A. V. Krestinin

The structure of 1D CuI crystals inside SWNTs.

Nanocomposites consisting of one‐dimensional CuI crystals inside single‐walled carbon nanotubes were obtained using the capillary technique. high‐resolution transmission electron microscopy investigations of the atomic structure of the encapsulated 1D CuI crystals revealed two types of 1D CuI crystals with growth direction <001> and relative to the bulk hexagonal CuI structure. Atomic structure models were proposed based on the high‐resolution transmission electron microscopy images. According to the proposed models and image simulations, the main contrast in the 1D crystal images arises from the iodine atoms whereas copper atoms, with lower atomic number giving lower contrast, are thought to be statistically distributed.

Fabrication and characterization of fluorinated single-walled carbon nanotubes

The optimum conditions for the fluorination of single-walled carbon nanotubes (SWCNT) in the atmosphere of gaseous fluorine with the nanotube structure remaining intact up to a stoichiometry of CFx, x ∼ 0.5 were determined. The kinetics of fluorination was examined. The fluorinated SWCNTs were characterized by various methods, including transmission electron microscopy, measurements of specific surface area and accessible internal volume, NMR spectroscopy, IR spectroscopy, X-ray absorption and photoelectron spectroscopies, thermal stability, and analysis of gaseous products by mass-spectrometry. The structure of fluorinated SWCNT was preserved up to brutto-composition CF0.5 but degree of fluorination of SWCNT bundles was decreased with distance from the SWCNT surface to its core. Such a decrease becomes evident at ∼1.5 nm distance. It means that the degree of fluorination depends on the degree of its dispersion.

Electrical conductivity of polypropylene fibers with dispersed carbon fillers

Polypropylene fibers with fillers in the form of carbon nanoparticles of four types (technical carbon, graphitized carbon nanofibers, multi-walled carbon nanotubes, and single-walled carbon nanotubes) have been synthesized. For all types of fillers, the electrical conductivity of the fibers has been measured as a function of the concentration of nanoparticles and the percolation thresholds have been determined. A correlation between the nanoparticle concentration and the electrical conductivity of the percolation cluster at the percolation threshold with the cross section, the axial ratio, and the shape of the nanoparticles dispersed in the polymer matrix has been discussed. The dependence of the electrical conductivity of the composite material with carbon nanofibers on the temperature has been measured.

Comparative X-ray absorption investigation of fluorinated single-walled carbon nanotubes

The C 1s and F 1s X-ray absorption spectra of pristine and fluorinated single-walled carbon nanotubes with different fluorine contents and nanodiamond as a reference compound have been measured with the aim of characterizing single-walled carbon nanotubes and their products formed upon treatment of the nanotubes with molecular fluorine at a temperature of 190°C. The spectra obtained have been analyzed by thoroughly comparing with the previously measured spectra of highly oriented pyrolytic graphite and fluorinated multiwalled carbon nanotubes and the spectrum of nanodiamond. It has been established that the fluorination of single-walled and multiwalled carbon nanotubes leads to similar results and is characterized by the attachment of fluorine atoms to carbon atoms on the lateral surface of the nanotube with the formation of the σ(C-F) bonds due to the covalent mixing of F 2p and C 2pz π valence electron states.

The behaviour of 1D CuI crystal@SWNT nanocomposite under electron irradiation

Nanocomposite 1D CuI crystal@SWNT was obtained by the growth of CuI nanocrystals inside single walled carbon nanotubes (SWNTs) using the capillary technique. High resolution transmission electron microscopy (HRTEM) investigation of the atomic structure of 1D CuI crystals revealed two types of 1D CuI crystals: with growth direction and relative to the bulk hexagonal CuI stucture. EM images were recorded and atomic models of the structure were proposed. According to the proposed models and image simulations, the main contrast in the 1D crystal images arises from the iodine atoms. In this paper the 1D CuI crystal@SWNT nanocomposite behavior determined mainly by the influence of the electron beam was investigated and it is shown that the 1D CuI nanocrystals can oscillate and rotate inside the nanotube channel under a 100kV electron beam. The oscillations occur within an exposure time of 25 s. With longer exposure time of ∼90 s, the 1D crystal gradually decreases in length, sometimes moving inside...

The formation and properties of one-dimensional FeHal2 (Hal = Cl, Br, I) nanocrystals in channels of single-walled carbon nanotubes

FeCl2@OCHT, FeBr2@OCHT, and FeI2@OCHT nanocomposites were obtained by capillary filling of the channels of carbon single-walled nanotubes (SWNTs) with melts of iron halogenides. The composites were studied by high resolution transmission electron microscopy (HRTEM), the capillary condensation of nitrogen at 77K, Raman spectroscopy, optical absorption spectroscopy, X-ray absorption spectroscopy, X-ray photoelectron spectroscopy, and Moessbauer spectroscopy. Substantial distinctions in the combination scattering spectra of SWNTs and nanocomposites in the region of radial modes and in the region of longitudinal and tangential oscillations were revealed. The presence of electron transfer between the nanocrystal and the SWNT wall was established in the nanocomposites. For the FeCl2@OCHT nanocomposite, two states of Fe+2 were found: the first is characterized by electron transfer from the nanotube to the nanocrystal, which leads to the electron structure of the SWNT and FeCl2 changing; the second corresponds to the strained intercalated state resulting from the mechanical effect of the small SWNT diameter on the FeCl2 nanocrystal.

Characterization of SWCNT products manufactured in Russia and the prospects for their industrial application

Single-wall carbon nanotubes (SWCNTs) are of the greatest interest for application in materials used for various purposes due to all of their unique properties. However, the practical use of SWCNTs has, until quite recently, been limited by the absence of a cheap industrial process for manufacturing them. Currently, a technology for the synthesis of SWCNTs from hydrocarbon raw materials providing the initial SWCNTs product of a sufficiently high quality has been developed in Russia for the first time in world history. In this work, the results of the characterization of the SWCNT products available in the Russian market are presented and the most promising directions among the technical applications of the materials and products on the basis of SWCNTs are highlighted.

Characterization of products on the base of single-walled carbon nanotubes by the method of nitrogen adsorption

In technical applications, the accessible internal volume of nanotubes and their external surface area are the most important characteristics of SWCNT materials. These values were determined by various methods based on the nitrogen adsorption. A new reference material for the αs-method has been proposed — the sample of pure SWCNTs without micropores. It has been shown that when choosing a sample of pure SWCNTs without micropores as the reference pattern, the t-method and the αs-method provide with well-coincided results for the values of the micropore volume and the external specific surface area. Thus, these methods can be used for these values determination in SWCNT products. In contrast to these methods, the method of Dubinin-Radushkevich (DR-method) gives systematically increased values of micropore volumes and substantively understated values of SWCNT external specific surface area. This can be explained by strong energy heterogeneity of the surface of SWCNT bundles.

Field emission from carbon layers containing very long and sparse nanotubes∕nanofilaments

Field-emission characteristics of carbon layers with very long (up to several mm) and sparse nanotubes (nanofilaments) have been investigated. For such layers field emission current of 10μA is registered at very low average electric field Eav=0.16V∕μm and the values of the field amplification coefficient β reach 45 000. It has been found that, at electric fields corresponding to the onset of the field emission, the emitting nanotubes are stretched towards the anode. At high emission currents (exceeding 30–50μA), one or several luminous filaments have been observed in the gap between the sample and the anode. These luminous filaments are carbon nanotubes (nanofilaments) heated by the emission current.

Field electron emission form single-walled carbon nanotubes with deposited cesium atoms

It has been found that deposition g of cesium atoms on single-walled carbon nanotubes covered with potassium atoms not only drastically increases emission current but also considerably changes the shape of current-voltage characteristics of field electron emission, namely, the characteristics become nonlinear in Fowler-Nordheim coordinates. It has been assumed that this effect is associated with the fact that field electron emission in these layers comes from single-walled carbon nanotubes, which have p-type conductivity after potassium treatment, while deposition of cesium leads to the formation of p-n junctions near nanotube tips. Part of the applied voltage drops in p-n junction, thus causing a nonlinearity of current-voltage characteristics.