Nos defeitos bucomaxilofaciais, a intervenção cirúrgica utilizando enxertos ou substi-tutos ósseos é indicada para reestabelecer a forma e a função perdidas. Nesse con-texto, enxertos auto?genos e alo?genos te?m sido substituídos por biomateriais osteo-condutores e reabsorvíveis. O objetivo deste trabalho foi avaliar por meio de micro-tomografia e dos aspectos histológicos do reparo ósseo, se um novo cimento bifási-co composto por sulfato de cálcio e beta fosfato tricálcico com controle de potencial zeta, poderia induzir ou conduzir a neoformação óssea em defeitos críticos, produzi-dos em calvárias de ratos. Foi realizado um defeito crítico de 8mm de diâmetro na calvária de 40 ratos Wistar machos. No grupo teste (n=20) os defeitos foram preen-chidos pelo cimento. No grupo controle (n=20) os defeitos não foram preenchidos e permaneceram apenas com o coágulo. Os animais sofreram eutanásia em 7, 14, 21 e 42 dias do pós operatório. Espécimes da região da ferida foram microtomografa-dos e posteriormente as amostras foram preparadas para análise histológica. A aná-lise histomorfológica incluiu a avaliação morfológica da histopatologia do reparo, a avaliação morfométrica da área de formação das trabéculas ósseas comparativa-mente entre os grupos. Realizamos ainda a coloração com fosfatase tartrato-resistente (TRAP) para identificação de osteoclastos. Os resultados mostraram que os defeitos preenchidos pelo cimento não apresentaram diminuição significativa da área de acordo com a progressão dos períodos pós-operatórios, pelo contrário, em alguns animais, o defeito aparentemente aumentou. A histomorfologia do reparo mostrou agrupamentos mais expressivos de células gigantes no grupo teste suge-rindo resposta a corpo estranho e osso neoformado mais maduro no grupo controle No grupo teste houve permanência do material e resposta corpo estranho até os úl-timos períodos de observação. Na histomorfometria, a área total de neoformação óssea na região da ferida foi significativamente maior e crescente com o passar do tempo experimental no grupo controle do que no grupo teste. As células gigantes apresentaram expressão histoquímica positiva para TRAP e não foram identificados osteoclastos. Concluímos que neste modelo de estudo, o cimento cerâmico não in-duziu ou conduziu a neoformação óssea de defeitos ósseos críticos criados em cal-vária de ratos sob o ponto de vista microtomográfico e histológico. / Surgical intervention employing grafts and bone substitutes is the best choice in oral and maxillofacial bone defects reconstruction for structural and functional lost. Re-garding this, autogenous and alogenous grafts have been used as osteocondutive and resorbable biomaterials. The aim of this study was to evaluate if a new bone bi-phasic composite of calcium sulfate and beta tricalcium phosphate with zeta potential control could induce or conduct bone formation in rats\' calvarias critical defects mod-el. Forty male Wistar rats underwent 8mm diameter calvaria perforation under gen-eral anesthesia. Animals were randomly allocated to group test (n=20), when the de-fects were filled with the biphasic phosphate and group control (n=20) when the wound was left just with blood clot. Animals underwent euthanasia 7, 14, 21 and 42 days after surgery. Bone calvaria specimens underwent microtomography and histo-logical processing for analysis. Histomorphological and histomorphometry were per-formed regarding aspects of bone healing evolution and new bone total area within the defect. Additionally, histological samples were tartrate-resistant phosphatase (TRAP) stained for osteoclasts identification. The results showed that defects filled by the composite did not present significant bone formation considering postoperative evolution, on the contrary it seemed that the defect area increased in some animals. The bone repair histomorphology in test-group showed expressive giant cells nests involving the ceramic material suggesting foreign body reaction. A mature bone tis-sue neoformation was significantly more intense in the control-group. In the test-group the permanence of the exogenous material caused the sustained foreign body reaction until the last observational periods. Histomorphometric analysis showed that in control-group the total area of bone formation was significantly greater and pro-gressive along the experiment than the test-group. Osteoclasts were not identified but the giant cells presented positive reaction to TRAP. It was possible to conclude that the biphasic ceramic with zeta potential control was not capable to induce or conduct bone neoformation in critical defects created in rats\' calvaria.

Abstract des Vortrages: Titanium aluminide (TiAl) alloys are attractive lightweight materials for mediumtemperature (500°-750°C) structural applications including components such as jet engine and industrial gas turbine blades, turbocharger rotors and automotive engine valves. However, envisaged service temperatures for future advanced applications will have to be in the range of 750° to 1000°C, over which these alloys suffer from both oxidation and oxygen embrittlement. Therefore, development of surfaceengineering techniques for preventing high-temperature environmental damage is critical in exploiting the advantages of TiAl alloys to their fullest extent. Two efficient approaches to protecting candidate TiAl alloys from high-temperature (>750°C) environmental degradation have been developed at HZDR. The first technique involves a single step, namely treating TiAl alloy components directly by plasma immersion ion implantation (PIII) of fluorine using a mixture of difluoromethane and argon (CH2F2 + 25% Ar) as the precursor gas. The oxidation performance of the fluorine-implanted alloys has been evaluated by thermal gravimetric analysis (TGA) over the temperature range of 750° to 1050°C under conditions of both isothermal and thermal cyclic oxidation in air, and for times as long as 6000 h. This type of surface modification has been shown to produce a stable, adherent and highly protective alumina scale. The second technique involves the fabrication of a durable protective coating in a two-step process, namely formation of a thin aluminum-rich TiAl layer (Ti-60Al) by chemical vapor deposition (CVD) employing a mixture of inorganic precursors, followed by PIII of fluorine. Subsequent long-term oxidation exposures to air at 900°C of a GE 4822 alloy (Ti-48Al-2Cr-2Nb; alloy composition qualified for aerospace applications) have shown that the coating so developed is able to successfully prevent oxidation damage to the base material while maintaining up to 90% of its initial mechanical properties (strength and ductility).

Abstract des Vortrages: Titanium aluminide (TiAl) alloys are attractive lightweight materials for mediumtemperature (500°-750°C) structural applications including components such as jet engine and industrial gas turbine blades, turbocharger rotors and automotive engine valves. However, envisaged service temperatures for future advanced applications will have to be in the range of 750° to 1000°C, over which these alloys suffer from both oxidation and oxygen embrittlement. Therefore, development of surfaceengineering techniques for preventing high-temperature environmental damage is critical in exploiting the advantages of TiAl alloys to their fullest extent. Two efficient approaches to protecting candidate TiAl alloys from high-temperature (>750°C) environmental degradation have been developed at HZDR. The first technique involves a single step, namely treating TiAl alloy components directly by plasma immersion ion implantation (PIII) of fluorine using a mixture of difluoromethane and argon (CH2F2 + 25% Ar) as the precursor gas. The oxidation performance of the fluorine-implanted alloys has been evaluated by thermal gravimetric analysis (TGA) over the temperature range of 750° to 1050°C under conditions of both isothermal and thermal cyclic oxidation in air, and for times as long as 6000 h. This type of surface modification has been shown to produce a stable, adherent and highly protective alumina scale. The second technique involves the fabrication of a durable protective coating in a two-step process, namely formation of a thin aluminum-rich TiAl layer (Ti-60Al) by chemical vapor deposition (CVD) employing a mixture of inorganic precursors, followed by PIII of fluorine. Subsequent long-term oxidation exposures to air at 900°C of a GE 4822 alloy (Ti-48Al-2Cr-2Nb; alloy composition qualified for aerospace applications) have shown that the coating so developed is able to successfully prevent oxidation damage to the base material while maintaining up to 90% of its initial mechanical properties (strength and ductility).

The design and manufacture of lightweight electric vehicles is becoming increasingly important with the rising cost of petrol, and the effects emissions from petrol powered vehicles are having on our environment. The University of Waikato and HybridAuto's Ultracommuter electric vehicle was designed, manufactured, and tested. The vehicle has been driven over 1800km with only a small reliability issue, indicating that the Ultracommuter was well designed and could potentially be manufactured as a solution to ongoing transportation issues. The use of titanium aluminide components in the automotive industry was researched. While it only has half the density of alloy steel, titanium aluminides have the same strength and stiffness as steel, along with good corrosion resistance, making them suitable as a lightweight replacement for steel components. Automotive applications identified that could benefit from the use of TiAl include brake callipers, brake rotors and electric motor components.

Submitted by Renata Lopes (renatasil82@gmail.com) on 2018-08-22T15:35:41Z No. of bitstreams: 1 evertonluizmartinsdapaixao.pdf: 15592539 bytes, checksum: 3e2c3d43b62b9fa0edea517213c63a12 (MD5) / Approved for entry into archive by Adriana Oliveira (adriana.oliveira@ufjf.edu.br) on 2018-09-03T16:33:20Z (GMT) No. of bitstreams: 1 evertonluizmartinsdapaixao.pdf: 15592539 bytes, checksum: 3e2c3d43b62b9fa0edea517213c63a12 (MD5) / Made available in DSpace on 2018-09-03T16:33:20Z (GMT). No. of bitstreams: 1 evertonluizmartinsdapaixao.pdf: 15592539 bytes, checksum: 3e2c3d43b62b9fa0edea517213c63a12 (MD5) Previous issue date: 2018-02-26 / CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Entender e controlar o movimento de parede de domínio em nanofios é extremamente im-portante para o desenvolvimento de novas tecnologias para a aplicação em dispositivos de ar-mazenamento de dados. É conhecido que defeitos como entalhes ("notches") em nanofios são úteis para fixar paredes de domínio. No entanto, a intensidade de potencial de aprisionamento gerado com esse tipo de defeito é muito forte, e para desprender a parede de domínio é ne-cessário aplicar uma densidade de corrente muito elevada. Entretanto, pode-se criar armadilhas para paredes de domínios variando localmente propriedades magnéticas do nanofio, tais como: tais como constante de troca, magnetização de saturação, constante de anisotropia, parâmetro de amortecimento de Gilbert. Definimos essas regiões como impurezas magnéticas por ter propriedades magnéticas diferentes do nanofio. Neste trabalho, realizamos simulações micro-magnéticas para investigar a dinâmica de uma parede de domínio transversal (PDT) aprisionada em um defeito magnético usando pulsos de corrente elétrica polarizada em spin. Afim de criar armadilhas de aprisionamento para a PDT, consideramos um modelo de impureza magnética variando localmente a constante de troca. Ao ajustar o potencial de interação entre impure-zas magnéticas e uma PDT, verificamos que pulsos de corrente de baixa intensidade e de curta duração são capazes de desprender a PDT. Por fim, demonstramos que é possível controlar a posição de uma PDT aplicando pulsos de corrente sequenciais em uma nanofita contendo uma distribuição linear de impurezas magnéticas igualmente espaçadas. / Understand and control the domain wall movement in nanowires is extremely important for the development of new technologies for an application in data storage devices. It is known that defect as notches in nanowires are useful to pinning domain walls. Nevertheless, the pinning potential intensity generated by this type of defect is strong, and for depinning the domain wall it is necessary to apply a high current density. However, it is possible to create traps for domains walls by locally varying magnetic properties of the nanowire, such as: the exchange constant, saturation magnetization, anisotropy constant, Gilbert damping parameters. We define those regions as magnetic impurities once their magnetic properties differ from the nanowire proper-ties. In this study, we realized micromagnetic simulations in order to investigate the dynamics of a transverse domain wall (TDW) trapped in a magnetic defect using electric current pulses of spin-polarized. In order to create traps to TDW pinning, we have modeled the magnetic impurities by varying the exchange constant locally. When we adjusted the interaction poten-tial between the magnetic impurities and the nanowire we showed that low intensity and short duration current pulses are capable of depinning the TDW. At last, we demonstrated that it is possible to control the TDW position applying sequential current pulses in a nanowire planar containing a linear distribution of magnetic impurities equally distributed.

γ-TiAl based alloys have attracted considerable research interest in the past few decades and have gained niche high temperature applications in aero-engines and automobiles. As high temperature structural materials, these alloys require stable microstructures. This thesis aims at addressing knowledge gaps in the understanding of microstructural stability in two technologically important γ-TiAl based alloys in different microstructures, viz. fully lamellar (FL) and duplex. Creep and exposure tests were complemented with a variety of microstructural characterization tools (SEM, EBSD, TEM, XRD). Density functional theory based calculations were also performed to further the understanding of stability of phases. In the first part of the thesis, microstructural stability of a FL microstructure was studied under creep and high temperature exposure conditions. An aim of these studies was to probe the effect of stress orientation with respect to lamellar plates on microstructural changes during primary creep. It was observed that retention of excess α2 resulted in an unstable microstructure and so under stress and temperature, excess α2 was lost. However, depending on stress orientation, the sequence of precipitates formed was different. In particular, for certain stress orientations, the formation of the non-equilibrium C14 phase was observed. The stress dependence of microstructural evolution was found to be stem from internal stresses due to lattice misfit and elastic moduli mismatch between α2 and γ. In the second part of this thesis, microstructural stability of a duplex alloy was probed, with an emphasis on understanding mechanisms that lead to tertiary creep. The as-extruded microstructure consisted of bands of equiaxed grains and lamellar grains. During creep, loss of lamellar grains was observed and this was attended by kinking of laths and formation of dynamically recrystallized equiaxed grains. Significant dislocation activity was seen in both lamellar and equiaxed grains at all stages of creep. Initially, dislocation activity leads to strengthening and primary creep behavior, but at later stages, it triggers dynamic recrystallization. Dynamic recrystallization was found to be the rate controlling creep mechanism. Accelerating creep behavior was due to strain localization during the constant load tensile test resulting from microstructural instabilities such as kinking.

No description available.

No description available.

<p>Doktorska disertacija je posvećena raznim klasama uop&scaron;tenih stohastičkih procesa i njihovim primenama na re&scaron;avanje singularnih stohastičkih parcijalnih diferencijalnih jednačina. U osnovi, disertacija se može podeliti na dva dela. Prvi deo disertacije (Glava 2) je posvećen strukturnoj karakterizaciji uop&scaron;tenih stohastičkih procesa u vidu haos ekspanzije i integralne reprezentacije. Drugi deo disertacije (Glava 3) čini primena dobijenih rezultata na re&middot;savanje stohastičkog Dirihleovog problema u kojem se množenje modelira Vikovim proizvodom, a koefcijenti eliptičnog diferencijalnog operatora su Kolomboovi uop&scaron;teni stohastički procesi.</p> / <p>Subject of the dissertation are various classes of generalized<br />stochastic processes and their applications to solving singular stochastic<br />partial di&reg;erential equations. Basically, the dissertation can be divided into<br />two parts. The &macr;rst part (Chapter 2) is devoted to structural characteri-<br />zations of generalized random processes in terms of chaos expansions and<br />integral representations. The second part of the dissertation (Chapter 3)<br />involves applications of the obtained results to solving a stochastic Dirichlet<br />problem, where multiplication is modeled by the Wick product, and the<br />coe&plusmn;cients of the elliptic di&reg;erential operator are Colombeau generalized<br />random processes.</p>