Superhard phase of single wall carbon nanotube:: comparison with fullerite C60 and diamond

A new superhard phase of single wall carbon nanotube (SP-SWNT) has been synthesized under non-hydrostatic compression at room temperature. The SP-SWNT was studied in comparison with diamond and ultrahard fullerite both in situ under pressure in a shear diamond anvil cell and after pressure release. After intermediate phase transitions single wall carbon nanotube (SWNT) transforms to SP-SWNT at pressure 24 GPa (hydrostatic component of a stress tensor). High mechanical properties of SP-SWNT, namely bulk modulus (465 GPa) exceeding diamond and hardness (62-150 GPa) belongs to the range between cubic BN and diamond, preservation of Raman bands of SWNT in SP-SWNT along with the bands broadening and absence of new bands (within the detection limit), are characteristic for the new phase. New procedure of pressure calibration using pressure-induced Raman shift of diamond anvil was elaborated especially for measurements of bulk modulus of superhard materials. Bulk module of ultrahard fullerite measured in situ in the diamond cell using the new procedure is 585 GPa. It appropriates to the literature data and verifies the new procedure. (C) 2002 Elsevier Science B.V. All rights reserved.