Página 1 dos resultados de 124 itens digitais encontrados em 0.004 segundos

"Utilização da escória de alumínio na fabricação de argila expandida" ; APPLICATION OF ALUMINUM SLAG INCORPORATED IN LIGTHWEIGHT AGGREGATE

Takahashi, Elisa Akiko Nakano
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 14/09/2006 PT
Relevância na Pesquisa
37.686309%
O presente trabalho estuda a viabilidade de utilização da escória de alumínio, que é um rejeito da indústria recicladora de alumínio, atualmente sem valor agregado, como elemento integrante na fabricação de argila expandida. A argila expandida é produzida a partir de argilas que produzam expansão piroplástica, que são utilizadas como agregado leve na fabricação de concreto estrutural e também como artigo decorativo em jardins. Inicialmente foram feitas análises dos materiais de partida, como difração de raios X, microscopia eletrônica de varredura, fluorescência de raios X, análise granulométrica, análise termogravimétrica e análise térmica diferencial da argila. Foram feitas incorporações do rejeito junto à massa de argila, na proporção de 5%, 10%, 15% e 20% em massa. As formulações estudadas foram analisadas quanto à expansão linear, variação de massa, massa específica aparente e absorção de água. Foram feitos também ensaios de lixiviação e solubilização. Os principais resultados obtidos mostraram que é viável o uso da escória de alumínio até aproximadamente 5% em massa, para a produção da argila expandida, com características aceitáveis e dentro das normas vigentes. Palavraschave: reciclagem...

Simulação numérica do comportamento ao impacto de componentes em alumínio

Felgueiras, Rolando Alves
Fonte: Universidade do Minho Publicador: Universidade do Minho
Tipo: Trabalho de Conclusão de Curso
Publicado em //2012 POR
Relevância na Pesquisa
27.180537%
Dissertação de mestrado integrado em Engenharia Mecânica; Este trabalho pretende servir como estudo de indentação dinâmica de placas de alumínio. Existem dois tipos de denting o dinâmico e estático sendo este trabalho só sobre o dinâmico. Podemos definir o fenómeno de impacto como sendo uma solicitação ou carregamento repentino, o que neste caso vai corresponder a por exemplo uma pedra a bater no capot do carro. A resistência ao denting é uma propriedade muito importante dos painéis é um parâmetro chave no desenho para painéis como exemplo o capô de um veículo. O impacto é um fenómeno tipicamente dinâmico. Ele ocorre quando um objecto atinge outro, ou seja, colide com outro, desenvolvendo grandes forças entre eles num período muito curto de tempo, é de grande importância estudar a absorção de energia por parte dos materiais ao impacto. O principal objectivo do estudo é a realização de uma comparação entre ensaios experimentais dinâmicos e simulações numéricas de chapas de alumínio. O programa de ensaios numéricos utiliza um código explícito (LS-DYNA), servindo estes ensaios para comparar resultados numéricos com os dinâmicos a nível de deslocamentos, acelerações e dent ratio. O programa informático LS-DYNA é relativamente fácil de manusear tendo em conta o evoluir da utilização...

Influência do teor de silício na usinabilidade da liga de alumínio 6351 - avaliada através de força de corte e acabamento superficial; Influence of the silicon content in the machinability of the 6351 aluminium alloy – analysed through cutting force and surface finish

Cunha, Daniel Fernandes da
Fonte: Universidade Federal de Uberlândia Publicador: Universidade Federal de Uberlândia
Tipo: Dissertação
POR
Relevância na Pesquisa
27.180537%
O objetivo deste trabalho é a verificação da influência do teor de silício na composição da liga de alumínio 6351 da empresa CBA (Compania Brasileira de Alumínio) na usinabilidade avaliada através da medição da força de corte e do acabamento superficial. Em uma primeira etapa foi analisado estatisticamente o efeito dos parâmetros de corte, profundidade de corte (ap), velocidade de corte (vc), avanço (f) e porcentagem de silício (% Si) na força de corte e rugosidade superficial durante ensaios de torneamento cilíndrico externo sem aplicação do fluido de corte. Em uma segunda etapa dos ensaios utilizou-se fluido de corte aplicado através de MQF (60l/h) e jorro, mantendo constante a profundidade de corte e variando velocidade de corte e avanço. Para cada uma das combinações de parâmetros de corte foram adquiridos valores de força de corte e rugosidade superficial com duas réplicas para cada ensaio, adotando um planejamento fatorial 3k. Analise estatística de variância (ANOVA) mostrou que a porcentagem de silício exerce influência significativa nos parâmetros de usinabilidade avaliados da liga estudada quando comparado com avanço, velocidade de corte e profundidade de corte. ______________________________________________________________________________ ABSTRACT; The aim of this work is to study the effect of silicon content in the machinability of CBA’s (Compania Brasileira de Aluminio) 6351 aluminum alloy measured through cutting force and surface finish. In a first moment the effect of depth of cut (ap)...

A comparison of the aging kinetics of a cast alumina-6061 aluminum composite and a monolithic 6061 aluminum alloy.

Hafley, Johanna L.
Fonte: Monterey, California. Naval Postgraduate School Publicador: Monterey, California. Naval Postgraduate School
Tipo: Tese de Doutorado
EN_US
Relevância na Pesquisa
37.64135%
Electrical resistivity and hardness measurements were conducted during isothermal aging treatments of an alumina particulate reinforced 6061 aluminum metal matrix composite and a monolithic 6061 aluminum control material. Transmission electron microscopy was utilized to examine the microstructural changes accompanying the changes in the resistivity of the monolithic during aging. In addition, differential scanning calorimetry was used to investigate the growth kinetics and thermal stability of the metastable phases in the control sample. From DSC experiments, the heats of formation of the metastable phases were determined as functions of aging time and temperature. These results were used to characterize the aging behavior of the matrix material. Keywords: Aluminum composite, Conductivity, Aluminum alloys. (jes)

Young chondrules in CB chondrites from a giant impact in the early Solar System

Krot, Alexander; Amelin, Yuri; Cassen, Patrick; Meibom, Anders
Fonte: Macmillan Publishers Ltd Publicador: Macmillan Publishers Ltd
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
27.180537%
Chondrules, which are the major constituent of chondritic meteorites, are believed to have formed during brief, localized, repetitive melting of dust (probably caused by shock waves) in the protoplanetary disk around the early Sun. The ages of primitive c

Finite element modelling of core thickness effects in aluminium foam/composite sandwich structures under flexural loading

Styles, Millicent; Compston, Paul; Kalyanasundaram, Shankar
Fonte: Elsevier Publicador: Elsevier
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
27.180537%
This paper models the flexural behaviour of a composite sandwich structure with an aluminium foam core using the finite element (FE) code LS-DYNA. Two core thicknesses, 5 and 20 mm, were investigated. The FE results were compared with results from previou

Lead Isotopic Ages of Chondrules and Calcium-Aluminum-Rich Inclusions

Amelin, Yuri; Krot, Alexander; Hutcheon, Ian D; Ulyanov, Alexander A.
Fonte: American Association for the Advancement of Science Publicador: American Association for the Advancement of Science
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
47.49956%
The lead-lead isochron age of chondrules in the CR chondrite Acfer 059 is 4564.7 ± 0.6 million years ago (Ma), whereas the lead isotopic age of calcium-aluminum-rich inclusions (CAIs) in the CV chondrite Efremovka is 4567.2 ± 0.6 Ma. This gives an inter

Low energy impact damage modes in aluminum foam and polymer foam sandwich structures

Compston, Paul; Styles, Millicent; Kalyanasundaram, Shankar
Fonte: Sage Science Press Publicador: Sage Science Press
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
47.378027%
The energy absorption of an aluminum foam sandwich structure and a conventional polymer foam sandwich structure is similar for impacts ranging from 5 to 25 J. The polymer foam-based samples exhibit localized damage in the form of skin fracture and core cr

Nucleation and growth of zeolite A under reagent controlled conditions. Part II

Singh, Puyam S; White, John
Fonte: Royal Society of Chemistry Publicador: Royal Society of Chemistry
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
27.180537%
Broad differences in the synthesis kinetics and the morphology of zeolite A from two silicate sources (soluble silicate and Ludox colloidal silica) and two different aluminium sources (aluminium isopropoxide and freshly prepared aluminium hydroxide) are reported. The differences are attributed to different rate limiting steps in the syntheses. The reactions have been followed by small angle X-ray scattering from the time of first mixing of the constituents until the final separation of zeolite A crystals. The soluble silicate and Ludox/aluminium hydroxide syntheses produce excellent cubic crystals in the 300 nm-1 μm size range. The products of the first synthesis have an interesting texture on the scale of nanometres but with aluminium isopropoxide as the aluminium source, the resulting zeolite A has a spherical morphology of size ca. 100 nm. Possible reasons for the development of these morphologies are discussed.

Oligomeric but not monomeric silica prevents aluminium absorption in humans

Jugdaohsingh, Ravin; Reeves, Raymond; Oldham, Claire; Day, J P; Fifield, L Keith; Thompson, Richard; Powell, Jonathan
Fonte: American Society of Clinical Nutrition Publicador: American Society of Clinical Nutrition
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
37.855684%
Background: Soluble silica, a ubiquitous component of the diet, may be the natural ligand for dietary aluminum and may prevent its accumulation and toxicity in animals. However, previous studies on the inhibition of aluminum absorption and toxicity by soluble silica have produced conflicting results. We recently identified a soluble silica polymer, oligomeric silica, that has a much higher affinity for aluminum than does monomeric silica and that may be involved in the sequestration of aluminum. Objective: By using26Al as a tracer, we investigated the effects of oligomeric and monomeric silica on the bioavailability of aluminum (study 1) and compared the availability of silicon from oligomeric and monomeric silica in the human gastrointestinal tract (study 2). Design: In study 1, three healthy volunteers each ingested aluminum alone (control), aluminum with oligomeric silica (17 mg), and aluminum with monomeric silica (17 mg). In study 2, five healthy volunteers ingested both the oligomeric and monomeric forms of silica (34 mg). Serum and urine samples were analyzed for aluminum and silicon. Results: Oligomeric silica reduced the availability of aluminum by 67% (P = 0.01) compared with the control, whereas monomeric silica had no effect (P = 0.40). Monomeric silica was readily taken up from the gastrointestinal tract and then excreted in urine (53%)...

Reflections on Aluminum: Some Thoughts on the Mesospheric Processing of Ablated Meteoric Al +

Petrie, Simon
Fonte: CSIRO Publishing Publicador: CSIRO Publishing
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
37.180537%
Quantum-chemical calculations, at the CP-dG2thaw level of theory, are used to characterize several novel Al-containing molecular and cluster ions that are likely to participate in the chemistry of Al+ resulting from meteoric ablation in the upper atmosphere. The calculations suggest that two overall processes may be dominant in aluminium's ion chemistry in the mesosphere/lower thermosphere (MLT) region. The first of these processes is an efficient cycle (Al+ → AlN2+ → A1O+ → Al+), with addition of N2 to Al+ the apparent rate-determining step on the overall cycle, and with weak competition from neutralization processes. The second possible process involves conversion of Al+ to the species HOAlOH+, by (we propose) reaction with H2O and O (3P) respectively. Although water vapour is only a trace species within the mesosphere, production of HOAlOH+ appears pivotal: This molecular ion is intrinsically stable against substitution or abstraction involving other mesospheric species, but is highly activated towards further addition of N2, CO2 and H2O. We propose that, once formed, HOAlOH+ is rapidly consumed through condensation reactions, producing larger cluster ions whose eventual neutralization through dissociative recombination will most probably yield hydrated AlOn structures. These Al-containing neutrals may act as nucleation sites for noctilucent and polar stratospheric clouds.

Oxygen-isotope fractionation between aluminium hydroxides phases and water at <60�C: results of decade-long synthesis experiments

Vitali, Frederic; Longstaffe, Fred; Bird, Michael; Caldwell, W
Fonte: Clay Minerals Society Publicador: Clay Minerals Society
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
37.49956%
Oxygen-isotope data were obtained for synthetic aluminum-hydroxide phases precipitated over 65-125 mo and have been compared to results from similar experiments conducted for 3-56 mo. The Al(OH)3 polymorphs, gibbsite, nordstrandite, and bayerite, were synthesized, but gibbsite was dominant in most samples, and commonly the only phase present. Using pure gibbsite samples, the following oxygen-isotope fractionation factors, α(gibbsite-H(2)O), were obtained: 1.0167 ± 0.0003 (9 ± 1°C), 1.0147 ± 0.0007 (24 ± 2°C), 1.0120 ± 0.0003 (51 ± 2°C). These values, and the associated equation for an oxygen-isotope geothermometer for the interval 0-60°C, 1031n α(gibbsite-H(2)O) = 2.04 X 106/T2 - 3.61 X 103/T + 3.65 (T in K), are not significantly different from those obtained from experiments of much shorter duration. These results, and the good agreement with α(gibbsite-H(2)O) values obtained for well-constrained natural systems, suggest that the experimentally determined fractionation factors describe equilibrium conditions for gibbsite that has precipitated directly from solution. As also proposed by others using a modified-increment calculation, our synthesis experiments suggest that α(Al((OH))(3)-H(2)O) is polymorph-dependent at low temperatures and that a significant temperature-dependent trend exists in the values of α(Al((OH))(3)-H(2)O). However...

Comparison of surface strain for stamp formed aluminum and an aluminum-polypropylene laminate

Compston, Paul; Cantwell, Wesley J; Cardew-Hall, Michael; Kalyanasundaram, Shankar; Mosse, Luke
Fonte: Kluwer Academic Publishers Publicador: Kluwer Academic Publishers
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
47.721494%
The permanent strain on the surface of a channel-formed aluminum-polypropylene laminate was compared to monolithic aluminum. The materials used in this study were 5005-H34 aluminum and a self-reinforced polypropylene (Curv, BP). Microscopic examination of the sidewall edge, prior to taking the strain measurements, confirmed the absence of delamination. The results show that the aluminum-Curv laminate exhibits low strain and is not influenced by a change in tool radii, which makes it efficient to solve the problems associated with stamping of traditional monolithic metals.

AFM Observations of Latent Fission Tracks on Surfaces: Amorphous SiO 2 and Quartz

Espinosa, G.; Golzarri, J I; Vazquez, C; Fragoso, R.; Chadderton, Lewis; Cruz, S.A.
Fonte: Pergamon-Elsevier Ltd Publicador: Pergamon-Elsevier Ltd
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
37.180537%
Preliminary results of a systematic AFM experimental investigation of the surface 'track' effects produced by the passage of fission fragments from a californium (252Cf) source into amorphous SiO2 and quartz are described. Fission fragments from the source were collimated using a 10 μm thick aluminum foil and comprised fragments with the usual binary distribution of energies - light and heavy - 79.4 and 103.8 MeV. Irradiations and AFM measurements were carried out in air at normal room temperature and pressure. Remarkably high sputtering yields/fragment were discovered, and in the case of crystalline quartz the ejecta was found to be arranged in an ordered manner. A brief discussion is given of a part likely to be played by electronic energy loss induced Coulomb explosion of target atoms for each point of fragment entry.

Molecular characterization and mapping of ALMT1, the aluminium-tolerance gene of bread wheat (Triticum aestivum L.)

Raman, Harsh; Zhang, Kerong; Cakir, Mehmet; Appels, Rudi; Garvin, David F; Maron, Lyza G; Kochian, Leon V; Moroni, J Sergio; Raman, Rosy; Imtiaz, Muhammad; Drake-Brockman, Fiona; Waters, Irene; Martin, Peter; Sasaki, Takayuki; Yamamoto, Yoko; Matsumoto, H
Fonte: National Research Council of Canada Publicador: National Research Council of Canada
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
37.378027%
The major aluminum (Al) tolerance gene in wheat ALMT1 confers an Al-activated efflux of malate from root apices. We determined the genomic structure of the ALMT1 gene and found it consists of 6 exons interrupted by 5 introns. Sequencing a range of wheat genotypes identified 3 alleles for ALMT1, 1 of which was identical to the ALMT1 gene from an Aegilops tauschii accession. The ALMT1 gene was mapped to chromosome 4DL using 'Chinese Spring' deletion lines, and loss of ALMT1 coincided with the loss of both Al tolerance and Al-activated malate efflux. Aluminium tolerance in each of 5 different doubled-haploid populations was found to be conditioned by a single major gene. When ALMT1 was polymorphic between the parental lines, QTL and linkage analyses indicated that ALMT1 mapped to chromosome 4DL and cosegregated with Al tolerance. In 2 populations examined, Al tolerance also segregated with a greater capacity for Al-activated malate efflux. Aluminium tolerance was not associated with a particular coding allele for ALMT1, but was significantly correlated with the relative level of ALMT1 expression. These findings suggest that the Al tolerance in a diverse range of wheat genotypes is primarily conditioned by ALMT1.

Mechanochemical Formation of Metal-Ceramic Composites

Welham, N; Willis, P; Kerr, T
Fonte: American Chemical Society Publicador: American Chemical Society
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
27.49956%
A mechanical activation technique has been used to form composites of alumina with titanium carbide, nitride, or carbonitride, both with and without elemental iron. The composites were formed by reacting elemental aluminum with either ilmenite (FeTiO3) or rutile (TiO2) concentrates in the presence of carbon and/or nitrogen in a ball-mill at ambient temperature. The reaction was complete for the ilmenite samples after milling but was completed only for rutile under hot pressing conditions. Microhardness measurements indicated that the composites had hardnesses in the range 19-30 GPa (1740-2750 VHN), with only a small variation within each sample. Elemental mapping of the pressed pellets indicated that titanium and aluminum were evenly distributed on a submicrometer level whereas iron tended to coalesce into <20 μm particles in the presence of TiC. The coalescence decreased with the carbon content of the hard material until iron was evenly distributed with TiN. A superstoichiometric amount of aluminum led to the formation of iron-aluminum phases which decreased the iron coalescence. The XRD crystallite size of the alumina was 30-50 nm and was 25-50 nm for the titanium phases, confirming the extremely fine microstructure.

Analysis of TaALMT1 traces the transmission of aluminum resistance in cultivated common wheat (Triticum aestivum L.)

Raman, Harsh; Ryan, P.R.; Raman, R.; Stodart, B.J.; Zhang, Kerong; Martin, P.; Wood, R.; Sasaki, T.; Yamamoto, Yoko; Mackay, M.; Hebb, Diane M; Delhazie , E.
Fonte: Springer Publicador: Springer
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
37.378027%
Allele diversities of four markers specific to intron three, exon four and promoter regions of the aluminum (Al) resistance gene of wheat (Triticum aestivum L.) TaALMT1 were compared in 179 common wheat cultivars used in international wheat breeding programs. In wheat cultivars released during the last 93 years, six different promoter types were identified on the basis of allele size. A previous study showed that Al resistance was not associated with a particular coding allele for TaALMT1 but was correlated with blocks of repeated sequence upstream of the coding sequence. We verified the linkage between these promoter alleles and Al resistance in three doubled haploid and one intercross populations segregating for Al resistance. Molecular and pedigree analysis suggest that Al resistance in modern wheat germplasm is derived from several independent sources. Analysis of a population of 278 landraces and subspecies of wheat showed that most of the promoter alleles associated with Al resistance pre-existed in Europe, the Middle East and Asia prior to dispersal of cultivated germplasm around the world. Furthermore, several new promoter alleles were identified among the landraces surveyed. The TaALMT1 promoter alleles found within the spelt wheats were consistent with the hypothesis that these spelts arose on several independent occasions from hybridisations between non-free-threshing tetraploid wheats and Al-resistant hexaploid bread wheats. The strong correlation between Al resistance and Al-stimulated malate efflux from the root apices of 49 diverse wheat genotypes examined was consistent with the previous finding that Al resistance in wheat is conditioned primarily by malate efflux. These results demonstrate that the markers based on intron...

Hydrogen-isotope fractionation in aluminium hydroxides: synthesis products versus natural samples from bauxites

Vitali, Frederic; Longstaffe, Fred; Bird, Michael; Gage, Karie Lyne; Caldwell, W
Fonte: Pergamon-Elsevier Ltd Publicador: Pergamon-Elsevier Ltd
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
37.180537%
Hydrogen-isotope data have been gathered for synthetic aluminum hydroxides precipitated over 3 to 121 months at temperatures varying between 8 and 51°C. All three Al(OH)3 polymorphs, gibbsite, nordstrandite, and bayerite, were generated during the synthe

Momentum profiles of aluminum

Vos, Maarten; Kheifets, Anatoli; Weigold, Erich
Fonte: Elsevier Publicador: Elsevier
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
47.378027%
Electron momentum spectroscopy is a tool ideally suited for the study of the energy-resolved momentum densities. Here we present new data from a high-energy EMS experiment using 50 keV incoming and 25 keV outgoing electrons. Momentum profiles have been measured from a thin aluminum film for the 2p core level and the valence band near Ef. The resolution of these momentum profiles, as well as the effects of multiple scattering are discussed. It is found that the high-energy EMS experiment measures momentum densities with superior resolution and very little background.

Quantitative Measurement of the Spectral Function of Aluminum and Lithium by Electron Momentum Spectroscopy

Vos, Maarten; Kheifets, Anatoli; Sashin, Vladimir; Weigold, Erich; Usuda, M; Aryasetiawan, Ferdi
Fonte: American Physical Society Publicador: American Physical Society
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
47.49956%
We present measurements of the spectral function of aluminum and lithium using high-energy electron momentum spectroscopy. For aluminum the quasiparticle peaks show clear asymmetries and significant satellite intensity that extends over a wide region to larger binding energies. The intensity distribution is not well described by band structure calculations. These data are described only by calculations based on the manybody cumulant expansion scheme. The measured momentum distribution at the Fermi level agrees with the theoretical one within 0.03 a.u. For lithium a bandwidth of 3.0 eV is obtained.