Researchers at Rice University have developed a way to turn carbon from a variety of sources straight into useful forms such as graphene or diamond. The technique uses a “flash” of electricity to heat the carbon, converting it into a final form that’s determined by the length of the flash.
The technique is known as flash joule heating (FJH), and the team first described it in January 2020. An electrical current is passed through carbon-containing materials, heating them to about 2,727 °C (4,940 °F), which converts the carbon into pristine, turbostratic graphene flakes.
Now the researchers have refined the process to create other materials. The original flashes lasted 10 milliseconds, but the team found that by changing the duration between 10 and 500 milliseconds they could also guide the carbon to convert into other forms, too. That includes nanodiamond, and “concentric carbon” where carbon atoms form a shell around a nanodiamond core.
To help the process along, organic fluorine compounds and precursors are now added to the mix at the beginning. Previous studies have shown that fluorine helps carbon atoms stick together more strongly, allowing the nanodiamonds to be made under gentler conditions – normally it would take very high pressures.
The team says that the new FJH process can help produce these new forms in bulk, which is traditionally tricky to do. That includes fluorinated nanodiamonds, which are more useful in electronic components such as semiconductors but normally need to undergo a separate doping process.
“In industry, there has been a long-standing use for small diamonds in cutting tools and as electrical insulators,” says James Tour, lead researcher on the study. “The fluorinated version here provides a route to modifications of these structures. And there is a large demand for graphene, while the fluorinated family is newly produced here in bulk form. The concentric-shelled structures have been used as lubricant additives, and this flash method might provide an inexpensive and fast route to these formations.”
The team says that the next steps are to experiment with using other additives such as boron, phosphorus and nitrogen.
The research was published in the journal ACS Nano.
Source: Rice University