Rice University scientists have shown how a thin shell of soft polymer can help keep knotty ceramic structures like schwarzites from shattering.
According to the team from Rice’s Brown School of Engineering, ceramics made with 3D printers crack under stress like any plate or bowl. But covering these in a soft polymer cured under ultraviolet light could help their structural integrity intact, just like how a car windshield’s treated glass is less likely to shatter.
The scientists demonstrated the concept on schwarzites, complex lattices that for decades existed only as theory but can now be made with 3D printers.
Named after German scientist Hermann Schwarz, schwarzites were first hypothesized in the 1880s as ‘negatively curved’ structures that could be used wherever very strong but lightweight materials were needed.
Now thanks to 3D printing and added polymers, schwarzites have come to resemble structures found in nature like seashells and bones that consist of hardened platelets in a biopolymer matrix.
In this latest research, Rice materials scientists Pulickel Ajayan and Muhammad Rahman – and graduate student and lead author Seyed Mohammad Sajadi – have shown how a coating of polymer no more than 100 microns thick can help make fragile schwarzites up to 4.5 times more resistant to catastrophic fractures.
It should be noted that the structures aren’t completely crack resistant under pressure, but the good thing is they don’t fall apart and remain enclosed like laminated glass.
Apart from Ajayan, Rahman and Sajadi, the team also includes scientists from Hungary, Canada and India.
These members were instrumental in creating computer models of the structures and printing them with a polymer-infused ceramic ink.
The ceramic was cured on the fly by ultraviolet lights in the printer, later dipped in polymer, and then cured again.
Once this was done, the intricate blocks – along with uncoated control units – were subjected to high pressure tests.
Results show that the control schwarzites shattered as expected, but the polymer coating prevented cracks from propagating in the others, allowing the structures to keep their form.
The researchers also compared the schwarzites to coated solid ceramics and found the porous structures were inherently tougher, attributing this to the material’s architecture.
Image and content: Rice University