Nano-graphite is an important material employed in lubricants, fire extinguishers, and lithium batteries as graphite is a good conductor of heat and electricity. However, graphite reserves are finite and extraction of this mineral comes with hefty environmental concerns. Now, researchers have found a cheap and easy way to produce it. You just need some copper foil, a glass container full of coal powder, and a conventional microwave oven.
Detailed in the journal Nano-Structures & Nano-Objects, pulverized coal is sealed in a container with a mixture of hydrogen and argon and some aptly cut copper foil. This is then placed in a microwave. If you've ever made the mistake of putting something metallic in a microwave before, you know what happens next: sparks!
“By cutting the copper foil into a fork shape, the sparks were induced by the microwave radiation, generating an extremely high temperature of more than 1,800 degrees Fahrenheit within a few seconds,” lead author Christoffer Masi from the University of Wyoming said in a statement. “This is why you shouldn’t place a metal fork inside a microwave oven,” he added.
When the coal powder was exposed to those 980°C (1,800°F) sparks, the temperature was high enough to turn it into polycrystalline graphite. The hydrogen also helps in the process. The team tested this approach with times ranging between 3-45 minutes. The optimal duration for the process was found to be around 15 minutes.
This may sound a bit like scientists playing around with equipment they have lying around at home but it could actually have some important real-world applications. “This method provides a new route to convert abundant carbon sources to high-value materials with ecological and economic benefits,” the team wrote in the study. “Finite graphite reserves and environmental concerns for the graphite extraction procedures make this method of converting coal to graphite a great alternative source of graphite production.”
This is not the first time that coal has been refined using microwave technology. Previous approaches saw the reduction of moisture or the removal of certain minerals such as sulfur also achieved by employing microwave ovens. The drawback in those methods is the requirement that the coal undergoes particular chemical pre-treatment for the reactions to take place, which is not needed with this new technique.
The researchers believe that this technology can be scaled up and the material involved changed, with the goal of improving on the quality and yield of the nano-graphite produced.
“The small thermal load makes this method cost-effective and has potential for higher temperature using metals with higher melting temperature,” the authors write. “Refinement of this technique is possible to yield a higher quality and quantity of nano-graphite materials for a wider range of applications.”