O, Yong-Taeg Kim, Sang-Woo Shin, Dong-Chan 2024-01-20T23:35:34Z 2024-01-20T23:35:34Z 2021-08-31 2008-02-01 0927-7757 https://pubs.kist.re.kr/handle/201004/133747 An alpha-Al2O3 nanopowder was prepared via the thermal decomposition of ammonium aluminum carbonate hydroxide (AACH). The AACH precursor, which had an average crystallite size of 5-8 nm, was fabricated at a reaction temperature of 8 degrees C with the pH of the aqueous ammonium hydrogen carbonate (AHC) precursor solution set to 10, which afforded the highest [NH4+][AlO(OH)(n)(SO4)(-)(3-n/2)]][HCO2-] ionic concentration. The AACH precursor was transformed to NH4Al(SO4)(2), rhombohedral (Al-2(SO4)(3)), amorphous-, theta-, and alpha-Al2O3 according to the heat-treatment temperature. A time-temperature-transformation (TTT) diagram for thermal decomposition in air was determined. The critical particle size of theta-Al2O3 in the theta -> alpha a phase transformation was similar to 30 nm. Homogeneous, spherical alpha-Al2O3 nanopowders with an average particle size of 70 nm were prepared by firing the precursor crystallites at 1150 degrees C for 3 h in air. (C) 2007 Elsevier B.V. All rights reserved. English ELSEVIER SCIENCE BV Fabrication and synthesis of alpha-alumina nanopowders by thermal decomposition of ammonium aluminum carbonate hydroxide (AACH) Article 10.1016/j.colsurfa.2007.04.123 1 COLLOIDS AND SURFACES A-PHYSICOCHEMICAL AND ENGINEERING ASPECTS, v.313, pp.415 - 418 COLLOIDS AND SURFACES A-PHYSICOCHEMICAL AND ENGINEERING ASPECTS 313 415 418 scie scopus 000252952400095 2-s2.0-37449025423 Chemistry, Physical Chemistry Article; Proceedings Paper ammonium aluminum carbonate hydroxide (AACH) pH alpha-Al2O3 nanopowders TTT diagram