The nanotubes presents high potential of applications in nuclear power, integrating them both in advanced fuels developments nano-breeding and in nano-shielding. The carbon nanotubes may be successfully used to create fuel wires used in high temperature applications and near perfect burning generating new procedures in nuclear reactor waste management while reducing the waste by two orders of magnitude. The modified nanowire may hold various other materials as conductors and insulators being useful in direct conversion of the nuclear energy into electricity, by including in the center a sequence of high and low electron density conductors. As direct conversion structures they can handle all the required functions into a nuclear reactor or energy harvesting blanket to assure high power density, high efficiency and minimal waste. Another very challenging application is the usage of nanotube to channel low energy nuclear radiation and guide it, similar to the GHz wave-guides or to hundreds of THz optic fibers. The operation domain of the nanotubes is placed mainly in the domain of UV to X rays, being the role of composite structures or nanowire channeling to cover the gamma ray domain. The carbon nanotubes may become useful cold neutrons transport devices with directive capabilities as short bending or focusing. The theoretical approaches and simulations predicted these new application capabilities of nanowires for nuclear materials with exceptional properties.

Vertically aligned carbon nanotube (VACNT) arrays grown on quartz particles were produced in large amount via a floating catalysis process. Initially fast synchronous growth of VACNT arrays was observed, which is independently of the irregular shape and rough surface of the quartz particles. However, long VACNT arrays cracked and scattered anisotropically, depending on the irregular particles. The VACNTs have inner diameter of about 8.0 nm and relatively wide outer diameter distribution with a mean value of 36 nm. The outer diameter of CNTs, however, can be further decreased to 19 nm by tuning carbon source and concentration of catalyst precursor. The VACNTs have a high purity up to 97%. This work presents a simple way for controllable continuous production of VACNT array in large scale.

In this study, an efficient approach to prepare high quality BN nanotubes (BNNTs) was developed. BNNTs with specific sizes were prepared by sublimation of ammonia borane complex (BH3NH3) using two kinds of porous alumina anodic membrane template in two independently temperature controlled furnaces in a glovebox filled with N2. The BNNTs with template were nitrided at different temperatures 1300 ∼ 1700 °C in NH3. The BNNTs of 200 – 300 nm wide°60×°m long, and 70 – 80 nm wide°×40 μm long were finally collected after removal of the template by etching of with 40 wt% NaOH solution. The fourier transform infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS) results confirmed the formation of BN from BH3NH3. Ordered arrays of BNNTs were observed by scanning electron microscopy (SEM), and the microstructure of these BNNTs was investigated by transmission electron microscopy (TEM). It was found that the diameters of the BNNTs can be easily controlled by using templates with different pore sizes. The wall thickness of the nanotubes was increased by increasing the sublimation time or the amount of the starting BH3NH3. The crystallinity of BNNTs was improved at higher temperatures (1700 °C) in NH3.

The paper presents an evaluation of the feasibility of developing ionic surfactant coated single walled carbon nanotube (SWCNTs) (P-N) junction clusters via microcontact printing using intrinsic semi conducting SWCNTs. These SWCNTs are doped with anionic and cationic surfactant molecules respectively, thereby altering the Fermi energy levels of and its electrical properties. Two types of surfactants were used for doping the SWCNTs to develop extrinsically doped P and N type SWCNTs. Sodium dodecyl sulfate (SDS) having Na+ positive ionic charge (anions) and Cetyl trimethylammonium bromide (CTAB), having Br- negative ionic charge (cations) on its hydrophilic ends have been used to generate anionic SWCNTs (P type) and cationic SWCNTs( N- type respectively. Using, dual level patterning process, these extrinsically doped anionic and cationic semiconducting SWCNTs clusters are alternatively symmetrically patterned in a parallel array to form crossbar P-N junctions onto a standard microfabricated platform using flexible polymeric poly-dimethylsiloxane (PDMS) stamps. Ink-based transfer of the nanomaterial from the relief structures achieves parallel alignment of SWCNTs clusters. The electrical device characterization is achieved by measuring I-V characteristics from the base micro fabricated platform. Functionality of the nanodevice is demonstrated by studying the rectifying current – voltage (I-V) characteristics that shows promise towards the formation of a junction diode array, which can be used for integrating complex logic devices for high-end applications such as memory module and addressable logic. Lastly, we believe that the chemical modulation method and microcontact printing techniques will have a wide scope for development of nanomaterial-based devices.

The commercial synthesis of carbon nanotube sheets will be described. This process involves the following steps: chemical vapor deposition of long CNTs from mixed hydrocarbon type fuels, creation and stabilization of the catalyst, and a large textile forming device. Movies of the growth process will be presented and described. Further the electronic properties of these textiles will be presented and discussed as: (1) A function of temperature from −4 °K to 500 °C, (2) A function frequency from 0 up to about 30 GHz and (3) In a magnetic field up to 1000 Oe. It is shown that these yarns have semiconductor properties but surprisingly exhibit apparent metallic like conduction high at high frequencies. The thermoelectric behavior of the textiles (and yarns) made of this material will be discussed as will the applications in secondary batteries. A power level of up to three watts per gram for the thermoelectric material has been demonstrated.

A model for the elastic response of a foamlike forest of coiled carbon nanotubes under mechanical impact is proposed according to recent experiments reported in the literature. A force vs. displacement relation is derived for different geometries of the impacting object (sphere, cube and circular cone). In the model, entanglement among neighboring coils in the superior part of the forest is explicitly taken into account and we show that it allows the full description of the strongly nonlinear elastic behavior of the forest.

The strength of macroscopic materials made of carbon nanotubes depends on the quality of the nanotubes produced, as well as various methods of post-treatment. The average diameter and length of the nanotubes can be controlled through the various parameters of a specially designed injector system, in conjunction with the CVD furnace. Large non-woven textiles and yarns of pure nanotubes are created, and then post-processed in various ways to obtain the desired products. In this way textiles over 2 square meters, and yarns of over a half kilometer have been produced with strengths unprecedented in pure carbon nanotube materials.

Using ultrafast optical pump-probe spectroscopy, we have measured carrier relaxation times in epitaxial graphene layers grown on SiC wafers. We find two distinct time scales associated with the relaxation of nonequilibrium photogenerated carriers. An initial fast relaxation transient in the 70-120 fs range is followed by a slower relaxation process in the 0.4-1.7 ps range. The slower relaxation time is found to be inversely proportional to the degree of crystalline disorder in the graphene layers as measured by Raman spectroscopy. We relate the measured fast and slow time constants to carrier-carrier and carrier-phonon intraband and interband scattering processes in graphene.

This paper deals with preliminary measurements for prove-of-concept of a Carbon Nanotubes Field Effect Transistors (CNTFETs) based sensor array which could improve dramatically gas selectivity. CNTFET based sensors exploit the extremely sensitive change of the Schottky barrier heights between Single Wall Carbon NanoTubes (SWCNTs) and drain/source metal electrodes: the gas adsorption creates an interfacial dipole that modifies the metal work function and so the bending and the height of the Schottky barrier at the contacts [1,2]. Using CNTFET array fabricated using SWCNT mat as channel, we have achieved a sort of electronic fingerprinting of different gases. Actually, we want to demonstrate that the change of the metal electrode work function strictly depends on the metal/gas interaction : CNTFET transfer characteristics will change specifically as a function of this interaction. In this study we have fabricated different CNTFETs using three metal contacts (Au, Pd, Mo) and exposed them to two gases, DMMP and NH3, which have the same “electron-withdrawing” behavior. The CNTFETs array has been exposed to 1ppm of DMMP and 10ppm NH3 and we have identified two electronic fingerprinting. The totality of our measures have been performed at ambient conditions.

For practical deployment of carbon nanotubes, an understanding of their growth mechanism is required in order to obtain better control over their crystallinity, chirality and other structural properties. In this study, we focus on the influences of gas species on carbon nanotube synthesis using thermal chemical vapour deposition. The influence of methane, hydrogen, and helium gases was investigated from the viewpoint of gas chemistry in relation to the nanotube structural change, by varying the growth pressure, the gas-flow ratio and the growth temperature. Simple changes in the hydrogen gas concentration during different growth stages have been found to induce surprising changes to the nanotube formation. The structure of the tubular carbon growth changed from amorphous to graphitic as the growth temperature and the concentration of hydrogen in the initial periods of growth decreases. The excess hydrogen tends to give rise to poor crystalline carbon nanofibres but has the effect of increasing the yields. Hydrogen gas is typically used in reducing metal catalyst particles during the pre-treatment and the carbon nanotube growth periods. We show that while hydrogen species can improve yield, it can also result in the degradation of the nanotube's crystallinity. The use of hydrogen in the growth process is one of the key parameters for enhanced control of carbon nanotube/nanofibre growth and their resulting crystallinity.

A technique to synthesize high-quality single walled carbon nanotubes (SWNTs) using chemical vapour deposition (CVD) on Ge Stranski-Krastanow dots has been developed. From transmission electron microscopy and Raman measurements, the grown carbon nanotubes (CNTs) are identified as SWNTs with diameters ranging from 1.6 to 2.1 nm. Extensive scanning electron microscopy and atomic force characterisation of the effect of each stage in the growth process is presented. Our hypothesis is that pre-treatment stages lead to the formation of Ge nanoparticles, which act as seeds for CNT growth. This technique demonstrates the ability to synthesize high-quality SWNTs without the need for a metal catalyst, using processes and equipment standard to a silicon foundry.

Carbon nanotubes (CNTs) were grown by using a combination of ethanol and metallic Fe, which was not exposed to air before the growth. CNTs were also grown using intentionally oxidized Fe. The reaction products by these growths were analyzed by in situ photoelectron spectroscopy. We found that the oxidized Fe partially remained and did not completely reduce, resulting in low CNT yields. At higher growth temperature, oxide formation was found even when metallic Fe was used. These oxides induced a lowering of the decomposition efficiency of ethanol, resulting in difficulty of CNT growth by the combination of pure ethanol and Fe.

Buckling of arc discharge made multi-walled carbon nanotubes with various lengths was studied by alternating the length of a multi-walled nanotube by intermittent cutting. Buckling stresses were determined by measuring force-distance curves employing an atomic force microscope and the values were compared with those expected from the Euler's theoretical model. As the length of a nanotube was shortened, its buckling mode changed from elastic compressive bending with Young's modulus of 1.2TPa, to inelastic compressive fracture. The inelastic behavior observed for short nanotubes can be attributed to the buckling mechanism, in which ripple-like distortions develop along the nanotube sidewalls.

Fabricating horizontally aligned single wall carbon nanotubes (CNTs) with controlled properties has been one of the significant challenges for field-effect transistor (FET) applications. This report demonstrates a novel procedure for the fabrication of horizontally aligned single walled CNTs using the focused ion beam (FIB) and chemical vapor deposition (CVD). This method allows the morphologies, internal structures, and elemental compositions of CNTs to be directly analyzed in the scanning electron microscope (SEM) and transmission electron microscope (TEM) and avoids any sample preparation procedures that might alter the structure of the CNTs. The techniques of electron beam and ion beam induced deposition (EBID and IBID) of Pt electrodes to the CNT ends were compared and both were found to produce metal contamination around the target area. The fabrication of large area electrodes to assist in testing the CNT's electronic properties, including contact resistance and I-V characteristics was investigated. Using this fabrication technique we were able to perform an I-V sweep on a CNT circuit as well as detect the metal contamination on the CNTs which occurred as a result of electrode deposition.

Vertically aligned carbon nanotube (CNT) nano-electro-mechanical (NEM) switches are currently being investigated for their application in radiation-hard, high temperature space electronics. Carbon nanotubes are attractive for switching applications since electrostatically-actuated CNT switches have low actuation voltages and power requirements, while allowing GHz switching speeds that stem from the inherently high elastic modulus and low mass of the CNT. Our NEM structure consists of CNTs that are grown using dc plasma-enhanced (PE) chemical-vapor-deposition (CVD) for forming vertically aligned, rigid tubes. A gas mixture of acetylene and ammonia were used for tube growth at a total pressure of a few Torr and temperatures up to 700 °C. We have formed arrays of single, vertically aligned tubes directly on Si, which was enabled by this first report of an optical lithography approach used to generate isolated tubes compared to e-beam lithography that is conventionally used. Vertical NEM switch devices were formed where single, vertically aligned tubes were seen within deep trenches, in close proximity to conducting electrodes.

Saccharides, ranging from simple table sugar (sucrose) to lactulose were successfully used as solid-state precursors for the synthesis of multi-walled carbon nanotubes (MWCNT). Dehydrated saccharide residues mixed with catalyst powders were subjected to pyrolysis at high temperatures (up to 1300°C) under flowing Argon atmosphere. Pyrolysis products were investigated using TEM, SEM, Raman spectroscopy and EDS. Images taken using the S/TEM and bright field mode of TEM showed the presence of helical multi-walled carbon nanotube (H-MWCNT) and regular MWCNT formation. More than two or three catalyst particles were observed to be present inside the hollow core of some of the nanotubes synthesized, suggesting a high level of capillary activity inside the tubes during synthesis.

The potential use of carbon nanotubes (CNT) as interconnects requires also new characterization approaches as the existing ones are optimized for three-dimensional materials and do not work for inherently one-dimensional structures like CNTs. Therefore, we have developed a so-called pick-and-place process which allows to remove an individual CNT from a specific site and to place it at another location for further analysis. The approach is based on nanomanipulation combined with scanning electron microscopy (SEM). This paper presents the pick-and-place concept and explains the different steps required for its successful application. We further demonstrate its power by characterizing individual CNTs using transmission electron microscopy (TEM) and atomic force microscopy (AFM). The developed pick-and-place approach overcomes the challenge of site-specific analysis of CNT interconnects and strongly facilitates the routine analysis of CNTs.

Carbon nanotubes (CNTs) are successfully immobilized on a bamboo charcoal by chemical vapor deposition of gaseous tetraethyl orthosilicate (TEOS). Electron microscopies, Raman spectroscopy and electron energy loss spectroscopy are used to characterize the sample. The CNTs found on the bamboo charcoal support were several microns long, and their diameters ranged from 50nm to 300nm. From the high resolution transmission electron microscopic analysis, we found that the CNTs were composed of ∼30 layers of graphitic carbon sheets. Amorphous droplets were also found at the tips of the CNTs. This suggested that the growth of the CNT was via a vapor-liquid-solid mechanism. The amorphous droplets contained calcium, silicon and oxygen. The calcium impurity was originated from the bamboo while the silicon impurity was supplied by the TEOS. CNTs partially filled with calcium silicate were also found. It was evident that calcium silicate had played a critical role in the formation of these CNTs.

A large area carbon nanotube cathode was fabricated by use of a screen printing method. The emission properties of the cathode were investigated in both direct current and pulse mode experiments. In the direct current mode, the cathode has high field enhancement factor and high emission current density. In the double-pulse mode, the emission current density can approach 267 A/cm2 at an applied electric field of 15.4 V/um. Steady intense electron beams were obtained from the cathode. The results proved that the emission mechanism of CNTs at pulse electric field is plasma-induced field emission. The carbon nanotube cathode is suitable for not only field emission display applications but also high-power microwave device applications.

Local electronic structures of C60-Co hybrid films have been studied by X-ray photoelectron spectroscopy (XPS) and near-edge X-ray absorption fine structure (NEXAFS) spectroscopy. XPS spectra of C 1s main and satellite peaks for the C60-Co films show binding-energy shifts and also line-broadening compared to those in a pure C60 film. In addition, XPS spectra in valence band region suggest an appearance of three new components at near Fermi level and HOMO level in the C60-Co film. These results are attributed to hybridizations between Co 3d band and C60 LUMO. The same effects have been observed in NEAXFS spectra at C 1s excitations.