Growth of diamond from fullerene C60 by spark plasma sintering

Abstract

a b s t r a c tThe growth of diamond from fullerene C60 was studied by spark plasma sintering (SPS). The phases and microstructures were analyzed by Raman spectroscopy, Synchrotron X-ray, scanning electron microscopy and transmission electron microscopy. Experimental results show that C60 becomes unstable and can be directly transformed into diamond by SPS under a pressure of 50 MPa at temperatures above 1150 1C, without any catalyst being involved. Polycrystalline diamond crystals with sizes up to 250 mm and transition rate about 30 vol% are obtained at SPS temperature of 1300 1C. The mechanism indicates that the high fraction of sp 3 hybrids in the fullerene C60 and the generated plasmas in the SPS lead to its transformation into diamond at such low temperatures and pressures. The transformation from C60 to diamond is a direct transition process with a structural reconstruction of carbon atoms without intermediate phases being involved.

Strong amorphous carbon prepared by spark‐plasma sintering C60

“…In this study, a series of amorphous carbon bulk materials were prepared through the SPS treatment of fullerene C 60 , and our findings clarified the contradictions of previous studies 8,9 . These amorphous carbons were composed of disordered linked multi‐graphene layers with different sizes and curvatures, and they possessed excellent mechanical properties.…”

“…The representative HRTEM and SAED images of the samples synthesized from various temperatures including 1100, 1300, 1700, and 2000°C are presented in Figure 3A–D. The disordered morphology could be observed directly from the HRTEM in all samples, and we searched many sample areas under the TEM, but we found no evidence for the formation of diamond, which was inconsistent with the previous claim 7,8 . The HRTEM results also revealed the microstructure difference in these amorphous carbon materials.…”

“…Zhang et al 7,8 sintered C 60 with SPS at a pressure in the range of 50-80 MPa and a temperature in the range of 1100-1500°C, and provided somewhat evidence about the formation of diamond after SPS treatment through the transmission electron microscope analysis. However, Hawelek et al 9 also sintered fullerene extract (approximately 70% of C 60 , 28% of C 70 , and 2% of higher fullerenes) with SPS under similar conditions (50 MPa, 1500°C), but they considered that glass-like amorphous carbon material was formed based on the X-ray and neutron diffraction data.…”

Field‐Assisted Sintering Technology/Spark Plasma Sintering: Mechanisms, Materials, and Technology Developments

“…The formation of diamond from fullerene C60 without any catalysts was also possible in FAST/SPS run under moderate pressure of 50-80 MPa at 1150-1300°C with a heating rate of 100°C min À1 in vacuum, i.e., much "milder" conditions than usually required for diamond production. [224,225] Polycrystalline diamond crystals with sizes up to 250 mm and transition rates about 30% were observed. The transformation into diamond takes place by direct reconstruction of sp 3 carbon, which exists as a high fraction in the fullerene.…”

Electrochemical interaction between graphite and molten salts to produce nanotubes, nanoparticles, graphene and nanodiamonds

“…It has been shown by theoretical analysis that sp 3 diamond nucleation from sp 2 carbon is possible inside carbon nanotubes or nanoparticles due to surface tension effects [39] and there have been many attempts to convert carbon nanotubes to diamonds using plasma techniques, laser irradiation, shock waves and plasma sintering [40][41][42] but all these techniques require very high pressures and temperatures as well as metallic catalysts. Non-metallic catalysts, such as alkali carbonates, have also been used although even higher temperatures and pressures are required as well as longer reaction times [43].…”