Elastic Properties of Carbon Nanotubes and Nanoropes

Elastic properties of carbon nanotubes and nanoropes are investigated using an empirical force-constant model. For single and multi-wall nanotubes the elastic moduli are shown to be insensitive to details of the structure such as the helicity, the tube radius and the number of layers. The tensile Young's modulus and the torsion shear modulus calculated are comparable to that of the diamond, while the the bulk modulus is smaller. Nanoropes composed of single-wall nanotubes possess the ideal elastic properties of high tensile elastic modulus, flexible, and light weight.Comment: 10 page

Oxidation-induced changes in mechanical properties of silicon nitride ceramics

The effect of oxidation on the room-temperature mechanical properties of four different silicon nitride ceramics is investigated. The strength and the elastic modulus of the whole material and the hardness, the fracture toughness and the elastic modulus of the internal region (without surface oxide layer) are determined for the materials oxidized at temperatures up to 1400°C. It is found that the fracture toughness decreases during oxidation at 1000°C. Reduction of the elastic modulus of the materials oxidized at 1400°C is also observed. A part of the changes in the mechanical properties is interpreted by the changes in the phase composition

Role of surface roughness in superlubricity

We study the sliding of elastic solids in adhesive contact with flat and rough interfaces. We consider the dependence of the sliding friction on the elastic modulus of the solids. For elastically hard solids with planar surfaces with incommensurate surface structures we observe extremely low friction (superlubricity), which very abruptly increases as the elastic modulus decreases. We show that even a relatively small surface roughness may completely kill the superlubricity state.Comment: 11 pages, 17 figures, format revte

Elasticity of polyelectrolyte multilayer microcapsules

We present a novel approach to probe elastic properties of polyelectrolyte multilayer microcapsules. The method is based on measurements of the capsule load-deformation curves with the atomic force microscope. The experiment suggests that at low applied load deformations of the capsule shell are elastic. Using elastic theory of membranes we relate force, deformation, elastic moduli, and characteristic sizes of the capsule. Fitting to the prediction of the model yields the lower limit for Young's modulus of the polyelectrolyte multilayers of the order of 1-100 MPa, depending on the template and solvent used for its dissolution. These values correspond to Young's modulus of an elastomer