Carbon Nanotubes Volume Research Articles

Wear behavior of Cu matrix composites reinforced with mixture of carbon and carbon nanotubes

In order to improve wear resistance and decrease the cost, carbon and carbon nanotubes reinforced copper matrix composites were fabricated by the power metallurgy method. The effects of carbon (carbon and carbon nanotubes) volume fraction and applied load on the friction coefficient and wear rate under dry sliding of the composites were investigated at room temperature. By scanning electron microscopy (SEM), the worn surfaces and debris were observed, and wear mechanism was also analyzed and discussed. The experimental wear process consists of the run-in, steady wear and severe wear process with the increasing of sliding distance. Both the friction coefficient and wear rate of the composites first decrease and then increase with the increasing of carbon volume fraction. The minimum friction coefficient and wear rate are obtained when carbon is 4.0vol%. The wear mechanisms of the composites change from the adhesive wear and delamination wear to abrasive wear with the increasing of carbon volume fraction.

Force Output, Control of Film Structure, and Microscale Shape Transfer by Carbon Nanotube Growth under Mechanical Pressure

We demonstrate that a film of vertically aligned multiwall carbon nanotubes (CNTs) can exert mechanical energy as it grows, and in our experiments the average force output is approximately 0.16 nN per CNT, for CNTs having an outer diameter of 9 nm and five walls. The film thickness after a fixed growth time and the alignment of CNTs within the film decrease concomitantly with increasing pressure which is applied by placing a weight on the catalyst substrate prior to growth, and CNTs grown under applied pressure exhibit significant structural faults. The measured mechanical energy density of CNT growth is significantly less than the energies of primary steps in the CNT formation process yet, based on the film volume, is comparable to the energy density of muscle and based on the volume of CNTs is comparable to hydraulic actuators. We utilize this principle to fabricate three-dimensional structures of CNTs which conform to the shape of a microfabricated template. This technique is a catalytic analogue to micromolding of polymer and metal microstructures; it enables growth of nanostructures in arbitrarily shaped forms having sloped surfaces and nonorthogonal corners and does not require patterning of the catalyst before growth.

Fabrication and properties of silver-matrix composites reinforced by carbon nanotubes

Composites of carbon nanotubes in a silver matrix have been fabricated by a powder metallurgy method. The effects of different nanotube contents on the relative density, hardness, bend strength and electrical resistivity of the composites were investigated. The results showed that the addition to the silver matrix of 8% by volume of carbon nanotubes caused increases in the Vickers hardness and the bend strength of about 27% and 9%, respectively. The nanotubes contributed less to the bend strength than to the hardness. The electrical resistivity of the composites increased slightly with increasing nanotube volume fraction when the volume content of the nanotubes was less than 10 vol.%. However, as the volume content increased from 10% to 25%, the resistivity experienced a sharp increase. Possible mechanisms are discussed in detail in the paper.