Ceramic microtubes self-formed at room temperature that exhibit a large bending stress

We have investigated the aluminum nitride microtubes made of aluminum nitri de thin film. Aluminum nitride thin film deposited on aluminum foil forms m icrotubes of itself at room temperature when the aluminum foil is dissolved in hydrochloric acid solution. The aluminum nitride microtubes exhibit a l arge bending stress of 1100 +/- 94 megapascals. The bending stress is more than three times larger than the bending strength of aluminum nitride bulk. The diameter of the microtubes is proportional to the film thickness. The bending stress is independent of the film thickness and is fixed. (C) 2000 American Institute of Physics. [S0021-8979(00)01720-5].