Solid Phase Equilibria Research Articles

Phase equilibria of quaternary system NaCl-NaBr-Na2B4O7-H2O at 348 K

The phase equilibria of quaternary system NaCl-NaBr-Na2B4O7-H2O at 348 K were studied by the isothermal equilibrium method. The solubilities and densities of the equilibrium solution were determined. According to the experimental data, the phase diagram, density-composition diagrams and water content diagram of the quaternary system at 348 K were plotted respectively. And the phase diagram consists of one univariant curve, two crystallization fields and without any invariant point of the quaternary system. The equilibrium solid phases of the two crystallization fields were Na(Cl, Br) and Na2B4O7·5H2O. The experimental results show that the quaternary system contained solid solution. The densities of the solution decrease with increasing NaCl concentration and increase with increasing NaBr concentration.

A Pseudo-Binary Diagram of the (Bi,Pb)-Sr-Ca-Cu-O System

A pseudo-binary phase diagram of the (Bi,Pb)-Sr-Ca-Cu-O system along the Bi1.6Pb0.4Sr2Can-1CunOx line is constructed. This resulting phase diagram shows three kinds of peritectic reactions, one eutectic reaction and one peritectoid reaction. The equilibrium solid phases in this diagram are the 2201 (n=1), 2212 (n=2), 2223 (n=3) and (Sr,Ca)CuO2 (n→∝) phases. The 2201 phase is solid solution which is stable at 1≤n≤1.2. The eutectic composition point is close to the maximum solid solution composition of the 2201 phase. The temperature interval between the peritectic reaction of L + (Sr,Ca)2CuO3 + (Sr,Ca)CuO2 → 2212 and the eutectic reaction of L → 2201 + 2212 is only about 3°C. For the composition of n=3, CaO and the liquid phase are stable at temperatures above 940°C. During the cooling, these two phases react peritectically to (Sr,Ca)2CuO3. At around 890°C, (Sr,Ca)2CuO3 reacts with the liquid to produce (Sr,Ca)CuO2. At around 865°C, (Sr,Ca)2CuO3 and (Sr,Ca)CuO2 react with the liquid to produce the 2212. The 2223 phase is transformed by a peritectoid reaction of the 2212 phase and residual (Sr,Ca)2CuO3, (Sr,Ca)CuO2.

Behavior of alkali element uranosilicates and uranogermanates in saturated aqueous solutions

The behavior of uranosilicates and uranogermanates of the series AIHBIVUO6·nH2O (AI = Li, Na, K, Rb, Cs, NH4; BIV = Si, Ge) in aqueous solutions at pH from 0 to 14 was studied. The acid-base intervals of the existence of these compounds were determined, their conversion products were identified, and the solubility of AIHBIVUO6·nH2O was measured. The physicochemical analysis of the heterogeneous systems AIHBIVUO6·nH2O-aqueous solution was performed. The equilibrium constants of the dissolution reactions and the Gibbs functions of formation of AIHBIVUO6·nH2O were calculated. The solubility curves and the speciation diagrams of U(VI) and element BIV in aqueous solutions and of the equilibrium solid phases were constructed.

Solid–Liquid Equilibria in the Quaternary Systems KCl–KBr–K2B4O7–H2O and KCl–KBr–K2SO4–H2O at 373 K

Solid–liquid equilibria in the quaternary systems KCl–KBr–K2B4O7–H2O and KCl–KBr–K2SO4–H2O at 373 K were measured by the isothermal solution saturation method. The equilibrium solid phases, solubilities of salts, and densities of saturated solutions in the two systems were determined. The experimental data are used to plot the solubility diagrams, water content diagrams, and solution density diagrams of the two systems. It was found that both systems contain the solid solution of KCl and KBr [K(Cl,Br)], so their solubility diagrams have no invariant point, but each has a univariant curve and two crystallization regions. In the first system, the solids are K(Cl,Br) and potassium borate aquahydrate (K2B4O7·4H2O), and in the second system, the solids are K(Cl,Br) and potassium sulfate (K2SO4).

Physicochemical Analysis of Inorganic Systems

The results of phase equilibria predictions for the Na,K∥SO4,CO3,HCO3,F-H2O six-component system at 25°C in the trona crystallization region (Na2CO3 · NaHCO3 · 2H2O) by the translation method are considered. Trona, which is one of the equilibrium solid phases of the title system at 25°C, is involved in equilibria that correspond to 14 invariant points, 37 monovariant curves, and 28 divariant fields. These data were used to construct a fragment of the phase equilibrium diagram of the title system in the trona crystallization region.

The Correlation between Reduced Glass Transition Temperature and Glass Forming Ability of Undercooled Polymeric Glasses

The thermodynamic behaviour of glass forming undercooled melt have been studied by analysing the temperature dependence of the Gibbs free energy difference (Δ<i>G</i>) for six polymeric glass forming materials[O-terphenyl, Tri-α-naphthyl benzene, Glycerol, Ethanol, 2-methylpentane and Phenyl salicylate (salol)] between the undercooled melt and the corresponding equilibrium solid phases. The expression obtained by expanding free energies of the undercooled liquid and solid phases of the materials in the form of Taylor’s series expansion. The procedure for the estimation of the ideal glass transition temperature has been reviewed together its importance in the glass forming ability of materials. The glass forming ability of undercooled materials is also explained in terms of ratio of reduced glass transition temperature and ideal glass transition temperature. It has also reported that Glycerol has the largest melting interval with the poorest glass forming ability among these six polymers. It has also been found that the best polymeric glass forming materials are at near eutectic composition. There is a strong correlation between glass forming ability of these polymeric materials.

Behavior of uranosilicates MIII(HSiUO6)3·10H2O (MIII = La-Lu, Y) in aqueous solutions

The behavior of uranosilicates MIII(HSiUO6)3·10H2O (MIII = La-Lu, Y) in aqueous solutions in the pH range from 0 to 14 was studied. The acidity intervals in which the compounds preserve their composition and structure were found, the uranosilicate conversion products were identified, and the solubility of MIII(HSiUO6)3·10H2O was determined. With the mathematical apparatus of equilibrium thermodynamics applied to heterogeneous systems MIII(HSiUO6)3·10H2O-aqueous solution, the equilibrium constants of dissolution and the Gibbs functions of formation of uranosilicates were calculated, the solubility curves were plotted, and the speciation diagrams of U(VI), Si(IV), and elements M(III) in solutions and equilibrium solid phases were constructed.

Facile proton conduction in H+/Li+ ion-exchanged garnet-type fast Li-ion conducting Li5La3Nb2O12

Garnet-type Li5La3Nb2O12, among several other Li-stuffed garnet compounds, is known to be unstable under moisture and undergoes H+/Li+ ion-exchange at room temperature. While there have been reports on proton-exchange in water, the transport of the protons in the garnet structure is yet to be characterized by electrical methods. In this work, proton-exchange was performed on the pellet form of Li5La3Nb2O12 for 4, 7, and 10 days, while the pellet generally showed less proton-exchange due to less surface area exposed to water, longer treatment times did allow the reaction to proceed further. Neutron diffraction (ND) studies were utilized to locate the H-site in the garnet-type structure and to confirm which Li ion sites were exchanged. For H exchanged Li5La3Nb2O12, the neutron diffraction studies indicated that H exchanged preferentially for Li in the distorted octahedral sites of the Iad space group (no. 230). AC impedance measurements were done on as-prepared Li5La3Nb2O12 under 3% H2O + N2 and 3% D2O + N2, which suggested proton conduction under humid conditions at 23–300 °C. Li5La3Nb2O12 shows a proton conductivity of 10−5 S cm−1, of the same order of magnitude as Li ion conduction, at room temperature in humidity where protons seem to be incorporated from the solid and gas phase equilibrium reaction. Proton reversible Nafion electrode experiments indicate facile proton conduction in Li garnets under humidity.

State of uranophosphates MII(PUO6)2·nH2O (MII = Mn2+, Co2+, Ni2+, Cu2+, Zn2+, Cd2+, Pb2+) in aqueous solutions

The stability of uranophosphates MII(PUO6)2·nH2O(MII = Mn, Co, Ni, Cu, Zn, Cd, Pb) in water and aqueous HClO4 and NaOH solutions was studied. The acid-base limits of the existence of these compounds were determined, the products of their conversion into phases of other compositions and structures were identified and studied, and the solubility of MII(PUO6)2·nH2O was determined. From the data obtained, the solubility products and Gibbs functions of formation of uranophosphates and the solubility curves were calculated, and the speciation diagrams of U(VI), P(V), and M(II) in solutions and equilibrium solid phases were plotted.

Solubility of the System KOH–K2CrO4–Al2O3–H2O at 150 °C in a High Alkali Concentrated Region

The phase equilibria for the system KOH–K2CrO4–Al2O3–H2O and its subsystems at 150 °C in a high alkali concentrated region were investigated. In the concentrated alkali region of the system and its subsystem KOH–Al2O3–H2O, the equilibrium solid-phase K2O·Al2O3·2H2O was found. This is different from the system KOH–Al2O3–H2O at low temperature from which the equilibrium solid-phase K2O·Al2O3·3H2O was discovered. The salting-out effect of KOH and potassium aluminate to K2CrO4 is strong. These findings can provide a significant and precious database for the production of K2CrO4 and the removal of alumina from the concentrated alkali solution that is produced in the chromate cleaner production process.

Study of the state of uranoarsenates MII(AsUO6)2·nH2O(MII = Mn2+, Co2+, Ni2+, Cu2+, Zn2+, Cd2+, Pb2+) in aqueous solutions

State of uranoarsenates MII(AsUO6)2·nH2O (MII = Mn, Co, Ni, Cu, Zn, Cd, Pb) in aqueous solutions in a wide range of acidity (pH 0–14) was studied. Acid-base boundaries of existence of the compounds were estimated, products of conversion were identified, and solubility of MII(AsUO6)2·nH2O was determined. On the basis of the obtained data the solubility products and Gibbs functions of formation of uranoarsenates, and the solubility curves were calculated, phase diagrams of uranium(VI) and arsenic(V) in solutions and in equilibrium solid phases were constructed with the use of the equilibrium thermodynamics technique.

Mutual Solid Solubility and Phase Equilibrium in the System BaTiO3–BaCeO3

Mutual Solid Solubility and Phase Equilibrium in the System BaTiO3–BaCeO3

Mutual Solid Solubility and Phase Equilibrium in the System BaTiO3–BaCeO3

A series of (1-x)BaTiO3–xBaCeO3 (x = 0.1–1.0) ceramics were prepared at 1480 °C by a cold-pressing ceramic technique. The mutual solid solubility and phase equilibrium in the system BaTiO3–BaCeO3 were investigated by X-ray diffraction analysis, scanning electron microscopy, and Raman spectroscopy. The results indicate that no pure BaCeO3 phase can be separated from the Ba(Ti1-xCex)O3 phase. The mutual solid solution limits of BaCeO3 and BaTiO3 are given. In the range of 0.4 ≤x ≤0.8, the system is well separated into the Ce- and Ti-rich Ba(Ti,Ce)O3 perovskite phases, corresponding to Ce/Ti ratios of 4.3:1 and 1:2, respectively.

Experimental simulation of phase relationships and zoning of magmatic nickel-copper sulfide Ores, Russia

The quasiequilibrium directed crystallization technique was used for experimental simulation of zoning characteristic of Cu-rich pyrrhotite-chalcopyrite and pyrrhotite-cubanite-mooihoekite-haycockite ores at the Oktyabr’sky deposit. Directed crystallization of samples I (Fe 32.55, Cu 10.70, Ni 5.40, S. 51.00, Pt = Pd = Rh = Ir= Au = Ag = 0.05 at %) and II (Fe 33.74, Cu 15.94, Ni 1.48, S. 48.75, Pt = Pd = 0.05 at %) was performed. These samples approximate average composition of the ore. Monosulfide (mms) and intermediate (iss) solid solutions progressively crystallized from the melt. The curves of ore element distribution in samples have been drawn. The partition coefficients (k) of ore elements between solid solutions and sulfide melt have been determined depending on melt composition. The paths of melt, mss, and iss compositions are supplemented by tie lines connecting compositions of equilibrium liquid and solid phases. The phase composition of samples after cooling was studied using an optical microscope, XRD, and microprobe. The zoning of sample I is described by the following sequence of phases: monoclinic pyrrhotite → hexagonal pyrrhotite + tetragonal chalcopyrite → tetragonal and cubic chalcopyrite + pentlandite + bornite. Crystallized sample II consists of four zones: (1) hexagonal pyrrhotite and isocubanite; (2) hexagonal pyrrhotite, cubanite, and pentlandite; (3) low-S pc-phase close to haycockite and pentlandite; and (4) mooihoekite, pentlandite, and bornite mixtures. This sequence corresponds to the secondary zoning, which reflects both the primary fractionation of components and the solid-phase reactions during cooling of the crystallized sample. The Rh, Ru, and Ir partition coefficients between mss and melt have been measured, and speciation of PGM in samples has been identified. The results obtained are compared with typical natural Cu-rich sulfide ore of the Oktyabr’sky deposit.

Liquid–solid phase transitions of Lennard-Jones particles confined to slit pores: towards the construction of temperature–pressure-slit width phase diagram

Molecular dynamics simulations are performed to investigate the phase behaviour of the Lennard-Jones (LJ) particles confined to slit pores with width h. For (in reduced unit based on the LJ parameter σ), the liquid–solid phase equilibria are estimated over the thermodynamic parameter space of temperature (T)–lateral pressure ()–slit width (h), on the basis of the Clausius–Clapeyron equation for the quasi-2D system. This is the first step towards the construction of the full phase diagram. For , we obtain the freezing/melting points and the crystal structure as a function of h. Even for , the abnormality in the freezing/melting points found previously (for h < 6) still appears. The new analysis confirms our previous simulation results for a few specific h values.

Solid phase extraction and uptake properties of multi-walled carbon nanotubes of different dimensions towards some nitro-phenols and chloro-phenols from water

Equilibrium sorption studies and solid phase extraction (SPE) of various phenols (Phenol (Ph), 2-chlorophenol (2-CP), 3-chlorophenol (3-CP), 4-chlorophenol (4-CP), 2-nitrophenol (2-NP), 4-nitrophenol (4-NP), 2,4-dinitrophenol (2,4-DNP)) on oxidized and raw multi-walled carbon nanotubes (MWCNTs) of various external diameters (10–20, 10–30, 20–40, 40–60 and 60–100 nm) and various lengths (short: 1–2 µm and long: 5–15 µm) were tested. Equilibrium sorption studies showed that 2-NP fits the Langmuir isotherm model (LIM), while the other phenolic compounds fit the Freundlich isotherm model (FIM). There was generally an inverse relation between external diameter of MWCNT and its sorption capacity towards phenolic compounds. Long MWCNT showed higher sorption capacity than short MWCNT. Thus dimensions of MWCNT play a role in retaining the sorbed molecules. Oxidation of MWCNT caused a decrease in sorption capacity of phenolic compounds of lower acidity where hydrophobic interaction is predominant, while it caused an increase in sorption capacity of phenolic compounds of higher acidity where H-bonding is predominant. The dependence of sorption on the acidity of phenols (pKa values) indicates that the basic groups (pyrone-like groups) on the MWCNT surface play a role in the sorption process. In SPE experiments, it was found that hydrogen peroxide-oxidized MWCNT of external diameter 40–60 nm and length 5–15 µm was the best extractant at pH 6.5 using acetonitrile as eluting solvent. The optimized SPE procedure gave detection limits range: 0.027–0.202 ng mL−1 within the studied concentration range (10–100 ng mL−1). Application of the optimum SPE method on spiked tap water, reservoir water and stream water gave recovery range of 84.3–100% for 2-CP, 3-CP and 4-CP (%RSD range 2.8–9.2%); while Ph, 2-NP, 4-NP, and 2,4-DNP gave recoveries <67.6%.

Colloid chemistry principles of separation of pure alkyl sulfates

Sodium dodecyl sulfate and other alkyl sulfates were treated by the method of polythermal conductometry to remove primary alcohols. The electrical conductivity polytherms were analyzed. The composition of the liquid and solid phases in equilibrium in the mixed solutions was determined. The method of the synthesis of chemical purity colloids of alkyl sulfates and other ionogenic micelle forming surfactants was suggested based on the optimal choice of crystallization temperature of the solutions.

Thermodynamic Properties and Crystal Structures of the Adductive 2,6-Naphthalenedicarboxylic Acid Crystallization with N,N-Dimethyl Acetamide and N-Methyl Pyrrolidone

The crystal structures and thermodynamic properties of NDA-DMAC and NDA-NMP adduct crystals, the solubilities of 2,6-naphthalenedicarboxylic acid (NDA) in N,N-dimethyl acetamide (DMAC) and N-methyl pyrrolidone (NMP) over a temperature range from (293.2 to 373.2) K were studied in this paper. The results show that: (1) The asymmetric units of NDA-DMAC and NDA-NMP adduct crystals both contain one half molecule of NDA and one molecule of the solvent which are linked mainly by hydrogen bonds. (2) The thermal stabilities of the two adducts are both poor, and the initial dissociation temperature of NDA-DMAC and NDA-NMP adducts are about 306.29 K and 322.75 K, respectively. (3) The solubilities of NDA in DMAC and NMP solvents at (293.2 to 373.2) K both increase with the rise of experimental temperature. Below the dissociation temperature, the equilibrium solid phase is the adduct crystal with the adduct solvent. Otherwise, the equilibrium solid phase is the pure NDA solid with the adduct crystal dissociating. Th...

Stability of the bcc phase of4He close to the melting curve: A molecular dynamics study

We have investigated whether the Aziz et al. [J. Chem. Phys. 70, 4330 (1979)] model for ${}^{4}$He renders the body-centered cubic phase more stable than the face-centered cubic phase in the proximity of the melting curve. Using molecular dynamics, we have simulated these solid phases in equilibrium with the liquid at a number of densities. In contrast to previous free energy molecular dynamics calculations, the model stabilizes the body-centered cubic phase. The stability field is just 5${}^{\ensuremath{\circ}}$ wide below the melting curve at pressures around 140 Kbar and about 70${}^{\ensuremath{\circ}}$ wide at pressures around 750 Kbar. Considering that the body-centered cubic phase is dynamically unstable at low temperature, this result bears striking similarities to transition metal phase diagrams.

PHASE EQUILIBRIUM IN THE LOW-Ca SIDE OF Mg-Zn-Ca SYSTEM AT 400℃

Zn addition to the magnesium alloys could result in the age-hardening, and the age- hardening response of Mg-Zn alloys could be further enhanced by the ternary addition of Ca. In order to better understand the mechanism of the Mg-Zn-Ca base alloy design, the solubility of Mg-based solid solution and relative phase equilibrium at 400 in low-Ca side of the Mg-Zn-Ca system have been investigated by SEM, EPMA, XRD and DSC. It has been shown that T1 and T2 are still main ternary compounds in the Mg-rich corner at 400 with the addition of Ca to Mg-Zn system, but only T1 phase could be in equilibrium with the Mg-based solid solution, and the two-phase field of α-Mg+T1 becomes narrow. The liquid phase with the Ca content less than 8.4% (atomic fraction) exists in the low-Ca side at 400 , which could be in equilibrium with α-Mg. But liquid phase could not exist in the Mg-Zn-Ca alloys when the Zn/Ca ratio is less than 1.7. At 400 , there are four three- phase fields consisting of α-Mg+Mg2Ca+T1, α-Mg+T1+Liq, Liq+T1+T2 and Liq+T2+Mg2Zn3 in the Mg-Zn-Ca system, respectively.