X-Ray Diffraction Study of Carbon Nanotubes Under High Pressure

Abstract

The structure and physical properties ofcarbon nanotubes have been investigated by using in situ highpressure energy dispersive x-ray diffraction with synchrotron radiation atpressures up to 50.7 GPa. At atmospheric pressure, the structure ofcarbon nanotubes is similar to the hexagonal close-packed lattice ofgraphite with the interplanar spacing of the diffraction line (002)d002 = 0.3404 nm and that of the line (100) d100 = 0.2116 nm.According to the high pressure x-ray diffraction results, the diffractionline (002) is broadened and weakened above 8 GPa, and carbon nanotubesbecome partly amorphous. When the pressures of 10 and 20 GPa aredecreased to zero, the diffraction line (002) is partly recovered.While at the maximum pressure of 50.7 GPa, they become entirely amorphousand this amorphous transition is irreversible. We used the equation ofstate of Birch-Murnaghan to fit the P-V data of carbon nanotubes andobtained the bulk modulus K0 = 54.3±3.2 GPa (at K'0 = 4.0).