Showing papers by "Andras Kis published in 2005"

Catalytically grown carbon nanotubes of small diameter have a high Young's modulus.

Abstract: Experimental studies of carbon nanotubes (CNTs) obtained through different synthesis routes show considerable variability in their mechanical properties. The strongest CNTs obtained so far had a high Young's modulus of 1 TPa but could only be produced in gram scale quantities. The synthesis by catalytic chemical vapor deposition, a method that holds the greatest potential for large-scale production, gives CNTs with a high defect density. This leads to low Young's modulus values below 100 GPa for multiwall CNTs. Here we performed direct measurements of the mechanical properties of catalytically grown CNTs with only a few walls and find a Young's modulus of 1 TPa. This high value is confirmed for CNTs grown under two different growth conditions where the synthesis parameters such as the hydrocarbon source, catalyst material, and the synthesis temperature were varied. The results indicate that the observed difference in the Young's modulus for the catalytically grown CNTs with high and low numbers of walls is probably related to the growth mechanism of CNT.

Imaging the life story of nanotube devices

Abstract: Live imaging of operating multiwall carbon nanotube (MWCNT-) based electronic devices is performed by high resolution transmission electron microscopy. Our measurements allow us to correlate electronic transport with changes in device structure. Surface contamination, contact annealing, and sequential wall removal are observed. Temperature profiles confirm diffusive conduction in MWCNTs in the high bias limit. This technique provides a general platform for studying nanoscale systems, where geometric configuration and electronic transport are intimately connected.

Elastic modulus of multi-walled carbon nanotubes produced by catalytic chemical vapour deposition

Abstract: Carbon nanotubes (CNTs) are ideal structures for use as reinforcement fibres in composite materials, due to their extraordinary mechanical properties, in particular high Young’s modulus (E∼1 TPa). Usually the high value of E is taken as granted for all types of carbon CNTs. Here we demonstrate that multi-walled carbon nanotubes (MWCNTs) produced by catalytic chemical vapour deposition (CCVD) have low moduli (E<100 GPa) independently of their growth conditions. We attribute this to the presence of structural defects. Additional high-temperature annealing failed to improve the mechanical properties. This study urges a better control of the growth process in order to obtain high strength CCVD grown MWCNTs suitable for reinforcement in large-scale industrial applications.

Nanoscale Mechanical Properties — Measuring Techniques and Applications

Abstract: The first part of this chapter describes local (at the scale of nanometers) measurements of mechanical properties. It includes detailed state-of-the-art presentation and in-depth analysis of experimental techniques, results, and interpretations.