高压下碳纳米管的X射线衍射研究

CARBON NANOTUBE PROPERTIES UNDER HIGH PRESSURE

用同步辐射原位高压能散X射线衍射技术 ,对碳纳米管进行了结构和物性的研究 ,压力达 50 7GPa。在室温常压下 ,碳纳米管的结构和石墨的hcp结构相似 ,其 (0 0 2 )衍射线的面间距为d0 0 2 =0 34 0 4nm ,(10 0 )衍射线的面间距为d10 0 =0 2 116nm。从高压X射线衍射实验看到 ,当压力升到 8GPa以上时 ,(0 0 2 )线变宽变弱 ,碳纳米管部分非晶化。而当压力从 10GPa或 2 0GPa卸压至零时 ,(0 0 2 )线部分恢复。但当压力升高至最高压力 50 7GPa时 ,碳纳米管完全非晶化 ,而且这个非晶化相变是不可逆的。用Birch Murnaghan方程拟合实验数据 ,得到体弹模量为K0 =(54 3± 3 2 )GPa(当K′0 =4 .0时 )。

The structure and physical properties of carbon nanotubes under high pressure up to 50.7 GPa were investigated using in situ high pressure energy dispersive X-ray diffraction with synchrotron radiation. At atmospheric pressure, the structure of carbon nanotubes is similar to the hexagonal close-packed lattice of graphite with the interplanar spacing of diffraction line (002) d002=0.3404 nm and that of line (100)d100=0.2116 nm. According to the high pressure X-ray diffraction results, diffraction line (002) is broadened and weakened above 8 GPa, and carbon nanotubes became partly amorphous. When pressure of 10 GPa and 20 GPa was down to zero, the diffraction line (002) was partly recovered. But at the maximum pressure of 50.7 GPa, they entirely became amorphous and this amorphous transition is irreversible. The equation of state of Birch-Murnaghan was used to obtain the bulk modulus K0=(54.3±3.2) GPa (at K'0=4.0).