Academic literature on the topic 'Hard anodization'

PurposeThe novel structures and properties of nanostructure and nanomaterials give people perfect artistic expression of feeling and sense, then the nanoart discipline is developed and is closely related on the nanotechniques. The many achieved novel nanostructures with strong anti-corrosion prepared by the anodization have been reviewed. The paper would raise public awareness of nanotechnology, nanomaterial and their impact on our lives.Design/methodology/approachAnodization is a very effective and simple technique to form various nanostructures of metal oxide. It includes hard anodization, mild anodization and pulse anodization. Many measures have been introduced anodization process to improve the quality of formed nanostructure and enhance its properties, such as anti-corrosion.FindingsThe formation mechanism of anodic aluminum oxide (AAO) by using the mild, hard and pulse anodization has been discussed. The pretexture process and many other measures have been taken in mild and hard anodization to improve the regularity of pore array and greatly accelerate the formation rate of AAO. The pulse anodization has been used to prepare the multilayer Y-branched AAO film, which exhibits steady rich and vivid structure colors and gives a very good artistic expression. Furthermore, many other metal oxide nanostructures such as TiO2and CuO have also been fabricated using the anodization techniques.Originality/valueVarious nanostructures of metal oxide prepared by anodization have been reviewed and are itself a perfect artwork in mesoscale. Also, many nanostructures have exhibited steady, rich and vivid structure colors and give people a very good artistic expression.

In this paper, we used two mass-produced industrial technologies, namely, thermal spraying and anodization methods, to enhance the surface characteristics of AISI 1045 medium carbon steel for use in special environments or products. The anodic film can effectively improve the surface properties of carbon steel. A sequence of treatments of the carbon steel substrate surface that consist of sandblasting, spraying the aluminum film, annealing, hot rolling, cleaning, grinding, and polishing can increase the quality of the anodized film. This paper proposes an anodization process for the surface of carbon steel to increase the corrosion resistance, hardness, color diversification, and electrical resistance. The resulting surface improves the hardness (from 170 HV to 524 HV), surface roughness (from 1.26 to 0.15 μm), coloring (from metal color to various colors), and corrosion resistance (from rusty to corrosion resistant). The electrochemical corrosion studies showed that the AISI 1045 steel surface with a hard anodized film had a lower corrosion current density of 10−5.9 A/cm2 and a higher impedance of 9000 ohm than those of naked AISI 1045 steel (10−4.2 A/cm2 and 150 ohm) in HCl gas.

This research presents how to use high current density (2.85A/dm2) to do 6061 aluminum alloy hard anodization. There are five steps during the process including mechanical polishing, anodization, acid spitting, sealing and surface cleaning. By using electrochemical molds which we designed and controlling the electrolyte temperature at-2°C, then we could obtain ordering anodization film with 20nm pore size and 33.3μm thickness. However, there are some situations should be overcome such as raising the success rate of sealing and reducing the defects on the AAO surface by means of adjusting the parameters such as the current density, final voltage, electrolyte temperature, etc.

Anodized aluminum (Al) and Al alloys have a wide range of applications. However, certain anodized finishings have relatively low hardness, dull appearance and/or poor corrosion resistance, which limited their applications. In this research, Al was first electropolished in a phosphoric acid-based solution, then anodized in a sulfuric acid-based solution under controlled processing parameters. The anodized specimen was then sealed by two-step sealing method. A systematic study including microstructure, surface morphology, hardness and corrosion resistance of these anodized films has been conducted. Results show that the hardness of this new anodized film was increased by a factor of 10 compared with the pure Al metal. Salt spray corrosion testing also demonstrated the greatly improved corrosion resistance. Unlike the traditional hard anodized Al which presents a dull-colored surface, this newly developed anodized Al alloy possesses a very bright and shiny surface with good hardness and corrosion resistance.

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No. of bitstreams: 1 GARCIA_Uanderson_2017.pdf: 25453924 bytes, checksum: 4c34f46362e91f9eb2f88106f805d7f3 (MD5) Previous issue date: 2017-03-14<br>Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)<br>Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)<br>This work covers the investigation and synthesis of nanometric structures of Porous Anodic Alumina PAA, produced from low purity substrates, in aim to obtain selfsustained membranes. The Hard Anodization (HA) and Mild Anodization (MA) processes were used under special conditions through those found in literature. The analyses of results were based in comparing the AAP produced under the same conditions except the applied potential that was different depending on the MA or HA. HA process had its time halved in order to investigate the oxide growth rate and to calibrate the conditions of anodized membrane synthesis over the glass samples. This work also covers the construction of a resistive thermal evaporation PVD system capable of evaporating metals with melting points below 800°C. Through the deposition of successive layers it was possible to obtain metallic films of aluminum with thicknesses above 10 µm, enabling conditions of synthesis of porous anodic alumina on substrates produced by thermal resistive evaporation. The result of membrane synthesis on low purity aluminum substrates was complement to the synthesis of membranes obtained in aluminum evaporated in glass substrates, since the thickness of each deposited film is low if compared to the thickness of the AAP layer. Therefore, it was necessary to make several Al depositions on the same samples, to obtain an aluminum film that was able to support an oxide layer of anodic alumina and with the same characteristics of those obtained by the process of MA. All anodized samples were characterized by scanning electron microscopy, including samples made from metalized aluminum. The micrography obtained from the low purity aluminum membranes were treated by ImageJ software allowing the morphological analysis. AAP membranes obtained from technical Al substrate depicted the formation of branched pore channels, a result of instabilities in applied electric field during Anodization and presence of different alloying elements in the Al substrate. The metalized aluminum film had a larger thickness in the samples positioned in the middle of the sample holder possibly due to different temperature gradients of filament depending on the position of Al pellets.<br>Este trabalho aborda a síntese e investigação de estruturas nanométricas de Alumina Anódica Porosa AAP produzidas a partir de substratos de baixa pureza, com a finalidade da obtenção de membranas auto-suportadas. Foram utilizados os processos de Hard Anodization (HA) e Mild Anodization (MA). Para efeito comparativo entre os processos foram mantidas todas as condições variando apenas o potencial aplicado. Posteriormente para HA o tempo experimental foi reduzido pela metade a fim de investigar a velocidade no crescimento do óxido e condições de anodização de membranas sobre as amostras de vidro. Este trabalho também abrange a construção de um sistema Phisical Vapor Deposition (PVD) por evaporação térmica resistiva, capaz de evaporar metais com pontos de fusão abaixo de 800°C. Através da deposição de sucessivas camadas foi possível a obtenção de filmes metálicos de Alumínio com espessuras acima de 10 µm, possibilitando condições de síntese de alumina anódica porosa sobre substratos produzidos por evaporação térmica resistiva. O resultado da síntese de membranas em substratos de Al de baixa pureza foi complementar à síntese das membranas obtidas em alumínio evaporado em substratos de vidro, pois a espessura de cada filme depositado é baixa se comparados a espessura da camada de AAP. Portanto, houve a necessidade de várias deposições sobre as mesmas amostras, para se obter o filme de alumínio que fosse capaz de suportar uma camada de alumina anódica porosa resistente e que se aproximasse das características das obtidas pelo processo de MA. Todas as amostras anodizadas foram caracterizadas por microscopia eletrônica de varredura, inclusive as amostras produzidas a partir do alumínio metalizado. As micrografias obtidas a partir das membranas de alumínio de baixa pureza foram tratadas pelo software ImageJ, possibilitando a análise morfológica das mesmas. As membranas de AAP de baixa pureza possuem poros com ramificações transversais, são provocadas pelos desvios do campo elétrico aplicado, além da possibilidade de formação de outros tipos de óxidos. O filme de alumínio metalizado teve maior espessura nas amostras posicionadas na parte central do porta amostra, isso pode estar relacionado com o aquecimento do filamento que ocorre da região central para as extremidades.<br>2010/10813-0

碩士<br>國立聯合大學<br>能源工程學系碩士班<br>107<br>The mild and hard anodic film of 6161 aluminum alloy has been studies by anodization in this thesis. In order to make a high quality anodic film on 6061 aluminum alloy the experiment parameters such as, anodic voltage, current density, temperature, and anodization time were under controlled. And, the characterizations of anodic film such as film thickness, film hardness and surface roughness were tested. The management of electrolyte temperature is also important because the exothermic reaction is usually accompanying with anodization. A high quality anodic film is always affected by the pretreatment. In our experiment, we also used chemical polishing and electro polishing as the pretreatment. The chemical polishing and electro polishing both can remove the surface scratches and defects which on the 6061 aluminum surface. In our study, an optimal parameter of 80 μm film thickness of mild anodization as: 22 V of anodic voltage, 60 min of anodization time, 25oC of electrolyte temperature. And, an optimal parameter of 57 μm film thickness of hard anodization as: 90 V of anodic voltage, 2 to 4 A/dm2 of current density, 47 min of anodization time, and 4oC of electrolyte temperature. Key words: 6061 aluminum alloy, hard anode treatment, mild anode treatment, surface treatment

碩士<br>國立交通大學<br>材料科學與工程學系奈米科技碩博士班<br>101<br>Nanoporous anodic aluminum oxide (AAO), a typically self-ordered nanopore material featuring of ordered high-aspect-ratio channels, has been widely used for the development of various functional nanostructures such as nano-magnetic memories, nanosensors, nanophotonic devices, nano-energe devices and nanoelectronic devices. The conventional fabrication of self-ordered Al2O3 pore arrays so-called mild-anodization (MA) requires several days of processing time and the self-ordering phenomenon occurs only in narrow process windows. Recently, a new attempt for AAO process, hard-anodization (HA), has successfully demonstrated. The HA process offers substantial advantages over conventional anodization processes in terms of processing time, allowing 3000% faster oxide growth with improved long-range ordering of the nanopores. However, compared with H3PO4 HA by us, AAO films obtained in suffer from poor mechanical properties because of structural cracks and defects, while uniformly sized parallel channels and irregular top surface with ‘‘pore in pore’’ structures cannot be exclusive in those using C2H2O4 HA process. In this work, we report an innovative H3PO4-based HA process for long-range ordered and high growth-rate alumina membranes. The various anodization parameters including applied voltage, electrolyte concentration, and temperature which have significant impact on the morphology of AAO will be discussed deeply. The self-ordering behavior in nanoporous AAO using H3PO4 HA process unlike conventional methods is investigated at applied voltage from 160 to 270 V without pre-anodization step. The applied voltage via the interpore distance is linearly relationship at anodization voltages from 160 to 210 V and presents an interpore distance from 325 to 390 nm. Unexpectedly, the linearly relationship will vanish and saturate from 220 to 270 V, which may result from the jour-heat accumulation supported by the chronoamperic response. By using advantages of H3PO4 HA method to fabricate taper AAO templates, we can obtain highly ordered and high-aspect-ratio taper AAO templates and then the tapered acrylic (PMMA) nanostructure can be obtained by spin coating or hot embossing. Moreover, we find that the PMMA surface with taper nanostructure coating fluoalkysliane display superhydrophobic phenomenon which can be served as a self-cleaning surface. The innovative AAO template fabrication is simple and cost-effective, and is of great value for applications in diverse areas of nanotechnology.

The sensor is a device that converts a form of energy concerning which the information is sought, called the measurand, to a form (electrical) in which it can be usefully processed or interpreted. Sensors rely on physical or chemical phenomena and materials where those phenomena appear to be useful. Those phenomena may concern the material itself or its geometry. Hence, the major innovations in sensors come from new materials, new fabrication techniques or both. Normally, thin film sensors are realized by depositing a sensing film on a suitable substrate. There could be many combination of metals and insulating materials being deposited depending upon the application or sensing requirements. In general, sensors for various applications are fabricated using a variety of liquid phase technologies (also called as wet methods) and gas phase technologies (also called as dry methods) of deposition. Hence sensor fabrication technology requires various combination of processing technologies and newer materials. In the present work, an attempt is made to design and fabricate a thin film based pressure sensor using a combination of wet and dry deposition techniques. The diaphragm, used for sensing the pressure is coated with a hard anodic coating (Al2O3) using a wet technology, viz. pulse hard anodizing technique, for electrical insulation requirement. The piezo-resistive strain sensing films were deposited onto this coating by dry method, namely, DC Magnetron sputtering technique.. Chapter 01 gives a brief overview of sensors, their classification, principles of sensing,characteristics, materials used in the fabrication of sensors like conductors and insulators, the components of a sensor. Chapter 02 gives brief information about various techniques of depositions viz., liquid phase technologies (wet methods) and vapour phase technologies (dry methods) used to fabricate the sensors. Also, information regarding the coating property evaluation and coating characterization techniques is included. The chapter 03 presents a detailed account of work carried out to obtain an electrically insulating layer by the development of pulse hard anodizing process for aluminum alloy diaphragm, necessary process optimization and testing. The details related to the development, fabrication and testing of thin film based pressure sensors using aluminum alloy diaphragm with hard anodic coating are presented in Chapter 04. The thin film strain gauges were deposited using DC magnetron sputtering technique. The information about mask design, deposition process parameters, calibration etc is also included. Chapter 05 provides summary of the work carried out and conclusions. The scope of carrying out further work is also outlined.

This study aims to develop a long-acting and implantable drug release device that can well control the release rate and concentration of the loaded drug. The proposed long-acting and implantable drug release device consists of a tubular nanoporous anodic aluminum oxide (AAO) and the microporous chitosan/collagen composite encapsulated inside it. The nanopore size of the AAO tube can be arranged by the anodization parameters to adjust the release rate and concentration, while the microporous chitosan/collagen composite can provide the device with a long-acting release property. Fabrication results indicated that the AAO tube has a uniform pore arrangement with pore size around 50 nm. And the synthesized microporous chitosan/collagen composites composites containing 90% of chitosan had the highest moisture content; therefore were used as the drug carriers. Release experiments demonstrate that the proposed long-acting drug release device had released only less than 60% of the loading drug at the 16th release day.

A facile electrochemical anodization method was used for producing hierarchically textured surfaces based on TiO2 nanotubes in two different configurations. It was found that perfluoro-functionalized TiO2 nanotubes exhibit high static contact angles for a variety of liquids such as apolar, polar aprotic and polar protic solvents. Wenzel and Cassie-Baxter theories were applied for theoretical contact angle calculations for the present study. By using Cassie theories, it is shown that a drop of polar liquid was in a fakir or Cassie-Baxter (CB) state on perfluoro-functionalized nanotube surfaces. The fakir state prevents spreading of the liquid on the surface. On the other hand, the wetting of non-polar liquids such as hexane is characterized by either Wenzel states or transition states characterized by partial imbibition that lie in between the CB and Wenzel states.