Chris Masi
Glass vial in microwave

Turning Coal Powder into Nano-Graphite—with a Microwave Oven

Jan. 8, 2021
This demonstration could lead to a low-cost source of nanoparticles of graphite and other materials.

Researchers at the University of Wyoming were looking for new ways to use coal, especially coal from Wyoming’s Powder River Basin, as demand for the coal to generate electricity declines due to concerns about emissions. They might have recently succeeded when they demonstrated that copper foil, glass containers and a conventional household microwave oven could convert pulverized coal powder into higher-value nano-graphite. Graphite is currently used as a lubricant and in items ranging from fire extinguishers to lithium-ion batteries, but that could expand if its price came down and its availability improved.

Previous research proved microwaves can reduce the moisture content of coal and remove sulfur and other minerals, but the methods require chemically pretreating the coal. In their experiment, the UW researchers simply ground raw Powder River Basin coal into powder.

That powder was placed on copper foil and sealed in glass containers with a mix of argon and hydrogen gas. It was then placed in a conventional microwave since it was convenient and provided the necessary desired levels of radiation.

The copper foil was cut into a fork shape, and the sparks it generated when the oven was turned on generated a temperature in excess of 1,800°F within a few seconds. These temperatures, combined with the copper and hydrogen, were enough to turn the coal powder into polycrystalline graphite.

The researchers say their new method of making graphite could be developed and scaled up to yield both a higher quality and quantity of nano-graphite materials.

Finite graphite reserves and environmental concerns for the way graphite is mined make this metal-assisted microwave process a great inexpensive alternative source of graphite, according to the team.

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