Mechanical properties of carbon nanotubes Mechanical properties of carbon nanotubes The mechanical properties of carbon nanotubes reveal them as one of the strongest materials in nature. Carbon nanotubes (CNTs) are long hollow cylinders of graphene. Although graphene sheets have 2D symmetry, carbon nanotubes by geometry have different properties in axial and radial directions. It has been shown that CNTs are very strong in the axial direction. Young's modulus on the order of and tensile strength of were obtained. Carbon nanotubes are the strongest and stiffest materials yet discovered in terms of tensile strength and elastic modulus respectively. This strength results from the covalent sp bonds
Material properties of diamond ("proper", "unalterable", "unbreakable") and sometimes called adamant, diamond is the hardest known naturally occurring material, scoring 10 on the Mohs scale of mineral hardness. Diamond is extremely strong owing to the structure of its carbon atoms, where each carbon atom has four neighbors joined to it with covalent bonds. The material boron nitride, when in a form structurally identical to diamond (zincblende structure), is nearly as hard as diamond; a currently hypothetical material, beta carbon nitride, may also be as hard or harder in one form. It has been shown that some diamond aggregates having nanometer grain size are harder