Formation of low-porosity compact diamond ceramics: Synthesis and Raman spectroscopic characterization Original Research Article

Diamond powder has been synthesized by spontaneous crystallization under high static pressure using a Mn-Ni catalyst at 4.5 GPa pressure and 1200 °C. A defined size distribution of the diamond particles has been established through adjustment of the growth period. Chemically modified microcrystalline diamond surfaces have been prepared by boiling in acid solutions. Investigations indicate that the diamond crystals have an octahedron habit with unbroken facets. Raman spectroscopic data show that the prepared diamond powder is pure diamond, without any traces of graphite and other impurities. Second-order Raman-spectra of both, single-crystalline natural diamond and the synthesized microcrystalline form reveal a similar phonon density of states. On the basis of model calculations and comparison with experimental data it is concluded that a polydisperse composition with a dominant size fraction of 28 μm suited best the compact diamond ceramics.