Pulsed electric field induced diamond synthesis from carbon nanotubes with solvent catalysts

Spark plasma sintering (SPS) was used to synthesize diamond from multiwalled carbon nanotubes (MWCNTs) with Fe35Ni powders as solvent catalysts. The MWCNTs/Fe35Ni mixtures were spark plasma sintered at various conditions. The microstructures and diamond phase were analyzed by using X-ray diffraction, Raman spectroscopy, scanning electron microscopy, and transmission electron microscope techniques. Experimental results showed that the diamond crystals can be synthesized from MWCNTs/Fe35Ni by using the SPS at lower temperature of 1200 °C under very low pressure of 70 MPa. Well-crystallized cubic diamonds consisted of mono-crystals and poly-crystals exhibiting particle sizes ranged from 10 to 40 μm. The Fe35Ni catalysts achieved an effective enhancement for diamond conversion from MWCNTs during the SPS. A model was also proposed to describe the diamond growth and revealed as a layer-by-layer growth mechanism.

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► Diamond crystals synthesized at 1200 °C, 70 MPa by SPS.
► Layer by layer structures of the synthesized diamond crystals.
► TEM and XRD identifications of the diamond crystals.
► The diamond growth model in the SPS method.