Heat-resistant composite diamond sintered product and method for production thereof

Abstract

Disclosed is a heat-resistant diamond composite sintered body, which is prepared by sintering an ultrafine-grain synthetic diamond powder having an average grain size of 200 nm or less, without using a sintering aid. The composite sintered body comprises a diamond crystal and a minute amount of non-diamond carbon as a product, and has a Vickers hardness of 85 GPa or more. The composite sintered body is produced by a method comprising enclosing in a Ta or Mo capsule a synthetic diamond powder having an average grain size of 200 nm or less, and heating and pressurizing using an ultrahigh-pressure synthesizing apparatus under thermodynamically stable conditions including a temperature of 2100° C. or more and a pressure of 7.7 GPa or more.

1 . A heat-resistant diamond composite sintered body prepared by sintering an ultrafine-grain synthetic diamond powder having an average grain size of 200 nm or less, by use of an ultrahigh-pressure synthesizing apparatus through static compression process without using a sintering aid, said composite sintered body comprising a diamond crystal and a minute amount of non-diamond carbon as a product, and having a Vickers hardness of 85 GPa or more.  
     
     
         2 . A method of producing the heat-resistant diamond composite sintered body as defined in  claim 1 , comprising: 
 enclosing a synthetic diamond powder having an average grain size of 200 nm or less, in a capsule made of Ta or Mo;    placing the capsule in a pressure medium; and    heating and pressurizing the capsule under thermodynamically stable conditions including a temperature of 2100° C. or more and a pressure of 7.7 GPa or more, by use of an ultrahigh-pressure synthesizing apparatus through static compression process.