Showing papers on "Aluminium published in 1987"
TL;DR: In this article, the variations with time of the contact angle formed by molten pure aluminium or Al-Si alloys with single crystalline SiC were measured by the sessile drop method in a vacuum of 10−4 to 10−5 Pa at temperatures ranging from 933 to 1200 K.
Abstract: The variations with time of the contact angle formed by molten pure aluminium or Al-Si alloys with single crystalline SiC were measured by the sessile drop method in a vacuum of 10−4 to 10−5 Pa at temperatures ranging from 933 to 1200 K. In the Al/SiC system, a “non-wetting-wetting” transition was observed at a temperature that decreases as time increases. After holding times of about 2 h, contact angles were stabilized to acute angles even at the aluminium melting point. Although additions of silicon to aluminium were in such amounts as to prevent Al4C3 formation at the interface, wettability in both pure Al/SiC and Al-Si alloys/SiC systems was not observed to differ appreciably.
232 citations
TL;DR: In this paper, a new type of aluminium in hydrothennally treated Y and ZSM-5 zeolites has been detected by high-field 27 Al NMR, using very fast sample spinning and two-dimensional NMR spectroscopie techniques.
213 citations
TL;DR: In this article, the authors report the observation of enhanced backscattering and strongly depolarized scattering of light from random rough surfaces, whose height fluctuations obey gaussian statistics, fabricated in photoresist with an aluminium overcoating.
200 citations
TL;DR: In this article, the locations of barrier-and porous-type films were determined precisely by direct observation of film sections, incorporating inert marker layers and tracers, in the transmission electron microscope and appropriate analysis.
Abstract: Key aspects of anodic film growth on aluminium at ambient temperatures in aqueous electrolytes, encompassing barrier- and porous-type films, are described. By direct observation of film sections, incorporating inert marker layers and tracers, in the transmission electron microscope and appropriate analysis, the locations of solid-film growth and electrolyte anion effects can be determined precisely. Thus, during barrier-film formation, at high current efficiency, Al3+ ion egress and O2-/OH− ingress proceed across the pre-existing air-formed film to develop solid material at the film/electrolyte and metal/film interfaces respectively. With decrease in current efficiency, the former contribution declines through a mechanism of direct ejection of Al3+ ions at the film/electrolyte interface. At a critical current density, all outwardly mobile Al3+ ions are lost to the electrolyte. Concerning anions of the forming electrolyte, such species (or more strictly their transformation products) may be mobile...
175 citations
TL;DR: The results of these experiments indicate that ∼ 8-10% of the aluminum in atmospheric aerosols of crustal origin over the North Pacific is soluble in seawater as mentioned in this paper, indicating that dissolution of aerosol aluminum is an important source of dissolved aluminum to these waters.
171 citations
TL;DR: In this article, a more substantial range of data for alloys of this type is presented and it is concluded that ductility in creep is the most significant parameter correlating differences in rates of strain-accumulation in the tertiary stage: thus, the lower the ductility the greater the rate of strain accumulation.
151 citations
TL;DR: In this article, a simple theory of magnetic braking in a thin metal strip is proposed and the predictions of the model are compared to experiment and good agreement is obtained. But the experimental tests were conducted by spinning a thin aluminum disk of large radius between the pole pieces of an electromagnet.
Abstract: A simple theory of magnetic braking in a thin metal strip is proposed. The predictions of the model are compared to experiment and good agreement is obtained. The experimental tests were conducted by spinning a thin aluminum disk of large radius between the pole pieces of an electromagnet. A field range of 0 to 150 mT was used.
149 citations
TL;DR: In this article, the chemistry and structure of weld metal inclusions was studied using a Philips 400T scanning transmission electron microscope, fitted with an energy dispersive analyser. And the inclusions were found to be glassy and essentially manganese silicate in composition with areas of a polycrystalline, titanium-rich phase on the surface.
Abstract: The chemistry and structure of weld metal inclusions has been studied. Four submerged arc welds which utilized plate and consumables to cover a range of oxygen and deoxidant contents were examined. Analysis of the inclusions was carried out on carbon extraction replicas in a Philips 400T scanning transmission electron microscope, fitted with an energy dispersive analyser. Two major types of inclusion were found. With weld metal aluminium approaching the stoichiometric ratio with oxygen, the inclusions were crystalline and had a spinel structure at the centre with a discontinuous, polycrystalline, titanium-rich phase on the surface. With weld metal oxygen high compared with the stoichiometric ratio with aluminium, inclusions were glassy and essentially manganese silicate in composition, again with areas of a polycrystalline, titanium-rich phase on the surface. The interinclusion spacing varied little with weld metal oxygen content in the range 0·0268–0·0858 wt-%. The spacing was found to be of a si...
144 citations
TL;DR: In this article, the grain boundary segregation of magnesium is examined with reference to both direct and indirect experimental evidence for magnesium segregation, and evidence to support both equilibrium and non-equilibrium segregation is presented.
133 citations
TL;DR: In this paper, the reductive dissolution of Na-dithionite of 28 synthetic goethites and 26 hematites having widely different crystal morphologies, specific surfaces and aluminium substitution levels has been investigated.
Abstract: The reductive dissolution by Na-dithionite of 28 synthetic goethites and 26 hematites having widely different crystal morphologies, specific surfaces and aluminium substitution levels has been investigated. For both minerals the initial dissolution rate per unit of surface area decreased with aluminium substitution. At similar aluminium substitution and specific surface, goethites and hematites showed similar dissolution rates. These results suggest that preferential, reductive dissolution of hematite in some natural environments, such as soils or sediments, might be due to the generally lower aluminium substitution of this mineral compared to goethite.
TL;DR: In this article, the microstructure and solid state phase transformations which take place in aluminium alloys containing lithium have been assessed, in addition to the binary Al-Li system, the Al−Li-Cu, Al −Li-Mg,...
Abstract: The microstructure and solid state phase transformations which take place in aluminium alloys containing lithium have been assessed. In addition to the binary Al–Li system, the Al–Li–Cu, Al–Li–Mg, ...
TL;DR: A model was developed almost 20 years ago which described how precipitation during the quench affected the development of properties of aluminium alloys during subsequent aging treatment as discussed by the authors, which was the basis for an analytical process known as quench factor analysis, that was used to predict the effects of quench path on corrosion characteristics and strength.
Abstract: A model was developed almost 20 years ago which described how precipitation during the quench affected the development of properties of aluminium alloys during subsequent aging treatment. This model was the basis for an analytical process, known as quench factor analysis, that was used to predict the effects of quench path on corrosion characteristics and strength. The purpose of this paper is to provide a theoretical basis for the model and to review how quench factor analysis has been used in solving industrial problems. Several investigators have confirmed that quench factor analysis is an effective predictive method for all quenching conditions save one. The exception is when material has been quenched below the knee of the C-curve and subsequently reheated above the knee before the quench is complete. Applications include the design of quench systems, the development of quench practices which optimize combinations of high strength and low residual stress and distortion, and predictions of the...
TL;DR: Etude, grâce a des techniques de fractographie and de metallographie, du comportement mecanique and de fracture d'aluminium 2124 renforce par 20% de SiC Tentative de separer les contributions des differents mecanismes impliques and identifier le mecanismse de fracture predominant as mentioned in this paper.
TL;DR: In this paper, the evolution of cluster orbital occupation with cluster size is found to be different than that predicted by the "electron droplet" or electronic shell model, and the authors find that these variations may be understood in terms of an extension to the droplet model that introduces the structure of the exact electron-nuclear attraction potential as a perturbation on the smooth spherically symmetric potential of the model.
Abstract: The results of first principles total energy calculations for optimized structures of Aln(n=2–6) are presented in which the evolution of cluster orbital occupation with cluster size is found to be different than that predicted by the ‘‘electron droplet’’ or electronic shell model. We find that these variations may be understood in terms of an extension to the droplet model that introduces the structure of the exact electron–nuclear attraction potential as a perturbation on the smooth spherically symmetric potential of the droplet model. We discuss the limits in which this effect is significant, finding that its importance should diminish with increasing cluster size. The detailed calculations produce cluster ionization potentials that are almost all larger than for the Al atom (5.8 to 6.6 eV), in agreement with experiment. Electron affinities are larger as well, ranging from 0.1 to 2.1 eV. Bond lengths increase from 2.51 A for Al2 to 2.81 A for Al6, but are highly sensitive to cluster electronic state. Co...
TL;DR: In this paper, the energies of voids, stacking-fault tetrahedra and vacancy loops in gold, silver, aluminium, copper, nickel, stainless steel, α-iron and molybdenum have been reexamined as a function of cluster size using established elastic continuum expressions.
Abstract: The energies of voids, stacking-fault tetrahedra and vacancy loops in gold, silver, aluminium, copper, nickel, stainless steel, α-iron and molybdenum have been reexamined as a function of cluster size using established elastic continuum expressions. Stacking-fault tetrahedra and vacancy loops are the most stable small-cluster morphologies in all of the f.c.c. metals and in α-iron. The void is calculated to be the most stable small cluster in molybdenum. These results are in good agreement with recent experimental observations that have been made on high-purity metals. Once a void has nucleated and started to grow, it is very unlikely that it will collapse into a dislocation loop owing to the large energy barrier associated with the conversion process. The continuum calculations and experimental studies imply that impurities (such as gas) are necessary in order for void formation to be stable in most metals.
TL;DR: In this article, it was proved that a composition of the form (Ti, Al)N grows up a TiN lattice with decreasing lattice parameters, up to 30 at.% aluminium.
TL;DR: In this article, 27Al NMR parameters of organoal aluminium compounds of the type (RnAlX3-n)m (n = 0, 1, 2, 3; m = 1,2, 3) and (R2 AlO(CH 2 ) 2 Y )2 (Y = OR′, NR′2) were determined.
TL;DR: By comparing dealuminated Y zeolites with and without non-framework aluminium species, it was shown that the bands at 3693 and 3606 cm−1 in the i.m.n.r. spectrum and the line at 2.6 ppm in the 1H MAS n.
TL;DR: The mouillabilite des metaux a la ceramique Si 3 N 4 est evaluee par mesure de l'angle de contact θ entre la surface peripherique d'une petite goutte sessile de metal fondu and la surface horizontale du substrat entre 1200 K and 1500 K as discussed by the authors.
Abstract: La mouillabilite des metaux a la ceramique Si 3 N 4 est evaluee par mesure de l'angle de contact θ entre la surface peripherique d'une petite goutte sessile de metal fondu et la surface horizontale du substrat entre 1200 K et 1500 K. Determination du travail d'adhesion entre 1200 et 1500 K
TL;DR: In this paper, an empirical expression relating T c to the amounts of moly b-denum and titanium as well as to the aluminum content was derived for a variety of alloys, both ternary and higher order.
TL;DR: In this article, acid leaching of two palygorskites with different octahedral aluminium contents has been carried out in HCl at 20°-70°C.
Abstract: Leaching of two palygorskites with different octahedral aluminium contents has been carried out in HCl at 20°–70°C. The acid concentration was varied in the range 0·05–6 mol. 1−1, using 4–500 g.g−1 liquid to solid ratios. Acid leaching of up to 60% of the octahedral cations did not provoke structural changes or amorphization of the samples. On the bases of the selectivity of extraction of Mg2+, Fe3+ and Al3+, it appeared that most of the octahedral edge positions are occupied by Mg2+, some by Fe3+, and practically none by Al3+. Differences in acid-leaching behaviour between the two palygorskites was better related to accessible surface than chemical composition.
TL;DR: In this paper, the surface charge ( sigma 0)-pH data of a synthetic pure crystalline gibbsite suspension were analyzed with a recently proposed one-step charging model for proton adsorption (one-pK model).
Abstract: Titration curves of a synthetic pure crystalline gibbsite suspension have been made at three NaCl levels. The synthesized gibbsite is characterized by TEM, TGA and X-ray diffraction. The overall BET surface area and the surface area of the edges of the hexagonal crystals are determined. The surface structure of gibbsite is discussed. The surface charge ( sigma 0)-pH data are analysed with a recently proposed one-step charging model for proton adsorption (one-pK model). Analysis of the data suggests that the singly coordinated surface hydroxyls are probably the dominant reactive surface group. Considering these groups as reactive only the titration data could be fitted well with the one-pK model if it is extended with pair formation. Only two adjustable parameters are needed, the Stern layer capacitance and the pair formation constant. Analysis of titration data of aluminium oxides, as presented in recent literature, showed that all sigma 0-pH curves could be described rather well with one and the same set of two parameters, the capacitance of the Stern layer and the pair formation constant. The difference in proton adsorption behaviour between different aluminium (hydr)oxides is mainly caused by differences in the site distribution and the site densities of the aluminium (hydr)oxides involved. The results suggest that pair formation should be taken into account. (Abstract retrieved from CAB Abstracts by CABI’s permission)
Book•
01 Jun 1987
TL;DR: Coverage includes metallic glasses, quasicrystals, aluminium alloys, titanium alloys and microcrystalline steels as mentioned in this paper, as well as other materials such as glass and metal.
Abstract: Coverage includes: metallic glasses; quasicrystals; aluminium alloys; titanium alloys; and microcrystalline steels.
TL;DR: In this article, the steaming of USY (ultrastable Y) zeolite at 500°C has been studied by both 27 Al and 29 Si n.m. spectra.
TL;DR: The response to aluminium concentrations was evaluated for birch seedlings (Betula pendula Roth, formerly Betula verrucosa Ehrh) by using a growth technique that provides stable internal concentrations of nutrients in plants as discussed by the authors.
Abstract: The response to aluminium concentrations was evaluated for birch seedlings (Betula pendula Roth, formerly Betula verrucosa Ehrh.) by using a growth technique that provides stable internal concentrations of nutrients in plants. Aluminium was added as aluminium nitrate and aluminium chloride and pH was kept at 3.8±0.2 by adding HCl or NaOH. The seedlings were grown in two different series of nutrient treatments, either with near-optimum conditions (relative addition rate 25% day−1) or with constant nutrient stress (relative addition rate 10% day−1) before the aluminium addition. Growth reduction occurred at aluminium concentrations greater than 3 mM, and lethal effects at aluminium concentrations greater than 15 mM. In plants subjected to near-optimum conditions before aluminium addition, the internal nutrient concentrations decreased with increasing aluminium concentration for all macronutrients. The concentration of the macronutrients N, K and P decreased gradually with increasing aluminium concentration, while the concentration of Ca and Mg decreased fairly abruptly when aluminium concentrations exceeded 1 mM. The same tendency was observed in nutrient stressed birch seedlings, but the pattern was more scattered. Relative growth rate of the seedlings was not affected by a low Ca/Al ratio. In all treatments, the molar Ca/Al ratio in/on the roots was below 0.2 at the end of the experiments. As decrease in growth occurs only at high aluminium concentrations, there is no reason to suggest that aluminium in acid soils is growth limiting for natural birch stands.
TL;DR: In this paper, the authors used solid-state NMR with magic-angle-spinning (MAS) combined with X-ray powder diffraction, thermal analysis and 57Fe Mossbauer spectroscopy to study two muscovites of different iron contents.
Abstract: Studies of two muscovites of different iron contents, using solid-state NMR with magic-angle-spinning (MAS) combined with X-ray powder diffraction, thermal analysis and57Fe Mossbauer spectroscopy, suggest that dehydroxylation occurs by a homogeneous rather than an inhomogeneous mechanism, forming a dehydroxylate in which the aluminium is predominantly 5-coordinate. On further decomposition at about 1100° C, the tetrahedral layer and interlayer K+ form a feldspar-like phase similar to leucite (KAISi2O6), the remainder forming a spinel, which, contrary to previous suggestions, appears to contain little silicon. Further heating induces the formation of mullite (AI6Si2OP13), and, in the higher-iron sample, corundum (α-Al2O3), in addition to the feldspar-like phase. The presence of the iron impurity enhances the recrystallization reactions and promotes the conversion of mullite to corundum, which eventually becomes the sole aluminous product in the high-iron sample. In samples fired to higher temperatures, only the tetrahedral aluminium resonance is detectable by27AI NMR, probably because most of the iron is located in either the mullite or corundum phases, in which it broadens the octahedral aluminium resonance beyond detection.
TL;DR: In this article, the dependence of the hardness of the TixAl1−xN coatings on the nitrogen partial pressure, the structural features of the coating surface and fracture are discussed.
TL;DR: In this paper, the electrochemical behaviour of pure aluminium in aqueous KOH solutions has been examined by steady state and non-steady state techniques (impedance, potential pulse, potential scan).