Synthesis and characterization of Al2O3 hollow spheres

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سنتز و شناسایی صفات کره های توخالی آلومینیوم اکسید

Abstract
This paper presents a novel technique to create Al2O3 hollow spherical nanoparticles. It used Al(OH)3 which was synthesized with Al2(SO4)3
and NaOH, and the C-Al(OH)3 core-shell nanoparticle as intermediate phases. The Al2O3 hollow spheres were achieved by the calcination of the
carbon cores and the dehydration of Al(OH)3. The chemical composition, morphology, size and superficial crystal structure of the nanoparticles
were characterized with TEM, XRD, TGA, FTIR and BET. The result shows that the average diameter of the C-Al(OH)3 core-shell nanoparticles
is about 25 nm, the thickness of the Al2O3 shell is about 5 nm and the surface area is 215.2 m2/g. The procedure for the formation of Al2O3 hollow
nanoparticles is discussed in details

۱. Introduction
In recently years, hollow nanoparticles are attracting more
and more interests due to their importance in various fields of
science and technology, such as biological labels, optical
resonances, catalysis, magnetics, ceramics, and pigments. By
building up shells on the suitable medium, the core-shell
nanoparticles can be generated to meet some special requirements.
Furthermore, an important extension of core-shell
particles is the subsequent removal of the core by dissolution,
decomposition and other method to produce hollow shells [1].
Variousmethods of producing core-shell nanoparticles have been
reported in the literatures, such as electroless plating, precipitation,
sonochemical deposition, reverse micelles, sol–gel, and layer-bylayer
technique. Generally, these methods can be divided into four
categories: surface reaction, surface precipitation, precipitation
hetero-coagulation and the layer-by-layer technique [1–۳].
Al2O3 was one of the materials studied very early for its
potential application as a radiation dose-meter owing to its
superior thermal and chemical stability and low effective atomic
number [4–۶]. Since then, a great deal of efforts has been
directed towards the improvement of its sensitivity [7–۹]. In this
paper, the core-shell C-Al(OH)3 nanoparticles were produced by
using sol–gel preparation of Al(OH)3 on the surface of carbon
cores. Subsequently, the Al2O3 shells were created by the
removal of the carbon cores and the decomposition of Al(OH)3.
The obtained Al2O3 was 20 wt.% of the carbon black, the
detailed structures of the hollow Al2O3 shell nanoparticles were
investigated [10,11].
۲. Experimental
۲.۱. Details of sample preparation procedure
Both NaOH and Al2(SO4)3·۱۸H2O were of analytical purity
and were purchased from Tianjin chemical Factory(china).
Carbon black was taken from Beijing university of chemical
technology, Ethanol absolute was of chemical purity and was
purchased from Tianjin Alcohol Factory(china). Distilled water
was used in all the experiments. The detailed experimental
procedure is as follows: The carbon black was treated by being
heated up to 300 °C for 5 h, this because burning the water can
took hydrophilic point on the surface of carbon black, in order
to enhance the hydrophilicity of carbon black. The mixture of
۲.۰۰۰ g the treated carbon black particles and 150 mL distilled
water was sonicated for 1 h to get stable emulsion. 0.940 g
NaOH and 2.600 g Al2(SO4)3·۱۸H2O were dissolved in 100 ml
distilled water respectively to acquire NaOH and Al2(SO4)3

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