25 Jan 2016
Rice University scientists embedded graphene nanoribbon-infused epoxy in a section of helicopter blade to test its ability to remove ice through Joule heating. Credit: Tour Group/Rice University
A thin coating of graphene nanoribbons in epoxy developed at Rice University has proven effective at melting ice on a helicopter blade.
The coating by the Rice lab of chemist James Tour may be an effective real-time de-icer for aircraft, wind turbines, transmission lines and other surfaces exposed to winter weather, according to a new paper in the American Chemical Society journal ACS Applied Materials and Interfaces.
In tests, the lab melted centimeter-thick ice from a static helicopter rotor blade in a minus-4-degree Fahrenheit environment. When a small voltage was applied, the coating delivered electrothermal heat – called Joule heating – to the surface, which melted the ice.
The nanoribbons produced commercially by unzipping nanotubes, a process also invented at Rice, are highly conductive. Rather than trying to produce large sheets of expensive graphene, the lab determined years ago that nanoribbons in composites would interconnect and conduct electricity across the material with much lower loadings than traditionally needed.
Previous experiments showed how the nanoribbons in films could be used to de-ice radar domes and even glass, since the films can be transparent to the eye.
“Applying this composite to wings could save time and money at airports where the glycol-based chemicals now used to de-ice aircraft are also an environmental concern,” Tour said.
In Rice’s lab tests, nanoribbons were no more than 5 percent of the composite. The researchers led by Rice graduate student Abdul-Rahman Raji spread a thin coat of the composite on a segment of rotor blade supplied by a helicopter manufacturer; they then replaced the thermally conductive nickel abrasion sleeve used as a leading edge on rotor blades. They were able to heat the composite to more than 200 degrees Fahrenheit.
For wings or blades in motion, the thin layer of water that forms first between the heated composite and the surface should be enough to loosen ice and allow it to fall off without having to melt completely, Tour said.
The lab reported that the composite remained robust in temperatures up to nearly 600 degrees Fahrenheit.
As a bonus, Tour said, the coating may also help protect aircraft from lightning strikes and provide an extra layer of electromagnetic shielding.
Explore further: Researchers create sub-10-nanometer graphene nanoribbon patterns
More information: Abdul-Rahman O. Raji et al. Composites of Graphene Nanoribbon Stacks and Epoxy for Joule Heating and Deicing of Surfaces, ACS Applied Materials & Interfaces (2016). DOI: 10.1021/acsami.5b11131
|EPFL scientists have developed a solar-panel material that can cut down on photovoltaic costs while achieving competitive power-conversion efficiency of 20.2%.|
|Some of the most promising solar cells today use light-harvesting films made from perovskites – a group of materials that share a characteristic molecular structure. However, perovskite-based solar cells use expensive “hole-transporting” materials, whose function is to move the positive charges that are generated when light hits the perovskite film. Publishing in Nature Energy (“A molecularly engineered hole-transporting material for e cient perovskite solar cells”), EPFL scientists have now engineered a considerably cheaper hole-transporting material that costs only a fifth of existing ones while keeping the efficiency of the solar cell above 20%.|
|This is a 3-D illustration of FDT molecules on a surface of perovskite crystals. (Image: Sven M. Hein / EPFL)|
|As the quality of perovskite films increases, researchers are seeking other ways of improving the overall performance of solar cells. Inadvertently, this search targets the other key element of a solar panel, the hole-transporting layer, and specifically, the materials that make them up. There are currently only two hole-transporting materials available for perovskite-based solar cells. Both types are quite costly to synthesize, adding to the overall expense of the solar cell.|
|To address this problem, a team of researchers led by Mohammad Nazeeruddin at EPFL developed a molecularly engineered hole-transporting material, called FDT, that can bring costs down while keeping efficiency up to competitive levels. Tests showed that the efficiency of FDT rose to 20.2% – higher than the other two, more expensive alternatives. And because FDT can be easily modified, it acts as a blueprint for an entire generation of new low-cost hole-transporting materials.|
|“The best performing perovskite solar cells use hole transporting materials, which are difficult to make and purify, and are prohibitively expensive, costing over €300 per gram preventing market penetration,” says Nazeeruddin. “By comparison, FDT is easy to synthesize and purify, and its cost is estimated to be a fifth of that for existing materials – while matching, and even surpassing their performance.”|
|Source: Ecole Polytechnique Fédérale de Lausanne|
Gold nanoparticles have unusual optical, electronic and chemical properties, which scientists are seeking to put to use in a range of new technologies, from nanoelectronics to cancer treatments.
Some of the most interesting properties of nanoparticles emerge when they are brought close together — either in clusters of just a few particles or in crystals made up of millions of them. Yet particles that are just millionths of an inch in size are too small to be manipulated by conventional lab tools, so a major challenge has been finding ways to assemble these bits of gold while controlling the three-dimensional shape of their arrangement.
One approach that researchers have developed has been to use tiny structures made from synthetic strands of DNA to help organize nanoparticles. Since DNA strands are programmed to pair with other strands in certain patterns, scientists have attached individual strands of DNA to gold particle surfaces to create a variety of assemblies. But these hybrid gold-DNA nanostructures are intricate and expensive to generate, limiting their potential for use in practical materials. The process is similar, in a sense, to producing books by hand.
Enter the nanoparticle equivalent of the printing press. It’s efficient, re-usable and carries more information than previously possible. In results reported online in Nature Chemistry, researchers from McGill’s Department of Chemistry outline a procedure for making a DNA structure with a specific pattern of strands coming out of it; at the end of each strand is a chemical “sticky patch.” When a gold nanoparticle is brought into contact to the DNA nanostructure, it sticks to the patches. The scientists then dissolve the assembly in distilled water, separating the DNA nanostructure into its component strands and leaving behind the DNA imprint on the gold nanoparticle.
“These encoded gold nanoparticles are unprecedented in their information content,” says senior author Hanadi Sleiman, who holds the Canada Research Chair in DNA Nanoscience. “The DNA nanostructures, for their part, can be re-used, much like stamps in an old printing press.”
From stained glass to optoelectronics
Some of the properties of gold nanoparticles have been recognized for centuries. Medieval artisans added gold chloride to molten glass to create the ruby-red colour in stained-glass windows — the result, as chemists figured out much later, of the light-scattering properties of tiny gold particles.
Now, the McGill researchers hope their new production technique will help pave the way for use of DNA-encoded nanoparticles in a range of cutting-edge technologies. First author Thomas Edwardson says the next step for the lab will be to investigate the properties of structures made from these new building blocks. “In much the same way that atoms combine to form complex molecules, patterned DNA gold particles can connect to neighbouring particles to form well-defined nanoparticle assemblies.”
These could be put to use in areas including optoelectronic nanodevices and biomedical sciences, the researchers say. The patterns of DNA strands could, for example, be engineered to target specific proteins on cancer cells, and thus serve to detect cancer or to selectively destroy cancer cells.
Financial support for the research was provided by the Natural Sciences and Engineering Research Council of Canada, the Canada Foundation for Innovation, the Centre for Self-Assembled Chemical Structures, the Canada Research Chairs Program and the Canadian Institutes of Health Research.
- Thomas G. W. Edwardson, Kai Lin Lau, Danny Bousmail, Christopher J. Serpell, Hanadi F. Sleiman. Transfer of molecular recognition information from DNA nanostructures to gold nanoparticles. Nature Chemistry, 2016; DOI: 10.1038/nchem.2420
This article is published in collaboration with Medium.
The eighteenth century’s cotton looms and steam engines overturned the way the world worked in the first industrial revolution. Then came mass production, with the efficient factories of the early twentieth century changing the nature of labour. Then the computer age, as PCs gradually shrank from the size of a room to something that would fit in the palm of your hand.
And now we’re in the middle of the most profound and fast-moving economic shift of them all. Man and machine are converging, digitisation is disrupting everything, new technologies are emerging more quickly than we can imagine them, let alone think up the rules to govern their use. This is the Fourth Industrial Revolution, a new era where we will be able to 3D-print both livers and guns.
Mastering the Fourth Industrial Revolution is the theme of the World Economic Forum’s Annual Meeting 2016 in Davos. Before we can master it, we need to define it.
Here, Professor Klaus Schwab, Founder and Executive Chairman at the World Economic Forum, explains how this revolution differs from others in its speed, breadth and impact.
What does this change mean to you? Can you provide a concrete example of how the Fourth Industrial Revolution will play out in your community, your industry, or even in your family? What should we do to manage its risks and reap its rewards?
We are inviting essay submissions of up to 900 words on the theme of the Fourth Industrial Revolution. A shortlist of five essays will be published on the World Economic Forum’s Agenda blog platform, which is read by 1.5 million people a month. The winning essay will be shared with delegates at Davos and promoted across our social media channels during the meeting, while the winner will receive a signed copy of Professor Klaus Schwab’s book.
If you would like to enter, please follow these steps:
1. Publish your essay on Medium
2. Tag your essay “Davos essay contest”
3. Email the link to firstname.lastname@example.org
4. The deadline for submissions is December 31st. The shortlist will be announced on Medium and Forum Agenda on January 11th, and the winner on January 18th.
5. The contest is for members of the public. World Economic Forum staff and constituents are not eligible.
Publication does not imply endorsement of views by the World Economic Forum.
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Author: Ceri Parker is Commissioning Editor at the World Economic Forum.