This paper is trying to explore the effect of stirring time on the synthesis of nano-
Alumina is one of the most widely used ceramic materials as catalysts, catalyst supports and absorbents, and also wear resistant coating [
This study tends to synthesize nanosized
Aluminum isopropoxide Al (OC3H7)3 (Merck, German), aluminum nitrate nonahydrate Al (NO3)3·9H2O (Merck, German), and Sodium dodecylbenzen sulfonate (SDBS) (Merck, German) were used as raw materials to prepare nano-
The molar ratio of alumina sol (ALP/ALN) was 3 so that the raw materials can be completely dissolved and provide clear solutions. The solutions were continuously stirred for 24, 36, 48, and 60 hours. Later, Sodium dodecylbenzen sulfonate (SDBS) was added by adjusting the molar ratio between alkoxide and surfactants to 0.1 and stirred for one hour. It is expected that the optimal time for the addition of surfactant is prior to the onset of the nucleation and growth step. The solutions were heated up to 60°C and stirred constantly for evaporation process. Viscosity and color changed as the sol turned into a transparent stick gel. The gels were, then, heat-treated at 90°C for 8 hours. Dried gels were calcined at temperature between 1000 and 1200°C. Finally, the calcined powders crushed by using mortar and pestle.
Phase identifications were performed by X-ray Diffraction (XRD) using nickel-filtered Cu K
Nano-
The synthesis of nano-
XRD spectra of Al2O3 at 1200°C.
The observation reported by Hyuk-Joon et al. [
Figure
TGA curve of the as-synthesized precursor.
From 400–750°, weight loss of the mat is less than 1%, and also there is less decrease in temperature. So, the volatilization does not happen obviously [
The DSC curve of the precursor is illustrated in Figure
DSC curve of the as-synthesized precursor.
Three small exothermal peaks at 420, 456, and 479°C are attributed to the pseudomophic phase transformation of bohemite to
Figure
SEM micrographs of
24 hr
36 hr
48 hr
60 hr
Novakovic and Korthaus [
The TEM micrographs Figures (
TEM micrographs of
24 hr
36 hr
48 hr
60 hr
Takhashi et al. [
At low supersaturation, there are usually negligible effects of agglomeration, and the crystals’ size distribution is mainly affected by the competition between the nucleation and the growth of the crystal. However, at high supersaturation, the process is dominated by agglomeration.
As it proceeds, more water evaporates from sol, the supersaturated solution, thus, supplies the material necessary to bond colliding particles and form the agglomerates. Local concentrations, also, determine the electrical interaction between the small colloidal particles because most particles in aqueous media are charged and the resulting repulsion force depends on the solution composition.
Hence, due to these reasons, the agglomeration process enhances after 60 hours of stirring time, and there was strong agglomeration observed in the samples. This is in agreement with the observation of this study as shown in Figure
Consequently, despite the high temperature (1200°C), the obtained particle size ranged between 20 and 30 nm after 48 hours of stirring time. Furthermore, Wright and Sommerdijk [
Therefore, the repulsions dominate the vanderwaals attractions, and the particles are stable in opposition to the aggregation unless the thickness of the diffuse layer can be significantly decreased.
The main way in which the diffuse layer thickness can be decreased is raising the ionic strength of the solution, and in particular, increasing the charge on the counterion. Hence, the stirring time was effective in controlling the size of the particles and their degree of aggregation.
In this research, the sol-gel method for the synthesis of aluminum oxide from aluminum alkoxide complexes was explained. However, selecting and controlling the exact stirring time for controlling the size of particles and the degree of aggregation are important. The evolution in the alumina precursor involved the decomposition which was followed by amorphous-to-
The authors would like to thank the Ministry of Science, Technology, and Innovation, Malaysia, University Putra Malaysia, and University Sains Malaysia in providing fund and support for this work.