In situ high-energy synchrotron radiation study of boehmite formation, growth, and phase transformation to alumina in sub- and supercritical water.

Journal Article · Thu Jan 01 00:00:00 EST 2009 · Chem. Eur. J.

DOI:https://doi.org/10.1002/chem.200901269· OSTI ID:982348

Lock, N; Bremholm, M; Christensen, M; Almer, J D; Chen, Y -S; Iverson, B B

Boehmite (AlOOH) nanoparticles have been synthesized in subcritical (300 bar, 350 C) and supercritical (300 bar, 400 C) water. The formation and growth of AlOOH nanoparticles were studied in situ by small- and wide-angle X-ray scattering (SAXS and WAXS) using 80 keV synchrotron radiation. The SAXS/WAXS data were measured simultaneously with a time resolution greater than 10 s and revealed the initial nucleation of amorphous particles takes place within 10 s with subsequent crystallization after 30 s. No diffraction signals were observed from Al(OH){sub 3} within the time resolution of the experiment, which shows that the dehydration step of the reaction is fast and the hydrolysis step rate-determining. The sizes of the crystalline particles were determined as a function of time. The overall size evolution patterns are similar in sub- and supercritical water, but the growth is faster and the final particle size larger under supercritical conditions. After approximately 5 min, the rate of particle growth decreases in both sub- and supercritical water. Heating of the boehmite nanoparticle suspension allowed an in situ X-ray investigation of the phase transformation of boehmite to aluminium oxide. Under the wet conditions used in this work, the transition starts at 530 C and gives a two-phase product of hydrated and non-hydrated aluminium oxide.

• Research Organization: Argonne National Lab. (ANL), Argonne, IL (United States)
• Sponsoring Organization: USDOE Office of Science (SC); Danscatt; Danish Strategic Research Council
• DOE Contract Number: DE-AC02-06CH11357
• OSTI ID: 982348
• Report Number(s): ANL/XSD/JA-67082; TRN: US201013%%1021
• Journal Information: Chem. Eur. J., Vol. 15, Issue 2009
• Country of Publication: United States
• Language: ENGLISH

Related Subjects

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEAR CHEMISTRY
ALUMINIUM OXIDES
CRYSTALLIZATION
DEHYDRATION
DIFFRACTION
EVOLUTION
FUNCTIONS
GROWTH
HEATING
HYDROLYSIS
NUCLEATION
PARTICLE SIZE
PARTICLES
PHASE TRANSFORMATIONS
SCATTERING
SIGNALS
SIZE
SUSPENSIONS
SYNCHROTRON RADIATION
TIME RESOLUTION
WATER