Detailed Structures of Hexagonal Diamond (lonsdaleite) and Wurtzite-type BN

Yoshiasa, Akira; Murai, Yu; Ohtaka, Osamu; Katsura, Tomoo

doi:10.1143/jjap.42.1694

Cited by 48 publications

(32 citation statements)

References 10 publications

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“…The solid circles in Figure 12 represent the positions where a mixture of diamond, lonsdaleite, and graphite was observed, and the open circles represent the positions where only diamond was obtained by high-pressure experiments without a catalyst (Bundy and Kasper, 1967;Yoshiasa et al, 2003;Irifune et al, 2004).…”

Section: P-t Conditions Of Diamond Formation In Ureilitesmentioning

confidence: 99%

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In situ observation, X–ray diffraction and Raman analyses of carbon minerals in ureilites: Origin and formation mechanisms of diamond in ureilites

Nakamuta

Kitajima

Shimada

2016

Journal of Mineralogical and Petrological Sciences

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Carbon minerals in sixteen monomict ureilites which are variable in shock features in olivine were observed in situ by optical microscopy, scanning electron microscopy, X-ray powder diffraction, and Raman analyses. Euhedral blade-like shaped or amoeboid shaped graphite crystals occur in the very low-shock ureilites, not associated with diamond. In the low, medium, and high-shock ureilites, diamond occurs together with graphite. X-ray diffraction and Raman analyses reveal that crystallinity of diamond is relatively well in the low-shock ureilites, although it varies in a wide range in the high-shock ureilites. Diamond formation in the low-shock ureilites occurred as a result of solid-state catalytic transformation of graphite at a pressure lower than 10 GPa, with metallic iron as the catalyst, while diamond in the high-shock ureilites formed by spontaneous transformation of graphite together with the catalytic transformation at a pressure higher than 12 GPa. The relative crystal-axes orientations between graphite (Gr) and diamond (Di) determined by EBSD analyses in the lowshock Y-8448 ureilite is the same as that observed for graphite and diamond in a carbon grain from the highshock Goalpara ureilite. The metallic iron catalyst promoted the sliding and puckering of the hexagonal carbon planes of graphite in the solid-state transformation processes of graphite to diamond after intercalating into its interplanar spaces. It is shown that noble gas systematics in ureilites can be matched with the shock formation origin of diamond in ureilites.

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Section: P-t Conditions Of Diamond Formation In Ureilitesmentioning

confidence: 99%

“…Diamond-formation regions on the pressure-temperature (P-T) phase diagram for elemental carbon (Bundy et al 1961;Bundy 1989;Yoshiasa et al 2003;Irifune et al 2004). T u , estimated temperature of ureilite at the time when the ureilite parent body (UPB) was broken up.…”

Section: Mechanism Of Catalytic Transformation Of Graphite To Diamondmentioning

confidence: 99%

In situ observation, X–ray diffraction and Raman analyses of carbon minerals in ureilites: Origin and formation mechanisms of diamond in ureilites

Nakamuta

Kitajima

Shimada

2016

Journal of Mineralogical and Petrological Sciences

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“…Although a bulk sample of pure hexagonal diamond has not been successfully recovered at the ambient pressure both in nature and experimentally [5][6][7]9], it is of great interest to evaluate its hardness and wear resistance to prove this prediction.…”

Section: Introductionmentioning

confidence: 99%

Wear resistance of nano-polycrystalline diamond with various hexagonal diamond contents

Kurio

Tanaka²,

Sumiya

et al. 2012

J. Superhard Mater.

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“…List of the Young's modulus (E), bulk modulus (B), shear modulus (G), and Poisson's ratio (y) of the ReB 2 compacts synthesized at 5.0 GPa and 1600 8C for 60 min, compared with previous calculated results [21] and in situ high-pressure X-ray diffraction measurements data. [9] E [31] ), but the ionic (ionic Ru-O bonds in RuO 2 [29] ) and metallic bonds (metallic Os-Os, W-W, and Co-W interactions in OsB 2 , [16] WC, and Co 6 W 6 C, [30] respectively) can damage the superhard nature for these hard materials. Therefore, the known superhard materials such as diamond, cBN, B 6 O, and BC 2 N do not possess ionic and metallic bonds.…”

mentioning

confidence: 99%