Multiwalled carbon nanotubes grown in hydrogen atmosphere: An x-ray diffraction study

X-ray diffraction study of multiwalled carbon nanotube (MWNT) grown by arc discharge in hydrogen atmosphere is presented. It is found that the thermal-expansion coefficient along the radial direction of MWNT is widely distributed in a range from 1.6 x 10-5 K-1 to 2.6 x 10-5 K-1, indicating the existence of both of Russian doll MWNT and highly defective MWNT. Russian doll MWNT is suggested to have the outer diameter less than ∼100 Aa. Thicker MWNT's are typically highly defective, and may have the jelly roll (scroll) or defective polygonal structure consisting of flat graphite domains