An individual carbon nanocoil was clamped between two AFM cantilevers and loaded in tension to a maximum relative elongation of ∼42%. The deformation of the nanocoil agrees well with an analytical model of the spring constant that accounts for the geometric nonlinearity. The nanocoil behaves like an elastic spring with a spring constant K of 0.12 N/m in the low strain region. No plastic deformation was detected. High-resolution microscopy images and the electron energy loss spectrum (EELS) indicate that the nanocoils are amorphous with a sp 2 /sp 3 bonded-carbon ratio of ∼4:1.

Carbon nanocoils were prepared by catalytic pyrolysis of acetylene using iron-coated indium tin oxide as the catalyst. The effects of the constitution of catalyst, the growth temperature and time, the flow rate of acetylene gas on the growth of carbon nanocoils were investigated. It is found that the coils grow mainly from the interface of iron and indium tin oxide films. The coils generally consist of two or more nanotubes. Each coil has its own external diameter and pitch, which is determined by the structure of the catalyst at its tip. The growth of the carbon nanocoil is considered to be due to the nonuniformity of the carbon extrusion speed at different parts of the catalyst particle containing iron, tin, indium and/or oxygen. It is confirmed that iron is crucial in the formation of a nanotubule and indium tin oxide induces the helical growth of the nanotubule.

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We have investigated how an iron catalyst changes during the growth of vertically aligned carbon nanotubes by in situ measurement of X-ray diffraction. It is found that heating the catalyst film to a growth temperature of 700°C in He atmosphere induces its oxidation beyond 100°C due to adsorbed moisture and changes the film to particles at approximately 600°C. At 700°C, the catalyst particles consist mainly of iron oxide with a cubic system. By feeding C2H2, the catalyst starts to be deoxidized and then absorbs carbon atoms to form Fe-C and Fe3C. The growth mechanism of nanotubes is discussed in terms of the crystalline phase and orientation of the catalyst.

Efficient chemical vapor deposition (CVD) synthesis of super long (7 mm) aligned carbon nanotubes (CNTs) with highdensity is reported here. Activity of catalyst nanoparticles has been achieved for very long time periods (ca. 12 h) by optimization of experimental parameters. The relative levels of ethylene and water, as well as those of ethylene and H 2 , were found to be most important for achieving extended-time activity of the catalyst. Transmission electron microscope (TEM) images revealed that the nanotubes were mainly double-walled, but very few single-walled and multi-walled nanotubes were also present in the sample.

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We have synthesized carbon coils of nanometer-scale size by catalytic thermal chemical vapor deposition. The catalyst used is iron-coated indium tin oxide and the carbon source is acetylene. The yield of carbon coils is over 95% at a growth temperature of 700°C. The carbon coil usually consists of two or more carbon tubules and each of them grows with its own diameter and pitch. The external diameters of the coils are from several tens to several hundreds of nanometers. It is found that iron plays an important role in the growth of carbon nanotubes, while indium, tin, oxygen, and/or their alloys are necessary in the formation of the coils.

Millimeter (mm) long vertically aligned carbon nanotubes (CNTs) were grown by the catalyst assisted thermal chemical vapor deposition (CVD) technique. The continuous growth of CNTs as long as 7 mm was observed after 12 h of deposition by adjusting the growth parameters for making the catalyst active for a long time. The direct dependence of the number of walls of mm-long CNTs on the Fe catalyst thickness was observed. The successful syntheses of single-walled nanotubes (SWNTs), double-walled nanotubes (DWNTs), and multiwalled nanotubes (MWNTs) with high percentages (∼80%) were achieved by varying the catalyst layer thickness. The effect of Al 2 O 3 buffer layer was found to be critical for this controlled synthesis, which has been discussed in detail. The possible growth mechanism is also discussed to better understand this phenomenon.