Stock material or miscellaneous articles – Coated or structually defined flake – particle – cell – strand,... – Particulate matter
Patent
1988-09-28
1992-01-14
Lesmes, George F.
Stock material or miscellaneous articles
Coated or structually defined flake, particle, cell, strand,...
Particulate matter
423446, 427215, 427249, 427255, 4272552, 4272553, 428408, 501 56, C01B 3106, C23C 1622
Patent
active
050809750
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates to composite diamond granules produced by the CVD method using ceramic or metallic particles as a core. The composite diamond granules of this invention can be suitably used as a granular abradant particularly for the abrasion of a surface and are advantageously used in the form of a grindstone obtained by mixing the composite diamond granules with resin, metal, a vitrified binder, and the like and molding the resultant mixture.
BACKGROUND ART
Diamond is the hardest substance known and has been used as a granular abradant. As a means for its manufacture, the ultra-high pressure method has been in use from a long time ago. In recent years, vapor phase methods (hereinafter referred to collectively as "CVD") of synthesizing diamond have been proposed. In CVD, though membrane diamond is produced mostly, granular diamond can be produced under certain conditions of production.
As one of the methods for the production of granular diamond there is a method which comprises preparing as cores minute diamond granules produced by the ultra-high pressure method and causing CVD diamond to be deposited on the periphery of the cores (Japanese Patent Publication SHO 48-32519 and Japanese Patent Public L Disclosure SHO 47-38794).
In the conventional method, the diamond granules used as cores are expensive and these diamond granules are obtained either by crushing large diamond grains or by classifying diamond dust which is produced during the cutting of diamond. These diamond granules are not easily obtained in a shape closely approximating a sphere because of their sharp edges, for example. It has been difficult, therefore, to produce diamond granules having a shape closely approximating a sphere by causing the core diamond described above to grow.
Where a granular abradant is used particularly for polishing the surface of a given object to high smoothness, the individual granules thereof are desired to be those of a shape closely approximating a sphere. Preferably these granules are mainly in a polycrystalline structure such that they reveal new crystal faces incessantly while they are being used for the abrasion.
Further single crystals of diamond are molded together with a substance as a matrix to produce a grindstone. In this case, the single crystals are not retained with ample fastness in the matrix substance. Generally, the fastness of the retention of the single crystals in the matrix is improved by having the surface of these single crystals coated in advance with a layer capable of promoting intimate contact with the matrix or having the single crystals subjected in advance to a surface treatment. For example, the diamond granules for resinoids are coated with nickel (50 to 60% by weight) by the electroless plating method to enhance their ability to make intimate contact with the matrix and improve their anchoring effect within the matrix.
Treatment of this type adds to the production cost of abrasive granules and grindstones. Moreover, since the coating is generously applied, it is difficult to maintain the desirable cutting ability.
An object of this invention is to provide composite diamond granules which are nearly spherical crystalline particles capable of retaining a surface particularly suitable for abrasion, exhibiting a highly desirable abrading ability as abrasive granules, and, on being molded together with a matrix substance to produce a grindstone, manifesting an ability to maintain intimate contact with the matrix substance and, therefore, obviate the necessity for any surface treatment.
DISCLOSURE OF THE INVENTION
To accomplish the object described above, this invention relates to composite diamond granules each comprising a ceramic or metallic granule not more than 30 .mu.m in diameter and a single-crystal or polycrystalline diamond produced by CVD enclosing the ceramic or metallic granule and having an aspect ratio in the range of 1.0 to 1.3.
The aforesaid two types of diamond are aggregates of various microcrystals. These microcrystals include those
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patent: 3630679 (1971-12-01), Angus
patent: 4617181 (1986-10-01), Yazu et al.
patent: 4816286 (1989-03-01), Hirose
patent: 4859493 (1989-08-01), Lemelson
patent: 4919974 (1990-04-01), McCune et al.
patent: 4938940 (1990-07-01), Hirose et al.
patent: 4960643 (1990-10-01), Lemelson
patent: 5023068 (1991-06-01), Jones
Japanese Journal of Applied Physics, vol. 21, No. 4, (1982), S. Matsumoto, et al. [Vapor Deposition of Diamond Particles from Methane] P. L183-L185.
Fujimaki Takashi
Hirose Yoichi
Komaki Kunio
Yamamoto Isamu
Brown Christopher
Lesmes George F.
Showa Denko K. K.
Yoichi Hirose
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