Scandium Addition Research Articles

Additions of scandium to superhard titanium oxy-carbonitride coatings : V.Brozek et al. (Ustav Anorganicke Chemie, Prague, Czechoslovakia.) Pokroky Psaskove Metal.,vol 34, no 3, 1996, 26–31. (In Czech.)

Additions of scandium to superhard titanium oxy-carbonitride coatings : V.Brozek et al. (Ustav Anorganicke Chemie, Prague, Czechoslovakia.) Pokroky Psaskove Metal.,vol 34, no 3, 1996, 26–31. (In Czech.)

Emission properties of compounds in the BaO · Sc 2O 3 · WO 3 ternary system

It has been established that the addition of scandium in a variety of forms to thermionic cathodes, both oxide and dispenser types, results in a reduction of work function. The improved emission behavior has been found to be relatively short-lived, however, as ion bombardment causes a loss of the scandium necessary for the enhanced emission properties. While a variety of scandate cathode configurations have been investigated, several compounds have been observed to be common to the various types. The presence of one or more of these compounds appears to be necessary to establish the appropriate surface chemistry and structure. The eight binary compounds and one ternary compound determined to exist in the BaO · Sc 2O 3 · WO 3 ternary system have been evaluated with regard to work function and emission current density. Samples were evaluated with and without an ‘activating’ layer of BaO on the surface. Selected compounds were also mixed with 10 wt% tungsten and evaluated with and without a BaO layer. Finally the emission characteristics of the ternary compound, Ba 3Sc 2WO 9, were investigated as a function of tungsten content (5, 10, 20 and 30 wt%), both with and without a BaO layer on the surface. Comparisons are made between the various samples and data obtained from pure tungsten and Sc 2O 3 10 wt% W , both activated with BaO.

Thermochemistry in the BaO · Sc 2O 3 · WO 3 ternary system

It has been established that the addition of scandium to thermionic cathodes, both oxide and dispenser type, results in reduction in work function. Unfortunately, the improved performance is short-lived, as the scandium is removed by ion bombardment and the low work function surface structure does not readily reform. A wide range of experiments have been reported on different scandate cathode configurations, including those incorporating scandium (or its oxide) into the bulk and as a component of a surface layer. In these studies the primary characterization techniques have been limited to one or more surface probe methods in efforts to correlate surface composition with emission behaviour. Surface analysis techniques yield compositional information, but provide no details as to the nature of phase composition of the surface. A study of the thermochemistry manifested in one of the systems representative of scandate cathodes has been undertaken to advance understanding of the mechanism responsible for the improved emission behaviour. Two isothermal sections of the BaO · Sc 2O 3 · WO 3 ternary system are presented detailing the phase equilibria at 1100°C and 950°C. Information regarding compound occurrence and stability, rates of reaction, and stability of products over a range of temperatures is reported. The structure of a previously reported ternary compound, Ba 3Sc 2WO 9, is discussed and a reaction mechanism describing the evolution of this compound, applicable for many scandate cathode configurations, is presented.

The effect of small additions of scandium on the properties of aluminium alloys

Additions of up to 1 wt% scandium have been made to Al, Al-Mg, Al-Mg-Ag and Al-Zn-Mg alloys and the effects on age-hardening and mechanical properties studied. Scandium levels up to 1% could be retained in solution at solidification rates of about 300 K s−1. The precipitation of Al3Sc at ageing temperatures in the range 563–593 K (290–320 °C) gave significant additional hardening. The low solubility of Sc in the solid state makes it difficult to obtain optimum hardening from Sc and other precipitating elements because of difficulties in solution treatment. The effect of deformation prior to ageing and the temperature-dependent mechanical properties are described.

Effect of scandium on the structure and properties of alloy Al-5.5% Zn-2.0% Mg

Commercial weldable aluminum alloys additionally containing scandium have recently been developed in Russia: thermally nonhardening alloys based on the system Al-Mg (01570, 01523, 01515), and thermally hardening alloys based on the systems-Al-Zn-Mg (01970, 01975) and Al-Mg-Li (01421, 01423). Compared with other weldable aluminum alloys these materials exhibit improved operating properties. This is achieved as a result of a small addition of scandium which displays a high modifying effect and it promotes retention of an unrecrystallized structure for alloys. Results are presented in this article for a study of the effect of scandium content on the structure and properties of pressed strips and cold-rolled sheets of alloy Al-5.5% Zn-2.0% Mg.

Some pressure-composition and electrical resistivity-composition relationships of the PdScH system

Almost without exception, one general effect of alloying different elements with palladium is to produce reductions in the hydrogen-alloy critical temperature T c (α, β) with respect to ranges of coexistence of the α and β (α') phases. At near-ambient temperatures ( e.g. 25 °C) this is reflected by decreases in the ranges of hydrogen contents corresponding to the main (pressure-invariant) regions of the α ⇌ β phase transition p α, β ( p β, α ). In quite close parallel to trends of change of heats of hydrogen absorption, alloying elements can be divided into two groups differentiated by whether they produce either increases or decreases of p α, β . One factor which has been advanced to have a major influence on these differences has been that of the size of the alloying element and its effect on the initial lattice constant of the palladium host. Comparisons of results obtained in measurements of ( R R 0 )-n and p- n relationships for series of palladium alloys with titanium, vanadium, zirconium and niobium have recently provided some support for a modified size-based correlation. These comparisons seemed to suggest a possibility that the smaller atomic radius of scandium relative to other group III transition elements might perhaps result in a trend of increasing p α, β with increasing scandium content in palladium. However, experiments at 25 and 50 °C have now indicated that increasing additions of scandium produce an overall marginal trend of decreasing values of p α, β in qualitative line with effects expected from an “expanded alloy” characterization.

The Effect of Scandium Addition on the Mechanical Properties of Pure Aluminium and of an AlMg6 Alloy

The Effect of Scandium Addition on the Mechanical Properties of Pure Aluminium and of an AlMg6 Alloy

The workability and ductility of molybdenum arc melted with small amounts of scandium

Molybdenum was arc melted with various amounts of scandium up to 0.5 wt.%, and the workability of the ingot and the bend ductility of the stress-relieved metal were studied. In contrast with other strong oxide formers, such as titanium and zirconium, scandium scavenges molybdenum by forming scandium oxide slag which rises to the surface of the molten metal. Consequently, molybdenum is refined by the addition of scandium, and this results in a marked improvement in its workability and ductility. The addition of an optimum amount of scandium (0.2 wt.%) results in a reduction in the working temperature of an ingot to about 673 K and the ductile-to-brittle transition temperature to 163 K.

Spectrophotometric Determination of Palladium and Bismuth(III) with Semimethylxylenol Blue

Abstract Procedures are described for the spectrophotometric determination of palladium and bismuth(III) with Semimethylxylenol Blue (SMXB). SMXB reacts with palladium and bismuth(III) to form reddish-violet 1:1 complexes. The optimum pH ranges for the color development are pH 1.0–1.7 for palladium and pH 1.0–1.4 for bismuth(III). The absorption maxima of the colored solutions lie at 565–568 nm and at 568–570 nm, respectively. Beer’s law is obeyed over the range of 0.4–3.2 μg cm−3 of palladium and 0.4–4.0 μg cm−3 of bismuth(III), and the sensitivities of the determinations are 4.0×10−3 μg Pd cm−2 and 6.1×103 μg Bi cm−2 for 0.001 of absorbance. For the palladium determination, gallium, tin(IV), bismuth(III), scandium, zirconium, and iron(III) interfere, but tin(IV), scandium, zirconium, and iron(III) can be masked by the addition of fluoride. For the bismuth(III) determination, gallium, tin(IV), scandium, zirconium, and iron(III) interfere, but the effect of iron(III) is eliminated by the addition of l-ascorbic acid, and tin(IV) and scandium can be masked by fluoride. A consecutive determination of palladium and bismuth(III) by the difference of the rates of color developments for their complexes was also studied.

Mechanism of oxide adherence on Fe-25Cr-4Al (Y or Sc) alloys

Oxidized alloys of Fe-25Cr-4Al, some containing small additions of elements (Yttrium or Scandium) which strongly promote oxide adherence, have been subjected to extensive structural studies by scanning, replication, and transmission electron microscopy as well as other techniques. The morphological details of the Al2O3 scales, which develop on these alloys during high temperature oxidation, and the structural changes at the oxide-substrate interfaces are discussed with respect to oxidation kinetics and oxide adherence. The oxide scales grow into the alloys at rates consistent with the diffusion of oxygen down grain boundaries of the fine-grained scales. Yttrium and expecially scandium additions tend to increase oxidation rates by providing rapid diffusion paths in the form of yttria and scandia stringers. More importantly, the morphological data led to the conclusion that the spallation of nonadherent scale is caused by distributions of small voids at the oxide-substrate interface. Consistent with this conclusion, it is found that the oxide scale is tenaciously adherent when voids are absent, as is the case when yttrium or scandium is added to the alloy. It is maintained that these alloy additions promote oxide adherence by forming vacancy complexes with excess vacancies or by providing internal oxide boundaries for the condensation of excess vacancies, which would have otherwise condensed at the oxide-substrate interface and formed the voids responsible for oxide spallation. The role of vacancy sinks is further confirmed by showing that oxide adherence is promoted in Fe-25Cr-4Al, in the absence of yttrium of scandium, by a distribution of Al2O3 particles. This result indicates that particles, which have been used in engineering alloys for strengthening purposes, can also promote oxide adherence. The morphological data are also discussed with respect to other mechanisms that had been proposed for oxide adherence.

Effect of Trace Scandium Addition on Al-6mg Alloy

Ageing behaviour of Al-6Mg alloy doped with trace amount of scandium was investigated. Cold rolled and as cast samples were aged isochronally for 60 minutes at different temperature up to 500°C. Some samples were aged isothermally at 300°C for different periods ranging from 30 to 240 minutes. Hardness of the alloys was measured to study the age hardening effect due to scandium addition. Resistivity changes with annealing time and temperature were measured to understand the precipitation behaviour and recovery of strain of the alloy. Attempts were also made to understand quantitatively the grain refining effect of scandium in Al-6Mg alloy. Moreover, a kinetic analysis for precipitation in cold rolled experimental alloys has been carried out by Differential Scanning Calorimetric Technique to gain a clear understanding about the kinetics of recrystallisation and recovery in Al-Mg alloy with or without scandium additions. Keywords: Al-Mg alloys, Age hardening, Resistivity, Dendrites, Second phase. Journal of Mechanical Engineering Vol.36 Dec. 2006 pp.12-17DOI = 10.3329/jme.v36i0.806

The Texture Behavior of Al-Mg-Sc Alloys

Three alloys of Al-Mg with and without scandium are cold worked at different percentage and then annealed. The texture behavior of the alloys is studied by X-ray diffraction technique. The X-ray diffraction analysis is done using a PHILIPS PW1830 diffractometer with Cu-Kα radiation. It is found that the addition of scandium in Al-6Mg alloy influences the development of texture. The cube texture (100)[001] is preferred in the alloy in the initial stages of deformation, whereas beyond 50% deformation, the maximization of (220) intensity indicates that a mixed texture is developed on increasing the percent reduction. Keywords: Al-Mg alloys, Cold working, Annealing, Texture, X-ray diffraction.doi:10.3329/jme.v37i0.814Journal of Mechanical Engineering Vol.37 June 2007, pp.10-17

Initial Permeability and Derived Anisotropy of Scandium-Substituted Yttrium Iron Garnets

Effects of nonmagnetic scandium octahedral substitution in yttrium iron garnet were studied in a series of polycrystalline garnets having the unit formula Y3ScxFe2−xFe3O12 where x was varied from 0 to 1.7. Measurements of the lattice parameters, spontaneous magnetization, Curie temperature, and the initial permeability as a function of frequency and temperature are reported. The lattice parameter varied linearly from 12.376±0.003 Å for x=0(YIG) to 12.495±0.005 Å for x=1.5 Sc3+. Single-phase garnet was not obtained for x>1.5. The apparent spontaneous magnetization at T=0°K and the Curie temperature dependence on substitution are qualitatively explained using Gilleo's statistical theory of incomplete super-exchange interactions. The initial permeability at room temperature is strongly affected by the addition of scandium, increasing from 120 (YIG) to a maximum value of 1934 (x=0.9 Sc3+) and then to unity for larger x values. The value of 1934 is the largest room-temperature initial permeability reported in garnets to date; the corresponding Curie temperature is 320°K. The frequency spectra of the initial permeability for x≤0.7 Sc3+ display the usual two characteristic loss peaks identified with domain wall motion and domain rotation mechanisms. The high-frequency (domain rotation) peak appears only as a shoulder on the broad wall motion resonance. The wall motion peak does not exhibit electronic diffusion effects. In the absence of experimental anisotropy data on Sc3+ substituted garnets, the temperature dependence of the initial permeability was used to deduce K1(T) by assuming that the rotational permeability contributes ∼20% to the total measured permeability. The rotational resonance frequencies calculated using the deduced anisotropy constants at room temperature agree quite well with experimental data. The derived K1(T) seem to be in good agreement with the available single-crystal experimental data.