An international team of scientists has created carbon nanolattices — constructed from closed-cell plate-architectures — that are stronger than diamonds as a ratio of strength to density.
With wall thicknesses of about 160 nm, a closed-cell, plate-based nanolattice structure is the first experimental verification that such arrangements reach the theorized limits of strength and stiffness in porous materials. Image credit: Cameron Crook & Jens Bauer, University of California, Irvine.
“Scientists have predicted that nanolattices arranged in a plate-based design would be incredibly strong,” said first author Cameron Crook, a graduate student at the University of California, Irvine.
“But the difficulty in manufacturing structures this way meant that the theory was never proven, until we succeeded in doing it.”
The team’s achievement rests on a complex 3D laser printing process called two-photon lithography direct laser writing.
As an UV-sensitive resin is added layer by layer, the material becomes a solid polymer at points where two photons meet.
The technique is able to render repeating cells that become plates with faces as thin as 160 nm.
One of the team’s innovations was to include tiny holes in the plates that could be used to remove excess resin from the finished material.
As a final step, the lattices go through pyrolysis, in which they’re heated to 900 degrees Celsius (1,652 degrees Fahremheit) in a vacuum for one hour.
The result is a cube-shaped lattice of glassy carbon that has the highest strength scientists ever thought possible for such a porous material.
“Another goal and accomplishment of the study was to exploit the innate mechanical effects of the base substances,” said leadauthor Dr. Jens Bauer, also from the University of California, Irvine.
“As you take any piece of material and dramatically decrease its size down to 100 nm, it approaches a theoretical crystal with no pores or cracks.”
“Reducing these flaws increases the system’s overall strength.”
“Nobody has ever made these structures independent from scale before,” said University of California, Irvine’s Professor Lorenzo Valdevit, co-author of the study.
“We were the first group to experimentally validate that they could perform as well as predicted while also demonstrating an architected material of unprecedented mechanical strength.”
The team’s paper was published March 27, 2020 in the journal Nature Communications.
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C. Crook et al. 2020. Plate-nanolattices at the theoretical limit of stiffness and strength. Nat Commun 11, 1579; doi: 10.1038/s41467-020-15434-2
