Hydrogenation of fullerites in the presence of intermetallic compounds or metals

Fullerene hydrides containing 24–26 H atoms per fullerene molecule were obtained by hydrogenation of solid-phase mixtures of fullerenes with either intermetallic compounds LaNi₅, LaNi_4.65Mn_0.35, CeCo₃ or V and Pd metals with gaseous hydrogen at 1.0–2.5 MPa and 573–673 K. These fullerene hydrides decompose at 800 K with evolution of H₂. Upon subsequent heating to 1000 K, vanadium reacts with fullerene to yield a cubic phase of vanadium carbide. The intermetallic compounds react with fullerene with the formation of a metallic phase of the 3d-metal and destruction of fullerene. Palladium does not react with fullerene. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 679–683, April, 1997.     

Features of electrochemical and thermal properties of CsHSO<Subscript>4</Subscript>-C<Subscript>60</Subscript> composite materials

New composite proton-conducting materials based on cesium hydrosulfate with fullerite C₆₀ were synthesized. The concentration dependence of the proton conductivity and thermal properties of synthesized materials with C₆₀ contents from 0 to 50 vol % was studied. It was found that these dependences are nonmonotonic with extrema at C₆₀ contents of ～2 and 30 vol %. The conductivity of the composite material with a C₆₀ content of ～2 vol % is almost twice higher than the conductivity of pure CsHSO₄ due to the formation of a new surface phase, which is confirmed by thermal analysis methods.     

Electronic structure of C60 films

A complete set of fundamental optical functions of fullerite (C₆₀) films in energy ranges of 2.5–5.0 and 4.0–9.0 eV is calculated using the known spectra of the imaginary and real parts of the dielectric constant. An integrated spectrum of the dielectric constant is decomposed into elementary components. Three basic parameters of each component (the maximum and halfwidth energies and oscillator strength) are determined. Based on the known theoretical calculations of fullerite zones, a scheme of the nature of these components of the dielectric constant is suggested. Udmurt State University, 71, Krasnogeroiskaya Str., Izhevsk, 426034, Russia. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 66, No. 2, pp. 227–232, March–April, 1999.     

Detailed study of defects in thin fullerite films

The structural investigations of fullerite films were performed using high‐resolution electron microscopy, electron diffraction and electron energy loss spectroscopy and X‐ray photoelectron spectroscopy. In particular defects such as dislocations, stacking faults and twins were studied in details. It was shown that fullerite films could be characterized by a face‐centered cubic (f.c.c.) structure with lattice parameter a = 1.416 nm. They are distinguished for their rich polytypic structure that is caused by breaking of alteration of closely packed planes of (111) type. The quantitative method based on information theory using the “run‐length encoding” algorithm was suggested to evaluate the degree of disorder in the f.c.c structure of thin fullerite films.     

Doping of fullerite with molecular oxygen at low temperature and pressure

Two methods are described for doping of fullerite C₆₀ with molecular oxygen at a pressure of ∼104 Pa and at temperature 20–30 °C. It was found by mass spectrometry using oxygen ¹⁸O as dopant that a portion of molecular oxygen absorbed by the pre-decontaminated fullerite (first method) is removed as CO and CO₂ at the heating temperature ≤200 °C. Doping during fullerite precipitation from the liquid phase (second method) makes it possible to prepare samples with the oxygen content ≥1.2 at.%. The fullerite doped with oxygen to this level is diamagnetic. The paramagnetic properties of an O₂ molecule disappear when O₂ is incorporated into the fullerene lattice. This is interpreted on the basis of quantum chemical calculations as a sequence of equilibrium formation of the adduct C₆₀O₂. Calculations showed that the subsequent chemical transformation of C₆₀O₂ resulting in the O-O bond cleavage is energetically favorable, enabling prerequisites for the formation of products of incomplete (CO) and deep (CO₂) oxidation of fullerene under mild conditions. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 662–671, April, 2006     

Low-Cost Synthesis of Fullerene Derivatives

Refined mixed fullerenes were used as a reagent in known organic reactions instead of the pure fullerene C₆₀ with aim to find an alternative, low-cost method for the synthesis of fullerene derivatives potentially exhibiting photoconductive properties. The isolation of C₆₀ or C₇₀ in clean form without admixtures requires the use of large quantities of toluene or other nonpolar solvents, polluting the environment and multiplying the production cost. 1,3-Dipolar cycloaddition of azomethine ylide to fullerite was chosen because this reaction is one of the most widely used for fullerene functionalization, producing material possibly presenting photoinducing behavior. The data showed that the use of the cheaper mixed fullerenes instead of pure C₆₀ leads to the isolation of the same expected products with similar yields. The photoelectric properties of mixed fullerenes and their organic derivatives were also examined. A slightly semiconductive behavior was confirmed as well as a noticeable photoresponse.

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Thermodynamic properties of graphite-like nanostructures prepared by thermobaric treatment of fullerite C60

Temperature dependences of the heat capacities of disordered graphite-like nanostructures prepared by the thermobaric treatment of fullerite C₆₀ (p = 2 and 8 GPa, T = 1373 K) were measured in the temperature ranges from 7 to 360 K in an adiabatic vacuum calorimeter and from 330 to 650 K in a differential scanning calorimeter. At T < 50 K, the dependences obtained were analyzed using the Debye theory of the heat capacity of solids and its multifractal version. The fractal dimensions D were determined and some conclusions on the heterodynamic character of the structures studied were made. The thermodynamic functions C _p ^o T), H ^o(T) − H ^o(0), S ^o(T) − S ^o(0), and G ^o(T) − H ^o(0) were calculated in the temperature range from T → 0 to 610 (650) K. The thermodynamic properties of the graphite-like nanostructures studied and some carbon allotropes were compared. The standard entropies of formation Δ_f S ^o of the graphite nanostructures studied and diamond were calculated along with the standard entropies of the reactions of their synthesis from the face-centered cubic phase of fullerite C₆₀ and their interconversions at T = 298.15 K. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1940–1945, September, 2008.