No description available.

The intention with this thesis was to evaluate how much pickling that have been achieved on aluminium details in the pickling bath before the anodization in an anodization process. As there were no earlier studies to use around pickling before anodization, statistical experimental design was chosen as planning tool. Statistical experimental design was used to plan the experiments in an organized way and to evaluate how the pickling process works together with the main effects and the interaction effects. Detailed scientific studies were performed on how aluminium is prepared and how the anodization process works. The studies were performed in reference books. Three different methods were designed. The first method, method 1, was based on a fractional factorial design with four design variables, temperature, sodium hydroxide and aluminium concentrations and the time the details was submerged into the pickling bath. The aluminium details was made from a square profile pipe. There was nine experiments performed in method 1. The measurements on the pickling was performed in two ways, first with a dial indicator where the pickling was compared with a reference surface before and after, and another method also performed with a dial indicator, where the measurements was performed over the edge between the pickled surface and the reference surface. A statistical control calculation was done on the surface smoothness of the square profile pipes. The control showed that the standard deviation was 11 µm. Method 2 was based on a complete factorial design where the design variables was temperature and the time the details was submerged into the pickling bath. All aluminium details were homogenous. There were seven experiments performed in method 2. The measurements on the pickling was performed in two ways, first with a dial indicator where the pickling was compared with a reference surface before and after, and another method also performed with a dial indicator, where the measurements was performed over the edge between the pickled surface and the reference surface. A statistical control calculation was done on the surface smoothness of the homogenous details. The control showed that the standard deviation was 14 µm. Method 3 was designed in a different way than method 1 and 2. In method 3 one experiment was performed and the design variable which was changed was the time when the details was submerged into the pickling bath. The aluminium details had the form of homogenous cubes. The measurements on the pickling was performed by measuring the weight of the details on an analytical scale before and after the pickling, and then calculate the pickling in µm in two different ways. The first way was to use the atomic radius of aluminium and the second way was to use the size of the unit cell of aluminium. The two first methods gave very different results than the third method. The result for method 1 showed very random values with great dispersion which resulted in a non-detectable pickling. The result for method 2 was very similar to the result from method 1, very random values with great dispersion and no pickling was detectable with any confidence. The result from method 3 gave a theoretical calculated result for the pickling, when the aluminium details was submerged in the pickling bath for 1 minute, and based on the atomic radius of aluminium, of 1,52 µm and with the same conditions but using the unit cell of aluminium showed a pickling of 1,62 µm. When the aluminium details were submerged in the pickling bath for 3 minutes, the theoretical calculation with the atomic radius of aluminium gave that the pickling was 4,51 µm and with the same conditions but using the unit cell of aluminium showed a pickling of 4,79 µm.

No description available.

A proposta deste trabalho é a produção de matrizes de nanotubos de dióxido de titânio seguindo os métodos de anodização eletroquímica de titânio estabelecidos da literatura. O objetivo central é a compreensão aprofundada das etapas do processo de crescimento dos nanotubos de TiO2, para posterior otimização de sua síntese visando as diferentes aplicações. Com este propósito foram realizados sistematicamente os seguintes estudos: das diferentes fases de crescimento dos nanotubos de TiO2, do efeito dos diferentes parâmetros de anodização na morfologia dos nanotubos e da reprodutibilidade dos processos. Visando as diferentes aplicações foram estudados métodos para obtenção de membranas autossustentadas e remoção de nanoresíduos. O método de camada sacrificial de fotoresiste positivo apresentou melhor resultado para remoção de nanoresíduos do topo dos nanotubos de TiO2 do que as demais técnicas. Por último, os arranjos obtidos com esta método foram aplicados na fabricação dos sensores de pH. / This work proposes the production of titania nanotubes arrays following the electrochemical anodization methods of a titanium sheet established in the literature. The main goal is a deep comprehension of the different TiO2 nanotubes growth stages for further optimization aiming the diverse applications. In this way the following systematic studies were performed: of the initial growth stages, of the effect of each anodization parameter on the nanotubes morphology and of the process reproducibility. In addition, methods for the production of self-sustained membranes as well as for obtaining a nanotube array surface free of nanoremnants were studied aiming the different applications. Positive photoresist bases sacrificial layer method presented a better result to eliminate nano-remnants on top of TiO2 nanotubes than other techniques. Finally, the nanotubes arrays obtained with this method were utilized for pH sensors fabrication.

Nos últimos anos, óxidos metálicos têm sido amplamente estudados para uma série de aplicações na indústria eletrônica e metalúrgica, sendo empregados em revestimentos anticorrosivos, sensores químicos, em dispositivos optoeletrônicos sensíveis, entre outros. Dentre os óxidos metálicos, o TiO2 (óxido de Titânio) tem enorme potencial em aplicações como sensor de gás, sensor de pH e em dispositivos fotossensíveis como células solares sensibilizadas por corante e para degradação fotocatalítica de compostos orgânicos. Há várias morfologias que podem ser obtidas para o TiO2, porém a de maior interesse atualmente é a de arranjos ordenados de nanotubos de TiO2 produzidos pelo processo de anodização do Ti, que por terem maior área superficial que outras morfologias como por exemplo, filmes finos, nanopilares e nanobastões, apresenta também maior sensibilidade à presença dos gases e/ou soluções a serem analisados, assim como maior absorção de fótons, além de uma menor recombinação de pares elétron-lacuna no material. Apesar destas várias vantagens, a atividade fotocatalítica do TiO2 é limitada por absorver apenas radiação ultravioleta devido a seu largo gap de aproximadamente 3,2 eV. Assim, neste trabalho foram produzidos nanotubos de TiO2 pelo processo de oxidação anódica do Ti, com diferentes parâmetros, correlacionando-os com a morfologia resultante. Com isso foi possível observar que o comprimento e diâmetro externo dos nanotubos de TiO2 crescem proporcionalmente com o aumento da tensão, sendo aproximadamente linear até um dado valor de saturação. A exceção a isto refere-se a nanotubos de TiO2 crescidos a partir de Ti depositado e substratos de vidro, no qual, há uma limitação de Ti a ser anodizado, de modo que após a conversão total do Ti em óxido não há mais o crescimento de nanotubos, porém os diâmetros gerados respeitam os mesmos valores para os casos em que não há essa limitação. Os nanotubos de TiO2 crescidos foram submetidos a processos de nitretação em um reator de deposição química a vapor assistida por plasma e os parâmetros foram avaliados com o intuito de encontrar as melhores condições para diminuição de seu gap, afim de aumentar sua atividade fotocatalítica. Pressão e potência de rádio frequência foram variados de 0,66 a 2,66 mBar (0,50 a 2,00 Torr) e 0,22 a 3,51 W/cm2 respectivamente. A maior diminuição no valor do gap, para 2,80 eV, foi obtida usando-se a pressão de 1,33 mBar (1,00 Torr), 1,75 W/cm2 de potência de rádio frequência durante um processo de 2 h a 320 °C, levando a uma diminuição de 14% no valor do gap e a um aumento de 25% na atividade fotocatalítica (redução de Azul de Metileno). Essa diminuição no valor do gap óptico dobra a abrangência de absorção de fótons de 5% para 10% do espectro solar. Os nanotubos de TiO2 nitretados produzidos com gap de 2,80 eV foram facilmente integrados a um microcanal de polidimetilsiloxano, produzindo um dispositivo fotocatalítico para estudo na fotodegradação de compostos orgânicos, podendo ser usado inclusive para redução de poluentes. O dispositivo fotocatalítico reduziu completamente 5 µL de solução de Azul de Metileno em cerca de 12 min, com uma taxa aproximadamente linear de 130 µM/h, enquanto os nanotubos de TiO2 como preparados apresentaram taxa de cerca de 115 µM/h. Logo, o dispositivo com nanotubos de TiO2 nitretados teve um aumento de 13% em sua eficiência de redução. / In recent years, metal oxides have been widely studied for a number of applications in the electronics and metallurgical industry, being used in anticorrosive coatings, chemical sensors, sensitive optoelectronic devices, among others. Among the metal oxides, TiO2 (titanium oxide) has enormous potential in applications such as gas sensor, pH sensor and in photosensitive devices such as dye sensitized solar cells and for photocatalytic degradation of organic compounds. There are several morphologies that can be obtained for TiO2, but the most interesting one today is ordered arrangements of TiO2 nanotubes produced by the Ti anodization process, which have a larger surface area than other morphologies such as thin films, nanopillars and nanobastones, also presents greater sensitivity to the presence of the gases and/or solutions to be analyzed, as well as greater absorption of photons, besides a smaller recombination of electron-hole pairs in the material. Despite these several advantages, the photocatalytic activity of TiO2 is limited by absorbing only ultraviolet radiation due to its wide gap of approximately 3.2 eV. Thus, in this work, TiO2 nanotubes were produced by the anodic oxidation process of Ti, with different parameters, correlating them with the resulting morphology. With this, it was possible to observe that the length and external diameter of the TiO2 nanotubes grow proportionally with the increase of the voltage, being approximately linear up to a given value of saturation. The exception to this relates to TiO2 nanotubes grown from Ti deposited and glass substrates, in which, there is a limitation of Ti to be anodized, so that after the total conversion of Ti to oxide, there is no longer growth of nanotubes, but the diameters generated respect the same values for cases in which there is no such limitation. The as grown TiO2 nanotubes were submitted to nitriding processes in a plasma assisted chemical vapor deposition reactor and the parameters were evaluated in order to find the best conditions to decrease their gap in order to increase their photocatalytic activity. Pressure and radio frequency power were varied from 0.66 to 2.66 mBar (0.50 to 2.00 Torr) and 0.22 to 3.51 W/cm2 respectively. The largest decrease in the gap value, to 2.80 eV, was obtained using the pressure of 1.33 mbar (1.00 Torr), 1.57 W/cm2 of radio frequency power during a process of 2 h in 320 °C, leading to a 14% decrease in gap value and a 25% increase in photocatalytic activity (reduction of Methylene Blue). This decrease in the value of the optical gap doubles the absorption range of photons from 5% to 10% of the solar spectrum. The nitrided TiO2 nanotubes produced with a gap of 2.80 eV were easily integrated into a microchannel of polydimethylsiloxane, producing a photocatalytic device for the study of photodegradation of organic compounds, and could be used to reduce pollutants. The photocatalytic device completely reduced 5 µL of Methylene Blue solution in about 12 min, with an approximately linear rate of 130 µM/h, whereas the TiO2 nanotubes as grown presented a rate of about 115 µM/h. Therefore, the device with nitrided TiO2 nanotubes had a 13% increase in its reduction efficiency.

A proposta deste trabalho é a produção de matrizes de nanotubos de dióxido de titânio seguindo os métodos de anodização eletroquímica de titânio estabelecidos da literatura. O objetivo central é a compreensão aprofundada das etapas do processo de crescimento dos nanotubos de TiO2, para posterior otimização de sua síntese visando as diferentes aplicações. Com este propósito foram realizados sistematicamente os seguintes estudos: das diferentes fases de crescimento dos nanotubos de TiO2, do efeito dos diferentes parâmetros de anodização na morfologia dos nanotubos e da reprodutibilidade dos processos. Visando as diferentes aplicações foram estudados métodos para obtenção de membranas autossustentadas e remoção de nanoresíduos. O método de camada sacrificial de fotoresiste positivo apresentou melhor resultado para remoção de nanoresíduos do topo dos nanotubos de TiO2 do que as demais técnicas. Por último, os arranjos obtidos com esta método foram aplicados na fabricação dos sensores de pH. / This work proposes the production of titania nanotubes arrays following the electrochemical anodization methods of a titanium sheet established in the literature. The main goal is a deep comprehension of the different TiO2 nanotubes growth stages for further optimization aiming the diverse applications. In this way the following systematic studies were performed: of the initial growth stages, of the effect of each anodization parameter on the nanotubes morphology and of the process reproducibility. In addition, methods for the production of self-sustained membranes as well as for obtaining a nanotube array surface free of nanoremnants were studied aiming the different applications. Positive photoresist bases sacrificial layer method presented a better result to eliminate nano-remnants on top of TiO2 nanotubes than other techniques. Finally, the nanotubes arrays obtained with this method were utilized for pH sensors fabrication.

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Nos últimos anos, óxidos metálicos têm sido amplamente estudados para uma série de aplicações na indústria eletrônica e metalúrgica, sendo empregados em revestimentos anticorrosivos, sensores químicos, em dispositivos optoeletrônicos sensíveis, entre outros. Dentre os óxidos metálicos, o TiO2 (óxido de Titânio) tem enorme potencial em aplicações como sensor de gás, sensor de pH e em dispositivos fotossensíveis como células solares sensibilizadas por corante e para degradação fotocatalítica de compostos orgânicos. Há várias morfologias que podem ser obtidas para o TiO2, porém a de maior interesse atualmente é a de arranjos ordenados de nanotubos de TiO2 produzidos pelo processo de anodização do Ti, que por terem maior área superficial que outras morfologias como por exemplo, filmes finos, nanopilares e nanobastões, apresenta também maior sensibilidade à presença dos gases e/ou soluções a serem analisados, assim como maior absorção de fótons, além de uma menor recombinação de pares elétron-lacuna no material. Apesar destas várias vantagens, a atividade fotocatalítica do TiO2 é limitada por absorver apenas radiação ultravioleta devido a seu largo gap de aproximadamente 3,2 eV. Assim, neste trabalho foram produzidos nanotubos de TiO2 pelo processo de oxidação anódica do Ti, com diferentes parâmetros, correlacionando-os com a morfologia resultante. Com isso foi possível observar que o comprimento e diâmetro externo dos nanotubos de TiO2 crescem proporcionalmente com o aumento da tensão, sendo aproximadamente linear até um dado valor de saturação. A exceção a isto refere-se a nanotubos de TiO2 crescidos a partir de Ti depositado e substratos de vidro, no qual, há uma limitação de Ti a ser anodizado, de modo que após a conversão total do Ti em óxido não há mais o crescimento de nanotubos, porém os diâmetros gerados respeitam os mesmos valores para os casos em que não há essa limitação. Os nanotubos de TiO2 crescidos foram submetidos a processos de nitretação em um reator de deposição química a vapor assistida por plasma e os parâmetros foram avaliados com o intuito de encontrar as melhores condições para diminuição de seu gap, afim de aumentar sua atividade fotocatalítica. Pressão e potência de rádio frequência foram variados de 0,66 a 2,66 mBar (0,50 a 2,00 Torr) e 0,22 a 3,51 W/cm2 respectivamente. A maior diminuição no valor do gap, para 2,80 eV, foi obtida usando-se a pressão de 1,33 mBar (1,00 Torr), 1,75 W/cm2 de potência de rádio frequência durante um processo de 2 h a 320 °C, levando a uma diminuição de 14% no valor do gap e a um aumento de 25% na atividade fotocatalítica (redução de Azul de Metileno). Essa diminuição no valor do gap óptico dobra a abrangência de absorção de fótons de 5% para 10% do espectro solar. Os nanotubos de TiO2 nitretados produzidos com gap de 2,80 eV foram facilmente integrados a um microcanal de polidimetilsiloxano, produzindo um dispositivo fotocatalítico para estudo na fotodegradação de compostos orgânicos, podendo ser usado inclusive para redução de poluentes. O dispositivo fotocatalítico reduziu completamente 5 µL de solução de Azul de Metileno em cerca de 12 min, com uma taxa aproximadamente linear de 130 µM/h, enquanto os nanotubos de TiO2 como preparados apresentaram taxa de cerca de 115 µM/h. Logo, o dispositivo com nanotubos de TiO2 nitretados teve um aumento de 13% em sua eficiência de redução. / In recent years, metal oxides have been widely studied for a number of applications in the electronics and metallurgical industry, being used in anticorrosive coatings, chemical sensors, sensitive optoelectronic devices, among others. Among the metal oxides, TiO2 (titanium oxide) has enormous potential in applications such as gas sensor, pH sensor and in photosensitive devices such as dye sensitized solar cells and for photocatalytic degradation of organic compounds. There are several morphologies that can be obtained for TiO2, but the most interesting one today is ordered arrangements of TiO2 nanotubes produced by the Ti anodization process, which have a larger surface area than other morphologies such as thin films, nanopillars and nanobastones, also presents greater sensitivity to the presence of the gases and/or solutions to be analyzed, as well as greater absorption of photons, besides a smaller recombination of electron-hole pairs in the material. Despite these several advantages, the photocatalytic activity of TiO2 is limited by absorbing only ultraviolet radiation due to its wide gap of approximately 3.2 eV. Thus, in this work, TiO2 nanotubes were produced by the anodic oxidation process of Ti, with different parameters, correlating them with the resulting morphology. With this, it was possible to observe that the length and external diameter of the TiO2 nanotubes grow proportionally with the increase of the voltage, being approximately linear up to a given value of saturation. The exception to this relates to TiO2 nanotubes grown from Ti deposited and glass substrates, in which, there is a limitation of Ti to be anodized, so that after the total conversion of Ti to oxide, there is no longer growth of nanotubes, but the diameters generated respect the same values for cases in which there is no such limitation. The as grown TiO2 nanotubes were submitted to nitriding processes in a plasma assisted chemical vapor deposition reactor and the parameters were evaluated in order to find the best conditions to decrease their gap in order to increase their photocatalytic activity. Pressure and radio frequency power were varied from 0.66 to 2.66 mBar (0.50 to 2.00 Torr) and 0.22 to 3.51 W/cm2 respectively. The largest decrease in the gap value, to 2.80 eV, was obtained using the pressure of 1.33 mbar (1.00 Torr), 1.57 W/cm2 of radio frequency power during a process of 2 h in 320 °C, leading to a 14% decrease in gap value and a 25% increase in photocatalytic activity (reduction of Methylene Blue). This decrease in the value of the optical gap doubles the absorption range of photons from 5% to 10% of the solar spectrum. The nitrided TiO2 nanotubes produced with a gap of 2.80 eV were easily integrated into a microchannel of polydimethylsiloxane, producing a photocatalytic device for the study of photodegradation of organic compounds, and could be used to reduce pollutants. The photocatalytic device completely reduced 5 µL of Methylene Blue solution in about 12 min, with an approximately linear rate of 130 µM/h, whereas the TiO2 nanotubes as grown presented a rate of about 115 µM/h. Therefore, the device with nitrided TiO2 nanotubes had a 13% increase in its reduction efficiency.

Biomaterials have been used for more than a century in the human body to improve body functions and replace damaged tissues. Currently approved and commonly used metallic biomaterials such as, stainless steel, titanium, cobalt chromium and other alloys have been found to have adverse effects leading in some cases, to mechanical failure and rejection of the implant. The physical or chemical nature of the degradation products of some implants initiates an adverse foreign body reaction in the tissue. Some metallic implants remain as permanent fixtures, whereas others such as plates, screws and pins used to secure serious fractures are removed by a second surgical procedure after the tissue has healed sufficiently. However, repeat surgical procedures increase the cost of health care and the possibility of patient morbidity. This study focuses on the development of magnesium based biodegradable alloys/metal matrix composites (MMCs) for orthopedic and cardiovascular applications. The Mg alloys/MMCs possessed good mechanical properties and biocompatible properties. Nine different compositions of Mg alloys/MMCs were manufactured and surface treated. Their degradation behavior, ion leaching, wettability, morphology, cytotoxicity and mechanical properties were determined. Alloying with Zn, Ca, HA and Gd and surface treatment resulted in improved mechanical properties, corrosion resistance, reduced cytotoxicity, lower pH and hydrogen evolution. Anodization resulted in the formation of a distinct oxide layer (thickness 5-10 μm) as compared with that produced on mechanically polished samples (~20-50 nm) under ambient conditions. It is envisaged that the findings of this research will introduce a new class of Mg based biodegradable alloys/MMCs and the emergence of innovative cardiovascular and orthopedic implant devices.

Bone implants procedures involve millions of people every year worldwide. One of the main factors determining implant success is related to the ability of the prostheses to osseointegrate, i.e. to create a structural and functional connection with the living bone. Titanium and titanium alloys are widely used biomaterials for bone implants, due to their superior biocompatibility and corrosion resistance, suitable mechanical properties, and natural ability to osseointegrate. To further enhance the inherent tendency of this class of materials to bond with the host bone tissue, the surface of Ti-based implant is often modified to improve cell responses in terms of adhesion, proliferation and differentiation, all factors contributing to successful osseointegration. In particular, surface topography, both at the micro- and nanoscale, can enhance the implant-living bone interaction. Herein, a possible surface modification strategy aimed at the creation of a dual-scale topography on two different titanium alloys, Ti-6Al-4V and Ti-5Al-5Mo-5V-3Cr, is presented. Dual-scale topography was obtained by electrochemically anodizing samples manufactured by selective laser melting to combine their intrinsic microtopography with the nanotopography offered by titanium dioxide nanotubes (TNTs) generated by anodization. Characterization of the as-printed and as-anodized samples was performed to evaluate parameters of significance in the context of osseointegration. Concerning wettability, it was observed that surfaces with TNTs exhibited high hydrophilicity. The influence of the anodization process parameters on TNTs morphology was examined, and linear dependence of the nanotube diameter on the voltage was identified. Annealing of the as-anodized samples showed that anatase was produced, while preserving the nanotube integrity. Preliminary studies to assess the bioactive properties of the samples showed the spreading of bone-like cells on these substrates and the deposition of mineral during simulated body fluid testing. Therefore, both studies provided promising results to corroborate the hypothesis that dual-scale topography could potentially improve osseointegration. / Thesis / Master of Applied Science (MASc) / Bone implants are often made of titanium-based materials, which, despite their suitable properties, may not sufficiently bond with the living bone tissue. This can lead to implant loosening and failure. To produce customized implants, additive manufacturing, or 3D-printing, can be employed. However, these surfaces require substantial post-processing to produce features capable of promoting bone integration. In this work, a dual-scale surface topography to combine the advantages of both micro- and nanoscale roughness was created using electrochemical anodization on 3D-printed titanium alloy substrates. Preliminary physical, chemical, and biological characterizations suggest that the creation of titania nanotubes on the 3D-printed surfaces of Ti-6Al-4V and Ti-5Al-5Mo-5V-3Cr could improve their ability to bond with bone.