Researchers at Rice University and China's Tianjin University have used 3D laser printing to fabricate centimeter-sized graphene objects. The team has demonstrated the making of graphene foams from non-graphene starting materials, in a method that could reportedly be scaled for additive manufacturing applications with pore-size control. The process is conducted at room temperature, without the need for molds. The rather unusual starting materials are powdered sugar and nickel powder.

Rice U team 3D prints graphene using lasers image

3D laser printers work differently than the more familiar extrusion-based 3D printers, which create objects by squeezing melted plastic through a needle as they trace out two-dimensional patterns. In 3D laser sintering, a laser shines down onto a flat bed of powder. Wherever the laser touches powder, it melts or sinters the powder into a solid form. The laser is rastered, or moved back and forth, line by line to create a single two-dimensional slice of a larger object. Then a new layer of powder is laid over the top of that layer and the process is repeated to build up three-dimensional objects from successive two-dimensional layers.

The new Rice process used a commercially available CO2 laser. When this laser was directed at the sugar and nickel powder, the sugar was melted and the nickel acted as a catalyst. Graphene formed as the mixture cooled after the laser had moved on to melt sugar in the next spot, and the team conducted a study to find the optimal amount of time and laser power to maximize graphene production.

The foam created by the process is a low-density, 3D form of graphene with large pores that account for more than 99% of its volume.

"This simple and efficient method does away with the need for both cold-press molds and high-temperature CVD treatment," said co-lead author Junwei Sha, a former student in Tour's lab who is now a postdoctoral researcher at Tianjin. "We should also be able to use this process to produce specific types of graphene foam like 3D printed rebar graphene as well as both nitrogen- and sulfur-doped graphene foam by changing the precursor powders."

Versarien - Think you know graphene? Think again! Versarien - Think you know graphene? Think again!