Binary Metal Systems Research Articles

Effect of the presence of lead on the biosorption of copper, cadmium and nickel by anaerobic biomass

Heavy metals are toxic pollutants released into the environment as a result of industrial, mining and agricultural activities. The biosorption of Pb, Cu, Cd, and Ni from single and binary metal systems were studied in equilibrium systems and in a flow-through column packed with a calcium-saturated anaerobic sludge biosorbent, respectively. The single-metal sorption uptake capacity of the biomass for Pb was slightly inhibited by the presence of Cu and Cd cations (by 6%) and by the presence of nickel (by 11%). The affinity order of anaerobic biomass for the four metals was established as: Pb > Cu > Ni > Cd. Factors such as hydration effects, hydrolysis effects and covalent binding of the metal ions may contribute to this result. By studying the breakthrough curves obtained from a fixed bed column fed with an equimolar mixture of Pb, Cd, Cu, and Ni, it was determined that lead was the last metal to break through the column at the 150 bed volume mark compared to 4, 15, 30 bed volume marks for Ni, Cd, and Cu, respectively.

Application of Wilson’s method to the calculation of thermodynamic properties of liquid ternary metallic systems from the data on boundary binary systems

The possibility of applying Wilson’s polynomial to the description of concentration dependences of thermodynamic functions in binary liquid metallic systems and to the calculation of thermodynamic properties of ternary systems from the data on boundary binary systems was considered.

Predicting the formation enthalpies of binary intermetallic compounds

A model is improved for predicting the formation enthalpies of binary transition metal systems and testified by comparing with the recently reported experimental data. The predictions by the improved model are in better agreement with 362 experimental data while comparing with Miedema’s theory. In addition, the predictive ability has also been addressed by comparing with ab initio calculations. A systematic analysis shows that the improved model is a reliable semi-quantitative method for predicting the formation enthalpy of intermetallic compounds with a reasonable statistical precise.

Stabilization of Nanoscale Quasi-Liquid Interfacial Films in Inorganic Materials: A Review and Critical Assessment

Recent observations of three classes of nanometer-thick, disordered, interfacial films in multicomponent inorganic materials are reviewed and critically assessed. The three classes of films are equilibrium-thickness intergranular films (IGFs) in ceramics, their free-surface counterparts, that is, surficial amorphous films (SAFs), and their metallic counterparts. Also briefly reviewed are several related wetting and adsorption phenomena in simpler systems, including premelting in unary systems, prewetting in binary liquids or vapor adsorption on inert walls, and frustrated-complete wetting. Analogous diffuse-interface and force-balance models are discussed with the goal of exploring a unifying thermodynamic framework. In general, the stability of these nanometer-thick interfacial films does not follow bulk phase diagrams. Stabilization of quasi-liquid interfacial films at subeutectic or undersaturation conditions in multicomponent materials can be understood from coupled interfacial premelting and prewetting transitions. More realistic models should include additional interfacial interactions, for example, dispersion and electrostatic forces, and consider the possibility for metastable equilibration. It is suggested that quasi-liquid grain boundary films in binary metallic systems can be used to validate a basic thermodynamic model. These nanoscale interfacial films are technologically important. For example, the short-circuit diffusion that occurs in interface-stabilized, subeutectic, quasi-liquid films explains the long-standing mystery of the solid-state activated sintering mechanism in ceramics, refractory metals, and ice.

Microbeam analysis of hydrogen near a crack tip in titanium

Microbeam transmission elastic recoil detection (ERD) was used to analyze microscopic hydrogen distributions near a crack tip in Ti foil loaded with an initial atomic hydrogen concentration of 3.0% relative to Ti. A 5.8MeV He ion beam focused down to the order of 10μm was scanned in a 500μm line perpendicular to the crack and approximately 20μm ahead of the crack tip. ERD line maps were made for a series of increasing stresses which were applied by uniaxial tension perpendicular to the crack. The crack opening displacement (COD) for each stress load was measured from an ion-beam-induced secondary electron emission (SEM) spectrograph of the crack opening. The technique was used to characterize the fracture mechanical properties of α-Ti hydride and demonstrates the use of microbeam analysis for the study of binary hydrogen metal systems.

A binomial truncation function proposed for the second-moment approximation oftight-binding potential and application in the ternary Ni–Hf–Ti system

We propose a two-parameter binomial truncation function for the second-momentapproximation of the tight-binding (TB-SMA) interatomic potential and illustrate indetail the procedure of constructing the potentials for binary and ternarytransition metal systems. For the ternary Ni–Hf–Ti system, the lattice constants,cohesion energies, elastic constants and bulk moduli of six binary compounds, i.e.L12 Ni3Hf,NiHf3,Ni3Ti,NiTi3,Hf3Ti and HfTi3, are firstly acquired by ab initio calculations and then employed to derive the binomial-truncatedTB-SMA Ni–Hf–Ti potential. Applying the ab initio derived Ni–Hf–Ti potential, the latticeconstants, cohesive energy, elastic constants and bulk moduli of another six binary compounds,i.e. D03 NiHf3, NiTi3 HfTi3, and B2 NiHf, NiTi, HfTi, and two ternary compounds,i.e. C1b NiHfTi, L21 Ni2HfTi, are calculated, respectively. It is found that, for the eight binary compounds studied, thecalculated lattice constants and cohesion energies are in excellent agreement with thosedirectly acquired from ab initio calculations and that the elastic constants and bulk modulicalculated from the potential are also qualitatively consistent with the results from abinitio calculations.

Comparison of Different Theoretical Models to Experimental Data on Viscosity of Binary Liquid Alloys

Six different theoretical equations are compared in the present paper with experimental data, measured for 28 binary liquid metallic systems. General conclusions are drawn on the ability of the different theoretical models to describe the concentration and temperature dependence of the viscosity of liquid alloys. A new equation is derived, being able to predict the viscosity in multicomponents alloy even if the viscosities of the pure components are not known.

Competitive Cu and Cd Sorption and Transport in Soils: A Combined Batch Kinetics, Column, and Sequential Extraction Study

The competitive effect influenced the transport behavior of Cu and Cd contrastingly in soils, as illustrated by the experimental findings obtained from column, batch kinetics, and sequential extraction tests. Of particular interest, Cd transport behavior changed from nonequilibrium in a single-metal system to equilibrium in a binary-metal system, whereas Cu exhibited a slightly greater degree of nonequilibrium transport under competition. The equilibrium time of specific sorption (approximately 7 days) was found to be much longer than that of nonspecific sorption (approximately 30 min). While there was a competitive effect on nonspecific sorption for both Cu and Cd, the majority of rate-limited specific sorption of Cd on oxide and organic matter fractions (contributing to approximately 20% of total sorption) was dramatically displaced by Cu. Such a strong suppression of specific sorption of Cd bythe presence of Cu resulted in a shorter equilibrium time of overall sorption, which probably accounts for its equilibrium transport. In contrast, the competitive effect on rate-limited sorption and transport behavior of Cu was less significant. This study demonstrated a correlation between the competitive effect of Cu and Cd on their nonspecific and specific sorption and the corresponding significance of rate-limited sorption and nonequilibrium transport behavior.

Thermal Modeling and Control in Production of Intermetallic Coatings From Layered Precursors

AbstractSuccessful fabrication of intermetallic coatings on surfaces of manufacturing interest involves regulation of the temperature/concentration dynamic distributions that develop in the molten layer during the thermal and reaction process. Modeling the spatio-temporal dynamics of this metallurgical process, however, requires partial differential equations that are cumbersome to solve on-line, as part of a real time reference model to the controller. To this end, we present a computationally parallel and meshless model (i.e., decoupled with the capability to be solved numerically in real time) to decipher the dynamics of the thermal coating process and to permit real time monitoring and control of the resulting coating microstructure. The analytical model is based on kinetic growth theories, lumped energy and mass balances, and convolution expressions of distributed temperature and concentration Green’s fields (accounting for the orientation of their gradient and decomposing heat and mass transfer across the coating from substrate conduction). The model is validated with nickel aluminide coatings processed on a robotic plasma arc laboratory station, through in-process infrared thermal sensing and off-line metallographic analysis. A Monte Carlo sample control scheme, that involves on-line parameter identification and model adaptation, is also developed using the model as an in-process observer for successful production of binary metal system coatings that exhibit the desired microstructure geometry and characteristics.

Synergistic Interactions of Binary Metal Toxicity to Indigenous Acidithiobacillus thiooxidans

Abstract-This study is a first attempt from a toxicological perspective to put forward, in general terms and through explanations, two-metal interactions of Cd(Ⅱ), Cu(Ⅱ), and Zn(Ⅱ) with indigenous Acidithiobacillus thiooxidans. According to the values of the critical concentration (CC), EC50, and slope factor B obtained in dose-response analysis, synergistic interactions rather than antagonism were found to have evolved for all the metallic cations as the combined effect of binary metal toxicity to indigenous A. thiooxidans. As the fixed-level factor metal increased, almost all the dose-response curves tended to shift toward the left (i.e. the highly toxic side). Compared with the single metal-bearing cultures, significant observed decreases in the critical concentration, resulting in a 100% toxic response for the binary metal systems, also strongly indicated synergistic interactions. In comparison, divalent zinc ion inevitably acted less synergistically than copper and cadmium ion. The toxicity ranking of three individual divalent cations in the binary metal systems with respect to indigenous A. thiooxidans is Cu＞Cd＞＞Zn. This assessment clearly indicates viable operation criteria for metal bioleaching for mine wastewater treatment, suggesting a feasible strategy for biotreatment using acidophilic Thiobacilli A. thiooxidans.

Modeling of the Equilibria of Yttrium(III) and Europium(III) Solvent Extraction from Nitric Acid with PC-88A

The equilibria of yttrium(III) and europium(III) (RE) extraction with PC-88A dissolved in Shellsol D70 from nitric acid solutions were studied under nonideal conditions in order to develop a chemically-based model enabling the engineering prediction of the equilibrium distribution ratios. The distribution of the extractant between the nitrate solution and the diluent was also examined. As a result, it was found that (i) the majority of PC-88A is dimerized in the organic phase, (ii) the cation exchange extraction is predominant in the low-acidity region, and (iii) solvation extraction becomes appreciable in the high-acidity region. By using a model that considers these two extraction equilibria together with the complexation of the RE with NO3−, the nonideality of the PC-88A dimer, and the competing extraction of HNO3, the extraction equilibrium constants and the coefficient for the effective concentration of the extractant were determined by the nonlinear least-squares method. The proposed model can reproduce the experimental data with good accuracy for single-metal systems over wide feed concentration ranges of RE up to 0.1 kmol·m−3, nitric acid (0.05 to 3 kmol·m−3), and the extractant (0.25 to 1 kmol·m−3). Its applicability to the prediction of the extraction from a binary metal system was also confirmed.

Size-dependent thermodynamic criterion for the thermal stability of binary immiscible metallic multilayers

With the aim of understanding the thermal stability of binary immiscible metallic multilayers, we propose a generally size-dependent thermodynamic criterion for determining the interface alloying in multilayers, with respect to the size-dependent interface energy of binary metal systems. Taking the copper/tungsten bilayer as an example, we obtain the interfacial alloying phase diagram based on the proposed thermodynamic model. Our theoretical predictions are consistent with experiments, implying that the size-dependent thermodynamic criterion of the thermal stability could be expected to be applicable to many multilayers.

Role of spatial valence charge density on the metastability of an immiscible binary metal system at equilibrium

In the equilibrium immiscible Ag--Ru system, the elastic constants and phonon spectra of the possible ${\mathrm{Ag}}_{3}\mathrm{Ru}$ and $\mathrm{Ag}{\mathrm{Ru}}_{3}$ in $\mathrm{D}{0}_{3},\mathrm{L}{1}_{2}$, and $\mathrm{D}{0}_{19}$ structures, respectively, are first obtained by the lattice dynamics calculation, which shows that only $\mathrm{L}{1}_{2}$ and $\mathrm{D}{0}_{19}\phantom{\rule{0.3em}{0ex}}\mathrm{Ag}{\mathrm{Ru}}_{3}$ phases can relatively be stable. The spatial valence charge density (SVCD) is then acquired by first principles calculation for all the studied structures. It turns out that the high SVCDs distribute mostly between the similar atoms in the relatively stable phases, while located mainly between the dissimilar atoms in all the unstable structures, indicating that the SVCD plays a decisive role in determining the metastability, i.e., the structural stability of the nonequilibrium phase, in an equilibrium immiscible binary metal system.

Comparison of the intergranular segregation for eight dilute binary metallic systems in the Σ 11′ {332} tilt grain boundary

Intergranular segregation is studied in the limit of infinitely diluted solution for eight dilute metallic systems made of four face centred cubic metals, one transition metal, nickel, and three noble metals, copper, silver and gold. The grain boundary (GB) chosen is the symmetrical tilt Σ = 11′ {332} 〈110〉 GB with its characteristic “zigzag” structural pattern as numerically calculated and experimentally observed by high resolution transmission electronic microscopy in nickel. The metallic interactions are modelled with Finnis-Sinclair like potentials. The atomic sites are characterised by a geometrical parameter defined with their exact Voronoi’ volumes and the tensor of the stresses locally exerted. The {332} GB presents the most diversity of sites in these respects. The segregation energies are computed and analysed versus the only two ‘driving forces’ which can play a role in metallic intergranular segregation, viz. the elastic size effect and the excess cohesion energy effect. The elastic size effect calculated by the method of virtual impurity represents the main segregation driving force in most cases of the considered systems. It is worth noting however that the excess cohesion energy effect is important for non hydrostatic or compressive sites. It can even be predominant, as in the case of Ni(Cu).

Biosorption of protons and heavy metals onto olive pomace: Modelling of competition effects

Heavy metal biosorption onto solid wastes from olive oil production plants, olive pomace, has been investigated. Acid–base properties of the active sites of olive pomace were determined by potentiometric titrations and represented by a continuous model accounting for two main kinds of active sites. Competition among protons and heavy metals in solution was considered by performing biosorption tests at different equilibrium pH with single (Cu and Cd) and binary metal systems (Cu–Cd). Both Langmuir extensions and non-ideal competitive adsorption models (NICA models) can be used to represent experimental data of Cu and Cd biosorption in single metal systems at different equilibrium pH. Nevertheless only NICA models, accounting for site heterogeneity and non-ideal adsorption of the different species simultaneously present in solution, can adequately simulate the competition among Cu and Cd in binary metal systems by using the parameters fitted to single system data.

Thermodynamics of interfacial energy in binary metallic systems: influence of adsorption on dihedral angles

The solid–liquid interfacial energy (or interfacial tension) was investigated by the lattice-liquid statistical calculation and by the Cahn–Hilliard theory of interface. Interfacial energies in binary metallic systems were estimated from a few bulk thermodynamic properties, i.e., melting temperature, entropy of fusion, and the critical temperature of the liquid phase. In eutectic systems, interfacial energy gradually increases with decreasing concentration of the solid species in the liquid. In monotectic systems, interfacial thickening occurs and interfacial energy is reduced around the liquid immiscibility gap. The results of calculation explain the experimental data of dihedral angles fairly well.

Thermodynamic and atomistic modeling of irradiation-induced amorphization in nanosized metal–metal multilayers

A brief summary is firstly presented concerning up-to-date experimental studies of the formation of amorphous alloys (metallic glasses) in binary metal systems by ion beam mixing of nanosized metal–metal multilayers. Secondly, under the framework of Miedema's theory, thermodynamic modeling of crystal-to-amorphous transition is described with special consideration of the effect of the excess interfacial free energy on the alloy phase formation. Thirdly, in some representative systems, glass-forming ranges are calculated directly from their realistic interatomic potentials by determining the critical solid solubilities of the systems by molecular dynamics simulations. Finally, a comparison between irradiation and thermally induced amorphization in the metal–metal multilayers is also discussed.

Proposed Definition of Microchemical Inhomogeneity and Application To Characterize Some Selected Miscible/Immiscible Binary Metal Systems

A new parameter is proposed to quantify the microchemical inhomogeneity (MCI) for a general multicomponent system and is applied to characterize some selected binary metal systems, i.e., the Ag−Ru, Ag−Co, Ni−Ru, and Ni−Hf systems, through molecular dynamics simulations. For the equilibrium immiscible Ag−Ru, Ag−Co, and Ni−Ru systems, ab initio calculations are performed to acquire some physical properties for fitting the respective n-body potentials. On the basis of the derived potentials, simulations reveal that in the highly immiscible Ag−Ru system, when the solute concentration is less than one of the critical values, i.e., either 6 atom % of Ru or 10 atom % of Ag, in the Ag-based and Ru-based solid solutions, respectively, the MCI is a small positive number and that when the solute concentration exceeds the critical values, i.e., falls in a composition range of 6−90 atom % of Ag, the MCI rises sharply to a large positive value ranging from 0.8 to 0.95, suggesting an incomplete-phase-separation tendency, which may result in forming a nanometer/subnanometer scaled structure. Similar simulations reveal that for the medium immiscible Ag−Co system, the MCI is about +0.7 within a composition range of 10−85 atom % of Ag and that for the Ni−Ru system, characterized by a nearly zero heat of formation, the MCI is nearly zero over the entire composition range, suggesting a possible metastable isomorphous phase diagram for the system, in which amorphous alloy, namely metallic glass, is hardly formed. In the contrast, for the miscible Ni−Hf system featuring a large negative heat of formation, the MCI is negative and is about −0.17 within a composition range of 25−80 atom % Ni, in which a crystalline solid solution prefers to turn into an amorphous state, corresponding almost exactly to the glass-forming range known from experiments as well as from theoretical prediction.

Glass-forming ability determined from inter-atomic potentials for some miscible/immiscible binary metal systems

The present study attempts to clarify one of the important issues in the field of metallic glasses (or amorphous alloys), i.e., to predict the glass-forming ability/range (GFA/GFR) of the binary metal systems. Firstly, a brief summary of the experimental observations indicates that in the miscible/immiscible systems, amorphous alloys can be formed in a broad composition range extending from central portion to nearby the edges of the two terminal solid solutions. Consequently, to predict RFA/GFR of a system becomes an issue of determining the critical solid solubility of the system, beyond which a solid solution would collapse into an energetically favored amorphous state. Secondly, the n-body potentials are derived by routine methods for the miscible Ni-Ta, Ni-Mo, and Ni-Ti systems, whereas for the immiscible Ag-Co and Cu-W systems having no any equilibrium alloy, the cross potentials are fitted to some physical properties acquired by first principles calculation for a few possible nonequilibrium alloys. Thirdly, applying the proven realistic potentials, molecular dynamics simulations with solid solution models reveal that the physical origin of crystal-to-amorphous transition is the lattice collapsing while solute atoms exceeding the critical solid solubility and that the GFRs of the systems are within the composition ranges bounded by the two determined critical solid solubilities. It turns out that the predictions are in good agreement with the experimental observations.

Bulk metallic glass formation in the binary Cu–Zr system

Using the Cu–Zr model system, we demonstrate that bulk amorphous alloys can be obtained by copper mold casting even in a binary metallic system. The narrow, off-eutectic, bulk-glass-forming range was found to require composition pinpointing to <1 at. %. A phase selection diagram is used to explain the success of our microstructure-based approach to pinpoint the best glass former in a given system. The implications of discovering simple binary bulk amorphous alloys are discussed, in terms of its impact on understanding the formation and physics of bulk metallic glasses.