O processamento de petróleo e seus derivados é analisado pela aplicação combinada e sistemática da Primeira e da Segunda Lei da Termodinâmica, análise exergética, permitindo a localização dos principais processos destruidores da capacidade de realização de trabalho ao longo da cadeia de processamento. Após a localização das irreversibilidades, diversas opções para melhoria dos processos são avaliadas. A exergia consumida nos processos é dividida em renovável e não renovável e posteriormente repartida, junto com as respectivas emissões de CO2, entre as diversas correntes de cada unidade de processamento. Para uma repartição racional dos fluxos exergéticos e de CO2, a análise exergoeconômica foi utilizada. Um sistema, que permite interações cíclicas entre a cadeia produtiva dos principais combustíveis utilizados no Brasil e a produção de eletricidade, foi elaborado a fim de permitir uma comparação entre os diversos combustíveis levando em consideração toda a cadeia produtiva. Esta comparação está fundamentada no consumo de exergia renovável e não renovável e nas emissões de CO2. Pode-se concluir que o coque de petróleo é o combustível que mais emite CO2, em seguida, encontram-se o carvão e a gasolina. O diesel hidrotratado vem após a gasolina, devido principalmente ao consumo de hidrogênio pelo hidrotratamento. Embora o diesel convencional emita mais SOx e NOx, este diesel exige menos exergia não renovável e emite menos CO2 que o diesel hidrotratado. O hidrogênio, se produzido da forma convencional (reforma a vapor de hidrocarbonetos leves), é o combustível mais intenso em exergia não renovável e com emissão de CO2 próxima ao valor da gasolina e maior que o valor obtido para o diesel convencional. O etanol se mostra uma boa alternativa ao uso dos derivados de petróleo, mesmo considerando configurações típicas para as usinas sucroalcooleiras. / The oil processing is analyzed by the combined and systematic application of the First and Second Laws of Thermodynamics, exergy analysis, allowing the location of the processes responsable for the main destructions of work capability along the processing chain. After the location of irreversibilities, several options for improving processes efficiency are evaluated. The exergy consumed in the processes is divided into renewable and non-renewable and then distributed, along with their CO2 emissions, among the various currents of each processing unit. For a rational distribution of the exergy and CO2 flows, exergoeconomy analysis takes place. A system that allows cyclical interactions between the productive chain of the main fuels used in Brazil and electricity production, is designed to allow the comparison among different fuels taking into account the entire production chain. This comparison is based on renewable and non-renewable exergy consumption and CO2 emissions. It can be concluded that the petroleum coke is the fuel that emits more CO2 followed by coal and gasoline. The hydrotreated diesel comes after gasoline, mainly due to the consumption of hydrogen for hydrotreating. Although conventional diesel emit more NOx and SOx, this diesel requires less non-renewable exergy and emits less CO2 than hydrotreated diesel. Hydrogen, if produced in the conventional way (steam reforming of light hydrocarbons) is the fuel most intense in nonrenewable exergy consumption and has CO2 emission near the value of gasoline and higher than the value obtained for conventional diesel. Ethanol is a good alternative to the use of petroleum derived fuels, even considering typical configurations for sugarcane mills.

Com a tendência da indústria automobilística em produzir motores com maior potência e menor consumo de combustível, a redução em peso dos componentes tem sido cada vez mais exigida. Isto tem desafiado a Ciência dos Materiais em desenvolver novos produtos que apresentem alta resistência mecânica para compensar a redução de peso desejada. No entanto, a fabricação de aços especiais implica em características de produto e de processamento altamente complexas. As diferentes rotas de fabricação apresentam limitações termodinâmicas, cinéticas e físicas, de recursos e de equipamentos, que devem ser balanceadas, visando viabilidade produtiva mas atendendo às especificações e às exigências da aplicação final. Assim são os desenvolvimentos de elementos de suspensão automotiva, que tem característica fundamental a redução de peso, implicando portanto em desafio constante para o projeto da peça e para o aço especificado. O presente trabalho teve como objetivo principal o desenvolvimento de um aço para aplicação em suspensão automotiva com alto desempenho em fadiga, menor peso e custo otimizado. A rota simplifica o processo produtivo, eliminando etapas intermediárias e também abre possibilidade da utilização de aços de aciaria elétrica, uma rota inovadora e desafiadora em relação à utilização de matéria-prima reciclada. Os objetivos foram alcançados através de um processo de engenharia de inclusões. O controle e a caracterização destas inclusões foram fundamentais, sendo necessárias técnicas diferenciadas como complemento às técnicas tradicionais. Foram utilizadas técnicas de microscopia ótica, microscopia eletrônica, espectrometria e dissolução ácida, visando complementar as caracterizações superficiais, volumétricas, e composicionais, além de testes dinâmicos, aumentando-se a amostragem tradicionalmente utilizada. O material estudado foi gentilmente cedido pela Gerdau Aços Especiais Brasil de Pindamonhangaba - SP, onde também foram realizados os testes e análises. Observou-se que a metodologia com diferentes técnicas de caracterização mostrou-se boas para avaliação do aço. Ainda, que o controle dos parâmetros de fabricação do aço líquido é fundamental para o desempenho final do produto e que a rota de aciaria elétrica e lingotamento contínuo mostraram-se viáveis para produção da matéria-prima de elementos de suspensão de alto desempenho. No entanto, é necessário um controle diferenciado de inclusões. Essa rota e controles levaram ao desenvolvimento de um material com alto limite de resistência mecânica, até 2100Mpa conforme as condições de tratamento térmico. Foi possível também associar a vida em fadiga às dimensões das inclusões, sendo que inclusões acima de 30?m reduziram a vida em fadiga do arame em 4 vezes. / Following the tendency of automotive industry to produce motors with higher power and less fuel consumption, weight reduction of components has been more and more demanded. This has defied Materials Science to develop new materials with higher mechanical resistance, to match the aimed weight reduction. However, production of special steel grades implies in highly complex product and process characteristics. There are different production routes, with thermodynamic, kinetic and physical limitations, as well of resources and of equipment, which must be balanced, aiming production feasibility and also matching product specifications and its final applications. Development of automotive suspension components have, for example, the weight reduction as main characteristic, what implies a constant challenge to the design project and also to the specified steel. This work aimed to develop a new steel applied to automotive suspension, with high fatigue performance, lower weight and optimized cost. The proposed route simplifies the productive process, eliminating intermediate steps and also uses steel melted in electric arc furnace, an innovative and challenging route concerning recycled raw material. The objectives were achieved through a process of inclusion engineering. The control and characterization of these inclusions were fundamental, and differentiated techniques were used, complementing the traditional ones. It was used optical microscopy, electron microscopy, spectrometry and acid dissolution, to complement the surface, volumetric and compositional characterization, and also dynamic testing, increasing the usual sampling. The studied material was kindly provided by Gerdau Aços Especiais Brasil - Pindamonhangaba - SP, where the tests and analysis were performed. It was observed that the methodology was suitable for the steel evaluation. And that the control of the steelmaking parameters is fundamental for the final performance of the product. It was also possible to conclude that the steelmaking based on electric arc furnace and continuous casting can be feasible to produce raw-material for high-performance suspension applications, once a differentiated inclusion control is applied. It was concluded that the methodology with different characterization techniques was good for the analysis, complementing each other. Liquid steel parameters control is fundamental for the final performance of the product. Electric Arc Furnace and Continuous Casting route are reliable for the production of raw material for high performance suspension parts. However, it is necessary to control the inclusions. The applied route created a material with high mechanical resistance, up to 2100MPa, depending on the heat treatments conditions. It was also possible to associate the fatigue life to the inclusion dimensions, and the inclusions above 30?m reduced the fatigue life of the wire in about four times.

Bio-refining of renewable resources such as waste biomass into value added products has increased rapidly over the last decades. The aim is to find new environmentally friendly yet economically feasible ways of replacing current utilization of non renewable resources. It can be expected that a commercially viable next generation bio-ethanol will be produced from lignocellulosic feedstock in the near future.This master thesis set out to look at a specific Canadian company in depth (Pure Lignin Environmental Technology Ltd), known as PLET henceforth. PLET has a new approach in pre-treatment of biomass, with a recently patented environmentally friendly technology, which could be extremely lucrative if applied in the right context. It is desirable to look at the possibility of using the master thesis as a take-off platform to launch a consulting bio-tech company directly after completion.There are several different ways to process biomass into higher value added products. In this master thesis focus is laid upon biomass waste, but the same principles could be applied on biomass processing in general. That is the separation and purification of products. In order to put the technology of PLET into a context, other company approaches are used as a comparison, such as SEKAB E-Technology, Lignoboost and Borregaard Lignotech.It is however hard to find suitable examples equivalent to the PLET approach since the technology of PLET considers all the three constituents of wood as raw material for production of three stand alone commercial products; pure lignin, pure cellulose and hemi-cellulose. These three products are separated and purified in the pre-treatment process at high yield and practically no formation of by-products. Process parameters are only moderately adjusted depending on what raw material is used.The catalytic reactor process (=CRP), is performed by PLET as a pre-treatment in a continuous and batch system, in which lignocellulosic material (= wood chips, saw dust or other waste biomass) undergo acid catalyzed hydrolysis by dilute nitric acid. The impregnated wood chips are partially depolymerised from the lignin matrix when heated in the low pressure catalytic reactor. After that, follows distillation, condensation and almost complete recovery of dilute nitric acid. After CRP, the cellulose pulp is separated from the black liquor by an alkaline solution (=NaOH). The obtained black liquor is pumped to a separation tank to precipitate lignin and sweet liquor through filtration. The final step is to dry the lignin, while the sweet liquor is utilized by Torula yeast (=Candida utilis) in order to produce unicellular protein.It would be interesting to see if the pre-treatment that PLET provides, could be exploited in a context of production of next generation of cellulosic ethanol from the cellulosic part of waste biomass. In this master thesis, an evaluation of producing next generation ethanol from dilute-nitric acid pre-treated cellulose rich softwood was performed and dilute sulphuric acid pre-treated hemi-cellulose rich hardwood birch pulp was used as a comparison.The technical part of this master thesis was conducted on a laboratory scale, using samples from two companies, referred to as PLET and SEKAB E-technology (Sweden). The strategy of PLET is currently to find a commercial platform to produce value added products from waste biomass generated by saw mills and pulping industries, while SEKAB E-Technology mainly works with Swedish softwood as a raw material.ivExperiments of this master thesis includes a series of fermentation trials using either SSF (= Simultaneous Saccharification and Fermentation) or SHF (= Separate Hydrolysis and Fermentation). Yields of the enzymatic hydrolysis and subsequent fermentations were estimated with HPLC measurements complemented with dry weight measurements.Obtained experimental data support the potential to make lignocellulosic ethanol out of either softwood or hardwood. Ethanol yield from dry material from SEKAB E-Technology hardwood birch slurry was 0.43 (g ethanol / g dry raw material), whereas samples supplied by PLET achieved the following results. The ethanol yield from dry material from softwood pine washed cellulose was 0.33 g (ethanol / g cellulose). The ethanol yield from dry material obtained for softwood pine unwashed cellulose in the three SHF was 0.47; 0.34 and 0.19 (g ethanol / g cellulose) respectively, while the yield in the two SSF was 0.45 and 0.46 (g ethanol / g glucose).The economical part of this master thesis includes the use of Business Model Canvas and the NABC- model (= Need, Approach, Benefit and Competition) to define the basic topics and tasks that need to be addressed in the start up phase of a small consulting bio-tech company.At least 6 million US dollars is needed as a minimum starting capital to be able to construct a small commercially viable pilot plant, according to PLET. This investment would cover the basic requirements and is scalable. The construction could preferably be done in Sweden in the vicinity of an existing saw mill or paper pulp industry or elsewhere, where a steady supply of cheap raw material could be assured. The size of the operation envisioned, depends greatly on location and adjacent businesses. Large pulp mills in the range of 400-500 MWh would be preferred, the largest pulp mills in Canada process 5000 ton per day which is equivalent to a capacity of 1 GW wood per day (GW = giga watt), but the concept of the technology of PLET must first prove its value on a smaller scale.According to PLET, a future full scale production plant could be designed for processing 56 tons of wood chips per day of wood chips would generate annual revenues of ≈ 7500000 US dollars. The annual profit would be ≈ 2500000 US dollars, and capital cost (equipments) ≈ 5000000 US dollars, while the payback time on investment would be 2-3 years. According to PLET, the products are estimated to have the following values; 25 tons/day of pure cellulose with a market value of 400-500 US dollars/ton, 10 tons/day of pure lignin with a market value of 1000-1200 US dollars/ton and finally 21 tons/day of sweet liquor with a market value of 50-100 US dollars/ton. / Program: Masterutbildning i Energi- och materialåtervinning - industriell bioteknik

[pt] O mercado brasileiro de combustíveis apresenta uma nova realidade com a mudança na política de preços praticados por sua principal empresa de petróleo, onde até o ano de 2016 foi caracterizado pelo monopólio devido aos preços artificiais impostos por esta de modo a controlar a inflação no país. Atualmente os preços dos produtos nas refinarias nacionais estão alinhados ao mercado internacional de commodities, viabilizando a entrada de novos competidores para atender a demanda do país. Com este cenário, surgem questões relativas a utilização do refino e níveis de preços a serem adotados no mercado interno de forma a trazer maior competitividade no mercado de forma duradoura e sustentável. Modelos de otimização são utilizados para suportar a tomada de decisão no planejamento da cadeia de downstream e definir a melhor utilização dos recursos disponíveis. Clientes e fornecedores possuem objetivos e custos diferentes, e a necessidade de integrar modelos que dialoguem entre as cadeias de abastecimento destes grupos faz-se necessária, onde os resultados da empresa são impactados de acordo com suas decisões de produção e participação no mercado. O experimento consistiu na construção uma modelagem de rede para a cadeia de distribuição de combustíveis no Brasil a partir de duas ferramentas de otimização existentes, uma delas utilizando-se SIG. Assim, esta modelagem traz uma aplicação eficaz para a empresa, pois a auxilia na quantificação de seus resultados em um cenário de competição em que a mesma se encontra inserida, considerando as singularidades do mercado e indústria no país. / [en] A recent change in the national Brazilian oil company price policy introduced a new market reality as the imposed artificial prices scheme used in order to control inflation was abandoned. Currently, refined products prices in the national territory are matched to the international commodities market, allowing the entry of new competitors to meet national demands. According to this scenario issues relating to infrastructure and a new set of prices to be adopted by the Brazilian domestic market aiming for increased competitiveness on the national market on a long-lasting and sustainable basis begin to appear. Optimization models are used to support the downstream supply chain planning decisionmaking and to ensure the best use of available production resources. Customers and suppliers have different objectives and costs, and it is necessary to integrate models which allow supply chain groups to dialogue among themselves, where the company s result are affected according to their production decisions and market share. The experiment described here consists of the building of a network modelling for the Brazilian fuel distribution chain starting from two optimization tools already available, one of them using GIS. Thus, this modelling brings an effective application to the company, as it assists in the quantification of its results in a competition scenario in which it is inserted, considering the singularities of the Brazilian market and industry.

Abstract Refining grain size is known to enhance mechanical properties also in austenitic stainless steels. To better understand the background of these properties, various reversion-treated structures were created in AISI 301LN (18Cr-7Ni-0.15N) steel and the microstructural features affecting flow behaviour and strength under monotonic and cyclic straining were investigated. Fully and partially reversed microstructures were produced using prior cold rolling thickness reductions in the range of 32–63% and both resistant and induction heating. Some selected reversed structures were also strengthening rolled to 20% reduction. The resultant microstructures were characterised using different research equipment and methods and their mechanical properties determined by microhardness, tensile and fatigue tests. The main interest was focused on the microstructural features of low-temperature reversed structures and the stability of austenite in them. Effective grain refinement was achieved after 56–63% rolling reduction. Depending on the reduction and annealing conditions, the reversed structures consisted of various amounts of submicron- and medium-sized austenite grains and retained phases. All the reversed structures showed non-homogenous, often bimodal grain size distribution. It was demonstrated that the stability of austenite was much reduced after annealing at temperatures ≤ 850 °C, which was attributed to precipitation occurring at these low temperatures. Fine grain size itself promoted higher stability, but the coarsest retained austenite was stable due to its special orientation. Therefore, medium-sized grains of 3–10 μm, formed mainly from slightly deformed strain-induced martensite, appeared to be most unstable, the fraction being highest after the lowest reduction. The yield and fatigue strengths of the low-temperature reversion-treated structures were significantly higher than those of commercial 301LN. Fatigue strength corresponded to that of a 20% cold-rolled sheet. Strength was highly enhanced even after the lowest cold rolling reduction of 32%, for the lower strength of the coarser reversed grain structure was balanced by the higher fractions of strong retained austenite and martensite phases. / Tiivistelmä Austeniitin raekoon hienontamisen tiedetään parantavan merkittävästi ruostumattomien terästen mekaanisia ominaisuuksia. Hienorakeisten reversiorakenteiden muokkauslujittumiseen ja lujuuteen vaikuttavien tekijöiden yksityiskohtaista tutkimista varten tuotettiin AISI 301LN (18Cr-7Ni-0.15N) teräkseen 32–63% kylmävalssausreduktiota ja sen jälkeistä vastus- tai induktiokuumennusta käyttäen täysin sekä osittain reversoituneita mikrorakenteita. Lisäksi osa reversiorakenteista vielä lujitusvalssattiin 10–20% reduktioon saakka. Mikrorakenteiden karakterisointiin käytettiin monipuolisesti eri tutkimuslaitteita ja menetelmiä sekä mekaanisten ominaisuuksien määrittämiseen mikrokovuus-, veto- ja väsytyskokeita. Ensisijaisena tarkoituksena oli tutkia yksityiskohtaisesti matalassa reversiolämpötilassa muodostuneita mikrorakenteita sekä hienorakeisen austeniitin stabiilisuutta monotonisessa ja syklisessä kuormituksessa. Reversiokäsitellyissä rakenteissa esiintyi vaihteleva määrä hienoja (raekoko alle 1 μm) ja keskisuuria (raekoko 3–10 μm) austeniittirakeita mahdollisien karkeiden jäännösfaasien lisäksi kylmämuokkaustilasta ja lämpökäsittely-parametreista riippuen. Suuri muokkausaste edesauttoi selvästi raerakenteen hienontumista, mutta kaikki rakenteet olivat raekokojakaumaltaan epähomogeenisia. Työssä demonstroitiin kuinka alle 900 °C:ssa hehkutetut reversiorakenteet ovat huomattavasti epästabiilimpia kuin korkeammassa syntyneet verrokkirakenteet, minkä osoitettiin johtuvan krominitridien erkautumisesta. Raekoon hienontuminen itsessään suosii suurempaa stabiilisuutta, mutta karkeimmat muokkautuneet jäännösausteniittirakeet olivat stabiileja niiden orientaation takia. Täten keskisuuret rakeet olivat epästabiileimpia. Keskisuurien rakeiden osoitettiin syntyvän pääasiassa vähän muokkaantuneesta martensiitista, ja niitä esiintyi eniten 32% reduktiolla valssatuissa rakenteissa. Matalassa lämpötilassa syntyneiden reversiorakenteiden lujuus oli merkittävästi korkeampi kuin kaupallisen teräksen. Väsymislujuus vastasi noin 20% lujitettuvalssattua tuotetta. Hehkutusta edeltänyt kylmämuokkausaste vaikutti vain vähän reversiorakenteiden lujuuteen, sillä vaikka pienin muokkausaste johti karkeimpaan keskimääräiseen raekokoon, siinä lujuutta lisäsivät kovat jäännösfaasit.

The present thesis was to study non-metallic inclusions during vacuum degassing in ladle treatment. Emphasize was mostly given to liquid CaO-Al2O3 inclusions. A series of industrial experiments were carried out at Uddeholm Tooling AB, Hagfors, Sweden. To gain an insight into the industrial findings, laboratory investigations were also performed. Large number of steel samples were collected and examined. Liquid calcium aluminate inclusions with low SiO2 and high SiO2 were often found with spinel inclusions before vacuum degassing. Laboratory experiments showed that spinel would react with the dissolved Ca in the liquid steel forming calcium aluminate inclusions. This laboratory results agreed with the industrial observation that spinel phase was quite often found in the center of the calcium aluminate phase. After vacuum degassing, most of the inclusions were calcium aluminate liquid inclusions. When dissolved Al level was low, 2 types of liquid calcium aluminate inclusions with considerably different SiO2 contents were found to coexist even at the end of the process. In view of the lack of the thermodynamic data for SiO2 activities in the low silica region, thermodynamic measurements were conducted in the CaO-Al2O3-SiO2-MgO system. The experimental results could reasonably explain the coexistence of the two types of the liquid oxide inclusions. While the total number of inclusions decreased during vacuum degassing, the number of bigger inclusions (>11.3 μm) increased generally in used ladles. This finding was in accordance with the previous studies, wherein, ladle glaze was found to be responsible for the supply of bigger inclusions. The behaviors of several types of inclusions in liquid steel were examined using a laser scanning confocal microscope (LSCM). While alumina inclusions tended to impact on each other, agglomerate and grow very quickly, none of the other types of inclusions, such as spinel and calcium aluminate was observed to agglomerate. The results of LSCM study agreed well with the industrial observation. Examination on a huge number of inclusions did not show any indication of impact and physical growth of the inclusions, except the alumina inclusions. The removal of inclusions around open-eye in a gas-stirred ladle was experimentally studied by a cold model with oil and water. Most of the simulated inclusions were brought up to the oil phase by gas-water plume. Inclusion removal into oil layer took place when the inclusions passed through the sphere-bed of the oil layer around the open-eye. A calculation showed that the contribution of metal-gas plume in inclusion removal was much larger than that of buoyancy mechanism. The results of the industrial experiments revealed that the inclusions distribution strongly depended on stirring condition. When a ladle was stirred by both gas and induction, inclusion removal near slag layer was significant. / QC 20100803

<p>The thesis is based on two supplements with two major objectives. In the first supplement equilibrium top slag-steel bulk and inclusions-steel bulk were investigated by comparison between calculated and measured oxygen activity values. This was done by applying different oxide activity models for slags combined with thermodynamic calculations. In the second supplement the inclusion composition is studied during the ladle refining process. The inclusion composition is related to top slag composition and other parameters during ladle</p><p>treatment.</p><p>The work was carried out by collecting data during well controlled sampling procedures at two different steel plants. Extensive inclusion analyses in Scanning Electron Microscope, SEM, were done. The data was used together with thermodynamics for a description of the interaction between slag-steel-inclusion interaction during ladle treatment.</p><p>Evaluation of inclusion composition during the ladle refining have revealed that the majority of the inclusions belonged to the system Al₂O₃-CaO-MgO-SiO₂and showed a continuous composition change throughout the ladle refining process, from high Al₂O_3, via MgO-spinel to finally complex types rich in CaO and Al₂O_3. The final composition after vacuum treatment was found to be close to the top slag composition. Small process parameter changes and practical variations during ladle refining were proven to give large differences of the inclusion composition.</p><p>Finally, it was concluded that equilibrium does not exist between top slag and steel bulk, with respect to oxygen, for the studied conditions. However, the equilibrium does exist between the steel bulk and inclusion.</p>

This dissertation analyses the history of the politics of pollution and petroleum refining in South Africa during the first decade of Apartheid, focusing on the country's first two oil refineries, both of which were built by multinational oil companies in Durban in the 1950s and 60s. It traces the origins of the development of environmental regulation in relation to oil refinery pollution. The dissertation outlines the development of a sense of disillusionment caused by the persistence of pollution problems associated with petroleum refining in the face of failed attempts at technological and expert interventions. The study identifies the existence of a civic culture amongst Bluff residents founded on ratepayer and landowner identities, through which they were able to exercise considerable purchase on the local State. Ultimately, the story of how two petroleum refineries ended up in the midst of residential communities in south Durban's represents a reiteration of the importance of race to the development of local urban landscapes during Apartheid. / Thesis (M.A.)-University of KwaZulu-Natal, Durban, 2004

Understanding and control of the flow structures in metallic fluids is important for the development of optimal crystal growth processes. One of the techniques used to control flow structures is the application of a rotating magnetic field (RMF) in the plane perpendicular to the growth direction, which induces two magnetic body force components; one in the radial direction and the other one in the circumferential direction. These two body force components alter the fluid flow in the growth system, leading to enhanced mixing, flatter growth interface, and more homogeneous crystal composition. The application of RFM was therefore considered in three separate projects: 1) the zone refining of cadmium and tellurium, 2) the synthesis of cadmium telluride (CdTe) by the travelling heater method (THM), and 3) the THM growth of gallium antimonide (GaSb). In the zone refining of tellurium, the objective was to enhance the transport of selenium in the melt since the selenium segregation coefficient is close to unity. A magnetic field with intensity of 0.6 mT and frequency of 100 Hz was selected based on the results of earlier numerical simulations. Due to the very low electrical conductivity of tellurium, the numerical simulations predicted a very small effect of RMF on selenium transport. The designed zone refining experiments for the tellurium system have verified this numerical simulation result. On the other hand, cadmium is an electric conductor, and thus the numerical simulations predicted a notable effect of RMF. However, experiments on the cadmium system could not be carried out because of the instability of molten zones caused by cadmium’s very high thermal conductivity. The commercial synthesis of CdTe is presently done by THM, which produces materials with much better stoichiometry than other techniques, but very slow process speeds make THM very costly. An application of RMF was considered in order to improve the speed of the process. A 1.3 mT, 0.5 Hz field was applied during the THM synthesis of CdTe. Under the experimental conditions employed, the examination of samples has shown that the application of RMF did not increase the maximum synthesis speed. The use of higher intensity RMF was not possible with the present system, but it is thought that higher fields might worsen the mixing of Cd and Te to produce non-stoichiometry. The objective of the third project was to carry out preliminary THM growth experiments for GaSb under RMF in order to prepare a basis for future THM growth experiments aimed at reducing the cost of THM by using higher growth rates and smaller seeds with tapered ampoules. The substantially redesigned THM furnace permits rotation of the growth ampoule, better control of the experimental environment, and a stronger temperature gradient at the growth interface. Two crystals have been grown at 25 mm diameter with and without the application of a magnetic field of 0.6-mT intensity and 100-Hz frequency. These preliminary experiments have shown that the system can be used for the planned THM experiments; however, further experiments are required to attribute any effect to RMF.

Compared to more common used austenitic stainless steels, ferritic stainless steels contain very low amounts of the expensive alloying element Ni. In addition, they have good corrosion properties, but are sometimes suffering from poor weldability and bad mechanical properties. This is mainly due to the presence of large grains after casting and large grain growth during heat treatment or welding. Processes for reducing the grain size (grain refining) of metal alloys are widely known and proven before to be suitable for many alloys. A successful grain refining process can increase the strength of an alloy without decreasing the ductility. This can be achieved by different methods, such as rolling or cooling. In this work, the focus has been on studying the aspect from a metallurgist point of view, to analyse the possibilities to create small particles in the liquid stage to enhance the solidification. The focus has been on oxide and nitride formation for nucleation of smaller grains during solidification. This study was made by forming particles, develop the analysis methods and thereafter to study the effect of particles on the structure of a ferritic stainless steel. The particles were formed by additions of Ti, Ce and Zr in to a liquid Fe-20mass% Cr alloy containing different amounts of oxygen and nitrogen. The electrolytic extraction technique was used to achieve a good understanding of the reaction processes and the particles size, number, composition and morphology. The grain sizes and the particles were then studied in as-cast samples as well as in specimens heat treated for 60 minutes at 1200, 1300 and 1400°C in a Confocal Scanning Laser Microscope (CSLM). Also, based on Scanning Electron Microscope (SEM) determinations and Thermo-Calc calculations, the precipitated particles were divided as primary and secondary particles. Thereafter, the grain refining potential was studied for each of these types. In this work, particles engineering by using small particles have been proven suitable for the Fe-20mass% Cr ferritic stainless steel alloys. Although the work has been based on small-scale samples and experiments, the results show good tendencies with respect to grain refining as well as a clear relationship between the particles in the steels and the microstructures. It was found that Ti-Ce additions in Fe-20mass% Cr alloys resulted in complex oxides including Ti, Ce and Cr. These oxides were observed to have high agglomeration tendencies and therefore to form larger particles or clusters. The grain refining potential on the solidification structure was insignificant, despite a relatively large amount of particles. However, Ti-Zr additions in Fe- 20mass% Cr alloys on the other hand resulted in primary precipitated particles such as ZrO2 and ZrO2+ZrN. Furthermore, ZrN nucleated ferrite during solidification, which lead to a clearly observed grain refining effect. This effect was also increased with an increased number of particles. The amount of particles (primary and secondary) was also found to increase with an increased amount of nitrogen. Secondary particles (mostly TiN) were precipitated near grain boundaries, which lead to a location based pinning effect of the grain growth during heat treatment at 1200 °C. This pinning effect was increased by an increased nitrogen content and thereby an increased number of particles. Finally, the pinning effect was clearly reduced during heat treatment at 1400 °C. / QC20100524