Este trabalho analisa o efeito da descarbonetação nas perdas magnéticas de aços elétricos semiprocessados, após recozimento final, descarbonetante e/ou não-descarbonetante. Neste trabalho foi utilizado um aço de baixo carbono (600ppm de C) encruado a 4-6% de deformação, tipo COSCORE 55O. Foi notado que o recozimento descarbonetante reduz rapidamente (poucos minutos de tratamento térmico) o teor de carbono do aço a níveis baixos (abaixo de 100ppm de C), reduzindo também as Perdas magnéticas totais (abaixo de 10W/Kg). Verifica-se que recozimentos de 20 e 40 minutos são tempos suficientes para produzir aços com baixas Perdas e baixo teor de C. É mostrado também que recozimento descarbonetante influencia na recristalização de aços carbono encruado. Verificou-se que, durante recozimento descarbonetante, o espaçamento entre as lâminas influenciou a microestrutura e as perdas magnéticas do material. A análise de Textura cristalográfica do material revela que quanto maior o nível de umidade do ensaio, maior a redução da intensidade de fibra Gama, (111)//DN, e aumento da intensidade de textura cristalográfica Goss, ou seja, grãos com orientação cristalográfica, (110)// de grande intensidade é obtido. / This work analyzes the effects of decarburizing annealing on the magnetic, microstructure and texture properties of semiprocessed electrical steels after annealing. A rolles low-carbon electrical steel (0,06%wt/wt Carbon) sheet was used in the experiments. It was verified that decarburizing annealings decrease quickly carbon content (after few minutes of thermal treatment) to levels lower than 100ppm, and after annealing the magnetic losses fastly decreases until below 10W/Kg. It was seen that decarburizing annealings for 20 and 40 minutes are enough to produce low magnetic losses and low carbon content steels. The annealings resulted in low magnetic losses steels whenever microstructure recrystallization has occurred, associated with decarburization. It was noticed that, during decarburizing annealing, the spacing between sheets affected the microstructure and magnetic losses of the material. Crystallographic texture analysis of material reveals that the bigger the annealing humidity, Gama fiber, (111)//DN, decreases and Goss texture, (110)//, increases.

by Lui Kai Man, Raymond. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1993. / Includes bibliographical references (leaves 221-225). / Acknow1edgements / Abstract --- p.i / Table of Contents --- p.ii / Chapter Chapter 1 --- Introduction --- p.1 / Chapter Chapter 2 --- Sample Preparation --- p.12 / Chapter A. --- Introduction --- p.12 / Chapter B. --- The Working Systems --- p.12 / Chapter C. --- Sample Preparation --- p.14 / Chapter C.1 --- The Method Of Reactive Evaporation --- p.14 / Chapter C.2 --- The Method Of Posthydrogenation --- p.15 / Chapter D. --- The Substrates --- p.16 / Chapter Chapter 3 --- "Electrical Conductivities, Thermal and Optical Stability Experiments" --- p.21 / Chapter A. --- Introduction --- p.21 / Chapter B. --- Theory --- p.22 / Chapter B.1 --- Electronic Transport In Amorphous Semiconductor --- p.22 / Chapter B.2 --- dc Electrical Conductivity in Davis-Mott Model --- p.23 / Chapter B.3 --- Photoconductivity --- p.27 / Chapter B.4 --- Staebler-Wronski Effect --- p.28 / Chapter C. --- Experimental Method --- p.29 / Chapter C.1 --- Dark And Photo Conductivities Measurements --- p.29 / Chapter C.2 --- Optical Stability Measurement --- p.32 / Chapter C.3 --- Thermal Stability Measurement --- p.32 / Chapter D. --- Results --- p.34 / Chapter D.1 --- Reactively Evaporated Samples --- p.34 / Chapter D.2 --- Temperature Dependence Of Conductivities --- p.34 / Chapter D.3 --- Optical Stability Measurement --- p.35 / Chapter D.4 --- Thermal Stability Measurement --- p.36 / Chapter E. --- Discussions --- p.36 / Chapter E.1 --- Electrical Properties Of Reactively Evaporated a-Si:H --- p.36 / Chapter E.2 --- A Comparative Study Between Reactive Evaporated Samples With Those From Other Reactive Deposition Techniques And Glow-Discharge Process --- p.37 / Chapter F. --- Conclusions --- p.38 / Chapter Chapter 4 --- Infrared Absorption Experiment --- p.63 / Chapter A. --- Introduction --- p.63 / Chapter A.1 --- General Description --- p.63 / Chapter A.2 --- Types Of Atomic Vibrations --- p.64 / Chapter A.3 --- Infrared Spectroscopy Of a-Si:H --- p.64 / Chapter A.4 --- Effect Of Substrate Temperature On Bonding Configuration --- p.65 / Chapter B. --- Experimental Method --- p.66 / Chapter C. --- Results --- p.66 / Chapter D. --- Discussions --- p.67 / Chapter D.1 --- Identification Of The Two Absorption Bands --- p.67 / Chapter D.2 --- Effect Of Substrate Temperature --- p.68 / Chapter E. --- Conclusions --- p.70 / Chapter Chapter 5 --- Electron Spin Resonance Experiment --- p.82 / Chapter A. --- Introduction --- p.82 / Chapter B. --- Theory --- p.85 / Chapter B. 1 --- The Absorption Process --- p.85 / Chapter B. 2 --- The Relaxation Process --- p.86 / Chapter C. --- Experimental Method --- p.90 / Chapter D. --- Results --- p.92 / Chapter E. --- Discussions --- p.93 / Chapter F. --- Conclusions --- p.96 / Chapter Chapter 6 --- Optical Absorption Experiment --- p.114 / Chapter A. --- Introduction --- p.114 / Chapter B. --- Theory On Optical Transitions Within Amorphous Materials --- p.114 / Chapter B.1 --- General Descriptions --- p.114 / Chapter B.2 --- Band Models For Optical Absorptions In An Amorphous Semiconductor --- p.116 / Chapter C. --- Experimental Method --- p.121 / Chapter E. --- Analysis --- p.123 / Chapter E.1 --- Band Model --- p.123 / Chapter E.2 --- Deconvolution Of Absorption Spectrum --- p.124 / Chapter F. --- Discussions --- p.131 / Chapter G. --- Conclusions --- p.133 / Appendix A --- p.134 / Chapter A.1 --- An Outline On The Theoretical And Experimental Aspects Of PDS --- p.134 / Chapter Chapter 7 --- Recrystallization Of Amorphous Germanium By Rapid Thermal Annealing --- p.165 / Chapter A. --- Introduction --- p.165 / Chapter B. --- Theory --- p.166 / Chapter B.1 --- Recrystallization Of Amorphous Germanium --- p.166 / Chapter B.2 --- Nucleation And Growth - Isothermal Transformation --- p.167 / Chapter B.3 --- The Structure Of Polycrystalline Aggregates By X-ray Analysis --- p.170 / Chapter C. --- Experimental Set-ups --- p.172 / Chapter C. 1 --- The Rapid Thermal Processing Unit --- p.172 / Chapter C. 2 --- The Conventional Furnace --- p.175 / Chapter C. 3 --- The X-ray Diffractometer --- p.175 / Chapter C. 4 --- Electrical Conductivity Measurements --- p.176 / Chapter D. --- Experimental Method --- p.177 / Chapter D.1 --- The Samples --- p.177 / Chapter D.2 --- The Experiments --- p.177 / Chapter E. --- Results And Discussions --- p.178 / Chapter F. --- Conclusions --- p.185 / Appendix A --- p.216 / Chapter Chapter 8 --- Conclusions --- p.217 / Chapter A. --- Conclusions --- p.217 / Chapter B. --- Suggestions On Improvement And Further Development Of The Present Systems --- p.219 / References --- p.221

O presente trabalho tem como objetivo mostrar a influência do recozimento na recuperação e recristalização de tiras de aço baixo carbono dobradas por deformação a frio. Muitas indústrias que produzem peças a partir de dobramento a frio, buscam constantemente garantir a qualidade de seus produtos. Isto se torna um desafio a partir do momento que se considera a diversidade do formato das dobras exigidas. Através de observações práticas, o que se vê é que, com o objetivo de facilitar o processo, muitos profissionais são induzidos a acreditar que simplesmente aquecendo o material, o trabalho será facilitado e garantirá a qualidade do produto final. Assim, independente do tipo do aço e/ou nível de encruamento, os parâmetros de temperatura utilizados são determinados, na sua grande maioria, de forma empírica, sem critérios estabelecidos, ou seja, em muitos casos, os valores de temperatura tendem a ser os mesmos. Como a grande maioria de peças produzidas na indústria submetida a deformação é em aço baixo carbono, este foi escolhido como material para a fabricação das amostras utilizadas no experimento. Estas amostras foram submetidas a diversos graus de dobramento a frio e aplicação de recozimento para recristalização com variação controlada dos parâmetros. Através da intercomparação das amostras e com aplicação de diversos ensaios foram caracterizados a dureza, estrutura metalográfica, tamanho médio do precipitado, bem como a correlação entre as condições de recozimento versus o nível de recuperação do encruamento. Através dos dados obtidos, observou-se a importância de definir de forma científica os parâmetros de aquecimento para a recristalização, sob pena de prejudicar as características das peças. / This work aims to show the influence of annealing on the recovery and recrystallization of low carbon steel strips bent by cold forming. Many industries that produce parts from cold bending, constantly seek to ensure the quality of their products. This becomes a challenge from the moment that one considers the diversity of the shape of folds required. Through practical observation, we can see that, in order to facilitate the process, many professionals are led to believe that simply heating the material, the work will be facilitated and ensure final product quality. Thus, regardless of the type of steel and / or level of work hardening, the parameters used in temperature are determined, mostly, empirically, without established criteria, ie, in most cases, the temperature values tend to be same. As the vast majority of parts produced in the industry is subjected to deformation in steel low carbon, this was chosen as material for the manufacture of the samples used in the experiment. These samples were subjected to various degrees of cold bending and applying for recrystallization annealing with controlled variation of parameters. By intercomparison of samples and application of various tests were characterized hardness, metallographic structure, average size of the precipitate, and the correlation between the annealing conditions versus the level of recovery of work hardening. Through the data obtained it observed the importance of defining the parameters in a scientific way of heating for recrystallization, failing to affect the characteristics of components.

A liga Cu-30%Zn, conhecida como latão 70/30, possui diversas aplicações comerciais, tais como cartuchos para munição e conectores elétricos. Na produção de chapas e barras dessa liga no formato e nas propriedades almejadas para a aplicação final, comumente utiliza-se de tratamento térmicos para restauração das propriedades mecânicas, chamados de recozimento. Em particular, o efeito de solutos em solução sólida é um fator determinante para o comportamento de ligas metálicas durante o recozimento e deve ganhar importância com a tendência industrial de utilização de matéria-prima reciclada, gerando adições inadvertidas de elementos químicos que estarão presentes como solutos em solução sólida. Este trabalho levanta dados referentes a alterações no comportamento do latão 70/30 diante do tratamento de recozimento causados por teores residuais de ferro. Com base na revisão da literatura, propôs-se a metodologia de tratamentos interrompidos em dilatômetro para o estudo do recozimento de três materiais: CuZn-1Fe (0,0126%Fe), CuZn-4Fe (0,0417%Fe) e CuZn-6Fe (0,0599%Fe). Duas taxas de aquecimento foram utilizadas: 10 ºC/min e 1000 ºC/min. As propriedades mecânicas foram avaliadas em termos de microdureza Vickers e a fração recristalizada determinada por metalografia quantitativa. As análises microestruturais mostraram que a recristalização inicia-se preferencialmente em bandas de cisalhamento. A análise conjugada dos resultados mostra a seguinte faixa de temperatura de recristalização: taxa de aquecimento de 10 ºC/min - 295ºC a 345ºC; taxa de 1000 ºC/min - 365ºC a 445ºC, sendo que o teor residual de ferro não causa alterações neste comportamento. A análise das amostras recozidas isotermicamente a 500ºC e a 600ºC mostram uma tendência à formação de uma microestrutura heterogênea, possivelmente pela evolução da microestrutura de recristalização, que dá origem a grãos grosseiros em sua etapa final. A amostra com 599 ppm de Fe não apresentou evolução do tamanho de grão a 500ºC. Resultados de MET não mostraram a formação de partículas dispersas, enquanto análises de DSC revelaram um pico prévio à recristalização, identificado como a formação de uma atmosfera de Cottrell, sendo esta atrasada pela presença de ferro em solução sólida. / The Cu-30%Zn alloy, known as 70/30 brass, has many commercial applications like ammunition cartridge and electronic connectors. To properly produce strips and bars of this material it is necessary to realize a heating treatment called annealing, which aims on recovering the mechanical properties of the material. The effect of solute atoms is a high important factor to determine the material behavior during annealing. This issue is getting even more importance to industrial applications, due to the increase of the recycle of waste products. These wastes often contaminate the molten metal with foreign elements which may be in solid solution after solidification. This work aims to assess changes in behavior of the 70/30 brass during annealing due to iron in residual content. Based on literature, it was proposed a methodology which takes advantages of interrupted annealing in dilatomer and isothermal annealing for three different iron residual content: CuZn- 1Fe (0,0126%Fe), CuZn-4Fe (0,0417%Fe) and CuZn-6Fe (0,0599%Fe). Two heating rates were used: 10 ºC/min e 1000 ºC/min. The mechanical properties were evaluated by Vickers microhardness and the recrystallized fraction was determined by quantitative microscopy. The microstructural analysis showed that the recrystallization starts preferentially on shear bands. The results from different techniques showed that the recrystallization temperature range is 295ºC to 345ºC when the heating rate was 10 ºC/min and 365º to 445ºC for 1000 ºC/min. There were no evidences of changing the brass behavior during annealing with the residual iron content. The isothermal annealed samples demonstrated a tendency for the formation of a heterogeneous microstructure at both 500ºC or 600ºC, which can be due to the recrystallization microstructure evolution. In the final stage, bigger recrystallized grains are formed inside cold worked grains. Also, the material with 599 ppm Fe did not change its grain size during annealing at 500ºC. MET results did not demonstrate the occurrence of dispersed iron particles. DSC analysis showed a peak prior to recrystallization, which was identified as the formation of a Cottrell atmosphere in all samples. The iron solute seems to detain its occurrence.

Hematite (α-Fe2O3) is a common, naturally occurring iron oxide, found throughout the earth's crust and atmosphere. Hematite is of interest to the scientific community because it is able to incite a reaction that produces hydrogen gas (H2), which is a form of clean energy (Bora et al., 2013). The composition of hematite in nature is also used to make inferences about conditions on early earth's surface (Guo et al., 2013). Hematite is useful for clean energy production and as an environmental indicator partly because of its apparent stability. However, some evidence suggests that hematite might not be as stable as previously thought. Many iron oxides undergo Fe atom exchange when they come into contact with aqueous Fe(II), as often occurs in nature (Pedersen et al., 2005, Jones et al., 2009, Gorski et al., 2012, Handler et al., 2009). This atom exchange can result in elements and nutrients being taken up or released from the iron oxides as they recrystallize (Frierdich & Catalano, 2012, Cwiertny et al., 2008, Boland et al., 2014). Although atom exchange has not been directly shown in hematite, it has been demonstrated that trace metals are released from hematite in the presence of aqueous Fe(II), implying that exchange may be occurring (Frierdich et al., 2011). Here, we directly demonstrate Fe atom exchange between hematite and aqueous Fe(II). This work provides knowledge concerning the surface chemistry of hematite that has important implications for clean energy production and the environment.

O crescimento dos núcleos de recristalização em direção à matriz deformada geralmente não ocorre de forma isotrópica. Perturbações locais na velocidade de migração dos contornos levam ao surgimento de protrusões. Trata-se de um aspecto importante na recristalização, porém ainda pouco explorado na literatura, especialmente quanto ao entendimento de quais mecanismos microestruturais explicam sua formação. O objetivo desta Tese de Doutorado é estudar a formação das protrusões na recristalização do nióbio oligocristalino. Para tal, uma chapa de nióbio com grãos bastante grosseiros foi retirada da seção longitudinal de um lingote fundido por feixe eletrônico. Foram selecionados de forma aleatória cinco grãos (A, B, C, D e E) para se avaliar eventuais efeitos de orientação na formação de protrusões. A chapa foi laminada a frio com vários passes até 50% de redução de espessura. Na sequência, a chapa foi dividida em duas partes, sendo que na primeira foi dado prosseguimento na laminação até atingir 70% de redução de espessura, enquanto que a segunda sofreu rotação de 90° em relação à direção de laminação inicial. As amostras foram recozidas entre 800 e 1200°C por 60 min. O grão E LC recristalizou em todas temperaturas estudadas, e o LD nas temperaturas entre 1000 e 1200°C. O grão A LC recristalizou em todas temperaturas, exceto em 1000°C, e LD recristalizou apenas em 1200°C. O grão C LC recristalizou apenas em 1200°C. Os grãos B e D não recristalizaram em nenhuma temperatura. Não foi possível identificar e associar diferenças significativas quanto ao potencial termodinâmico para recristalização à frente dos contornos com a formação das protrusões. Medidas de EBSD em 3D obtidas por seccionamento serial mostraram diferenças importantes do ponto de vista energético entre o contorno formado entre a protrusão e a matriz recuperada e o contorno entre a lateral do grão recristalizado e a matriz recuperada. O primeiro par é mais móvel, o que explica a morfologia alongada das protrusões. / The growth of recrystallization nuclei towards the deformed matrix generally does not occur in an isotropic manner. Local disturbances in the migration along grain boundaries lead to the formation of protrusions. This is an important aspect in recrystallization, but still less explored in the literature, especially regarding the understanding of which microstructural mechanisms explain its formation. This Thesis aims at to study the formation of protrusions during recrystallization of a niobium oligocrystal. A coarse-grained niobium plate was cut out from the longitudinal section of an electron-beam cast ingot. Five coarse grains (A, B, C, D and E) were randomly selected for this study to evaluate possible orientation effects on protrusion formation. The plate was cold rolled with several passes up to 50% thickness reduction. The sheet was cut into two parts. The former was straight rolled until 70% thickness reduction while the latter was rotated 90° with respect to the initial rolling direction. The samples were annealed at 800 to 1200°C for 60 min. Grain E CR recrystallized at all temperatures studied, and SR at temperatures between 1000 and 1200°C. Grain A CR recrystallized at all temperatures except 1000°C, and SR recrystallized only at 1200°C. Grain C CR recrystallized only at 1200°C. Grains B and D did not recrystallize at any temperature. It was not possible to identify and to associate significant differences of the thermodynamic potential for recrystallization ahead of the boundaries with the formation of protrusions. 3D EBSD measurements obtained by serial sectioning showed important differences regarding grain boundary energy between the boundary formed between the protrusion and the recovered matrix and the boundary formed by the lateral part of the recrystallized grain and the recovered matrix. The first pair is more mobile, which explains the elongated morphology of the protrusions.

Cryopresevation is the process of cooling biological materials to low sub-zero temperatures for storage purposes. Numerous medical and technical applications, such as hematopoeitic stem cell transplantation and sperm banking, sometimes require the use of cryopreserved cells. Cryopreservation, however, can induce cell injury and reduce the yields of viable functional cells. Ice recrystallization is a mechanism of cryopreservation injury, but is rarely addressd in strategies to optimize cell cryopreservation. The results from this thesis demonstrate an association between the potency of carbohydrate-mediated ice recrystallization inhibition used in the cryopreservation of umbilical cord blood and recovery of viable non-apoptotic cells and hematopoietic progenitor function. Furthermore, increased numbers of apoptotic cells in hematopoeitic stem cell grafts were associated with reduced hematopoietic function and delayed hematopoietic recovery in patients undergoing blood stem cell transplantation. These findings provide a basis for pursuing further studies assessing ice recrystallization inhibition as a strategy for improving cell cryopreservation.

16 samples of increasing metamorphic grade from the Ballachulish Igneous Complex and Aureole, located in the west of Scotland, were studied in order to analyze the sulfide mineralogy and to what extent they were affected by contact metamorphism. The samples were collected from two lithologies, the Creran Succession and the Ballachulish Slate lithology, as well as from the igneous complex. The sulfides of main interest in the samples are pyrite and pyrrhotite. At the onset of contact metamorphism, pyrite disappears while pyrrhotite gets more abundant as metamorphic grade increases. Pyrrhotite also undergoes multiple changes such as 1) elongation and thinning of the grains, 2) development of 120° grain-boundaries, 3) development of pyrite-zones within the pyrrhotite and 4) the decomposition of pyrrhotite and alignment of pyrite along its grain-boundaries at high temperature. The elongation of the grains occurs in both the Creran Succession and the Ballachulish Slate. The rest of the textures, however, can only be found in the Creran Succession. The two lithologies differ by the high graphite content in the Ballachulish Slate. The elongated grains as well as the pyrite inclusions in the pyrrhotite both are strong evidence of recrystallization. The absence of pyrite in the Ballachulish Slate was most probably caused by the buffering properties of the graphite-rich fluid in these rocks, causing more reducing conditions. There is evidence against a heavy, pervasive fluid flow through the aureole. However, the inner contact zone seems to have been affected by a more pronounced fluid flow. This could have been caused by the metamorphic fluid working in conjunction with fluids released from the intrusion. Regarding the mobility of S in the aureole, no strong evidence could be found, other than the decomposition of pyrrhotite grain-boundaries in the high-grade metamorphic samples.

Cryopresevation is the process of cooling biological materials to low sub-zero temperatures for storage purposes. Numerous medical and technical applications, such as hematopoeitic stem cell transplantation and sperm banking, sometimes require the use of cryopreserved cells. Cryopreservation, however, can induce cell injury and reduce the yields of viable functional cells. Ice recrystallization is a mechanism of cryopreservation injury, but is rarely addressd in strategies to optimize cell cryopreservation. The results from this thesis demonstrate an association between the potency of carbohydrate-mediated ice recrystallization inhibition used in the cryopreservation of umbilical cord blood and recovery of viable non-apoptotic cells and hematopoietic progenitor function. Furthermore, increased numbers of apoptotic cells in hematopoeitic stem cell grafts were associated with reduced hematopoietic function and delayed hematopoietic recovery in patients undergoing blood stem cell transplantation. These findings provide a basis for pursuing further studies assessing ice recrystallization inhibition as a strategy for improving cell cryopreservation.

none