Synthesis and formation of alumina whiskers from hydrothermal solution

摘要

Al₂O₃ whiskers with an average length of 5 μm have been synthesized from hydrothermal solution. Al(NO₃)₃ and urea were mixed and put into a Teflon-lined stainless steel autoclave and then treated at 120 °C to fabricate precursor whiskers NH₄Al(OH)₂CO₃ (AACH). AACH whiskers were heated at 1200 °C in a furnace to obtain Al₂O₃ whiskers. The time-dependent examinations revealed that the formation process of AACH whiskers involves two sequential processes: a short liquid–solid deposition process in the initial stage and a long Ostwald ripening process. During calcinations, AACH transforms to amorphism then to α-Al₂O₃. The escape of NH₃ and CO₂ induced the distortion and toothlike morphology on the surface of the Al₂O₃ whiskers.