The Absolute Upper Limit of Material Strength and Ways to Reach it

Ideas on the nature of strength of defect-free nano-sized crystals are presented. Findings on experimental determination of uniaxial tensile strength of carbyne (linear allotrope of carbon) are given. It is found that carbynes’ strength exceeds 270GPа. This is significantly greater than the maximum strength level 130GPа ascertained in 2008 for graphene. It may be expected that this is not the next “all-time high” for strength but it upper limit. Based on the results of ab-initio calculations and molecular-dynamics simulation, it is exhibited that dependence of strength on dimensionality is key specific feature of nano-scale crystals. Increase in strength at transition from 3D-crystal (diamond) to 2D-crystal (graphene) and 1D-crystal (carbyne) is demonstrated for carbon. It is shown how carbynes can be used for creation of ultra-high-strength bulk materials. Requirements to structural parameters of such materials are formulated and assessment of their strength is given.