Search results for "Aluminium"
showing 10 items of 548 documents
The influence of the nature of the surface oxide on the adhesive fracture energy of aluminium-bonded joints as measured by T-peel tests
2008
Abstract Modification of aluminium alloy substrates microstructure and morphology by depositing new oxide layers on top of the metal surface has been investigated, with the aim of improving adhesion. The effect of treating the metal with boiling water or immersing it in a cerate bath has been studied by means of electron microscopy, contact angle measurements and peeling tests. The formation of pseudoboehmite layers or cerium conversion coatings both led to an increase in joint's adhesive fracture energy and more durable adhesive bonds with respect to joints obtained with “mechanically grinded only” substrates. Differences in the performance of the bonded joints has been discussed in terms …
Influence of initial treatments of aluminium on the morphological features of electrochemically formed alumina membranes
2003
Abstract The fabrication of alumina membranes by electrochemical oxidation of annealed aluminium was investigated. Porous layers were grown in 0.4 M H3PO4 at −1 and 5 °C at different anodising times. The morphology of the outer surface was found to be dependent on temperature and charge density, with both determining the extent of chemical dissolution of the anodic oxide. The inner-surface morphology was found to depend on the applied voltage only. The chemical dissolution rate of anodic oxide grown on annealed aluminium was found to be lower than that formed on unannealed aluminium under otherwise identical conditions. Such a difference in behaviour is explained in terms of a higher finish…
On the Finite Element Simulation of Secondary Operations on Metallic Foams
2007
Metallic foams have been recently introduced also as industrial materials due to their well known advantages. In fact, their low mass in conjunction with the good thermal and mechanical properties push toward an extensive diffusion in manufacturing industry. In the study here addressed, a very accurate investigation concerning the latter two aspects has been carried out. In fact, a secondary manufacturing process, i.e. the foam bending, has been taken into account. Anyway, all the knowledge derived for sheet metal bending is not directly applicable to the foams. A finite element code has been utilized for modeling the foam behavior during the bending processes and an accurate material rheol…
Haemostatic agents on the shear bond strength of self-adhesive resin
2015
Background Dentin surface contaminated with haemostatic agents can interfere with the bonding of self-adhesive resin cement. Therefore the purpose of this study was to evaluate the effect of various haemostatic agents such as Aluminium chloride, Ferric sulphate and Tannic acid on the shear bond strength of self-adhesive resin luting agent. Material and Methods The buccal surfaces of extracted premolars were flattened to expose the dentine. The teeth were then randomly divided into four groups. In Group I Aluminium Chloride was applied on the flattened dentinal surface, in Group II Ferric Sulphate was applied to exposed dentin surface, in Group III tannic acid was applied on to the dentinal …
Mechanism of anionic polymerization of (meth)acrylates in the presence of aluminium alkyls, 1. 13C NMR studies of model compounds in toluene
1994
The bimetallic ate complex [(CH 3 ) 2 C=C(OEt)(O - AlR 3 )]Li + is regarded to be the model of the active centre of the polymerization of methyl methacrylate in the presence of aluminium alkyls. This complex is detectable by 13 C NMR up to 273 K. At ambient temperature irreversible decomposition takes place. Apart from the formation of the ate complex, excess aluminium chloride coordinates to the ester carbonyl groups of both the monomer and the polymer chain
On the mechanism of the interaction between oxygen and close-packed single-crystal aluminum surfaces
2003
Abstract Using periodic first principles simulations we investigate the interaction of oxygen molecules with both regular Al(111) and Al(001) surfaces as well as a stepped Al(111) substrate. The limitation of this approach is the use of thin metallic slabs with a limited range for their coverage by adsorbed oxygen. The advantage is the detailed modeling that is possible at an atomic level. On the regular Al(111) surface, we have been able to follow the oxidation process from the approach of O 2 molecules to the surface, through the chemisorption and absorption of O atoms, up to the formation of first Al 2 O 3 formula units. An energetically feasible mechanism for the formation of these Al 2…
Thermostimulated processes in statically and dynamically disordered luminescent solids
1993
Abstract Trap spectra depending on the concentration of defects in crystalline KBr-T1, LiF-Mg, Ti, A1 2 O 3 and glassy Na 2 O·SiO 2 are investigated. The nature of inhomogeneous broadening and continuous distribution of traps over activation energies at sufficiently high defect concentrations is considered. Impurity hopping controlled recombination of electronic excitations is observed. The presence of enlarged values of process activation energies and frequency factors is discussed in terms of the concept of dynamic disorder, taking into account the fluctuational changes in both the perfectpart and the structure of defects in the solid at high temperatures.
Defects in yttrium aluminium perovskite and garnet crystals: atomistic study
2000
Native and impurity point defects in both yttrium aluminium perovskite (YAP) and garnet (YAG) crystals are studied in the framework of the pair-potential approximation coupled with the shell model description of the lattice ions. The calculated formation energies for native defects suggest that the antisite disorder is preferred over the Frenkel and Schottky-like disorder in both YAP and YAG. The calculated values of the distortion caused by the antisite YAl x in the lattice turn out to be in an excellent agreement with the EXAFS measurements. In non-stoichiometric compounds, the calculated reaction energies indicate that excess Y2 O3 or Al2 O3 is most likely to be accommodated by the forma…
Pyroxene-based glass-ceramics as glazes for floor tiles
2005
Abstract Crystallization of a glass with composition in the diopside primary crystallization field in the MgO–CaO–Al 2 O 3 –SiO 2 quaternary system was investigated. Also the action of some additives, nucleants and fluxes, in the pyroxene development was examined. Glasses were prepared by conventional melting of a mixture of raw materials and cooled by pouring in water. Pellets of glass powder specimens were thermally treated at several temperatures up to 1200 °C. The crystallization path was followed by X-ray diffraction powder (XRD), scanning electron microscopy (SEM) and energy dispersive X-ray spectrometry (EDX). The results proved that, in addition to the effect of B 2 O 3 and TiO 2 in…
A rietveld study of the cation substitution between uvarovite and yttrium-aluminum synthetic garnets, obtained by sol-gel method
1994
A series of synthetic garnets solid solutions with compositions between Y 3 Al 2 Al 3 O 12 (Y-Al garnet) (YAG) and Ca 3 Cr 2 Si 3 O 12 (uvarovite) was synthesized using the sol-gel method. The expected general formula is (Ca x Y 1-x ) 3 (Cr x Al 1-x ) 2 (Si x Al 1-x ) 3 O 12 where x=0 to x=1. The cation distribution in dodecahedral, octahedral and tetrahedral sites and bond distances in these synthetic garnets were determined using the Rietveld method. It shows the incomplete substitution in small sites. The smaller site the smaller substitution there is