S. V. Kidalov

Fullerenes catalyze the graphite-diamond phase transition

The effect of fullerenes on the graphite-diamond phase transition was experimentally studied. Adding a catalytic amount of fullerenes to graphite during the diamond synthesis at relatively low pressures (4.5–5.5 GPa) and temperatures (about 1200°C) increases the percentage graphite to diamond conversion by a factor of 1.8 as compared to the case of an initial charge containing only graphite or fullerene. Adding fullerene to graphite allows the pressure and temperature of the synthesis to be decreased.

Electron spin resonance detection and identification of nitrogen centers in nanodiamonds

Individual nitrogen centers N0 and nitrogen pairs N2+ have been detected and identified in natural diamond nanocrystals by means of the high-frequency electron spin resonance method. The N0 nitrogen centers have been observed in synthetic diamond nanocrystallites with a size of less than 10 nm produced by high-temperature high-pressure sintering of detonation nanodiamonds. Thus, the possibility of the stable state of impurity nitrogen atoms in diamond nanoparticles has been demonstrated.

Electron Paramagnetic Resonance Detection of the Giant Concentration of Nitrogen Vacancy Defects in Sintered Detonation Nanodiamonds

A giant concentration of nitrogen vacancy defects has been revealed by the electron paramagnetic resonance (EPR) method in a detonation nanodiamond sintered at high pressure and temperature. A high coherence of the electron spins at room temperature has been observed and the angular dependences of the EPR spectra indicate the complete orientation of the diamond system.

Effect of carbon materials on the graphite-diamond phase transition at high pressures and temperatures

Experimental data are used in an attempt to unravel the mechanism underlying the effect of modification of a graphite blend by fullerenes on the diamond synthesis at high pressures and temperatures in the presence of metal catalysts. Diamonds have been synthesized under different conditions in a wide range of temperatures and at different pressures, and the effects of blend modification by fullerenes and by addition of natural microcrystalline diamonds to a blend on the diamond synthesis at high pressures and temperatures have been compared.

Static synthesis of microdiamonds from a charge containing nanodiamonds

The effect of detonation nanodiamonds (DNDs) [5] on the graphite-diamond phase transition at high pressures and temperatures has been experimentally studied. It is established that adding DNDs to a graphite-based charge for the diamond synthesis provides for a ∼1.4 times higher conversion of graphite into diamond even at relatively low pressures (4.5–5.5 GPa) and temperatures (1250–1500°C). DND additives also modify the size distribution of microcrystalline diamonds.

Growth of diamond microcrystals by the oriented attachment mechanism at high pressure and high temperature

For the first time it has been experimentally shown that a powder of detonation nanodiamonds (DND) and a saturated acyclic hydrocarbon, mono- or dibasic alcohol, used as the reaction mixture after treatment at high pressures (5–8 GPa) and high temperatures (1300–1800°C) results in the formation of diamond single crystals up to 15 micron in size. The Raman spectrum indicates that the diamonds have a perfect of crystal structure. It has been suggested that the oriented attachment mechanism is responsible for growth of micrometer-size diamond single crystals out of DND particles with sizes of about 5 nm under these technological conditions.

Properties of copper-detonation nanodiamond composites obtained by spray drying

Nanostructural copper-detonation nanodiamond (DND) composites have been obtained by the method of spray drying. The technological process consists in spraying and drying a mixture of an aqueous copper salt solution and DND suspension, followed by thermal treatment in a reductive atmosphere. The DND content in copper powder was varied from 0.5 to 5.0 mass %. The average DND particle size in suspension was 4–6 nm. Copper-DND nanocomposite powders consist of nearly spherical particles with average size within 20–30 μm. Composition and structure of obtained materials have been studied.

First observation of optical radiation from fullerenes in the gas phase

Optical radiation of C60 fullerenes in the gas phase was observed. The observed emission line λ=258 nm is identified with an electronic transition into the ground state hg→hu in C60.

The Effect of Water Complexes on the Parameters of Glow Discharge in Argon-Hydroxyl Mixtures

Experimental data are presented that demonstrate the dependence of the glow discharge parameters in argon-hydroxyl mixtures, including the UV emission efficiency, stability, and duration of the discharge, on the working mixture preparation conditions. Principles allowing the preparation of optimum inert gas-hydroxyl mixtures are established. The main point is to suppress the possible formation of water and/or hydroxyl complexes capable of hindering the realization of optimum conditions for the 306.4 nm OH resonance band excitation in the discharge stage.

Synthesis and properties of superhard crystalline materials in boron-carbon-nitrogen system

The possibility of creating single-crystalline materials in the boron-carbon-nitrogen system has been studied. The thermal conductivity of composites obtained by sintering a mixture of natural microcrystalline diamond powder with cubic boron nitride at high pressures (up to 7 GPa) and high temperatures (up to 2600°C) has been measured. To within sensitivity of the X-ray diffraction, no new C-N and/or B-C-N compounds are formed at the interphase boundaries in the system under consideration.