Dissertations / Theses on the topic 'Molten aluminium material'

Aluminium die casting is a process used to transform molten aluminium material into automotive gearbox housings, wheels and electronic components, among many other uses. It is used because it is a very efficient method of achieving near net shape with the required mechanical properties. Life Cycle Assessment (LCA) is a technique used to determine the environmental impacts of a product or process. The Life Cycle Inventory (LCI) is the initial phase of an LCA and describes which emissions will occur and which raw materials are used during the life of a product or during a process. This study has improved the LCI technique by adding in manufacturing and other costs to the ISO standardised methods. Although this is not new, the novel application and allocation methods have been developed independently. The improved technique has then been applied to Aluminium High Pressure Die Casting. In applying the improved LCI to this process, the cost in monetary terms and environmental emissions have been determined for a particular component manufactured by this process. A model has been developed in association with an industry partner so this technique can be repeatedly applied and used in the prediction of costs and emissions. This has been tested with two different products. Following this, specialised LCA software modelling of the aluminium high pressure die casting process was conducted. The variations in the process have shown that each particular component will have different costs and emissions and it is not possible to generalise the process by modelling only one component. This study has concentrated on one process within die casting but the techniques developed can be used across any variations in the die casting process.

Orientador: Maria Helena Robert
Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecanica
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Resumo: Neste trabalho investiga-se a influência da microestrutura inicial e do material do molde na tixoconformação da liga A356. São produzidas e testadas em operações de tixoforjamento pastas obtidas por três distintos processos: fusão parcial controlada de estrutlJ'aS dendríticas grosseiras, fusão parcial controlada de estruturas ultra-refinadas e pastas obtidas por agitação mecânica do líquido durante solidificação. É produzido ainda um compósito A356 + Ab03 obtido por compofundição. Os tixoforjados foram submetidos à análise metalográfica para caracterização microestrutural, medindo-se a fração da fase primária e o tamanho médio de glóbulo ou roseta da fase sólida. Os resultados obtidos mostram a viabilidade da utilização de moldes não metálicos e operações de tixoconformação com produtos de bom acabamento superficial e dimensional. As forças de tixoforjamento são dependentes da condição inicial da matéria-prima, de forma que forças maiores são requeridas com o aumento do parâmetro microestrutural básico (espaçamento interdendrítico, tamanho de glóbulo e tamanho de roseta) da matéria-prima
Abstract: This research aims the influence of initial microstructure and die material on thixofonning of A356 alloy. Obtained slurries are produced and tested in thixoforging operation by three distinct processes: controlled partial melting of coarse dendritic structures, controlled partial melting of ultra-refined structures and obtained slurries by liquid mechanical stirring during solidification. It is still produced a composite A356 + AbO:i obtained by compocasting. Thixoforged samples were submitted to metalographic analysis for microstructural characterisation, measuring the primary phase fraction and globule average size or 50lid phase rosette. Obtained results showed the viability of non-metallic dies in thixoforming operations with good superficial and dimensional finishing produds. Thixoforging forces are dependent on initial condition of raw material, 50 that higher forces are required with the increasing of basic microstructural parameter Onterdentritic spacing, globule size and rosette size) of raw material
Mestrado
Materiais e Processos de Fabricação
Mestre em Engenharia Mecânica

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 1987.
MICROFICHE COPY AVAILABLE IN ARCHIVES AND SCIENCE.
Bibliography: leaves 178-188.
by Seok-Yeol Yoon.
Ph.D.

Thesis: Ph. D., Massachusetts Institute of Technology, Department of Materials Science and Engineering, 2018.
This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Cataloged from student-submitted PDF version of thesis.
Includes bibliographical references.
The electrolytic cell method and its application for Gibbs energy measurement in high temperature, concentrated ionic melts was investigated. Previous challenges related primarily to signal interpretation during decomposition voltage measurement have hindered determination of Gibbs energy. An electrolytic cell method is proposed herein utilizing the sensitivity of large amplitude alternating current voltammetry, which enabled precise measurement of chemical potential during electrolytic decomposition. A novel, containerless approach for electrochemical study of high temperature, reactive electrolytes in a molten pendant droplet is described. For the first time, melts of pure alumina, lanthana and yttria were electrolytically decomposed to metal alloy and oxygen gas using iridium electrodes. The method was validated in molten alumina. Systematic investigation of the half-cell reactions corresponding to oxygen evolution and aluminum deposition revealed their electrochemical nature. Measurements of the chemical potential and partial molar entropy of aluminum in an iridium-rich, binary alloy liquid were obtained in close agreement with previous predictions. The method was extended to the pseudo-binary system molten lanthana-yttria. The results revealed selective extraction of lanthanum and indicated that molten lanthana-yttria does not exhibit ideal mixing behavior, contradicting previous predictions. However, data interpretation in multicomponent electrolyte compositions were challenged primarily by a lack of thermodynamic data for the attendant alloy system and influence of dissolved oxygen on the observed alloy composition. This work represents a pioneering effort for electrochemical operation in molten refractory oxides at temperatures above 2000 K.
by Bradley Rex Nakanishi.
Ph. D.

Thesis: S.B., Massachusetts Institute of Technology, Department of Materials Science and Engineering, 2016.
Cataloged from PDF version of thesis.
Includes bibliographical references (pages 33-34).
One of the key limitations in the wide-scale adoption of mature renewable energy technologies is the lack of grid-level energy storage solutions. One important figure of merit in these battery systems is a high rate capability to match fluctuating demands for electricity. Molten salt batteries are an attractive option for stationary storage due to fast kinetics and good cycling capability, but high temperatures (>300 °C) limit available materials. In this thesis, the molten NaCl-AlCl3-SnCl2 electrolyte and liquid Sn electrode couple at 250 °C is investigated as part of the potential cell Na I NaCl-AlCl 3-SnCl2 I Sn for a lower temperature molten salt battery. An electrochemical study of the kinetics in the molten salt electrolyte and at the liquid Sn electrode-electrolyte interface is conducted using cyclic voltammetry and the galvanostatic pulse method. The liquid metal electrode is found to have suitably fast kinetics with an exchange current density of 92 mA/cm2. Parameters for a new Na+ conducting membrane are proposed, requiring an ionic conductivity of 0.056 S/cm, which would allow for a hypothetical Na I NaCl-AlC 3-SnCl2 I Sn battery to operate with an energy efficiency of 70%.
by Raku Watari.
S.B.

Tese (doutorado) - Universidade Federal de Santa Catarina, Centro Tecnológico, Programa de Pós-Graduação em Ciência e Engenharia de Materiais, Florianópolis, 2010
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Este trabalho apresenta uma metodologia para obtenção de óxido de alumínio nanoporoso em substratos de alumínio obtidos de diferentes processos metalúrgicos e de diferentes graus de pureza do substrato, utilizando a técnica de oxidação anódica (anodização). Para realização dos trabalhos, foi montado um sistema eletroquímico de anodização com temperatura controlada e adaptável aos vários tipos de eletrodos de alumínio. Os produtos obtidos apresentaram excelentes qualidades para uso como moldes para deposição de materiais nanoestruturados. As estruturas de alumina foram caracterizadas por técnicas de microscopia eletrônica de varredura e de transmissão. O preenchimento dos poros da alumina foi realizado por técnicas de eletrodeposição em modo pulsado (de corrente e de potencial) em soluções de sulfatos de ferro, níquel e cobalto, de onde foram produzidos nanofios de ligas magnéticas. Algumas estruturas de alumina preenchidas pelas ligas foram caracterizadas por magnetometria de amostra vibrante, de onde foram obtidas informações a respeito da qualidade morfológica do próprio molde de alumina. Também foi realizado um estudo do comportamento resistivo das estruturas compósitas de alumina e nanofios mediante aplicação de tensões elétricas. A caracterização dos nanofios, extraídos após a dissolução dos moldes de alumina, foi obtida por microscopia eletrônica de varredura e de transmissão.

La thèse s’inscrit dans le cadre d’un projet de recherche visant à élaborer une anode permettant le dégagement d’oxygène en milieu de cryolithe fondue à 960°C et dont l’utilisation supprimerait les émissions de dioxyde de carbone du procédé de production d’aluminium Hall-Héroult. Le type d’anode envisagée est un composite Cermet (CERamique – METal), généralement constitué d’une phase métallique à base de nickel, cuivre et fer et d’une ou plusieurs phase(s) oxyde(s) conductrice(s) du type NixFe3-xO4 et Ni1-xFexO. Deux types de cermet, biphasé et triphasé, ont été étudiés dans le cadre de ce projet. L’objectif principal a été de comprendre les mécanismes de dégradation de telles anodes durant les électrolyses. Les cermets ont été testés sous une densité de courant de 0,80 A/cm² pour différentes durées, puis analysés par microscopie optique et microscopie électronique à balayage couplée à une analyse dispersive en énergie. Les premières électrolyses, effectuées dans un électrolyte synthétique, sans aluminium métallique et sous atmosphère argon ont révélé à la fois une dégradation chimique et électrochimique. L’étude de la dégradation chimique a été réalisée grâce à des immersions dans l’électrolyte sans polarisation. Les résultats ont mis en évidence une dissolution de la phase spinelle, liée à un phénomène de substitution entre les ions Al3+ de l’électrolyte et Fe3+ du spinelle, entrainant la formation d’un aluminate du type NixFe3-x-yAlyO4. Lorsque x = 0 et y proche de 2, la phase spinelle est dissoute alors que lorsque x est proche de 1, la phase spinelle est stabilisée et sa dissolution ralentie. Les électrolyses menées jusqu’à la fin de vie des matériaux ont révélé l'attaque préférentielle de la phase métallique pour former des composés fluorés et oxydes. Grâce aux caractérisations micrographiques et aux calculs thermodynamiques (logiciel FactSage 7.1), un mécanisme de dégradation global des anodes a été proposé. La compréhension des mécanismes de dégradation chimique et électrochimique des matériaux a permis de proposer des voies d'amélioration concernant à la fois le matériau d'anode et la chimie du bain cryolithique
The thesis is a part of a research project which develop an anode permitting the release of oxygen in molten cryolite medium at 960°C, in order to eliminate carbon dioxide emissions from the aluminium production process called Hall-Héroult process. The type of anode envisaged is a Cermet composite (CERamic - METal), generally consisting of a metallic phase based on nickel, copper and iron and one or more conductor oxide phase(s) such as NixFe3-xO4 and Ni1-xFexO type. Two types of cermet, two-phase and three-phase, have been studied in this project. The main objective was to understand the degradation mechanisms of such anodes during electrolysis. The cermets were tested at a current density of 0.80 A/cm² for different durations and analyzed by optical microscopy and scanning electron microscopy coupled with dispersive energy analysis. The first electrolyses, carried out in a synthetic electrolyte, without metallic aluminum and under argon atmosphere revealed both chemical and electrochemical degradations. Study of chemical degradation was carried out thanks to immersions in the electrolyte without polarization. The results showed a dissolution of the spinel phase, linked to a substitution phenomenon between the Al3+ ions from the electrolyte and Fe3+ from spinel, resulting in the formation of a NixFe3-x-yAlyO4 aluminate type. When x = 0 and y close to 2, the spinel phase is dissolved whereas when x is close to 1, the spinel phase is stabilized and its dissolution slowed down. Electrolyses conducted to the end of life of the materials revealed the preferential attack of the metal phase to form fluorinated compounds and oxides. Thanks to micrographic characterizations and thermodynamic calculations (FactSage 7.1 software), a global degradation mechanism of the anodes has been proposed. The understanding of the chemical and electrochemical degradation mechanisms of the materials made it possible to propose ways of improvement concerning both the anode material and the cryolithic bath chemistry

Orientador: Rezende Gomes dos Santos
Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecanica
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Resumo: Este trabalho apresenta uma análise experimental da influência do material e da geometria do molde em parâmetros térmicos e estruturais durante a solidificação de ligas alumínio-cobre. Para tanto placas e cilindros das ligas Al-4,5%Cu e Al-15%Cu foram solidificadas em moldes de areia e de aço. Foram obtidas, através de um sistema de aquisição de dados, as curvas de resfriamento em diferentes posições nas peças e na superfície externa dos moldes. Os resultados obtidos permitiram a determinação dos tempos de solidificação nas diferentes condições analisadas. Através de análise metalográfica foi possível determinar a influência da geometria e do material do molde na formação da macroestrutura e da microestrutura durante o processo de solidificação. Um modelo numérico para simulação do processo de solidificação em moldes maciços foi desenvolvido e otimizado. Alguns resultados obtidos com a aplicação do modelo, comparados com resultados experimentais, são apresentados
Abstract: This work presents an experimental analysis of the influence of material and geometry of mold in thermal and structural parameters during solidification of aluminum-copper alloys. Slabs and cylinders of Al-4.5wt%Cu and Al-15wt%Cu alloys were solidified in sand and steel molds. Curves of the variation of temperature in different positions in the solidifying alloy and on the external surface of the mold were determined. From the results solidification times were estimated for all cases analyzed. From metallographic analysis of the influences of geometry and mold material on macrostructure and microstructure were determined. A numerical model to analyze the solidification of alloys in massive molds was developed. Examples of the application of the model compared with experimental results are shown
Mestrado
Materiais e Processos de Fabricação
Mestre em Engenharia Mecânica

Orientador: Maria Odila Hilário Cioffi
Coorientador: Marcos Yutaka Shiino
Banca: Herman Jacobus Cornelis Voorwald
Banca: Rita de Cássia Mendonça Sales Contini
Resumo: O aumento do uso de compósitos estruturais tem levado a uma preocupação constante com a confiabilidade destes materiais. Em particular, o processo de cura das resinas na fabricação é citado como um dos problemas mais significativos no processamento de compósitos estruturais. Assim, para que essa classe de materiais possa ser economicamente viável e atender às exigências dos padrões de qualidade do setor aeronáutico, tecnologias de processamento automatizado e novas formas de matéria-prima estão sendo desenvolvidas e implantadas na fabricação. Desta forma, o objetivo da presente pesquisa foi estudar a influência das propriedades térmicas dos materiais de moldes, utilizados no processamento de compósitos via RTM, nas propriedades finais dos laminados. Foram processadas três placas de compósitos com reforço não dobrável (NCF-non-crimp fabric) biaxial [+45°/-45°] via RTM: em molde de aço 1020, laminado 1; e em liga de alumínio 5052-F, laminados 2 e 3. Para verificar a influência dos materiais dos moldes nas propriedades finais, foram analisadas a tenacidade à fratura interlaminar em modo I e investigação das superfícies de fratura pelo Microscópio Eletronico de Varredura (MEV). O comportamento térmico estudado via análise térmica dinâmico-mecânica (DMA), que avaliou as diferenças no grau de cura dos laminados 1, 2 e 3 com a análise da Tg. Nos processamentos, evidenciou-se que o molde de alumínio apresentou maior controle e estabilidade térmica, enquanto que o molde de aço aprese... (Resumo completo, clicar acesso eletrônico abaixo)
Abstract: The increase use of structural composites has led to a constant concern on the reliability of these materials. In particular, curing process of resins during manufacturing are cited as one of the most significant problems in the structural composites. Therefore, in order to this class of materials can be economically viable and meet the requirements of quality in the aeronautic industry standards, automated processing technologies and new materials have been developed and implemented in manufacturing sector. Thus, this research aimed to investigate the influence of thermal properties of the mold, which was used in the processing of composites via RTM, on the final properties of the laminates. Three composite plates comprised with NCF (non-crimp fabric) reinforcement, which has biaxial [+45°/-45°] configuration, and epoxy matrix. Two molds were employed for this investigation: steel 1020, for laminate 1, and aluminum alloy 5052-F, for laminates 2 and 3, all laminates with the same fiber stacking sequence. The influence of the materials of the molds in the final properties were verified with interlaminar fracture toughness in mode I (GIc), and their images of the fractured surfaces investigated by Scanning Electron Microscope (SEM). The thermal analysis conducted with Dynamic Mechanical Thermal Analysis (DMA), which evaluated the differences in the degree of cure of laminate 1, 2 and 3 by vitreous temperature transitions (Tg). It was evidenced that the aluminium mold showed bet... (Complete abstract click electronic access below)
Mestre

Sélectionner des traitements de surface pour l’industrie nécessite de prendre en compte :les propriétés à conférer au substrat, la nature et la géométrie de celui-ci et les caractéristiques du milieu extérieur. Certaines combinaisons de ces paramètres rendent difficile la sélection d’un traitement unique, d’où le recours à des multitraitements de surface. Dès lors, se posent les questions suivantes :

- Utiliser des multitraitements de surface peut se faire en scindant les différentes requêtes en sous-ensembles, de manière à ce que chaque traitement réponde à l’un d’eux. Dans quel ordre ces requêtes doivent-elles être introduites par rapport au substrat ?

- Comment sélectionner les traitements de surface répondant à chaque requête individuelle ?

- Comment classer des multitraitements en termes d’adéquation au problème posé ?

Dans ce travail, les première et troisième questions sont abordées, en explorant les requêtes concernant habituellement les dispositifs de moulage de l’aluminium :

- Résistance aux contraintes d’origine thermique.

- Résistance à la corrosion par les métaux fondus.

- Résistance au frottement.

L’analyse de la bibliographie relative aux traitements de surface utilisés dans ces systèmes a été analysée et des « architectures »-types ont été identifiées (chapitre 3). On prévoit, par exemple, un traitement conférant la résistance à la fatigue superficielle, ainsi qu’un revêtement étanche et résistant à l’aluminium fondu. Une barrière thermique est parfois préconisée.

Pour chacune des architectures, des traitements de surface individuels peuvent être sélectionnés. Un « facteur de performance » permettant de classer les solutions par rapport au problème de la fatigue thermique a été construit (chapitre 4) et discuté dans deux situations :

- Lorsqu’un revêtement est présent, et que les contraintes d’origine thermique (différence de dilatation thermique couche-substrat) menacent de le rompre lors de l’immersion dans un milieu corrosif à haute température. Des essais de corrosion dans de l’aluminium fondu ont été réalisés sur un acier revêtu par du nitrure de chrome dopé à l’aluminium, synthétisé par déposition physique en phase vapeur (chapitre 5 – collaboration :Inasmet).

- Lorsque des variations thermiques rapides menacent de rompre le substrat et la (les) couches. Des essais de fatigue thermique ont été réalisés sur de l’acier à outils pour travail à chaud non traité, boruré ou recouvert d’un multitraitements (zircone yttriée / NiCrAlY / boruration / acier). Le revêtement en zircone yttriée a été obtenu par projection par plasma. L’essai de fatigue thermique a été modélisé et le facteur de performance, discuté (chapitre 6).

Au chapitre 7, les architectures-types ont été introduites dans une méthodologie de sélection des multi-traitements de surface, qui a été appliquée dans deux cas :

- Celui des moules de fonderie, devant résister à la fatigue thermique et à la corrosion par l’aluminium fondu. Le facteur de performance a été extrapolé à d’autres situations qu’aux chapitres 5 et 6. Les solutions habituellement proposées pour résoudre ce problème sont retrouvées.

- Celui de deux pièces en acier frottant l’une contre l’autre en présence d’aluminium fondu.

To select surface treatments, one must account for the required functional properties, the substrate features and the solicitations the substrate must endure. Certain combinations of these parameters make it difficult to select a single surface treatment, a reason why several successive treatments are preferred. To select them, one needs to determine:

- How to divide the several requests into groups and how to stack up these groups from the substrate to the outer surface, so that each treatment deals with one specific group of requests/properties.

- How to select individual layers for each group of properties.

- How to rank the multi-treatments in terms of relevance for a given application.

In this work, one tries to answer the first and the third questions, by studying the case of aluminium foundry, in which the industrial devices frequently face the following solicitations:

- Thermal stress (thermal fatigue, thermal expansion mismatch).

- Presence of corrosive molten metal.

- Sliding wear.

In the literature, several “standard” architectures are proposed (chapter 3), like a diffusion layer reducing superficial fatigue plus a corrosion barrier layer. A thermal barrier coating is also sometimes proposed.

For each of these architectures, one can select individual treatments. To rank them, one devised a “performance index” for thermal stress (chap.4), which is discussed for two cases:

- For large differences between layer and substrate thermal expansion coefficients, when both are put into contact with a high temperature corrosive medium, the layer may be damaged. One discusses this case by examining the corrosion caused by molten aluminium for a steel substrate coated by anticorrosive chromium nitride doped with aluminium. The layer is produced by physical vapour deposition (chap. 5 – cooperation: Inasmet).

- Repeated fast surface temperature transients can also damage the substrate and/or the layer by thermal fatigue. One conducted thermal fatigue tests with samples of hot work tool steel, respectively untreated, simply borided and protected by a multilayer. In the last case, top coat is yttria stabilised zirconia, followed by a nickel superalloy and then a borided layer (undercoat). One synthesized the zirconia coating by plasma spray and one modelled the thermal fatigue (chap. 6).

In chap. 7, architectures from chap. 2 are introduced in a multi-treatment selection routine, which is applied in two cases:

- Foundry moulds for molten aluminium, withstanding both thermal fatigue and corrosion. The devised performance index is extrapolated beyond the tests of chap. 5 and 6 to treatments for this industrial application, thereby quantifying their respective merits.

- A foundry device exposed to molten metal and sliding wear.

Doctorat en Sciences de l'ingénieur
info:eu-repo/semantics/nonPublished

Proučavane su koroziona postojanost i tendencija lepljenja različitihmaterijala u kontaktu sa tečnom Al–Si–Cu legurom. Ispitivanjem suobuhvaćeni čelik za rad na toplo, plazma nitrirani čelik i dupleksslojevi sa CrN, TiAlN, TiAlSiN i CrAlN prevlakama, različitog nivoapovršinske hrapavosti. Za ispitivanja pomenutih fenomenaprimenjena je metoda izvlačenja, koja je unapređena kako bi se povećalenjena tačnost i verodostojnost simulacije procesa livenja. Korozioniefekti su pojačani tako što su uzorci osim kratkog kontakta sa odlivkomzadržavani i u dužim periodima u kontaktu sa tečnom legurom (5 i 20min). Uprkos opštim stavovima, za ispitivane materijale jeustanovljeno da su sile izvlačenja uzoraka iz Al–Si–Cu odlivakanezavisne od njihovog hemijskog sastava. Uticaj hrapavosti je izraženkod uzoraka sa prevlakama kod kojih pri smanjenju hrapavosti dolazi dopovećanja sile izvlačenja. Sve ispitane prevlake su sklone mehaničkomlepljenju Al–Si–Cu legure za svoje površine, ali sa aspekta korozije utečnom metalu značajno prevazilaze performanse čelika i plazmanitriranog sloja. Duži kontakt livene legure sa površinama prevlakauzrokovao je niže vrednosti sila izvlačenja, što je posledicaoksidacije površina prevlaka. Ustanovljeno je da su ispitivaneprevlake inertne ka tečnoj leguri aluminijuma. Međutim, dolazi dooksidacije i korozije materijala podloge kroz greške rasta koje suprisutne u prevlakama. Stečena znanja o identifikovanimmehanizmima habanja i propadanja zaštitnih slojeva prevlakaposlužiće daljem razvoju dupleks slojeva namenjenih za zaštitu alataza livenje pod pritiskom.
Corrosion resistance and soldering tendency of different materials in moltenAl–Si–Cu alloy were studied. Hot-working tool steel, plasma nitrided steel andduplex layers with CrN, TiAlN, TiAlSiN and CrAlN top coatings, which wereproduced to various degree of surface roughness, were covered by the study.An ejection test was employed for investigation of the concerned phenomena.The ejection test was improved in order to increase its accuracy and thereliability of process simulation. Samples were examined in both short andextended periods of contact (5 and 20 min) with liquid casting. Castingsolidification was extended in order to intensify the corrosion effects. Contraryto common findings, it was found that the ejection force of the investigatedmaterials does not depend on their chemical composition. For the coatedsamples, a pronounced dependence of the ejection force on the surfaceroughness was found. The ejection force increases with decrease in surfaceroughness. All investigated coatings are prone to mechanical soldering by Al–Si–Cu alloy. Still, their corrosion resistance substantially exceeds the corrosionresistance of steel and plasma nitrided layer. Longer exposure of coatedsamples to cast alloy induced lower ejection forces, which is a consequenceof coatings oxidation. It was found that the investigated coatings are inert toliquid aluminium. However, the underlying material undergoes oxidation andcorrosion through coating growth defects. The findings concerning the wearmechanisms of protective layers support further development of duplex layersintended for die casting tools protection.

The traditional aluminum production process (Hall-Héroult process) involves electrolyzing the alumina dissolved in the molten cryolite salt. This process is energy intensive and emits massive amounts of CO2 and other greenhouse gases. The market demand of aluminum and the environmental impact of the current aluminum production process justify research and development of alternative electrolytic processes for aluminum production that can both reduce the cost and eliminate adverse environment impacts. Solid oxide membrane (SOM) based electrolysis process is an innovative technology that has been demonstrated to successfully produce many energy-intensive metals directly from their oxides in an efficient, economical and environmentally sound way. During the SOM electrolysis process, an oxygen-ion-conducting SOM tube made of ytteria-stabilized zirconia (YSZ) separates the pre-selected molten flux with dissolved metal oxide from the inert anode assembly inside the YSZ tube. When the applied DC potential between the cathode and the anode exceeds the dissociation potential of desired metal oxide, the metal is reduced at the cathode while oxygen ions migrate through the YSZ membrane and are oxidized at the anode. Employing the inert anode allows the oxygen to be collected at the anode as a value added byproduct. In this work, a zero-direct-carbon-emission aluminum production process utilizing SOM electrolysis is presented. The molten flux used in the electrolysis process is optimized through careful measurements of its physio-chemical properties. The liquidus temperature, volatilization rate, alumina solubility, aluminum solubility, YSZ membrane degradation rate and electrical conductivity of various flux compositions were measured, and the flux chosen for SOM electrolysis was a eutectic MgF2-CaF2 system containing optimized amounts of YF3, CaO and Al2O3. Laboratory scale SOM electrolysis employing the inert anode were performed at 1100 ~ 1200oC to demonstrate the feasibility of producing and collecting aluminum while producing pure oxygen as a byproduct. The aluminum product was characterized by scanning electron microscopy (SEM) and energy dispersive x-ray spectroscopy (EDS). An equivalent circuit model for the electrolysis process was developed in order to identify the polarization losses in the SOM electrolysis cell.
2016-12-21T00:00:00Z