Made available in DSpace on 2015-04-14T13:35:30Z (GMT). No. of bitstreams: 1 438171.pdf: 6920524 bytes, checksum: f5e5c6d7e177dfd60f3b3303552cc797 (MD5) Previous issue date: 2012-03-28 / OBJECTIVE : To evaluate and compare the effect of using Platelet-Rich Plasma (PRP) and Platelet-Rich Fibrin (PRF) in the repair of the Achilles tendon (TA) of rats. MATERIAL and METHODS : Forty-eight adult male rats randomized into three experimental groups: PRP, PRF and Control (saline 0.9%). A 3 cm longitudinal incision was made in the right leg of each rat in order to expose the TA. Later, it was a break in the same horizontal, and the repair performed with suture Kessler-type, when the sequence was applied 50 &#956;L of the treatment in question. After 14 and 28 days postoperatively, the targeted part of the TA was removed, thus initializing the histological processing (Hematoxylin/Eosin; Sirius Red) to obtain results. The data obtained were expressed at 5% significance level (p <0.05) with mean ? SE. RESULTS : When comparing the three groups together, as to time and area of collagen type I and III, only statistical difference between the control group (16.22%) and the PRP group (37.16%) at 14 days after the treatment, no statistically significant difference was observed in the other groups. In the same way, when compared within groups of 14 and 28 days, the PRF group showed a significant difference for collagen I (27.76% and 47.74%) and III (66.94% and 46%) respectively. Control group showed significant difference in collagen type I (14.20% and 40.90%), not observed any significant difference in the PRP group. When evaluated on Hematoxylin/Eosin staining, PRP and control were similar in the times studied, differing only in the presence of hemorrhage, that was more expressed in the PRP group. Already the group PRF has shown to be more organized, especially in time of 28 days compared to the other two treatments. CONCLUSION : The data from this study suggest that the Platelet-Rich Fibrin tends to promote the accelerated regeneration of the Achilles tendon of rats, bringing promising prospects for future use in the clinic. / OBJETIVO : Avaliar e comparar o efeito do uso de plasma rico em plaquetas (PRP) e fibrina rica em plaquetas (PRF) no reparo do tend?o de Aquiles (TA) de ratos. MATERIAL e M?TODOS : Foram utilizados 48 ratos machos adultos distribu?dos randomicamente em tr?s grupos experimentais: PRP, PRF e Controle (solu??o salina 0,9%). Uma incis?o longitudinal de 3 cm foi realizada na perna direita de cada rato, a fim de expor o TA. Posteriormente, fez-se uma ruptura horizontal no mesmo, sendo a repara??o realizada com sutura do tipo Kessler, onde na seq??ncia foi aplicado 50 &#956;L do tratamento em quest?o. Passados 14 e 28 dias p?s- operat?rio, a parte segmentada do TA foi removida, inicializando assim o processo histol?gico (Hematoxilina/Eosina; Picros?rius Red) para obten??o de resultados. Os dados obtidos foram expressos ao n?vel de 5% de signific?ncia (p < 0.05) com m?dia ? EP. RESULTADOS : Ao comparar os tr?s grupos entre si, quanto ao tempo e ?rea de col?geno tipo I e III, houve diferen?a estat?stica somente entre o grupo Controle (16.22%) e o grupo PRP (37.16%) aos 14 dias ap?s o tratamento, n?o sendo observada diferen?a estatisticamente significativa nos outros grupos. Da mesma forma, quando comparados intra-grupos em 14 e 28 dias, o grupo PRF apresentou diferen?a significativa para col?geno I (27.76% e 47.74%) e III (66.94% e 46%) respectivamente. Grupo Controle demonstrou diferen?a significativa para col?geno tipo I (14.20% e 40.90%), n?o sendo observada qualquer diferen?a significativa no grupo PRP. Quando avaliados na colora??o Hematoxilina e Eosina, PRP e Controle apresentaram-se semelhantes nos tempos avaliados, diferindo apenas quanto a presen?a de hemorragia, que foi mais expressa no grupo PRP. J? o grupo PRF demonstrou-se mais organizado, principalmente no tempo de 28 dias quando comparado aos outros dois tratamentos. CONCLUS?O : Os dados obtidos neste trabalho sugerem que a Fibrina Rica em Plaquetas tem tend?ncia a promover a regenera??o acelerada do tend?o de Aquiles de ratos, trazendo perspectivas promissoras para futuras utiliza??es na cl?nica.

This thesis study is concerned with genetical investigation of Balikesir Balya Pb-Zn mineralization through the mineralogic-petrographic and geochemical examination of the core samples obtained from a total of 9 holes drilled by EczacibaSi ESAN Madencilik. The Pb-Zn mineralization in Balya is mainly of vein-type. Wall rocks hosting mineralizations are dacite, dacite porphyry and microdiorite. Major types of alteration are silicification, carbonatization and calc-silicate alteration, each of which is further subdivided into early and late stages and overprinted by argillic alteration of probable supergene origin. The ore minerals are mainly Zn- and Pb-sulphides and are hosted by the rocks with late calc-silicate alteration that underwent pervasive late silicification and late carbonatization. Sulfide mineralization is spatially and temporally associated with the late silicification and carbonatization stages. Lateral-vertical correlation of drill logs suggest that thickness of the ore zone tends to decrease towards north. The volcanic rocks hosting the mineralization have calc-alkaline nature. Major, trace and rare earth element (REE) geochemistry suggests either crustal contamination or subduction signature in the mantle source of the volcanics. Multi element patterns and discrimination diagrams collectively point to a post-collisional setting for their generation. Alteration geochemistry reveals that Fe2O3 and CaO are enriched during calc-silicate alteration in contrast to depletion of SiO2. Al2O3 and TiO2 are almost constant during late calc-silicate alteration. Enrichment of Fe2O3 and Na2O, and depletion of K2O characterize the silicified zones. Carbonatization is accompanied by strong enrichment of CaO and depletion of SiO2, Al2O3 and K2O.

In the Central Anatolian Crystalline Complex (CACC) the Late Cretaceous post-collisional granitic magmatism is followed by Eocene extension, resulting in formation of roughly E-W trending transtensional basins. Formation of these basins was accompanied by calc- alkaline- mildly alkaline volcanism. The volcanic rocks, mainly subaques lava flows and subareal domes are concentrated along these basins and associated with Middle Eocene (Bartonian) Mucur Formation. They are basic to intermediate and are classified as basalt, basaltic andesite and rarely alkali basalt and trachy-andesite. All studied samples are strongly and variably LREE enriched relative to chondrite with the (La/Sm)N ratio of 2.26- to 6.17. They have negative Nb-Ta and Ti anomalies in the primitive mantle normalized diagram, and are characterized by low Nb/La (0.21 to 0.62), Ce/Pb (3.70-34.90) and Nb/U ratios (1.11-30), which may indicate an interaction with the Late Cretaceous granitic host rocks in the course of their ascent. The volcanic rocks display similar but variable ranges of Sr, Nd and Pb isotope values. Relatively high values of &epsilon / Nd (0.53 to 4.33) indicate an isotopically depleted mantle source. Combined trace element and isotope compositions of the Eocene samples suggest that they were derived from a heterogeneous lithospheric mantle source that had been metasomatized by subduction related agents such as fluids and/or melts during a previous geodynamic event. Geochemistry and geotectonic setting point out that lithospheric delamination was the most likely mechanism to generate these calc-alkaline to mildly alkaline volcanic rocks in the CACC.

Reproduction de : Thèse de doctorat : Sciences des matériaux : Lille 1 : 2004. / N° d'ordre (Lille 1) : 3532. Résumé en français et en anglais. Titre provenant de la page de titre du document numérisé. Bibliogr. p. 171-176.

Submitted by Rodrigo Martins Cruz (rodrigo.cruz@ufvjm.edu.br) on 2015-02-27T13:30:35Z No. of bitstreams: 5 45.pdf: 345535 bytes, checksum: c3649a3cfc01189e92c6e9258cbcfc4a (MD5) license_url: 52 bytes, checksum: 3d480ae6c91e310daba2020f8787d6f9 (MD5) license_text: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) license_rdf: 23898 bytes, checksum: e363e809996cf46ada20da1accfcd9c7 (MD5) license.txt: 2109 bytes, checksum: aa477231e840f304454a16eb85a9235f (MD5) / Approved for entry into archive by Rodrigo Martins Cruz (rodrigo.cruz@ufvjm.edu.br) on 2015-02-27T18:12:58Z (GMT) No. of bitstreams: 5 45.pdf: 345535 bytes, checksum: c3649a3cfc01189e92c6e9258cbcfc4a (MD5) license_url: 52 bytes, checksum: 3d480ae6c91e310daba2020f8787d6f9 (MD5) license_text: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) license_rdf: 23898 bytes, checksum: e363e809996cf46ada20da1accfcd9c7 (MD5) license.txt: 2109 bytes, checksum: aa477231e840f304454a16eb85a9235f (MD5) / Made available in DSpace on 2015-02-27T18:12:58Z (GMT). No. of bitstreams: 5 45.pdf: 345535 bytes, checksum: c3649a3cfc01189e92c6e9258cbcfc4a (MD5) license_url: 52 bytes, checksum: 3d480ae6c91e310daba2020f8787d6f9 (MD5) license_text: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) license_rdf: 23898 bytes, checksum: e363e809996cf46ada20da1accfcd9c7 (MD5) license.txt: 2109 bytes, checksum: aa477231e840f304454a16eb85a9235f (MD5) Previous issue date: 2013 / Conselho Nacional de Desenvolvimento Cient?fico e Tecnol?gico (CNPq) / Funda??o de Amparo ? Pesquisa do estado de Minas Gerais (FAPEMIG) / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior (Capes) / O Brasil possui imensas ?reas de pastagens e a esp?cie mais cultivada ? a Brachiaria brizantha. O controle das plantas daninhas nestas ?reas ? realizado predominantemente pelo uso de herbicidas com longo per?odo residual, destacando-se o picloram. Este ? utilizado no controle de plantas daninhas de folhas largas perenes e tem sido intensamente pesquisado em fun??o da alta meia vida nos solos, sendo sua persist?ncia dependente do clima e atributos ed?ficos, como textura e pH. Objetivou-se com este trabalho avaliar o desenvolvimento e o potencial remediador de B. brizantha em solo contaminado com picloram em diferentes n?veis de pH. O delineamento experimental utilizado foi em blocos casualizados, com quatro repeti??es e com faixa de pH variando entre 4,5 e 5,6. Cultivou-se a forrageira at? a flora??o, quando se determinou a massa da mat?ria seca dos componentes da planta e posteriormente, cultivou-se plantas de pepino como indicadores da presen?a do herbicida. O picloram causou redu??o no ac?mulo da massa da mat?ria seca total das plantas de B. brizantha, em consequ?ncia do efeito negativo sobre a produ??o de ra?zes, independente do pH do solo. Nas folhas o herbicida promoveu redu??o na massa da mat?ria seca em solo com maior pH. Nos tratamentos com maior valor de pH, na profundidade de 35 cm, constatou-se maior ac?mulo de massa da mat?ria seca de ra?zes quando n?o se aplicou o herbicida, indicando que em solos menos ?cidos o herbicida tende a prejudicar o desenvolvimento de ra?zes da forrageira em maiores profundidades. A B. brizantha reduziu a concentra??o de picloram na camada superficial de solo, o que pode ser atribu?do a sua capacidade de degradar o herbicida e tamb?m ao fato desta absorver e exsudar o herbicida ao longo das camadas de solo. Observou-se tamb?m que em solos com maiores valores de pH o herbicida tem maior potencial de lixivia??o, principalmente quando n?o cultivado com B. brizantha. Solos com menores valores de pH tendem ? maior sor??o do herbicida, e consequentemente, a maior concentra??o do mesmo em camadas intermedi?rias. Pode-se concluir que altas concentra??es de picloram no solo s?o nocivas ao crescimento da B. brizantha, principalmente sob condi??es de solos menos ?cidos e esta forrageira pode ser usada para remedia??o de solos contaminados por picloram e na preven??o de sua lixivia??o, que ? maior em solos tratados com calc?rio. / Disserta??o (Mestrado) ? Programa de P?s-Gradua??o em Produ??o Vegetal, Universidade Federal dos Vales do Jequitinhonha e Mucuri, 2013. / ABSTRACT Brazil has vast areas of pasture and the specie most widely cultivated is Brachiaria brizantha. The weed control in these areas is carried out predominantly using herbicides of long residual period, highlighting the picloram. This herbicide is used for weed control broadleaf evergreen and has been intensively investigated due to the high half-life in soil, and their persistence dependent on climate and soil attributes such as texture and pH. The aim of this work was to evaluate the development and potential remediation of B. brizantha in soil contaminated with picloram at different pH levels. The experimental design was a randomized block with four replications and pH among 4.5 and 5.6. The forage was grown up to flowering, when determined the dry weight of the plant components and subsequently were cultivated cucumber plants such as bioindicators of presence of the herbicide. The picloram caused reduction of total dry matter accumulation of B. brizantha, consequently to negative effect on root production, regardless soil pH. The herbicide caused a reduction of leaf dry matter on plants cultivated in higher soil pH. In treatments of high pH value at a depth of 35 cm, there was greater accumulation of dry matter of roots when the herbicide was not applied, indicating that in less acid soils the herbicide tends to hinder the development of grass root at greater depths. B. brizantha reduced picloram concentration in the soil shallow layer, which can be attributed to its ability of degrade the herbicide, and also by fact of absorption and exudation herbicide along the soil layers. In higher pH soils also observed that ??the herbicide has higher potential for leaching, mainly when not cultivated B. brizantha. Soils with lower pH values ??tend to greater sorption of the herbicide, and consequently, a higher concentration of the same in the intermediate layers. Concluded that high concentrations of picloram in the soil are harmful to the growth of B. brizantha, mainly under conditions of soils less acidic and this forage can be used for remediation of soils contaminated by picloram and preventing leaching, which is greater in soils treated with lime.

Submitted by Automa??o e Estat?stica (sst@bczm.ufrn.br) on 2017-01-13T13:10:16Z No. of bitstreams: 1 AlineCamilaMedeirosPinheiro_DISSERT.pdf: 2070282 bytes, checksum: 2dc5a4e02f354ba8fa90c6a7240a1df2 (MD5) / Approved for entry into archive by Arlan Eloi Leite Silva (eloihistoriador@yahoo.com.br) on 2017-01-24T11:56:12Z (GMT) No. of bitstreams: 1 AlineCamilaMedeirosPinheiro_DISSERT.pdf: 2070282 bytes, checksum: 2dc5a4e02f354ba8fa90c6a7240a1df2 (MD5) / Made available in DSpace on 2017-01-24T11:56:12Z (GMT). No. of bitstreams: 1 AlineCamilaMedeirosPinheiro_DISSERT.pdf: 2070282 bytes, checksum: 2dc5a4e02f354ba8fa90c6a7240a1df2 (MD5) Previous issue date: 2016-04-29 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior (CAPES) / Os ecossistemas recifais proveem bens e servi?os que abrangem as esferas social, ambiental e econ?mica. Contudo, cerca de 35% encontram-se amea?ados mundialmente. No Brasil, est?o situados ao longo da regi?o nordeste e geralmente pr?ximos ? costa, facilitando o acesso da popula??o humana que utiliza-os para sustento e lazer. Para manter a resili?ncia e evitar a perda da biodiversidade torna-se importante estudar como ocorre o recrutamento e a sobreviv?ncia dos seres vivos que estruturam as comunidades. O coral Siderastrea stellata, ? um dos mais resistentes e comuns nos recifes brasileiros. Buscou-se entender aspectos da sua distribui??o, recrutamento e manuten??o das col?nias. Para tal, efetuou-se mapeamento das col?nias por tamanho em diferentes s?tios de estudo no Parracho de Pirangi/RN, experimento de recrutamento com manipula??o de rodolitos e experimento de avalia??o da sa?de de col?nias com manipula??o de macroalgas b?nticas. Com o mapeamento observou-se uma zona??o das col?nias, com menos corais ocorrendo pr?ximo ao local destinado ? atividade tur?stica. Possivelmente impactos como a constante suspens?o de sedimentos provocada por banhistas e embarca??es esteja agindo como o mecanismo condutor desta zona??o. O recrutamento de corais foi baixo comparado a outros recifes rasos do nordeste brasileiro. Embora muito resistente, o coral S. stellata n?o est? conseguindo se estabelecer nesta forma??o recifal. Notou-se que o recrutamento n?o ? facilitado por rodolitos. Bancos de rodolitos abrigam alta riqueza de invertebrados bent?nicos que podem competir por espa?o ou se alimentar das larvas de corais. De modo geral, a sa?de das col?nias jovens foi afetada pelo branqueamento, que aumentou ao longo ano. Este aumento foi correlacionado com hipossalinidade e elevada turbidez da ?gua. Por?m, notou-se que na presen?a das macroalgas b?nticas o branqueamento foi menor. Possivelmente o crescimento dessas macroalgas dentro do limite observado atenuou o efeito da elevada radia??o solar nas col?nias jovens de corais, protegendo-as do branqueamento. / Reef ecosystems are known worldwide for their natural beauty and their capacity to harbor a great variety of marine life. In addition, these environments provide goods and services that encompasses social, environmental and economic spheres. However, around 20% of the world's reefs have been destroyed and 35% are threatened. In Brazil, the reefs are located along the northeast region and are usually near the coast, enabling the access of the human populations that use them for food, sport and recreation. One way to maintain reef resilience and avoid biodiversity loss would be to gather information on recruitment and survival of organisms from reef communities. The endemic hard coral, Siderastrea stellata, is one of the most resistant and common species in Brazilian reefs. Considering the ecological importance of this species of coral, we aimed to understand some aspects of its distribution, recruitment and colony maintenance. Therefore, S. stellata colonies were analyzed at different study sites in the ?Parracho de Pirangi/RN?. The following activities were performed: 1) mapping colonies size (Chapter 1), 2) running recruitment experiment subjected to manipulation of calcareous algae (rhodoliths), testing the hypothesis that rhodoliths act as facilitators due its complex three-dimensional structure (Chapter 2), and 3) running a health evaluation experiment of juvenile colonies in different areas of the reef, through macroalgae manipulation, testing the hypothesis that coral colony health is affected negatively by the presence of benthic macroalgae (Chapter 3). A distribution pattern in Parracho de Pirangi/RN was observed with less coral occurring in the area nearby touristic site. It is possible that impacts such as the constant suspension of sediments caused by swimmers and boats are acting as the main mechanism driving this distribuition pattern. Coral recruitment of Parracho de Pirangi was low compared to other shallow reefs from northeastern Brazil. This shows that although very resistant, the coral S. stellata is not able to establish on this reef formation. It was also noted that recruitment is not facilitated by calcareous algae that form rhodoliths. Instead, rhodolith banks sheltered abundant concentration of benthic invertebrates that might compete for space or feed on coral larvae, preventing recruitment. Generally, the health of young colonies was affected by bleaching, which increased throughout the year. This increase was correlated with low water salinity registered. However, it was notable that bleaching was lower in the treatment where benthic macroalgae was not removed. Possibly, the growth of benthic macroalgae within the limits observed over the months attenuated the effects of high solar radiation on young coral colonies, protecting them from bleaching.

Submitted by Automa??o e Estat?stica (sst@bczm.ufrn.br) on 2017-08-01T14:05:21Z No. of bitstreams: 1 AllanMartinsNeves_DISSERT.pdf: 2153659 bytes, checksum: 19b8e265b34574f2712c75f067e65296 (MD5) / Approved for entry into archive by Arlan Eloi Leite Silva (eloihistoriador@yahoo.com.br) on 2017-08-07T15:28:10Z (GMT) No. of bitstreams: 1 AllanMartinsNeves_DISSERT.pdf: 2153659 bytes, checksum: 19b8e265b34574f2712c75f067e65296 (MD5) / Made available in DSpace on 2017-08-07T15:28:10Z (GMT). No. of bitstreams: 1 AllanMartinsNeves_DISSERT.pdf: 2153659 bytes, checksum: 19b8e265b34574f2712c75f067e65296 (MD5) Previous issue date: 2017-06-28 / Conselho Nacional de Desenvolvimento Cient?fico e Tecnol?gico (CNPq) / O cen?rio atual da ind?stria do petr?leo envolve explorar e produzir reservas com desafios t?cnicos enormes. Desta forma, torna-se cada vez mais necess?rio o conhecimento dos mecanismos que impactam a produ??o do ?leo. Um exemplo disso s?o as novas descobertas no mar brasileiro, como o pr?-sal, composto por grandes acumula??es de ?leo leve, com alto valor comercial. Um fator determinante a ser considerado ? o tipo de rocha reservat?rio predominante na forma??o destas reservas, que s?o rochas carbon?ticas, principalmente o calc?rio, que em sua maioria apresenta molhabilidade favor?vel ao ?leo, fator que diminui a recupera??o do petr?leo. Assim, estudos v?m sendo desenvolvidos com esse tipo de rocha visando inverter sua molhabilidade e melhorar a produtividade. Uma maneira de melhorar essas condi??es no reservat?rio ? atrav?s dos m?todos qu?micos envolvendo tensoativos, que pela sua natureza anfif?lica, t?m a capacidade de se adsorver em interfaces e superf?cies de acordo com sua afinidade, diminuindo a energia livre interfacial, podendo inverter a molhabilidade da rocha, facilitando o fluxo de ?leo e assim, melhorando sua recupera??o. O objetivo desse trabalho foi estudar como diferentes tipos de tensoativos se adsorvem na rocha calc?ria, e se eram capazes de alterar sua molhabilidade. Para isso, foi utilizado o m?todo de banho finito para tr?s tensoativos: OCS (ani?nico), C16TAB (cati?nico) e ULTRANEX 110 (n?o i?nico), variando-se par?metros como a temperatura, a massa de adsorverte (calc?rio), tempo de contato e concentra??o de tensoativo. Tamb?m foram feitas an?lises de ?ngulo de contato para analisar a molhabilidade e de potencial zeta. O OCS foi o ?nico tensoativo que apresentou adsor??o significativa na rocha, possivelmente por apresentar ?ons opostamente carregados aos da rocha. O aumento da temperatura de 30?C para 50?C ocasionou decr?scimo na capacidade de adsor??o. O calc?rio in natura apresentou molhabilidade mista, com forte afinidade ao ?leo, que ap?s tratamento ocorreu diminui??o da molhabilidade ao ?leo, no entanto tamb?m diminuiu em rela??o ? ?gua. As medidas de potencial zeta mostraram que as atra??es eletrost?ticas desempenharam papel importante na adsor??o, obtendo-se maior valor em m?dulo para o OCS. / The current scenario of the oil industry involves exploring and producing reserves with big technical challenges, in this way, it becomes increasingly necessary to know the mechanisms that impact the oil production. An example of this is the new discoveries in the Brazilian sea, with the pre-salt, composed of large accumulations of high commercial value light oil. However, a determining factor to be considered is the type of reservoir rock predominant in the formation of its reserves. These rocks are composed almost of carbonates of calcium that form the carbonate rocks, mainly limestone, which in the majority of them are oil-wet, a factor that Decreases the recovery of oil. Thus, studies have been developed in this type of rock in order to reverse its wettability and improve productivity. One way of change the wettability of the reservoir is through the chemical methods involving surfactants, which by their amphiphilic nature have the ability to adsorb at interfaces and surfaces according to their affinity, reducing the free interfacial energy, which can reverse the wettability of the rock, facilitating the flow of oil and thus, improving its recovery. The objective of this work was to study how different types of surfactants adsorb in limestone, and if they were able to alter their wettability. For this, the finite bath method was used for three surfactants: OCS (anionic), C16TAB (cationic) and ULTRANEX 110 (nonionic), varying parameters such as temperature, adsorption mass (limestone), contact time and concentration of surfactant. Contact angle analysis was also performed to analyze wettability and zeta potential. OCS was the only surfactant that presented significant adsorption in the rock, possibly due to the presence of electrically charged ions. The increase in temperature from 30 ? C to 50 ? C caused a decrease in the adsorption capacity. The limestone in natura presented mixed wettability, with strong affinity to the oil, after treatment the wettability decreased to oil, however it also decreased in relation to water. The measurements of zeta potential showed that the eletrostatic attractions played an important role in the adsorption, obtaining greater value in the module for the OCS.

Foi investigada a influência de elementos de liga como o Cromo, o Níquel, o Carbono e o Nitrogênio no intervalo de solidificação de um aço inoxidável martensítico fundido do tipo CA6NM. Este tipo de aço, utilizado na fundição de peças de grande porte, é bastante utilizado pela sua ótima resistência ao impacto, e boas propriedades contra corrosão em meio aquoso. Além disso, este aço possui ótima fundibilidade, tendo como principal característica seu reduzido intervalo de solidificação, o que torna diminutos os defeitos relacionados a este fenômeno. Resultados obtidos por cálculos termodinâmicos utilizando-se o Thermo-calc sugeriram forte dependência deste parâmetro em relação ao teor de Carbono (0,018%C a 0,044%C), com o intervalo de solidificação variando de 25°C a 43°C no intervalo de composições definidos pela norma como aceitáveis para a liga. Os outros elementos de liga analisados, segundo os cálculos termodinâmicos, não demonstraram influência significativa dentro das faixas toleradas pela norma. Foram fundidas 13 amostras com as composições químicas simuladas no Thermo-calc, e seus intervalos de solidificação foram investigados por análise térmica diferencial (DTA) e calorimetria exploratória diferencial (DSC). Contrariando os resultados do Thermo-calc, a influência do Carbono não foi comprovada, não havendo variação do intervalo de solidificação entre as amostras. Para confirmar os resultados de análise térmica, as amostras desta técnica foram analisadas por metalografia, não sendo observado qualquer tipo de reação no material ensaiado (descarbonetação, oxidação, etc). / The influence of alloying elements like Chromium, Nickel, Carbon and Nitrogen on the solidification interval on a CA6NM martensitic stainless steel casting was investigated. This steel class, mainly used on large castings, applies due to the fact that it has very good impact resistance, and satisfactory corrosion properties. Besides that, this stainless steel class has excellent castability, having as an important characteristic its reduced solidification interval, diminishing the tendency for solidification defects. The results obtained by thermodynamic calculations using Thermo-calc package have suggested a strong influence of the Carbon content on the solidification interval (25°C a 43°C) when the carbon content is varied within the range allowed by the alloy standard (0,018%C to 0,044%C). Other alloying elements, according to the thermodynamic calculations, have no influence over the solidification interval. Thirteen samples were cast based on the simulated chemical compositions and their solidification interval was investigated by differential thermal analysis (DTA) and differential scanning calorimetry (DSC). Contrary to the thermodynamic calculations, no influence of Carbon was observed on the solidification interval. In order to confirm the thermal analysis results, metallographic tests were performed on the DTA samples, with no observation of any unusual reaction on them, like oxidation or decarburizing.

This work deals with the effects of high temperature exposition of low alloyed creep resistant steels on their structural stability and structural stability of their weld joint. The theoretical part of this work gives an overview of creep resistant steels considering their chemical and phase composition and their connection to high temperature mechanical properties. The CALPHAD method is presented as generally accepted approach for equilibrated calculations and Thermo-Calc and DICTRA software packages are introduced as CALPHAD applications. Thermo-Calc software is used for calculation of phase composition of the examined materials and for calculation of the phase diagrams. Software DICTRA is used for simulations of diffusion controlled phase reactions in the analysed weld. Experimentally one weld joint of the steels 15 128 and 15 313 has been studied after four different annealing procedures. The experimental results include chemical profiles across the welds, microhardness profiles and metallographic analysis of significant regions of the welds. These experimental results are compared with the simulation results. The comparison shows a reasonable agreement between experimental and simulation data.

No description available.