Mechanical Properties of Nanodiamond

The distinct mechanical characteristics of diamond are based on its lattice stmc-ture and electronic properties. It stands out for the highest hardness ever measured for a natural material, for large moduli of bulk and shearing and for a high scratch-resistance. Dislocations are little mobile in its lattice, and the material features a very high surface energy contributing to the hardness as well. 

The existence of covalent bonds is an essential prerequisite for a great hardness of an element A three-dimensional, orthotropic lattice with cubic symmetry may be formed from a minimum number of four bonds arranged at an angle of 109.47 ° (tetrahedral angle) relative to each other. In the periodic table, these conditions 

The large surface energy of diamond distinctly complicates the cleavage of the crystal lattice with respect to most directions in space. The (lll)-plane constitutes the crystallographic face with the lowest surface energy after all, so a cleavage preferably takes place in perpendicular to this facet 

---

The preparation of composite materials in general is a very important appHca-tion of the mechanical properties of nanodiamond. With many polymers like caoutchouc, polysiloxanes, fluoroelastomers polymethacrylates, epoxy resins, etc., composites with markedly improved mechanical characteristics have already been obtained from the noncovalent incorporation of nanodiamond by simple admixing during polymerization. The modulus of elasticity, the tensile strength, and the maximal elongation of the material all increase upon this modification. Depending on the basic polymer, just 0.1-0.5% (w/w) of nanodiamond are required to achieve this effect (Table 5.3). Polymer films can also be reinforced by the addition of nanodiamond. For a teflon film with ca. 2% of nanodiamond added, for example, friction is reduced at least 20%, and scratches inflicted by mechanical means are only half as deep as in neat teflon. 

U. Maitra, K.E. Prasad, U. Ramamurty, and C.N.R. Rao Mechanical properties of nanodiamond-reinforced polymer-matrix composites. Solid State Communications, 149 (39-40), 1693-1697, 2009. 

---