Alexander G. Ryabenko

Properties of nanocomposites based on crosslinked elastomeric polyurethane and ultrasmall additives of single-wall carbon nanotubes

It is shown for the first time that the addition of ultrasmall amounts of single-wall carbon nanotubes leads to a significant increase in the main mechanical characteristics of the crosslinked poly(urethane urea) elastomer. The elastic modulus and the tensile strength pass through maxima as the nanotube concentration is increased from 0 to 0.018 wt %; at a nanotube concentration of 0.002 wt %, the maximum values of the modulus and strength are higher by factors of 2.5 and 1.5, respectively, than the corresponding values for the unfilled polymer. The thermomechanical, spectral, and structural characteristics of nanomodified elastomers are investigated, and possible causes of change in their mechanical parameters are discussed.

Reactions on single-walled nanotubes: 1. Radiation-stimulated reactions in aqueous suspensions of single-walled carbon nanotubes in surfactant solutions

Chical reactions initiated by 60Co γ-radiation in the suspensions of single-wall carbon nanotubes (SWCNTs) in the aqueous solutions of a surfactant, cetyltrimethylammonium bromide (CTAB), have been studied. In a pure aqueous solution of CTAB, the radiolysis of water leads to the appearance of OH radicals, which induce the oxidation of CTAB molecules. In the suspensions, CTAB molecules are concentrated on SWCNTs and oriented in one direction and the OH radicals induce the crosslinking of surfactant molecules. A moss-like coating is formed on the nanotubes, and the suspension is converted into jelly. The coating does not have covalent bonds with the nanotube walls. The formation of the polymer is due to the packing of molecules around the nanotube, rather than their chemical properties.

Reactions on single-walled nanotubes: 2. Reactions on the nanosized surface of nanotubes in liquid hydrocyanic acid

Chemical reactions stimulated by γ-radiation in liquid hydrocyanic acid (HCN) in the presence of single-walled edcarbon nanotubes (SWCNTs) have been studied. The polymerization of HCN on the surface of nanotubes occurs several times more rapidly than in pure HCN, and the set of radiolysis products becomes poorer. It is likely that the approach of polymerizing reagents on the nanosized surface is limited by specific mutual orientations. Furthermore, the CN and H radicals add to the walls of the nanotubes and the nanotubes become soluble in water, ethanol, and acids.

Reactions of excited fullerenes C60 and C70 studied by mass spectrometry

The transformation of the mass spectra of the laser-desorbed C60 and C70 samples with a successive increase in the laser power, resulting in an increase in the degree of excitation of C60 (C70) and in the number of the particles in the laser plume, was studied. Unusual metastable clusters (C60 + C2) and (C70 + C2) are formed even at a minimum laser power and begin to dissociate after ∼0.5 μs following a short (3 ns) laser pulse. An increase in the laser power results in the appearance of peaks of metastable clusters C62 (C72) with the statistically normal lifetime without a delay of dissociation. A further increase in the laser power produces metastable clusters C60k–2n and C70k–2n (k = 2, 3) formed without a lag from the dimers and trimers of C60 (C70) by the ejection of a number of C2 required for the stabilization of the C2 molecules. The peak of C70 appears simultaneously with the appearance of the (C60)2–2n peaks upon the laser desorption of pure C60. These findings provide evidence for the growth of the excited fullerene clusters by coalescence and subsequent stabilization due to the ejection of a small fragment rather than by the implantation of C2 into the fullerene framework. This mechanism of cluster growth should be taken into consideration in modeling fullerene formation in an electric arc reactor, because the clusters formed under these conditions have a substantial excess internal energy.