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ABSTRACT: Microcrystalline boron-doped diamond powders consisting of octahedrally faceted crystals have been synthesized in the C-H-B
system at a pressure of 8 GPa and temperatures above 2000 K. The presence of boron has been shown to reduce the parameters
of diamond synthesis compared to the binary system C-H (naphthalene). One possible reason for the reduction in synthesis parameters
is the formation of less perfect graphite in the boron system in an intermediate step of diamond synthesis. At B/(C + B) ratios
of about 5–10 at % in the C-H-B (naphthalene + boron) system, superconducting diamond microcrystals have been synthesized.
Inorganic Materials 10/2006; 42(11):1198-1204. · 0.41 Impact Factor
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ABSTRACT: Dense boron samples with a glassy structure have been prepared for the first time by high-pressure sintering of amorphous
boron powder at temperatures from 750 to 1100 K. Analysis of the mechanical properties of boron samples sintered at pressures
from 2 to 8 GPa and different temperatures indicates that sintering proceeds most effectively near 750 K. Purification of
amorphous boron in water is shown to be effective in removing products of boron oxidation in air.
Inorganic Materials 04/2006; 42(5):479-483. · 0.41 Impact Factor
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ABSTRACT: The design of a high-pressure cell for short-term (5–20 s) experiments in a toroid-type high-pressure chamber at a pressure of 8 GPa and a temperature up to 3100 K is described. The dependence of the temperature in the high-pressure cell on the electric power supplied to the heater is constructed on the basis of data on the incongruent melting of silicon carbide (SiC) under pressure.
Instruments and Experimental Techniques 02/2004; 47(2):276-278. · 0.36 Impact Factor
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ABSTRACT: Superhard polycrystalline diamond material consisting of crystallites less than 20 m in size and containing less than 5 wt % B4C is synthesized in the graphite–B4C system at 2600–2800 K and 8–9 GPa. In the Raman spectrum of this material, the main band (1332 cm–1) is shifted to lower frequencies by 40 cm–1, typical of heavily boron-doped diamond films. Based on experimental data, a mechanism is proposed for the transformation of graphite into polycrystalline diamond at temperatures between the melting points of the B4C–diamond and B4C–graphite eutectics.
Inorganic Materials 01/2004; 40(9):932-936. · 0.41 Impact Factor
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ABSTRACT: Microcrystalline powders of boron-doped diamond were produced in the C–H–B system under a pressure of 8 GPa and at a temperature of more than 2000 K. The presence of boron in the C–B–H system was shown to decrease the temperature–pressure parameters for diamond synthesis compared with those for the binary C–H system (naphthalene). A decrease in the parameters for synthesis in the system with boron may be due to the formation of graphite with less perfect crystal structure during an intermediate stage of diamond formation. Superconducting diamond microcrystals are synthesized in the C–H–B system with boron content of about 5–10 at% in a mixture with naphthalene. Superconductivity below 3.5 K in boron-doped diamond powder is detected in AC magnetic susceptibility measurements.
Science and Technology of Advanced Materials.
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ABSTRACT: Carbonado-like polycrystalline diamond was synthesized in the non-metallic B4C–graphite system at a high pressure of 8–9 GPa and very high temperatures, about 2600–2800 K. The Vickers hardness of the polycrystalline diamond containing less than 5 mass% of B4C was 70–120 GPa at the indenter load 4.9 N. The experimental evidence suggests that the graphite-to-diamond transformation starts in the temperature range between the B4C–graphite–liquid and B4C–diamond–liquid eutectic temperatures. The presence of a volatile component, boric acid, in the starting B4C–graphite system breaks the polycrystalline microstructure of the diamond material leading to the formation of separate diamond microcrystals. In addition, we demonstrate that the toroid-type high-pressure chamber can be used for experiments at the temperature up to 2800–3100 K.
Diamond and Related Materials.
