A. N. Sokolov

Novel hybrid ultrahard material

A novel hybrid ultrahard polycrystalline composite material has been produced by the reinforcement of the polycrystalline diamond composite thermostable material with a CVD grown polycrystalline diamond. It has been found that a thermal treatment of a polycrystalline diamond grown at high pressure ensures an increase of the CVD diamond hardness from 77 to 140 GPa. Tests of drilling tools have shown that in turning granite of the XI drillability index the wear intensity of rock destruction elements of the hybrid ultrahard material is lower than that of rock destruction elements of polycrystalline diamond composite thermostable material by a factor of 14.

Structure and physico-mechanical properties of CVD diamonds of various crystalline perfections in the hybridite material

A comparison study has been conducted of the substructure of samples of CVD diamonds of various crystalline perfections in the hybridite material produced at high pressures and temperatures. The material thermostability and hardness variation as a result of the formation of a polycrystalline shell of diamond thermostable composite material around a CVD diamond at high pressure and temperature have been examined. Based on the data obtained on the efficiency of tools from hybridite with CVD diamonds of various structural perfections, the most efficient applications of tools have been recommended.

Structure and hardness of octahedral natural diamond single crystals depending on the HPHT treatment conditions

The structure evolution of octahedral natural diamond single crystals has been studied depending on the HPHT treatment using Raman scattering and infrared spectroscopy. It has been found that the formation of a polycrystalline diamond capsule around a single crystal at p = 8 GPa and T = 1500°C gives rise to a combined structural-stressed state in the single crystal due to its plastic strain. This state has been manifested by a significantly (more than double) broadening of the characteristic line of diamond (1332 cm−1) in the Raman spectrum and the increase of a single crystal hardness from 105 to 120 GPa.

Diamond polycrystalline composite material with dispersion-hardened nickel-based additive

A diamond polycrystalline composite material with improved physico-mechanical characteristics has been obtained at high pressure and temperature using nickel and cobalt powders and tungsten carbide nanopowder as sintering aids. Samples of this material reinforced with CVD polycrystalline diamond at high pressure and temperature have been manufactured.

Special features of self-organization of ultradispersed diamond at high pressures and temperatures

The behavior of ultradispersed diamond (UDD) particles at high pressure and temperature has been studied experimentally. Products from UDD only, from UDD with boron added, from UDD with boron and the liquid phase added have been analyzed. The possibility to obtain bulk well-faceted single crystals in sizes up to 10 μm as a result of the self-organization of UDD nanoparticles of size ≈ 5 nm in a liquid phase, which does not solve carbon, has been found for the first time.

Special features of structural transformations of fullerite C60 at high pressures and temperatures

The results of experimental studies of special features of fullerite C60 structural transformations at high pressures and temperatures are discussed. It has been found that under the action of a pressure of ∼ 7.0 GPa and a temperature of 2000–2200 K on fullerite graphite forms and with the liquid phase present diamond forms.

Novel Wear-Resistant Superhard Diamond Composite Polycrystalline Material

Using the activated HPHT-sintering of diamond powders with addition of n-layered graphene of the N002-PDR grade, was produced a novel superhard composite polycrystalline material that does not contain free silicon and has a strength by 35% higher and wear-resistance by 7 times higher than samples produced without addition of graphene.

Phase transformations of n-layer graphenes into diamond at high pressures and temperatures

The effect of high pressure (7.7 GPa) and temperature (1700°C) on the phase transformations of both graphene plates with a high degree of crystallinity having less than four layers and thickness not exceeding 5 nm and powders of multilayer graphenes (of 10–20 monolayers) and 8–12 nm in thickness was experimentally studied in the presence of carbon solvents (Ni–Mn alloy, iron). Factors both contributing and inhibiting the diamond synthesis from graphene in the presence of the solvents for carbon are defined. It is shown that the transformation of multilayer graphenes into diamond at high pressure and temperature by a two-stage scheme of the diamond synthesis (i.e., after three-dimensional structural ordering of graphene at the first stage) is preferable.

Structure and properties of impact diamonds from the Popigai Deposit and polycrystals based on them

Properties of impact diamonds from the Popigai Deposit have been studied in a free state and in a composition of a compact. Raman spectra have been taken of the initial micron powders and polycrystals HP-HT sintered both in the presence of sintering aids and without them. Hardness, HV, of sintered polycrystals have been found, structural variations in diamond crystal lattice depending on the sintering conditions have been studied.

Hardness of single-crystal CVD diamond and phase transformations in it on indentation

Hardness of single-crystal CVD diamond placed into a shell of a diamond composite thermostable material produced at high pressures and temperatures as well as structural variations in diamond during indentation have been studied.