Composition Of Solid Solution Research Articles

Quantum insulator in a semimetal channel on a single type II broken-gap heterointerface in high magnetic fields

The peculiarity of planar quantum magnetotransport in the type II broken-gap p-GaInAsSb/p-InAs heterostructures at high magnetic fields has been investigated. The structure of the hybridized energy spectrum of a two-dimensional semimetal channel at a single type II broken-gap heterointerface was considered in dependence on the composition of the quaternary solid solution. A transition from a conducting state to a dielectric state (quantum insulator) for a 2D-semimetal channel at the heteroboundary was observed in quantizing magnetic fields under the condition of simultaneous filling of the first Landau levels for 2D-electron and interface hole states.

Morphology of ettringite crystal of sulfoferrite clinker

This paper deals with the composition and properties of solid solution of calcium sulfoferrite. It was studied an influence of calcium s sulfoferrite on structure and properties cement phases. Study of the hydration processes of the calcium sulfoferrite mineral are observed only short prismatic crystals. Prismatic crystals of ferruginous ettringite are always formed from sulfoferrite mineral of any fraction. it was found that the smaller the initial hydrating grains of minerals, the faster they are hydrated. Analyse polyfractional compound hydration showed that fine fractions provide formation of crystallization centres, and particles less than 45 microns, with constant interaction with the liquid phase, cause a gradual growth of crystals. Expansion of hydrated minerals of certain fractions was analysed to check the dependence of the expansion on the morphology of ettringite crystal hydrates. During the hardening of the samples, expansion was observed along with a drop in strength.

The impact of solid solution composition on kinetics and mechanism of [2 + 2] photodimerization of cinnamic acid derivatives

The effect of the solid solution composition on the kinetics of solid-state [2 + 2] photocycloadditions was evaluated via a combination of single crystal XRD, FTIR, Raman spectroscopy, and principal component analysis (PCA).

Влияние состава зародышевого слоя AlGaAs на формирование антифазных доменов в структурах (Al)GaAs, выращенных газофазной эпитаксией на подложках Ge/Si(100)

GaAs-based heterostructures grown by metalorganic vapor-phase epitaxy on virtual Ge/Si substrates using an AlxGa1-xAs seed layer with different aluminum content x in the solid solution are investigated. The effect of solid solution composition on the density and size of antiphase domains emerging on the sample surface and on the optical properties of the GaAs layer is shown. Si(100) substrates with a small unintentional miscut of 0.7° to [110] were used for growth.

Experiment and Calculation of Solid Liquid Phase Equilibria in the Ternary System KCl−KBr−H2O at T = 273 K

In this work, the solid-liquid phase equilibrium in the ternary system KCl−KBr−H2O at T = 273 K has been investigated by using the isothermal dissolution equilibrium method. Based on determined solubility data of saturated liquid phase and corresponding humid residue composition, the experimental phase diagram has been constructed. The result shows that the type of the system is classified as completely solid solution type due to the existence of solid solution K(Cl, Br). The phase diagram of the ternary system KCl−KBr−H2O at 273 K is divided into an unsaturated liquid phase filed and one solid crystalline phase region corresponding to K(Cl, Br) by an univariant solubility curve on which there is without any invariant point. The function which described the relationship between the composition of solid solution and the solubility of two salts in saturated liquid phase was constructed by multiple regression. The Pitzer equation has been selected to calculate the solubility data in the ternary system KCl−KBr−H2O at T = 273 K. The solubility modelling approach agrees with experimental solubility data.

SYSTEM Ag2S – SnS2 – P2S5

The quasiternary system Ag2S – SnS2 – P2S5 is characterized by quasi-binary sections between the binary and ternary phases. The existence of solid solutions Ag7+xP1-xSnxS6 (x =0÷ 0,31) and Ag8-xSn1-xPxS6 (x = 0÷0,21) was established on the quasi-binary section Ag7PS6 – Ag8SnS6. Replacement of P atoms by a mixture of [Ag + Sn] atoms in α-solid solution leads to an increase in the lattice parameters. The replacement of Sn atoms by P atoms in the β-solid solution is accompanied by a decrease in the lattice parameters. Moreover, the character is not linear, but is described by a positive deviation from Vegard’s rule. The crystal structure of two phases Ag7.31P0.69Sn0.31S6 ( а = 10.526(1) Å, SG (No 198) P213) та Ag7.8Sn0.8P0.2S6 (а = 15.205(3) Å, b = 7.527(1) Å, c = 10.663(2) Å; SG (No 33) Pna21) which are the final compositions of solid solutions. The tetra phase Ag7.31P0.69Sn0.31S6 is formed by replacing P atoms with Sn atoms. As a result, we obtain a defective, relative to the position of the atoms P, position 4a, which is inhabited by a mixture of atoms [Ag + Sn]. The coordination environment of cations is represented by tetrahedra, monohedra and dumbbells: Ag1 has a coordinating environment of sulfur atoms in the form of a dumbbellhas [S3-Ag1-S1], Ag2 is centered in the monohedron of the triangle [2S4- Ag2-S3] ; Ag3 is coordinated into a tetrahedron [Ag3S1S2S3S4], the atoms [Ag / Sn + P] have a tetrahedral environment of sulfur atoms: {[Ag/Sn+P]S23S4}. The tetra phase Ag7.8Sn0.8P0.2S6 is formed by replacing Sn atoms with P. atoms. As a result, we obtain position 4a, in which a mixture of atoms [0.8Sn + 0.2P] is localized. The coordination environment of cations is represented by tetrahedra, monohedra and dumbbells: Ag1 has a coordination environment of four sulfur atoms [Ag1S2S4S5S6], Ag2 is centered in a tetrahedron [Ag2S1S3S5S6]; Ag3 is coordinated in a tetrahedron [Ag3S1S2S5S6], Ag4 – in a monohedron [Ag4S1S4S6], Ag5 – in a monohedron [Ag5S1S2S5], Ag6 has a tetrahedral environment of sulfur atoms [Ag6S3S4S5S6]], Ag7 is coordinated in the center of the monohedron [Ag7S3S3S6], Ag8 forms a dumbbell shape with Sulfur atoms [S3-Ag8-S5]. [Sn + P] atoms have a tetrahedral environment of Sulfur atoms {[Sn+P]S1S2S3S4}.

Adjustable photoluminescence of Bi3+ and Eu3+ in solid solution constructed by isostructural end components through composition and excitation-driven strategy

• From orange red to blue in one phosphor via excitation-driven strategy. • The luminescence color of Bi 3+ was fine-tuned by solid solution composition. • Bi 3+ ions are used as doping ions, which can be carried out in air. • Solid solution constructed by isostructural end components. Most lanthanide doped phosphors need to be prepared in a reducing atmosphere, such as phosphors doped by Eu 2+ and Ce 3+ ions with d-f transition. In contrast, the doping ion Bi 3+ selected in this paper has more advantages. Moreover, the 6S electrons of bare bismuth are very sensitive to the surrounding coordination field environment, which makes it highly tunable. A new type of solid solution Sr 3−x Gd x AlO 4+x F 1−x designed by the isostructural end components Sr 3 AlO 4 F and GdSr 2 AlO 5 well promotes the luminescence of Bi 3+ ion. By adjusting the concentration of Bi 3+ /Eu 3+ , the phosphor can be tuned from blue to red, which is due to the energy transfer caused by dipole–dipole interaction between Bi 3+ and Eu 3+ . Surprisingly, by means of excitation-driven, the emission peak position of Bi 3+ ions can also be moved from ~425 nm to ~437 nm, and red shift occurs, so as to realize the tuning of the fluorescence from orange red to blue. We speculate that this is induced by the presence of multiple emission centers of Bi 3+ , and different absorption strength of Bi 3+ and Eu 3+ . In addition, the thermal response of Bi 3+ and Eu 3+ ions to temperature is different. They are thermally quenched by energy level cross relaxation (ELCR) and multi-phonon deexcitation (MPD), respectively. The maximum relative sensitivity of optical thermometry based on fluorescence intensity ratio (FIR) is approximately 1.17 %K −1 at 323 K, which is higher than that of previously reported Bi 3+ and Eu 3+ co-doped phosphors. At 523 K, we also obtained a high absolute sensitivity of 0.0064 K −1 . Consequently, the solid solution phosphor prepared by us has a far-reaching application prospect in the field of temperature monitoring.

Nepheline solid solution compositions: stoichiometry revisited, reviewed, clarified and rationalised

AbstractMolecular formulae used to recalculate nepheline analyses generally have different numbers of oxygens (e.g. NaAlSiO4(Ne), KAlSiO4,(Ks), CaAl2Si2O8(An) and SiO2(Q)). A 32 oxygen cell has 16 T cations and 8 cavity sites, but ideal nepheline stoichiometry is not necessarily followed. Ca end-member □CaCaAl2Si2O4(CaNe) and excess silica end-member □SiSi2O4(Q’) calculation requires inclusion of both vacancy species as cavity cation values. Q’ parameter calculations can involve different assumptions and four parameters are described: Qxs; QSi; Q(Si–Al); and Qcavity; these should have closely similar values for high-quality, stoichiometric analyses.Representative published compositions are recalculated to assess whether authors followed ideal nepheline stoichiometry. Phenocrysts from peralkaline rocks and nephelinites typically exhibit Al deficiencies reflected in negative Δ(Al – cavity cation) parameters (ΔAlcc), negative ‘normative’ corundum (Al2O3,Cn), and anomalously low or negative Qxsparameters; for such rock types Q(Si–Al)provides a better estimate of excess silica contents. A ΔT-site (cation charge) parameter (ΔTcharge), is closely coupled to ΔAlccand end-member NaAlSiO4has a ΔAlcc/ΔTchargeratio of 1.4296; the derivation of this value is controlled by strict stuffed-tridymite, unit-cell constraints. Natural nephelines all contain excess silica with a mean ΔAlcc/ΔTchargeof ~1.134 reflecting their Si/Al ratio being > 1.Nepheline analyses with relatively low Al and Si and high Na (also Ca) contents are common; this might reflect the presence of small amounts (up to ~5%) of cancrinite as an alteration phase or perhaps even in solid solution. The compositions of alteration lamellae of Ca-rich cancrinite in altered nepheline phenocrysts in phonolites from the Marangudzi alkaline complex, Zimbabwe, are used to define diagnostic parameters for recognising such non-stoichiometry. These alteration lamellae formed hydrothermally from Ca-rich and K-poor fluids.An EXCEL file is provided to help researchers to standardise calculation of nepheline end-member molecular proportions.

Theoretical and experimental investigation of the W-Al-B and Mo-Al-B systems to approach bulk WAlB synthesis

MAB phases are a family of ternary transition metal borides with a layered crystal structure, that provides them with properties likely to be suitable for applications within extreme environments. Here, we report a computational and experimental examination of the W-Al-B system compared to the isostructural Mo-Al-B system. Utilising DFT calculations, WAlB and MoAlB were found to be thermodynamically favourable compared to their most stable competing phases, with respective total energy differences of -0.15 eV and -0.28 eV at 0 K. Partial substitution of W on the Mo-site of MoAlB was observed for certain solid solution compositions. The experimental results indicate that synthesis of (Mo,W)AlB compounds is driven by in-situ formation of metal boride solid solutions, (Mo,W)B, which further react with Al, Mo-Al, W-Al or (Mo,W)-Al compounds to obtain the MAB phase structure. Finally, reactive hot-pressing was shown to be a promising avenue for the production of dense engineering (Mo,W)AlB-containing components.

On the Microstructure and Properties of Nb-18Si-6Mo-5Al-5Cr-2.5W-1Hf Nb-Silicide Based Alloys with Ge, Sn and Ti Additions (at.%).

We studied the microstructures and isothermal oxidation of the Nb-silicide-based alloys Nb-11.5Ti-18Si-5Mo-2W-4.9Sn-4.6Ge-4.5Cr-4.7Al-1Hf (JZ4) and Nb-21Ti-18Si-6.7Mo-1.2W-4.4Sn-4.2Ge-4Cr-3.7Al-0.8Hf (JZ5), calculated their average creep rate for the creep goal conditions of T = 1200 °C and σ = 170 MPa, and compared properties of the two alloys with those of other refractory metal (RM) complex concentrated alloys (RCCAs). Both alloys had a density less than 7.3 g/cm3 and lower than the density of multiphase bcc solid solution + M5Si3 silicide RCCAs. There was macrosegregation of Si in both alloys, which had the same phases in their as-cast microstructures, namely βNb5Si3, αNb5Si3, A15-Nb3X (X = Al, Ge, Si, Sn), TM5Sn2X (X = Al, Ge, Si), C14-Cr2Nb, but no solid solution. After heat treatment at 1500 °C for 100 h, a low volume fraction of a W-rich (Nb, W)ss solid solution was observed in both alloys together with βNb5Si3, αNb5Si3 and A15-Nb3X but not the TM5Sn2X, whereas the Laves phase was observed only in JZ4. At 800 °C, both alloys did not pest, and there was no spallation of their scales at 1200 °C. At both temperatures, both alloys followed parabolic oxidation kinetics and their weight changes were lower than those of Ti-rich Nb-silicide-based alloys. The oxidation of both alloys was superior to that of other RCCAs studied to date. For each alloy the Si macrosegregation, volume fraction of solid solution, chemical composition of solid solution and Nb5Si3, and weight changes in isothermal oxidation at 800 and 1200 °C that were calculated using the alloy design methodology NICE agreed well with the experimental results.

Phase Composition and Residual Stresses in the Surface Layers of VNS9-Sh TRIP Steel

The phase composition of thin-sheet (0.3 mm thick) austenitic–martensitic VNS9-Sh TRIP steel is studied by X-ray diffraction, and the residual stresses in the steel are determined. This cold-rolled steel is a gradient material with a high content of strain-induced martensite in the near-surface layers. The austenite content in the surface layer is shown to increase from 47% (as-delivered state) to 85% after removing a 10‑μm-thick surface layer. The positive volume effect of the martensitic transformation during cold rolling leads to the relaxation of high tensile stresses up to 850 MPa in the martensite phase and to the formation of compressive stresses up to 950 MPa in austenite in the surface layer. The removal of a 10-μm-thick surface layer brings about a substantial change in the stressed state; in this case, residual tensile stresses prevail in both the phases: 400–800 MPa in martensite and 70–280 MPa in austenite. A technique is proposed for estimating the residual stresses via measuring the lattice parameters for various reflections; it makes it possible to separate the contributions of residual stresses and the solid solution composition with allowance for the elastic anisotropy of the crystal lattice.

Centrosymmetric and acentric whitlockite-type phosphates and vanadates among Ca3(VO4)2-Ca3(PO4)2-Y2O3 compositions

Identifications and studies of whitlockite-type phases for the first time are fulfilled in the cation-anion mixed phosphate-vanadate ferroelectric systems Ca10.5(V1-x P x O4)7, Ca9Y(V1-x O4)7, Ca10.5-1.5x Y x (VO4)7 and Ca10.5-1.5x Y x (PO4)7. These systems are the sections of a more extensive multi-component system Ca3(VO4)2 - Ca3(PO4)2 - Y2O3, but are all built on the basis of well-known individual compounds of the type of mineral whitlockite. The solid solutions formed between them are also of ferroelectric whitlockite-type, but some compositions are not ferroelectric, and according to the nonlinear optical phase analysis possess centrosymmetric structure. Ferroelectric phase transitions were detected in the region of 1000–1300 K by the method of dielectric spectroscopy. A precision X-ray study of some compositions of solid solutions using synchrotron radiation revealed a significant deviation in the cationic-anionic arrangement from being completely disordered. Partial ordering of structural tetrahedral groups of PO4 3- and VO4 3- determines a significant increase in nonlinear optical activity in the mixed anions whitlockite-type compounds.

On the Microstructure and Properties of Nb-12Ti-18Si-6Ta-5Al-5Cr-2.5W-1Hf (at.%) Silicide-Based Alloys with Ge and Sn Additions.

The microstructures and properties of the alloys JZ3 (Nb-12.4Ti-17.7Si-6Ta-2.7W-3.7Sn-4.8Ge-1Hf-4.7Al-5.2Cr) and JZ3+(Nb-12.4Ti-19.7Si-5.7Ta-2.3W-5.7Sn-4.9Ge-0.8Hf-4.6Al-5.2Cr) were studied. The densities of both alloys were lower than the densities of Ni-based superalloys and many of the refractory metal complex concentrated alloys (RCCAs) studied to date. Both alloys had Si macrosegregation and the same phases in their as cast and heat treated microstructures, namely βNb5Si3, αNb5Si3, A15-Nb3X (X = Al, Ge, Si, Sn), C14-Cr2Nb and solid solution. W-rich solid solutions were stable in both alloys. At 800 °C only the alloy JZ3 did not show pest oxidation, and at 1200 °C a thin and well adhering scale formed only on JZ3+. The alloy JZ3+ followed parabolic oxidation with rate constant one order of magnitude higher than the single crystal Ni-superalloy CMSX-4 for the first 14 h of oxidation. The oxidation of both alloys was superior to that of RCCAs. Both alloys were predicted to have better creep at the creep goal condition compared with the superalloy CMSX-4. Calculated Si macrosegregation, solid solution volume fractions, chemical compositions of solid solution and Nb5Si3, weight changes in isothermal oxidation at 800 and 1200 °C using the alloy design methodology NICE agreed well with the experimental results.

Matched characterization of super-multiperiod superlattices

Heterostructures with multiple strongly coupled quantum wells, such as super-multiperiod (SMP) superlattices (SLs), are promising semiconductor devices, which may contain hundreds or even thousands of layers with 100 or more periods synthesized by molecular beam epitaxy (MBE) to high structural perfection. The proposed characterization method employs matched application of high-resolution x-ray diffractometry (XRD), reflectometry (XRR), and, for the first time, the deep XRR (DXRR) allows the study of SMP structures, as well as high-accuracy determination of the thicknesses of layers, roughness/diffuseness of boundaries using the rigorous scattering theory, and composition of solid solutions. Combining these methods with scanning transmission electron microscopy (STEM) enables characterization of SMP SLs and independent determination of these same parameters. The differences between the expected and obtained layer thicknesses by XRD and XRR were 1%–3% for AlGaAs/GaAs structures. The samples were characterized by sharp interfaces with the root-mean-square width of the transition layers of the order of a few Å, which is consistent with the XRR/DXRR and STEM analysis. Based on the data obtained for the thicknesses of layers, the composition of Al0.3Ga0.7As has been accurately determined by the x-ray methods. These results may be considered as the first step in the analysis of MBE-grown SMP structures with a number of periods up to 1000.

High-Throughput and Systematic Study of Phase Transformations and Metastability Using Dual-Anneal Diffusion Multiples

This article highlights the capabilities of dual-anneal diffusion multiples (DADMs) in performing high-throughput and systematic studies of phase transformations and metastability. DADMs create wide ranges of solid solution compositions through elemental interdiffusion during a first anneal at a high temperature. After quenching to ambient temperature, each diffusion multiple can be cut into several slices, and each slice is further annealed individually at a lower/second temperature. Phase transformations take place in the supersaturated regions of the solid solution compositions that are formed during the first anneal, leading to various precipitates due to different driving force, interfacial energy, and other factors as composition varies across the regions in the sample. By subjecting the sliced diffusion multiples individually to different anneal durations and different second anneal temperatures, very large datasets can be collected on phase transformation kinetics and evolution of precipitate morphology as a function of composition, time, and temperature. Metastable phases and their transitions to more stable phases have been systematically observed in the Fe-Cr-Mo ternary system across a wide range of composition, temperature, and anneal time, thus providing a large amount of information on metastability of the phases. The solvi of the metastable and stable phases can be systematically collected for more reliable CALPHAD assessments of the Gibbs free energy of the metastable phases. By adjusting the interfacial energy value in simulations using models such as the Kampmann–Wagner Numerical (KWN) model and matching the simulated precipitate sizes at different compositions with experimentally measured sizes of the corresponding compositions in a DADM, the interfacial energy value can be obtained. Opportunities and challenges in using DADMs to collect large datasets on precipitation kinetics and morphology will be explained to enable full utilization of the capabilities of DADMs in the future. This review not only presents experimental results collected to date, but also explains the vast more datasets that can be collected from DADMs in the future. An approach that iteratively and holistically integrates experimental results with model predictions is advocated as a very effective means to advance the understanding of various phase transformation mechanisms. In this way, the new mechanistic understanding can be integrated to more robust models to simulate the “abnormal” behaviors that are observed in DADMs, especially related to sequential precipitations of phases that are common in engineering alloys. Examples are also shown to illustrate the systematic nature of DADMs as a result of their continuously varying composition regions in catching unusual phenomena and emergent trends that are easily missed during studies using discrete compositions afforded by individual alloys.

The role of nickel addition on the CO2 chemisorption enhancement in Ni-containing Li2CuO2: Analysis of the cyclability and different CO2 partial pressure performance

This work analyzes the inclusion of nickel ions in lithium cuprate (Li2CuO2) as a solid solution or outside forming composites. All the compounds were obtained by solid-state reaction: pristine Li2CuO2, solid solutions (Li2Cu1-xNixO2, with x ≤ 0.10) and composites (Li2CuO2-LiNiO2, with x > 0.10). The materials were characterized by XRD, N2 adsorption-desorption, SEM and NMR of solids. The CO2 capture capacity of solid solutions and composite samples was evaluated, in comparison to the pristine lithium cuprate. At PCO2 = 1, the Li2Cu0.9Ni0.1O2 solid solution composition exhibits the best CO2 chemisorption at high temperature (700 °C), although all Ni-containing Li2CuO2 samples showed slower kinetics and lower temperature dependence than pristine lithium cuprate. It was attributed to structural and chemical variations on Li2CuO2 produced by the Ni ions. In fact, when the CO2 partial pressures were equal to 0.2 or 0.05, the nickel presence induced a stabilization during CO2 capture, averting temperature displacement maintained the highest chemisorption at 700 °C where the regeneration of the material is optimal. At PCO2 of 0.2, pristine Li2CuO2 shifted its highest capture from 700 to 650 °C, while Ni-containing samples preserved the best CO2 capture at 700 °C. Then, cyclic experiments were performed at 700 °C with PCO2 = 0.2 where the solid solution sample demonstrated a better stability than that observed on the pristine Li2CuO2 sample.

Structure refinement, mechanical properties and feasibility of deformation of hypereutectic Al–Fe–Zr and Al–Ni–Zr alloys subjected to ultrasonic melt processing

Hypereutectic Al–Fe and Al–Ni alloys offer a potentially attractive combination of properties, e.g. high-temperature strength and stability, high elastic modulus and low coefficient of thermal expansion. This potential, however, cannot be reached unless the structure of these alloys is refined so that their processing becomes possible. In this study, we for the first time apply ultrasonic melt processing for refining the structure of hypereutectic Al-4% Fe and Al-8% Ni alloys with 0.3 wt% Zr addition. Both primary Al3Fe and Al3Ni particles as well as aluminum/eutectic grains are significantly refined. It is suggested that cavitation-induced fragmentation of primary Al3Zr crystals plays a significant role in the nucleation of intermetallics as well as aluminum. Furthermore, the hardness and tensile properties of the alloys substantially increase after ultrasonic treatment due to the refined structure, which also contributes to the considerably enhanced ductility of the alloys. As a result, the fracture mode changes from brittle fracture to ductile fracture. The increase in ductility makes the alloys suitable for hot deformation, which is demonstrated by lab-scale hot rolling. In addition, precipitation hardening of the alloys can be achieved by high-temperature annealing at 450 °C due to retained Zr in the Al solid solution upon solidification. The results are supported by the analysis of the composition of a supersaturated solid solution of Zr in Al and scanning and transmission electron microscopy that confirms the precipitation of coherent Al3Zr nanoparticles. It is demonstrated that a combination of ultrasonic melt processing and alloying with Zr makes it feasible to develop new class of hypereutectic casting and wrought alloys based on the Al–Fe and Al–Ni systems.

Influence of interatomic interactions on the mechanical properties of face-centered cubic multicomponent Co–Ni–Cr–Mo alloys

The composition of a multicomponent solid solution has a significant influence on its mechanical and microstructural properties. Herein, the microstructures, phase stabilities, mechanical properties, and interatomic interactions of multicomponent Co–(5–55)Ni–19Cr–9Mo (mass%) alloys with varying Ni contents were comprehensively investigated. First-principles calculations were performed to predict the mechanical properties, electron distributions, atomic bonding states, and density of states of the alloy system. The local charge distribution revealed that the alloying elements exhibit stronger bonds with Co atoms than with Ni atoms, and the Ni–Ni bond is the weakest; accordingly, an increase in the Ni content generally diminishes the interatomic interactions in the studied alloy system. Meanwhile, significant augmentations in the strength and elastic modulus were observed at 45 mass% Ni. This was attributed to the additional interactions that are prevalent in 45 and 55 mass% Ni alloys that stem from the second-nearest Ni atoms with vacant 3d states and involve Co, Cr, and Mo atoms. Strengthening analyses indicated that the shear moduli predetermined the changes of yield strength with respect to the Ni contents. The stacking fault energies (SFEs) were calculated ab initio at 0 K and thermodynamically at 1500 K. A similar trend in the SFE variations was obtained under special consideration of the concentration dependence of the Co–Ni interaction, which indicated the significant influence of interatomic interactions even at elevated temperatures.

Dynamic Crystallization of a Haplogranitic Melt: Application to Pegmatites

AbstractBoth equilibrium and dynamic crystallization experiments have been performed on a hydrous haplogranitic melt at 200 MPa to model nucleation and growth mechanisms and simulate pegmatite textures. The equilibrium results provide a reference frame (phase assemblages and compositions, liquidus and solidus temperatures and dependence with the melt H2O concentration) to parametrize the kinetic experiments. The seven H2O-saturated dynamic crystallization experiments followed a specific time-temperature path. After a pre-conditioning step at 800°C, charges were cooled between 3·5 and 7°C/min to 700, 660 and 600°C corresponding to ΔT of 20, 60 and 120°C. Dwell times ranged from 42 up to 1440h. Variable mineral assemblages and textures, and two types of polymineralic assemblages were obtained depending on ΔT and t. For ΔT = 120°C, crystallization is sequential and includes graphic quartz–alkali-feldspar intergrowths characteristic of pegmatite textures. The crystallization sequence reflects nucleation and growth of kinetically-favoured metastable phases and solid solution compositions from the supercooled melt. Early alkali-feldspars are more K-rich than expected at equilibrium and late albites more Na-rich. The K-rich graphic texture progressively evolves to a Na-rich intergrowth texture. Melts also follow a progressive though limited sodic evolution with time. At the interface of growing alkali-feldspars, melts are enriched in SiO2 and depleted in Al2O3, Na2O and, to a lesser extent, K2O. H2O accumulates at the interface reaching concentration levels higher (by 1–2 wt %) than the saturation. Rejection of SiO2 and H2O at the interface controls the effective undercooling in the local melt and promotes rapid textural changes toward larger grain sizes at the front of graphic zones. Textural ripening takes place contemporaneously to sequential crystallization. Growth rates for quartz and alkali-feldspar are tightly grouped, between 7·3 x 10-11 and 1·6 x 10-12 m s-1. Textures from the dynamic crystallization experiments closely resemble natural pegmatites, but layered aplite units have not been reproduced. Our results confirm and strengthen the importance of liquidus undercooling to generate pegmatite textures.

Encapsulation of Phosphorescent Pt(II) Complexes in Zn-Based Metal-Organic Frameworks toward Oxygen-Sensing Porous Materials.

In this work, we synthesized two tailored phosphorescent Pt(II) complexes bearing a cyclometalating tridentate thiazole-based C^N*N pincer luminophore (L) and exchangeable chlorido ([PtCl(L)]) or cyanido ([PtCN(L)]) coligands. While both complexes showed photoluminescence from metal-perturbed ligand-centered triplet states (3MP-LC), [PtCN(L)] reached the highest phosphorescence quantum yields and displayed a significant sensitivity toward quenching by 3O2. We encapsulated them into two Zn-based metal-organic frameworks, namely, MOF-5 and ZIF-8. The incorporation of the organometallic compounds in the resulting composites [PtCl(L)]@ZIF-8, [PtCN(L)]@ZIF-8, [PtCl(L)]@MOF-5, and [PtCN(L)]@MOF-5 was verified by powder X-ray diffractometry, scanning electron microscopy, time-resolved photoluminescence spectroscopy and microscopy, as well as N2- and Ar-gas sorption studies. The amount of encapsulated complex was determined by graphite furnace atomic absorption spectroscopy, showing a maximum loading of 3.7 wt %. If compared with their solid state forms, the solid-solution composites showed prolonged 3O2-sensitive excited state lifetimes for the complexes at room temperature, reaching up to 18.4 μs under an Ar atmosphere, which is comparable with the behavior of the complex in liquid solutions or even frozen glassy matrices at 77 K.