Graphene Gets Practical
It turns out graphene is not just for high-tech applications, but for the simple devices we use everyday like our light bulbs.
When applications for graphene are proposed, we typically hear about some gee-whiz technology, like the next generation of electronics or optoelectronics. It’s rare that we hear about how graphene could play a role in the more mundane technologies of our lives, like our light bulbs or our home heating systems.
However, in this last quarter we have seen a fair number of applications for graphene that could broadly fall under the title of practical uses.
Graphene Coating Shines for LED Lighting Fixtures
Photo: University of Manchester
One such application that made a big splash, especially in the UK, was news that a graphene-coated light bulb was to be the “first commercially viable consumer product” using graphene.
Aside from the obvious inaccuracies of such a claim, since there are products currently on the market using graphene, such as Head’s graphene-based tennis racquets, the coating of an LED light bulb did seem like a peculiar choice for using graphene.
It was not immediately apparent from the news reports on the graphene-based light bulb what the potential benefits could be from coating a solid-state device like an LED light bulb with graphene. Without providing much in the way of details, Dan Cochlin, the graphene communications manager for the University of Manchester, where the basic technology was developed, explained that the graphene coating takes heat away from the LED components, which would reduce energy use and increase the LED bulb’s lifetime.
This could explain the head-scratching economics of the LEDs. The graphene-coated light bulbs are supposed to be priced lower than some LEDs, which can cost approximately US$20 a piece, despite them requiring the additional processing step of the coating.
If the graphene coating can improve the heat management of the LEDs, this could reduce the need for a larger and more expensive heat sink. So, while the LED bulb itself may be more expensive to produce, its improved thermal properties could reduce the total package costs.
Graphene Comes to Home Heating Systems
A UK-based startup called Xefro has turned to a graphene-based ink coating to provide the final piece of the puzzle to their novel heating system.
Xefro had developed a smart control system that could automatically control an electric heater based on the current conditions in the room and your personal heating habits. What they wanted was a material that could coat the heater elements and enable the heater element to be turned on and off quickly and wouldn’t waste energy in heating up.
While a number of carbon-based ink coatings could have been used, the company decided to use graphene. Since graphene is all surface area, it provided a small thermal mass so that the heat could be turned on and off quickly and no energy would be wasted in heating up the heater itself.
Xefro believed that the graphene-based coating offered some advantages over other coatings they could have used, especially when used in combination with its novel control system in which the speed at which the heat could be turned off and back on again was critical to the system’s efficiency.
The company has claimed that depending on the heating system a customer is currently using, its system can reduce energy costs anywhere from 25 to 70 percent.
The systems will become available in July 2015 through Xefro’s distributors in the UK.
Graphene Composites That Deserve the Name
For the most part, the nanomaterial composites that have been marketed over the last decade are not much different from run of the mill polymer composites. From tennis racquets to high-end bicycles, nanomaterials have been used as the resins in composites.
Basically, resins are used in composite materials to serve as a kind of binder to keep everything stuck together. For a long time it was unclear whether an expensive resin like a carbon nanotube imparted much benefit over inexpensive carbon black, such as improving the composites strength and flexibility.
In fact, this question mark came to be known in the composites industry as the “Valley of Death” in composite material design. Then about four years ago some researchers found a way to actually overcome this by using carbon nanotubes as reinforcements in composites rather than just as resins. In this way, some of the attractive properties of the nanomaterial were actually part of the properties of the composite material. In this case, the composite had electrical conductivity.
Then just two years ago, researchers at the University of Western Australia found a way for composite materials to actually match the strength and flexibility of nanowires that had been added to the composite mix.
The resulting composite has proved to be twice as strong as high-strength steels and it enjoys elastic strain limits that are 5 to 10 times greater than the best spring steels currently available.
While the attractive properties of carbon nanotubes and nanowires were now being imparted into the composites that they were part of, graphene was still not having its qualities fully manifested in the composites.
Recently, researchers at Oak Ridge National Laboratory have produced composites made up of plastic and 5-centimeter-by-5-cm sheets of graphene that have the mechanical and electrical capabilities that the researchers were expecting.
The key to the research was the large size of the graphene sheets. Previously, it was only possible to add tiny flakes of graphene into the composites. This meant that there were often large gaps between the small graphene pieces and any strength or flexibility they might have had was lost in the matrix of the composite.
The Oak Ridge researchers employed chemical vapor deposition (CVD) to produce their large sheets of graphene. These large graphene sheets eliminated the clumping of graphene flakes in the composites and required 50 time less graphene in the composite.
This large-scale fabrication of a graphene-based composite that actually imparts the attractive properties of graphene, such as its strength and electrical and thermal conductivity, could open a range of applications that would benefit from having these properties.