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.

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 polycrystalline diamond structure comprises a first region and a second region adjacent the first region, the second region being bonded to the first region by intergrowth of diamond grains. The first region comprises a plurality of alternating strata or layers, each or one or more strata or layers in the first region having a thickness in the range of around 5 to 300 microns. The polycrystalline diamond (PCD) structure has a diamond content of at most about 95 percent of the volume of the PCD material, a binder content of at least about 5 percent of the volume of the PCD material, and one or more of the layers or strata in the first region comprise and/or the second region comprises diamond grains having a mean diamond grain contiguity of greater than about 60 percent and a standard deviation of less than about 2.2 percent. There is also disclosed a method of making such a polycrystalline diamond structure.

A method of forming polycrystalline diamond comprised placing a plurality of graphene nano-platelets into a capsule; and subjecting the platelets to a pressure of around 10 GPa to around 20 GPa and a temperature of around 1600 degrees Celsius to around 3000 degrees Celcius to convert the graphene platelets to nano-polycrystalline diamond. There is also disclosed a polycrystalline super hard construction comprising a polycrystalline diamond region comprising polycrystalline diamond material formed according to said method.

A polycrystalline diamond structure comprises a first region and a second region adjacent the first region, the second region being bonded to the first region by intergrowth of diamond grains. The first region comprises a plurality of alternating strata or layers, each or one or more strata or layers in the first region having a thickness in the range of around 5 to 300 microns. The polycrystalline diamond (PCD) structure has a diamond content of at most about 95 percent of the volume of the PCD material, a binder content of at least about 5 percent of the volume of the PCD material, and one or more of the layers or strata in the first region comprise and/or the second region comprises diamond grains having a mean diamond grain contiguity of greater than about 60 percent and a standard deviation of less than about 2.2 percent. There is also disclosed a method of making such a polycrystalline diamond structure.