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Effect of Milling on the Formation of Nanocrystalline χ‐Al 2 O 3 from Gibbsite
Author(s) -
Chaitree Wasu,
Jiemsirilers Sirithan,
Mekasuwandumrong Okorn,
Praserthdam Piyasan,
Charinpanitkul Tawatchai,
Panpranot Joongjai
Publication year - 2010
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/j.1551-2916.2010.03849.x
Subject(s) - gibbsite , nanocrystalline material , calcination , materials science , boehmite , chemical engineering , thermogravimetric analysis , activation energy , phase (matter) , differential thermal analysis , isothermal process , particle size , ball mill , mineralogy , analytical chemistry (journal) , metallurgy , diffraction , chemistry , aluminium , nanotechnology , thermodynamics , catalysis , biochemistry , physics , organic chemistry , optics , engineering , chromatography
Gibbsite (FG) with mean particle diameter ( d 50 =13 μm) was milled in an attrition mill for 12 and 24 h using alumina balls as grinding media and calcined at different temperatures in the range of 350°–600°C. The properties of the alumina obtained were determined by X‐ray diffraction, N 2 physisorption, thermogravimetric/differential thermal analyses, and transmission electron microscopy. Without milling, the alumina obtained normally contained the mixed phases between γ‐ and χ‐phase alumina. On the other hand, high purity of nanocrystalline χ‐phase alumina (100 wt%) can be produced by calcination of the 24‐h milled FG at 600°C. The isothermal kinetics measurements revealed that the rate constant ( k ) for phase transformation increased as the particle size of gibbsite decreased and the calculated activation energy for transformation from FG to alumina decreased from 20.6 to 14.7 and 6.8 kJ/mol after milling for 12 and 24 h, respectively. The physical properties of nanocrystalline χ‐alumina obtained by the calcination of milled FG were comparable to those produced by the solvothermal method. The present results offer a simple way to prepare a large amount of pure χ‐phase alumina for particular industrial applications.