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In Vestigations On Porous Anodic Aluminum Oxide Films Fabricated By Using Unsteady-state Anodization Processes

Posted on:2018-10-24Degree:MasterType:Thesis
Country:ChinaCandidate:S Y JinFull Text:PDF
GTID:2321330533466931Subject:Microelectronics and Solid State Electronics
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Low-dimension nanomaterials,such as nanodot and nanowires,were widely applied in nano-devices because of their unique physical and chemical properties.With the development of nanotechnology,nanomaterials with complex structures are directly applied in devices used in sensors and solar cells,which will demonstrate largely enhanced properties,compared with conventional devices.Therefore,controllable synthesis of nanomaterials with complex structures has become a hot research topic.Porous anodic aluminum oxide(AAO)has been commonly used as template materials for the fabrication of various functional materials due to simple fabricating process,low cost and good reproducibility.In addition,porous AAO is also used as filter membranes which needs good chemical and mechanical properties.In this paper,porous AAO films with complex microstructure and polycrystalline alumina structure were fabricated by using unsteady-state anodization process.1.The morphology of barrier layer of porous AAO was adjusted by varying the andization voltage(300~600V).The effects of Ua(300~600V),anodization current density(Ja,100~200A/m2),and the proportion of ethanol adding(0.3M oxalic acid : ethanol = 1 : 1,3 :2,V/V)on the submicron/micron structures of porous AAO templates have been investigated in detail.2.Firstly,porous AAO films of AAO-Al sheets were fabricated in ethanol-oxalic acid electrolyte at 600 V through the first anodization process.Then aluminum sheets with submicron/micro pits were obtained by removing the porous AAO films in a mixture solution of CrO3 and H3PO4.Finally,porous AAO templates with diverse nano/submicron/micron multiple-scale structures were fabricated in the 0.3M oxalic acid solution under lower voltage based on aluminum sheet with submicron/micro pits through the second anodization process.The effects of Ua(30~40V),etching process,and anodization time(15~30min)on the nanostructures of as-fabricated porous AAO films have been studied carefully.3.Patterned aluminum surface with different cell sizes(640~900nm)was obtained by using large voltage anodization processes(400~600V)in ethanol-oxalic acid electrolyte and a following AAO removing method.Porous AAO films was fabricated in 0.3M oxalic acid solution under periodic voltage based on the patterned aluminum surface(the first anodization voltage is 600V)and the smooth aluminum surface,respectively.The voltage/current-time curves during anodization were analyzed in detail.Moreover,the AAO microstructure,film thickness and film growth rate have been comparatively studied based on smooth aluminum surface and patterned aluminum surface,respectively.4.Three types of unique AAO structure can be fabricated by using constant voltage or periodic voltage in 0.3M oxalic acid solution based on patterned aluminum surface by varying the anodization voltage and etching time:(1)AAO with three-dimensional(3D)interconnected pores;(2)controllable self-assembled AAO nanowires;(3)supporting AAO skeleton structures.5.The porous AAO film containing nanocrystalline alumina was fabricated by anodization process in the mixture solution of oxalic acid and ethanol(0.3M oxalic acid : ethanol = 1 : 2,V/V)at 900 V.Both the intrinsic formation mechanisms of porous AAO films with nano-polycrystalline alumina structure,and the mechanisms of anodization process under ultrahigh voltage(700~1000V)without the breakdown and burning phenomena,have been studied.
Keywords/Search Tags:porous, anodic aluminum oxide, multi-scale structure, high voltage, nano-polycrystalline
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