or reduce the risk of certain types of cancer.

 

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In October, Rensselaer announced its new Smart Lighting Research Center, in partnership with Boston University and the University of New Mexico, and funded by an $18.5 million, five-year award from the NSF Generation Three Engineering Research Center Program. The three primary research thrusts of the center are developing novel materials, device technology, and systems applications to further the understanding and proliferation of smart lighting technologies.

For more information on the Smart Lighting Center, visit: smartlighting.rpi.edu.

To read the news release announcing the Smart Lighting Center, visit: http://news.rpi.edu/update.do?artcenterkey=2503.

December 17, 2008

LED lighting news

Filed under: Science — Tags: , , , — David Kirkpatrick @ 1:46 am

One of my favorite emerging technologies — LED lighting for the home.

The release:

The Green (and blue, red, and white) lights of the future

Special energy issue of Optics Express describes ‘coming revolution’ in LED lighting

WASHINGTON, Dec. 17– A revolution in energy-efficient, environmentally-sound, and powerfully-flexible lighting is coming to businesses and homes, according to a paper in latest special energy issue of Optics Express, the Optical Society’s (OSA) open-access journal.

The paper envisions the future of lighting — a future with widespread use of light emitting diodes (LEDs), which offer a number of obvious and subtle advantages over traditional light bulbs.

“We are at the verge of a revolution,” says the paper’s senior author E. Fred Schubert, a professor of electrical engineering and physics at Rensselaer Polytechnic Institute in Troy, NY. “There are tremendous opportunities that open up with LED lighting.”

LEDs are more rugged, resembling something closer to hard plastic than thin glass. They are also more environmentally sound, since their manufacture does not require toxic substances such as mercury.

As an alternative to the traditional incandescent light bulb, LED lights provide significant energy savings. They can be 2,000 percent more efficient than conventional light bulbs and 500 percent more efficient than compact fluorescent bulbs. Schubert predicts that widespread use of LEDs over the course of 10 years would save more than $1 trillion in energy costs, eliminate the need for nearly a billion barrels of oil over 10 years, and lead to a substantial reduction in emissions of carbon dioxide, the most common greenhouse gas.

All of these advantages make LEDs a good replacement light source, says Schubert, adding that this is why there has been a tremendous recent expansion of the LED industry, which is growing by double-digit rates. However, he adds, the true potential of LED lighting lies in their ability to transform — rather than simply replace — lighting technology.

“Replacement is fine,” says Schubert. “But we must look beyond the replacement paradigm to see the true benefits of LED lights.” Schubert envisions a day when light switches give way to light switchboards that control not only the brightness of a light, but its color temperature and hue. Light spectra could be custom-tailored for all wavelengths, accurately matching the sun’s light qualities and vary these characteristics according to the time of day, for instance. This could revolutionize indoor agriculture and help night-shift workers and people who are jet-lagged. The use of polarized light from LEDs could also improve computer displays and lower the glare from car headlights.

In his article, Schubert lays out how such future, “smart” light sources, can harness the huge potential of LEDs.

 

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Paper: “Transcending the Replacement Paradigm of Solid-State Lighting,” E. Fred Schubert and Jong Kyu Kim, Optics Express, Vol. 16, Issue 6, December 22, 2008, Focus Issue on Solar Energy edited by Alan Kost, University of Arizona.

About OSA
Uniting more than 70,000 professionals from 134 countries, the Optical Society (OSA) brings together the global optics community through its programs and initiatives. Since 1916 OSA has worked to advance the common interests of the field, providing educational resources to the scientists, engineers and business leaders who work in the field by promoting the science of light and the advanced technologies made possible by optics and photonics. OSA publications, events, technical groups and programs foster optics knowledge and scientific collaboration among all those with an interest in optics and photonics. For more information, visit www.osa.org.

December 8, 2008

Nanoscale magnetism

Earlier I did my first post on solar in quite a while. It seems more nanotech news is cropping up now.

At any rate here’s a pretty cool press release from today on detecting nanoscale magnetism.

The release:

New Hybrid Nanostructures Detect Nanoscale Magnetism

A scanning electron micrograph of cobalt nanoclusters embedded in multi-walled carbon nanotubes. Researchers at Rensselaer used these new hybrid structures, the first of their kind, to detect magnetism at the nanoscale.
Photo Credit: Saikat Talapatra/Caterina Soldano

Research could pave way for new data storage devices, drug delivery systems

A key challenge of nanotechnology research is investigating how different materials behave at lengths of merely one-billionth of a meter. When shrunk to such tiny sizes, many everyday materials exhibit interesting and potentially beneficial new properties.

Magnetic behavior is one such phenomenon that can change significantly depending on the size of the material. However, the sheer challenge of observing the magnetic properties of nanoscale material has impeded further study of the topic.

Researchers at Rensselaer Polytechnic Institute have developed and demonstrated a new method for detecting the magnetic behaviors of nanomaterials. They created a new process for creating a single multi-walled carbon nanotube that is embedded with cobalt nanostructures. The cobalt clusters measure from 1 nanometer to 10 nanometers. 

After a series of experiments, the research team has concluded that the electrical conductance of carbon nanotubes is sensitive enough to detect and be affected by trace amounts of magnetic activity, such as those present in the embedded cobalt nanostructures. It is believed to be the first instance of demonstrating the detection of magnetic fields of such small magnets using an individual carbon nanotube.

Results of the study were reported in the paper “Detection of Nanoscale Magnetic Activity Using a Single Carbon Nanotube” recently published by Nano Letters

“Since the cobalt clusters in our system are embedded inside the nanotube rather than on the surface, they do not cause electron scattering and thus do not seem to impact the attractive conductive properties of the host carbon nanotube,” said Swastik Kar, research assistant professor in Rensselaer’s Department of Physics, Applied Physics, & Astronomy, who led the project. “From a fundamental point of view, these hybrid nanostructures belong to a new class of magnetic materials.” 

“These novel hybrid nanostructures open up new avenues of research in fundamental and applied physics, and pave the way for increased functionality in carbon nanotube electronics utilizing the magnetic degree of freedom that could give rise to important spintronics applications,” said Saroj Nayak, an associate professor in Rensselaer’s Department of Department of Physics, Applied Physics, and Astronomy, who also contributed to the project. 

Potential applications for such a material include new generations of nanoscale conductance sensors, along with new advances in digital storage devices, spintronics, and selective drug delivery components.

Co-authors of the paper include Caterina Soldano, formerly a graduate student at Rensselaer who is now a postdoctoral research associate at the Centre d’Elaboration de Matériaux et d’Etudes Structurales in Tolouse, France; Professor Saikat Talapatra of the Physics Department of Southern Illinois University, Carbondale; and Prof. P.M. Ajayan of the Rice University Department of Mechanical Engineering and Materials Science.

Researchers received funding for the project from the New York State Interconnect Focus Center at Rensselaer.

Published December 8, 2008

March 14, 2008

Passing the Turing Test

From KurzweilAI.net:

AI researchers think ‘Rascals’ can pass Turing test
EE Times, Mar. 12, 2008Passing the Turing test–the holy grail of AI (a human conversing with a computer can’t tell it’s not human)–may now be possible in a limited way with the world’s fastest supercomputer (IBM‘s Blue Gene) and mimicking the behavior of a human-controlled avatar in a virtual world, according to AI experts at Rensselaer Polytechnic Institute.

“We are building a knowledge base that corresponds to all of the relevant background for our synthetic character–where he went to school, what his family is like, and so on,” said Selmer Bringsjord, head of Rensselaer’s Cognitive Science Department and leader of the research project.

“We want to engineer, from the start, a full-blown intelligent character and converse with him in an interactive environment like the holodeck from Star Trek.”
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