The extreme instability and strong chemical activity of carbyne, the infinite sp 1 hybridized carbon chain, are responsible for its low possibility to survive at ambient conditions. Therefore, much less has been possible to explore about carbyne as compared to other novel carbon allotropes like fullerenes, nanotubes and graphene. Although end-capping groups can be used to stabilize a carbon chain, length limitation is still a barrier for its actual production, and even more for applications. Here, we report on a novel route for bulk production of record long acethylenic linear carbon chains protected by thin double-walled carbon nanotubes. A corresponding extremely high Raman band is the first proof of a truly bulk yield formation of very long arrangements, which is unambiguously confirmed by transmission electron microscopy. Our production establishes a way to exceptionally long stable carbon chains, and an elegant forerunner towards the final goal of a bulk production of essentially infinite carbyne.Different kinds of allotropes can be formed from elemental carbon due to its sp n hybridization 1 . 1 arXiv:1507.04896v2 [cond-mat.mtrl-sci]

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Toughness is crucial to the structural function of bone. Usually, the toughness of a material is not just determined by its composition, but by the ability of its microstructure to dissipate deformation energy without propagation of the crack. Polymers are often able to dissipate energy by viscoplastic flow or the formation of non-connected microcracks. In ceramics, well-known toughening mechanisms are based on crack ligament bridging and crack deflection. Interestingly, all these phenomena were identified in bone, which is a composite of a fibrous polymer (collagen) and ceramic nanoparticles (carbonated hydroxyapatite). Here, we use controlled crack-extension experiments to explain the influence of fibre orientation on steering the various toughening mechanisms. We find that the fracture energy changes by two orders of magnitude depending on the collagen orientation, and the angle between collagen and crack propagation direction is decisive in switching between different toughening mechanisms.

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