Wyoming University scientists have demonstrated an inexpensive technology for converting pulverized coal powder into higher-value nano-graphite.
All they needed for doing this were copper foil, glass containers and a conventional household microwave oven. They contend that this discovery is another step forward in the effort to find alternative uses for Wyoming’s Powder River Basin coal, especially with climate change taking center stage.
Nano-graphite is used as a lubricant and in items ranging from fire extinguishers to lithium ion batteries. Creating this is however can be a really costly affair.
This is why team lead and associate professor TeYu Chien opines that their ‘one-step method with metal-assisted microwave treatment’ is a game changer as it provides a new route to convert abundant carbon sources to high-value materials with ecological and economic benefits.
While previous research has shown that microwaves can be used to reduce the moisture content of coal and remove sulfur and other minerals, such methods require specific chemical pre-treatment of the coal.
For their study, the UW team simply ground raw Powder River Basin coal into powder.
That powder was then placed on copper foil and sealed in glass containers with a gas mixture of argon and hydrogen, before being placed in a microwave oven.
A conventional microwave oven was chosen because of convenience and because it provided the desired levels of radiation.
“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,” notes lead author Chris Masi.
“This is why you shouldn’t place a metal fork inside a microwave oven.”
The sparks caused by the microwaves generated the high temperatures necessary to transform the coal powder into polycrystalline graphite, with the copper foil and hydrogen gas also contributing to the process.
The scientists contend that this new method can be further refined and performed at a larger scale to yield both a higher quality and quantity of nano-graphite materials.
Image and content: University of Wyoming