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IUGG XXIV General Assembly July 2-13, 2007 Perugia, Italy<br />

(S) - <strong>IASPEI</strong> - International Association of Seismology and Physics of the Earth's<br />

Interior<br />

JSS001 Oral Presentation 1720<br />

Ultrahard nano-polycrystalline diamond: novel material for high-pressure<br />

mineral physics studies<br />

Prof. Tetsuo Irifune<br />

Geodynamics Research Center Ehime University <strong>IASPEI</strong><br />

Hitoshi Sumiya<br />

Since we first reported the synthesis of binderless nano-polycrystalline diamond (NPD) with extremely<br />

high hardness by direct conversion of graphite at high pressure and high temperature (Irifune et al.,<br />

2003; 2004; Sumiya and Irifune, 2004), we have been extensively working to synthesise the NPD with<br />

larger dimensions and higher quality. NPD rods of up to ~5 mm in diameter and ~a few mm thick<br />

without any visible cracks can now be synthesized on a routine basis using large multitnvil apparatus.<br />

We found thus synthesised NPD rod can be polished to various forms, although it needs substantially<br />

longer time compared with that needed for polishing a single crystal diamond. Moreover, the NPD was<br />

found to maintain its hardness at temperatures substantially higher than single crystal diamond.<br />

Applications of NPD to high-pressure generat ion have been made by using multianvil apparatus<br />

combined with in situ X-ray observations. We used a pair of NPD rods as the third-stage anvils for the 6-<br />

8-2 compression system, originally devised by Endo et al. (1985), and found that the pressures as high<br />

as ~90 GPa were produced at room temperature, which were maintained at temperatures up to<br />

~1200K. It is suggested that NPD can also be used for further higher pressure generation and other<br />

mineral physics studies using various high pressure apparatus, such as laser heated diamond anvil cell,<br />

Drickamer anvil apparatus, etc.<br />

Keywords: diamond, high pressure, multianvil

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