Direct transformation of cubic diamond to hexagonal diamond

He, Hongliang; Sekine, Toshimori; Kobayashi, Taizo

doi:10.1063/1.1495078

Cited by 94 publications

(54 citation statements)

References 21 publications

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“…The spectra of the recovered sample exhibits two broad peaks centered at 1,581 and 1,355 cm Ϫ1 , respectively, which are characteristics of carbon with a very small particle size (1,11). Such spectroscopic characteristics are very similar to those of glassy carbon with a significant ratio of sp 3 ͞sp 2 bonding (13), but remarkably different from those of the starting nanotube, single-crystal graphite, or cubic and hexagonal diamond (7). The 1,355-cm Ϫ1 peak of glassy carbon is much stronger and sharper than that of the recovered hexagonal phase (1).…”

mentioning

confidence: 68%

“…The 1,355-cm Ϫ1 peak of glassy carbon is much stronger and sharper than that of the recovered hexagonal phase (1). It is also clear that our hexagonal form is not hexagonal diamond, since it should only have a single Raman active mode at Ϸ1,310 cm Ϫ1 , representing the occurrence of the sp 3 -hybridized bonds (6,7,12). We therefore conclude that this is an additional highpressure carbon phase.…”

mentioning

confidence: 79%

“…, a characteristic signature of hexagonal diamond (6,7). So far, x-ray diffraction data suggest the existence of the so-called hexagonal diamond (2, 4), but Raman spectroscopic studies performed at similar experimental conditions indicate that the observed hexagonal form is a high-pressure polymorph of carbon (1,8,12).…”

mentioning

confidence: 99%

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A quenchable superhard carbon phase synthesized by cold compression of carbon nanotubes

Wang

Zhao

Tait

et al. 2004

Proc. Natl. Acad. Sci. U.S.A.

166

132

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A quenchable superhard high-pressure carbon phase was synthesized by cold compression of carbon nanotubes. Carbon nanotubes were placed in a diamond anvil cell, and x-ray diffraction measurements were conducted to pressures of Ϸ100 GPa. A hexagonal carbon phase was formed at Ϸ75 GPa and preserved at room conditions. X-ray and transmission electron microscopy electron diffraction, as well as Raman spectroscopy at ambient conditions, explicitly indicate that this phase is a sp 3 -rich hexagonal carbon polymorph, rather than hexagonal diamond. The cell parameters were refined to a 0 ‫؍‬ 2.496(4) Å, c0 ‫؍‬ 4.123(8) Å, and V0 ‫؍‬ 22.24(7) Å 3 . There is a significant ratio of defects in this nonhomogeneous sample that contains regions with different stacking faults. In addition to the possibly existing amorphous carbon, an average density was estimated to be 3.6 ؎ 0.2 g͞cm 3 , which is at least compatible to that of diamond (3.52 g͞cm 3 ). The bulk modulus was determined to be 447 GPa at fixed Kϵ4, slightly greater than the reported value for diamond of Ϸ440 -442 GPa. An indented mark, along with radial cracks on the diamond anvils, demonstrates that this hexagonal carbon is a superhard material, at least comparable in hardness to cubic diamond.

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confidence: 68%

mentioning

confidence: 79%

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A quenchable superhard carbon phase synthesized by cold compression of carbon nanotubes

Wang

Zhao

Tait

et al. 2004

Proc. Natl. Acad. Sci. U.S.A.

166

132

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“…However, these exceptional properties have not been proven experimentally because of the inability to synthesize lonsdaleite as a pure phase. It has been reported to form during static compression of graphite 3,9,13,[15][16][17][18] ; highpressure-high-temperature treatment of powdered diamond, graphite and amorphous carbon 19 ; explosive detonation and shock compression of graphite 11,20 and diamond 21 ; and chemical vapour deposition of hydrocarbon gases 22 ; however, in all cases the synthesis product also contained cubic diamond, graphite or both.…”

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confidence: 99%

Lonsdaleite is faulted and twinned cubic diamond and does not exist as a discrete material

et al. 2014

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Lonsdaleite, also called hexagonal diamond, has been widely used as a marker of asteroidal impacts. It is thought to play a central role during the graphite-to-diamond transformation, and calculations suggest that it possesses mechanical properties superior to diamond. However, despite extensive efforts, lonsdaleite has never been produced or described as a separate, pure material. Here we show that defects in cubic diamond provide an explanation for the characteristic d-spacings and reflections reported for lonsdaleite. Ultrahigh-resolution electron microscope images demonstrate that samples displaying features attributed to lonsdaleite consist of cubic diamond dominated by extensive {113} twins and {111} stacking faults. These defects give rise to nanometre-scale structural complexity. Our findings question the existence of lonsdaleite and point to the need for re-evaluating the interpretations of many lonsdaleite-related fundamental and applied studies.

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“…Such amount of shift is also observed in hexagonal diamond with peak broadening. 37,38 At the earlier stage of the growth in our case, such hexagonal diamonds might be grown. On the other hand, the peak shift is not observed in the diamond layers grown after 5 h. More detailed analysis, e.g.…”

Section: Micro-raman Spectrum Of the Grown Particles At Various Condimentioning

confidence: 99%

Synthesis of diamond fine particles on levitated seed particles in a rf CH4/H2 plasma chamber equipped with a hot filament

Shimizu

Thomas

et al. 2012

Journal of Applied Physics

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The first successful growth of diamond layers on levitated seed particles in CH 4 /H 2 plasma is presented. The particles were grown in an rf CH 4 /H 2 plasma chamber equipped with a tungsten hot filament. The seed diamond particles injected in a plasma are negatively charged and levitated under the balance of several forces, and diamond chemical vapor deposition takes place on them. The SEM images show that the crystalline structures are formed after the coagulation of islands. The micro-Raman spectroscopy of the particle grown after several hours show the clear peak assigned to diamond.

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Direct transformation of cubic diamond to hexagonal diamond

Cited by 94 publications

References 21 publications

A quenchable superhard carbon phase synthesized by cold compression of carbon nanotubes

A quenchable superhard carbon phase synthesized by cold compression of carbon nanotubes

Lonsdaleite is faulted and twinned cubic diamond and does not exist as a discrete material

Synthesis of diamond fine particles on levitated seed particles in a rf CH4/H2 plasma chamber equipped with a hot filament

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