Open AccessOne‐step synthesis of flower‐like η‐Al 2 O 3 via supercritical hydrothermal method
Author(s) -
Jalouli Behrouz,
Abbasi Aref,
Musavi Khoei Seyed Mohammad
Publication year - 2020
Publication title -
micro and nano letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.25
H-Index - 31
ISSN - 1750-0443
DOI - 10.1049/mnl.2020.0244
Subject(s) - supercritical fluid , ostwald ripening , hydrothermal circulation , scanning electron microscope , calcination , hydrothermal synthesis , chemical engineering , materials science , desorption , phase (matter) , morphology (biology) , molten salt , nanostructure , adsorption , nanotechnology , chemistry , organic chemistry , metallurgy , catalysis , composite material , biology , engineering , genetics
In this Letter, flower‐like η‐Al 2 O 3 nanostructure was synthesised via hydrothermal method without any surfactant or further calcination. A molten salt bath rose the reactor temperature as much as 500°C to achieve the supercritical condition. Such a high temperature caused a rapid one‐step synthesis in two minutes. Al(NO 3 ) 3 and NaOH were the only precursors. Synthesised powders were investigated by X‐ray powder diffraction and scanning electron microscope, and the specific surface area was also determined by N 2 adsorption–desorption analysis. Increasing reaction time >2 min caused undesired Ostwald ripening. So instead of giving more time, a small amount of NaOH was added to form the η‐Al 2 O 3 phase. Moreover, the morphology of η‐Al 2 O 3 changed to flower‐like by increasing the density of the supercritical fluid. Finally, the probable mechanism of flower‐like morphology formation was proposed in two steps.