Novel polycrystalline BN ribbons (BNRs) with an average width of about 300 nm and a thickness of about 200 nm have been synthesized using Sialon ribbons and ammonia borane as starting materials. We find out that single-crystalline Sialon ribbons can be converted to polycrystalline BNRs upon reacting with the vapors decomposed from ammonia borane at 1450 degrees C. A template self-sacrificing mechanism has been proposed to account for the growth of BNRs. Our approach can be extended to fabricate other BN nanostructures. (C) 2011 Elsevier Ltd. All rights reserved.