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The rise of Zn-coatings on direct press hardened steels for body-in-white passenger safety applications over the widely used Al-Si coatings is due to its lower cost, compatibility with Zn-based paint systems, and offers sacrificial cathodic protection in addition to barrier protection. Manufacturing the complexly-shaped high strength automotive parts using the direct hot press forming method (DHPF) transforms the Zn-based coating into a mixture of Γ-Fe3Zn10 and α-Fe(Zn). Previous literature has determined that a minimum of 15 vol% Γ-Fe3Zn10 is required within the coating to provide robust cathodic protection of the steel substrate. This assumed the mixed potential theory is valid for modeling the electrochemical properties of the mixed phase coating; however, the interwoven coating phase morphology results in varying volume fractions of Γ-Fe3Zn10 and α-Fe(Zn). Potentiodynamic polarization scans of GI70 coated 22MnB5 steel annealed at 890°C for various annealing times revealed that Γ-Fe3Zn10 + α-Fe(Zn) coatings with at least 11 vol% Γ-Fe3Zn10 exhibit electrochemical properties insignificantly different from those comprising pure Γ-Fe3Zn10, and behaves similarly to pure α-Fe(Zn) for coatings with less than 11 vol% indicating that the Γ-Fe3Zn10 + α-Fe(Zn) coatings behave as a homogeneous single phase, thus validating the use of the mixed potential theory. Scanning vibrating electrode technique analysis of various galvanic couples determined that Γ-Fe3Zn10 provides strong cathodic protection for the 22MnB5 steel and moderate protection for α-Fe(Zn), while the 22MnB5 steel is only weakly protected by α-Fe(Zn). Separation of the 22MnB5 steel and Γ-Fe3Zn10 by an intermediary α-Fe(Zn) layer reduces the cathodic protection of the 22MnB5 steel since the α-Fe(Zn) layer acts as an electron receptor and limits the macroscale throwing power of Γ-Fe3Zn10. / Thesis / Master of Applied Science (MASc) / Zn-coatings on direct press hardened steels are designed to electrochemically protect the steel substrate from corrosion. Manufacturing automotive parts using the direct hot press forming method transforms the Zn-based coating into a two-phase mixture of Γ-Fe3Zn10 and α-Fe(Zn). The previously determined minimum 15 vol% Γ-Fe3Zn10 required for the coating to provide the steel substrate robust protection assumed that mixed potential theory was a valid model to predict the electrochemical properties of the two phase coating, despite its complex microstructure. It was found that the use of mixed potential theory was valid as it was determined that the Γ-Fe3Zn10 + α-Fe(Zn) coatings behave as a single phase, with robust cathodic protection of direct hot pressed coatings requiring a minimum of 11 vol% Γ-Fe3Zn10. It was further determined that Γ-Fe3Zn10 cathodically protects both the steel and α-Fe(Zn), while α-Fe(Zn) only weakly cathodically protects the steel.

Les fortes teneurs en éléments traces métalliques (ETMs) présents dans les déblais miniers entraînent généralement une forte réduction de la diversité végétale et microbienne. Selon les caractéristiques physico-chimiques des sols, la nature des métaux, leur concentration et leur spéciation, seules certaines espèces végétales et microbiennes ont développé des mécanismes particuliers et se sont adaptées à la présence d'ETMs. C'est le cas d'Anthyllis vulneraria et d'Hedysarum coronarium, deux Fabacées qui sont présentes sur d'anciennes mines de Zn/ Pb respectivement au sud de la France et au nord de la Tunisie. L'étude de l'absorption du Zn chez quatre sous-espèces d'A. vulneraria a montré que seule la sous-espèce carpatica présente sur l'ancienne mine Zn/Pb des Avinières, peut croître en présence de teneurs élevées en Zn et accumule des quantités élevées de ce métal sans montrer de symptômes de toxicité. Les données obtenues ont révélé qu'A. vulneraria sous espèce carpatica est une plante hypertolérante et accumulatrice de Zn. L'inoculation d'A. vulneraria avec ses bactéries symbiotiques fixatrices d'azote, Mesorhizobium metallidurans STM2683 (souche métallicole) et Mesorhizobium sp. STM2682 (souche non métallicole), a induit une diminution très significative de la teneur en Zn dans la plante. Par contre, seule la souche métallicole a montré un effet protecteur vis-à-vis des sous espèces sensibles d'A. vulneraria lorsque celles-ci sont exposées à une concentration modérée en Zn. La diversité phylogénétique et phénotypique des bactéries symbiotiques fixatrices d'azote associées à H. coronarium isolées du substrat de l'ancienne mine de Zn/Pb de Fej El Hdoum et du sol d'une parcelle agricole à El Krib a mis en évidence (i) l'appartenance de tous les isolats étudiés au genre Rhizobium, (ii) l'existence de différents niveaux de tolérance au Cd et l'absence de tolérance au Zn pour les isolats issus du substrat de Fej El Hdoum (iii) le lien étroit entre la présence de la plante hôte, H. coronarium et de sa bactérie symbiotique fixatrice d'azote sur un site donné. Ainsi, compte tenu des contraintes imposées par la présence des ETMs, l'utilisation de Fabacées en première séquence de végétation pour favoriser l'entrée d'azote et faciliter l'installation d'une couverture végétale stable et pérenne à même de phytostabliser les déblais miniers, rend indispensable la sélection des associations les mieux adaptées aux conditions environnementales locales. / High contents of trace metals present in waste rock mining causes a significant reduction in plant and microbial diversity. According to soil physico-chemical characteristics, metal nature, concentration and speciation, only some plant and strain species have developed specific mechanisms to cope with trace metal toxicity. This is the case of Anthyllis vulneraria and Hedysarum coronarium, two Fabaceae that are present on Zn / Pb ancient mines respectively in southern France and northern Tunisia. The Zn absorption study in four subspecies of A. vulneraria showed that only the carpatica subspecies, present on the Zn / Pb ancient mine of Les Avinières, can grow with high Zn concentrations and accumulate high levels of this metal without showing toxicity symptoms. Thus, A. vulneraria subsp. carpatica should be considered as a Zn-hypertolerant and accumulator plant. Inoculation of A. vulneraria with a nitrogen-fixing symbiotic bacterium, Mesorhizobium metallidurans STM2683 (metallicolous strain) or Mesorhizobium sp. STM2682 (non- metallicolous strain), induced a significant decrease of Zn content in the plant. However, only the metallicolous strain showed a protective effect for sensitive A. vulneraria subspecies when symbiotic plants were exposed to a moderate Zn concentration. Phenotypic and phylogenetic diversity of nitrogen-fixing symbiotic bacteria associated with H. coronarium isolated from the Zn / Pb ancient mine of Fej El Hdoum and an agricultural parcel of El Krib highlighted (i) that all studied isolates belong to the genus of Rhizobium, (ii) the existence of different Cd tolerance levels and the absence of Zn tolerance for isolates from the Fej El Hdoum substrate (iii) the close link between the presence of the host plant, H. coronarium and their symbiotic nitrogen-fixing bacteria on a given site. Thus, given the constraints imposed by heavy metals, the use of Fabaceae in a first sequence of vegetation to promote nitrogen entrance and facilitate the installation of a sustainable plant cover able to phytostabilise waste rock mining, necessitates the selection of the best adapted associations to local environmental conditions.

A deficiência de Zn no solo causa efeitos indesejáveis na produção agrícola, pois a baixa disponibilidade deste micronutriente para as plantas promove a diminuição da atividade enzimática, além da deficiência deste elemento na alimentação, que pode levar ao estado de subnutrição. Tendo em vista a problemática do Zn no sistema solo-planta e suas variações nos compartimentos do solo, é importante a avaliação de sua fitodisponibilidade e as frações do solo que este elemento está associado. O objetivo deste trabalho foi avaliar a fitodisponibilidade e a compartimentalização de Zn no solo, para as culturas de arroz (Oryza sativa L.) e soja (Glycine max L. Merrill) e avaliar o efeito das doses de Zn sobre a nutrição e exportação deste nutriente pela cultura. Utilizou-se como plantas teste as culturas de arroz e soja para avaliar o efeito das doses de Zn sobre a nutrição e translocação deste nutriente até os grãos. Para tanto, uma amostra de um Latossolo Vermelho, textura argilosa da região de Piracicaba (SP) foi utilizada e ZnCl2 (marcado com 65Zn) como fonte. O experimento foi conduzido em casa de vegetação em DIC, com cinco doses de Zn (0, 1, 2, 4 e 8 mg kg-1 de solo), com quatro repetições. O experimento foi conduzido até a formação de grãos e foi realizada determinação de Zn por Espectrômetria de Absorção Atômica após digestão nitroperclórica e contagem do 65Zn nas partes da planta: parte aérea (PA) e panícula (P), para arroz e PA, vagem (V) e grão (G), para soja. Calculou-se a quantidade de Zn proveniente da fonte (Znpf) nas partes das plantas e o aproveitamento do Zn da fonte pelas culturas (Ap). Nas amostras de solo foram realizadas extrações por DTPA (ZnDTPA) e Mehlich-1 (ZnM1) em duas subamostragens (t1 e t2), antes da semeadura e florescimento, respectivamente. O fracionamento de Zn foi realizado em amostras de t2 nas frações: trocável (ZnTroc); ligado a carbonatos (ZnCarb); a matéria orgânica (ZnMO); a óxidos (ZnOxi) e residual (Znres). Adicionalmente, foi realizada análise do teor pseudo-total de Zn (ZnPST). Os dados obtidos foram submetidos à análise de variância pelo teste-F a 95 % de probabilidade, ajuste das variáveis em função das doses por regressões e teste de média e análises de correlações entre as principais variáveis respostas. O Zn acumulado total na planta se ajustou à regressão linear em função do aumento das doses, entretanto ao analisar as partes separadamente, só houve diferença entre as doses para a variável PA em ambas as culturas. O Znpf total nas plantas apresentou incremento com a adição das doses crescentes de Zn ao solo, entretanto, eu aproveitamento foi baixo, 12 e 8,75 % para arroz e soja, respectivamente. As doses de ZnCl2 adicionadas ao solo, aumentaram a concentração de Zn presente nas frações ZnTroc > ZnMO > ZnCarb, em ordem decrescente. O Zn total acumulado nas plantas de arroz e soja apresentam correlações crescentes para os extratores DTPA e M1 nas duas subamostragens (t1 e t2), em função das doses avaliadas. O Zn extraído pelo DTPA ou M1, apresentaram correlação significativa com o Zn extraído nas frações, na ordem decrescente, ZnTroc > ZnCarb > ZnMO / Zn deficiency in soil causes undesirable effects on agricultural production because the low availability of this micronutrient for plants promotes the decrease in enzymatic activity besides the deficiency of this element in food, which can lead to a state of malnutrition. Considering the problem of Zn in soil-plant system and its variations in soil compartments, it is important to evaluate its bioavailability and forms in soil which this element is associated. The objective of this study was to evaluate Zn bioavailability and compartmentalization in the soil, to the rice (Oryza sativa L.) and soybean (Glycine max L. Merrill) crops and evaluate the effect of Zn levels on nutrition and exportation of this nutrient by the crops. As test plant rice and soybeans were used to evaluate the effect of Zn rates on nutrition and the nutrient translocation to the grains. For this purpose, a sample of an Oxisol (FAO), an clay texture from Piracicaba (SP) region, was used and ZnCl2 (labelled with 65Zn) as a source. The experiment was conducted in a greenhouse in CRD, with five rates of Zn (0, 1, 2, 4 and 8 mg kg-1 soil), with four repetition. The experiment was conducted until the formation of grains and Zn analyzis were performed by Atomic Absorption Spectrophotometery after nitricperchloric digestion and 65Zn counting of parts: shoot (PA) and panicle (P) for rice and PA, beans pods (Pd) and grains (G) for soybeans. The amount of Zn derived from the source (Znpf) was calculated in the plant parts and the recovery of the Zn by the crops (Ap). In the soil samples, extractions were performed by DTPA (ZnDTPA) and Mehlich-1 (ZnM1) methods in two sub samples (t1 and t2) prior to seeding and flowering, respectively. The Zn fractionation was performed on samples of t2 in the fractions: exchangeable (ZnTroc); linked to carbonates (ZnCarb); to organic matter (ZnMO); to oxides (ZnOxi) and residual (Znres). Additionally, analysis of the pseudo-total content of Zn (ZnPST) was performed. Data obtained was subjected to analysis of variance by the F-test at 95% probability, adjusting the variables depending on the rates for regression and average test and analysis of correlations between the main variables. The total cumulative Zn in the plant set to the linear regression in terms of increasing rates, however when analyzing the parts separately, just the PA showed differences between doses, for both crops. The total Znpf increased with the increasing rates, however its recoveries were low, approximately 12% for rice and 8.75 % for soybean. The ZnCl2 rates in soil increased the Zn concentration in the fractions: ZnTroc > ZnMO > ZnCarb, in descending order. The total cumulative Zn in the rice and soybean plants are growing correlations for extractors DTPA and M1 for two sub samples (t1 and t2), depending on the rates evaluated. The Zn extracted by DTPA or M1 were significantly correlated with Zn extracted in fractions in descending order: ZnTroc > ZnCarb > ZnMO

In dieser Arbeit wird die Machbarkeit der Herstellung von Leuchtdioden Strukturen (LEDs) in einzelnen GaN Nanodrähten (ND) und deren Integration mit herkömmlicher Si Technologie untersucht. Hierzu wird zunächst ein generelles Verständnis des Wachstums von GaN ND erarbeitet und dargestellt. Es folgen Untersuchungen zum Einfluss von Dotierstoffen, wie z.B. Mg und Si, auf das Wachstum der ND. Dieses Wissen wird anschließend angewandt um Dotierübergänge in GaN ND herzustellen die nominell n-i-p bzw. p-i-n dotiert sind. Diese Untersuchung brachte die technologisch wichtige Erkenntnis, dass eine p-Dotierung mit Mg am besten erreicht werden kann wenn die ND bereits wohl entwickelt sind. Dies bedeutet, dass der obere Teil der ND LEDs aus p-Typ Material bestehen wird. Eine weitere wichtige Komponente von LEDs ist die aktive Zone in der die Elektron-Loch-Rekombination stattfindet. Im Fall von planaren GaN LEDs wird diese durch Zugabe von In und die Formierung von InGaN hergestellt. Wir untersuchen das Wachstum von InGaN auf Si, GaN NDs und in Form von MQWs, um das Wachstum und insbesondere den In Gehalt unter vielen Bedingungen kontrollieren zu können. Das gesamte Wissen der Voruntersuchungen wird kombiniert und für das Ziel dieser Arbeit nutzbar gemacht: Die Herstellung von GaN ND basierten LEDs. Diese Strukturen werden untersucht und zu einer funktionierenden LED weiter prozessiert. Abschließend wird von den Anstrengungen zur Integration von III-Nitrid LEDs und Si basierter MOSFET Technologie berichtet. Es wird erstmalig erfolgreich die monolithische Integration dieser beiden Bauelemente und ihr gleichzeitiges Funktionieren gezeigt. / This work is concerned with the realization and investigation of a light emitting diode (LED) structure within single GaN nanowires (NWs) and its integration with Si technology. To this end first a general understanding of the GaN NW growth is given. This is followed by investigations of the influence which doping species, such as Mg and Si, have on the growth of the NWs. The experience gathered in these studies set the basis for the synthesis of nominal p-i-n and n-i-p junctions in GaN NWs. Investigations of these structures resulted in the technologically important insight, that p-type doping with Mg is achieved best if it is done in the later NW growth stage. This implies that it is beneficial for a NW LED to place the p-type segment on the NW top. Another important component of an LED is the active zone where electron-hole recombination takes place. In the case of planar GaN LEDs, this is usually achieved by alloying Ga and In to form InGaN. In order to be able to control the growth under a variety of conditions, we investigate the growth of InGaN in the form of extended segments on top of GaN NWs, as well as multi quantum wells (MQWs) in GaN NWs. All the knowledge gained during these preliminary studies is harnessed to reach the overall goal: The realization of a GaN NW LED. Such structures are fabricated, investigated and processed into working LEDs. Finally, a report on the efforts of integrating III-nitride NW LEDs and Si based metal-oxide-semiconductor field effect transistor (MOSFET) technology is given. This demonstrates the feasibility of the monolithic integration of both devices on the same wafer at the same time.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Nos últimos anos, a busca por fontes de energia renováveis e o desenvolvimento de novas tecnologias para a produção de biocombustíveis têm sido objeto de intensa investigação. O biodiesel é um combustível biodegradável, derivado de fontes renováveis e é obtido em escala industrial principalmente através da reação de transesterificação de óleos vegetais e/ou gorduras animais com metanol na presença de catalisadores homogêneos, como NaOH. Entretanto, a utilização de catalisadores heterogêneos tem sido sugerida por diversos autores, por apresentar vantagens como a eliminação dos problemas de separação e purificação dos produtos obtidos. No presente trabalho foi investigada a produção de biodiesel a partir da transesterificação do óleo de soja com metanol utilizando óxidos mistos de Zn e Al como catalisadores sólidos básicos. A influência das variáveis: temperatura, concentração de catalisador e relação molar metanol/óleo de soja na produção de biodiesel foi avaliada. Os catalisadores preparados apresentaram predominantemente sítios básicos e foram ativos frente à reação estudada, sendo os resultados mais promissores apresentados pelo óxido misto com relação molar Al/(Al+Zn)=0,50, obtido por tratamento térmico à 450C, que apresentou rendimentos em ésteres metílicos de até 98,5% sob condições específicas. A metodologia da superfície de resposta foi utilizada visando estabelecer as condições ótimas para maximizar o rendimento em ésteres metílicos, tendo sido encontradas a temperatura de 165oC e a concentração de catalisador de 5,8% m/m em relação massa de óleo, no caso da relação molar metanol/óleo de soja limitada em 15. Essa limitação teve como objetivo garantir um processo viável em escala comercial / Recently the search for renewable energy sources and new technologies for biofuel production have become the aim of several researches. Biodiesel is a biodegradable fuel, derived from renewable sources, and produced in industrial scale, mainly by the transesterification reaction of vegetable oils and/or animal fats with methanol, in the presence of homogeneous catalysts, such as NaOH. However the use of heterogeneous catalysts has been suggested by several authors, due to their great advantages, such as the elimination of separation problems and purification of the products. In the present work, the production of biodiesel from transesterification of soybean oil with methanol, using Zn,Al-mixed oxides as solid basic catalysts, was investigated. The influence of variables such as temperature, concentration of catalyst and methanol/soybean oil molar ratio on biodiesel production was evaluated. The catalysts prepared showed predominantly basic sites and were active for the studied reaction; and the most promising results, presented by the mixed oxide with Al/(Al + Zn) molar ratio = 0.50 obtained by heat treatment at 450C, showed methyl esters yields of up to 98.5%, under specific conditions. The response surface methodology was used to establish the optimum conditions to maximize methyl esters yield. Reaction temperature of 165oC and catalyst concentration of 5.8 wt% referred to mass of oil using methanol/soybean oil molar ratio limited by 15 were the optimum experimental conditions. This limitation had the goal to guarantee a viable commercial scale

<p>U radu je predložena modifikovana vatmetarska metoda za merenje snage gubitaka u toroidnim feritnim jezgrima koja je prilagođena osciloskopima male ulazne impedanse. Metoda je verifikovana na komercijalnim uzorcima od Mn-Zn i Ni-Zn feritnih materijala. Metoda je upotrebljena za merenje kompleksne permeabilnosti i gustine snage gubitaka dodatno obrađenih komercijalnih Mn-Zn feritnih prahova. Utvrđeno je da se dodatnim tehnološkim procesima (mlevenjem i prosejavanjem) početnog komercijanog praha mogu napraviti feritna jezgra manje gustine snage gubitaka i veće permeabilnosti.</p> / <p>The thesis proposes a modified Watt-meter method for measuring core loss of ferrite cores, which is adjusted to oscilloscopes with the small input impedance. The method is verified on comercial Mn-Zn and Ni-Zn ring cores. The method is used to measure the influence of starting powder sieving and milling on the core loss density and permeability of Mn-Zn ferrite. The experimental results and calculations show the significance of the additional milling and sieving process on magnetic properties of Mn-Zn ferrite in the frequency range from 0.1MHz to 10MHz. These processes increase the relative permeability about 3 times and decrease the core loss 4 times by milling of the starting powder.</p>

This research deals with the synthesis and characterization (transmission electron microscopy and optical spectroscopy) of composite nanocondensates produced by pulse laser ablation (PLA) on Zn, Zn-Cu and Cu-Au targets in liquid or vacuum. First, wurtzite-type (W)-ZnO and

L'objectif général de cette thèse est de mieux comprendre l'influence d'anciens sites miniers sur la contamination en métaux (Cd, Hg, Tl, Pb, Zn) et métalloïdes (As, Sb) de l'hydrosystème aval. Une attention particulière a été portée à l'antimoine (Sb), dont le comportement dans les cours d'eau contaminés par les drainages miniers reste mal connu et dont la signature isotopique pourrait permettre de tracer différentes sources et processus. Le site d'étude est le bassin des Gardons dans le Gard ; ce cours d'eau Cévenol draine de nombreux sites miniers abandonnés (Pb, Zn, Sb, charbon). L'enrichissement en métaux et métalloïdes a été étudié dans les sédiments actuels et anciens du bassin des Gardons. Un historique de la contamination métallique a été reconstitué à l'aide d'une archive sédimentaire. Les sources prépondérantes de métaux et métalloïdes dans les sédiments ont été déterminées ainsi que la mobilité potentielle de ces éléments vers la phase aqueuse. En complément, les variations de concentrations en métaux et métalloïdes dans les phases dissoute et particulaire ont été étudiées lors d'un épisode de crue grâce à un échantillonnage à haute résolution temporelle. Dans leur ensemble, les résultats montrent que les anciennes mines du bassin des Gardons contribuent à l'enrichissement en métaux et métalloïdes du cours d'eau aval, particulièrement en période de crue. Plus spécifiquement, le comportement de l'antimoine a été étudié dans un affluent du Gardon impacté par du drainage minier acide en aval de l'ancienne mine de Carnoulès et la composition isotopique de l'antimoine a été déterminée dans des eaux prélevées sur le bassin des Gardons et de l'Orb amont, après mise au point d'un protocole de purification/pré-concentration de Sb. Les résultats mettent en évidence le potentiel des isotopes de l'antimoine pour tracer l'origine de cet élément et les processus qu'il subit au cours de son transfert dans les cours d'eau impactés par du drainage de mine. / The overall objective of this thesis was to improve understanding of the influence of former mining sites on metal (Cd, Hg, Tl, Pb, Zn) and metalloid (As, Sb) contamination of the downstream hydrosystem. A special care was given to antimony (Sb), its behavior in mining-impacted streams remains poorly known and its isotopic signature could be usefull to track sources and processes. The study site is the Gardon River watershed in the south-east of France which drains many abandoned mining sites (Pb, Zn, Sb, coal). Metal and metalloid enrichment was studied in current and historical sediments of the Gardon River watershed. A sedimentary archive was used to investigate past metal contamination history. The prevailing metal and metalloid sources in sediments were determined together with the potential mobility of these elements toward the aqueous phase. In addition, dissolved and particulate metal and metalloid concentration variations were studied during a flood event using a high temporal resolution sampling. Altogether, the results suggest that former mining sites of the Gardon River watershed contribute to metal and metalloid enrichment of the downstream hydrosystem, especially during floods. More specifically, antimony behavior was investigated in a tributary of the Gardon River which is impacted by acid mine drainage originating from the disused Carnoulès mine and antimony isotopic composition was determined in waters collected in the Gardon River watershed and in the Upper Orb River after developing a protocol for preconcentrating and purifying Sb. The results highlight the potential of antimony isotopes to track the origin of this element and the processes that it undergoes during its transfer in streams impacted by mine drainage.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Nos últimos anos, a busca por fontes de energia renováveis e o desenvolvimento de novas tecnologias para a produção de biocombustíveis têm sido objeto de intensa investigação. O biodiesel é um combustível biodegradável, derivado de fontes renováveis e é obtido em escala industrial principalmente através da reação de transesterificação de óleos vegetais e/ou gorduras animais com metanol na presença de catalisadores homogêneos, como NaOH. Entretanto, a utilização de catalisadores heterogêneos tem sido sugerida por diversos autores, por apresentar vantagens como a eliminação dos problemas de separação e purificação dos produtos obtidos. No presente trabalho foi investigada a produção de biodiesel a partir da transesterificação do óleo de soja com metanol utilizando óxidos mistos de Zn e Al como catalisadores sólidos básicos. A influência das variáveis: temperatura, concentração de catalisador e relação molar metanol/óleo de soja na produção de biodiesel foi avaliada. Os catalisadores preparados apresentaram predominantemente sítios básicos e foram ativos frente à reação estudada, sendo os resultados mais promissores apresentados pelo óxido misto com relação molar Al/(Al+Zn)=0,50, obtido por tratamento térmico à 450C, que apresentou rendimentos em ésteres metílicos de até 98,5% sob condições específicas. A metodologia da superfície de resposta foi utilizada visando estabelecer as condições ótimas para maximizar o rendimento em ésteres metílicos, tendo sido encontradas a temperatura de 165oC e a concentração de catalisador de 5,8% m/m em relação massa de óleo, no caso da relação molar metanol/óleo de soja limitada em 15. Essa limitação teve como objetivo garantir um processo viável em escala comercial / Recently the search for renewable energy sources and new technologies for biofuel production have become the aim of several researches. Biodiesel is a biodegradable fuel, derived from renewable sources, and produced in industrial scale, mainly by the transesterification reaction of vegetable oils and/or animal fats with methanol, in the presence of homogeneous catalysts, such as NaOH. However the use of heterogeneous catalysts has been suggested by several authors, due to their great advantages, such as the elimination of separation problems and purification of the products. In the present work, the production of biodiesel from transesterification of soybean oil with methanol, using Zn,Al-mixed oxides as solid basic catalysts, was investigated. The influence of variables such as temperature, concentration of catalyst and methanol/soybean oil molar ratio on biodiesel production was evaluated. The catalysts prepared showed predominantly basic sites and were active for the studied reaction; and the most promising results, presented by the mixed oxide with Al/(Al + Zn) molar ratio = 0.50 obtained by heat treatment at 450C, showed methyl esters yields of up to 98.5%, under specific conditions. The response surface methodology was used to establish the optimum conditions to maximize methyl esters yield. Reaction temperature of 165oC and catalyst concentration of 5.8 wt% referred to mass of oil using methanol/soybean oil molar ratio limited by 15 were the optimum experimental conditions. This limitation had the goal to guarantee a viable commercial scale