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Preparation And Characterizations Of α-Al2O3 Nanoparticles

Posted on:2012-10-06Degree:MasterType:Thesis
Country:ChinaCandidate:J W LiFull Text:PDF
GTID:2181330335973058Subject:Materials Physics and Chemistry
Abstract/Summary:PDF Full Text Request
Alumina is a very important ceramic material and widely applied in fields of ceramics, metallurgy, electron and catalysts, because of its high heat-resistance, high corrosion-resistance, good electrical insulation and catalytic abilities. In order to attain homogeneous microstructure and thus high mechanical properties,α-Al2O3 powders are acquired to have the characteristics of ultrafine particle sizes, no agglomeration, regular morphology and narrow particle size distribution. So it is of great signification to prepare nanosizedα-Al2O3 powders. Using the cheap aluminum sulphate as raw materials, alumina precursors were prepared by chemical precipitation method. The formation mechanism of ultrafine precursor in the homogeneous precipitation and the inhomogeneous precipitation was discussed. The influence of preparation conditions on the morphology of alumina precursors, particle size and agglomeration degree was studied. The phase transformation and morphology change of alumina precursors during the calcination were investigated.It is found that the Al2O3 nanoparticles with ultrafine particle sizes, weak agglomeration, regular morphology and narrow particle size distribution can be prepared by adjusting the aluminum ion concentration. As the concentration of Al3+ reduces from 0.5 mmol/L to 0.25 mmol/L, the average particle size reduces from 80 nm to 20 nm. The particle size distribution and the morphology can be controlled by adjusting the reaction time. As the molar ratio of DMAB and Al3+ is 40:1 and the reaction time extends from 0.5 h to 1 h, the morphology of the particle is spherical and the corresponding size distribution changes from wide to uniform; when the reaction time extended to 2 h, the morphology of the particles is still spherical, but the platelets were found in part. And the precursors transformed from amorphous to boehmite. The IR curve and TG-DTA curve show that the precursor contains a certain amount of sulfuric acid root, and these can be completely removed around 1150℃. The SO2 or SO3 that released from sulfuric acid root decomposition as the isolation of gas phase, does not make the precursor sintering seriously.Using the aluminum sulfate as aluminum salt and ammonia as precipitator, theα-Al2O3 nanoparticles with spherical as well as ultrafine particle size can be prepared by the inhomogeneous precipitation method. The sulphuric acid can be controlled by adjusting the solution pH. The well dispersed particle is obtained when the pH=5.5.As the concentration of Al3+ reduces from 0.1 mol/L to 0.05 mol/L, the particle size does not change obviously. When the concentration of Al3+ increases to 0.2 mol/L, the size increased obviously.
Keywords/Search Tags:Nanoparticle, Homogenious precipitation method, Inhomogeneous precipitation method, α-Al2O3, Isolating phase
PDF Full Text Request
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