Compositions: ceramic – Ceramic compositions – Synthetic precious stones
Patent
1993-11-18
1999-01-19
Straub, Gary P.
Compositions: ceramic
Ceramic compositions
Synthetic precious stones
423446, C01B 3106
Patent
active
058613498
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to the field of inorganic chemistry of carbon, and more specifically, to the cubic modification of carbon featuring the properties of a superhard material, and to the process for preparing the material which comprises detonation synthesis of a diamond-bearing burden with subsequent extraction by chemical methods.
When some explosives detonate under the conditions making it possible to preserve the condensed carbon products of the explosion ultradispersive diamond-bearing powders are formed, which possess such specific properties as high dispersivity, presence of defects of carbon structure, developed active surface. These characteristics are varied within wide limits depending on the conditions of preparing the diamond-bearing materials. The particular properties of the diamond-bearing detonation materials define the spheres of the practical application, such as in composite materials and coatings, abrasive or lubricating compositiosn and the like.
BACKGROUND ART
The properties of diamond-bearing materials, obtained with the use of explosion energy, and also the conditions of their synthesis and separation from impurities are known in the art.
A paper (G. A. Adadurov et al, "The physics of Pulse Pressures" pp 44 (74), 1979, No. 4, Papers of All-Union Science-Research Institute of Physical and Radio Engineering Measurements, p. 157) discloses the characteristics of the product obtained in detonation of a mixture of RDX with a carbon material (black or graphite) in a blasting chamber in inert atmosphere. The purified product is a powder with the average particle size 0.05 to 5.0 mom, the average particle size calculated for the unit surface values is 0.04 to 0.08 mcm. The unit surface area is 20 to 42 m.sup.2 /g. The pycnometric density is 3.20 to 3.40 g/cm.sup.3. By the phase composition, the product is a mixture of diamond of a cubic (the lattice parameter a=0.357 nm) and a hexagonal modification (lonsdalite). The size of the coherent scattering region (CSR) of crystallites (i.e. the linear distance between the adjacent defects) is 10 to 12 nm, and the value of microdistortions of the second kind, characterizing the presence of defects, is within the limits 1 to 2.multidot.10.sup.-3. After anealing at 1073 K, the size of CSR was 12 nm, and the value of microdistortions of the second kind was reduced to 0.35.multidot.10.sup.-3. The temperature of the beginning of graphitization is over 1073K. About one fourth of the surface is occupied by carboxyl groups. When heated in vacuum, specimens lose some. 8% of the mass owing to liberation of oxygen, carbon monoxide and carbon dioxide molecules.
The properties of the diamond obtained from the carbon of explosives are described by K. V. Volkov with co-authors (The Physics of Compustion and Explosion, v. 26, No. 3, p, 123, 1990). Synthesis is effected when charges are set off in a blasting chamber in the atmosphere of carbon dioxide and in a water jacket. The particle size of the obtained diamond is 0.3 to 0.06 nm, the CSR size is 4 to 6 nm, the particle shape is round. The pyonometric density is 3.2 g/cm.sup.3. The product contains about 90% diamond, the balance, adsorbed gases. The product start oxidizing at 623 K. After fivehour holding at. 1173K, the degree of graphitization of the diamond is 10%.
Other versions of the method (A. M. Staver et al, The Physics of Combusion and Explosion, V. 20, No. 5, p. 100, 1984 and G. I. Savvakin et al, Proceedings of the USSR Academy of Sciences, V. 282, No. 5, 1985) are based of other or the same explosives in various kinds of atmospheres. The products resulting in this case feature properties similar to those described by K. V. Vollcov with co-authors.
For isolating the end diamond-bearing product, use is made of a complex of chemical operations directed at either dissolving or gasifying the impurities present in the material. The impurities, as a rule, are of the two kinds: non-carbon (metal, oxides, salts, etc.) and nondiamond forms of carbon (graphite, black, amorph
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Klimov Anatoly Valentinovich
Komarov Vitaly Fedorovich
Kozyrev Nikolai Vladimirovich
Petrov Evgeny Anatolievich
Sakovich Gennady Viktorovich
Hendrickson Stuart L.
Nauchno-Proizvodstvennoe Obiedinenie "Altai"
Straub Gary P.
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