Development of anodised aluminium oxide nanostructure from Al-Mn alloy
This study was divided into two parts. The first part of the study was focused on the synthesis of well ordered porous AAO by using oxide dissolution treatment. The porous AAO was formed by anodising of 99.99 % aluminium in 0.3 M oxalic acid at 15 oC for 15 minutes. Anodised substrates were subje...
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| Format: | Thesis |
| Language: | English |
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| Online Access: | http://dspace.unimap.edu.my:80/xmlui/bitstream/123456789/59424/1/Page%201-24.pdf http://dspace.unimap.edu.my:80/xmlui/bitstream/123456789/59424/2/Full%20text.pdf |
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| Summary: | This study was divided into two parts. The first part of the study was focused on
the synthesis of well ordered porous AAO by using oxide dissolution treatment. The
porous AAO was formed by anodising of 99.99 % aluminium in 0.3 M oxalic acid at 15
oC for 15 minutes. Anodised substrates were subjected to oxide dissolution treatment by
immersing in stirred mixture of chromic acid and phosphoric acid. The effect of oxide
dissolution treatment on the morphology and regularity of porous AAO was studied by
using scanning electron microscope. The results showed that exposure of porous AAO
to oxide dissolution treatment up to three minutes revealed the well ordered pores
arrangement that formed during the steady state growth stage. Regularity of the porous
AAO was improved. In the second part of the study, porous AAO was formed from
aluminium manganese (Al-Mn) alloy substrates and the effect of manganese content,
anodising voltage, concentration of oxalic acid, and temperature of oxalic acid on the
anodising behaviour, morphology, dimensional properties and growth kinetics were
studied. Results showed that the addition of Mn from 0.5 wt % to 2.0 wt % into Al
substrates reduced the current density, regularity and growth kinetics of porous AAO.
The pore size and interpore distance were also found to decrease with the addition of
Mn. Anodising efficiency of anodising process decreased as the Mn content increased
up to 1.0 wt %, but increased when the Mn content was further increased to 2.0 wt %.
Analysis of XRD patterns showed that amorphous alumina was formed in substrates of
all compositions and MnO2 was found to present in Al-1.5 wt % Mn and Al -2.0 wt %
Mn substrates. For the study of effect of anodising voltage, anodising of Al-0.5 wt %
Mn under the influence of increasing anodising voltage of 30-70V has led to higher
current density, larger pore size and interpore distance and higher growth rates. The
regularity of pore arrangement of porous AAO was improved when the anodising
voltage was increased from 30 V to 50V, but deteriorated when further increased to 70V.
Dielectric breakdown occurred when anodising was conducted at 70V. Amount of
amorphous alumina was found to increase when the anodising voltage was increased
from 30 V to 70 V. Anodising of Al-0.5 wt % Mn at 50 V in oxalic acid of increasing
concentration from 0.1 M to 0.7 M increased the current density and growth kinetics.
Well ordered porous AAOs were obtained when oxalic acid of all concentration was
used, except 0.1 M. Increase of concentration of oxalic acid decreased the pore size
while no significant difference in interpore distance was observed. Anodising efficiency
decreased as a function of concentration of oxalic acid. The relative intensity of broad
peaks in XRD patterns showed that amount of amorphous alumina increased as a
function of concentration of oxalic acid. For the study of effect of temperature of oxalic
acid, anodising of Al-0.5 wt % Mn was conducted at 50V in 0.5 M oxalic acid of
temperature ranging from 5oC to 25oC. Current density and oxide thickness increased
while regularity of pores arrangement and anodising efficiency decreased with the
increasing temperature of oxalic acid. Temperature of oxalic acid did not have obvious
effect on both pore size and interpore distance. Relative intensities of broad peaks
increased indicating the amount of amorphous alumina increased with the increasing
temperature of oxalic acid. |
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