(Press-News.org) What may be the ultimate heat sink is only possible because of yet another astounding capability of graphene. The one-atom-thick form of carbon can act as a go-between that allows vertically aligned carbon nanotubes to grow on nearly anything.
That includes diamonds. A diamond film/graphene/nanotube structure was one result of new research carried out by scientists at Rice University and the Honda Research Institute USA, reported today in Nature's online journal Scientific Reports.
The heart of the research is the revelation that when graphene is used as a middleman, surfaces considered unusable as substrates for carbon nanotube growth now have the potential to do so. Diamond happens to be a good example, according to Rice materials scientist Pulickel Ajayan and Honda chief scientist Avetik Harutyunyan.
Diamond conducts heat very well, five times better than copper. But its available surface area is very low. By its very nature, one-atom-thick graphene is all surface area. The same could be said of carbon nanotubes, which are basically rolled-up tubes of graphene. A vertically aligned forest of carbon nanotubes grown on diamond would disperse heat like a traditional heat sink, but with millions of fins. Such an ultrathin array could save space in small microprocessor-based devices.
"Further work along these lines could produce such structures as patterned nanotube arrays on diamond that could be utilized in electronic devices," Ajayan said. Graphene and metallic nanotubes are also highly conductive; in combination with metallic substrates, they may also have uses in advanced electronics, he said.
To test their ideas, the Honda team grew various types of graphene on copper foil by standard chemical vapor deposition. They then transferred the tiny graphene sheets to diamond, quartz and other metals for further study by the Rice team.
They found that only single-layer graphene worked well, and sheets with ripples or wrinkles worked best. The defects appeared to capture and hold the airborne iron-based catalyst particles from which the nanotubes grow. The researchers think graphene facilitates nanotube growth by keeping the catalyst particles from clumping.
Ajayan thinks the extreme thinness of graphene does the trick. In a previous study, the Rice lab found graphene shows materials coated with graphene can get wet, but the graphene provides protection against oxidation. "That might be one of the big things about graphene, that you can have a noninvasive coating that keeps the property of the substrate but adds value," he said. "Here it allows the catalytic activity but stops the catalyst from aggregating."
Testing found that the graphene layer remains intact between the nanotube forest and the diamond or other substrate. On a metallic substrate like copper, the entire hybrid is highly conductive.
Such seamless integration through the graphene interface would provide low-contact resistance between current collectors and the active materials of electrochemical cells, a remarkable step toward building high-power energy devices, said Rice research scientist and co-author Leela Mohana Reddy Arava.
###
Co-authors of the study are Honda senior scientists Rahul Rao and Gugang Chen; Rice graduate student Kaushik Kalaga; Masahiro Ishigami, an assistant professor of physics at the University of Central Florida; and Tony Heinz, the D.M. Rickey Professor of Physics at Columbia University. Ajayan is the Benjamin M. and Mary Greenwood Anderson Professor in Mechanical Engineering and Materials Science and of chemistry at Rice.
The research was supported by the Honda Research Institute.
Read the open-access paper at http://www.nature.com/srep/2013/130528/srep01891/full/srep01891.html
Follow Rice News and Media Relations via Twitter @RiceUNews
Related Materials:
Ajayan Group: http://www.owlnet.rice.edu/~rv4/Ajayan/
Honda Research Institute: http://www.honda-ri.com
Images for download:
http://news.rice.edu/wp-content/uploads/2013/05/0528_AJAYAN-1-web.jpg
Rice University and the Honda Research Institute use single-layer graphene to grow forests of nanotubes on virtually anything. The image shows freestanding carbon nanotubes on graphene that has been lifted off of a quartz substrate. One hybrid material created by the labs combines three allotropes of carbon – graphene, nanotubes and diamond – into a superior material for thermal management. (Credit: Honda Research Institute)
Located on a 300-acre forested campus in Houston, Rice University is consistently ranked among the nation's top 20 universities by U.S. News & World Report. Rice has highly respected schools of Architecture, Business, Continuing Studies, Engineering, Humanities, Music, Natural Sciences and Social Sciences and is home to the Baker Institute for Public Policy. With 3,708 undergraduates and 2,374 graduate students, Rice's undergraduate student-to-faculty ratio is 6-to-1. Its residential college system builds close-knit communities and lifelong friendships, just one reason why Rice has been ranked No. 1 for best quality of life multiple times by the Princeton Review and No. 2 for "best value" among private universities by Kiplinger's Personal Finance. To read "What they're saying about Rice," go to http://tinyurl.com/AboutRiceU.
END
Johns Hopkins scientists report that a 10-minute test for "frailty" first designed to predict whether the elderly can withstand surgery and other physical stress could be useful in assessing the increased risk of death and frequent hospitalization among kidney dialysis patients of any age.
In a study described in the Journal of the American Geriatrics Society and published online yesterday, the Johns Hopkins investigators said dialysis patients deemed frail by the simple assessment were more than twice as likely to die within three years, and much more likely to be hospitalized ...
WASHINGTON — Disabled Medicare patients under the age of 65 who don't take their prescription medications because of cost concerns are more likely to have at least one emergency department visit during a one-year period. The results of a new study are published online today in Annals of Emergency Medicine ("The Relationship Between Emergency Department Use and Cost-Related Medication Nonadherence Among Medicare Beneficiaries").
"Poverty and disability increase the risk that patients don't take their medicine because of the cost, which can lead to avoidable hospitalizations," ...
Given the chance, women are more likely than men to dodge an opportunity to donate to charity, a group of economists have found.
The issue of which gender is more generous has been debated for years. A new field experiment conducted by scholars at the University of Chicago and University of California, Berkeley shows that when it's easy to avoid making a donation, such as not responding to a door-to-door solicitor, women are less likely than men to give.
The results of the study are published in the article, "The Importance of Being Marginal: Gender Differences in Generosity," ...
UCLA researchers now have the first evidence that bacteria ingested in food can affect brain function in humans. In an early proof-of-concept study of healthy women, they found that women who regularly consumed beneficial bacteria known as probiotics through yogurt showed altered brain function, both while in a resting state and in response to an emotion-recognition task.
The study, conducted by scientists with UCLA's Gail and Gerald Oppenheimer Family Center for Neurobiology of Stress and the Ahmanson–Lovelace Brain Mapping Center at UCLA, appears in the June edition ...
Hurricane Sandy caught the public and policymakers off guard when it hit the United States' Atlantic Coast last fall. Because much of the storm's devastation was wrought by flooding in the aftermath, researchers have been paying attention to how climate change and sea-level rise may have played a role in the disaster and how those factors may impact the shoreline in the future.
A new study led by the University of Pennsylvania's Benjamin P. Horton, an associate professor in the Department of Earth and Environmental Science, relied upon fossil records of marshland to reconstruct ...
PORTLAND, Ore. — For several years, the pharmaceutical industry has tried to develop drugs that target a specific neurotransmitter receptor in the brain, the NMDA receptor. This receptor is present on almost every neuron in the human brain and is involved in learning and memory. NMDA receptors also have been implicated in several neurological and psychiatric conditions such as Alzheimer's disease, Parkinson's disease, schizophrenia and depression.
But drug companies have had little success developing clinically effective drugs that target this receptor.
Now, researchers ...
Mexican American mothers' formal immigration status affects the educational achievement of their children and even their grandchildren, according to a study written by Penn State and University of California, Irvine, sociologists and released by the US2010 Project at Brown University.
Based on a large-scale survey of second-generation Mexican young adults in Los Angeles, the study finds that those whose mothers were authorized immigrants or U.S. citizens averaged more than two years more schooling than those whose mothers entered the country illegally. The researchers ...
Older Texans embracing divorce in greater numbers
Article provided by Law Office of Nancy H. Boler
Visit us at http://www.bolerlaw.com
According to a study entitled, "The Gray Divorce Revolution," divorce among older adults in the United States has doubled since the new millennium began. This is at a higher rate than predicted and the new trend, referred to as gray divorce, is expected to continue increasing.
In Texas, legal professionals are seeing a rise in the number of older people going through divorce as well. Experts in law and psychology offer ...
North Carolina home heating fire injures one
Article provided by Warren & Kallianos - Injury Lawyers
Visit us at http://www.burninjurieslaw.com
In a recent frightening incident, a High Point, North Carolina man was injured in a boarding house fire. The fire, which apparently affected only the man's unit in the building, was reported to the fire department around 2:30 A.M.
A fire department spokesperson stated that flammable materials were ignited by a space heater, starting the fire that caused the injuries.
Home heating fires happen all too often
According ...
Altaaqa Global CAT Rental Power, a leading global power solutions provider, recently designed and installed a 24MW temporary power plant in the Sultanate of Oman.
To meet electricity demands throughout the summer, the 24MW temporary rental power plant will supply power to the electricity grid at a time when there is a significant increase in the use of temperature control equipment, such as air conditioning and district cooling. Supporting the existing generating capacity of Oman, the interim power plant will ensure peak performance during the hottest months of the ...
