Boron nitride (BN) nanotubes were synthesized by heating a mixture of boron and alumina-supported nickel boride catalyst at the temperatures from 1100 to 1300 degreesC under nitrogen or ammonia atmosphere. The BN Nanotubes exhibit a well-crystallized tube structure with 5-40 nm in diameter and several microns in length. Their tip morphology and chirality depend on the diameter of BN nanotubes. Bamboo- and polar-like BN could be obtained when the synthesized temperature increases to 1400 and 1500 degreesC, respectively. The catalytic growth. mechanism was also proposed to explain the growth of BN nanotubes. (C) 2002 Elsevier Science B.V. All rights reserved.