Boundary Solid Solution Research Articles

Physicochemical interaction in the Cs3Sb2Br9-Cs2TeBr6 system: The phase diagram and the nature of the interaction of components

Phase equilibria in the Cs3Sb2Br9-Cs2TeBr6 system were studied for the first time by differential thermal and X-ray powder diffraction analyses. The state diagram of the system was constructed. It was found that the system is of eutectic type and is characterized by the formation of boundary solid solutions based on the initial ternary compounds.

Interaction in the Tl2S-SnS-PbS quasi-ternary system

Phase equilibria in the Tl2S-SnS-PbS quasi-ternary system were studied by differential thermal, X-ray powder diffraction, and microstructural analyses. The following schemes were constructed: the state diagrams of the partially quasi-binary sections Tl4SnS3-Tl4PbS3, PbS-Tl4SnS3, and PbS-Tl2Sn2S3, the isothermal section at 520 K, and the projection of the liquidus surface to the concentration triangle of the Tl2S-SnS-PbS system. The coordinates of invariant points and the boundaries of solid solutions were determined.

The spinel and cubic rocksalt solid-solutions in the Li–Mn–Ni oxide pseudo-ternary system

Abstract Solution-based combinatorial samples of lithium manganese nickel oxide were synthesized and studied by X-ray diffraction in order to map out the pseudo-ternary system over the entire metal composition ranges. More than 300 compositions were prepared and many duplicates were made to test reproducibility. The samples were made by heating to 800 °C in an oxygen atmosphere and two cooling methods were tested: quenching as well as a slower cooling rate. A partial phase diagram in air was also determined wherein regions showing extreme lithium loss were avoided. This article focuses on two solid solutions: the spinel and rocksalt regions. Both are larger than previously suspected which is of significance for composite electrode materials of Li-ion batteries Part of the rocksalt solid solution region shows a new structure with a cubic lattice, similar to that of NiO rocksalt but with ordering of manganese, lithium and metal site vacancies such that the scattering pattern resembles that of Ni 6 MnO 8 . The results obtained here confirm that the spinel structures have oxygen site vacancies when quenched even when synthesized in pure oxygen, while slow cooling relieves these vacancies. The boundaries are found to move during slow cooling in such a way that is consistent with the reaction equilibrium favoring the high oxygen content spinel phases. The high level of precision obtained in drawing the solid solution boundaries and the tie-lines in co-existence regions using quantitative phase analysis establishes the use of combinatorial samples in mapping complex pseudo-ternary diagrams.

The Quasi-Ternary System Cu2Se-Ga2Se3-GeSe2

The quasi-ternary system Cu2Se-Ga2Se3-GeSe2 was investigated using the methods of differential thermal and x-ray analysis. An isothermal section at 770 K and a liquidus surface projection of the phase diagram were constructed. The existence of the quaternary phase CuGaGeSe4, the boundaries of solid solutions ranges of the system compounds were established.

Effect of low-melting additives on the structure, phase transitions, and dielectric properties of 0.36BiScO3 · 0.64PbTiO3 ceramics

Ceramic samples of 0.36BiScO3 · 0.64PbTiO3 morphotropic phase boundary solid solutions modified with low-melting additives (bismuth, nickel, and manganese oxides and lithium fluoride; < 5 wt %) have been prepared by solid-state reactions, and the phase formation, microstructure, and dielectric properties of the ceramics have been investigated. The additives were shown to lower the formation temperature of the solid solutions and raise the density of the ceramics. Varying the heat treatment conditions, we obtained single-phase samples, both large-grained, ranging in grain size from a few to tens of microns, and fine-grained, with a submicron-scale microstructure. The ceramics were shown to form through liquid-phase sintering. The additives influenced the dielectric properties, electrical conductivity, Curie temperature, and dielectric relaxation of the ceramics.

Phase equilibria in the Ag4SSe–PbTe system

The phase diagram of the Ag4SSe–PbTe system is built using XRD, DTA and microstructural analysis, as well as density and microhardness measurements. An intermediate compound Ag4SSe·2PbTe exists in it with unit cell parameters of the α-phase: a=0.3510nm, b=0.3053nm, c=0.2951nm, α=99.07°, β=94.37°, γ=89.31°. The compound melts incongruently at 630°C and goes through a polymorphous transition at Tα↔β=400°C. Boundary solid solutions based on the initial compounds Ag4SSe and PbTe, as well as on the new Ag4SSe·2PbTe phase are observed.

Phase equilibria in the PbSb 2Te 4–InSb system

A phase diagram of the PbSb 2Te 4–InSb system, which is polythermal cross section of the three-component PbTe–Sb 2Te 3–InSb system, was built using DTA, XRD, microhardness and density measurements. The system contains the PbSb 2Te 4·(2 ± δ)InSb compound of variable composition, incongruently melting at 530 ± 5 °C, and with asymmetric area of homogeneity shifted to the side rich in InSb (+ δ = 0–2). The PbSb 2Te 4·2InSb compound crystallizes in orthorhombic symmetry with unit cell parameters: a = 7.7640 Å; b = 6.4144 Å; and c = 3.6010 Å, α = β = γ = 90°. The system also contains PbSb 2Te 4 and InSb based boundary solid solutions extended from 0 to 10 and from 95 to 100 mol% InSb, respectively, at room temperature.

Quasi-ternary system CuGaS2–CuInS2–2CdS

Abstract The quasi-ternary CuGaS 2 –CuInS 2 –2CdS system was investigated using differential-thermal analysis and phase X-ray diffraction. Isothermal section of the system at 870 K and projection of the liquidus surface were constructed. Limits of the boundary solid solutions were determined.

Quasi-ternary system Cu 2GeS 3–Cu 2SnS 3–CdS

Phase equilibria in the quasi-ternary system Cu 2GeS 3–Cu 2SnS 3–CdS were investigated by differential thermal analysis and XRD. Isothermal section of the system at 670 K, liquidus surface projection and the perspective views of the phase diagram were constructed. The boundaries of solid solution ranges of the system components and the intermediate phases were determined.

Iodine‐Promoted Synthesis of Structurally Ordered AlPd5

AbstractThe boundary conditions and scope of catalytically stimulated synthesis of ordered intermetallics from solid metals are elucidated. The method is applied to the preparation of AlPd5. Its crystal structure has been determined by means of x‐ray powder diffractometry. AlPd5 forms a structurally unmatched ordered variant of the cubic close‐packing of spheres. Above 900 K AlPd5 is merged in the fcc boundary solid solution AlxPd1−x by a first order phase transition. The particular arrangement of the minority component Al and the associated structural distortions are analysed with regard to chemical bonding against the background of the enthalpy‐driven disorder‐order transition.

A Comment on “Hydrogen-Boron Interaction and Its Effect on the Ductility and Fracture of Ni 3Al”

Cohron et al. recently reported that in the presence of hydrogen boron embrittles polycrystals of Ni{sub 3}Al. The concern is not the observations. Clearly, the environment is a major factor in the case examined. The issue is whether the effect is characteristic of the intermetallic per se. The alternative is that it is related to an attack on nickel-enriched regions adjacent to the grain boundaries. Cohron et al. did not describe the grain boundaries in their alloys. However, other investigators using high resolution techniques have found that at least some grain boundaries in similarly Ni-rich material exhibit nickel concentrations well above the overall alloy composition. Boron increases this enrichment in some cases leading to a detectable disordered grain boundary solid solution. It seems fair to assume that the grain boundaries in Cohron`s alloys were similarly enriched. The other point to note is that hydrogen embrittles both elemental nickel and Ni-based superalloys. It is suggested, therefore, that the embrittlement reported by Cohron et al. may be related more to an attack by hydrogen on Ni-enriched grain boundaries, made richer by the addition of boron, than to an attack on NiAl per se. Consistent with this suggestion are the results of amore » new study on strain rate effects, presented elsewhere. The key point of that study is that high rate deformation (which suppresses environmental attack) does not impart ductility to stoichiometric Ni{sub 3}Al, but does impart ductility to Ni-rich material. The difference is that the stoichiometric alloy does not contain grain boundaries enriched in nickel, implying that its brittleness is an intrinsic quality.« less

Vanadium-doped TiO 2 catalysts. A unifying picture of powders and suspensions

Anatase powders, both pure and vanadium-doped, were subjected to acid-base leaching cycles. The different samples were characterized with respect to chemical composition, morphology and surface area. The effects of the different treatments on the chemical state of the surface and on the electrification at the solid-solution boundary were investigated, respectively, by X-ray photoelectron spectroscopy and electrophoretic mobility measurements. The stability of the aqueous suspensions was measured by sedimentation tests. The results of the different determinations are cross-compared in order to produce a general description of the catalysts.

Energy of an excited atomic configuration in alloys

We investigate a model relating the excitation caused by ion bombardment of a metal substrate to the formation of an additional energy minimum relative to the equilibrium state for the excited atomic configuration. We present an explanation of the effects of changing the boundaries of solid solutions during ion implantation.

Determination of the phase boundaries of the wustite solid solution within the context of reduction tests

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Binary system neopentylglycol/pentaglycerin

The phase diagram of the plastic crystals Neopentylglycol (HPG) and Pentaglycerin (PG) has been established from 288 Κ until the liquid state. The NPG/PG system exhibits a demixing region in the solid state as a consequence of the difference between the ordered low-temperature forms of the pure compounds; the solid solution boundaries have been determined (0.07 and 0.53 molar fraction of PG) at 288 K. The equilibrium domains between the two solid phases and the plastic phase show an eutectoid invariant, with eutectoid composition of 0.29 ± 0.02 molar fraction of PG and eutectoid temperature of 298.1 ± 1.1 K. In the plastic phase, total miscibility is observed and, from a crystallographic point of view, an ideal behaviour can be assumed for the alloys. The plastic-liquid equilibrium shows a Gibbs minimum corresponding to a concentration of 0.21 ±0.02 molar fraction of PG and a temperature of 379.6 ± 2.0 K.

Alumina‐Silica Phase Diagram in the Mollite Region

The alumina‐silica phase relations of samples annealed in oxygen and quenched were studied by optical microscopy, image analysis, X‐ray diffraction, and the electron microprobe. The solid solution boundaries of mullite changed with increasing temperature and joined at 1890°C and a composition of 77.15 wt% alumina. The melting point of mullite was 189°C with a peritectic between 76.5 and 77.0 wi% alumina.

Aluminum base heat-resistant alloys with additions of iron from powdered materials obtained by the method of rapid solidification of the melt

When alloys of the system Al-Feare obtained by the method of RSM, the range of the existence of the boundary solid solution is extended to iron concentration of about 6% against 0.052 under equilibrium conditions, i.e., almost 100 times. Thanks to the high degree of supersaturation of the solid solution and the dispersion of the primary intermetallic phases from the extruded RSM aluminum alloys with 8–10% iron, compact semiproducts were obtained which in strength and heat resistance are not inferior to the best industrial marques.

The Stress Corrosion Susceptibility of 7075 Al-Zn-Mg-Cu Alloys Tempered from T6 to an Overaged T7X

Abstract The influence of overaging a 7075 Al-Zn-Mg-Cu alloy from T6 to T7X type temper on the composition of the near grain boundary solid solution has been investigated. Changes in measured stress corrosion crack growth kinetics resulting from such heat treatment have been correlated with differences in the electrochemical properties of the grain boundary solid solutions brought about by solute microsegregation. Microanalysis has been accomplished with a spatial resolution of < 20 nm using a scanning transmission electron microscope (STEM) combined with energy dispersive X-ray analysis.

The structure and adhesion of coatings deposited by wire explosion spraying

The coating method and the characteristics of wire explosion spraying, as developed in our laboratory, are described. A study of the mechanism of adhesion between the coating and substrate in two metal systems, W-mild steel and W–Cu which differ in mutual solubility, is discussed. Metallographic observations using electron probe and soft x ray confirmed the presence of a solid solution boundary layer in the case of the mild steel substrate, with a critical shearing stress of adhesion measured by our method ranging from 20 to 26 kg/mm2, which is nearly equal to the shearing strength of the tungsten coating itself of 24 kg/mm2; fracture propagated within the coating itself. In the case of the copper substrate the critical shearing stress of adhesion was from 9 to 13 kg/mm2 which is much weaker than the shearing strength of copper, 28 kg/mm2; the fracture propagated along the boundary between the coating and substrate. Theoretical considerations attempt to explain the mechanisms of formation of the structures and the adhesion properties. It is concluded that the high adhesion strengths obtained by this method are attributable to the characteristics of the particles sprayed by wire explosion, i.e., the small size (average 5 μ), the high temperature (near the boiling point of materials), the high impinging velocity (500–600 m/sec), and furthermore, the uniformity of the size, velocity and temperature of the sprayed particles.

Effect of alloying elements on the strength of grain boundaries in aluminum alloys at high temperatures

1. A method has been developed for obtaining bicrystal specimens for stress-rupture testing. 2. It has been found that zinc and manganese segregate at the grain boundaries of solid solution of aluminum -copper-zinc and aluminum-copper-manganese. 3. It has been found that zinc lowers the high temperature strength of the grain boundaries in aluminum-copper alloys, while manganese increases it.