Calculating surface tension isotherms and the adsorption of components in ternary Na-K-Cs alloys

The results from calculating the surface tension (ST) isotherms and adsorption coefficients for components (?? _i ^(N) ) of Na-K-Cs alloys obtained by means of graphic computations and using a semi-empirical formula are presented. Ternary alloys with compositions corresponding to sections of a concentration triangle directed toward vertices of sodium, potassium, and cesium are investigated. A comparison of the values for ST isotherms and adsorption (where i represents Na, Cs, and K), calculated using the above methods, demonstrates their satisfactory agreement among themselves and with the experimental data.     

Values of adsorption and surface concentrations of the components in Na-K-Cs alloys

The values of adsorption Γ _i ^(N) and surface concentration X _i ^ω of all the components in alloys of the Na-K-Cs system were determined. The adsorption of cesium Γ_Cs^(N) was found to be > 0, while that for sodium Γ_Na^(N) was < 0 in all ternary alloys. The adsorption of potassium was found to undergo inversion when passing from Γ_K^(N) > 0 in ternary alloys (the ratios being X _Na: X _Cs > 14.4 and X _Cs < 6.5 at %) to the negative value of adsorption Γ_K^(N) in the alloys with X _Na: X _Cs < 14.4 and any cesium concentrations. Using the Na-K-Cs system, it was demonstrated for the first time that conditions ΣΓ _i ^(N) = 0 and ΣX _i ^ω = 1 and are fulfilled in ternary alloys.     

深过冷Ag-Cu-Ge三元共晶合金的相组成与凝固特征

在Ag_38.5Cu_33.4Ge_28.1三元共晶合金的深过冷实验中，获得的最大过冷度为175 K(0.22T_E). XRD分析表明，不同过冷条件下其共晶组织均由(Ag),(Ge)和η(Cu₃Ge)三相组成. 在小过冷条件下，三个共晶相协同生长，凝固组织粗大.随着过冷度的增大，共晶组织明显细化，(Ge)相与其他两相分离，以初生相方式生长，而(Ag)相与η相始终呈二相层片共晶方式共生生长. 当过冷度超过80 K时，初生相(Ge)由小过冷时的块状转变为具有小面相特征的枝晶方式生长. 部分小面相(Ge)枝晶出现规则的花状，花瓣数介于5—8之间，并且过冷度越大(Ge)相越容易分瓣. 花状(Ge)枝晶的晶体表面为{111}晶面簇，择优生长方向为〈100〉晶向族. 关键词： 三元共晶 晶体形核 深过冷 快速凝固     

Formation mechanism of primary phases and eutectic structures within undercooled Pb-Sb-Sn ternary alloys

The solidification characteristics of three types of Pb-Sb-Sn ternary alloys with different primary phases were studied under substantial undercooling conditions. The experimental results show that primary (Pb) and SbSn phases grow in the dendritic mode, whereas primary (Sb) phase exhibits faceted growth in the form of polygonal blocks and long strips. (Pb) solid solution phase displays strong affinity with SbSn intermetallic compound so that they produce various morphologies of pseudobinary eutectics, but it can only grow in the divorced eutectic mode together with (Sb) phase. Although (Sb) solid solution phase and SbSn intermetallic compound may grow cooperatively within ternary eutectic microstructures, they seldom form pseudobinary eutectics independently. The (Pb)+(Sb)+SbSn ternary eutectic structure usually shows lamellar morphology, but appears as anomalous eutectic when its volume fraction becomes small. EDS analyses reveal that all of the three primary (Pb), (Sb) and SbSn phases exhibit conspicuous solute trapping effect during rapid solidification, which results in the remarkable extension of solute solubility. Supported by the National Natural Science Foundation of China (Grant Nos. 50121101 and 50395105)     

Densities and surface tensions of SexTe1−x melts

The densities and surface tensions of Se_xTe_1?x melts have been determined from the melting points up to about 700°C. For Te-rich alloys a non linear behaviour has been found for the temperature dependence connected with a change in the coordination number.     

Topological and thermodynamic investigations of ternary mixtures containing cyclic ether: Excess molar enthalpies

Excess molar enthalpies, H_ijk^E, of 1,3-dioxolane or 1,4-dioxane (i) + aniline (j) + benzene or toluene (k) ternary mixtures have been measured as a function of composition at 308.15 K. The H_ijk^E data have been fitted to Redlich-Kister equation to determine ternary adjustable parameters along with their standard deviations. It has been observed that H_ijk^E values predicted by Graph theory compare well with their corresponding experimental values. The observed data have been analyzed in terms of (i) Graph theory (which involves the topology of a molecule); (ii) Prigogine-Flory-Patterson; and (iii) Sanchez and Lacombe theories.     

Thermodynamic and kinetic aspects on the selective surface oxidation of binary, ternary and quarternary model alloys

Segregation and selective oxidation phenomena of minor alloying elements during annealing of steel sheets lead to the formation of bare spots after hot dip galvanizing. In order to understand the influence of common alloying elements on the surface chemistry after annealing, model alloys of binary (Fe-2Si, Fe-2Mn and Fe-0.8Cr), ternary (Fe-2Mn-2Si, Fe-2Mn-0.8Cr and Fe-2Si-0.8Cr) and quarternary (Fe-2Mn-2Si-0.8Cr) systems were investigated. The specimens were annealed for 60 s at 820 °C in N₂-5% H₂ gas atmospheres with different dew points −80 and −40 °C, respectively. Surface chemistry of the annealed specimens was obtained by using X-ray photoelectron spectroscopy (XPS). The field emission scanning electron microscopy (FE-SEM) was used to view surface morphology. At low dew point −80 °C, apart from the thermodynamical calculations such as solubility product of oxides and their critical solute concentrations, kinetics play a decisive role on the selective oxidation, i.e. oxygen competition. As expected, the amount of external selective oxidation of alloying elements are well pronounced at higher dew point −40 °C. An attempt has been made to explain the dominant process of Si and Mn on Cr-oxidation and segregation. It is observed that annealing of quarternary system at higher dew point shifts the Cr-oxidation from external to internal.     

Excess molar volumes and isentropic compressibilities of binary liquid mixtures containing n-alkanes at 298.15 K

Excess molar volumes (V ^E) and deviation in isentropic compressibilities (Δβ _s) have been investigated from the density ρ and speed of sound u measurements of six binary liquid mixtures containing n-alkanes over the entire range of composition at 298.15 K. Excess molar volume exhibits inversion in sign in one binary mixture, i.e., n-heptane + n-hexane. Remaining five binary mixtures, n-heptane + toluene, cyclohexane + n-heptane, cyclohexane + n-hexane, toluene + n-hexane and n-decane + n-hexane show negative excess molar volumes over the whole composition range. However, the large negative values of excess molar volume becomes domainant in toluene + n-hexane mixture. Deviation in isentropic compressibility is negative over the whole range of composition in the case of all the six binary mixtures. Existence of specific intermolecular interactions in the mixtures has been analyzed in terms of excess molar volume and deviation in isentropic compressibility.     

The Rh influence on the surface distribution of the ternary alloy Pt-Pd-Rh

Using the modified analytical embedded atom method (MAEAM) and combining with Monte Carlo computer simulations, the surface segregations of Pd-Rh and Pt-Pd-Rh have been simulated. The simulation results indicate that Pd enriched at both Pd-Rh and Pt-Pd-Rh (1 1 1) surface, but in the ternary ones, the surface Pd concentrations are influenced by bulk Rh compositions. Differences and similarities of the surface segregations between Pt-Pd, Pd-Rh and Pt-Pd-Rh have been discussed. Because of the lack of the experimental data, we finally compared present simulation results with available experiment data and theory calculation results of Au-Cu-Ni and Cu-Ag-Au. It is shown that the present results of simulations are in qualitative agreement with the experimentally observed trends, and it will be helpful for a better understanding of the segregation behaviors in Pt-Pd-Rh.     

Densities, excess molar volumes and partial molar volumes of the binary mixtures of acetic acid + alkanol (C1–C4) at 298.15 K

Densities (ρ) of the binary mixtures of acetic acid with methanol, ethanol, propan-1-ol, propan-2-ol, butan-1-ol and butan-2-ol have been measured at temperature 298.15 K and ambient pressure (815 hPa) as a function of composition using an Anton Paar model DMA 4500 oscillating densimeter. The excess molar volume (V_m^E), partial molar volume (V¯_i) and excess partial molar volumes (V¯_i^E) of the binary mixtures were calculated from the density data. The excess molar volumes were correlated with the Redlich−Kister equation. The excess molar volumes are negative for methanol, ethanol, propan-1-ol, propan-2-ol and butan-1-ol. They are positive for butan-2-ol and an inversion of sign in V_m^E is observed for butan-2-ol around 0.9 mol fraction of acetic acid.

The results obtained in this work were interpreted in terms of intermolecular interaction between like and unlike molecules, difference in size and shape of unlike molecules and the steric hindrance caused by increased methylation.     

Binary alloys of Ge and Te: order, voids, and the eutectic composition

The liquid and amorphous structures of Ge0.15Te0.85 and GeTe alloys are characterized using combined density functional/molecular dynamics simulations. Te is threefold coordinated, in contrast with predictions of the "8-N rule," and Ge atoms (fourfold coordinated) show octahedral and tetrahedral bonding angles. Cubic local environment occurs in both materials, and GeTe shows a pronounced alternation of atomic types. Tetrahedral Ge coordination is more common in the eutectic Ge0.15Te0.85, which comprises corner- and edge-sharing GeTe4 units surrounded by Te. There is no Te segregation, and the material resembles neither GeTe nor Te. The ubiquitous cavities (voids) have been overlooked in Ge0.15Te0.85, where they comprise over 25% of the volume.     

Electron Energy Loss Spectroscopy study of the near surface region of the ternary Co-Cr-Mo alloy

Nature of the characteristic electron energy losses in the second electron emission spectra from the ternary Co-Cr-Mo alloy surface are studied in the low energy range of the primary electron energy E₀. The main types of losses were found: surface and bulk plasmons and their hybrid modes, interband transitions and ionization losses. For Co, Cr, Mo and Co-Cr-Mo alloy the experimental values of the plasmon energy were established to be less than it was predicted by free-electron gas model. Excess of conductive electrons in the surface layers for Co, Cr and Mo was observed by dependence of the surface plasmon dispersion from E₀, while for Co-Cr-Mo alloy the situation is quit opposite. Such behavior is explained by the complex phase structure of the ternary alloy. The analysis of intensity lines of plasmons from E₀ showed deeply changed alloy profile. Ionization Spectroscopy was used for studying the alloy elements distributing on the depth. Mo atoms preferred segregation in the outermost layers of Co-Cr-Mo alloy and enrichment with Cr competitive atoms in underlayers is displayed.     

Thermal diffusivities and molar volumes of ternary Al20 AsxTe80−x alloy glasses: evidence of self-organization

Thermal diffusivities (α) and molar volumes (V_m) of bulk Al₂₀As_xTe_80−x alloy glasses in the composition range 0≤x≤35 are examined. The results reveal a broad maximum in alpha and a broad minimum in V_m in the 15<x<25 range. Earlier temperature modulated differential scanning calorimetric measurements on these glasses have revealed the non-reversing heat flow to show a global minimum (reversibility window) in the same composition range. Taken together these results suggest that present glasses in the 15<x<25 range are self-organized. The thermal diffusivity maximum observed near x=20 is consistent with a minimal scattering of thermal waves in the homogeneous and stress-free glass composition residing in the center of the self-organized phase.     

One and two mode behaviors of surface phonon-polaritons of ternary mixed crystal films

One and two mode behaviors of surface phonon-polaritons of ternary mixed crystal (TMC) films are studied in the framework of the modified random-element-isodisplacement model and the Born-Huang approximation, based on the Maxwell's equations with the usual boundary conditions. The numerical results for the frequencies and splitting energies of the surface phonon-polaritons as functions of the composition in several II-VI and III-V compound semiconductor ternary mixed crystal films are obtained. The “two-mode” and “one-mode” behaviors for different types of systems are clearly shown in the curves of the splitting energies of surface phonon-polaritons. The theoretical conclusion obtained is agreement with the reported experiment results for bulk TMC systems.     

Distribution of atoms in a ternary alloy with a free surface in the self-consistent field approximation

Analytical form for the functions describing atomic distribution of the components in the subsurface layer of a ternary alloy has been found in a closed form in the self-consistent field approximation, without taking correlation into account. The functions obtained allow one to construct concentration profiles of the components near the surface, to calculate the component surface concentration, and to investigate the dependence of the composition on the surface of the alloy crystal on temperature, and surface relaxation of coordination numbers and energies of the nearest neighbor interatomic interaction in an alloy. An analysis of the character of temperature dependencies of the composition on the surface has been performed for various alloys.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 8, pp. 47–52, August, 1982.     

Thermodynamics of mixtures containing alkoxyethanols. Part XXV. Densities, excess molar volumes and speeds of sound at 293.15, 298.15 and 303.15 K, and isothermal compressibilities at 298.15 K for 2-alkoxyethanol + 1-butanol systems

Densities, ρ, and speeds of sound, u, of systems formed by 2-methoxyethanol (2ME), 2-ethoxyethanol (2EE), 2-propoxyethanol (2PE), or 2-butoxyethanol (2BE) and 1-butanol have been measured at 293.15, 298.15 and 303.15 K and atmospheric pressure using a vibrating tube densimeter and sound analyser Anton Paar model DSA-5000. The ρ and u values were used to calculate excess molar volumes, V^E, at those temperatures and deviations from the ideal behaviour of the thermal expansion coefficient, Δ_P, or of the isentropic and isothermal compressibilities, Δκ_S and Δκ_T at 298.15 K. From the data, it is apparent that the interactional contribution to V^E is more important for systems with 2ME or 2EE, while structural effects are more relevant in the 2PE or 2BE mixtures, and that dipolar interactions decrease with the size of the 2-alkoxyethanol. Several methods are applied to predict speeds of sound: free length theory (FLT), collision factor theory (CFT), and Nomoto, Junjie and Van Dael equations. CFT and Nomoto's equation provide the better predictions. Finally, 1-butanol + 2-alkoxyethanol, or + 2-(2-alkoxyethoxy)ethanol mixtures have been studied using ERAS. Poorer results were obtained for systems including 2-(2-alkoxyethoxy)ethanols, which may be due to dipolar interactions and structural effects are more important in such solutions.     

An investigation of influencing of Sb and Bi contents on surface tensions associated with Pb-free Sn-Zn-Sb-Bi quaternary and sub-quaternary solder alloys

The surface tensions of ternary and quaternary systems of Sn-based Pb-free solder alloys have been calculated using geometric models, such as Muggianu, Kohler, Chou’s general solution model (GSM), Toop, Guggenheim, ideal Butler and Butler models. It is observed from the calculation carried out in the present work that Sb and Bi contents decrease the surface tension of the solder alloys Sn-Zn-Sb-Bi. It is inferred from the statistical analysis that the best agreement between the experimental results and the corresponding calculated values of the surface tensions is generally observed in GSM and Muggianu models among the geometric models. Whereas Muggianu model is the most appropriate. Relatively good agreements have been observed between models considered in this study and experimental data.     

Physical study of bismuth alloys containing Pb,Sn and Cd

For the purpose of studying some physical properties in addition to the mechanism of the melting phenomena, five bismuth alloys Bi_55.5Pb_44.5, Bi₅₀Pb₂₅Sn₂₅, Bi₅₀Pb₂₅Cd₂₅, Bi₅₀Pb₂₅Sn_18.75Cd_6.25 and Bi₅₀Pb₂₅Sn_6.25Cd_18.75 of melting points in the range from 338.5 to 396.5 K were prepared and studied by different techniques. The near-surface materials have been characterized by microhardness together with the wetting characteristics on CuZn₃₀ substrates as a function of time. The mechanism of melting from the point of view of the order of reaction (n) was explored by applying two different techniques, namely, differential thermal analysis and the electrical resistivity as a function of temperature.     

Densities, excess molar volumes, and viscosities of the binary and ternary mixtures of {diethylcarbonate (1) + p-chloroacetophenone (2) + 1-hexanol (3)} at 303.15 K for the liquid region and at ambient pressure

Densities ρ, dynamic viscosities η, of the ternary mixture (diethylcarbonate + p-chloroacetophenone + 1-hexanol) and the involved binary mixtures (diethylcarbonate + p-chloroacetophenone), (diethylcarbonate + 1-hexanol), and (p-chloroacetophenone + 1-hexanol) have been measured over the whole composition range at 303.15 K for the liquid region and at ambient pressure. The data obtained are used to calculate excess molar volumes V_m^E, excess partial molar volumes V¯_m,i^E, limiting excess partial molar volumes V¯_m,i^E,∞, and viscosity deviations Δη, of the binary and ternary mixtures. The data of excess molar volumes of the binary systems were fitted to the Redlich–Kister equation while for the ternary system the Cibulka equation was used. The McAllister's four body, and Kalidas and Laddha interaction models are used to correlate the kinematic viscosities of binary and ternary mixtures, respectively, to determine the fitting parameters and the standard deviations. The experimental data of the constitute binaries and ternary are analyzed to discuss the nature and strength of intermolecular interactions in these mixtures.