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Preparation Of Nano Paa Template And Ferroelectric Pzt Nanotubes

Posted on:2013-02-13Degree:MasterType:Thesis
Country:ChinaCandidate:Q M YeFull Text:PDF
GTID:2211330371459650Subject:Materials science
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Porous anodic alumina (PAA) films have been widely used as templates to fabricate nanostructures in various materials. However, ferroelectric nanostructures fabricated by PAA template still face many challenges. Based on the preparation study of nano-PAA template, lead zirconate titanate (PZT) nanotubes were synthesized in this work using a PAA template-directed method that integrates a sol-gel process with a spin-coating technique.At first, PAA films were fabricated by a two-step mild anodization (MA) under constant voltage in sulfuric, oxalic and phosphoric acid aqueous solutions and the influences of electrolyte species on the morphology of the PAA were studied. The results show that highly ordered nanopore arrangements in PAA can be achievable with this two-step anodization procedure, especially in sulfuric and phosphoric acid aqueous solutions. Their interpore distances are about 55nm, 110nm and 440nm for sulfuric acid, oxalic acid and phosphoric acid, respectively.Subsequently, several methods for detaching the PAA film obtained in oxalic acid solutions under MA from A1 substrate were developed by applying an improved chemical etching method and five different reversed-bias detaching approaches. The influences of these stripping approaches on the morphology of PAA and stripping efficiency were studied. The results show that the chemical etching method is particularly suitable for stripping of the PAA films formed by aluminum anodization on single side. Polyvinyl alcohol can be used as a water-soluble protective film, which is more environmental friendly as compared to the conventional polymer. As for the PAA film obtained by aluminum anodization on double side, it can be detached from the A1 substrate successfully by the five different reversed-bias detaching approaches. Among them, the stripping time is the shortest for the approach where the original electrolyte was replaced with phosphoric acid solution while reversing the polarity of the cell voltage.To suppress electrical breakdown effects in the course of conventional high-field anodization of aluminum, a new approach was developed to fabricate well-ordered PAA films by a single-step high-field anodization process at higher temperature in concentrated acid electrolyte. This paper reports on the detailed investigations of the high-field anodization behavior of aluminum in concentrated oxalic acid solutions. The influences of anodizing parameters such as the electrolyte concentration, bath temperature, current density on the morphology of PAA templates and electrical breakdown behaviors were discussed. The results confirm that stable high-field anodization can be realized without the occurrence of unfavorable breakdown and well-ordered PAA films can be available by increasing oxalic acid concentration and temperature. The interpore distance is proportional to the final voltage with a proportionality constant~2.0nm·V-1. In addition, the well-ordered PAA film can be fast obtained without assisting complex pretreatment processes and even without stirring of the electrolyte. Unlike conventional high-field anodization, a powerful cooling system is not required in this approach. Moreover, this approach is also valid for sulfuric acid electrolyte. But it is not appropriate for phosphoric acid electrolyte owing to its highly corrosive attack on the oxide film.Finally, PZT nanotubes were synthesized using a sol-gel method together with spin-coating technique in through-hole PAA templates. The effect of the PZT sol concentration was studied. Analysis results show that these nanotubes are composed of tetragonal perovskite nanocrystallites and appear to have high toughness. When the sol concentration is in the range of 0.1M to 0.4M, PZT nanotubes can be achieved utilizing nanochannel PAA templates. And the nanocrystallite size increases as the sol concentration rises.
Keywords/Search Tags:PAA template, mild anodization, high-filed anodization, concentrated acidic electrolyte, electrical breakdown, stripping, sol-gel, PZT nanotube
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