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Aluminium-induced impairment of Ca2+ modulatory action on GABA transport in brain cortex nerve terminals

Cordeiro, J. M.; Silva, V. S.; Oliveira, C. R.; Gonçalves, P. P.
Fonte: Universidade de Coimbra Publicador: Universidade de Coimbra
Tipo: Artigo de Revista Científica Formato: aplication/PDF
ENG
Relevância na Pesquisa
37.23%
The [gamma]-aminobutyric acid (GABA) is the major inhibitory neurotransmitter in vertebrate CNS. At GABAergic synapses, a high-affinity transporter exists, which is responsible for GABA reuptake and release during neurotransmission. GABA transporter activity depends on the phosphorylation/dephosphorylation state, being modulated by Ca2+/calmodulin-dependent protein phosphatase 2B (calcineurin). Aluminium is known to interfere with the Ca2+/calmodulin signalling pathway. In this work, we investigate the action of aluminium on GABA translocation mediated by the high-affinity transporter, using synaptic plasma membrane (SPM) vesicles and synaptosomes isolated from brain cortex. Aluminium completely relieved Ca2+ downregulation of GABA transporter, when mediating uptake or release. Accordingly, aluminium inhibited Ca2+/calmodulin-dependent calcineurin activity present in SPM, in a concentration-dependent manner. The deleterious action of aluminium on the modulation of GABA transport was ascertained by comparative analysis of the aluminium effect on GABA uptake and release, under conditions favouring SPM dephosphorylation (presence of intracellular micromolar Ca2+) or phosphorylation (absence of Ca2+ and/or presence of W-7, a selective calmodulin antagonist). In conclusion...

Influência do alumínio e do pH ácido sobre a fisiologia reprodutiva de peixes teleósteos continentais; Influence of aluminium and acidic pH over the reproductive physiology of freshwater teleost fish

Correia, Tiago Gabriel
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 05/05/2008 PT
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37.21%
A reprodução em peixes é controlada pelo eixo hipotálamo-hipófise-gônadas e os fatores que alteram o funcionamento adequado deste eixo são chamados de disruptores endócrinos. Muitos metais têm o papel de disruptores endócrinos e dentre eles destaca-se o alumínio que, além de afetar o sistema endócrino de algumas espécies de peixes, pode alterar a deposição e/ou mobilização de substratos energéticos nestes animais. Sabe-se que o pH pode modular em muitos casos as respostas fisiológicas decorrentes da exposição de peixes a alguns metais, como é o caso do alumínio. Desta forma, o presente trabalho objetiva avaliar as possíveis alterações na fisiologia reprodutiva de duas espécies de peixes teleósteos continentais quando os mesmos são expostos às altas concentrações de alumínio e em pH ácido. Para avaliar estes efeitos foram conduzidos 2 tipos de experimentos: um crônico, realizado com fêmeas de uma espécie de desova total (sincrônica em grupo), Astyanax fasciatus (lambari), durante a sua fase reprodutiva, pelo período de 14 dias; e outro agudo, pelo período de 96 horas, com fêmeas de Oreochromis niloticus (tilápia), espécie de desova parcelada (assincrônica) também em fase reprodutiva. Foram determinadas as concentrações plasmáticas de hormônios esteróides como o cortisol...

Proteção contra a corrosão de ligas de alumínio com recobrimentos à base de cério e polímero condutor; Corrosion protection of aluminium alloys by cerium-based and conducting polymer coatings

Johansen, Herbert Duchatsch
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 11/11/2013 PT
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37.18%
As ligas de alumínio vêm sendo amplamente usadas nas indústrias aeronáuticas e automobilísticas por suas propriedades mecânicas superiores às do metal puro. Entretanto, como as propriedades de corrosão dessas ligas variam, sendo piores do que as do alumínio puro, surge a necessidade de estudos de diferentes métodos de proteção contra a corrosão. O uso de coberturas protetoras é uma alternativa para diminuir os processos corrosivos e, desta maneira, aumentar a vida útil desses materiais. Das coberturas de conversão existentes, as mais usadas ainda são à base de cromo, porém o cromo tem se mostrado danoso ao meio ambiente e à saúde humana. Por outro lado, as coberturas de conversão à base de óxidos de cério, ambientalmente mais corretas e menos nocivas, já têm sido usadas com sucesso para este propósito. Ademais, partindo do consenso sobre o bom desempenho da polianilina (PAni) em proteger metais oxidáveis contra a corrosão, inclusive o alumínio e suas ligas, o presente estudo propõe o desenvolvimento de proteção anticorrosiva de ligas de alumínio pela combinação de camadas de conversão à base de óxidos de cério associada com camadas de PAni nas ligas de alumínio das séries AA1xxx e AA6xxx. A combinação de camadas duplex surge como uma alternativa promissora por: (i) possibilitar a formação de pontos de ancoragem sobre a superfície...

Expressão de genes da ferritina e resposta antioxidante em duas cultivares de Coffea arabica expostas a ferro e aluminio; Ferritin gene expression and antioxidant response of two Coffea arabica cultivars exposed to iron and aluminium

Alexandra Bottcher
Fonte: Biblioteca Digital da Unicamp Publicador: Biblioteca Digital da Unicamp
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 10/02/2009 PT
Relevância na Pesquisa
37.08%
A ferritina é uma proteína que armazena átomos de ferro (Fe) em uma forma não tóxica, controlando o nível desse metal nas células. Em humanos, a ferritina também é capaz de se ligar ao alumínio (Al), evitando sua toxicidade. Como o cafeeiro consegue crescer adequadamente em solos ácidos, com níveis elevados de Al, e células em suspensão tratadas com esse mesmo metal têm expressão aumentada de genes que codificam para ferritina, há a possibilidade dessa proteína se complexar ao Al também em plantas. Na indução da síntese da ferritina em suspensões celulares de Coffea arabica cv. Mundo Novo com 300 e 1.200 µmol/L de sulfato ferroso observou-se um aumento de 8,9 e 18,2 vezes, respectivamente, do RNAm CaFer1 da ferritina, em relação ao controle. Já o tratamento com 5 mmol/L de sulfato de alumínio-potássio resultou na diminuição de 4,57 vezes na expressão desse gene, em relação ao controle. Para Coffea arabica cv. Icatu, todos os tratamentos resultaram na queda da expressão de CaFer1, sendo que essa diminuição foi de 29,0 e 6,3 vezes para as células tratadas com 300 e 1.200 µmol/L de sulfato ferroso, respectivamente, e de 98,0 vezes para o tratamento com 5 mmol/L de sulfato de alumínio-potássio, em relação ao controle. Esses mesmos tratamentos não induziram...

Factors affecting the metal recovery yield during induction melting of aluminium swarf

Puga, Hélder; Barbosa, J.; Ribeiro, Carlos Silva
Fonte: Trans Tech Publications Publicador: Trans Tech Publications
Tipo: Artigo de Revista Científica
Publicado em //2013 ENG
Relevância na Pesquisa
37.18%
Machining operations of cast parts usually generate considerable amounts of waste in the form of chips (usually 3–5% of the casting weight). Traditionally, swarf is sold to scrapers and remelters, but this option is quite expensive because the selling price is roughly 30% of the acquisition price of the commercial 2nd melt raw material. For most aluminium foundries that incorporate machining operations in their products, reusing aluminium chips as raw material for the melting stocks is perhaps the best option as waste management policy in what concerns to economical and technical aspects. Nevertheless, aluminium swarf is a low density product (0.25 kg/dm3) and is usually covered by a thin film of aluminium oxide and machining fluid. Melting such a product without suitable previous preparation leads to very low metal recovery rates, high energy consumption, gases and smoke generation and very low quality of the final product. During the last years, the authors have developed a high efficient and environmentally friend aluminium swarf recycling technique, using direct incorporation in aluminium melts. The influence of processing parameters, namely melt temperature and holding time, melting atmosphere, swarf briquetting pressure and melting charge composition in the metal recovery yield and dross generation was studied and characterized...

Does neurotransmission impairment accompany aluminium neurotoxicity?

Goncalves, Paula P.; Silva, Virgilia S.
Fonte: Elsevier Publicador: Elsevier
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
37.18%
Neurobehavioral disorders, except their most overt form, tend to lie beyond the reach of clinicians. Presently, the use of molecular data in the decision-making processes is limited. However, as details of the mechanisms of neurotoxic action of aluminium become clearer, a more complete picture of possible molecular targets of aluminium can be anticipated, which promises better prediction of the neurotoxicological potential of aluminium exposure. In practical terms, a critical analysis of current data on the effects of aluminium on neurotransmission can be of great benefit due to the rapidly expanding knowledge of the neurotoxicological potential of aluminium. This review concludes that impairment of neurotransmission is a strong predictor of outcome in neurobehavioral disorders. Key questions and challenges for future research into aluminium neurotoxicity are also identified. (c) 2007 Elsevier Inc. All rights reserved.; FCT (to V.S.S.); SFRH/BPD/14677/2003

Aluminium-induced impairment of Ca2+ modulatory action on GABA transport in brain cortex nerve terminals

Cordeiro, J. M.; Silva, V. S.; Oliveira, C. R.; Goncalves, P. P.
Fonte: Elsevier Publicador: Elsevier
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
37.23%
The gamma-aminobutyric acid (GABA) is the major inhibitory neurotransmitter in vertebrate CNS. At GABAergic synapses, a high-affinity transporter exists, which is responsible for GABA reuptake and release during nemotransmission. GABA transporter activity depends on the phosphorylation/dephosphorylation state, being modulated by Ca2+/calmodulin-dependent protein phosphatase 2B (calcineurin). Aluminium is known to interfere with the Ca2+ /calmodulin signalling pathway. In this work, we investigate the action of aluminium, on GABA translocation mediated by the high-affinity transporter, using synaptic plasma membrane (SPM) vesicles and synaptosomes isolated from brain cortex. Aluminium completely relieved Ca2+ downregulation of GABA transporter, when mediating uptake or release. Accordingly, aluminium inhibited Ca2+ /calmodulin-dependent calcineurin activity present in SPM, in a concentration-dependent manner. The deleterious action of aluminium on the modulation of GABA transport was ascertained by comparative analysis of the aluminium effect on GABA uptake and release, under conditions favouring SPM dephosphorylation (presence of intracellular micromolar Ca2+) or phosphorylation (absence of Ca2+ and/or presence of W-7, a selective calmodulin antagonist). In conclusion...

Spectrophotometric Determination of Aluminium in Iron Ores Using Solid-Phase Extraction

Ferreira,Sérgio Luis Costa; Lemos,Valfredo Azevedo; Costa,Antônio Celso Spinola; Jesus,Djane Santiago de; Carvalho,Marcelo Souza de
Fonte: Sociedade Brasileira de Química Publicador: Sociedade Brasileira de Química
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/04/1998 EN
Relevância na Pesquisa
37.21%
In the present paper, a procedure for separation and determination of aluminium in iron matrices is proposed. It is based on the solid-phase extraction of the iron, in the form of thiocyanate complexes, by a polyurethane(PU) foam. The followings parameters were studied: effect of pH and of the thiocyanate concentration on the iron extraction, shaking time required for quantitative extraction, amount of PU foam necessary for complete extraction of iron, aluminium separation from other cations, influence of anions on the iron sorption by PU foam and analytical characteristics of the procedure for aluminium determination using methylthymol blue as chromogenic reagent. The results show that, in the pH range from 1.5 to 4.7, with a thiocyanate concentration of 0.80 mol L-1, by extraction using 1 g of polyurethane foam and a shaking time of 1 min, aluminium (40 mug) can be separated from large amounts of iron (10 mg), 800 mug of copper(II), cobalt(II), zinc(II), mercury(II), tin(IV), manganese(II) and tungsten(V); 100 mug of titanium(IV) and lead(II); and 50 mug of vanadium(V). Calcium(II), barium(II), strontium(II) and magnesium(II) can not be separated by this process, but do not react with MTB under the conditions used for aluminium determination. The anions nitrate...

The study of corrosion stability of organic epoxy protective coatings on aluminium and modified aluminium surfaces

Lazarevic,Zorica Z.; Miškovic-Stankovic,Vesna B.; Kacarevic-Popovic,Zorica; Drazic,Dragutin M.
Fonte: Sociedade Brasileira de Química Publicador: Sociedade Brasileira de Química
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/02/2005 EN
Relevância na Pesquisa
37.23%
Epoxy coatings were formed by cathodic electrodeposition of an epoxy resin on aluminium and modified aluminium surfaces (phosphatized, chromatized-phosphatized and anodized aluminium) using a constant voltage method (resin concentration 10 wt.%, temperature 27 ºC, applied voltage 250 V). The corrosion behavior of these coatings was investigated during exposure to 3% NaCl using electrochemical impedance spectroscopy (EIS) and polarization measurements. From the dependence of resistance, capacitance and relative permittivity of the coating, obtained from EIS, on the rate of hydrogen evolution reaction in the electrodeposition bath, obtained from polarization curves, it can be observed that the epoxy coating on aluminium and modified aluminium surfaces is a good barrier against the transport of corrosive agents. The time corresponding to contact between electrolyte and aluminium surface under the coating is greater in the case of surface modification by chromato-phosphatized and anodized aluminium than in the case of phosphatize one.

Determination of the momentum of droplets impinging on the pool during aluminium GMAW

Scotti,Américo; Rodrigues,Carlos Eduardo Aguiar Lima
Fonte: Associação Brasileira de Soldagem Publicador: Associação Brasileira de Soldagem
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/12/2009 EN
Relevância na Pesquisa
37.08%
The purpose of this work was to raise the kinematics and dynamics characteristics of the droplets under transference during aluminium GMA welding and quantify the partial effect of the momentum on the weld bead formation. It is initially claimed that a better way of quantifying this effect would be through the mass flow rate of the droplets reaching the weld pool; calculated parameter denominated here as Effective Momentum. Bead-on-plate GMAW, shielded with Ar, was carried out using an aluminium alloy wire. Three levels of current and two levels of arc length were employed in the experimental design. High-speed filming shadowgraphy, synchronized with the electrical signals, was used as measuring tool. Dedicated computational programs were employed to quantify arc lengths and size, frequency, acceleration and speed of the droplets. It was confirmed that in spite of the low values of the Effective Momentum for aluminium GMAW, the momentum is one of the governing factor in developing bead penetration. The interaction between Effective Momentum and welding current and its effect on the aluminium GMAW bead geometry is discussed.

Impact properties of aluminium - glass fiber reinforced plastics sandwich panels

Periasamy,Mathivanan; Manickam,Balakrishnan; Hariharasubramanian,Krishnan
Fonte: ABM, ABC, ABPol Publicador: ABM, ABC, ABPol
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/06/2012 EN
Relevância na Pesquisa
37.14%
Aluminium - glass fiber reinforced plastics (GFRP) sandwich panels are hybrid laminates consisting of GFRP bonded with thin aluminum sheets on either side. Such sandwich materials are increasingly used in airplane and automobile structures. Laminates with varying aluminium thickness fractions, fiber volume fractions and orientation in the layers of GFRP were fabricated by hand lay up method and evaluated for their impact performance by conducting drop weight tests under low velocity impacts. The impact energy required for initiating a crack in the outer aluminium layer as well as the energy required for perforation was recorded. The impact load-time history was also recorded to understand the failure behavior. The damage depth and the damage area were measured to evaluate the impact resistance. Optical photography and scanning electron micrographs were taken to visualize the crack and the damage zone. The bidirectional cross-ply hybrid laminate (CPHL) has been found to exhibit better impact performance and damage resistance than the unidirectional hybrid laminate (UDHL). Increase in aluminium thickness fraction (Al tf) and fiber volume fraction (Vf) resulted in an increase in the impact energy required for cracking and perforation. On an overall basis...

Surface Passivation of Crystalline Silicon by Sputtered Aluminium Oxide

Tsu Tsung, Andrew Li
Fonte: Universidade Nacional da Austrália Publicador: Universidade Nacional da Austrália
Tipo: Thesis (PhD); Doctor of Philosophy (PhD)
EN_AU
Relevância na Pesquisa
37.23%
Efficient and inexpensive solar cells are necessary for photovoltaics to be widely adopted for mainstream electricity generation. For this to occur, the recombination losses of charge carriers (i.e. electrons or holes) must be minimised using a surface passivation technique suitable for manufacturing. In the literature, it has been shown that the aluminium oxide films are negatively charged dielectrics that provide excellent surface passivation of silicon solar cells. Meanwhile, sputtering has been shown to be an inexpensive thin film deposition method that is suitable for manufacturing. This thesis work aims to combine the excellent passivation properties of aluminium oxide with the manufacturing advantages offered by sputtering. We show - for the first time - that sputtering is capable of depositing negatively charged aluminium oxide films that provide very good surface passivation of crystalline silicon. Effective surface recombination velocities of 24.6 cm/s and 9 cm/s are achieved on 0.8 Ohm.cm p-type crystalline silicon and 1 Ohm.cm n-type crystalline silicon respectively, with charges in the range of -1E11 to -1E13 per square centimetre. We specify the sputtering requirements and processing conditions required for achieving these results...

The development of the welding procedures and fatigue of butt-welded structures of aluminium-AA5383

Calcraft, R. C.; Wahab, Muhammad Abdul; Viano, D. M.; Schumann, G. O.; Phillips, R. H.; Ahmed, N. U.
Fonte: The development of the welding procedures and fatigue of butt-welded structures of aluminium-AA5383 Publicador: The development of the welding procedures and fatigue of butt-welded structures of aluminium-AA5383
Tipo: Artigo de Revista Científica
Publicado em //1999 EN
Relevância na Pesquisa
47.18%
The development of the aluminium shipbuilding industry has seen greater demands put upon the design of faster and larger vessels, particularly in the high speed ferry industry, and increasing loads put on existing vessels. Because of this the fatigue performance of marine grade aluminium alloys has become a limiting factor for design, especially with regard to severe service conditions. Far more information is required, such as the load spectra acting upon the structures and the effects of physical and metallurgical properties, to allow designers to cope with these increased requirements and maximise the performance of the vessels. New grades of marine aluminium alloys have appeared recently, which claimed to improve properties that will aid the designer. CSIRO-MST has begun an in-depth evaluation of the fatigue performance of two marine grade aluminium alloys. Optimisation of welding procedures, post-weld treatments and an understanding of how weld metallurgy relates to the fatigue performance are the major goals. The information produced in this study will allow ship designers and builders to take full advantage of the latest developments in marine grade aluminium alloys. It will also provide the constraints that can be used in the design of larger and faster high speed vessels.; R.C. Calcraft...

Prevention by aluminium phosphate of gastric lesions induced by ethanol in the rat, role of endogenous prostaglandins and sulfhydryls

Duchateau, Alain; Thiefinl, Gérard; Varin-Bischoff, Sophie; Garbe, Edouard; Zeitoun, Paul
Fonte: Murcia : F. Hernández Publicador: Murcia : F. Hernández
Tipo: Artigo de Revista Científica Formato: application/pdf
ENG
Relevância na Pesquisa
37.23%
This study was designed to demonstrate the cytoprotective effect of an antacid containing aluminium phosphate (PhosphalugelB) against ethanol-induced gastric injury in the rat and to determine whether this cytoprotective effect is mediated by endogenous prostaglandins and sulfhydryls. We have quantitatively evaluated gastric mucosal lesions using macroscopic and histological techniques one hour after ethanol administration. Two m1 of aluminium phosphate given orally one hour before administration of 2 m1 of 100% ethanol significantly (p < 0.01) reduced the area of macroscopic lesions induced by ethanol (3.3 i 0.9%) when compared to distilled water (20 i 4.8%). The histological study showed that aluminium phosphate prevented deep tissue necrosis. However, it did not protect surface epithelial cells against ethanol injury. Pretreatment with indomethacin, 5 mglkg sc one hour before aluminium phosphate, slightly but significantly (p < 0.05) reduced the cytoprotective effect of aluminium phosphate. Macroscopic lesions occupied 4.3 i 0.94% and 1.88 i 0.41% of total mucosal area in indomethacin group and in vehicle group, respectively. On the other hand, the sulfhydryl blocker, N-ethylmaleimide, 10 mgíkg sc, given one hour before aluminium phosphate...

Oxidation of Micro-Sized Aluminium Particles: Hollow Alumina Spheres

Velasco López, Francisco Javier; Guzmán Fernández, Susana; Moral Gil, Cristina; Bautista Santa-Cruz, Alfredo
Fonte: Springer Publicador: Springer
Tipo: info:eu-repo/semantics/acceptedVersion; info:eu-repo/semantics/article
Publicado em /10/2013 ENG
Relevância na Pesquisa
37.14%
Oxidized aluminium microparticles have recently been proposed for manufacturing new, environmentally-friendly, protective coatings on stainless-steels and Ni-base alloys. The oxidation mechanisms of spherical aluminium microparticles of an average particle size of 3.5 mu m were studied. Accordingly, simultaneous differential thermal analysis-thermogravimetry tests were carried out in air at different temperatures, always above aluminium melting temperature. Scanning electron microscopy and XRD were also used for the interpretation of results. Weight gain and energy results were explained in terms of the different structural changes taking place in aluminium particles. Dehydroxylation process was identified. The transformation of amorphous alumina to gamma-Al2O3 was numerically evaluated and the alumina phase transformation (gamma-Al2O3 -> I +/--Al2O3) was also studied. The temperature ranges revealed the appearance of metastable phases (theta-Al2O3). Complete oxidation of particles can be obtained at 1,300 A degrees C in < 1 h, although this also takes place at lower temperatures if enough oxidation time is used. Activation energy of oxidation process at high temperature was also estimated, taking a value of 334 kJ/mol. High temperature oxidation causes the formation of hollow alumina spheres...

Climate policy and the aluminium smelting industry

Cong, Andrew
Fonte: Universidade Nacional da Austrália Publicador: Universidade Nacional da Austrália
Tipo: Relatório
Relevância na Pesquisa
37.3%
In economic modelling done by Treasury on the effects of the Government's Carbon Pollution Reduction Scheme (CPRS), the Australian aluminium smelting industry ('the industry') is predicted to contract dramatically in the medium- to long-term. This report examines why the industry is expected to decline in the future. In doing so, this report examines the concepts of international competitiveness loss, carbon leakage, emissions-intensive, trade-exposed industries and climate policy. Australia is the fifth largest producer of primary aluminium in the world. In 2007, Australia produced around 2 million tonnes of aluminium, accounting for around 5 per cent of global production. Almost 85 per cent of the aluminium produced is exported overseas. The industry has an estimated total production value of around $7 billion and export value of around $5 billion. The industry employs around 51000 workers, mostly in regional areas. The two main inputs in aluminium production are alumina and electricity. All the Australian smelters except the Bell Bay smelter in Tasmania (which is powered by hydro-electricity) use coalfired electricity. Coal-fired electricity is the most emissions intensive source of energy. Therefore, the introduction of a carbon cost will create substantially increase the production costs of aluminium in Australia. This increase in cost cannot be passed onto t he consumer as aluminium is an internationally traded commodity and exposed to international market pricing. Hence...

Behaviour of different bare and anodised aluminium alloys in the atmosphere

Bartolomé, Mª. J.; Río, J. F. del; Escudero, E.; Feliu Jr., S.; López, Víctor; Otero, Eduardo; González Fernández, José Antonio
Fonte: Conselho Superior de Investigações Científicas Publicador: Conselho Superior de Investigações Científicas
Tipo: Artículo Formato: 2184133 bytes; application/pdf
ENG
Relevância na Pesquisa
37.14%
Exposure tests in natural atmospheres are an indispensable means for determining the behaviour and durability of metallic materials in the atmosphere. The corrosion behaviour of bare aluminium and anodised aluminium with three different coating thicknesses has been evaluated for two years' exposure in two natural atmospheres of very different corrosivities: one urban and the other marine. Several techniques have been used to evaluate changes in the specimens during exposure, but special attention is paid to the direct measurement of corrosion by gravimetry and its indirect estimation by the comparatively much more sensitive electrochemical impedance spectroscopy (EIS) technique. The results show that if no demands are placed on the conservation of its appearance, aluminium may be used without protection even in atmospheres of medium or high corrosivity. The anodising and sealing of aluminium alloys, above an ill-defined minimum thickness threshold, is an appropriate solution to prevent localised corrosion of aluminium and to conserve its appearance, even in aggressive atmospheres.; Acknowledgements The authors of this work would like to thank to the “Comisión Interministerial de Ciencia y Tecnología (CICYT)” for financial support within the framework of project MAT2003-02217.; Peer reviewed

Estudio de la reactividad entre aleaciones de aluminio y partículas de SiC; Study on the reactivity between aluminium alloys and SiC particles

Criado Herrero, Emilio; Gómez de Salazar, J. M.; Gil, L.; Rodrigo, P.; Martínez, E. E.; Baldonedo, J. L.
Fonte: Sociedad Española de Cerámica y Vidrio Publicador: Sociedad Española de Cerámica y Vidrio
Tipo: Artículo Formato: 2164513 bytes; application/pdf
SPA
Relevância na Pesquisa
37.14%
[ES] Las partículas de refuerzo de SiC reaccionan con el aluminio fundido y forman Al4C3 que es frágil y sensible al contacto con la humedad, lo que degrada las propiedades de los materiales compuestos constituidos por ambos componentes. La reacción en la intercara Al/SiC depende de varios parámetros de fabricación como temperatura, tiempo de residencia, atmósfera y composición química, tanto de la matriz de aluminio como del refuerzo de SiC. Se han realizado estudios sistemáticos de reactividad entre partículas de SiC y aluminio fundido, analizando el efecto que tiene la formación de una capa de SiO2 por oxidación de las partículas cerámicas, antes de su incorporación en el fundido, como barrera protectora para prevenir el ataque del SiC por la matriz. Se ha estudiado también el efecto de la composición de la matriz metálica en dicha reactividad, empleando para ello varias aleaciones de aluminio: AA1170 (99,7%Al), A-319.0 (Al-6Si-3Cu) y A-332.0 (Al-11Si-1,5Cu). Los materiales compuestos se prepararon mediante mezcla de partículas de SiC (30 % vol.) y polvo de las aleaciones de aluminio, prensado en frío y posterior fusión a 900ºC, variando el tiempo de residencia dentro del horno para simular un proceso de fabricación por colada. Los resultados obtenidos se comparan con los obtenidos para materiales compuestos del tipo AA 2014/SiC/20p.; [EN] The SiC reinforcement particles react with the molten aluminium to form Al4C3 that is brittle and sensitive to the the humidity. This reaction degrades the properties of the SiC reinforced aluminium matrix composites. The extend of the reaction in the Al/SiC interface depends on the fabrication parameters such as the temperature...

Reuse of steel and aluminium without melting

Cooper, Daniel
Fonte: University of Cambridge; Department of Engineering Publicador: University of Cambridge; Department of Engineering
Tipo: Thesis; doctoral; PhD
EN
Relevância na Pesquisa
37.23%
Carbon dioxide emissions must be dramatically reduced to avoid the potentially dangerous effects of climate change. The steel and aluminium industries produce large amounts of carbon dioxide, accounting for 6% of anthropogenic emissions. Previous studies have shown that in these industries there is limited scope for further improvements in energy efficiency. Material efficiency strategies can, however, further reduce emissions. This thesis focuses on materially efficient reuse without melting. A scoping study of current reuse found three opportunities, an examination of which forms the basis of this thesis: reusing components at end of product life; extending the lifespan of products; and reusing manufacturing scrap. The opportunity to reuse components has received little attention to date and there is no clearly defined set of strategies or barriers to enable assessment of appropriate component reuse; neither is it possible to predict future levels of reuse. This thesis presents a global assessment of the potential for reusing steel and aluminium components. A combination of top-down and bottom-up analyses is used to allocate the final destinations of current global steel and aluminium production to final products. A substantial catalogue has been compiled for these products characterizing key features of steel and aluminium components including design specifications...

Corrosion Prevention of Aluminium in 1 M HCl by Surface Deposition of Nickel Titanate

Beenakumari,K.S.
Fonte: Sociedade Portuguesa de Electroquímica Publicador: Sociedade Portuguesa de Electroquímica
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/08/2013 EN
Relevância na Pesquisa
37.23%
A different approach for protecting the aluminium in 1M HCl is done by strengthening the surface oxide film of aluminium with nickel titanate particles. Weight loss methods, open circuit potential measurements and polarization techniques are used to measure the corrosion behaviour of aluminium samples. The corrosion rate of nickel titanate deposited aluminium shows lower values compared to pure aluminium in HCl medium. The intermixing of aluminium oxide with nickel titanate enhances the corrosion resistance property of the aluminium oxide layer on the surface of aluminium and thereby reduces the coulombic and non-coulombic loss of metal.