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Sintering of Compacts from Nanocrystalline Diamonds Without Sintering Agent

  • A. Witek (a1), B. Palosz (a1), S. Stel'Makh (a1), S. Gierlotka (a1), R. Pielaszek (a1), E. Ekimov (a2), V. Filonenko (a2), A. Gavriliuk (a2) and V. Gryaznov (a2)...

Abstract

Compacts of polycrystalline diamond were made in toroid-type high-pressure camera under the pressure of 8 GPa using temperatures between 800 to 2150°C without the use of additive components. Nanocrystalline commercial DALAN, and microcrystalline ASM diamond powders were used. The compacts were characterized by helium pycnometry, Vickers hardness measurements, X-ray diffraction and SEM methods.

The starting and sintered nanocrystalline grain compacts were found to have strongly one-dimensionally disordered cubic modification. The nanocrystalline powder had a bimodal grain size distribution function as determined from X-ray diffraction data and ab initio intensity calculations performed with the use of Debye functions. It was found that neither the grain size nor one-dimensional disordering change under high-pressure high-temperature conditions. There is a general tendency in a decrease of density of compacts with increase in the sintering temperature what resulting partly from graphitization above 1000–1200°C. The main factor which determines the density of the diamond compacts is closed porosity. Typically, the nanocrystalline diamond compacts sintered from 30 sec. to 6 min. have densities around 90% of the theoretical value. Their Vickers microhardness is 24 GPa and less.

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Sintering of Compacts from Nanocrystalline Diamonds Without Sintering Agent

  • A. Witek (a1), B. Palosz (a1), S. Stel'Makh (a1), S. Gierlotka (a1), R. Pielaszek (a1), E. Ekimov (a2), V. Filonenko (a2), A. Gavriliuk (a2) and V. Gryaznov (a2)...

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