R. M. Nikonova

Deformation-induced changes in the structure of fullerites C60/70 during their mechanical activation

Structural changes occurring during the mechanical activation of fullerites C60/70 have been investigated using X-ray diffraction, IR and UV spectroscopy, and scanning electron microscopy. The complete destruction modes of fullerite have been determined (3.5 h at the intensity of the mill of 4.3 W/g and 28 h at 2.2 W/g). The destruction of the crystal structure of fullerites is accompanied by the destruction of fullerene molecules. The residual solvent, which enters into the composition of C60/70, is retained during the entire time of mechanical activation. In this case, the low-frequency shift of absorption bands of toluene (729 → 725 cm−1), which is caused by the deformation of the solvent molecule in the composition of crystal solvates, has been observed. It has been shown that the deformation stability of graphite is substantially lower than in the case of fullerite.

C60-C70-C6H5CH3 crystal solvates: Structure and thermal stability

Differential scanning calorimetry (DSC) and X-ray diffraction were used to study the thermal stability and structure of C60-C70-C6H5CH3 crystal solvates synthesized at room temperature. The decomposition of the crystal solvates generates C60-C70 solid solutions with hexagonal close-packed (hcp) structure.

Features of the oxidation of C60 and C70 fullerites as studied by IR spectroscopy

Features of the oxidation of C60 and C70 fullerites were studied by infrared spectroscopy. It was shown that for C60 fullerite, the presence of toluene residue reduces the temperature at which oxidation starts. The form of the toluene (solvate or nonsolvate) is not important. A low-frequency shift in the valence C-O-C vibrations of C70 fullerene due to local steric strains was discovered.

The structural-phase state of C60-C70 fullerene mixtures

The structural and phase state of the C60-C70 system at various C60/C70 ratios in mixtures obtained by the vaporization of solutions in toluene at ∼98°C was studied by X-ray structure analysis, differential scanning calorimetry, and infrared spectroscopy. Solid solutions based on the face-centered cubic packing of C60 are not formed in the C60-C70 system at C70 contents from 0.5 to 50 wt %. The hexagonal close packing of a solid solution of C60 in C70 can be formed as a result of the thermally activated decomposition of the ternary crystal solvate in the C60-C70-C6H5CH3 system. The structural state of multiphase mixtures formed under conditions far from equilibrium is characterized by a high degree of structure imperfection and greater ability to undergo oxidation compared with C60 and C70.

Morphological features of C60 and C70 microcrystals obtained from C6H5CH3 and CCl4 solutions

Fullerene C60 and C70 microcrystals of different morphologies obtained by crystallization from toluene and carbon tetrachloride solutions were investigated using scanning electron microscopy and diffuse reflectance IR Fourier transform spectroscopy. The obtained results are discussed with regard to the features of fullerenes clusterization processes in solutions.

Formation of secondary structures in heat-resistant steels under sliding friction

The formation of secondary structures in nicotrated layers on surfaces of complex-alloy heatresistant 25Kh3M3NBTsA and 30KhN2MFA structural steels under the effect of sliding friction with resource lubrication has been studied using metallography, X-ray diffraction, X-ray photoelectron spectroscopy, and thermodynamic modeling. It has been found that, under friction, the nicotrated layer on the steels oxidizes to produce iron oxides, which is substantially less pronounced for 25Kh3M3NBTsA steel than for 30KhN2MFA steel. It has been shown using thermodynamic modeling that, under equilibrium conditions, the heating of both steels to a temperature of ~300°C leads to the formation of an internal-oxidation layer, which consists of FeO with MoO2, Cr2O3, and carbon impurities, a Fe3O4 interlayer with MoO2 and Cr2O3 impurities, and a top layer of Fe2O3 with Cr2O3 impurity. The heating of steels to a temperature of ~700°C leads to the formation of an internal-oxidation layer, which consists of FeO with MoO2 and carbon impurities, a Fe3O4 interlayer with MoO2 impurity, and a top layer of Cr2O3 with Fe2MnO4 and SiO2 impurities.

Oxidation of C60 and C70 Fullerites in Air

The oxidation of C60 and C70 fullerites and C60/C70 mixture is accompanied by the decomposition of the carbon frameworks of the molecules at annealing temperatures of 250 and 445°C. Fourier-IR and HPLC studies show that the oxidation/decomposition of C70 molecules is more active than that of C60. The stages of fullerite interaction with oxygen while heating in air were determined.

IR-Fourier spectroscopic studies of structural changes in fullerenes C60 and C70-Toluene systems

The C60-toluene and C70-toluene complexes were studied by IR-Fourier spectroscopy. The complexes were obtained by crystallization from a toluene solution at room temperature. The changes in the IR spectra caused by the deformation of toluene molecules in the complexes allowed us to study the phase transitions in the fullerene-aromatic solvent systems.

Thermal behavior of a mixture of fullerenes and fullerites C60/70

The thermal behavior of a mixture of fullerites C60/70 was studied by X-ray diffraction and IR and UV spectroscopy. The temperature range in which the molecular and crystal states degrade was determined (825–875°C in a CO medium). In the C60/70 mixture, fullerenes decomposed at lower temperatures than in pure C60 and C70; the decomposition temperature depended on the impurity (oxygen and solvent) content.

Stacking faults and mechanisms strain-induced transformations of hcp metals (Ti, Mg) during mechanical activation in liquid hydrocarbons

The evolution of the structure and substructure of metals Ti and Mg with hexagonal close-packed (hcp) lattice is studied during their mechanical activation in a planetary ball mill in liquid hydrocarbons (toluene, n-heptane) and with additions of carbon materials (graphite, fullerite, nanotubes) by X-ray diffraction, scanning electron microscopy, and chemical analysis. The temperature behavior and hydrogen-accumulating properties of mechanocomposites are studied. During mechanical activation of Ti and Mg, liquid hydrocarbons decay, metastable nanocrystalline titanium carbohydride Ti(C,H)x and magnesium hydride β-MgH2 are formed, respectively. The Ti(C,H)x and MgH2 formation mechanisms during mechanical activation are deformation ones and are associated with stacking faults accumulation, and the formation of face-centered cubic (fcc) packing of atoms. Metastable Ti(C,H)x decays at a temperature of 550°C, the partial reverse transformation fcc → hcp occurs. The crystalline defect accumulation (nanograin boundaries, stacking faults), hydrocarbon destruction, and mechanocomposite formation leads to the enhancement of subsequent magnesium hydrogenation in the Sieverts reactor.