Dry ice once gained notoriety as a fog enabler at innumerable 1970’s discotheques, and now it is being revived to hustle a 21st century breakthrough material out of the lab and into commercial use. Researchers from South Korea and Case Western Reserve University are developing a way to manufacture large quantities of graphene based on little more than dry ice and a canister filled with stainless steel balls.
What graphene means for a sustainable future
Graphene’s unique electrical properties combined with its incredible strength (though only one atom thick, a sheet of graphene is 200 times stronger than steel) could lead to smaller, lighter, cheaper, more energy efficient and more powerful electronic devices for the consumer market. Graphene could also give rise to a new generation of electronic devices altogether, with applications for science, medicine, industry and of course, warfare.
Since the words “light” “strong” and “electronic” are usually good for attracting the attention of the U.S. Air Force, it’s no surprise that the Air Force Office of Scientific Research is among the funders of the new research.
So close, and yet so far
Graphene has made waves in the research community since first discovered in 2004, but its tantalizing future has been out of reach because it is extremely difficult to mass produce.
Early research was conducted on graphene sheets that were literally lifted from chunks of graphite with sticky tape, and there are a number of ways to generate flakes of graphene, but researchers are still trying to figure out how to produce it in usable forms with predictable behaviors, at a commercially viable price.
The current method of choice is based on acid oxidation, which is a “tedious,” expensive process that requires toxic chemicals according to the Korea/Case Western research co-author Liming Dai, a professor of macromolecular science and engineering at Case.
Using dry ice to make a better graphene flake
The Korea/Case team is doing a workaround on the production problem by generating graphene flakes that can be bonded seamlessly together. The flakes are prepped using a low cost process without the toxic chemicals.
As described by Case Western blogger Kevin Mayhood:
“Researchers placed graphite and frozen carbon dioxide [dry ice] in a ball miller, which is a canister filled with stainless steel balls. The canister was turned for two days and the mechanical force produced flakes of graphite with edges essentially opened up to chemical interaction by carboxylic acid formed during the milling.”
When the flakes are soaked in a solvent, they separate into sheets of graphene up to five layers thick. That’s not quite the one-atom scale of pure graphene, but it is still incredibly thin: in comparison, it would take three million layers to make a flake one millimeter thick.
Yep, it’s a better graphene flake
The thin sheets of graphene can be pressed into pellets that conduct electricity 688 times better than pellets made from graphene produced by acid oxidation, according to the Korea/Case team.
The team also demonstrated that their graphene pellets could withstand extremely high temperatures (900 degrees Celsius) for a longer period of time than conventional acid oxidation based pellets.
Creating usable graphene pellets in the lab through a low cost, reliable process is a first step to demonstrating that graphene could be fabricated in molded shapes for commercial use. In addition to molding, the team also demonstrated that their graphene flakes can be deposited on silicon wafers to form thin films with a large surface area.
The U.S. Air Force hearts graphene
As for the Air Force, in an article last September Dr. John Boeckl, a materials and manufacturing expert with the Air Force Research Laboratory, described how graphene could “totally transform technologies:”
“Researchers predict that graphene will be as transformative as the television, atomic bomb, and silicon chip. It has the potential for enormous impact on Air Force capabilities, such as enabling band-hopping radar and leading to radio frequency semiconductors that are 100 times faster than the current state-of-the-art. Graphene may lead to the production of lighter aircraft and satellites, and may be used in sensors, electric batteries, transparent conductive coatings for solar cells, and in a variety of other applications.”
The Air Force has also been funding graphene fabrication research at Columbia University through an interdisciplinary project involving Columbia Engineering, the Graduate School of Arts and Sciences, and Cornell University. Earlier this month the Air Force extended its involvement for another two years with an additional grant of $3 million.
Rice University is another hotbed of graphene research that has been fueled with Air Force funding. Last January a team of researchers at Rice announced that they have developed a method for transforming graphene’s relatively simple chickenwire structure into a complex “superlattice” that could be tailored for use in applications based on organic chemistry, as well as electronics, optics, thermoelectric devices and sensors.
“The beauty of this process is the promise it holds for future devices with the ability to efficiently accomplish a wide variety of highly sophisticated functions in one small affordable device,” enthused Dr. Robert White of the Air Force Office of Scientific Research in an article describing the research.
Dr. White is not alone among his Air Force colleagues in his somewhat poetic advocacy for graphene. In a presentation on graphene developed last year, Lt. Col. Scott Dudley, the Air Force physics program manager who is responsible for finding and funding basic research, evoked the Rolling Stones, Elton John and Pink Floyd to make the case for a graphene-based future.
Follow Tina Casey on Twitter: @TinaMCasey.
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