Polycrystalline diamond

Abstract

An object is to provide polycrystalline diamond applicable to diverse applications; and a water jet orifice, a stylus for gravure printing, a scriber, a diamond cutting tool, and a scribing wheel that include such polycrystalline diamond. This object is achieved by polycrystalline diamond obtained by converting and sintering non-diamond carbon under an ultrahigh pressure and at a high temperature without addition of a sintering aid or a catalyst, wherein sintered diamond grains constituting the polycrystalline diamond have an average grain diameter of more than 50 nm and less than 2500 nm and a purity of 99% or more, and the diamond has a D90 grain diameter of (average grain diameter+average grain diameter×0.9) or less.

1 . Polycrystalline diamond obtained by converting and sintering non-diamond carbon under an ultrahigh pressure and at a high temperature without addition of a sintering aid or a catalyst, wherein sintered diamond grains constituting the polycrystalline diamond have an average grain diameter of more than 50 nm and less than 2500 nm and a purity of 99% or more, and the diamond has a D90 grain diameter of (average grain diameter+average grain diameter×0.9) or less. 
     
     
         2 . The polycrystalline diamond according to  claim 1 , wherein the sintered diamond grains have a D90 grain diameter of (average grain diameter+average grain diameter×0.7) or less. 
     
     
         3 . The polycrystalline diamond according to  claim 1 , wherein the sintered diamond grains have a D90 grain diameter of (average grain diameter+average grain diameter×0.5) or less. 
     
     
         4 . The polycrystalline diamond according to  claim 1 , wherein the polycrystalline diamond has a hardness of 100 GPa or more. 
     
     
         5 . The polycrystalline diamond according to  claim 1 , wherein the non-diamond carbon is a carbon material having a graphite-type layer structure. 
     
     
         6 . A water jet orifice comprising the polycrystalline diamond according to  claim 1 . 
     
     
         7 . The water jet orifice according to  claim 6 , wherein an interior surface of an orifice bore through which water jet fluid passes, the bore being formed in the polycrystalline diamond, has a surface roughness Ra of 300 nm or less. 
     
     
         8 . The water jet orifice according to  claim 6 , wherein the orifice bore formed in the polycrystalline diamond has a diameter of 10 μm or more and 500 μm or less. 
     
     
         9 . The water jet orifice according to  claim 6 , wherein a ratio (L/D) of an orifice level (L) to an orifice bore diameter (D) is 10 to 500, the orifice bore being formed in the polycrystalline diamond. 
     
     
         10 . The water jet orifice according to  claim 6 , wherein the orifice bore formed in the polycrystalline diamond has a diameter of more than 500 μm and 5000 μm or less. 
     
     
         11 . The water jet orifice according to  claim 6 , wherein a ratio (L/D) of an orifice level (L) to an orifice bore diameter (D) is 0.2 to 10, the orifice bore being formed in the polycrystalline diamond. 
     
     
         12 . A stylus for gravure printing comprising the polycrystalline diamond according to  claim 1 . 
     
     
         13 . A scriber comprising the polycrystalline diamond according to  claim 1 . 
     
     
         14 . The scriber according to  claim 13 , wherein a cutting face at a tip of the scriber has a shape of a polygon including three or more edges and the edges, in part or entirety, of the polygon are used as a blade. 
     
     
         15 . A diamond cutting tool comprising the polycrystalline diamond according to  claim 1 . 
     
     
         16 . A scribing wheel comprising the polycrystalline diamond according to  claim 1 .