published_or_final_version / Dentistry / Doctoral / Doctor of Philosophy

M. Tech. Metallurgical Engineering / Titanium alloys exhibit poor tribological characteristic which include abrasion resistance, metal to metal wear resistance and solid particle erosion and cavitation due to low surface hardness and high coefficient of friction. These poor properties have limited the application of titanium alloys as engineering tribological components, tools and parts that operate in severe wear and friction conditions. Laser processing defects such as pores, cracks and segregation pose a huge threat to the quality and the microstructure of the deposited layer. Defects caused by the parameters lead to severe wear and corrosion occurrence, hence, precise control of the parameters are crucial and it depends on the properties of the material used. It is postulated that Nickel Titanium (NiTi) is a promising candidate as reinforcement matrix material for wear resistant alloy. The wear resistance would be further enhanced if NiTi is in-situ incorporated onto titanium matrix by laser cladding to yield hard intermetallic phases. The main goal of the study is to develop corrosive-wear resistant thin surface coatings on Ti-6Al-4V alloy for automotive and aerospace applications by depositing Titanium and Nickel elemental powders to form in-situ NiTi intermetallic using laser cladding technique.

Shape memory alloys (SMAs) have been recognized as one of the most promising materials for MEMS micro-actuator applications. Among the available materials, Nickel/Titanium (NiTi) SMAs are more popular because, they exhibit unique properties in shape memory effect (SME) and pseudo-elasticity (PE). In addition NiTi SMA possesses high corrosion resistance, excellent mechanical properties and is also bio¬compatible. NiTi thin-film SMAs have been considered as the most significant material in the field of MEMS applications, which can be patterned with standard lithographic techniques to scale-up for batch production. However, the lack of proper understanding of basic materials’ properties and inability to reproduce, has limited the usage of this material in MEMS devices. The properties of NiTi SMA thin-films are very much sensitive to the elemental composition and structure, which are in turn decided by the deposition process and process parameters. A brief history of NiTi shape memory alloys (SMAs), basic information, transformation characteristics, crystal structure, phase diagram and literature reviewed for the current motivation have been presented in the second chapter In the third chapter, a brief summary about the deposition techniques relevant to NiTi film deposition has been presented. The deposition of NiTi films by a number of deposition techniques such as thermal evaporation, co-evaporation, molecular beam Epitaxy, pulsed laser deposition, flash evaporation, electron beam deposition, filtered arc deposition, ion beam assisted sputter deposition, vacuum plasma spraying, ion beam sputtering, ECR sputtering and magnetron sputtering techniques have been discussed. In order to achieve a precise control over film thickness and composition of the films on to the substrates, the selection of magnetron sputtering has been highlighted. In the present thesis, two prolonged approaches such as DC magnetron sputtering of an alloy target and co-sputtering of elemental targets have been presented. Various characterization techniques used for film thickness, composition, structure, micro¬structure, electrical, phase transformation and mechanical properties have also been briefly presented in the same chapter. In the fourth chapter, description of Conventional Alloy Target Sputtering System has been presented. DC magnetron sputtering of an alloy target with two different atomic ratios (Ni:Ti = 45:55 & 50:50) has been used for depositing the coatings. Several limitations in the reproducibility and repeatability have been observed with single alloy target sputtering, irrespective of the target composition ratio. In addition to this, incorporation of oxygen in the films during and after deposition has been observed, which has limited the extensive usage of this single alloy target system. The limitations regarding control over composition, thickness uniformity over large area have been improved by designing and fabricating a dedicated Three Target Magnetron Co-sputtering System. The vacuum diagnosis of the system under different conditions has been carried out by using PPR-200 Residual Gas Analyzer (RGA), which have included in Appendix I. Similar to alloy target sputtering system, the thickness uniformity and required composition with deposition parameters over a size of 75 mm diameter has been achieved and the process repeatability has been established. Oxygen incorporation in the films during deposition has been minimized by pre-sputtering of Ti target for known duration of time, which has resulted in significant reduction in partial pressure of oxygen in the chamber. The oxide layer formation on film surface has been eliminated by in-situ capping layer (TiN) deposition. In the fifth chapter, the influence of process parameters such as sample locations, substrate to target distance (STD), working pressure (WP), gas flow rates, deposition rates, deposition and annealing temperature, Target power, on the film thickness and composition uniformity have been presented for alloy target sputtering system as well as for the co-sputtering system. The film thicknesses have been measured with stylus method. Film compositions have been determined by energy dispersive X-ray spectroscopy (EDS), Secondary ion mass spectrometry (SIMS), Rutherford backscattering spectrometry (RBS) and X-ray photoelectron spectroscopy (XPS). The working pressure of 1.5 X 10-3 mbar, STD of 90 mm and target power of 100 W have been found to produce coatings having uniform thickness and composition over the given area for alloy target sputtering system. Similar investigations have been carried out for co-sputtered NiTiCu films. The working pressure of 1.5x 10-3 mbar, at a STD of 90 mm, at a rotational speed of 15 rpm and at target powers of 600, 50 and 12 W for Ti, Ni and Cu respectively, have resulted in the thickness and required composition uniformity over a size of 75 mm diameter substrate and the process repeatability has been established. In the Sixth chapter, the influence of process parameters on film structure and micro-structure on the NiTi/NiTiCu films deposited by a single alloy target and co¬sputtering have been studied by different analytical techniques like XRD, TEM, AFM, SEM etc. Phase transformation temperatures and kind of transformations have been investigated by DSC, Resistivity / Temperature and Stress/ Temperature studies and correlations have been established. The process parameters have been optimized for TiN deposition, which act as the capping layer to protect NiTi films from surface oxidation. The variation in mechanical behavior for the NiTi/ NiTiCu films before and after TiN capping by nano-indentation test have also presented. XRD and TEM studies have shown that the NiTi / NiTiCu films deposited at room temperature to 400o C are amorphous. Post-annealing, at a temperature of 450O C or above resulted in the film crystallization with oxide layer formation at the film surface, which has been confirmed by XRD and XTEM studies. In the case of Ni-rich NiTi films, R-phase diffraction peaks have also been identified in addition to the Austenite / Martensite phase. XRD investigations have shown that Ti-rich NiTi and Ni-rich NiTi films have resulted in precipitate free films. In the case of Ti-rich NiTiCu and Ni-rich NiTiCu films, the variations in Ti/Ni target power has resulted in the formation of NiTi 2 and Ni3Ti precipitates along with their parent Martensite and Austenite phases. When the Cu content is increased in NiTiCu films, an increase in number of Martensite phase diffraction peaks in XRD spectrum has been observed. XTEM studies have confirmed formation of oxide layer, inter-metallic layer and interface layer at higher post annealing temperatures. SEM studies have shown that the films deposited at higher gas flow rate results in the columnar micro-structure. In the context of NiTiCu films, the films deposited at higher Ti target power have shown more compact and tightly packed film micro-structure. AFM studies have shown increase in the average crystallite size and film roughness with post annealing temperature and duration. TiN coating has been used as the capping layer onto NiTi / NiTiCu films. Structural and micro-structural comparison of these films before and after TiN coating has resulted the appearance of (111) TiN peak in all TiN capped films. SEM and AFM studies have shown that the film roughness have decreased after capping layer deposition. DSC thermal cycling used to verify the film crystallization temperature has shown the appearance of exothermic peak in NiTi / NiTiCu films. DSC, Resistivity-temperature, stress-temperature response has been confirmed the transformation temperature and kind of transformations in all the films. Residual stress measurements have shown that the crystalline films exhibited lower bi-axial stress in comparison to the amorphous films. Ti-rich NiTi films have shown single phase transformations (M-A and A-M) whereas two phase transformations (M-R-A and A-R-M) have been observed in Ni-rich NiTi films. Higher deposition / annealing temperature have shown the appearance of distinct phase transformation peaks in resistivity vs. temperature studies. In the case of NiTiCu films, the decrease in film crystallization temperature with increase in the Cu content has been observed. The phase transformation temperature evaluated from second thermal cycle has shown decrease in the width of hysteresis loop with increase in the Cu content in NTC films. Nano-indentation studies have been carried out to evaluate the micro-hardness and modulus values of TiN capped and uncapped NiTi / NiTiCu films. The modulus and hardness uniformity have been confirmed for the different location over a diameter of 75 mm. The modulus and hardness values have increased with increase in the substrate and annealing temperature. Increase in the Cu target power has resulted in the increase in the hardness and modulus values under same deposition conditions. TiN coated NiTi / NiTiCu films have shown larger modulus and hardness values than the uncapped films. In the Seventh chapter, the fabrication process and actuation response for silicon dioxide, Aluminum and NiTi SMA coated micro-cantilevers has been discussed. Various nano-structures such as pyramids, beams and pillars by focused ion beam (FIB) micro-machining have been fabricated. High aspect ratio nano-pillars have been selected for micro-compression testing. In summary, this thesis emphasizes on the fabrication of specific sputtering systems relevant to NiTi film deposition and process parameter optimization for desired film thickness and composition uniformity. DC magnetron sputtering of a NiTi alloy target (50:50 and 45:55 at. %) and co-sputtering of elemental targets (Ni, Ti and Cu) have been presented. These films have been investigated for structural, micro-structural, phase transformation and mechanical properties. In-situ deposition of TiN capping layer, on to NiTi / NiTiCu films has been carried out to reduce the oxygen trapping. The fabrication process and actuation response of micro-cantilevers have been described. The etching characteristics to generate various nano-structures viz. pyramids, beams and pillars by focused ion beam (FIB) micro-machining have been investigated and mechanical testing of selected nano-structures have also been reported.

Thesis (M.S.)--University of Alabama at Birmingham, 2007. / Additional advisors: Peter G. Anderson, Brigitta C. Brott, Jack E. Lemons. Description based on contents viewed Feb. 4, 2008; title from title screen. Includes bibliographical references (p. 69-70).

Orientador: Renato de Toledo Leonardo / Banca: Idomeo Bonetti Filho / Banca: Celso Kenji Nishiyama / Resumo: Foram avaliadas comparativamente três técnicas híbridas automatizadas de preparo de canais radiculares, Free Tip, Endo-Eze Híbrida e Race. Neste trabalho, foram utilizados 24 pré-molares artificiais, confeccionados em resina, com canais radiculares únicos, com curvatura de quarenta graus e raio de quatro milímetros. Para a avaliação dos preparos dos canais radiculares, os dentes foram divididos em três grupos e seccionados no terço apical das raízes. As secções das raízes foram então captadas antes e após a instrumentação de forma padronizada e as imagens transferidas para o computador que procedeu às analises comparativas. A avaliação baseou-se na extensão do deslocamento e na direção do movimento do centro do canal radicular. Apesar de a técnica Endo-Eze Híbrida ter apresentado um menor deslocamento do centro do canal radicular do que as técnicas Free Tip e Race, não houve diferença estatisticamente significante entre as técnicas estudadas. / Abstract: Three different techniques of automated instrumentation of root canal preparation were evaluated, Free tip, Hybrid Endo-Eze and Race. Twenty four single rooted artificial resin pre-molars were manufactured whith an apical curvature of 40-degree angle and 4 millimeters of radius each. For the evaluation of root canal preparation, the artificial teeth were divided in three groups and sectioned at the apical third. The sections were taken before and after the instrumentation on a standardize way and the images obtained were transferred to a computer for comparative analysis. The evaluation was based on the extension of canal displacement and the direction of the canal center movement. Although the Hybrid Endo-Eze technique had presented a smaller deviation of root canal center than Free Tip and Race techniques, there was no statistical difference between the analysed techniques. / Doutor

Made available in DSpace on 2014-06-11T19:31:25Z (GMT). No. of bitstreams: 0 Previous issue date: 2006-05-19Bitstream added on 2014-06-13T20:01:53Z : No. of bitstreams: 1 araujo_fbc_dr_sjc.pdf: 312103 bytes, checksum: 3f21d0423598e73724ad1f5cf82e2469 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Analisaram-se separada e comparativamente três marcas comerciais de elásticos ortodônticos sintéticos e de molas de NiTi (MORELLI, ORMCO e GAC), quanto à degradação da força sofrida por estes materiais em função do tempo, quando submetidos a simulação das condições bucais. Os elásticos e molas foram inicialmente termociclados (temperaturas de 15°C e 45°C), em seguida estirados em 20mm, imersos em saliva artificial a 37°C e desativados em 0,5mm semanais. As leituras da quantidade de força gerada pelas amostras foram realizadas nos momentos: inicial, 1, 24, 48 horas, 7, 14, 21 e 28 dias. Observou-se significativa redução na quantidade de força gerada pelos elásticos na primeira hora de ativação, que variou de 49,5% a 53%, enquanto que para as molas a degradação foi signicativamente menor, com valores entre 4,2% e 18,1%. Ao término de 28 dias de testes, as amostras de elásticos sofreram redução média na quantidade de força gerada entre 82,7% e 91,2% (GAC-82,7%, ORMCO-86,0% e MORELLI- 91,2%) já as amostras de molas apresentaram degradação média de força entre 17,5% e 32,2% (MORELLI-17,5%, ORMCO-27,3% e GAC-32,2%). Concluiu-se que, em geral, os elásticos promoveram maior índice inicial de força que as molas, mas após as primeiras 24 horas de ativação a quantidade de força gerada pelos elásticos era menor que a promovida pelas molas, que assim apresentaram níveis médios de força mais constantes que os elásticos ao longo dos testes. / Three commercial marks of synthetic elastics and NiTi coil springs (MORELLI, ORMCO, GAC) were separately and comparably analyzed, according to the force degradation generated by these materials, because of the time, when maintained stretched in artificial salivary, 37°C. The synthetic elastics and NiTi coil springs were thermal- cycled (15°C-45°C) and stretched in 20mm, and this stretch was reduced in 0,5mm weekly. The readings of the amount generated for elastics and coil springs were done in the intervals 0, 1, 24, 48h, 7, 14, 21 and 28 days. Where observed significative reduction on the amount of force generated for the elastics in the first hour of the activation (49,5%- 53%), and 82,7% - 91,2% in 28 days of the tests ( MORELLI - 91,2%, ORMCO - 86,0%, GAC - 82,7%);, while the generated force for NiTi coil springs suffered a reduction of 4,2%- 18,1%, in the first hour of the experimentation and 17,5% - 32,2% in 28 days of the stretch (MORELLI - 17,5%, ORMCO - 27,3%, GAC - 32,2%). We conclude that for most elastics delivered larger initial force that NiTi coil springs, but after 24 hours of activation the NiTi coil springs delivered larger force that the elastics and generated level of the force more constant that elastics.

Made available in DSpace on 2014-06-11T19:31:32Z (GMT). No. of bitstreams: 0 Previous issue date: 2004-03-04Bitstream added on 2014-06-13T21:02:37Z : No. of bitstreams: 1 camargo_jmp_dr_arafo.pdf: 622434 bytes, checksum: e10a27eeda1607b463fd51b6ce1ff55c (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Foram avaliados comparativamente três sistemas de técnicas automatizadas de preparo dos canais radiculares, Endo-Eze, K3 e Race. Neste trabalho, foram utilizados 30 pré-molares artificiais, confeccionados em resina, com canais radiculares únicos, com curvatura de quarenta graus. Para a avaliação do preparo dos canais radiculares, os dentes foram divididos em três grupos, incluídos em blocos de resina e seccionados no terço apical das raízes. As secções das raízes foram fotografadas antes e após a instrumentação de forma padronizada e as imagens transferidas para o computador que procedeu às análises comparativas. A avaliação baseou-se na extensão do deslocamento, na direção do movimento do centro do canal radicular e na área desgastada. Em relação ao preparo dos canais, os sistemas Endo-Eze e K3, apresentaram um deslocamento do centro do canal radicular maior do que o sistema Race. Menores valores de desgaste foram observados para o sistema Race, seguido dos sistemas K3 e Endo-Eze. Os dentes utilizados neste estudo mostraram-se eficazes na avaliação de diferentes técnicas de instrumentação. / Three different systems of automated instrumentation techniques of root canal preparation were evaluated, Endo-Eze, K3 and Race. Thirty single rooted artificial resin pre-molars were manufacture with an apical curvature of 40-degree angle each. For the evaluation of the root canal preparation, the artificial teeth were divide in three groups, included in resin blocks and sectioned at the apical third. The sections were photographed before and after the instrumentation on a standardize way and the images obtained were transferred to a computer for the comparative analysis. The evaluation was based on the extension of canal displacement, the direction of the canal center movement and at the removed area. Concerning the root canal preparations, the Endo-Eze and K3 systems presented a bigger deviation of the center of the original root canal bigger them the Race system. Lower values for the Race system were observed fallowed by the K3 and Endo-Eze. The artificial teeth utilized in this study were efficient for the evaluation of different automated instrumentation techniques.

Made available in DSpace on 2014-06-11T19:31:33Z (GMT). No. of bitstreams: 0 Previous issue date: 2006-03-10Bitstream added on 2014-06-13T21:02:40Z : No. of bitstreams: 1 zanin_fp_me_arafo.pdf: 546745 bytes, checksum: 092d588a4cd9251dab98907a113bad3c (MD5) / Universidade Estadual Paulista (UNESP) / Foram avaliadas comparativamente três técnicas híbridas automatizadas de preparo de canais radiculares, Free Tip, Endo-Eze Híbrida e Race. Neste trabalho, foram utilizados 24 pré-molares artificiais, confeccionados em resina, com canais radiculares únicos, com curvatura de quarenta graus e raio de quatro milímetros. Para a avaliação dos preparos dos canais radiculares, os dentes foram divididos em três grupos e seccionados no terço apical das raízes. As secções das raízes foram então captadas antes e após a instrumentação de forma padronizada e as imagens transferidas para o computador que procedeu às analises comparativas. A avaliação baseou-se na extensão do deslocamento e na direção do movimento do centro do canal radicular. Apesar de a técnica Endo-Eze Híbrida ter apresentado um menor deslocamento do centro do canal radicular do que as técnicas Free Tip e Race, não houve diferença estatisticamente significante entre as técnicas estudadas. / Three different techniques of automated instrumentation of root canal preparation were evaluated, Free tip, Hybrid Endo-Eze and Race. Twenty four single rooted artificial resin pre-molars were manufactured whith an apical curvature of 40-degree angle and 4 millimeters of radius each. For the evaluation of root canal preparation, the artificial teeth were divided in three groups and sectioned at the apical third. The sections were taken before and after the instrumentation on a standardize way and the images obtained were transferred to a computer for comparative analysis. The evaluation was based on the extension of canal displacement and the direction of the canal center movement. Although the Hybrid Endo-Eze technique had presented a smaller deviation of root canal center than Free Tip and Race techniques, there was no statistical difference between the analysed techniques.

Made available in DSpace on 2014-06-11T19:24:38Z (GMT). No. of bitstreams: 0 Previous issue date: 2004-02-16Bitstream added on 2014-06-13T19:52:07Z : No. of bitstreams: 1 leonardi_dp_me_arafo.pdf: 741813 bytes, checksum: 2517134a5a1799a4a8f6f37ddf2985b0 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Foram analisadas, comparativamente, a ação e a presença de deformações proporcionadas pela instrumentação com limas manuais Flexofile e dois Sistemas Rotatórios de Limas Endodônticas de Níquel e Titânio: o Sistema K3 (SDS Kerr) e o Sistema Race (FKG), sobre as paredes dos canais radiculares curvos simulados em blocos de resina. Foram utilizadasa as técnicas manual e ultra-sônica de irrigação. Após a instrumentação, os blocos de resina foram digitalizados, analisados e estabelecido escores de acordo com a qualidade do preparo biomecânico obtido em cada uma das técnicas. Concluímos que os melhores resultados foram obtidos com as duas técnicas de instrumentação rotatória associadas à irrigação manual. / It were comparatively analyzed the action and aberrations provided by the instrumentation using manual files Flexofile and two Rotary Systems of Endodontic Nickel-Titanium files, the K3 (SDS Kerr) System and the Race (FKG) System, in the curved root canal walls simulated in resin blocks, with two irrigations techniques: a manual and an ultrasonic technique. Thereafter the instrumentation, the resin blocks were digitalized, analysed and scores were set according to the preparation's quality achieved in each technique. It was ended that the best results were obtained with the two techniques of rotary instrumentation associated to the manual irrigation.

Made available in DSpace on 2014-06-11T19:24:38Z (GMT). No. of bitstreams: 0 Previous issue date: 2000-11-08Bitstream added on 2014-06-13T19:25:39Z : No. of bitstreams: 1 camargo_jmp_me_arafo.pdf: 2506915 bytes, checksum: 3c82c9bacd6db2893e1c2f01ff217116 (MD5) / Foram avaliadas comparativamente as técnicas Quantec LX, Pow-R, Profile e Profile série 29, em blocos de resina com canais radiculares simulados, as deformações produzidas nas paredes côncavas e convexas, através da editoração de imagens com a utilização do programa AutoCAD. Os resultados nos permitiram concluir que o sistema que mais provocou a ampliação foi o sistema Quantec LX seguido respectivamente pelo sistema Profile série 29, sistema Profile e sistema Pow-R. Permitiu também fazer uma análise matemática de qual a quantidade e local do desgaste nos níveis 1, 3, 5, 7, 12 e 16 milímetros. / It was comparatively evaluated the Quantec LX, Pow-R, Profile and Profile series 29 techniques, utilizing resin blocks, with simulated canals. The evaluation was done with the AutoCAD program after image editoration. The results led us to conclude that, the Quantec LX system promoted the greater amplification of the root canal, folowed by Profile series 29, Profile and Pow-R systems. This kind of analysis, alowed us to concluse also, where and the quantity of wear in different levels.