Characteristics of graphene material

Stability 
Calculations show that if the size of the graphene sheet is less than about 20nm, the graphene sheet is thermodynamically unstable ("graphene is the most unstable structure before about 6000 atoms"), and only for more than 24, A molecule of 000 atoms becomes the most stable fullerene (as in graphite).
Thermal conductivity
The heat transfer of graphene is an active research area, which has attracted people's attention due to its potential for thermal management applications. It is known that when a single layer of graphene is supported on an amorphous material, the room temperature thermal conductivity is reduced to approximately 500 – 600 W⋅m−1⋅K−1.
Mechanical properties
The carbon-carbon bond length in graphene is about 0.142 nanometers. Graphene sheets are stacked to form graphite with a spacing of 0.335 nm.
Graphene is the strongest material ever tested, with an inherent tensile strength of 130 GPa and Young's modulus (stiffness) of 1 TPA (150,000,000 psi). The announcement of the Nobel Prize illustrates this point. It is said that a 1 square meter graphene hammock can support a 4 kg cat, but its weight is only 0.77 mg as heavy as a cat’s whisker (about 0.001% of 1 m2 paper weight).
A single layer of graphene bent at a large angle is obtained with negligible strain, showing the mechanical robustness of the two-dimensional carbon nanostructure. Even in the case of extreme deformation, excellent carrier mobility in single-layer graphene can be maintained.
The elastic constants of suspended graphene sheets were measured with an atomic force microscope. The graphene sheet is suspended on the cavity where the tip of the SiO2 atomic force microscope exerts stress on the thin plate to test its mechanical properties. Unlike bulk graphite, its spring constant is in the range of 1-5 N/m, and its stiffness is 0.5 TPa. These inherent characteristics may lead to NEMS applications such as pressure sensors and resonators. Due to its large surface energy and in-plane extensibility, the planar graphene sheet is unstable in rolling, that is, it is bent into a cylindrical shape, which is its low-energy state.