Al–Ga–Zn Phase Diagram. Calorimetric study of the isobaric invariants

The Al–Ga–Zn ternary phase diagram presents two isobaric invariant reactions: a eutectic at 23±1°C and a metatectic at 123±1°C [1–3]. Calorimetric measurements on the two isobaric invariant reactions have been carried out. First the Tammann method has enabled us to determine the composition of their limits on five isopletic cross sections. Then, the compositions of the invariant phases have been determined. This revised version was published online in July 2006 with corrections to the Cover Date.     

The Al-Zn-Ga Phase Diagram Part I

The Al-Zn-Ga ternary phase diagram was earlier established by thermodynamic modellization [1], but no experimental study appears to have been carried out on this system, except for measurements of mixing enthalpies in the liquid [2]. The present experimental study was carried out by thermal analysis and X-ray diffraction at various temperatures, using the isopletic cuts method. Four isopletic cuts were established and two others were partly studied in the Al-rich corner of the diagram. On these cuts, two isobaric ternary invariant reactions were determined: a eutectic reaction at 23±1°C, and a metatectic reaction at 123±1°C. Evidence was found for the existence of a retrograde miscibility of Ga in a solid solution α′_SS which protrudes into the ternary system starting from the Al-Zn binary up to a Ga concentration of about 30%^*. This revised version was published online in July 2006 with corrections to the Cover Date.     

Diphasic Domains Approach Method (DDAM)

If someone wants to plot an isobaric temperature-composition binary or an isobarothermal section of a ternary equilibria phase diagram he only needs to plot the limits of diphasic domains, it automatically gives the limits of the monophasic and triphasic fields. In such diagrams each diphasic domain is defined by two lines joining all the extremities of the tie-lines of the domain and limited by the first and the last one. These tie-lines are segments whose the extremities are in the plane of the diagram and can easily be determined by equilibria calculation codes. Then binary or ternary phase diagrams can be plotted only using conodes of the diphasic fields and the method used to determine the diphasic domains becomes the main point in binary and ternary phase diagrams plotting. A meshing of the surface of the diagram is certainly not the best way to obtain a rapid result. We propose an approach which consists to follow the curvature of the diphasic domains limits, the ‘Diphasic Domains Approach Method, DDAM’, which allows a rapid and robust determination of binary and ternary diagrams.     

Al-Zn-Sn Phase Diagram X-ray diffraction study at various temperatures

Further studies of the ternary phase diagram Al-Zn-Sn have been carried out by X-ray diffraction at various temperatures and by thermodilatometry in order to confirm our earlier experimental results which have been refuted by some recent work based on thermodynamic optimization. These new results, in particular the change with temperature of the crystallized fraction for Al-Zn-Sn mixtures containing up to 31.5 mass% of tin, confirm our previous results on the existence of a significant retrograde miscibility of tin in a solid solution α′ss (in the temperature range 286 to 335°C) which protrudes into the ternary system starting from the Al-Zn binary up to a tin concentration of about 50 mass%. This disagreement between theory and experiment highlights the difficulties of a thermodynamic optimization approach based on solid state solubilities in the binary systems and on ternary liquidus data which disregards the ternary interaction parameters in the solid state. Besides, this experimental study highlights the difficulties in understanding the phenomena which depend on phase stabilities. This revised version was published online in July 2006 with corrections to the Cover Date.     

Investigations into the formation and characterization of microemulsions. I. Phase diagrams of the ternary system water—sodium alkyl benzene sulfonate—hexanol and the quaternary system water—xylene—sodium alkyl benzene sulfonate—hexanol

The phase diagrams of the ternary system water—sodium alkylbenzene sulfonate (NaDBS)-hexanol and the quaternary system water—xylene—NADBS—hexanol have been established at three different temperatures, namely 25, 37, and 50°C. The different phases formed have been qualitatively examined using optical (phase contrast and polarizing) microscopy. The textures of the various liquid crystalline phases in the ternary system have been identified, by comparison with previous studies in the literature. Some of the liquid crystalline phases have been quantitatively assessed using low angle X-ray diffraction. The latter measurements were also used to determine the unit cell dimensions in the various phases studied. With the quaternary system, particular attention was paid to the transparent region which consisted of an L₂ (inverse micellar) phase extending into another transparent region which has a blue “tinge” in some cases, namely the microemulsion (M) region. The amount of water solubilized in the L₂ (reverse micelle) or M + L₂ phase was calculated from the phase diagrams. With the ternary system the results showed a maximum in moles of water solubilized per mole total surfactant (NaDBS + hexanol) at a concentration of 0.3 mole surfactant, at an optimum molar ratio of n-hexanol to NaDBS of 4.5:1. This maximum was about twice with the quaternary system, when compared with that of the ternary system, indicating the importance of the role of xylene in solubilization of water by the surfactants. The present investigation has also shown that the extent of the microemulsion region is significantly reduced by increases of temperature when the NaDBS is lower than 15 wt%.     

Cubic perovskite-related phases in the ternary SrO-CuO-Nb2O5 system

A careful phase analysis study of cubic perovskite-related phases in the ternary SrO-CuO-Nb₂O₅ system has been carried out via the synthesis and compositional analysis of a range of specimens within the ternary SrO-CuO-Nb₂O₅ system. Powder XRD in conjunction with electron probe microanalysis (EPMA) has been used to determine whether the synthesized specimens are single phase or not and to determine the compositions of the various reaction products. Three quite distinct such solid solution phases have been found and their quite distinct electrical and diffraction characteristics investigated.     

Al-Zn-Sn Phase Diagram Calorimetric Study of the Isobaric Invariants

A systematic study of Al-Zn-Sn ternary alloys by using a Tian-Calvet calorimeter with slow heating and cooling rate was carried out and supplemented by scanning electron microscopic observations. The results have shown that crystallization coupled with dissolution of tin into the α_ss′ ternary solid solution on heating is an endothermic process, while melting coupled with tin expulsion on cooling is an exothermic one. It seems that the thermal effects of phase transition are outweighed by much stronger ones due to a large composition change of the α_ss′ ternary phase. This revised version was published online in August 2006 with corrections to the Cover Date.     

T-x-y diagram of the Ce-Bi-Te system

The character of phase interaction in the Ce-Bi-Te ternary system has been investigated by differential thermal, X-ray diffraction, and microstructural analyses, as well as by the measurement of microhardness and density of alloys. Phase diagrams of eight polythermal and projection of the liquidus of the Ce-Bi-Te ternary system have been constructed. Original Russian Text ? S.G. Mamedova, F.M. Sadygov, T.M. Il’yasly, Z.I. Ismailov, 2009, published in Zhurnal Neorganicheskoi Khimii, 2009, Vol. 54, No. 2, pp. 364–367.     

Innocent or guilty? Redox activity in and magnetic and optical behaviour of dinuclear molydenum complexes

The phenomenon of ‘non-innocence’, first articulated by J?rgensen in 1966, is briefly reviewed. Spectroelectrochemical studies of a range of dinuclear complexes of the type [Mo(NO)Tp*Cl₂(bridge)] (bridge = dipyridyls) and [Mo(O)Tp*Cl₂(bridge)] (bridge = diphenolates) which are redox active, show that oxidised or reduced forms of these species exhibit ‘non-innocence’. The spectral behaviour is associated with metal-to-ligand or ligand-to-metal charge transfer phenomena, probably the first time that monodentate bridging ligands have been implicated in ‘non-innocent’ behaviour. These bridging ligands also determine the nature and extent of magnetic interaction between the unpaired spins in [Mo(NO)Tp*Cl₂(bridge)] and [Mo(O)Tp*Cl₂(bridge)], the dominant mechanism of spin-exchange relying on the extent of {ie291-01}-delocalisation within the bridging ligands. The unusual optical behaviour of these dinuclear complexes when oxidised (oxomolybdenum diphenolates) or reduced (nitrosyl molybdenum dipyridyls) has led to the exploration of electrochromism as a means to develop variable optical attenuators operating in the near-infrared region.     

Reactive diffusion in W–Mo–Si thin films

This study reports the phase formation in the ternary thin films system Mo–W–Si. The metallic films were deposited onto Si (100) substrate by sputtering. Two kinds of samples were prepared, either by sequential deposition or by co-deposition. The phase formation was investigated by In situ X-ray diffraction measurements from 300 to 900 °C. The influence of the sample preparation, namely sequential deposition and co-deposition, on the mechanism of phase formation has been evidenced.     

Fractionation of nano- and microparticles in a rotating conoidal coiled column

A method for the continuous-flow fractionation of particles in a transverse centrifugal field in a rotating conoidal coiled (RCC) column has been developed. A model of a planetary centrifuge with a conoidal drum of a special construction has been tested. The effects of the rotation and revolution speed of the conoidal RCC, as well as the direction and pumping rate of the mobile phase on the behavior of particles smaller than 1 μm have been studied. The conditions have been selected and optimized for the retention and elution of spherical particles of the ‘150 nm’, ‘400 nm’, and ‘900 nm’ standard samples of silica gel (Polyscience Inc.). The possibility of using RCC for the analysis and production of monodisperse standard particle samples has been demonstrated. In particular, the ‘900 nm’ particles have been separated from admixtures of small (100–200 nm) particles and nonspherical 1–2 μm particles present in the sample. The separated fractions have been characterized by electron microscopy.     

Modeling the state diagrams of ternary reciprocal systems

A model p-T diagram of a eutectic-type ternary reciprocal system is presented. An isobaric cross section in the form of a projection onto a concentration diagram is shown. Isothermic and polythermic cross sections of a eutectic-type ternary reciprocal fusibility diagram with swept faces of a tetrahedral prism are created. A projection of the diagram of a ternary reciprocal system with solid solutions based on initial components with a ternary nonstoichiometric intermediate phase is considered.     

Aqueous Mixtures of a Trisiloxane Surfactant and Oil Studied by SANS and NMR Self-diffusion: Effect of Temperature and Oil Concentration

Samples of a poly(ethylene oxide) trisiloxane surfactant, water, and decane have been investigated using pulsed field gradient NMR (PGSE NMR) and small-angle neutron scattering (SANS) to determine the solution structure. The surfactant/water weight ratio has been kept constant at a value of 3/2, with variation of the oil (decane) content. In the neutron scattering measurements the temperature was varied from 23 °C up to the phase separation limit for these systems. The combined NMR and SANS data show that on addition of decane, the system exists as a hexagonal phase of cylindrical decane-containing micelles at all temperatures investigated. The addition of decane changes significantly the values for the structure parameters in the system, inducing an increase in periodicity of 12–15 ?. By substitution of decane with its deuterated equivalent, decane-d₂₂, it was possible to obtain detailed information on the structural organization of the oil component in this ternary mixture.     

Ternary upper-critical-solution-temperature behavior in a blend system comprising poly(2,6-dimethyl-1,4-phenylene oxide), poly(4-methyl styrene), and polystyrene

 Upper-critical-solution-temperature (UCST) behavior in a ternary blend of poly(2,6-dimethyl-1,4-phenylene oxide), poly(4-methyl styrene), and polystyrene is reported. The as-cast ternary blend is immiscible at ambient conditions and comprises two different phases, and, however, turns into a miscible system above the “clarity point” ranging from 160 to 300 °C for different ternary compositions. The maximum clarity point is labeled as the UCST for the ternary system, which is about 295 °C. Above the clarity point, the originally immiscible ternary blend turned into one miscible phase. Owing to the thermodynamic UCST behavior and kinetic hindrance, the immiscible ternary polymer blend can be locked into a pseudo-miscible state if it is heated to a temperature above the clarity point followed by a rapid-cooling processing scheme. The quenched ternary blend can remain in a pseudo-miscible state as long as the service temperature does not exceed the glass-transition temperature of the blend. Received: 17 July 2001 Accepted: 3 October 2001     

Calorimetric study of myoglobin embedded in trehalose-water matrixes

It has been suggested that in ‘dry’ protein-trehalose-water systems, water-mediated hydrogen bond network, whose strength increases by drying, anchors the protein to its surroundings. To further characterize this effect, we performed a DSC study on low-water myoglobin-trehalose systems. The denaturation temperature resulted to increase by decreasing hydration, and linearly correlated to the glass transition temperature of both the ternary protein-water-trehalose and the binary water-trehalose systems. Further measurements are being performed to investigate eventual differences among different saccharides.     

Solubility in the ternary system LiCl + MgCl<Subscript>2</Subscript> + H<Subscript>2</Subscript>O at 60 and 75°C

The solubility of ternary system of lithium, magnesium and chloride and refractive indexes have been determined at 60 and 75°C, respectively. Using the experimental results, the phase diagrams of the ternary system were plotted. The single-salt Pitzer parameters of LiCl and MgCl₂ β⁽⁰⁾, β⁽¹⁾ and C ^ϕ were calculated by using the equations reported by Li Y-H and de Lima at different temperatures, respectively. On the basis of Pitzer ion-interaction model and solubility product equation for mixed electrolytes, the mixing parameters θ_{Li, Mg}, Ψ_{Li, Mg, Cl} and equilibrium constant K _sp were evaluated in this system, which were not reported in literature. A complete phase diagram of the ternary system was predicted at 60 and 75°C. The prediction of solubilities in ternary system was then demonstrated. The calculated solubilities agreed well with the experimental values.