Prof. Xiaoyan Li’s group published article in PNAS, reporting fabrication of lightweight, flaw-tolerant and ultrastrong nanoarchitected carbon
On March 19, Prof. Xiaoyan Li’s research group published a an article entitled with “Lightweight, flaw-tolerant and ultrastrong nanoarchitected carbon” in the journal PNAS, in collaboration with Prof. Huajian Gao’s group at Brown University and Prof. Julia Greer’s group at California Institute of Technology. This paper reported the fabrication and mechanical behaviors of lightweight and ultra-strong pyrolytic carbon nanolattices which are insensitive to fabrication-induced defects.
A long-standing challenge in modern materials design is to create low-density materials that are robust against defects and can withstand extreme thermomechanical environments because these properties typically are mutually exclusive: the lower the density, the weaker and more fragile the material. In this paper, Prof. Li’s group collaborated with the groups of Prof. Gao andP Prof. Greer, and demonstrated the creation of pyrolytic carbon nanolattices with stretching-dominated octet- and iso-truss topologies by a two-step procedure: direct laser writing and pyrolysis at high temperature (see Fig. 1). The unit cells of these nanolattices had the same dimensions of approximately 2 m, and the diameters of the individual struts in the lattices varied from 261 nm to 679 nm. The smallest characteristic size of the struts approached the limits of resolution of the available three-dimensional lithograph technologies. In situ scanning electron microscopy and ex situ compressive testing revealed that these pyrolytic carbon nanolattices have a compressive strength of up to 1.90 GPa at a density below 1.0 g/cm3 (see Fig. 2A). As a result, the pyrolytic carbon nanolattices achieved an exceptional specific strength (i.e., ratio of strength to density) of 1.90 GPa g-1 cm3, which is 1-3 orders of magnitude higher than those of nearly all micro/nanolattices reported so far. Such specific strength of our nanolattice is about 35% of that (5.60 GPa g-1 cm3) of diamond, which has the highest specific strength of all bulk materials.
Figure 1. Fabrication and microstructures of pyrolytic carbon nanolattices
The compression experiments also showed that these octet- and iso-truss nanolattices have the average fracture strains of 14.0% and 16.7%, respectively, which are larger than those of various brittle nanolattices reported previously. More remarkably, these nanolattices become insensitive to fabrication-induced defects (see Fig. 2B), allowing them to attain nearly theoretical strength of the constituent material. The combination of ultra-low density, ultra-high strength and specific strength, large fracture strain and flaw insensitivity of these pyrolytic carbon nanolattices are attributed to the miniaturization (nanosized beams) of the overall structure and the optimization of the lattice topology. This study provides a feasible pathway for scalable fabrication of robust nanoarchitected with defect tolerance, ultralight weight, and superior strength.
Figure 2. Mechanical properties of pyrolytic carbon nanolattices
In recent year, Prof. Xiaoyan Li’s research group worked on mechanics of novel nanostructured materials, and published some influential papers on high-profile international journals, including Nature Materials, Nature Communications, Science Advances, Advanced Materials and ACS Nano.
Prof. Xiaoyan Li, Prof. Huajian Gao and Prof. Julia Greer are co-corresponding authors of this paper. Dr. Xuan Zhang is the first author of this paper. This work was supported by the National Natural Science Foundation of China.
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