To see the other types of publications on this topic, follow the link: Porous anodic aluminium oxide.
Dissertations / Theses on the topic 'Porous anodic aluminium oxide'
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 50 dissertations / theses for your research on the topic 'Porous anodic aluminium oxide.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse dissertations / theses on a wide variety of disciplines and organise your bibliography correctly.
1
Oh, Jihun. "Porous anodic aluminum oxide scaffolds; formation mechanisms and applications." Thesis, Massachusetts Institute of Technology, 2010. http://hdl.handle.net/1721.1/59709.
Full textAbstract:
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2010.Cataloged from PDF version of thesis.
Includes bibliographical references.
Nanoporous anodic aluminium oxide (AAO) can be created with pores that self-assemble into ordered configurations. Nanostructured metal oxides have proven to be very useful as scaffolds for growth of nanowires and nanotubes with tunable diameters and with tight diameter distributions. For 50 years, field-assisted dissolution of the oxide has been cited as the mechanism that leads to pore formation in alumina, and by analogy, porous anodic TiO₂ and other functional metal oxides. We show that field-assisted dissolution models are consistent with the observed dependence of the Al₂O₃ dissolution rate on the electric field, as well as the existence of a critical field for pore initiation. However, we further show that the well-known ordered porous structure, which has a significantly different length scale, does not result from a field-induced instability, but is instead the result of a strain-induced instability with forced plastic deformation and flow of the oxide during further anodization. We demonstrate that these pore generation mechanisms can be controlled independently, even when they co-exist, by controlling the electric field across the oxide as well as the anodization conditions. We also show that mechanical confinement results in a dendritic pore structure. Through interpretation of these results we develop a generalized mechanism for ordered pore formation in AAO in analogy with cellular solidification. In addition, we report on abnormal behavior in anodic oxidation of Al in mechanically confined structures for formation of horizontal nanoporous anodic alumina oxide, H-AAO. Instead of smooth pore walls, periodic dendrite inner pore structures form, the growth rate is suppressed to 5 % of its value during bulk anodization under the same conditions, and a steady-state is never reached. These anomalies associated with formation of H-AAO originate from suppressed volume expansion and plastic flow of Al₂O₃ confined by the SiO₂ hard mask. By determining new anodization conditions leading to zero volume expansion, dendritic H-AAO can be avoided and kinetic retardation can be minimized. A new method for perforation of the AAO barrier layer has been developed, based on anodization of Al/W bilayer films on substrates. When Al/W bilayer films are anodized and pores approach the Al/W interface, tungsten oxide forms and penetrates the alumina barrier oxide, in part, due to enhanced plasticity of the alumina layer. By selectively etching the tungsten oxide, the barrier oxide can be removed and the base of the pores opened, without etching of the AAO. Finally, we further refined the selective barrier perforation process using the W interlayer to develop a methodology for fabrication of through-pore AAO scaffolds on any conducting substrate (AS) by anodizing an Al/W/AS tri-layer. Structural and kinetic study of the WO₃ extrusion revealed that the anodization of W consumes a fixed thickness of the W layer in acidic electrolytes under specific anodization conditions. Based on this study, the optimum thickness of the W interlayer in the Al/W/Au tri-layer was measured for various anodization conditions. Through-pore AAOs were fabricated on Au layers with exposure of the surface at the base of the pores, using the optimum W thickness without a violent O₂ evolution reaction and without changing the pore diameters. With scaffolds made using this methodology, vertically-aligned free-standing Au and Pt nanowires with diameters ranging from about 12 nm to about 120 nm were grown by electrodeposition on a gold substrate.
by Jihun Oh.
Ph.D.
2
He, Xueying. "Characterization of Porous Anodic Aluminum Oxide Film by Combined Scattering Techniques." University of Cincinnati / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1383645061.
Full text
3
Lim, Jin-Hee. "Synthesis and Characterization of Nanostructures in Porous Anodic Aluminum Oxide Templates." ScholarWorks@UNO, 2011. http://scholarworks.uno.edu/td/455.
Full textAbstract:
In this study, template-based methods are used for the fabrication of various nanostructures such as nandots, nanorods, nanowires, nanotubes, and core-shell structures. Porous alumina membranes were employed as templates and metal nanostructures were synthesized in the templates by electrodeposition. By using lithography techniques, controlled patterned nanostructures were also fabricated on alumina templates. The magnetic properties of the various metal nanostructures were investigated. The pore size, interpore distance, and pore geometry highly affect magnetic properties of nanostructures grown in the templates. Hexagonally ordered porous alumina templates can be fabricated by two-step anodization. The pore diameters and interpore distances were readily controlled by appropriately changing anodization conditions and pore widening time. Alumina templates with various pore geometries were also successfully synthesized by changing applied voltage, increasing and decreasing, during a third anodization step. To understand magnetic properties of nanostructures with different aspect rations in the form of nanodots, nanorods, or nanowires, Fe nanostructures were fabricated in the templates by controlling of electrodeposition times. The coercivity of nanostructures increased with increasing aspect ratio. The anisotropy of the arrays was governed by the shape anisotropy of the magnetic objects with different aspect ratios.
nanowires in mild-hard alumina and conventional alumina templates showed distinct differences in the squareness of hysteresis loops and coercivity both as a function of pore structure and magnetic component. Iron oxide nanotubes with a unique inner-surface were also fabricated by an electrodeposition method. β-FeOOH nanotubes were grown in alumina templates and transformed into hematite and magnetite structures during various heating processes. Hematite nanotubes are composed of small nanoparticles less than 20 nm diameters and the hysteresis loops and FC-ZFC curves show superparamagnetic properties without the Morin transition. In the case of magnetite nanotubes, which consist of slightly larger nanoparticles, hysteresis loops show ferromagnetism with weak coercivity at room temperature while FC-ZFC curves exhibit the Verwey transition at 125 K. For the patterning of nanowires, lithography techniques including nanosphere lithography and e-beam lithography were used. Nanosphere lithography used self-assembled PS spheres as a mask creates holes between spheres and the size of the holes is determined by the size and geometry of ordered PS spheres on the templates. This method can grow patterned nanowires arrays and also produce unique cup-shaped nanostructures with sizes ranging from micrometer down to several nanometers. E-beam lithography was also combined with template-based electrodeposition. Of these two lithographic methods, this one is the most powerful in the fabrication of patterned nanostructures with high aspect ratios. Various features and the sizes of patterned structures can be readily controlled. By the directing the pore diameters and interpore distances of the alumina template, the size and number of patterned nanowires are also adjustable.
4
Chennell, Philip. "Préparation et caractérisation de surfaces poreuses ordonnées en polymères en vue d'applications médicales." Thesis, Université Clermont Auvergne (2017-2020), 2018. http://www.theses.fr/2018CLFAS005/document.
Full textAbstract:
Les stents urétéraux et les sondes de néphrostomie sont constitués de silicone ou de polyuréthane thermoplastique (TPU). Afin de limiter les risques infectieux lors de leur implantation, une modification topographique par création de pores permettrait de limiter l’adhésion des bactéries et de former des réservoirs pour une libération in situ de substances antiinfectieuses. Ce travail vise à préparer des surfaces en polymère ayant un motif poreux tubulaire ordonné. Une réplication en deux temps à partir de surfaces ordonnées poreuses d’oxyde d’aluminium (PAAO) préparées par 2 méthodes (double anodisation douce et double anodisation dure/douce) a été mise en œuvre pour reproduire le motif initial sur des surfaces en silicone et TPU. Pour le moule intermédiaire trois matériaux ont été testés (acrylonitrile butadiène styrène, polystyrène et résine polyacrylate). Les surfaces ont toutes été caractérisées par des techniques microscopiques et spectroscopiques. Les surfaces en PAAO préparées par double anodisation douce possédaient des pores d’environ 50 nm de diamètre et 100 nm de profondeur, alors que celles obtenues après mise au point de la méthode dure/douce étaient de taille supérieure, d’environ 125 nm de diamètre et ayant des profondeurs de quelques centaines de nanomètres. La surface du moule intermédiaire est constituée de picots. Une adhésion latérale de ceux-ci a été observée pour certaines conditions. La meilleure réplication du motif a été obtenue pour le TPU. Les surfaces ainsi obtenues pourront être utilisées et optimisées lors de l'étude ultérieure de l'adhésion du biofilmUreteral stents and nephrostomy catheters are made of silicone or thermoplastic polyurethane (TPU). A topographical modification creating an ordered porous surface could limit the infectious risks during their implantation, by reducing bacterial adhesion and creating a loading platform from which anti-infectious compounds could be released.In this work, a two-steps replication method was used to create ordered porous polymer surfaces (silicone or TPU) using porous anodic aluminium oxide (PAAO) as master template. The PAAO surfaces were prepared by double mild or double hard/mild anodization. Three intermediate mould materials were tested (acrylonitrile butadiene styrene, polystyrene, polyacrylate resin). The polymer material (silicone or TPU) was then moulded onto the intermediate mould surfaces that possessed freestanding pillar arrays, to imprint pores. The obtained surfaces were characterized by microscopic and spectroscopic methods. The initial PAAO surfaces prepared by double mild anodization possessed pores of about 50 nm diameter and 100 nm depth, whereas those prepared after development of the double hard/mild anodization method were bigger, of about 125 nm diameter and several hundred nanometers deep. The intermediate mould structure possessed freestanding arrays, but instabilities (lateral adhesion) were noted for certain conditions. The best pattern replication was observed for TPU. In conclusion, these novel porous polymeric surfaces could be optimized and tested for an anti-biofilm effect
5
King, L. J. "Aligned nanorods of A1PO4-5 within the pores of anodic alumina : a thesis submitted to the Victoria University of Wellington in fulfilment of the requirements for the degree of Master of Science with Honours in Chemistry /." ResearchArchive@Victoria e-thesis, 2010. http://hdl.handle.net/10063/1289.
Full text
6
Chintakula, Goutam. "SCHOTTKY DIODES ON COPPER PHTHALOCYANINE NANOWIRE ARRAYS EMBEDDED IN POROUS ALUMINA TEMPLATES." UKnowledge, 2008. http://uknowledge.uky.edu/gradschool_theses/556.
Full textAbstract:
Vertically aligned nanowire arrays of copper phthalocyanine (CuPc) and CuPc-Al Schottky diodes, of controllable diameter and length were fabricated by cathodic electrodeposition of CuPc into anodized alumina (AAO) templates, followed by annealing at 300 ºC in Argon. AAO over Aluminum tape and that over ITO-glass were both used as starting templates for the device fabrication. Depending on the dimensions of the starting AAO template, diameters of CuPc nanowires ranged from 30 nm to 40 nm and the lengths ranged from 500 nm to 1 μm. The temperature dependence of the phase and the absorption spectrum of the nanowires are reported. The electrodeposited nanowires (as prepared) had the preferred crystallite orientation of the α-phase. ITO formed the ohmic contact and Schottky contacts were formed between CuPc and aluminum. Insertion of a thin layer of PEDOT:PSS between CuPc nanowires and the ITO electrode improved the contact and reduced the series resistance by an order of magnitude. Schottky diodes were characterized and analyzed at room temperature and at cryogenic temperatures.
7
Moturu, Sri Harsha. "SYNTHESIS AND CHARACTERIZATION OF P-TYPE COPPER INDIUM DISELENIDE (CIS) NANOWIRES EMBEDDED IN POROUS ALUMINA TEMPLATES." UKnowledge, 2011. http://uknowledge.uky.edu/gradschool_theses/91.
Full textAbstract:
This work focuses on a simple template assisted approach for fabricating I-III-VI semiconductor nanowire arrays. Vertically aligned nanowires of p-CIS of controllable diameter and thickness are electrodeposited, from an acidic electrolyte solution, inside porous aluminum templates using a three electrode set up with saturated calomel electrode as the reference. AAO template over ITO-glass was used as starting template for the device fabrication. The deposited CIS is annealed at different temperatures in a reducing environment (95% Ar+ 5% H2) for 30 minutes. X-ray diffraction of the nanowires showed nanocrystalline cubic phase structures with a strong orientation in the <112> direction. The effective bandgap of the deposited CIS nanowires determined using the Near Infrared (NIR) Spectrometer was found to be 1.07eV. The type of CIS electrodeposited inside the porous alumina template is determined to be p-type from the Schottky diode obtained with ITO-CIS-Au structure. Schottky diodes were characterized and analyzed at room temperature.
8
Yanamanagandla, Srikanth. "SYNTHESIS AND CHARACTERIZATION OF SCHOTTKY DIODES ON N-TYPE CdTe NANOWIRES EMBEDDED IN POROUS ALUMINA TEMPLATES." UKnowledge, 2008. http://uknowledge.uky.edu/gradschool_theses/573.
Full textAbstract:
This work focuses on the growth of vertically aligned CdTe nanowire arrays of controllable diameter and length using cathodic electro deposition in anodized alumina templates. This step was followed by annealing at 250° C in a reducing environment (95% Ar + 5% H2). AAO template over ITO-glass was used as starting template for the device fabrication. The deposited nanowires showed nanocrystalline cubic phase structures with a strong preference in [111] direction. First gold (Au) was deposited into AAO using cathodic electro deposition. This was followed by CdTe deposition into the pore. Gold was deposited first as it aids the growth of CdTe inside AAO and it makes Schottky contact with the deposited n type CdTe. CdTe was determined to be n-type from the fact that back to back diode was obtained with Au-CdTe-Au test structure. Aluminum (Al) was sputtered on the top to make the ohmic contact to the n type CdTe deposited in AAO. Analysis of Schottky diodes yielded a diode ideality factor of 10.03 under dark and 10.08 under light and reverse saturation current density of 34.9μA/cm2 under dark and 39.7μA/cm2 under light.
9
Ferro, Letícia Mariê Minatogau. "Fabricação de biossensor óptico de glicose em alumina anódica porosa." Universidade Federal de São Carlos, 2016. https://repositorio.ufscar.br/handle/ufscar/9002.
Full textAbstract:
Submitted by Milena Rubi (milenarubi@ufscar.br) on 2017-08-16T17:03:58Z
No. of bitstreams: 1
FERRO_Leticia_2016.pdf: 31138746 bytes, checksum: e2ec63a4c8fe8750b322f5f59e152466 (MD5)Approved for entry into archive by Milena Rubi (milenarubi@ufscar.br) on 2017-08-16T17:04:05Z (GMT) No. of bitstreams: 1 FERRO_Leticia_2016.pdf: 31138746 bytes, checksum: e2ec63a4c8fe8750b322f5f59e152466 (MD5)
Approved for entry into archive by Milena Rubi (milenarubi@ufscar.br) on 2017-08-16T17:04:12Z (GMT) No. of bitstreams: 1 FERRO_Leticia_2016.pdf: 31138746 bytes, checksum: e2ec63a4c8fe8750b322f5f59e152466 (MD5)
Made available in DSpace on 2017-08-16T17:04:19Z (GMT). No. of bitstreams: 1 FERRO_Leticia_2016.pdf: 31138746 bytes, checksum: e2ec63a4c8fe8750b322f5f59e152466 (MD5) Previous issue date: 2016-03-31
Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
Porous anodic alumina (PAA) has been used as platform for the manufacture of optical sensors. Itshows chemical resistance, thermal stability, hardness, biocompatibility, high surface area which facilitates interaction with the analyte and good morphological organization with the possibility to manipulate its pore size. Furthermore, PAA shows optical responses characterized by Fabry-Pérot interferences that can be obtained by photoluminescence and reflectance spectroscopy. Besides the surface of the AAP can be modified by Layer-by-Layer technique (LbL) in order to enhance optical sensors. Changes in Fabry-Pérot interferences can be monitored and analyzed as sensor responses. In this work, LbL film were deposited using hydrochloride polyallylamine (PAH) and glucose oxidase (GOx) for the purpose of manufacturing an optical biosensor for glucose detection. A protective bilayer of PAH and poly (vinyl sulfonic acid) (PVS) was assembled. The growth of the films were monitored by photoluminescence and total reflectance techniques. In addition, biosensor tests were carried out by immersing PAA in glucose solutions with different concentrations in order to check for changes in Fabry-Pérot oscillations. Analyzing the results, orderly growth of LbL film and biosensor response were verified. Results of the biosensor test were characterized by displacements of Fabry-Pérot interferences to shorter wavelengths and by multivariate analysis. Limit of detection determined by qualitative analysis of the Fabry-Pérot oscillations was 0.1 mol.L-1 to both PAA without surface modification and modified PAA. By using partial least squares (PLS) regression, it was possible to determine glucose from 0.1 mol.L-1 with PAA without modification and 0.01 mol.L-1 for PAA with LbL film. Furthermore, it was also verified the viability of using chemometrics to examine Fabry-Pérot interferences obtained with the PAA as an alternative method shown in the literature, which involves concepts of Fabry-Pérot equation.
A alumina anódica porosa (AAP) vem sendo utilizada como plataforma na fabricação de sensores ópticos por apresentar resistência química, estabilidade térmica, dureza, biocompatibilidade, grande área superficial que facilita a interação com o analito e boa organização morfológica com a possibilidade de se manipular as dimensões de seus poros. Além disso, a AAP apresenta respostas ópticas caracterizadas pelas interferências de FabryPérot, que podem ser obtidas por espectroscopia de fotoluminescência e de reflectância. A superfície da AAP ainda pode ser modificada pela técnica de deposição por camadas, Layerby-Layer (LbL), com o intuito de se aprimorar esses sensores ópticos, sendo que mudanças nas interferências de Fabry-Pérot podem ser acompanhadas e analisadas como resposta do sensor. Neste trabalho, houve a deposição de filmes LbL de polialilamina hidroclorada (PAH) e de glicose oxidase (GOx), contendo um colchão de PAH e de ácido poli(vinil sulfônico) (PVS), com a finalidade de fabricação de um biossensor óptico de glicose. O crescimento dos filmes foi acompanhado por fotoluminescência e reflectância total. Além disso, testes dos biossensores foram realizados imergindo a AAP em soluções de glicose com concentrações diferentes a fim de se verificar alterações nas oscilações apresentadas nos espectros. A partir dos resultados obtidos foram verificados o crescimento ordenado do filme LbL e a resposta do biossensor, que foi caracterizada pelo deslocamento das interferências de Fabry-Pérot para comprimentos de onda menores e por análise multivariada. O limite de detecção determinado através da análise qualitativa das oscilações de Fabry-Pérot foi de 0,1 mol.L-1 de glicose, tanto para a AAP sem modificação superficial, quanto para a modificada. Com o emprego da regressão por mínimos quadrados parciais (PLS, do inglês “partial least squares”) foi possível a determinação de glicose a partir de 0,1 mol.L-1 para a AAP sem modificação e de 0,01 mol.L-1 para a AAP com filme LbL. Além disso, foi verificada também a viabilidade de se utilizar a quimiometria para analisar as interferências de Fabry-Pérot obtidas com a AAP como um método alternativo do apresentado na literatura, que envolve conceitos da equação de Fabry-Pérot.
10
Zhou, Fan. "Growth mechanism of porous anodic films on aluminium." Thesis, University of Manchester, 2011. https://www.research.manchester.ac.uk/portal/en/theses/growth-mechanism-of-porous-anodic-films-on-aluminium(4e5601b4-9a30-4438-bb19-c93c71e75ec7).html.
Full textAbstract:
Fundamental research on the growth of porous anodic alumina (PAA) films has been undertaken for many years because of the complexity of the processes involved and the wide range of commercial applications. In this study, a tungsten tracer approach has been used to determine the influences of current density and electrolyte temperature on the incorporation of the tracer and its distribution and consequently, the growth mechanisms of PAA films. The efficiencies of growth of PAA films, formed during anodizing at 5 mA cm-2 in the three major forming acids at 25°C, are ~60%, due to loss of outwardly migrating Al3+ ions at the film/electrolyte interface. Thus, only the inwardly migrating O2- ions contribute to formation of the anodic oxide at the film/metal interface. The pores are developed due to flow of alumina from beneath the pore base regions toward the cell walls, which is indicated by distortion of the incorporated Al-W alloy layers and retention of the tungsten species within the anodic films. PAA films formed at a low range of current densities (<2 mA cm-2) develop by a field-assisted dissolution mode, with significant losses of aluminium and tungsten species to the electrolyte, and low expansion factors of less than 1.2. Conversely, films formed at current densities ≥2 mA cm-2 grow by a flow mechanism: flow of film material transports the alumina oxide, including the incorporated tungsten tracers, from the barrier layer regions to the cell walls, resulting in relatively thicker films at higher current densities and retention of the tungsten within the films. The tungsten remains mainly within the inner cell region of the films, with a tungsten-free region present next to the pore wall. The efficiency of film growth increases from ~0.29 to ~0.73 with increase of current density from 0.5 to 30 mA cm-2, and from ~0.26 to ~0.88 with increasing current density between 0.5 and 50 mA cm-2 for anodizing in sulphuric and oxalic acids respectively.Comparatively, for PAA films formed at 15 mA cm-2 in oxalic acid, reduction of electrolyte temperature from 20 to 1°C gives rise to a slight increase of the anodizing efficiency from ~0.67 to ~0.74; the film expansion factor also increases from ~1.32 to ~1.43. The previous arises from reduced field-assisted ejection of Al3+ ions at the decreased electrolyte temperature.Anodizing of the aluminium substrates in phosphoric acid or neutral phosphate solution generates barrier anodic alumina films and the barrier layers of porous films respectively, which comprise phosphorus-containing outer regions and a phosphorus-free inner regions. The phosphorus-containing outer region accounts for ~0.67 of the barrier films and the ~0.80 of the barrier layer of the porous films. Further, the distributions of phosphorus species are not significantly affected by the incorporation of the tungsten tracer nanolayer into the films; the influence of the phosphorus species on the outward migration of the tungsten species is also negligible.This tungsten tracer study suggests a significant influence of the flow of alumina oxide, under the high electric field, on the formation of PAA films at current densities ≥2 mA cm-2.
11
Gravani, Styliani. "Synthesis of nanomaterials via anodic aluminium oxide templates." Thesis, University of Surrey, 2014. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.616919.
Full textAbstract:
This thesis is concerned with the synthesis of 1 D nanomaterials via a template-assisted route. Porous anodic aluminium oxide templates prepared electrochemically have been utilised with two intrinsically different deposition techniques, sol-gel and high power pulsed magnetron sputtering (HPPMS), to obtain ID metal and metal oxide nanowires and nanotubes. The resultant morphologies and crystal structures were examined via SEM, XPS, XRD, TEM and EELS. A number of porous template alumina structures have been grown via the anodisation of pure and sputtered aluminium. The effects of surface pre-treatments, etching treatments and anodisation conditions on the resultant morphologies were investigated. It has been found that pore growth is largely dependent on the surface roughness of the substrate as well as the anodisation conditions. The anodisation duration is critical in promoting and allowing self-ordering. Obtained templates, varied in thickness from a few hundred run to several tens of pu-m, with an average pore diameter of 70 nm, interpore distance of 100 nm and pore density of 4 x 1010 cm2. . The implementation of HPPMS led to the successful deposition of Ti inside the alumina template to depths of around 45-50 run. It was found that templates with highly parallel pores on a rigid substrate such as Si, are more suited if this deposition method is to be used. Control of the pressure and substrate biasing is critical in avoiding 'pinch-off and 'bridging' and leading to complete pore filling. The results have shown that HPPMS is a promising plasma technology for the synthesis of nanomaterials such as nanodots, nanopillars or nanowires, when used with porous alumina templates under appropriate conditions. The use of sol-gel deposition has led to the growth of a number of interesting materials and structures. Nanocrystalline Ce02 and Ce1-xZrx02 and Ce1-xSmx02 thin films and powders have been successfully obtained exhibiting novel micro- and nano-structures, likely to find useful applications in catalysis and gas sensing due to their redox properties and large surface to volume ratio. FUlihermore, the treatment of porous alumina templates via a sol-gel/hydrothermal method led to the formation of Ce-doped y-Ah03 nanowires. Hence, a simple, direct and cost effective method for producing large scale Ah03 (and doped Ah03) nanowires is repotied. Moreover, by annealing at temperatures above 600 DC, nanowires of different crystallographic forms such as 0-, e- and a-Ah03 can also be readily obtained. As the dopant Ce was successfully introduced through this method a wide range of doped-Ah03 nanowires (by other rare eatihs such as Y, La, Gd, Srn), at various concentrations (e.g. 1,3,5 at. %) can be readily obtained.
12
El-Mashri, Saleh M. "Structure of anodic-oxide and hydrated oxide films on pure aluminium." Thesis, University of Warwick, 1985. http://wrap.warwick.ac.uk/108759/.
Full textAbstract:
The technique of electron yield-EXAFS has been used to derive information about the different structures of amorphous films, formed anodically on pure aluminium when various electrolyte solutions are used. It has been found that the uniform non-porous (barrier-type) oxide films which are formed in neutralised sodium tartrate or sodium borate electrolyte are amorphous and have an average Al-0 bond length of 0.190 nm. The amorphous oxide produced in neutralised sodium oxalate gives an average Al-0 separation of 0.185 nm, while the porous oxides formed in strong aggressive electrolytes, chromic acid and phosphoric acid, have an average Al-0 bond length of 0.183 nm and 0.180 nm respectively. Both the non-porous and the porous types of films have also been examined by high resolution scanning electron microscopy. The films formed in neutralised electrolytes show a structureless morphology, while the films prepared in strong acid are shown to have a porous morphology. All these oxide films become hydrated when exposed to hot water at 85°C. The time for complete hydration varies according to whether the film is porous or not. Electron yield-EXAFS analysis of these hydrated films yields two well defined Al-0 distances, 0.205 nm and 0.280 nm, which appear to be associated with the formation of an oxy-hydroxide similar in structure to boehmite. The SEM observation of these hydrated films shows a narked change in the micromorphology during hydration. A "cornflake" structure is developed which is related to the oxy-hydroxide structure (boehmite-like phase). These measured Al—O bond lengths derived from the EXAFS differ, depending on the nature of the anodising treatment, which suggests different states of aluminium-oxygen coordination. A possible model for the structure of amorphous alumina, based on this information, is proposed. These results are also discussed in relation to the structural chemistry of the hydration process.
13
Su, Zixue. "Porous anodic metal oxides." Thesis, University of St Andrews, 2010. http://hdl.handle.net/10023/1019.
Full textAbstract:
An equifield strength model has been established to elucidate the formation mechanism for the highly ordered alumina pore arrays and titanium oxide nanotubular arrays prepared via a common electrochemical methodology, anodisation. The fundamentals of the equifield strength model was the equilibrium between the electric field driven oxidation rate of the metal and electric field enhanced dissolution rate of oxide. During the anodic oxidation of metal, pore initiation was believed to generate based on dissolution rate difference caused by inhomogeneity near the metal/oxide interface. The ionic nanoconvection driven by the electric force exerted on the space charge layer in the vicinity of electrolyte/oxide interface is established to be the main driving force of the pore ordering at the early stage of the anodisation. While the equifield strength requirement governs the following formation of the single pore and the self-ordering of random distributed pore arrays during the anodisation process. Hexagonal patterned Al2O3 nanopore arrays and TiO2 nanotubular arrays have been achieved by anodisation of corresponding metal substrates in proper electrolytes. The two characteristic microstructural features of anodic aluminium oxide (AAO) and anodic titanium oxide (ATO) were investigated using scanning electron microscopy (SEM) and high resolution transmission electron microscopy (HRTEM). The observations of the hemispherical electrolyte/oxide and oxide/metal interfaces, uniform thickness of the oxide layer, as well as self-adjustment of the pore size and pore ordering can be well explained by the equifield strength model. Field enhanced dissociation of water is extremely important in determination of the porosity of anodic metal oxide. The porosity of AAO and ATO films was found to be governed by the relative dissociation rate of water which is dependent on anodisation conditions, such as electrolyte, applied voltage, current density and electric field strength. Using an empirical method, the relations between the porosity of the AAO (ATO) films and the anodisation parameters, such as electric field strength, current density and applied voltage, have been established. Besides, the extent that an external electric field can facilitate the heterolytic dissociation of water molecule has been estimated using quantum-chemical model computations combined with the experimental aspect. With these achievements, the fabrication of anodic metal oxide films can be understood and controlled more precisely. Additionally, the impacts of other factors such as the electrolyte type and the temperature effect on the morphology of the anodic products were also investigated. Some important experimental evidences on the pore diameters variation with applied voltage in the anodisation of aluminium and the titanium were obtained for future investigation of the anodic metal oxide formation processes.
14
Silva, Karina Rodrigues da. "Caracterização da alumina anódica porosa modificada por plasma." Universidade Federal de São Carlos, 2015. https://repositorio.ufscar.br/handle/ufscar/8331.
Full textAbstract:
Submitted by Milena Rubi (milenarubi@ufscar.br) on 2016-11-17T17:43:21Z
No. of bitstreams: 1
RODRIGUES_Karina_2015.pdf: 7918406 bytes, checksum: 5c7eded70cc8a9dd00ce5c1b2d70d846 (MD5)Approved for entry into archive by Milena Rubi (milenarubi@ufscar.br) on 2016-11-17T17:43:31Z (GMT) No. of bitstreams: 1 RODRIGUES_Karina_2015.pdf: 7918406 bytes, checksum: 5c7eded70cc8a9dd00ce5c1b2d70d846 (MD5)
Approved for entry into archive by Milena Rubi (milenarubi@ufscar.br) on 2016-11-17T17:43:39Z (GMT) No. of bitstreams: 1 RODRIGUES_Karina_2015.pdf: 7918406 bytes, checksum: 5c7eded70cc8a9dd00ce5c1b2d70d846 (MD5)
Made available in DSpace on 2016-11-17T17:43:54Z (GMT). No. of bitstreams: 1 RODRIGUES_Karina_2015.pdf: 7918406 bytes, checksum: 5c7eded70cc8a9dd00ce5c1b2d70d846 (MD5) Previous issue date: 2015-06-29
Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
In this study, the wettability of porous anodic alumina (PAA) surfaces modified by plasma was investigated. The porous anodic alumina films were grown on aluminum substrate using a two step anodization procedure in oxalic acid solution under potentiostatic regime. The surfaces of PAA films were modified by plasma treatment or plasma deposition techniques. Prior to surface modification, the impurities were removed by a plasma cleaning procedure. Oxygen was used in plasma treatment in order to produce hydrophilic surfaces. On the other hand, the plasma deposition (in HMDSO or HMDSO + argon mixture) was performed to produce hydrophobic surfaces or less hydrophilic surface. Electropolished aluminum without PAA film were used as reference. The influence of substrate morphology on wettability was analyzed. The morphological characterization was performed by scanning electron microscopy (SEM). The microstructural analysis was carried out using Fourier Transformed Infrared Spectroscopy (FTIR). A goniometer was used to measure the contact angle and evaluate the wettability of electroplished aluminum and PAA films. The results showed that the wettability of the samples was affect by chemical interactions of functional groups on the surface deposited after plasma treatment. The effect of the porous surface morphology on wettability was not significant compared to the plasma treated films with new chemical interactions effects.
Neste trabalho foram investigadas as propriedades de molhabilidade das superfícies nanoestruturadas da alumina anódica porosa (AAP) modificadas por plasma. Os filmes de AAP foram produzidos sobre substrato de alumínio pelo método de anodização potenciostática em duas etapas em solução de ácido oxálico. Após a fabricação, as amostras foram submetidas a um tratamento a plasma (com oxigênio) ou a deposição a plasma (em HMDSO ou em uma mistura de HMDSO e argônio). Antes das modificações das superfícies, removeram-se as impurezas das amostras através de técnicas de limpeza a plasma. No tratamento a plasma, o gás oxigênio foi utilizado para a obtenção de superfícies hidrofílicas. Por outro lado, para tornar a superfície hidrofóbica ou menos hidrofílica, foram feitas duas séries de deposição a plasma, uma contendo uma mistura de argônio e HMDSO e outra série somente com HMDSO. O tratamento ou deposição a plasma também foram feitas em amostras de alumínio eletropolido, sem a camada de AAP, a fim de verificar a influência morfológica do substrato na molhabilidade. A caracterização morfológica dos filmes de AAP foi feita por microscopia eletrônica de varredura (MEV), onde foi verificada a formação dos poros na superfície. A caracterização microestrutural foi feita por espectroscopia de absorção no infravermelho por transformada de Fourier (FTIR) com o objetivo de verificar as alterações químicas na superfície. A molhabilidade foi analisada utilizando um goniômetro, equipamento que realiza medição direta do ângulo de contato. Os resultados mostram que a molhabilidade da superfície é afetada por interações químicas dos grupos funcionais na superfície dos filmes. Por outro lado, o efeito da morfologia sobre a molhabilidade da superfície não é significativo nas condições estudadas.
15
Mohamed, Ali Keith. "Growth mechanism of porous anodic films formed on aluminium in sulphuric acid." Thesis, University of Manchester, 2010. https://www.research.manchester.ac.uk/portal/en/theses/growth-mechanism-of-porous-anodic-films-formed-on-aluminium-in-sulphuric-acid(6b8fd94a-2fba-44ab-81ca-f15fc8af5bb0).html.
Full textAbstract:
The present study is concerned with the mechanism of growth of porous anodic films formed on high purity aluminium and sputtering deposited aluminium over a wide range of current density between 5 to 50 mA/cm2 for times up to 5400 s in 24.5 wt % sulphuric acid and at temperatures of either 0 or 20 0C. The resultant films were examined using scanning electron microscopy (SEM), transmission electron microscopy (TEM), Rutherford backscattering spectroscopy (RBS), nuclear reaction analysis (NRA), optical interferometery, microhardness and nanoindentation.The RBS analysis enabled determination of the composition of the porous films, which was expressed as Al2O3.xAl2(SO4)3, with the sulphur species content increasing with increase in current density and decrease in temperature. The average expansion factor (expressing, the ratio of the film thickness to the oxidized aluminium thickness) increased between 5 mA/cm2 and 50 mA/cm2 for films formed at 0 0C, extending from 1.58 to 1.88 and from 1.57 to 1.78 according to SEM and TEM respectively. For films fabricated at 20 0C, the average expansion factor increased from 1.45 to 1.66 and from 1.42 to 1.67 derived from SEM and TEM respectively. The expansion factor increases as the current density increases for both temperatures, and decreases as electrolyte temperature for a given current density increases. The increase of expansion factor is also associated with a rise in the steady voltage during film growth. However, the film expansion does not depend on the anodizing time. The increase in expansion factor correlates with a small increase in the amount of sulphur in the film, which increases with rise of current density. The surface of the porous alumina revealed a network of furrows and ridges, reflecting the pattern of the cellular textures on the topography of the elecropolished aluminium. The retention of topography indicates that the thinning of the film due to chemical dissolution by the electrolyte is negligible, although softening of the film toward the film surface increases with rise of electrolyte temperature and anodizing time as determined by microhardness measurements on film cross-sections. For films fabricated at 0 0C, nodules appeared with a low population density on the film surfaces formed at 20 mA/cm2 for 5400 s, and a locally high population density, but non-uniform distribution, for films formed at 30 to 50 mA/cm2 for a wide range of anodizing times. NRA determined the oxygen concentrations in the films, from which the efficiency of the film grown was derived. The efficiency showed a correlation with the expansion factor, with values increasing with rise of current density and with decrease in the anodizing temperature, ranging from 72 % to 87 % between 5 mA/cm2 and 50 mA/cm2, for an electrolyte temperature of 0 0C, and between 66 % to 75 %, for the same range of current density, for an electrolyte temperature of 20 0C. The change in the relative film thickness with a change of the anodizing conditions might due to either a rise in the film porosity under a constant efficiency of film growth (assuming a flow model) or an increase in the efficiency of film growth for a constant film porosity (for either a flow or dissolution model), or a combination of the two factors. However, the film expansion appeared to be relatively little dependent on the change of the porosity over selected anodizing conditions. The dependence of the efficiency on the anodizing conditions is possibly associated with a change in the transport number of ion species in the film with a reducing contribution of cation migration to the total ionic current with an increase in the current density and in decrease of the anodizing temperature, which correspond to conditions of increasing electric field. The film porosity probably develops by flow of film material underneath the pore base toward the cell wall, as indicated by distribution of tungsten band through the film and distribution of electrolyte species from previous work, with the displaced material enhancing the thickness of the film.
16
Molchan, Tatsiana. "Generation of porous and nanotubular anodic films on titanium and titanium-aluminium alloy." Thesis, University of Manchester, 2014. https://www.research.manchester.ac.uk/portal/en/theses/generation-of-porous-and-nanotubular-anodic-films-on-titanium-and-titaniumaluminium-alloy(d20970de-6692-48e6-b5f6-3456bcec5e3e).html.
Full textAbstract:
This project was focused on the generation of porous and nanotubular anodic films on titanium and Ti-6wt.%Al alloy, and investigation of the key factors responsible for a transition between porous and nanotubular morphologies. Advanced analytical techniques were employed for characterisation of the anodic films, in particular scanning and transmission electron microscopies, including analytical transmission electron microscopy, Raman spectroscopy, nuclear reaction analysis, Rutherford backscattering spectroscopy and atomic force microscopy. Preparation of electron transparent sections for analysis by analytical transmission electron microscopy was undertaken using the focused ion beam technique. Initially, the influence of a post-anodizing rinsing treatment, using various media, on the morphology, structure and composition of anodic films generated on titanium in 0.2 M ammonium fluoride in glycerol, containing 0 and 5 vol.% added water, was investigated. Porous anodic films were formed in an electrolyte without added water followed by rinsing with ethanol. It was revealed that the oxide-rich nanotubes are embedded in a fluoride-rich matrix, with fluoride-rich material being more extensive and oxide-rich nanotubes being thinner-walled for the anodic films generated in the electrolyte with no added water followed by rinsing with ethanol compared with those for the films formed with added water to the electrolyte and rinsed similarly. However, post-anodizing rinsing of the former films transforms the porous morphology of the films to a tubular one. The contents of titanium and fluorine were reduced in the case of anodic films with the nanotubular morphology. It was suggested that dissolution of the fluoride-rich matrix occurs during rinsing of the specimens with water, leading to the transition from porous to nanotubular morphologies and subsequent loss of titanium and fluorine. Further work was undertaken to study the effect of ageing in deionised water on the morphology, structure and composition of the anodic films. It was revealed that loss of titanium and fluorine is greater for the films generated in the electrolyte with no added water followed by rinsing with water and ethanol and ageing compared with that for the films formed in the electrolyte with 5 vol.% added water followed by rinsing with water and ethanol and ageing. Finally, the anodic films generated on the Ti-6wt.%Al alloy were investigated. Porous anodic films were formed in the electrolyte without added water followed by rinsing with ethanol whereas the films treated with water disclosed nanotubular morphology. Porous anodic films contained greater amount of fluorine than nanotubular ones. Compositional analysis revealed an increased amount of fluorine for the anodic films generated on the alloy compared with those for the films formed on titanium under all investigated conditions. The difference in film compositions may be related to the difference in composition of the substrates used for anodizing, in particular, to the presence of aluminium as alloying element in the Ti-6wt.%Al alloy.
17
Liu, Guanjie. "Fabrication and characterization of highly ordered porous anodic oxide and nanowires." Thesis, University of Manchester, 2010. https://www.research.manchester.ac.uk/portal/en/theses/fabrication-and-characterization-of-highly-ordered-porous-anodic-oxide-and-nanowires(35726d34-3d20-40d4-ab12-89b931c05691).html.
Full textAbstract:
Porous anodic films with highly ordered pores were successfully fabricated with multi-steps anodizing. The degree of pore ordering was quantitatively assessed by obtaining the pore distribution regularity based on fast Fourier transform (FFT) of scanning electron micrographs of the resultant porous anodic films. It is revealed that the degree of pore ordering in anodic films increases with increased number of repeated steps of anodizing. Anodizing conditions, i.e. anodizing voltage and the electrolyte concentration, are found to have significant effects on pore ordering. The best regularity was recorded on the porous anodic films formed at 30 V in 0.3 M oxalic acid and 40 V in 0.4 M oxalic acid. Further, anodic oxide films, with pores arranged in hexagonal or square patterns, were obtained by anodizing of aluminium with corresponding pre-patterns induced by optic grating impressions under selected anodizing voltages. Additionally, anodic film templates were successfully fabricated using optimised procedures with selective removal of the aluminium substrate and the barrier oxide layer. Nickel nanowires were produced by electrodeposition using anodic film templates. The current density-time response reveals three growth stages of nickel nanowires during electrodeposition. The electrodeposition current efficiency varied with the variation of electrodeposition parameters, mainly due to side reactions i.e. hydrogen evolution. The process temperature and applied voltage have a significant influence on the growth rate of nickel nanowires. Further, the structure of the resultant nickel nanowires depends on the process temperature. At a process temperature of 3°C, single crystal nanowires grew preferentially along [110] orientation. However, polycrystalline nanowires were obtained at an increased temperature of 37°C due to the increased surface diffusion rate of nickel adatoms. Optical limiting assessment of the nickel nanowires revealed significant non-linear scattering in the wavelength range of 532 to 1064 nm, suggesting potential applications in the fields of ultrahigh-density magnetic recording, ultrafast optical switching and microwave devices. Manganese oxide nanowires were also fabricated via the anodic film template route in a mixed solution of 0.1 M manganese acetate and 0.1 M sodium sulphate. The resultant nanowires exhibit an amorphous structure with short range ordering. A high population of fine crystalline particles, with an average diameter of 3~5 nm, was revealed within the nanowires. The crystalline particles were determined as ε-Manganese dioxide with a hexagonal structure. Further, a high specific capacitance of 220 F g-1 was recorded on the electrode fabricated from the deposited manganese oxide nanowire array in a cyclic voltammetry measurement at a scan rate of 5 mV s-1 from 0 to 1 V (SCE) in 0.1 M sodium sulphate solution at 25°C , indicating excellent capacitive properties.
18
Orsi, Alice. "Control of aluminium anodization to regulate the optical properties of porous aluminium oxide membranes." Thesis, Imperial College London, 2013. http://hdl.handle.net/10044/1/11137.
Full textAbstract:
Porous alumina anodized (PAA) membranes are widely used as templates for electrodeposition of conductive materials or directly as photonic material [1-3] due to the regular distribution of pores when anodized under defined temperature, electrolyte and voltage. This thesis investigated PAA nucleation and development under constant voltage in order to develop a periodic anodizing procedure to control pore diameter and interpore distance along the pore main axis. The periodic change in the geometrical parameters modifies the optical properties of the membranes and visible light interacts with the porous membrane when the periodicity of the structure is of the same order as the light wavelength. Two porous structures with reflectance peaks in the visible range were realized and their optical properties were studied. Branched membranes presented alternated layers of branched pore and main pore layers of controllable thicknesses. The reflectance spectra was modelled as a Bragg stack whose thicknesses and refractive indices of the alternating layers were obtained from ellipsometrical and SEM measurements of PAA membranes. The second structure was defined as necked membrane, as it presented periodic enlargements and restrictions of pore diameter along the pore main axis without branching. Reflectance spectra showed a single peak in the visible range whose position could be controlled by the anodizing temperature. Reflectance spectra showed by branched and necked samples were considered promising with regards to applications as interleaved reflectors in reflective displays. The presence of selective reflective layers interleaved in a stack display reduces light losses due to undesired absorbance of colour layers and more freedom in display design. [4] 1. Wang, B., et al., Preparation of photonic crystals made of air pores in anodic alumina. Nanotechnology, 2007. 18: p. 1. 2. Zheng, W.J., et al., Modulation of Transmission Spectra of Anodized Alumina Membrane Distributed Bragg Reflector by Controlling Anodization Temperature. Nanoscale Research Letters, 2009. 4(7): p. 665. 3. Zheng, W.J., et al., Distributed Bragg reflector made of anodic alumina membrane. Materials Letters, 2009. 63(8): p. 706. 4. Kitson, S., et al., Bright color reflective displays with interlayer reflectors. Optics Express, 2011. 19(16): p. 15404.
19
Ng, King-yeung, and 吳競洋. "An investigation of the deformation of anodic aluminium oxide nano-honeycomb during nanoindentation." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2009. http://hub.hku.hk/bib/B42841240.
Full text
20
Ng, King-yeung. "An investigation of the deformation of anodic aluminium oxide nano-honeycomb during nanoindentation." Click to view the E-thesis via HKUTO, 2009. http://sunzi.lib.hku.hk/hkuto/record/B42841240.
Full text
21
Calavia, Boldú Raúl. "Gas sensor microsystems based on nanostructured layers via anodic oxidation." Doctoral thesis, Universitat Rovira i Virgili, 2012. http://hdl.handle.net/10803/96314.
Full textAbstract:
En aquesta tesi es detalla la metodologia per obtindre sensors de gasos basats en òxid de tungstè nanoestructurat sobre suports micromecanitzats de silici. Aquesta nanoestructuració s’ha fet mitjançant una capa d’alúmina porosa como a motlle, pel que s’ha desenvolupat una metodologia per a compatibilitzar l'anodització de l’alumini, i altres metalls com el tungstè, amb els processos estàndards del silici.
S’han desenvolupat dos tipus de capes nanoestructurades, nanotubs i nanopunts de WO3. Els nanotubs s’han obtingut depositant mitjançant polvorització catòdica reactiva la capa sensible sobre alúmina porosa recobrint les parets dels pors.
Els nanopunts s’han obtingut anoditzant una bicapa d’alumini i tungstè, on la primera anodització crea la alúmina porosa i la segona fa créixer els nanopunts d’òxid de tungstè en la base dels pors.
S’ha analitzat la composició, morfologia i funcionament com a sensors de gasos d’ambdós materials nanoestructurats i s’han comparat els resultats amb sensors basats en materials sense nanoestructuració.En esta tesis se detalla la metodologia para obtener sensores de gases basados en óxido de tungsteno nanoestructurado sobre soportes micromecanizados de silicio. Dicha nanoestructuración se ha obtenido empleando una capa de alúmina porosa como molde, por lo que se desarrolla una metodología para compatibilizar la anodización del aluminio, y otros metales como el tungsteno, con los procesos estándares del silicio. Se han desarrollado dos tipos de capas nanoestructuradas, nanotubos y nanopuntos de WO3. Los nanotubos se han obtenido depositando por pulverización catódica reactiva la capa sensible sobre alúmina porosa recubriendo las paredes de sus poros. Los nanopuntos se han obtenido anodizando una bicapa de aluminio y tungsteno, donde la primera anodización crea la alúmina porosa y la segunda hace crecer los nanopuntos de óxido de tungsteno en la base de los poros. Se ha analizado la composición, morfología y funcionamiento como sensores de gases en ambos casos y se han comparado los resultados con los de sensores sin nanoestructuración.
This thesis shows the methodology to obtain nanostructured tungsten oxide layer as sensing material on silicon micromachined gas sensor devices. A porous anodised alumina layer was used as pattern to obtain it, so a technique has been developed to make compatible the anodising of aluminium and other metals like tungsten with the standard silicon processes. Two different nanostructuring approaches were developed, nanotube and nanodot based tungsten oxide layers. The WO3 nanotube layer has been obtained by the tungsten oxide deposition using reactive sputtering on the porous alumina layer. As a result a continuous sensing layer coats the pores without clogging them. WO3 nanodot layers were obtained by the anodising of an aluminium and tungsten bilayer, where the first anodising process grows the porous alumina layer and the second one generates the tungsten oxide nanodots in the end of the pores. Compositional and morphological studies and the study of their behaviour as gas sensors where conducted for the two nanomaterials. The results have been compared with the flat tungsten oxide layers on micromachined gas sensors.
22
Muratore, Francesca. "Growth of porous anodic films on zirconium and zirconium alloys in glycerol/fluoride electrolytes." Thesis, University of Manchester, 2011. https://www.research.manchester.ac.uk/portal/en/theses/growth-of-porous-anodic-films-on-zirconium-and-zirconium-alloys-in-glycerolfluoride-electrolytes(ce98e6f6-e743-47b2-b1c4-7b0fd6797003).html.
Full textAbstract:
Anodic films have been produced on zirconium and zirconium alloys potentiostatically (at either 20 or 40 V) in 0.35 M ammonium fluoride in glycerol, with interest in the addition of small amounts of water (up to 5 vol.%) to the electrolyte on their growth, morphologies and compositions. Scanning and transmission electron microscopies have been employed to analyse morphologies of the films, which appeared to be porous under all the investigated conditions.Rutherford backscattering spectroscopy and nuclear reaction analysis, used as techniques to investigate film compositions, disclosed the presence of zirconium, oxygen, fluorine, carbon and nitrogen in the films. The contents of fluorine and oxygen in the films were found to increase and decrease respectively by decreasing the amount of water added to the electrolyte from 5 to 0 vol.%. Moreover, the content of fluorine increased by decreasing the applied formation voltage, from 40 to 20 V, for films formed in electrolytes containing similar amounts of added water.In order to get information on the distribution of the species in the films, cross-sections of selected specimens were produced by focused ion beam and analysed by analytical transmission electron microscopy. Oxide-rich nanotubes were revealed embedded in a fluoride-rich matrix, suggesting that the mechanism of growth of the anodic films is governed by different migration rates of the anionic species in the film base, with F- ions, being the fastest anions. The relative amounts of the oxide-rich and fluoride-rich materials were related to the composition of the electrolyte, with the fluoride regions being less extensive and the oxide-rich nanotubes being thicker-walled by adding small amounts of water. Moreover, nanotubes are constituted of two shells (an outer one surrounding the pores and an inner one located between the outer shell and the matrix), suggesting differences in the composition in these two regions, presumed to be due to the incorporation of carbon species, being the slowest migrating species, in the outer shell. The fluoride-rich matrix chemically dissolved following 1 h immersion of the specimens in the formation electrolytes, promoting the transition from porous to nanotubular morphologies. Ageing of the specimens in deionized water for similar times did not significantly influence the morphologies and compositions of the anodic films.
23
Lee, Jongmin [Verfasser], Ulrich [Akademischer Betreuer] Gösele, and Peter [Akademischer Betreuer] Woias. "Thermoelectric bismuth-related nanowires based on anodic aluminium oxide membranes / Jongmin Lee. Betreuer: Ulrich Gösele ; Peter Woias." Halle, Saale : Universitäts- und Landesbibliothek Sachsen-Anhalt, 2009. http://d-nb.info/1024895629/34.
Full text
24
Karlsson, Marjam. "Nano-porous Alumina, a Potential Bone Implant Coating." Doctoral thesis, Uppsala : Acta Universitatis Upsaliensis, 2004. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-4452.
Full text
25
Tian, Zhipeng. "Nanopore/Nanotube Pattern Formation through Focused Ion Beam Guided Anodization." Thesis, Virginia Tech, 2010. http://hdl.handle.net/10919/46207.
Full textAbstract:
Anodization is a kind of method that can produce oxide layer in a large area and on flexible shaped metals. In some specific conditions, anodic oxide layers exhibit interesting nanopore/nanotube structures. In this work, focused ion beam patterning method is introduced to general anodization, aiming to make highly ordered anodic porous alumina and titania nanotubes.
Focused ion beam guided porous anodic alumina is carried out by pre-designing hexagonal and square guiding patterns with different interpore distances on well electropolished Al foil before anodization. After anodization, the guiding interpore distance is found to affect the new poresâ locations and shapes. Two important elements, electrical field and mechanical stress, are discussed for the development of the guiding pores and the generation of new pores. Based on the proposed pore growth mechanism, novel patterns, non-spherical pores, and large patterns across the grain boundaries are successfully produced.
The research on focused ion beam guided anodic titania nanotubes begins with surface polishing. The influence of four polishing conditions, as-received, chemically polished, mechanically polished, and electropolished samples, are investigated. A polished smooth sample provides a desired surface for focused ion beam guided anodization. Hexagonal guiding patterns with different interpore distances are created on Ti surface. Ordered nanotube arrays are produced, and the structure of the anodized guiding pattern is identified.Master of Science
26
Meyer, Daniel. "Korrelationen zwischen Herstellungsprozess, Struktur und Eigenschaften von anodischen Aluminiumoxidschichten für Verschleißschutzanwendungen." Doctoral thesis, Universitätsbibliothek Chemnitz, 2017. http://nbn-resolving.de/urn:nbn:de:bsz:ch1-qucosa-228257.
Full textAbstract:
Das Ziel dieser Dissertation besteht darin, einen Beitrag zur technologischen, ökonomischen und ökologischen Weiterentwicklung der anodischen Verfahren zur Oberflächenkeramisierung von Aluminium zu leisten. Die Arbeit ist in zwei thematische Schwerpunkte untergliedert. Im ersten Teil wird für die Hartanodisation eine hinsichtlich eines geringeren Energieeinsatzes optimierte Elektrolytzusammensetzung identifiziert und mit einem optimierten galvanostatischen Pulsmuster simultan appliziert. Im Ergebnis kann die Gesamtleistungsaufnahme um ca. 6 % reduziert werden, ohne die mechanischen Eigenschaften der Oxidschichten zu mindern. Im zweiten Schwerpunkt werden das Lichtbogen- und das Flammspritzen mit der plasmaelektrolytischen anodischen Oxidation kombiniert, um verschleißbeständige Aluminiumoxidschichten auf Stahl-, Titan- und Magnesiumsubstraten zu applizieren. Neben einer umfangreichen Mikrostrukturanalyse (REM, EDX, XRD, EBSD) werden die mechanischen Eigenschaften der Schichten untersucht und mit atmosphärisch plasmagespritzten Al2O3-Schichten verglichen. Insbesondere Oxidschichten auf lichtbogengespritztem AlCu4Mg1 zeigen dabei eine hohe Härte sowie eine sehr gute VerschleißbeständigkeitThe aim of the present work is to contribute to the technological, economic and ecological improvement of the anodic processes for the surface ceramization of aluminum. The work is subdivided into two thematic priorities. In the first part, for the hard anodizing process an optimized electrolyte composition for a lower energy input is identified and applied simultaneously with an optimized galvanostatic pulse regime. As a result, the total power consumption can be reduced by approximately 6% without reducing the mechanical properties of the oxide coatings. In the second focus, arc and flame spraying are combined with plasma electrolytic anodic oxidation to apply wear resistant aluminum oxide coatings on steel, titanium and magnesium substrates. In addition to a comprehensive microstructural analysis (SEM, EDX, XRD, EBSD), the mechanical properties of the layers are investigated and compared with atmospheric plasma sprayed Al2O3 coatings. In particular, oxide layers formed on arc sprayed AlCu4Mg1 coatings show a high hardness as well as very good wear resistance
27
Singhal, Dhruv. "Forêt de nanofils semiconducteurs pour la thermoélectricité." Thesis, Université Grenoble Alpes (ComUE), 2019. http://www.theses.fr/2019GREAY016/document.
Full textAbstract:
La conversion thermoélectrique a suscité un regain d'intérêt en raison des possibilités d'augmenter l'efficacité tout en exploitant les effets de taille. Par exemple, les nanofils montrent théoriquement une augmentation des facteurs de puissance ainsi qu'une réduction du transport des phonons en raison d'effets de confinement et/ou de taille. Dans ce contexte, le diamètre des nanofils devient un paramètre crucial à prendre en compte pour obtenir des rendements thermoélectriques élevés. Une approche habituelle consiste à réduire la conductivité thermique phononique dans les nanofils en améliorant la diffusion sur les surfaces tout en réduisant les diamètres.Dans ce travail, la caractérisation thermique d'une forêt dense de nanofils de silicium, germanium, silicium-germanium et alliage Bi2Te3 est réalisée par une méthode 3-omega très sensible. Ces forêts de nanofils pour le silicium, le germanium et les alliages silicium-germanium ont été fabriqués selon une technique "bottom-up" suivant le mécanisme Vapeur-Liquide-Solide en dépôt chimique en phase vapeur. La croissance assistée par matrice et la croissance par catalyseurs en or des nanofils à diamètres contrôlés ont été réalisés à l'aide d'alumine nanoporeuse comme matrice. Les nanofils sont fabriqués selon la géométrie interne des nanopores, dans ce cas le profil de surface des nanofils peut être modifié en fonction de la géométrie des nanopores. Profitant de ce fait, la croissance à haute densité de nanofils modulés en diamètre a également été démontrée, où l'amplitude et la période de modulation peuvent être facilement contrôlées pendant la fabrication des matrices. Même en modulant les diamètres pendant la croissance, les nanofils ont été structurellement caractérisés comme étant monocristallins par microscopie électronique à transmission et analyse par diffraction des rayons X.La caractérisation thermique de ces nanofils a révélé une forte diminution de la conductivité thermique en fonction du diamètre, dont la réduction était principalement liée à une forte diffusion par les surfaces. La contribution du libre parcours moyen à la conductivité thermique observée dans ces matériaux "bulk" varie beaucoup, Bi2Te3 ayant une distribution en libre parcours moyen (0,1 nm à 15 nm) très faible par rapport aux autres matériaux. Même alors, des conductivités thermiques réduites (~40%) ont été observées dans ces alliages attribuées à la diffusion par les surfaces et par les impuretés. D'autre part, le silicium et le germanium ont une conductivité thermique plus élevée avec une plus grande distribution de libre parcours moyen. Dans ces nanofils, une réduction significative (facteur 10 à 15 ) a été observée avec une forte dépendance avec la taille des nanofils.Alors que les effets de taille réduisent la conductivité thermique par une meilleure diffusion sur les surfaces, le dopage de ces nanofils peut ajouter un mécanisme de diffusion par différence de masse à des échelles de longueur atomique. La dépendance en température de la conductivité thermique a été déterminée pour les nanofils dopés de silicium afin d'observer une réduction de la conductivité thermique à une valeur de 4,6 W.m-1K-1 dans des nanofils de silicium fortement dopés avec un diamètre de 38 nm. En tenant compte de la conductivité électrique et du coefficient Seebeck calculé, on a observé un ZT de 0,5. Avec l'augmentation significative de l'efficacité du silicium en tant que matériau thermoélectrique, une application pratique réelle sur les appareils n'est pas loin de la réalitéThermoelectric conversion has gained renewed interest based on the possibilities of increasing the efficiencies while exploiting the size effects. For instance, nanowires theoretically show increased power factors along with reduced phonon transport owing to confinement and/or size effects. In this context, the diameter of the nanowires becomes a crucial parameter to address in order to obtain high thermoelectric efficiencies. A usual approach is directed towards reducing the phononic thermal conductivity in nanowires by achieving enhanced boundary scattering while reducing diameters.In this work, thermal characterisation of a dense forest of silicon, germanium, silicon-germanium and Bi2Te3 alloy nanowires is done through a sensitive 3ω method. These forest of nanowires for silicon, germanium and silicon-germanium alloy were grown through bottom-up technique following the Vapour-Liquid-Solid mechanism in Chemical vapour deposition. The template-assisted and gold catalyst growth of nanowires with controlled diameters was achieved with the aid of tuneable nanoporous alumina as templates. The nanowires are grown following the internal geometry of the nanopores, in such a case the surface profile of the nanowires can be modified according to the fabricated geometry of nanopores. Benefiting from this fact, high-density growth of diameter-modulated nanowires was also demonstrated, where the amplitude and the period of modulation can be easily tuned during the fabrication of the templates. Even while modulating the diameters during growth, the nanowires were structurally characterised to be monocrystalline through transmission electron microscopy and X-ray diffraction analysis.The thermal characterisation of these nanowires revealed a strong diameter dependent decrease in the thermal conductivity, where the reduction was predominantly linked to strong boundary scattering. The mean free path contribution to the thermal conductivity observed in the bulk of fabricated nanowire materials vary a lot, where Bi2Te3 has strikingly low mean free path distribution (0.1 nm to 15 nm) as compared to the other materials. Even then, reduced thermal conductivities (~40%) were observed in these alloys attributed to boundary and impurity scattering. On the other hand, silicon and germanium have higher thermal conductivity with a larger mean free path distribution. In these nanowires, a significant reduction (10-15 times) was observed with a strong dependence on the size of the nanowires.While size effects reduce the thermal conductivity by enhanced boundary scattering, doping these nanowires can incorporate mass-difference scattering at atomic length scales. The temperature dependence of thermal conductivity was determined for doped nanowires of silicon to observe a reduction in thermal conductivity to a value of 4.6 W.m-1K-1 in highly n-doped silicon nanowires with 38 nm diameter. Taking into account the electrical conductivity and calculated Seebeck coefficient, a ZT of 0.5 was observed. With these significant increase in the efficiency of silicon as a thermoelectric material, a real practical application to devices is not far from reality
28
Sieber, Maximilian. "Elektrochemisches Modell zur Beschreibung der Konversion von Aluminium durch anodische Oxidation." Doctoral thesis, Universitätsbibliothek Chemnitz, 2017. http://nbn-resolving.de/urn:nbn:de:bsz:ch1-qucosa-216761.
Full textAbstract:
Durch elektrochemische Impedanzspektroskopie während der anodischen Oxidation von Aluminium werden in der vorliegenden Arbeit die elektrochemischen Vorgänge während der Oxidbildung quantitativ und zeitabhängig untersucht. Es wird ein Modell vorgeschlagen und diskutiert, welches das Impedanzverhalten während der anodischen Oxidation in Schwefel-, Oxal- und Phosphorsäure über einen großen Bereich von Konzentrationen und Stromdichten abbilden kann. Aus den gewonnenen Ergebnissen werden die kapazitive Wirkung der Sperrschicht am Porengrund, der Eintritt von Ladungsträgern in die Sperrschicht, der Ionentransport durch die Sperrschicht sowie die Oxidbildungsreaktion selbst als wesentlich für das Impedanzverhalten identifiziert. Die ermittelten Zusammenhänge und Konstanten können als Grundlage für Modellvorstellungen dienen, welche das Verhalten elektrischer Prozessgrößen und die Ausbildung der charakteristischen Oxidstruktur bei der anodischen Oxidation von Aluminium verknüpfenIn the present work, the electrochemical subprocesses of the oxide formation on aluminium by anodic oxidation are investigated using electrochemical impedance spectroscopy. The time dependence of the impedance behaviour and the quantitative relations between the process parameters and the impedance behaviour are considered. A model for the representation of the electrochemical behaviour during the anodic oxidation in sulphuric, oxalic and phosphoric acid is proposed and discussed for a wide range of anion concentrations and current densities. On the basis of the obtained results, the capacitive effect of the barrier layer, the charge transfer resistance of the barrier layer, the ion transport within the barrier layer and the oxide formation are identified as the dominating effects for the impedance behaviour. The established relations can serve as a basis for models, which interrelate both the electrochemical behaviour and the geometrical formation of the characteristic pore structure
29
Shingne, Nitin [Verfasser], Thomas [Akademischer Betreuer] Thurn-Albrecht, Jörg [Akademischer Betreuer] Kreßler, and Bernd [Akademischer Betreuer] Stühn. "Morphology and crystal orientation of ferroelectric P(VDF-ran-TrFE) nanostructures in porous aluminium oxide / Nitin Shingne. Betreuer: Thomas Thurn-Albrecht ; Jörg Kreßler ; Bernd Stühn." Halle, Saale : Universitäts- und Landesbibliothek Sachsen-Anhalt, 2011. http://d-nb.info/1025201884/34.
Full text
30
Baldé, Mamadou Saliou. "Etude et développement de microtechnologies sur substrat papier : application à la structuration d'AL2O3 poreux pour la faisabilité d'un capteur d'humidité." Thesis, Montpellier 2, 2013. http://www.theses.fr/2013MON20065.
Full textAbstract:
L'objectif premier de ce projet est la mise au point de procédés de fabrication microélectroniques/microtechnologiques compatibles avec l'utilisation d'un support papier. Pour cela, des techniques comme l'évaporation thermique sous vide, la photolithographie, l'électrodéposition et l'anodisation d'aluminium ont été développées et adaptées à ce support. Des bancs de caractérisations structurels, électriques et flexibles ont été aussi mis en œuvre pour étudier la fiabilité des couches déposées sur un tel substrat. En application, un capteur d'humidité à base d'oxyde d'aluminium flexible a été fabriqué et les tests en humidité ont montré d'excellents résultats permettant de valider le travail effectuéThe primary objective of this project is the implementation of microelectronics/microtechnology processes compatible with the use of paper-based substrate. For this purpose, techniques such as thermal vacuum evaporation, photolithography, electroplating and anodizing aluminum have been developed and adapted to this substrate. Structural, electrical and flexible characterizations benches have also been implemented to study the reliability of the layers deposited on such substrate. A moisture sensor based on flexible aluminum oxide was made and humidity tests have shown excellent results which validate the work
31
Carossi, Lory Cantelli. "Propriedades ópticas da alumina anódica porosa e o efeito do guia de onda." Universidade Federal de São Carlos, 2015. https://repositorio.ufscar.br/handle/ufscar/9003.
Full textAbstract:
Submitted by Milena Rubi (milenarubi@ufscar.br) on 2017-08-16T17:19:17Z
No. of bitstreams: 1
CAROSSI_Lory_2017.pdf: 61131706 bytes, checksum: 687def06b5a758fcb457d49f53a494b1 (MD5)Approved for entry into archive by Milena Rubi (milenarubi@ufscar.br) on 2017-08-16T17:19:27Z (GMT) No. of bitstreams: 1 CAROSSI_Lory_2017.pdf: 61131706 bytes, checksum: 687def06b5a758fcb457d49f53a494b1 (MD5)
Approved for entry into archive by Milena Rubi (milenarubi@ufscar.br) on 2017-08-16T17:19:33Z (GMT) No. of bitstreams: 1 CAROSSI_Lory_2017.pdf: 61131706 bytes, checksum: 687def06b5a758fcb457d49f53a494b1 (MD5)
Made available in DSpace on 2017-08-16T17:19:39Z (GMT). No. of bitstreams: 1 CAROSSI_Lory_2017.pdf: 61131706 bytes, checksum: 687def06b5a758fcb457d49f53a494b1 (MD5) Previous issue date: 2015-02-11
Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
Nanoporous anodic alumina films (NAA) may present different behavior to reflectance and photoluminescence techniques, with Fabry-Pérot interferences and waveguide properties. This phenomenon makes possible the use of NAA as transducer signal in optical sensors. In this work, we investigated how the pre-treatment, the number of steps of anodizing, the anodizing electrolyte mode and temperature affect electrochemical characteristics, morphological and optical mainly NAA. As a result, it was noticeable that the realization of electropolishing is necessary for both the NAA with good regularity as to make it possible to obtain a spectrum with the Fabry-Pérot interference. If the fabrication of NAA is done in two steps, it is possible to obtain reflectance spectra and luminescence fringed with better amplitudes, areas and heights. Regarding the anodizing mode, both the NAA anodized in galvanostatic how potentiostatic showed similar morphologies and spectra with fringes, but the interferences were better defined when the galvanostatic mode was performed. Regarding the temperature, it was noticeable that the change of this parameter leads influences the porous oxide thickness. The spectrum of the luminescence and reflectance increasing the electrolyte temperature caused an increase in interference. However, the range and resolution of interference decreased with increasing temperature. The oxide thicknesses were estimated by energy variation (?E), graph slope between order and 1/? and fast Fourier transform (FFT) techniques. The ratio of film thickness and pore diameter (L/dp) was performed to validate the NAA films with better waveguides property. Moreover, the surface composition analysis of NAA films anodized in phosphoric acid, oxalic acid and mixtures thereof by backscattering spectroscopy Rutherford (RBS) was performed. From simulations it was possible to note that the amount of carbon in the porous oxide structure is practically zero, which may indicate that the origin of the luminescence is related to the presence of more centers F.
Filmes de alumina anódica porosa (AAP) podem apresentar, espectros de reflectância e luminescência com interferências de Fabry-Pérot e propriedades de guias de onda. Esse fenômeno possibilita que a AAP possa ser utilizada como plataforma em sensores ópticos. Neste trabalho, foi investigado como o pré-tratamento, o número de etapas de anodização, o modo de anodização e a temperatura do eletrólito afetam características eletroquímicas, morfológicas e principalmente ópticas da AAP. Como resultado, foi possível notar que a realização do eletropolimento é necessário para obter tanto a AAP com boa regularidade como para que seja possível obter um espectro com as interferências Fabry-Pérot. Se a fabricação da AAP for feita em duas etapas, é possível obter espectros de reflectância e luminescência com franjas com melhores amplitudes, áreas e alturas. Com relação ao modo de anodização, tanto as AAPs anodizadas em modo galvanostático como potenciostático apresentaram morfologias semelhantes e espectros com franjas, mas as interferências foram melhor definidas quando o modo galvanostático foi realizado. Com relação à temperatura, foi possível notar que a mudança desse parâmetro ocasiona influencia na espessura do óxido poroso. Quanto aos espectros de luminescência e reflectância, o aumento da temperatura do eletrólito ocasionou um aumento no número de interferências. Entretanto, a amplitude e a resolução das interferências diminuíram com o aumento da temperatura. A espessura do filme poroso foi estimada pelas técnicas de variação de energia (?E), coeficiente angular do gráfico entre ordem da interferência e 1/? e através da transformada rápida de Fourier (FFT). E foi utilizada a razão entre a espessura do filme e diâmetro do poro (Esp/Dp) para averiguar os filmes de AAP com guias de onda que pudessem ser utilizadas como substratos para sensores ópticos. Além disso, foi realizada a análise de composição superficial dos filmes de AAP anodizados em ácido fosfórico, oxálico e mistura destes ácidos pela técnica de espectroscopia de retroespalhamento de Rutherford (RBS). A partir das simulações realizadas foi possível notar que a quantidade que carbono na estrutura do oxido poroso é praticamente nula, o que pode indicar que a origem da luminescência está relacionada à presença dos centros F.
32
Johansson, Anders. "Template-Based fabrication of Nanostructured Materials." Doctoral thesis, Uppsala : Acta Universitatis Upsaliensis, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-7364.
Full text
33
Appusamy, Boopathy Harish, and Pavan Kumar Bonthala. "Electrochemical etching and anodizing as key stages of surface treatment of aluminium foil for electrolytic capacitor industry : Application of Electro Chemical Impedance Spectroscopy as non-destructive characterization of etched anode foil with an anodized dielectric oxide layer." Thesis, Tekniska Högskolan, Högskolan i Jönköping, JTH, Produktutveckling, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:hj:diva-37858.
Full textAbstract:
In the initial stage, the sample preparation was done by using the techniques of Anodic etching and anodic forming processes where a repeated trial and error method of sample preparation headed towards making out a suitable sample set for characterization. After this step, the set of 2 different industrial samples were introduced and anodic oxide forming process was carried out in different electrolytes. In the sample preparations, 4 different electrolytes were used 15% wt. Ammonium Adiphate, 1.5% wt. Ammonium Phosphate, 7% wt. Boric acid and 15% Penta Borate at different stages for performing the anodic oxide forming process. Minimum forming voltages of 20V to a maximum of 100V was employed in the sample preparation and to overcome the waiting time in forming the etched samples a higher current of 0.5A was used. After the samples preparation, Electrochemical Impedance spectroscopy was used as a tool for characterising the various groups of samples and for observing the micro structures of various samples, they were fractured and the observed on the cross section by SEM. After the analysis of the etched samples was made, an attempt to compare the results of the data of these samples to that of the 2 set of industrial samples was made and found that the resultant data wasn’t stable enough to characterize since huge scattering were occurring and whereby the simulation of the CPE circuit for the chosen circuit in the analysis was not possible. Under the analysis, a randomly chosen industrial sample was also used and the resultant data was utilised in understanding the response of the system to different electrolytes.Sammanfattning Avhandlingsarbetet har genomförts på KEMET AB i samarbete med yttekniklaboratoriet vid JTH i syfte att karakterisera den etsade anodiska aluminiumfolien som grundprov med anodisering och etsning för ytbehandling. I inledningsskedet gjordes provberedningen med användning av teknikerna för anodisk etsning och anodbildande processer där en upprepad provnings- och felmetod för provberedning ledde ut mot att utarbeta en lämplig provuppsättning med avseende på karakterisering. Efter detta steg infördes uppsättningen av 2 olika industriella prover och anodoxidbildande process utfördes i olika elektrolyter. I provpreparaten användes 4 olika elektrolyter 15 % vikt Ammoniumadiphat, 1,5 vikt% Ammoniumfosfat, 7 vikt% Borsyra och 15 % Penta-borat vid olika steg för utförande av anodoxidbildningsförfarandet. Minimala formningsspänningar på 20V till ett maximum av 100V användes i provframställningen och för att övervinna väntetiden vid bildning av de etsade proven användes en högre ström av 0,5A. Efter provberedningen användes elektrokemisk impedansspektroskopi som ett verktyg för att karakterisera de olika grupperna av prover och för att observera mikrostrukturerna i olika prover, de bröts och de observerades i tvärsnittet av SEM. Efter att analysen av de etsade proverna gjordes ett försök att jämföra resultaten av data från dessa prover till den för de två uppsättningarna av industriella prover. Det är konstaterat att de resulterande data inte var stabila nog att karakterisera eftersom stor spridning inträffade och varigenom simuleringen av CPE-kretsen för den valda kretsen i analysen inte var möjlig. Under analysen användes också ett slumpmässigt valt industriellt prov och de resulterande data användes för att förstå systemets respons till olika elektrolyter.
34
Dassié, Pierre-Igor. "Vers une approche intégrée de la synthèse et de la mise en forme d'oxydes métalliques par extrusion réactive." Thesis, Sorbonne université, 2018. http://www.theses.fr/2018SORUS131/document.
Full textAbstract:
Une nouvelle méthode « one pot » de synthèse et de mise en forme continue d’oxydes métalliques nanostructurés, résultat d’un couplage original entre la chimie sol-gel et le procédé d’extrusion réactive, a été développée. A notre connaissance, il n’existe pas de littérature concernant l’extrusion réactive massique d’oxydes métalliques, ce sujet se situe donc aux frontières des connaissances de tels systèmes chimiques. Nous nous sommes tout d’abord intéressés à la synthèse et la mise en forme d’aluminosilicates amorphes à porosité hiérarchique (micro/méso/macroporeux) à caractère zéolitique. Les extrudés obtenus présentent d’excellentes propriétés texturales (surface spécifique supérieure à 800 m2/g, volume poreux supérieur à 0,6 cm3/g). De plus, ils présentent une acidité exacerbée, comparée à un aluminosilicate standard. Leur activité, évaluée par isomérisation du méta-xylène et par déshydratation du méthanol, est supérieure à une référence contenant de la zéolite Y (pour une activité à iso-masse). Nous nous sommes également intéressés à la synthèse d’extrudés de boehmite. Nous avons tout d’abord cherché à adapter une réaction de co-précipitation de sels d’aluminium au procédé. Dans un deuxième temps, nous nous sommes tournés vers la synthèse en masse de boehmite par hydrolyse/condensation d'alcoxydes d'aluminium (sans solvant). Cette dernière réaction s'est révélée très intéressante tant au niveau de la validation du procédé d’extrusion réactive (intensification de procédé, intégration thermique) que du point de vue de la texture poreuse des produits formésA new one pot method for the synthesis and shaping of nanostructured metal oxides, based on the coupling of sol-gel chemistry and reactive extrusion process, was developed. To our knowledge, no literature is to be found about this topic so this work is situated at the frontier of such chemical systems’s knowledge. First, we worked on the synthesis and shaping of amorphous aluminosilicates with hierarchical porosity (micro/meso/macroporous) and zeolitic feature. Extrudates were obtained, those solids show fine textural properties (specific surface area above 800 m2/g, porous volume above above 0.6 cm3/g). Furthermore, they demonstrate increased acidity properties compared to standard amorphous aluminosilicates. Their catalytic activities were appraised by m-xylene isomerization and methanol dehydration and were found to be actually better than a catalyst with zeolite Y (for an activity calculed at iso-weight). Then we worked on the synthesis and shaping of boehmite (γ-AlOOH). First, we tryed to adapt an aluminium salts based co-precipitation reaction to our process. Afterward, we change the chemical reaction to aluminium alkoxides hydrolysis/condensation (without solvent). This later reaction was especially interesting, both in the validation of the reactive extrusion process (process intensification, thermal integration) as well as in the products textural properties
35
sheng, Peng jing, and 彭及聖. "Control porous pattern of anodic aluminum oxide." Thesis, 2005. http://ndltd.ncl.edu.tw/handle/87355058402729631449.
Full textAbstract:
碩士國立中興大學
機械工程學系
93
In this research, a series of anodic aluminum oxide fabrication experiments based on the aluminum foils laminate approach were carried out. During the experiments, we found that the pores of the AAO grew only on the upper foil, bi-directionally from both the top and the bottom surfaces. Experimental results further indicate that the upward porous pattern of the upper foil is determined by the surface structure of the bottom surface of the upper foil. The porous pattern of AAO can be controlled by a pre-made pattern on the bottom surface. In addition, since the lower aluminum sheet attached to the bottom of the being anodized aluminum sheet acts as a barrier layer during anodization, no barrier removing process is required in this novel laminate approach. The developed work in this study can be further applied to the fabrication of nanofunction devices.
36
Wang, Yadong, Melissa Sander, Chen Peng, Soo-Jin Chua, and Clifton G. Jr Fonstad. "GaN Based Nanomaterials Fabrication with Anodic Aluminium Oxide by MOCVD." 2003. http://hdl.handle.net/1721.1/3664.
Full textAbstract:
A highly self-ordered hexagonal array of cylindrical pores has been fabricated by anodizing a thin film of Al on substrate and subsequent growth of GaN and InGaN in these nanoholes has been performed. This AAO template-based synthesis method provides a low cost process to fabricate GaN-based nanomaterials fabrication.Singapore-MIT Alliance (SMA)
37
Chien-HsiangFan and 范建翔. "Tunable Photoconductivity of Porous Anodic Aluminum Oxide with Silver Nanoparticles." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/47755424468065005276.
Full textAbstract:
碩士國立成功大學
光電科學與工程研究所
99
The dielectric porous anodic aluminum oxide films (AAO) with embedded two-dimensional (2D) silver nanoparticles array have been fabricated by electrochemical deposition. There are have the function of photo-induced conductivity and can be apply to the optical photon switching. When an appropriate laser light source is emitted to the 2D Ag anoparticles array of AAO films, the localized surface plasmon resonance (LSPR) is excited. The dielectric AAO films with embedded 2D Ag nanoparticles thus exhibit the conductivity, is called the photoconductivity, which has the high dependence of laser wavelength and laser power. In this thesis, we follow the experiment which arried out by Ben-Chao Lau. The experiment proves the photo-induced electrical conduction can be achieved by pours anodic aluminum oxide with embedded silver nanowires (Ag/AAO). Here, we will change the pore diameter and inter-pore spacing to investigate the influence of photocurrent and photoconductivity of Ag/AAO substrate. By changing the pore size and inter-pore distance, the absorption spectrum of these substrates can expect the phenomenon for the plasmon resonance peak appear shifting and broadening. The diameter of pores can changed with different etching time, and the distance of inter-pore also can be controlled by applying the different anodic voltage. Thus, we can fabricate many varied Ag/AAO films and measuring photocurrent at different condition. Therefore, we expecting these varied Ag/AAO films have ability for developing a high tolerance and tunable wavelength of optical photon switching base on the Ag/AAO film.
38
Liu, I.-Yun, and 劉伊芸. "Fabrication of FePt Network Nanostructures with porous anodic aluminum oxide." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/00713011421072520759.
Full text
39
Lee, Hong-Chang, and 李鴻昌. "Investigation of MEMS Filter For Porous Anodic Aluminum Oxide Technology." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/92107318176602761221.
Full textAbstract:
碩士和春技術學院
電機工程研究所
95
Nano technology is that have been often brought the theme studied extensively in recent years. Because use porous anodic alumina oxide technology process to got the MEMS filter have excellence of chipper. This thesis makes out the MEMS filter of porous anodic alumina oxide technology. First porous anodic alumina oxide technology detailed introduction and relevant theories. In this process, we use the silicon substrate and use steam plating to use aluminium membrane steam on silicon substrate, take up the porous anodic alumina oxide technology process to grow Al2O3 and we can the ground side on back to plating process. Second we use Al2O3 surface of sink mask on the surface of filter figure to plating process, and remove the mask if the plating finish, than the filter figure show in the Al2O3 surface,than measure data in fanil. Use porous anodic alumina oxide technology process to got the MEMS filter have excellence of chipper, probe into the component characteristic.
40
Tseng, Chun-Wei, and 曾俊瑋. "Preparation, Structure and Anti-Reflective Properties of Nano-Porous Anodic Aluminium Oxide for Solar Cell Application." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/wxk58a.
Full textAbstract:
碩士國立東華大學
光電工程學系
100
While it has been known that the electrochemical behavior of the ions migration (Al3+ and O2−) for pore AAO formation can conventionally be distinguished by controlling the voltage-time curve, the effects of geometric scale dependent reflectance on the optical properties of AAO films have not been emphasized until recent years. In addition, the nano-porous AAO with pore-density/size dependent anti-reflectance (AR) at different incident angles has rarely been addressed. In particular, the alternative approach on simplifying the AR film evaporation with lower production cost is also the important key for obtaining cost-effective solar cells, whereas more than 34% of the incident light is actually reflected back from the surface of solar cells. This study demonstrates nanoporous AAO thin films with ultra-low reflectivity and hydrophobicity on glass substrate produced by two-step anodization at room temperature. The effects of various electrochemical conditions on their geometric scale and the reflectance at different incident angles are characterized. In particular, the surface energy related hydrophobicity, as well as the geometric scale of the electrochemical synthesized nanoporous AAO film, is investigated and elucidated. By electro-polishing the aluminum coating, a minimum roughened surface with an Rrms of 3.91 nm is obtained. After adjusting the applied potential, an optimum regular structure of anodic aluminum oxide (AAO) is obtained, corresponding to the pore diameter and density of 23 nm and 8.67×10^10 cm^-2. In particular, nanoporous AAO with an air/solid ratio of 58% exhibits a maximum water contact angle of 73.4° corresponding to surface energy of 40.1×10^-5 N．cm^-1. Furthermore, the TM-mode reflection analysis shows a diminishing Brewster angle shifted from 60°-54° with an increasing air/solid ratio from 37%-58% at 532 nm. The greatly reduced small-angle reflectance and surface energy reveals a nonlinear trend with an enlarging pore size and air/solid ratio, leading to a minimum surface reflectance and maximum water contact angle at the nanoporous AAO prepared with 60V. Furthermore, an optimum power efficiency of 1.13% is obtained in the nanoporous AAO anti-reflection coating glass covered semi-manufactured solar cell.
41
Wen-ChinChen and 陳玟瑾. "Fluorescence Responses of Porous Anodic Aluminum Oxide Films with Silver Nanoparticles." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/67663804924984889656.
Full textAbstract:
碩士國立成功大學
光電科學與工程學系
101
In this thesis, we produce the anodic aluminum oxide (AAO) film which has highly order nanopores inserted by Ag nanoparticels with high filling ratio using the electrochemical deposition with a stable DC voltage. The absorption spectra of Ag/AAO films are measured, and the visible absorption peak, 405 nm, is observed. The major reason of absorption peak is local surface plasmon induced by the Ag nanoparticles on the surface of Ag/AAO film. The surface plasmons (SPs) are also excited by Ag nanoparticles by total internal refection fluorescence (TIRF) technique. The fluorescence signals can be enhanced by the localized electric field. In our experimental processes, the sizes and pitches of AAO samples can be controlled under a stable experimental condition. Therefore, their optical properties are suitable to investigate the fluorescence signals with different fluorescence reagents. The fluorescence signals caused by the evanescent wave are measured by the traditional total internal reflection fluorescence microscope (TIRFM) when the angle of incident light is more than the critical angle. The evanescent range is about several hundred nanometers which reach nano-scale resolution, and the fluorescence images have low background noise. In our samples applied on lived cells, we also need to enhance the fluorescence images. When localized surface plasmon resonance (LSPR) excited by evanescent wave, the detection limit decreases and the fluorescence signals are enhanced by the Ag/AAO films using the total internal reflection fluorescence microscope (TIRFM) combined.
42
Chuang, Yuan-Cheng, and 鍾源昇. "Ordered porous anodic aluminum oxide film fabricated by nano-tip arrays." Thesis, 2005. http://ndltd.ncl.edu.tw/handle/04521226055153648501.
Full textAbstract:
碩士國立成功大學
微機電系統工程研究所
93
Nanotechnology represents one of the most novel frontiers in today’s science and engineering research. With increasing interest in the fabrication of nanometer-sized structures applied in optical, electronic, magnetic, and optoelectronic devices. Anodic porous alumina, which has been studied in detail in recent years . Thus AAO has been commonly used to fabricate nanometer-sized structures via the template mediated process because of its relatively low cost and ease of fabrication compared with conventional lithography processed materials. In fundamental studies of anodic alumina oxide, we use high pure aluminum and then put this treated aluminum sample into a particular electrolyte to grow desired oxide under suitable conditions. After that , we can get patterns with uniform pore size . By adjusting process parameter , we can control our AAO patterns such as the pore size and the density of pores . But we have different methods to control pore Arrays. This experiment is mainly combine silicon mold by anisotropic etching of silicon and imprint onto aluminum foil .we will discuss the anodic process after imprinting that whether could control array of nano-pore.
43
Chang, Zeng-Rong, and 昌增榮. "The characteristics of porous anodic oxide structure formed on aluminum thin film." Thesis, 2005. http://ndltd.ncl.edu.tw/handle/50969094239800859579.
Full textAbstract:
碩士國立成功大學
機械工程學系碩博士班
93
The research mainly explores the porous oxide from anodic aluminum thin film: to analyze the surface morphology and section structure of the porous oxidized membrane through SEM, and to match up the voltage- current-time relationship during anodizing process to discuss the formation of the pores and the influence of voltage and electrolyte temperature on the porous structure. Eventually, we compare the anodic interpore distance with the size of poly-Si from Excimer Laser re-crystallization to find out the most suitable parameter. It is for applying the porous oxidized aluminum thin film to the new type poly-Si solar cell. The depth of the alumina barrier is about 50nm when using 60V and 80V of anodizing voltage. When the voltage is above 80V, the increase of voltage will result in the thicker barrier. The barrier thickness adds up to 200nm while voltage rises to 140V. The wall thickness of the pore structure is about 60~70nm under 100V, and it will increase linearly to 206nm while the voltage rises to 140V. The distances between pores are 134nm and 329nm respectively when voltages are 60V and 140V. The average distance will become farther with the mounting voltage. After 120V-40V reducing voltage process, the depth of barrier is 73nm, the wall thickness is about 145nm, the interpore distance is about 255nm. The interpore distance after anodizing with 120V and the size of crystals under laser parameter of 450 mJ/cm2 are similar. Comparing the interpore distance after 120V-40V reducing voltage process and 120V long-term anodizing, we can discover that they are alike. So we can utilize the former process to adjust the pore structure for the application of solar cell.
44
Chung-HaoTsai and 蔡仲豪. "A study on fabrication and characteristic of porous anodic aluminum oxide from 5052 aluminum alloy." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/18038351346069748351.
Full textAbstract:
碩士國立成功大學
機械工程學系
104
Anodic aluminum oxide (AAO) template has been widely applied to different fields such as photonics, semiconductor, biomedical, chemical engineering and so on. Conventional AAO template was formed using direct-current anodization (DCA) from high-purity (99.99% or more) aluminum (Al) foil at low temperature (0~10 °C). In this article, we have successfully demonstrated the greatly enhanced growth behavior of 5052 Al-Mg alloy (95.5% Al) using hybrid pulse anodization (HPA) with pulsing normal-positive and small-negative potential to synthesize nanoporous AAO at room temperature (RT, 25 °C). The growth rate at RT is higher than that at low temperature. The Mg impurity in the 5052 Al alloy plays an important role during anodization; it influences the AAO property and composition. The Mg contents in 5052 Al alloy could contribute to the growth of AAO. Also, the AAO fabricated by 5052 Al alloy is found quite different from pure Al in the average pore size. In addition, we investigated the photoluminescence (PL) difference between 5052 Al alloy and high purity Al, to prove that the composition difference also caused in the optical characteristic change. In the end, we proposed a fast, easy and low cost SERS substrate by AAO from 5052 Al alloy and platinum to investigate the anodization parameters effect on enhancement of Raman intensity.
45
Chang, Chung-Chuan, and 張中銓. "Effect of Nanometer Oxide on the Optical Properties of Sapphire Substrate with Porous Anodic Aluminum Oxide Film." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/r9m777.
Full textAbstract:
碩士國立臺灣科技大學
機械工程系
106
In this study, anodized aluminum oxide film (AAO) with nanopore arrays structure was fabricated on single-crystal sapphire substrate by magnetron sputtering and anodic oxidation. Tin and tin oxide were deposited on the surface to change the transmission and reflection of visible light , Making the colorless and transparent sapphire substrate color change, the extension of the application. Through the adhesion cross-cut test and the nanoindenter measurement, we found that the aluminum film has the best adhesion at a working pressure of 3 mTorr. Through the field emission scanning electron microscope measurement, the AAO hole size formed by oxalic acid is about 50 nm, which is not obvious for the diffraction phenomenon of visible light. The tin atoms are almost only deposited on the surface when tin is sputtered. The pore diameter of AAO formed by phosphoric acid is about 200 nm, which makes the incident light destructively interfere with the wavelength of 400 nm. The size of the holes is enough to make the tin atoms deposited inside the holes. After the visible spectrum measured via known, sputtering under five minutes, the amount of tin atoms sufficient to modify the results of the visible spectrum and does not completely seal the holes, and forming a plurality of peaks generated stannous oxide to the transmission and reflection spectra Wave pattern changes, the appearance also had a significant color change.
46
LEE, HUNG-CHING, and 李竑慶. "Effect of Nanometer Oxide on the Optical Properties of Glass Substrate with Porous Anodic Aluminum Oxide Film." Thesis, 2019. http://ndltd.ncl.edu.tw/handle/rk9d5a.
Full textAbstract:
碩士國立臺灣科技大學
機械工程系
107
In this study, a microstructure was set on the glass to change the transmittance of light. Zinc were deposited on the glass substrate by magnetic reactive sputtering with anodic aluminum oxide (AAO) template, after that the ZnO nanoparticles were prepared by thermal oxidation. The procedure of the experiment was mainly used magnetron RF Sputter to deposit Al film on the glass with transmittance and also processed the Al into nano porous structure by using electrochemical process Moreover, the analysis of the optical penetration is attribute to the nano porous structure and transparency of AAO.During the manufacturing process, the electrolyte with anodic treatment and the voltage was changed in order to analyze the variation of light by using Ultraviolet/Visible spectroscopy. In addition, due to the benefit of nano porous structure, ZnO film could deposit on the surface much more homogeneously, improving the transparency Therefore, the study observed that ZnO film had the character of selective absorption in ultraviolet band. For example, it was proved that the ZnO film was opaque in the range of 386.3 nm of the light. Lastly, the each step of measurement test including used the Field Emission Scanning Electron Microscope (FE-SEM), which could not only show the shape, but also measure the microstructure, as well as make sure the ingredient of ZnO material by X-ray Diffraction (XRD).
47
Chou, Liang-Yu, and 周亮余. "Fabrication of Palladium/ Anodic Aluminum Oxide/ Porous Ceramic Tri-Layered Structure for H2 Permeation." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/86756493627274205013.
Full textAbstract:
碩士國立交通大學
材料科學與工程學系
100
This work is concerned with the fabrication of a composite membrane structure (Pd/alumina oxide/porous ceramic) that enables the separation of hydrogen from a mixture of hydrogen and carbon dioxide at elevated temperature. The porous ceramic containing a variety of pores is adopted as the substrate where thin layers of alumina oxide and Pd are deposited sequentially. Large pores in the ceramic substrate facilitate hydrogen transports but they require thick layers of Pd to cover those exposing pores which wastes Pd unnecessarily. Hence, a thin layer of aluminum is thermally deposited onto the porous ceramic substrate followed by an anodization treatment to form hexagonal-structured porous alumina oxide. This effectively reduces the diameter of the open pores that allows a thin Pd deposit to function. For permeability test, a gas chromatograph is employed to determine the amount for leakage and hydrogen permeation. At room temperature, the leakage is estimated at 0.455 ml‧ cm2‧min-1. In contrast, the hydrogen flux after deducting the amount of leakage at 600 °C is around 0.612 ml‧cm2‧min-1. In addition, after 60 min of operation in 50％H2-50％CO2 atmosphere, the hydrogen flux is decreased to 0.286 ml‧cm2‧min-1. This notable reduction in hydrogen permeation is caused by the competing adsorption of H2 and CO2 that limits the effective Pd surface for hydrogen permeation.
48
Ben-ChaoLau and 羅本超. "Photo-induced Electrical Conduction of Porous Anodic Aluminum Oxide Films Embedded with Silver Nanoparticles." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/77902430449777334836.
Full textAbstract:
碩士國立成功大學
微電子工程研究所碩博士班
98
Dielectric films embedded with two-dimensional (2D) arrays of silver nanoparticles have been fabricated by electrodeposition of Ag into nanopores of anodic aluminum oxide (AAO) films. In this case, the filling ratio of Ag nanoparticles into nanopores of AAO films is a major concern. Alternating current voltage source and Direct current voltage source are used as electrodepositing sources to determine the best filling ratio. Results show that alternating current voltage source has got better filling ratio than direct current voltage source. The absorption spectrum of Ag nanoparticles embedded in the anodic aluminum oxide film (Ag/AAO) shows that the characteristic plasmon resonance peak is located at 405 nm which is considered to be caused by localized surface plasmon resonance (LSPR) of Ag nanoparticles. Two metal contacts are fabricated for the conductivity measurements of the Ag/AAO film. The optical system consisting of 633-, 532- and 405-nm lasers is set for the photo-induced conductivity measurement. Conductivity measurements under 405-nm laser illumination have got the highest conductivity compared to the conductivity under other laser illuminations and the dark condition. The ratio of the induced conductivity for 633-, 532- and 405-nm laser illuminations is directly proportional to the ratio of the structural absorption at these three wavelengths, which confirms that the localized plasmon resonance of Ag nanoparticles are closely related to the photo-induced conductivity on the Ag/AAO substrate.
49
Chu, Chien-Wei, and 朱建威. "Fabrication of Porous Anodic Aluminum Oxide Templates and Property Analysis of Confined Functional Polymer Nanomaterials." Thesis, 2017. http://ndltd.ncl.edu.tw/handle/y28u6g.
Full textAbstract:
博士國立交通大學
應用化學系碩博士班
105
Polymer nanomaterials recently have attracted great interest because of their unique properties compare to the bulk materials. To have a deeper understanding of the properties of confined functional polymer nanomaterials, a simple route to fabricate polymer nanostructures is desired. In this work, we build up a well-controlled system in our laboratory to fabricate AAO templates using the second anodization method (Chapter 3). Subsequently, cylindrical anodic aluminum oxide (c-AAO) templates can be synthesized using similar anodizing process on the Al wires and the polymer nanorod arrays on the curved surfaces can be obtained by infiltrating polymers into the nanopores of the c-AAO templates (Chapter 4). Furthermore, light-emitting polymer nanotubes are also fabricated by infiltrating the light-emitting polymer into the nanopores of the AAO templates. The optical properties and polymer chain packings of confined polymer nanotubes are also characterized (Chapter 5). Finally, stimuli-responsive polymer brushes are grafted from the surfaces of the AAO templates by surface-initiated atom transfer radical polymerization (SI-ATRP). The confinement effect on polymer chain growth in the nanopores of AAO membranes is investigated (Chapter 6).
50
Lee, Kuan-Wei, and 李冠緯. "The Application of Porous Anodic Aluminum Oxide in Field-Flow Fractionation for Nanoparticles Size Discrimination." Thesis, 2019. http://ndltd.ncl.edu.tw/handle/tcy2h9.
Full textAbstract:
碩士國立臺灣師範大學
化學系
107
In the research, we developed a brand new Field-Flow Fractionation (FFF) device which based on porous anodic aluminum oxide (AAO) plate. After we issued a hypothesis of trap model, a series of experiments was designed to verify and testify the hypothesis. The line of the research separated into two different operations, the Electric Field-Flow Fractionation (ElFFF) and Magnetic Field-Flow Fractionation (MFFF). First, in the ElFFF experiment, a valuable result was found that a particle with a diameter (10 nm) smaller than the pores of AAO was prone to electrolysis under the electric field. While a particle had a diameter (40 nm) larger than AAO pores, such the tendency was not been found. However, the drawback of ElFFF, bubble formation, profoundly retarded us to verify the trap model in ElFFF. Second, in the MFFF experiment, the trap phenomenon was detected both in AAO plate and unprocessed Al plate, but the number of trapped particles in AAO plate was much more than Al plate. Furthermore, through the analysis of these trapped and non-trapped particles size, an exciting result indicated that the size of trapped particles was generally smaller than non-trapped particles. Although this was merely quite preliminary research, the size choosing ability of porous AAO first revealed in FFF instrument.