Stock material or miscellaneous articles – Coated or structually defined flake – particle – cell – strand,... – Particulate matter
Patent
1989-06-20
1991-12-10
Lesmes, George F.
Stock material or miscellaneous articles
Coated or structually defined flake, particle, cell, strand,...
Particulate matter
423446, 428408, 501 86, B32B 900, C30B 2904
Patent
active
050717081
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates to a composite diamond grain composed of a heat-resistant grain and diamond crystals deposited on the surface of the grain and obtained by the vapor-phase method and to a method for the production thereof.
BACKGROUND ART
Heretofore, natural diamond, synthetic diamond grains produced from carbonaceous substances as raw material by the ultra-high pressure method and having their auto-morphic shape, and grains obtained by grinding such diamond have been generally used as diamond grains for grinding and abrasion.
Recently, the vapor-phase method for synthesis of diamond has been developed. Various procedures for carrying out this method have been disclosed.
The inventors formerly filed PCT/JP 88/00299 relating to a composite diamond grain composed of a ceramic or metal grain having a diameter equal to or less than 30 .mu.m as a nucleus and a vapor-phase method crystal diamond enclosing the grain therewith. The nucleus of the composite diamond grain involved in said application has a diameter of 30 .mu.m at most and has conical projections and rectangular faces and square faces on the grain surface and, therefore, has restrictions on use. To expand the uses of the composite diamond grain, the inventors have continued a study in search for a method capable of producing a composite diamond possessing a nucleus no less than 30 .mu.m in diameter and have accomplished the present invention.
DISCLOSURE OF INVENTION
This invention relates to a composite diamond grain composed of a heat-resistant grain and discrete diamond crystals deposited as dispersed on the surface of the grain or diamond crystal films deposited on the surface of the grain and to a method for the production thereof. This invention further relates to a method for the treatment of tantalum to be used for the hot filament vapor-phase method without any anxiety about the possibility of embrittlement by hydrogen.
BRIEF DESCRIPTION OF DRAWINGS
FIG. 1 is a scanning electron micrograph (SEM) illustrating at 1,000 magnifications a composite diamond grain of this invention produced in Example 1.
FIG. 2 is an SEM illustrating at 5,000 magnifications the composite diamond grain mentioned above.
FIG. 3 is an SEM illustrating at 150 magnifications a composite diamond grain produced by the method of this invention and composed of a heat-resistant grain and diamond crystal films deposited on the entire surface of the grain.
FIG. 4 is a diagram illustrating an apparatus for the synthesis of diamond by the vapor-phase method and concurrently for the treatment of preventing a tantalum filament from embrittlement by hydrogen.
BEST MODE FOR CARRYING OUT THE INVENTION
First, a composite diamond grain composed of a heat-resistant grain and discrete diamond crystal particles deposited as dispersed on the surface of the grain, and a method for the production thereof will be described.
As the material for the heat-resistant grain to be used in the composite diamond grain, diamond and such heat-resistant metallic and ceramic substances as W, Co, Ta, WC, SiC, TiC, ZrO.sub.2, Cr.sub.2 O.sub.3, TaN, ZrN, Si.sub.3 N.sub.4, and etc. are useful. The size of the heat-resistant grain of such a substance is no less than 10 .mu.m, preferably no less than 30 .mu.m.
Though the upper limit of the size of the heat-resistant grain is not specifically defined, it is properly about 300 .mu.m for the purpose of permitting uniform dispersion and deposition of discrete diamond crystals on the heat-resistant grain. The size of this grain is adjusted by such means as comminution or classification.
The diamonds deposited as dispersed on the surface of the heat-resistant grain are very minute, discrete diamond particles. The size of most of the minute particles is in the range of 0.1 to 100 .mu.m.
The term "diamond crystals" as used in the present specification refers to all crystals including single crystals, aggregates of single crystals, and polycrystals.
The "dispersed and deposited diamond crystals" mentioned above are spherical crystals whos
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Fujimaki Takashi
Hirose Yoichi
Komaki Kunio
Yanagisawa Masaaki
Brown Christopher
Hirose Yoichi
Lesmes George F.
Showa Denko K.K.
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