Lightweight, flaw-tolerant, and ultrastrong nanoarchitected carbon

Abstract

It has been a long-standing challenge in modern material design to create low-density, lightweight materials that are simultaneously robust against defects and can withstand extreme thermomechanical environments, as these properties are often mutually exclusive: The lower the density, the weaker and more fragile the material. Here, we develop a process to create nanoarchitected carbon that can attain specific strength (strength-to-density ratio) up to one to three orders of magnitude above that of existing micro- and nanoarchitected materials. We use two-photon lithography followed by pyrolysis in a vacuum at 900 °C to fabricate pyrolytic carbon in two topologies, octet- and iso-truss, with unit-cell dimensions of ∼2 μm, beam diameters between 261 nm and 679 nm, and densities of 0.24 to 1.0 g/cm3. Experiments and simulations demonstrate that for densities higher than 0.95 g/cm3the nanolattices become insensitive to fabrication-induced defects, allowing them to attain nearly theoretical strength of the constituent material. The combination of high specific strength, low density, and extensive deformability before failure lends such nanoarchitected carbon to being a particularly promising candidate for applications under harsh thermomechanical environments.

Ultrahigh Energy Absorption Multifunctional Spinodal Nanoarchitectures

“…While possessing superior energy absorption capability, glassy carbon nanospinodals are at the same time ultrastrong and ultrastiff ( Figure ). Compressive strength‐to‐density ratios are on par with or even above those of beam‐based glassy carbon nanolattices (Figure a), which are the strongest reported architected materials and were synthesized by the same fabrication route as applied here . The same is true for the compressive stiffness (Figure b).…”

“…This is up to one order of magnitude higher than for other nano‐, micro‐, and macro‐scale architected materials and most state of the art impact protection structures . At the same time, we measure strengths and Young's moduli on par with the most advanced, yet brittle nanolattices, demonstrating true multifunctionality. Finite element simulations indicate that optimized shell‐based spinodal topologies prevent catastrophic failure under compression by impeding propagation of cracks that are aligned with the loading direction.…”

“…The energy absorption capability of progressively failing glassy carbon nanospinodals substantially exceeds that of any other 3D architected material (Figure d). We measure 3–20 times increased specific energy absorption compared to the most advanced nanolattices, as well as larger‐scale beam‐, and shell‐based architected materials . Compared to metal foams, our nanospinodals show up to an order of magnitude increase in energy absorption capability .…”

“…So far, lightweight nanoarchitected materials have mostly been designed for either high deformability or high strength, with true multifunctionality remaining a major challenge. Elastic beam buckling allows repeatable recoverability from large‐strain compression in low density lattices, providing high damping capability .…”

“…c) Energy absorption versus relative density. d) Comparison of the energy absorption with metallic foams, nanolattices, large‐scale beam‐, and shell‐based lattices …”