A composite polycrystal contains polycrystalline diamond formed of diamond grains that are directly bonded mutually, and compressed graphite dispersed in the polycrystalline diamond.

Methods of forming composite particles include forming a source material over a plurality of nucleation cores and forming a catalyst material over the source material. Compositions of matter include a plurality of composite particles, each particle of the plurality comprising a plurality of nucleation cores, a source material disposed over the nucleation cores, and a catalyst material disposed over the source material. Methods of forming earth-boring tools include forming a plurality of composite particles, combining the plurality of composite particles with a plurality of grains of hard material, and catalyzing the formation of inter-granular bonds between the composite particles and the grains of hard material to faun a polycrystalline material. The plurality of in situ nucleated grains of hard material and the plurality of grains of hard material may be interspersed and inter-bonded.

Roller cutters comprise a diamond-bonded body joined to an infiltration substrate. An extension is joined to the substrate and includes first section having a diameter sized the same as the substrate, and an integral second section having a diameter smaller than the substrate. The extension is joined to the substrate during an HPHT process. The first section has a thickness greater than that of the infiltration substrate. The second section has an axial length greater than the combined thickness of the substrate and the first section. The extension has a strength and/or toughness greater than the substrate as a result of its material composition, e.g., the amount of binder phase material and/or the size of hard phase material. The roller cutter is rotatably disposed within a pocket internal cavity, wherein the pocket is attached to a

Luminescent diamond is made by subjecting a volume of diamond grains to high-pressure/high-temperature conditions with or without a catalyst to cause the grains to undergo plastic deformation to produce nitrogen vacancy defects in the diamond grains, increasing the luminescent activity/intensity of the resulting diamond material. The consolidated diamond material may be further treated to further increase luminescent activity/intensity, which treatment may comprise reducing the consolidated diamond material to diamond particles, heat treatment in vacuum, and air heat treatment, which reducing process further increases luminescent activity/intensity. The resulting luminescent diamond particles display a level of luminescence intensity greater than that of conventional luminescent nanodiamond, and may be functionalized for use in biological applications.

A method of making polycrystalline diamond material includes providing a fraction of diamond particles or grains and a sintering additive, the sintering additive comprising a carbon source of nano-sized particles or grains, forming the diamond particles and sintering additive into an aggregated mass, consolidating the aggregated mass and a binder material to form a green body, and subjecting the green body to conditions of pressure and temperature at which diamond is more thermodynamically stable than graphite and for a time sufficient to consume the sintering additive, sintering it and forming polycrystalline diamond material that is thermodynamically and crystallographically stable and is substantially devoid of any nano-structures.

A method of forming a polycrystalline diamond comprises derivatizing a nanodiamond to form functional groups, and combining the derivatized nanodiamond with a microdiamond having an average particle size greater than that of the derivatized nanodiamond, and a metal solvent-catalyst. A polycrystalline diamond compact is prepared by adhering the polycrystalline diamond to a support, and an article such as a cutting tool may be prepared from the polycrystalline diamond compact.

An electrode comprising synthetic high-pressure high-temperature diamond material, the diamond material comprising a substitutional boron concentration of between 1×10.sup.20 and 5×10.sup.21 atoms/cm.sup.3 and a nitrogen concentration of no more than 10.sup.19 atoms/cm.sup.3. The electrode has a ΔE.sub.3/4-1/4 as measured with respect to a saturated calomel reference electrode in an aqueous solution containing 0.1 M KNO.sub.3 and 1 mM of Ru(NH.sub.3).sub.6.sup.3+ selected any of less than 70 mV, less than 68 mV, less than 66 mV, and less than 64 mV, and/or a peak to peak separation ΔE.sub.p as measured with respect to a saturated calomel reference electrode in an aqueous solution containing 0.1 M KNO.sub.3 and 1 mM of Ru(NH.sub.3).sub.6.sup.3+ selected any of less than 70 mV, less than 68 mV, less than 66 mV, and less than 64 mV.

Polycrystalline diamond constructions are formed from a mixture of diamond grains including a first volume of fine-sized diamond grains, and a second volume of coarse-sized diamond grains. The fine-sized diamond grains are partially graphitized, and the coarse-sized diamond grains are not graphitized. The mixture of diamond grains is subjected to high pressure/high temperature sintering process conditions in the presence of a sintering aid thereby forming polycrystalline diamond. Contact areas between coarse-sized diamond grains in the polycrystalline diamond construction are substantially free of graphite.

A diamond polycrystal includes diamond grains, the diamond polycrystal including a cubic diamond and a 6H type hexagonal diamond, wherein the cubic diamond and the 6H type hexagonal diamond exist in the same or different diamond grains, and a ratio Ab.sub.1/Ab.sub.2 is more than or equal to 0.4 and less than or equal to 1, Ab.sub.1 representing a maximum value of absorption in a range of more than or equal to 1200 cm.sup.−1 and less than or equal to 1300 cm.sup.−1 in an infrared absorption spectrum, Ab.sub.2 representing a maximum value of absorption in a range of more than or equal to 1900 cm.sup.−1 and less than or equal to 2100 cm.sup.−1.

A superabrasive compact and a method of making the superabrasive compact are disclosed. A method of making a superabrasive compact comprises steps of providing a plurality of superabrasive particles having a particle size distribution with a first ratio (d50)/(d50 principle particles) ranging from about 0.86 to about 0.92; providing a support to the plurality of superabrasive particles; and subjecting the support and the plurality of superabrasive particles to conditions of an elevated temperature and pressure suitable for producing the polycrystalline superabrasive compact.