A team of scientists at the Karlsruhe Institute of Technology, Germany, has created a glassy carbon nanolattice with single struts shorter than 1 μm and diameters as small as 200 nm — the smallest lattice structure yet produced.
The world’s smallest lattice is visible under the microscope only, according to the team, led by Dr. Jens Bauer.
“The smallest stable lattice structure presented now was produced by the established 3D laser lithography process at first,” said Dr. Bauer, who is the lead author of a paper published online yesterday in the journal Nature Materials.
For their experiments, Dr. Bauer and his colleagues manufactured three differently sized lattices with tetrahedral unit cells with edge or strut lengths of 10, 7.5 and 5 µm.
In the subsequent pyrolysis step, these polymeric microlattices were converted into carbon nanostructures in a furnace.
“The objects were exposed to temperatures of around 1,650 degrees Fahrenheit (900 degrees Celsius) in a vacuum tube furnace,” Dr. Bauer and co-authors explained.
“During the pyrolysis, the unit cell sizes of our structures shrank by roughly 80% compared to the initially fabricated sizes, yielding lattices with unit cell edge lengths of 2,020 nm, 1,440nm and 970 nm, respectively.”
“The struts of the pyrolyzed lattices have elliptical cross-sections with axial diameters of 330, 270 and 225 nm and lateral diameters of 275, 235 and 205 nm, respectively, for the three different lattice sizes.”
The resulting structures were tested for stability under pressure by the researchers.
“According to the results, load-bearing capacity of the lattice is very close to the theoretical limit and far above that of unstructured glassy carbon,” said team member Prof. Oliver Kraft.
“The strength-to-density ratios of the nanolattices are 6 times higher than those of reported microlattices. With a honeycomb topology, effective strengths of 1.2 GPa at 0.6 g/cm3 are achieved,” the scientists said.
“Diamond is the only bulk material with a notably higher strength-to-density ratio.”
J. Bauer et al. Approaching theoretical strength in glassy carbon nanolattices. Nature Materials, published online February 01, 2016; doi: 10.1038/nmat4561