Making ceramic fuel cells with a 3-D printer would be a quick and easy way to manufacture the devices and could lead to new fuel cell designs that do a better job of converting a gas into electricity, according to researchers at Northwestern University.
The lab of Ramille Shah, assistant professor of materials science and engineering, has developed new inks that a single 3-D printer can use to create the individual components of the solid oxide fuel cell—cathode, anode, electrolyte, and interconnects. The inks are a mixture of ceramic particles that make up 70 to 90 percent of the mix, a binder, and a cocktail of solvents that evaporate at different rates. The ink for the electrolyte, for example, is made of yttrium-stabilized zirconia (YSZ) particles, while the anode is YSZ plus nickel oxide.
When the machine prints a line with one of these inks, a highly volatile solvent in the mix evaporates immediately, so the printed piece turns from a liquid to a solid instantly. The other solvents, however, evaporate more slowly, leaving the printed line hard enough to maintain its shape but soft enough that the next layer melds with it to form a single piece. The printing is done at room temperature, but just like when making a ceramic vase, the printed piece has to be fired at up to 1250° C to make it denser and smoother. To make sure the different parts of the printed fuel cell all shrink at the same rate during firing, the team tweaks the composition of the individual inks, and adds iron oxide in some layers.
“We can get really densely packed particles in the printed structure,” says Adam Jakus, a Ph.D. student in Shah’s lab, who described the work at the Materials Research Society’s fall meeting in Boston this week.
Using 3-D printing to build fuel cells of a standard design could be an easier manufacturing process than having to join the separate parts together, says Jakus. But, he says, the real promise could come from 3-D printing’s ability to create shapes that standard manufacturing processes can’t. For instance, they’ve printed flat sheets of the ceramic materials, which can be rolled or folded into different shapes before firing. Instead of the standard stack of fuel cells, they could be built in concentric circles, or be interwoven, creating more surface area and therefore easier transport of charge. Jakus, though, focuses on the inks, and will leave it up to colleagues who are experts in fuel cells to experiment with new designs.
Meanwhile, he’s developing similar inks for other uses, such as 3-D printed ceramic bone replacements that mimic the mechanical properties of actual bone. The team has also made an ink that allows 3-D printing of graphene.