Showing papers on "Aluminium published in 1976"
TL;DR: In this paper, a fluorimetric method using the reagent Lumogallion has been investigated and found to have a detection limit of 0.05 µg l−1 of aluminium and a coefficient of variation of 5% at the 1.0 µg L−1 level and 2.7% at 22 µgL−1 levels.
Abstract: Dissolved aluminium occurs in natural waters down to concentrations of 1 µg l–1 or less. There are very few methods that are sufficiently sensitive to measure down to these levels. A fluorimetric method using the reagent Lumogallion has been investigated and found to have a detection limit of 0.05 µg l–1 of aluminium and a coefficient of variation of 5% at the 1.0 µg l–1 level and 2.7% at the 22 µg l–1 level. The only anionic interference likely to be important in most natural waters is that from fluoride, and this interference can be dealt with by using an incremental calibration procedure. For acidic waters iron is a potential interferent but has no significant effect at concentrations of less than 100 µg l–1. In water abnormally rich in dissolved organic material there may be competition for the dissolved aluminium between the natural organic ligands and the Lumogallion. This effect can be overcome by ultraviolet irradiation prior to analysis for aluminium. The analysis detects all forms of aluminium in filtered natural water samples except when the aluminium occurs in stable mineral structures, e.g., clay particles small enough to pass through the filter. Aluminium adsorbed on the surface of such particulate material appears to be determined.
229 citations
225 citations
TL;DR: In this paper, the anisotropic work function of smooth (100), smooth (111), and (110) faces of a single crystal were cleaned through a mild cyclic treatment of ion bombardment and annealing.
176 citations
TL;DR: The electrochemical behavior of aluminium alloyed with small amounts (up to 0.2%) of indium, gallium and thallium has been investigated in this paper, and it has been found that these additions result in:============
Abstract: The electrochemical behaviour of aluminium alloyed with small amounts (up to 0.2%) of indium, gallium and thallium has been investigated. It has been found that these additions result in:
(a)
A considerable shift of the rest potential in the negative direction (to 1.4–1.7 V versus SCE),
(b)
A significant increase of the passivating current density (up to 0.1–1 Acm−2) and
(c)
A considerable decrease in the negative difference effect (increase of the faradaic efficiency to
99.5%) compared to the behaviour of pure aluminium. Except for the gallium alloy, the rate of corrosion of the alloys in neutral salt solutions is also decreased compared to that of pure aluminium. A ternary alloy, Al-0.01 In-0.01 Ga, exhibited a more negative rest potential than the Al-In alloy and a corrosion stability superior to that of the Al-Ga alloy. The negative difference effect was found to depend on the cation of the neutral salt in solution. The lowest effect was obtained in ammonium chloride solutions.
139 citations
TL;DR: The chemistry of the surface of oxides depends to a large extent on the quantity and type of both physically and chemically (OH groups) absorbed water as discussed by the authors, and infrared spectroscopy coupled with a variety of chemical exchange processes has provided useful information on the nature and stability of the adsorbed species, and on the interaction of surface hydroxyl groups with adsorbates at the solid/vapour and solid/liquid interfaces.
Abstract: The chemistry of the surface of oxides depends to a large extent on the quantity and type of both physically and chemically (OH groups) absorbed water. Infrared spectroscopy coupled with a variety of chemical exchange processes has provided useful information on the nature and stability of the adsorbed species, and on the interaction of the surface hydroxyl groups with adsorbates at the solid/vapour and solid/liquid interfaces. Electrochemical techniques are used to study the oxide/aqueous solution interface to provide surface charge data and establish zero points of charge, both of which are related to the character of the hydroxyl group and its environment. This paper briefly reviews the application of these methods to the oxides of titanium, silicon and aluminium, in both the pure and mixed forms, and to the study of the deposition of one oxide on the surface of another.
131 citations
124 citations
TL;DR: In this paper, the surface charge of several natural kaolinites was measured in the pH range 3-10 using an exchange technique, and it was found that the positive surface charge on kaolinite is due to exposed alumina such as is found on oxide surfaces.
Abstract: The surface charge of several natural kaolinites was measured in the pH range 3-10 using an exchange technique. The positive charge was found to increase with decreasing pH and sometimes to increase with increasing ionic strength; it occurred on the kaolinites at pH values as high as 9 and 10 and was particularly evident at high ionic strengths. The positive surface charge on kaolinites is thought to be due to exposed alumina such as is found on oxide surfaces. Aluminium was found to dissolve from kaolinite at pH values beiow about 6.5. Aluminium dissolution increased with decreasing pH and time. When the proportion of dissolved aluminium ions balancing negative surface charge was taken into account, the negative and net negative surface charge on kaolinite was concluded to be largely due to pH independent charge resulting from isomorphous substitution, together with some pH dependent charge due to exposed SiOH sites. If Na+ was the index cation, dissolved aluminium ions from the clay replaced some of the Na+ balancing the negative surface charge. However, when Cs+ was the index cation, less Cs+ balancing the negative surface charge on the clay was replaced by dissolved aluminium. As the concentration of either Na+ or Cs+ was increased, less dissolved aluminium replaced the index cation as a counteraction to the negative surface charge.
111 citations
TL;DR: In this article, the formation energy of vacancies was measured under conditions of very low vacancy concentrations for ultrahigh purity aluminium, after quenching down to 4 K. A value of (0.69 ± 0.03) eV was found.
Abstract: The formation energy of vacancies is measured under conditions of very low vacancy concentrations for ultrahigh purity aluminium, after quenching down to 4 K. A value of (0.69 ± 0.03) eV is found. Similar experiments made using pure magnesium yield a formation energy of (0.79 ± 0.03) eV. It is shown that in magnesium vacancies are mobile well below room temperature.
107 citations
TL;DR: In this paper, a method to disperse oxide particles (primarily alumina) in the matrix of aluminium alloys, involving additions of particles to alloy melts prior to the solidification of castings, is described.
106 citations
TL;DR: In this article, the authors investigated the acoustic emission during tensile tests for several types of aluminium alloys and found that the mean square amplitude of the continuous emission is proportional to strain rate and sample length.
Abstract: The acoustic emission during tensile tests is investigated for several types of aluminium alloys. It is found that the mean square amplitude of the continuous emission is proportional to strain rate and sample length. It is assumed that the continuous emission is generated by dislocation loops, which are created continuously at Frank-Read sources. According to this model the mean square amplitude of the continuous emission U2 is proportional to the total length of the mobile dislocations L and the size of the loops l: ∼LI. Information about l was taken from Kuhlmann and Wilsdorf's observations of slip lines at the surface of deformed aluminium single crystals.
83 citations
TL;DR: Using channeling and nuclear reaction analysis methods, the authors deduced that implanted elements occupy the tetrahedral position and are associated with the vacancies created by the implantation, and they used this information to determine the position of implanted elements in a single crystal.
TL;DR: The initial aluminum hydroxide gel precipitate resulting from the reaction of aluminum chloride or aluminum sulfate with ammonium hydroxides is shown by potentiometric titration, chemical analysis, and the ratio of bound hydroxid to aluminum to fit a polymer model described previously.
TL;DR: In this paper, a bath consisting of and an alkali metal bromide such as dissolved in a suitable mixture of aromatic hydrocarbons was operated under conditions resembling industrial operation, and the effect of bath composition on the quality of the plated product was discussed in detail.
Abstract: Electroplating of aluminium on copper and steel substrates was conducted at room temperature. The bath consisted basically of and an alkali metal bromide such as dissolved in a suitable mixture of aromatic hydrocarbons. The bath was operated under conditions resembling industrial operation. Oxygen and humidity were removed by bubbling nitrogen through the bath. The effect of bath composition on the quality of the plated product is discussed in detail. Transference numbers were measured. The aluminium is shown to be present in the form of a negative ion , the transference number of which is larger than that of the solvated positive ion. The reactions taking place during deposition and dissolution of aluminium in this system are discussed in detail.
TL;DR: The role of alloying additions in modifying the recrystallization behavior of aluminium alloys is discussed in this article, and possible deformation mechanisms in the newer alloys are discussed to demonstrate their relative importance.
Abstract: Although the phenomenon of super plasticity in metals was recognized for many years, the majority of alloys that were shown to be super plastic consisted of two phases present in approximately equal volumes. The only aluminium alloys known to be superplastic were of eutectic composition and did not, in general, possess other properties that would make them commercially attractive. More recently, superplasticity has been obtained in relatively dilute aluminium alloys with more useful user properties. A brief summary is given of the aluminium alloys of eutectic composition that have been shown to exhibit superplasticity, but the authors are mainly concerned with the newer, relatively dilute alloys. The roles of alloying additions in modifying the recrystallization behaviour, because of both their presence in precipitate particles and their influence in solid solution, are considered. Additionally, possible deformation mechanisms in the newer alloys are discussed to demonstrate the relative importanc...
TL;DR: In this paper, it is suggested that the metals extracted by acetylacetone are essentially bound to the organic matter and they behave as junctions of a net composed of polymeric chains of soil organic matter.
Abstract: Summary
Extraction of five soils with acetylacetone in benzene does not change their particle-size distribution, compared with no pre-treatment or dispersion, but it decreases the water stability of soil aggregates. The decrease is closely related to the extent of the extraction of iron and aluminium by acetylacetone in benzene from soils.
The metals extracted by acetylacetone are essentially bound to the organic matter. It is suggested they behave as junctions of a net composed of polymeric chains of soil organic matter. The mesh, which exerts a protective action on soil aggregates, is weakened at the junctions of polymeric chains after the removal of metals so that the stability to the disrupting action of water is decreased.
TL;DR: In this article, a Cameca ion analyser was used to examine barrier-type anodic films grown on aluminium in neutral phosphate, chromate or phosphate/chromate solutions and in phosphate and chromate solutions containing relatively small amounts of chloride ion.
TL;DR: In this paper, the magnetic hardness at cryogenic temperatures increases rapidly around a composition with x = 0.30 at 4.2 K. This low-temperature magnetic hardness appears to be connected with the presence of highly energetic domain walls.
Abstract: Aluminium substitution for iron in Sm2Fe17 results in stabilization of the Th2Zn17 structure. Compounds are homogeneous from x = 0.20 to x = 0.50 in Sm0.105Fe0.895−xAlx when annealed at 800 °C. In this structure, Fe and Al are statistically distributed on 6(c), 9(d), 18(f) and 18(h) sites. Materials with x = 0–0.15 are composed of the Th2Zn17 type and Fe. The magnetic hardness at cryogenic temperatures increases rapidly around a composition with x = 0.30. A value of coercive force, Hc = 15 kOe, is obtained both on bulk and powder material with x = 0.50 at 4.2 K. This low-temperature magnetic hardness appears to be connected with the presence of highly energetic domain walls. The mechanism of demagnetization involves domain nucleation, in contrast with Sm0.167Co0.833−xAlx where demagnetization is predominantly governed by domain wall pinning.
TL;DR: In this article, the dissolution kinetics of Nb, Ta, Mo and W in liquid aluminium have been investigated by the rotating disk method at 700-850 °C, and the dissolution process ( ω = 4-40 rad/s) was found to be diffusion controlled.
Abstract: The dissolution kinetics of Nb, Ta, Mo and W in liquid aluminium have been investigated by the rotating disk method at 700–850 °C. The dissolution process ( ω = 4–40 rad/s) was found to be diffusion-controlled. Values of the solubilities of the refractory metals, the dissolution rate constants, and the diffusion coefficients in liquid aluminium have been obtained. The temperature dependences of solubilities, dissolution rates and diffusion coefficients are described by the Arrhenius equation. Under the conditions of the present investigation, a layer of the most Al-rich intermetallic phase appropriate appears at the aluminium-refractory metal boundary over the investigated temperature range. Intensive dissolution of the refractory metal in liquid aluminium prevents the formation of the intermetallic layer for a considerable period of time. In this way, bimetallic specimens with a contact zone strength exceeding that of aluminium may be obtained.
Patent•
27 Dec 1976TL;DR: In this article, a catalyst suitable for steam reforming, especially at low temperatures and high pressures, which is resistant to polymer deactivation, comprises nickel, alumina and ruthenium, optionally together with an oxide, hydroxide or carbonate of an alkali metal or alkaline earth-metal.
Abstract: A catalyst suitable for steam reforming, especially at low temperatures and high pressures, which is resistant to polymer deactivation, comprises nickel, alumina and ruthenium, optionally together with an oxide, hydroxide or carbonate of an alkali metal or alkaline earth-metal wherein the amount of ruthenium does not exceed 0.8% by weight of the weights of the other components of the catalyst. The nickel and aluminium components of the catalyst are prepared by coprecipitation with the nickel and aluminium components, by impregnation of the precipitated nickel and aluminium components or by physical blending of an insoluble ruthenium compound with the precipitated nickel and aluminium components.
TL;DR: The number of secondary electrons per unit energy, N (E), and the derivative dN/dE have been measured carefully for clean and contaminated aluminum using a four-grid hemispherical retarding field energy analyzer.
Abstract: The number of secondary electrons per unit energy, N (E), and the derivative dN/dE have been measured carefully for clean and contaminated aluminum using a four‐grid hemispherical retarding‐field energy analyzer. At primary beam energies of 0.5, 1.0, and 1.5 keV, a broadened curve of N (E) vs energy E was obtained for clean aluminum; the more normal narrow curve was obtained when the surface was contaminated with oxygen. This structure is believed due to plasmon decay excitation of electrons in the solid.
TL;DR: A Cameca ion analyser has been used to examine aluminium surfaces, supporting barrier-type anodic films ca. 720A thick, after natural immersion for 1-25 h in 1M chloride and chromate/dichromate solutions of varying pH, and neutral 1M phosphate solution as mentioned in this paper.
Patent•
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04 Jun 1976
TL;DR: In this paper, a process for the treatment of titanium dioxide pigment is described, in which there is added to a slurry of the pigment a compound of silicon, of aluminium, of zirconium and of titanium, changing the pH of the slurry to 7.5 to 8.5 prior to adding a compound.
Abstract: A process for the treatment of titanium dioxide pigment in which there is added to a slurry of the pigment a compound of silicon, of aluminium, of zirconium and of titanium, changing the pH of the slurry to 7.5 to 8.5 prior to adding a compound of silicon, an acidic compound of aluminium and an alkaline compound of aluminium, thereby producing a coated pigment.
Patent•
05 Mar 1976TL;DR: In this article, a metal article having perforations therein whose transverse cross-sectional dimension is less than 0.4 mm has formed thereon a surface diffusion alloy by applying a refractory filter element to the workpiece surface prior to the diffusion treatment.
Abstract: A metal article having perforations therein whose transverse cross-sectional dimension is less than 0.4 mm has formed thereon a surface diffusion alloy by applying a refractory filter element to the workpiece surface prior to the diffusion treatment, the filter element being a refractory felt based on metal fibres including chromium in a proportion by weight of from 10 to 60%. The felt is oxidized to give a layer of chromium oxide. This is followed by conventional thermochemical powder diffusion treatment in the presence of at least one chromium oxide-reducing element selected from aluminium, yttrium, titanium and the lanthanides.
TL;DR: In this paper, the authors investigated the dependence of acoustic emission power and spectra for deformation of aluminum alloys over a wide frequency range of 100 kHz to 4 MHz, and found that acoustic emissions were proportional to the first power of the plastic strain rate times the gauge length of the specimen.
Abstract: Strain‐rate dependence of acoustic‐emission power and spectra for deformation of aluminum alloys is investigated over a wide frequency range of 100 kHz to 4 MHz. In case of Al‐Cu‐Mg alloy (2024) and pure aluminum (1100), it is found that acoustic‐emission power is proportional to the first power of the plastic strain rate times the gauge length of the specimen. Normalized acoustic‐emission power spectra show no significant change at a given strain depending on the strain rate, though they vary with the strain in early stages of deformation. In case of Al‐Mg alloy (5056), repeated bursts of acoustic emission are recorded accompanied by repeated discontinuous yielding. The mode of inhomogeneous deformation and the pattern of acoustic emission vary with the strain rate.
TL;DR: The presence of soluble polymeric complexes in dilute solutions of aluminium and phosphate at 25°C was demonstrated by paper electrophoresis and confirmed by chemical analyses and measurements of 32 P specific activities as discussed by the authors.
Abstract: The presence of soluble polymeric complexes in dilute solutions (10–30 μM) of aluminium and phosphate at 25°C was demonstrated by paper electrophoresis and confirmed by chemical analyses and measurements of 32 P specific activities. Complexed aluminium and phosphate were not determined by colorimetric procedures without preliminary hydrolysis in 1 N HCl at 80–90°C. The formation of aluminophosphate complexes was maximal around pH 5 when, at an initial P/Al mole ratio of 1.6, 3 moles of P were complexed with 4 moles of Al. At pH 6.9, however, only 1 mole of P was removed for every 10 of Al, suggesting that hydroxyaluminium polymers predominated at higher ratios of OH-ions to H2PO4-ions. re]19750523