BNC tubules have been synthesized in a high isostatic pressure apparatus in Ar at 1650°C and 1.5 MPa. The synthesis of tubules was performed in BN-crucible in the presence of yttrium aluminum garnet. TEM studies were carried out using a JEM-2010 transmission electron microscope with EELS and EDS techniques, and a JSM-7600F scanning electron microscope. It is established that carbon content varies for different tubules in the sample and does not exceed 50%, and boron and nitrogen amounts in each tubule are approximately the same. It is shown that the tubules contain the Al2O3-filling with β-, ϵ- or γ-phase crystal lattice.

Cobalt-filled carbon nanotubes were synthesized at high temperature and high gas pressure. A high-resolution transmission electron microscopy study demonstrates that the product of the synthesis contains cylindrical carbon nanotubes whose cores are filled with cobalt nanoparticles or nanorods. It is shown that cobalt appears inside the nanotubes in three basic modifications: face-centered cubic (fcc) lattice, hexagonal close-packed (hcp) lattice and disordered polytypic structure. The fcc lattice is often twinned, with two or more non-parallel twinning planes being observed. The orientations of the fcc and hcp cobalt particles with respect to the nanotubes were investigated. The authors believe that the variety of cobalt modifications inside the nanotubes is due to the process of segregation of the closely packed structures from the melt.

BNC nanostructures were produced by the resistive heating of graphite and boric acid powder in a high isostatic pressure apparatus at a temperature of ∼1650°C, with a nitrogen pressure of 12MPa. The resultant nanostructures were examined using transmission electron microscopy, electron energy-loss spectroscopy and X-ray photoelectron spectroscopy. The growth mechanisms of the nanostructures are discussed.

Carbon branched structures are of interest because of their novel functionality and possible applications. Seamless junctions between carbon nanotubes (CNT) are obtained due to the topological defects (i. e. pentagons, heptagons, octagons, etc.) in the hexagonal lattice. In order to obtain multiwall Y-junction bamboo-like CNx nanotubes we use a technique of resistive heating of graphite in a water-cooled hot isostatic pressure apparatus (HIP). Argon-nitrogen mixture (with molar ratio 1:2.5) was used as a gas medium. We did not place any catalyst material into the reaction volume on purpose, but we used a mullite wool as one of the heat screen parts, and we believe, that the mullite wool was a source of Mg, Si, Ca, and Al found in catalyst particles of nanotubes. CNx nanotubes were characterized by transmission electron microscope JEM-2010 equipped with the EDS (Energy Dispersive X-Ray Spectroscopy) system. The TEM images have shown that the material consists of many Y-junctions with the main CNT stem and CNT branches. In most cases the angles between the branches are close to 120°. The nanotubes are 80–170 nm in diameter and have either one or several Y-junctions. Y-junction nanotubes both with short and long branches were observed. It is interesting that the short branches as well as those grown at the end of the process have a conic shape. Usually nanotubes are divided into identical compartments, but some of the observed nanotubes have the compartments of larger length. It is seen that all the Y-junction bamboo-like CNx nanotubes contain pear-shaped catalytic particles at the end. It is believed that the growth of branching structures occurs mainly due to the change of both physical and chemical properties of catalyst particles caused by different reasons.

The method for the production of multiwall Y-junction bamboo-like CN x nanotubes by the resistive heating of graphite is described. Different branched bamboo-like CN x nanotubes have been observed. The possible mechanism of the formation of branched nanotubes is proposed.

Extended abstract of a paper presented at Microscopy and Microanalysis 2004 in Savannah, Georgia, USA, August 1–5, 2004.

The curved intersected inner C-N layers have been observed inside nanofibers, formed in the High Isostatic Pressure (HIP) apparatus. The threshold field strength value of about 1V/mkm for the field electron emission, measured in the present study, falls among best values, found for graphite-like materials. The electron emission depends on peculiarities of the energy band diagram of the material and on the amount of band bending at the surface. Significant curvature of nanocarbons, produced with the participation of nitrogen and containing C-N bonds, is responsible for improved emission properties of our deposit. Close to the spherical shape of many fragments and numerous curved surfaces of our fibers allow not to orient them along the electric field, because such fragments will emit electrons at any orientation.

A variety of nanocarbons of different shapes and compositions (C, C-N) has been formed using a modified high isostatic pressure (HIP) apparatus. It was found that the presence of nitrogen in the background gas increases evaporation of graphite in the hot zone of the heater and increases the yield of carbon nanostructures. Carbon deposits formed by different gas pressures and temperatures were characterised using transmission electron microscopy and electron energy loss analytical microscopy. (C) 2003 Elsevier Science B.V. All rights reserved.

Carbon tubes or fibres with diameters ranging from 0.05 to 1 μm have been produced in a hot isostatic pressure apparatus, using gas pressures up to 100 MPa. Nitrogen, argon or mixtures thereof have been used. Other carbon structures were also present in small amounts. Transmission electron microscopy revealed tubes of cylindrical and conical shape. The semi-apex angles for the conical tubes were measured to be close to 5,10 and 20°. A possible growth mechanism for the tubes of conical shape is proposed.