588 / 2019-03-20 23:57:57

Strong, Hard, and Elastic Compressed Glassy carbon

strength,hardnes,carbon,elasticity

全体主题 > High Pressure Physics and Materials Science

ABSTRACT Glassy carbon (GC) is a class of nongraphitizing carbon made by firing polymeric precursors such as phenolic resin or furfuryl alcohol resin in an inert atmosphere. Recent research shows that type-I GC produced at low temperatures mainly consists of randomly distributed curved graphene layer fragments (1), and type-II GC fabricated at high temperatures can be considered as a carbon-based nanoarchitectured material, consisting of a disordered multilayer graphene matrix encasing numerous randomly distributed nanosized fullerene-like spheroids (2).
Here we find that this hybrid Type-II GC possesses a number of advantageous properties such as high strength (> 3 times stainless steel), high volume compression, superelastic (rubber-like) recovery from large volume deformation (～40% volume reduction), high uniaxial strain (up to 6% strain compared with that of the shape memory alloy), and a pressure-induced variable (zero or even negative) Poisson's ratio (2). Controlling the concentration, size and shape of fullerene-like spheroids with tailored topological connectivity to graphene layers is expected to yield exceptional and tunable mechanical properties, similar to mechanical metamaterials, with a potentially wide range of applications. The discovery of fullerene-like spheroids encased in a disordered, multi-layer graphene matrix opens a route for the preparation of new forms of carbon that feature combinations of two or more carbon allotropes.
In addition to the work above, here we also report a kind of novel sp2-sp3 hybridized carbon forms exhibiting a combination of lightweight, ultrastrong, hard, elastic and conductive properties (3). This type of carbons, called compressed glassy carbons, are recovered from compressing sp2-hybridized glassy carbon at various temperatures, and possess an interpenetrating graphene network which is formed from buckled graphene sheets that are crosslinked between sp3 nodes. This network is overall long-range disordered, but with local, short-range order on nanometer scale. The compressed glassy carbons possess extraordinary specific compressive strength (more than two-time stronger than those of commonly used carbon fibers, cemented diamond, SiC, and B4C), high hardness compared with commonly used ceramics, indentation elastic recovery above 70% (obviously higher than common metals and ceramics, and even higher than the shape-memory alloy, organic rubber, and silica with known excellent elasticity), and conductivity for many potential applications.
References: 1. P. J. Harris, Crit. Rev. Solid State Mater. Sci. 30, 235 (2005). 2. Z. Zhao et al., Nat. Commun. 6, 6212 (2015). 3. Meng Hu et al., Science Advances 3, e1603213 (2017).