Formation of zirconia sheets with nanotubular structure prepared by anodization of zirconium
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Date
2014-08-01
Authors
Suriyati Mohamed Ansari
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Abstract
In this work, anodic process was done to produce anodic layer of comprising of ZrO2 nanotubes. The anodic layer was then removed from the Zr foil to produce free standing ZrO2 nanotube sheets. Types of carbonates, different concentration of carbonates, anodization voltage and also anodization time were experimented aiming at forming ZNTs sheets. The presence of carbonates, K2CO3 and Na2CO3 as an additive plays an important role during the formation of the nanotube sheets. To compare, in EG added with 3 ml 1 M K2CO3 shows more nanotube sheets formation compared to EG with Na2CO3. In ZNTs formation, H+ is released in the nanotubes and when H+ reacts with CO32-, CO2 gas is released. The formation of CO2 gas effect the adhesion of ZrO2 film from the foil. Effect of different concentrations of K2CO3 added, the amount of nanotube sheets that formed was also increased. As for the effect of anodization voltage and time, it appears that at 40 V and 60 V, the amount of ZNTs were formed and at 60 V, the film was easier to be removed from Zr foil. As for the effect of anodization time, it seems that at longer time, more reaction between the CO32- and H+ occurs forming more CO2. The CO2 gas produced from the reaction of CO32- and H+ accumulated at the metal and oxide interface and makes the anodic oxide film to detach easily from Zr substrate without the need of pretreatment. The ZrO2 nanotube sheets were found to be amorphous, thus it were annealed at three different temperatures of 200 ⁰C, 400 ⁰C and 600 ⁰C. The phase formation and transformation at each temperature was observed with all tetragonal (T), cubic (C), and monoclinic (M) phase co-exist after annealing at 400 ⁰C and 600 ⁰C. The activity of the annealed ZrO2 nanotube sheets was study by degradation of MO. After 300 min, about 37 % of the MO was degraded by the annealedsample at 600 ⁰C, 35 % of MO degraded by sample annealed at 400 ⁰C and 22 % of MO degraded by sample annealed at 200 ⁰C. This indicates that crystallinity is important in photocatalysis