HR: 0800h
AN: MR31A-0148    [Abstracts]
TI: Micro-texture and Structure of High-pressure Quenched Graphite and Related Carbon Materials
AU: * Ohfuji, H
EM: ohfuji@sci.ehime-u.ac.jp
AF: Geodynamics Research Center, Ehime University, 2-5 Bunkyo-cho, Matsuyama, 790- 8577, Japan
AU: Aibara, K
EM: aibara-k@mserv.sci.ehime-u.ac.jp
AF: Geodynamics Research Center, Ehime University, 2-5 Bunkyo-cho, Matsuyama, 790- 8577, Japan
AU: Sumiya, H
EM: sumiya@sei.co.jp
AF: Electronics & Materials Lab, Sumitomo Electr. Industr., 1-1-1 Konyokita, Itami, Osaka, 664- 0016, Japan
AU: Irifune, T
EM: irifune@dpc.ehime-u.ac.jp
AF: Geodynamics Research Center, Ehime University, 2-5 Bunkyo-cho, Matsuyama, 790- 8577, Japan
AB: There have been extensive studies in room-temperature compression of graphite and related carbon materials such as nanotubes and fullerene. Some reports claimed that the transformation of carbon hybridized state from sp² to sp³ takes place under high pressure at room temperature, and the hardness of the quench products may be comparable to that of cubic diamond. Here, we investigated the micro-texture and structure involved in such high-pressure quenched carbon materials using high-resolution electron microscopy. High- pressure experiments were conducted on a variety of carbon materials including graphite (synthetic, highly- oriented sheet), single/multi-walled carbon nanotubes, amorphous carbons in a diamond anvil cell (DAC, with 250 μm culet non-beveled anvils) at room temperature. Pelletized sample was loaded into a 70 μm hall, drilled in a preindented Re gasket, without a pressure medium. The sample was compressed up to 70 ~ 90 GPa at room temperature, kept at the highest pressure at least overnight, and then decompressed. The pressure dependence of graphite E_2g( G) Raman band at ~1580cm^-1 was measured on compression and decompression. A_1g( D) band, so called defect band at ~1350 cm^-1, was also collected for the recovered products. The quenched materials were examined by high-resolution (HR) field emission (FE-) SEM and (HR)TEM. A focused ion beam (FIB) was employed to fabricate thin cross-sections of the samples. The most notable change in texture upon compression was observed in multi-walled carbon nanotube (MWNT); the elongated tubes were fragmented into short rods (ca. 100 - 300 nm in length and 80 - 100 nm in width, almost two times wider than that of the original MWNT). TEM observations showed that the short rod- shaped particles consist of piles of graphene shells (stacked walls of MWNT, characterized by (002) lattice fringes) which were significantly bent and fragmented. Some of those rod-shaped particles showed lattice fringes with an interlayer spacing of ca. 2 Å at the core regions, which may be derived from a high-pressure phase of carbon. More detailed textural observations and structural analysis based on electron diffraction are works in progress.
DE: 3900 MINERAL PHYSICS
DE: 3924 High-pressure behavior
DE: 5460 Physical properties of materials
SC: Mineral and Rock Physics [MR]
MN: 2007 Fall Meeting