Research ArticleMATERIALS SCIENCE

Defects and plasticity in ultrastrong supercrystalline nanocomposites

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Science Advances  08 Jan 2021:
Vol. 7, no. 2, eabb6063
DOI: 10.1126/sciadv.abb6063
  • Fig. 1 Nanostructure and defects in iron oxide–oleic acid bulk supercrystalline nanocomposites.

    (A) Single supercrystal FCC nanostructure and bulk pellet after processing. Photo credit: Diletta Giuntini, Hamburg University of Technology. (B) Intersupercrystalline interface (high-angle grain boundary). (C) Low-angle grain boundary. (D) Frank partial. (E) Twins. (A) and (B) are SEM micrographs, (C) and (E) are TEM micrographs, and (D) is a STEM high-angle annular dark field micrograph. The FCC superlattice is visualized along the [112¯] projection axis in (C) and (D), while along the [101¯] axis in (E). Scale bars, 100 nm. The defects depicted here are detected regardless of cross-linking.

  • Fig. 2 Nanoindentation of supercrystalline nanocomposites.

    (A to D) Indents in the non–cross-linked supercrystalline nanocomposites. (A) SEM micrograph of a 500-nm-deep Berkovich indent. (B and C) AFM topography map and profiles of the indent shown in (A). (D) SEM micrograph of a 300-nm-deep cube-corner indent [reproduced with permission from (7)]. (E to H) Indents in the cross-linked supercrystalline nanocomposites. (E) SEM micrograph of a 500-nm-deep Berkovich indent. (F and G) AFM topography map and profiles of the indent shown in (E). (H) SEM micrograph of a 300-nm-deep cube-corner indent. Scale bars, 500 nm. (I to K) Pile-ups (I), sink-in (J), and equivalent plastic strain (K) resulting from FE simulations of a Berkovich indentation, 500 nm in depth, in the cross-linked material. The visualized subindent cross section is marked in the inset of (K). In (I), the pile-ups are highlighted by only plotting material displacements above the surface, in direction perpendicular to it (z); in (J), the complementary plot is shown.

  • Fig. 3 Deformation under indent in supercrystal with cross-linking of the organic ligands.

    (A) Indent’s area from which the lamella was extracted. (B) TEM image of half the lamella, with highlight of the deformed subindent area. (C) Higher-resolution TEM micrograph of the unperturbed superlattice away from the indent, with the respective FCC unit cell orientation. (D) Plastically deformed area under the indent, with highlighted (111) planes, revealing dislocation-like structures arranged along concentric arrays. (E) Map of the alterations in the spacing among (111) planes, d, with respect to the equilibrium value (14.1 nm), revealing compression and expansion zones in the superlattice. The indent is of the Berkovich type, 500 nm in depth. Scale bars, 500 nm (A) and 100 nm (B) to (E).

  • Fig. 4 Deformation under indent in supercrystal without cross-linking of the organic ligands.

    (A) Surface material removal. (B and C) Pile-ups around the indent’s edges. (D) Mapping of the interplanar spacing changes among tightly packed {111} planes, d, with respect to the equilibrium value (14.8 nm). Planes of the {111} family oriented almost horizontally with respect to the applied load were selected for the mapping. (E) Scheme of slip bands and dislocation movement in analogy with shear patterns observed under indents in atomic single crystals (41, 42). Tension and compression areas are also marked, with positive and negative sign, respectively. Note the matching of these patterns in (D) and (E). (F to H) Slip bands features, in the central area of an external slip band (F), at the termination of the same external slip band, where an interstitial is detected (G), and at the intersection between two internal bands, where cleavage is detected (H). The indent is of the Berkovich type, 500 nm in depth. Scale bars, 500 nm (central reference image) and 50 nm (all other micrographs).

Supplementary Materials

  • Supplementary Materials

    Defects and plasticity in ultrastrong supercrystalline nanocomposites

    D. Giuntini, S. Zhao, T. Krekeler, M. Li, M. Blankenburg, B. Bor, G. Schaan, B. Domènech, M. Müller, I. Scheider, M. Ritter, G. A. Schneider

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