Composition Dependence Research Articles

First principles calculation of composition dependence tracer and interdiffusion with phase change in γ/γ′ superalloy: A case study of Ir/Ir3Nb

In this work, the composition dependent tracer and interdiffusion coefficient with phase change in γ/γ′ Ir/Ir3Nb superalloy are studied by means of first-principles calculation together with nudged elastic band, and quasi−harmonic thermodynamics. The formulae scattered in the literature for composition dependence tracer diffusion coefficient are summarized and executed using first principles calculation. Each term in the newly derived formulae, such as energy barrier, jump frequency, defect concentration, correlation, solvent enhancement factor, effective escape frequency, etc. is meticulously calculated. We find the composition dependent tracer diffusion coefficient of Nb in L12 γ′-Ir3Nb phase is contributed mainly from the antisite bridge rather than five-frequency model proposed in FCC γ-Ir dilute solid solution. The faster diffuser is Nb in γ-Ir, while Ir in γ′-Ir3Nb. Based on the tracer diffusion coefficient, the interdiffusion coefficient is obtained using Darken-Manning equation. The composition profile and phase boundary movement of γ/γ′ Ir/Ir3Nb superalloy are evaluated through an analytical solution of Matano-Boltzmann equations. The calculated diffusion coefficients and composition profile are in good agreement with experiments. Our findings not only serve as a successful example for the quantitative calculation of composition dependent tracer diffusion coefficient, but also shed lights on the physics behind the diffusion in intermetallics.

Compositional and Temperature Dependence of Amorphous Polymer Networks Undergoing Mechanotropic Phase Transitions

Compositional and Temperature Dependence of Amorphous Polymer Networks Undergoing Mechanotropic Phase Transitions

Investigation of Indium doped Se-Te bulk chalcogenide glasses for electrical switching and phase changing applications

Recently, Metal-doped Se-Te chalcogenides have gained a lot of interest due to their unique capacity for electrical switching, which makes them desirable for electronic applications. This study examines the electrical switching characteristics of bulk Se86−xTe14Inx (0 ≤ x ≤ 6) amorphous alloys produced by the conventional melt-mix-quench process. The samples with an Indium atomic percentage between 2 to 6 exhibited a remarkable transition from a highly resistive to a low resistive state when subjected to an electric field with a current of 1 mA, displaying quick and reversible switching behaviour. The threshold voltage (Vth) significantly dropped from 410.6 V to 49.2 V with an increase in Indium concentration. Additionally, above the specific current threshold, these bulk glasses demonstrated memory-type switching, demonstrating their potential for data storage applications. To comprehend the trend of glass forming ability, thermal stability range and Hruby’s glass stability parameters, with their compositional dependency, Differential Scanning Calorimetry (DSC) was utilized. The sample Se80Te14In6 emerged to be the fastest phase-changing material, with a memory switching current threshold of Ith = 1.3 mA and a threshold voltage value of 49.2 V. To study the formation of crystallites in Se-Te-In alloy, X-ray diffraction patterns of pristine glass and the annealed sample were examined. Furthermore, temperature-dependent conductivity investigations showed a sharp rise in conductivity once the process crystallization begins (Tx), and also the threshold voltage (Vth) of the samples decreased linearly with rising temperature. Overall, this study provides valuable insights into the electrical switching behaviour and thermal properties of Se-Te-In chalcogenide glasses, enhancing their suitability in electronic devices.

BOWIE-ALIGN: A JWST comparative survey of aligned versus misaligned hot Jupiters to test the dependence of atmospheric composition on migration history

ABSTRACT A primary objective of exoplanet atmosphere characterization is to learn about planet formation and evolution, however, this is challenged by degeneracies. To determine whether differences in atmospheric composition can be reliably traced to differences in evolution, we are undertaking a transmission spectroscopy survey with JWST to compare the compositions of a sample of hot Jupiters that have different orbital alignments around F stars above the Kraft break. Under the assumption that aligned planets migrate through the inner disc, while misaligned planets migrate after disc dispersal, the act of migrating through the inner disc should cause a measurable difference in the C/O between aligned and misaligned planets. We expect the amplitude and sign of this difference to depend on the amount of planetesimal accretion and whether silicates accreted from the inner disc release their oxygen. Here, we identify all known exoplanets that are suitable for testing this hypothesis, describe our JWST survey, and use noise simulations and atmospheric retrievals to estimate our survey’s sensitivity. With the selected sample of four aligned and four misaligned hot Jupiters, we will be sensitive to the predicted differences in C/O between aligned and misaligned hot Jupiters for a wide range of model scenarios.

Reaction of size-selected iron-oxide cluster cations with methane: a model study of rapid methane loss in Mars' atmosphere.

We report gas-phase reactions of free iron-oxide clusters, FenOm+, and their Ar adducts with methane in the context of chemical processes in Mars' atmosphere. Methane activation was observed to produce FenOmCH2+/FenOmCD2+ and FenOmC+, where the reactivity exhibited size and composition dependence. For example, the rate coefficients of methane activation for Fe3O+ and Fe4O+ were estimated to be 1 × 10-13 and 3 × 10-13 cm3 s-1, respectively. Based on these reaction rate coefficients, the presence of iron-oxide clusters/particles with a density as low as 107 cm-3 in Mars' atmosphere would explain the rapid loss of methane observed recently by the Curiosity rover.

Study of the dependence of component composition - degree of wastewater purification by adsorbents based on plant raw materials to control the content of priority pollutants in water bodies

In conditions of intensive development of industrial and agricultural production, measures aimed at protecting the hydrosphere from harmful substances are becoming increasingly important every year. Water purification using the sorption method and water treatment is one of the most common technological processes. Almost unlimited reserves of sorbents of natural origin, their low cost, and fairly high adsorption and ion-exchange properties make their use advisable. Sorbents developed on the basis of available secondary plant raw materials show high efficiency and open up the possibility of their practical use in solving environmental problems. New sorbents based on plant raw materials have been developed, their structure and morphology have been studied in order to identify the absorption capacity and effectiveness of use as oil sorbents. Studies of the kinetics and dynamics sorption of oil pollutants confirm the effectiveness of mentioned sorbents and sorption purification technology can be used for environmental monitoring of water bodies.

Features of formation of titanium–nickel system coatings during annealing of titanium with nickel layer

The results of studies of the processes of formation of coatings based on titanium nickelides during diffusion annealing of titanium at a temperature of 750...850 °C with a chemical nickel coating are presented. The kinetics of transformation of a nickel layer on titanium into an intermetallic coating based on titanium nickelides is shown. The dependence of the chemical composition of the formed layers of nickelides on the temperature-time regimes of annealing has been established.

Approximation method for the potential composition of petroleum fractions

The paper gives a brief review of mathematical models of potential composition of oil fractions. The stages of obtaining approximating dependence of the fractional composition of oil are defined. A multicomponent mixture is represented as a discrete series of narrow hydrocarbon fractions. Each of them is characterized by its average boiling point. The results of approximation obtained for oil of different fields are given. The criterion for choosing dependence is the sum of squared deviations of factored values from experimental (reference) values. The following approximating dependencies of the curve of true boiling points for oil of different deposits are obtained. They are cubic parabola, power function, arctangence, exponentiation function, cubic parabola-arctangence. It is shown that the best results are obtained for combined ‘cubic parabolaarctangent’ model. In case of data deviation on oil fractional composition coming from chemical analytical laboratory coefficients are corrected in TBP approximation. Oil fractional composition awareness is important when choosing the direction of oil refining, in process and simulation modeling, when determining the top performance of processing units.

CO2 activation by copper oxide clusters: size, composition, and charge state dependence.

The interaction of CO2 with copper oxide clusters of different size, composition, and charge is investigated via infrared multiple-photon dissociation (IR-MPD) spectroscopy and density functional theory (DFT) calculations. Laser ablation of a copper target in the presence of an O2/He mixture leads to the preferred formation of oxygen-rich copper oxide cluster cations, CuxOy+ (y > x; x ≤ 8), while the anionic cluster distribution is dominated by stoichiometric (x = y) and oxygen-deficient (y < x; x ≤ 8) species. Subsequent reaction of the clusters with CO2 in a flow tube reactor results in the preferred formation of near-stoichiometric CuxOy(CO2)+/- complexes. IR-MPD spectroscopy of the formed complexes reveals the non-activated binding of CO2 to all cations while CO2 is activated by all anions. The great resemblance of spectra for all sizes investigated demonstrates that CO2 activation is largely independent of cluster size and Cu/O ratio but mainly determined by the cluster charge state. Comparison of the IR-MPD spectra with DFT calculations of the model systems Cu2O4(CO2)- and Cu3O4(CO2)- shows that CO2 activation exclusively results in the formation of a CO3 unit. Subsequent CO2 dissociation to CO appears to be unfavorable due to the instability of CO on the copper oxide clusters indicating that potential hydrogenation reactions will most likely proceed via formate or bicarbonate intermediates.

Composition, time, temperature, and annealing-process dependences of crystalline and amorphous phases in ductile semiconductors Ag2S1−xTex with x = 0.3–0.6

We investigate composition, time, temperature, and annealing-process dependences of crystalline and amorphous phases in ductile semiconductors Ag2S1−xTex with x = 0.3–0.6. We reveal that a metastable amorphous phase containing no secondary phases is obtainable at x = 0.6 even with furnace cooling and possesses ductility in the same manner as the end compound of Ag2S, while the high-temperature phase (HTP) of Ag2S precipitates in the amorphous phase at x = 0.3–0.5 by keeping the good ductility. During the crystallization process of the amorphous phase by annealing a sample at 373–503 K for 4–14 days and cooling it down slowly to room temperature, HTP of Ag2S disappears and the low-temperature phase (LTP) of Ag2S and the Ag5−dTe3 phase appear, while the amorphous phase remains. The ductility is observed for the samples containing the LTP of Ag2S but not for those containing the Ag5−dTe3 phase. Based on the obtained results, the possible phase diagram of Ag2S1−xTex with x = 0.3–0.6 is proposed, and the origin of the ductility in the LTP and HTP of Ag2S and amorphous phase is discussed. We believe that our study is helpful for properly predicting mechanical and transport properties of this material and developing this material as a component of bendable/wearable electronic devices for long-term use.

Compositional dependence of uniaxial zero thermal expansion and zero linear compressibility in metal-organic framework MIL-122 (Al, Ga, In).

The responses of MIL-122(Al, Ga, In) to pressure or temperature have been investigated. The findings suggest that the a-axis in the lattice exhibits minimal compressibility, particularly zero linear compressibility (ZLC) behavior observed in MIL-122(In), consistent with experimental reports. Additionally, as the radius of metal atoms increases, the compressibility of the b-axis and c-axis gradually strengthens. There is a notable compositional dependence on volume thermal expansion in MIL-122(Al, Ga, In), where an increase in the metal atom radius leads to gradual weakening of volume thermal expansion. In particular, MIL-122(In) demonstrates pronounced volume negative thermal expansion (NTE) behavior, with the a-axis displaying zero thermal expansion (ZTE) behavior and both the b-axis and c-axis exhibiting NTE behavior. The temperature-dependent relative change in the bulk modulus of MIL-122(Al, Ga, In) has also been explored, revealing abnormal thermal hardening specifically within MIL-122(Ga, In). We attribute these unique uniaxial ZTE and ZLC behaviors in MIL-122(In) to its distinctive wine-rack topology, anomalous phonons (negative Grüneisen parameters), and internal structural flexibility.

Clinopodium menthifolium subsp. menthifolium in the Central Balkan Peninsula - essential oil composition in relation to climatic conditions

The compositional dependency of the essential oil of Clinopodium menthifolium subsp. menthifolium (Lamiaceae) on ecological conditions has not yet been investigated. In pursuit of this objective, we assessed the quantity and quality of the essential oil in plants from 11 natural populations from the Central Balkans and one cultivated plant. In order to determine the correlations between essential oil variations and environmental conditions, each habitat was characterised by 36 climatic and 19 bioclimatic parameters. Despite inhabiting diverse climatic zones, altitudes, and biogeographical regions, no significant differences were observed in the yield and qualitative and quantitative composition of the essential oils among the analysed plants. All the samples exhibited essential oil yield ? 0.5%, V/w, with piperitone epoxide as the major compound. Among the identified compounds, only limonene and (E)-caryophyllene demonstrated dependence on bioclimatic parameters. The bioclimatic parameters which influence the presence of a larger number of compounds are annual temperature range and the precipitation of the wettest quarter. The consistent quantity and quality of the essential oils of C. menthifolium subsp. menthifolium indicate their probable adaptive significance and could serve as chemotaxonomic features of this taxon.

The effect of cation size on structure and properties of Ba-based tetragonal tungsten bronzes Ba4M2Nb10O30 (M = Na, K or Rb) and Ba4M2Nb8Ti2O30 (M = Ca or Sr).

The second largest family of oxide ferroelectrics, after perovskites, are the tetragonal tungsten bronzes (TTB) with the general formula A24A12C4B12B28O30. Cation disorder in TTBs is known to occur if the size difference between cations is small, but the impact of cation disorder on structure and properties has not yet been extensively addressed. In this study we investigate the effect of the size of the M cation, including cation disorder, on the crystal structure and dielectric properties in the two series Ba4M2Nb10O30 (BMN, A = Na, K and Rb) and Ba4M2Nb8Ti2O30 (BMNT, M = Ca, Sr). Dense and phase pure ceramics in the two series were prepared by a two-step solid state synthesis route. The crystal structures of the materials were characterized by powder X-ray diffraction combined with Rietveld refinement. A close to linear relation between the in-plane lattice parameter (a) and the size of the M-cation were observed. Ba4M2Nb8Ti2O30 was shown to possess cation disorder on the A-sites in line with previous work on Ba4M2Nb10O30. Thermodynamic calculations from density functional theory also indicated a drive for cation disorder in the three BMN compositions. Non-ambient temperature X-ray diffraction revealed contraction of the in-plane (a) and expansion of the out-of-plane (c) lattice parameters at the ferroelectric phase transition for Ba4M2Nb10O30. The ferroelectric transition temperature acquired by dielectric spectroscopy showed a systematically increasing TC with decreasing size of the M-cation within both compositional series studied. The compositional dependence of TC is discussed with respect to the size of the M-cation, cation disorder and the tetragonality, as well as the Ti-content. The relaxor to ferroelectric properties observed by polarization-electric field hysteresis loops are discussed in relation to the relative size of cations on the on A1 and A2 sites and the Ti-content.

Composition dependence of X-ray stability and degradation mechanisms at lead halide perovskite single crystal surfaces.

The multiple applications of lead halide perovskite materials and the extensive use of X-ray based techniques to characterize them highlight a need to understand their stability under X-ray irradiation. Here, we present a study where the X-ray stability of five different lead halide perovskite compositions (MAPbI3, MAPbCl3, MAPbBr3, FAPbBr3, CsPbBr3) was investigated using photoelectron spectroscopy. To exclude effects of thin film formation on the observed degradation behaviors, we studied clean surfaces of single crystals. Different X-ray resistance and degradation mechanisms were observed depending on the crystal composition. Overall, perovskites based on the MA+ cation were found to be less stable than those based on FA+ or Cs+. Metallic lead formed most easily in the chloride perovskite, followed by bromide, and only very little metallic lead formation was observed for MAPbI3. MAPbI3 showed one main degradation process, which was the radiolysis of MAI. Multiple simultaneous degradation processes were identified for the bromide compositions. These processes include ion migration towards the perovskite surface and the formation of volatile and solid products in addition to metallic lead. Lastly, CsBr formed as a solid degradation product on the surface of CsPbBr3.

High-throughput development of tough metallic glass films.

Fast development of metallic glass films with high toughness has been a long-sought goal of humankind in view of their superior properties and great potential for application in the field of soft electronics. However, until now, there has been no effective experimental strategy because of the lack of suitable and precise toughness measurement technology. In the present work, we introduced a feasible route for developing tough metallic glass films using combinatorial material library preparation and high-throughput toughness measurement via nanoindentation. Based on this route, tough metallic glass films for the quaternary Zr-Ti-Cu-Al system were successfully screened out. The corresponding electron work function map was detected to uncover the physical mechanism for the composition dependence of toughness. In addition, the preliminary assessments of the screened tough metallic glass films as strain-sensing materials were also conducted. Our current research not only provides a versatile toolbox for high-throughput development of tough metallic glass films, but also exemplifies their potential as strain-sensing materials.

FIRST-PRINCIPLES CALCULATION OF STRUCTURAL, ELECTRONIC, AND OPTICAL PROPERTIES OF InP1-XSbX USING WC-mBJ FOR NANOSCALE IR APPLICATIONS

The structural, electronic, and optical characteristics of cubic InP&lt;sub&gt;1-x&lt;/sub&gt;Sb&lt;sub&gt;x&lt;/sub&gt;(x &amp;#61; 0, 0.25, 0.50, 0.75, 1) ternary alloys were explored using the full-potential linearized augmented plane wave density functional theory approach. The total energy vs. volume optimization, lattice constants, and density of states were investigated for InP&lt;sub&gt;1-x&lt;/sub&gt;Sb&lt;sub&gt;x&lt;/sub&gt; alloys using exchange correlation function Wu-Cohen generalized gradient approximation (WC-GGA), available with the WIEN2k code. Band structure of the alloys was calculated using TB-mBJ functional to achieve a higher bandgap accuracy. The results of the mBJ experiment are in close agreement to those of the other experimental studies when compared to WC-GGA. Dielectric function and energy loss function were calculated in order to explore optical properties of the alloys. It was noticed that the estimated lattice parameters exhibit reduction when the Sb content is increased. Furthermore, the compositional dependency of the structural, electronic, and optical properties were also reported. For the InP&lt;sub&gt;1-x&lt;/sub&gt;Sb&lt;sub&gt;x&lt;/sub&gt; alloys, a band gap of less than 1.6 eVwere observed, making it suitable for usage in infrared optoelectronics devices.

Correlation of trace element composition of oils to the composition of the Earth’s crust as an indicator of the prospectivity of deep-seated deposits

The article considers correlations between the trace element composition of oils from the fields of Tatarstan and Western Siberia and the chemical composition of the Upper, Middle and the Lower crust and biota. The factual basis of the correlation calculations is a database compiled from a large number of analyzes by different authors. The results of the study quantitatively confirm the earlier conclusions about the polygenic source of trace elements in naphthides. The nature of the change in the correlation dependences of the trace element composition of naphthides is shown – from the initial organic matter to oils and natural bitumens. In certain oil and gas basins, a higher correlation of the trace element composition of oils with the compositions of the Lower or Middle crust, but not with the Upper one testifies for the involvement of deep-seated deposits in the oil generation processes, which increases the predictive estimates of the possibility of identifying mega-reservoirs of oil and gas at great depths.

Ecological preferences of the Swiss pine (Pinus cembra L.) forests in the Gorgany Nature Reserve

Swiss pine (Pinus cembra L.) is a montane Carpathian (Alpine-Carpathian) species. The modern distribution of the Swiss pine is disjunct, the two isolated areas are located in western and central Europe (Alps) and the middle and high mountains of the Carpathians. The largest areas of Swiss pine in Ukraine are preserved in the Gorgany region at the altitude of 1250‒1450 m above sea level, where it forms the upper forest line. In the Gorgany Nature Reserve, P. cembra grows in the altitude range from 1070 to 1475 m ASL. The lower boundary, in the form of individual trees, descends to 1000 m ASL, and the upper boundary rises to 1585 m ASL. To define the ecological preferences of the Swiss pine, a series of route surveys were conducted and research sites (permanent forest monitoring plots, stationary research profiles, and stationary areas for the counting of natural forest regeneration) were established. The study of the plant communities with P. cembra on the southwestern slopes of the Dzhurdzhi tract showed the dependence of the forest species composition on the altitude above sea level. The forest stands quantitative composition and productivity are also significantly influenced by slope exposure. The proportion of P. cembra in the forests on steep slopes (30‒55°) of west and north-west exposure is relatively high (from 17.1% to 49.0%). Under other conditions, the proportion of P. cembra in the stand composition gradually decreases. Swiss pine is almost completely absent on the slopes of eastern and northern exposures except for rare single trees in Pinus mugo Turra scrub on northern slopes. The forests with P. cembra are typical of sunny slopes where the available sum of active temperatures ranges between 1000° and 1400° and the average ambient temperatures from -12.2°С to +16°С. The optimal environmental conditions for the relict species P. cembra in the Dovbushanski Gorgany region are on the western slopes with a steepness of 17‒55° and southwestern and northwestern slopes with a steepness of 35°‒42°. In terms of soil fertility, oligotrophic edaphotopes with moderate moisture are optimal for the growth of Swiss pine.

DETERMINATION OF THE THERMODYNAMIC PARAMETERS OF α-IRON IN BINARY SYSTEMS Fe-Cr AND Fe-Ti

This article presents the results of calculations of the thermodynamic parameters of binary Fe-Cr and Fe-Ti systems based on their state diagrams using the Bjerrum-Guggenheim osmotic coefficient, for the region of iron crystallization from the iron activity of an ideal α-γ solution for the above systems. When calculating the lines of phase equilibrium in the Fe-Cr and Fe-Ti systems, it was established that the Bjerrum-Guggenheim coefficient can serve as an assessment parameter characterizing the role of exchange forces between atoms, and by its dimension (Фi&gt;&lt;1) one can qualitatively judge the nature of the intermolecular interactions in the system. The results of this work made it possible to correctly solve the direct Gibbs problem, namely, to obtain an analytical dependence of phase compositions on temperature at phase equilibria based on the laws of phase formation. It is shown that with the help of the Bjerrumm-Guggenheim osmotic coefficient (Fi), the real equilibrium in the system under study can be determined in detail and their correct analytical expression can be obtained. When calculating phase equilibrium lines in systems with different types of interaction between components, it was established that the Bjerrum-Guggenheim coefficient can serve as an assessment parameter characterizing the role of exchange forces between atoms. Keywords: thermodynamics; Bjerrum-Guggenheim coefficient; state diagram; osmotic coefficient; binary systems.

Insight into compositional dependence of thermophysical properties and structure of Al2O3-SiO2-CaF2-CaO-Li2O melts

Low-fluoride-lime Al2O3–SiO2–CaF2-based slag melts were designed for producing sulfur-bearing free-cutting steels by electroslag remelting. These newly designed slags must maintain the technological parameters, related to viscosity and crystallization characteristics. The structure, viscosity and crystallization of the slag with different CaO/SiO2 mass ratios and Li2O contents were studied. Raman spectroscopy shows that the silicate network is depolymerized and the aluminate network is polymerized as CaO/SiO2 mass ratio or Li2O content is increased. 27Al MAS-NMR spectra demonstrates the presence of small amounts of AlV and AlVI species in the melts with 0 mass% and 1.18 mass% Li2O, whereas Al is present exclusively in AlIV in other cases. The measured viscosity of the melts and the apparent activation energy of viscous flow decrease with increasing CaO/SiO2 mass ratio or Li2O content. Both the crystallization temperature and the crystallization ability of melts increase with increasing CaO/SiO2 mass ratio or Li2O content.