Quaternary Phase Diagram Research Articles

Screening Approach for Identifying Cocrystal Types and Resolution Opportunities in Complex Chiral Multicomponent Systems

Cocrystallization of racemic-compound-forming chiral molecules can result in conglomerate cocrystals or diastereomerically related cocrystals, which enable the application of chiral separation techniques such as preferential crystallization and classic resolution. Here, a systematic method to identify the types and phase diagrams of cocrystals formed by chiral target compounds and candidate coformers in a particular solvent system is presented, which allows the design of suitable chiral resolution processes. The method is based on saturation temperature measurements of specific solution compositions containing both enantiomers of chiral molecules and a coformer. This method is applied to analyze three different systems. For racemic phenylalanine (Phe) in water/ethanol mixtures one of the enantiomers selectively cocrystallizes with the opposite enantiomer of valine (Val), forming the more stable diastereomerically related cocrystal. The racemic compound ibuprofen crystallizes with the nonchiral coformer 1,2-bis(4-pyridyl)ethane (BPN) as racemic compound cocrystals. More interestingly, when it is combined with trans-1-(2-pyridyl)-2-(4-pyridyl)ethylene (BPE), the racemic compound ibuprofen cocrystallizes as a conglomerate, which in principle enables the application of preferential crystallization of this racemic compound. The systematic method shows the benefit of using pseudo-binary phase diagrams. Such pseudo-binary phase diagrams depict the saturation temperature on a very specific route through the quaternary phase diagram, allowing the identification of various cocrystal types as well as the corresponding cocrystallization conditions. The systematic method can be used to identify a suitable solid phase for chiral separation, and the obtained phase diagram information enables the performance of a crystallization-mediated chiral resolution process design. Such a guideline for a chiral resolution process design has never been reported for conglomerate cocrystal systems such as IBU:BPE, presented in this study.

Atom probe characterisation of segregation driven Cu and Mn–Ni–Si co-precipitation in neutron irradiated T91 tempered-martensitic steel

The T91 grade and similar 9Cr tempered-martensitic steels (also known as ferritic-martensitic) are leading candidate structural alloys for fast fission nuclear and fusion power reactors. At low temperatures (300–400 °C) neutron irradiation hardens and embrittles these steels, therefore it is important to investigate the origin of this mode of life limiting property degradation. T91 steel specimens were separately neutron irradiated to 2.14 dpa at 327 °C and 8.82 dpa at 377 °C in the Idaho National Laboratory Advanced Test Reactor. Atom probe tomography was used to investigate the segregation driven formation of Mn–Ni–Si-rich (MNSPs) and Cu-rich (CRP) co-precipitates. The precipitates increase in size and, slightly, in volume fraction at the higher irradiation temperature and dose, while their corresponding compositions were very similar, falling near the Si(Mn,Ni) phase field in the Mn–Ni–Si projection of the Fe-based quaternary phase diagram. While the structure of the precipitates has not been characterised, this composition range is distinctly different than that of the typically cited G-phase. The precipitates are composed of CRP with MNSP appendages. Such features are often observed in neutron irradiated reactor pressure vessel (RPV) steels. However, the Si, Ni, Mn, P and Cu solutes concentrations are lower in the T91 than in typical RPV steels. Thus, in T91 precipitation primarily takes place in solute segregated regions of line and loop dislocations. These results are consistent with the model for radiation induced segregation driven precipitation of MNSPs proposed by Ke et al. Cr-rich alpha prime (α’) phase formation was not observed.

Topological transformations of phase diagrams of quaternary systems through the boundary tangential azeotrope stage

The specific features of quaternary system phase diagram transformations induced by formation ofboundary tangential azeotrope were investigated. The characteristics of bifurcation states corresponding to the transition from one structure of the diagram to another were determined. The principal possible transformations of diagrams with varying pressure were illustrated by the systems acetone-chloroform-ethanol-water and chloroform-ethanol-cyclohexane-water. The obtained results expand the understanding of thermodynamics of heterogeneous equilibria of multicomponent systems and make it possible to solve the practical problem of maintaining favorable phase equilibrium conditions for rectification in certain pressure ranges.

Liquidus Phase Diagram of CaO-SiO2-La2O3-Nb2O5 System with w(La2O3) = 15 to 25 Pct

The thermodynamic information of the CaO-SiO2-Nb2O5-La2O3 system is of great significance for the utilization of Nb and RE resources from minerals. In this article, the phase equilibria of the CaO-SiO2-Nb2O5-La2O3 system were investigated by equilibrium experiments. Twelve kinds of phase equilibria were determined, and then a spatial liquidus phase diagram was constructed. The primary phase fields of SiO2, CaNb2O6, LaNbO4, Ca2Nb2O7 and CaSi3La4O13 were determined, respectively. Meanwhile, the liquidus surfaces in the primary phase fields of SiO2, Ca2Nb2O7 and LaNbO4 were determined. Finally, the CaO-SiO2-Nb2O5-(17.5, 20, 22.5, 25 pct)La2O3 pseudo-ternary phase diagrams were also obtained. In addition to the experimental results, two theoretical rules applicable for the spatial quaternary phase diagram were also proposed to obtain indirect information on the bivariate interface between two adjacent primary phase fields. The first rule was the “tangent line rule” for judging related precipitation reaction types, and the second rule was the “highest temperature rule” for judging related temperature trends. The present work will be helpful for the utilization of Nb and RE resources and for the establishment of related thermodynamic databases.

Determination, Construction, and Evaluation of Ternary and Quaternary Solid–Liquid Phase Equilibrium of Uric Acid, Adenine, and Guanine in Water

In this work, nine ternary phase diagrams and three quaternary phase diagrams of different systems at 298.15, 308.15, and 318.15 K were constructed. The ternary solid–liquid phase equilibrium of (u...

Quaternary phase diagrams as a tool for ionic cocrystallization: the case of a solid solution between a racemic and enantiopure ionic cocrystal

Quaternary phase diagram of ionic cocrystals with solid solution formation is generated and dissolution surface is depicted clearly by contour lines.

Deracemization in a Complex Quaternary System with a Second-Order Asymmetric Transformation by Using Phase Diagram Studies.

Invited for the cover of this issue is the group of Gérard Coquerel at Université de Rouen Normandie. The image depicts a pyramid-like tetrahedron of the quaternary phase diagram showing where symmetry breaking can take place. Read the full text of the article at 10.1002/chem.201903338.

Deracemization in a Complex Quaternary System with a Second-Order Asymmetric Transformation by Using Phase Diagram Studies.

A productive deracemization process based on a quaternary phase diagram study of a naphthamide derivative is reported. New racemic compounds of an atropisomeric naphthamide derivative have been discovered, and a quaternary phase diagram has been constructed that indicated that four solids are stable in a methanol/H2 O solution. Based on the results of a heterogeneous equilibria study showing the stable domain of the conglomerate, a second-order asymmetric transformation was achieved with up to 97 % ee. Furthermore, this methodology showcases the chiral separation of a stable racemic compound forming system and does not suffer from any of the typical limitations of deracemization, although application is still limited to conglomerate-forming systems. We anticipate that this present study will serve as a fundamental model for the design of sophisticated chiral separation processes.

Phase equilibria in low basicity region of CaO-SiO2-Nb2O5-(5 wt%, 10 wt%, 15 wt%) La2O3 system

The lack of thermodynamic information, such as primary phase fields and liquidus temperatures, in the CaO-SiO2-Nb2O5-La2O3 quaternary system phase diagram has restricted the comprehensive utilization of the niobium (Nb) and rare earth (RE) resources. In this work, the phase equilibria in low basicity region (w(CaO)/w(SiO2)<1) of CaO-SiO2-Nb2O5-(0–15 wt%)La2O3 system at 1373–1873 K were experimentally studied by thermodynamic equilibrium experiment, and then, the results were analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy dispersive spectrometry (EDS). Additionally, an optimized method was proposed to process the compositions of equilibrium liquid phases at different temperatures. According to the experimental results, the univariate line between CaNb2O6, SiO2 and LaNbO4 primary phase fields, interface between CaNb2O6 and SiO2 primary phase fields and isothermal liquidus surfaces in SiO2 primary phase field were determined. Finally, the spatial phase diagram of CaO-SiO2-Nb2O5-La2O3 within specific region was constructed, and furthermore, the phase diagram was also presented in CaO-SiO2-Nb2O5 pseudo-ternary system with w(La2O3) = 5 wt%, 10 wt% and 15 wt%. The research results have guiding significance for the improvement of related phase diagram and the comprehensive utilization of Nb and RE resources.

Effect of Si on the stability of NbCr2 Laves phase in Cr-Mo-Nb system

An experimental study on a part of the Cr-Nb-Mo-Si quaternary phase diagram associated with the NbCr2 Laves phase is conducted. It is found that most of the Si added to 50Cr-30Mo-20Nb alloys is distributed in the NbCr2 Laves phase and that the amount of Mo in the Laves phase increases with increasing Si addition. The Laves phase in Cr-Mo-Nb alloys with higher Si addition is found to be more stable. Electronic structure calculations based on density functional theory are performed to examine the effects of Mo and Si co-doping on the formation enthalpy of NbCr2. It is found that the co-doping effectively increases the stability of the Laves phase. This result is consistent with the effect of the atomic size ratio DA/DB on the stability of the AB2 Laves phase, where DA and DB are the average atomic diameters of atoms occupying the A and B sites of the AB2 structure, respectively.

Formation sequence of Fe–Al intermetallic phases at interface between solid Fe and liquid Zn–6Al–3Mg alloy

In the present study, we characterized the Fe–Al intermetallic phases formed in interstitial-free (IF) steel hot-dipped in a Zn–6Al–3Mg (wt.%) alloy melt at different temperatures (400, 460 and 500 °C) and dipping times (from 2 to 3600 s). Chemical composition analyses indicated Fe dissolution into the Zn alloy melt even after 2 s of dipping. Microstructural characterization revealed the initial formation of a continuous θ-Fe4Al13 phase layer, followed by the local growth of η-Fe2Al5 phase toward both steel and Zn alloy melt sides during the hot-dipping process. After long-term hot-dipping, further growth of the η phase was accompanied by significant dissolution of Fe into the Zn alloy melt, resulting in the loss of thickness of the IF steel sheets. Altogether, we rationalized the formation mechanism of Fe–Al intermetallic phases and their associated growth at the interface between solid Fe and liquid Zn alloy in terms of a Zn–Al–Mg–Fe quaternary phase diagram, calculated according to thermodynamic database available in the literature.

Phase diagrams of the quaternary system K+, NH4+//Cl−, SO42−-H2O at 273.15 K and their application

In order to produce chloride-free K-N compound fertilizers by the reaction of KCl (carnallite) and (NH4)2SO4 as raw materials, the phase equilibrium of the mutual quaternary system K+, NH4+//Cl−, SO42−-H2O and its two ternary subsystems KCl-NH4Cl-H2O, K2SO4-(NH4)2SO4-H2O were measured by isothermal method at 273.15 K. And the corresponding phase diagrams were plotted and analysed. The equilibrium phase diagram of the quaternary system K+, NH4+//Cl−, SO42−-H2O shows that there is one saturation point and three solid phase fields of crystallization. Three fields of crystallization represent solid solution salts corresponding to (K1−t, (NH4)t)2SO4, (K1−m, (NH4)m)Cl and ((NH4)n, K1−n)Cl respectively. The phase analysis shows that field of (K1−t, (NH4)t)2SO4 is larger than other crystalline fields, and there is no crystalline field of pure potassium sulfate, which indicates that the K1-t, (NH4)t)2SO4 is easy to crystallize out from solution. By analysing and calculating the phase diagrams of K+, NH4+//Cl−, SO42−-H2O at 273.15 K and 323.15 K, chloride-free K-N compound fertilizers (K1−t, (NH4)t)2SO4) can be obtained using KCl and (NH4)2SO4 as raw materials at 273.15 K, and ((NH4)t, K1−t)Cl can crystallize out at 323.15 K. The new technology shows the advantages of effective utilization of carnallite resources. The research on this quaternary phase diagram is the foundation of the chloride-free potash production by the reaction of carnallite and ammonium sulfate.

Design and property investigations of manganese-based cathode material LiδNi0.25-zMn0.75-zCo2zOy (0 ≤ δ ≤ 1.75) for lithium-ion batteries

On the foundation of LiNiCoMn quaternary phase diagram, a series of manganese-based cathode materials LiδNi0.25-zMn0.75-zCo2zOy (0 ≤ δ ≤ 1.75, z = 0, 0.05, 0.15 and 0.25) have been designed and systematically studied. These materials are synthesized via a carbonate co-precipitation route and followed by a solid-state reaction. The effects of cobalt and lithium contents on phase transformations morphologies, and electrochemical behaviors of the cathode materials are overall compared and evaluated. The results reveal that, with δ increases, structures of the materials present phase evolution from spinel phase (δ ≤ 0.5) to integrated composite of spinel and layered phase (Fd3¯m and R3¯m, 0.5 < δ < 1.5) and then to a pure layered phase (R3¯m and C2/m, δ ≥ 1.5). In addition, size of primary particle and roughness of the secondary particles are also affected by δ value. Moreover, it is found that the initial discharge capacity and cycle stability of the cathode materials can be improved by a proper amount of cobalt substitution for both spinel and layered structure. These studies on the LiNiMnCo quaternary phase diagram provide a new insight into the research and development of the cathode materials for advanced lithium-ion batteries.

Phase stability and structural comparison of phases in the Cu-Zn-Sn-S system using solid-state NMR

Phases in the Cu-Zn-Sn-S system are of interest to the solar and thermoelectrics communities because all elements are earth-abundant and non-toxic. A better understanding of the structures of these phases and the equilibria between them is necessary to guide device manufacturers. This work reviews all the phases reported in this system and reports which phases form and are stable at 200 °C and 400 °C. In this work, the stable phases in the Cu-Zn-Sn-S system (Cu4Sn7S16, Cu4SnS4, Cu2ZnSnS4, and Cu2SnS3) are synthesized and their structures are investigated using solid-state NMR, X-ray diffraction, and Raman spectroscopy. The existing Cu-Sn-S and Cu-Zn-Sn-S phase diagrams are revised based on our synthesis results. Cu3SnS4 and Cu2ZnSn3S8 are removed from the quaternary and ternary phase diagrams because we did not observe either phase. Prior reports (in thin films and nanocrystals) of Cu3SnS4 may be related to trace amounts of In or large surface areas. Monoclinic Cu2SnS3 is not stable at 400 °C and, at this temperature, a disordered tetragonal phase is stable. At lower temperatures (room-temperature and 200 °C ), this same (disordered) tetragonal phase is stable at compositions that are Cu-rich and Sn-poor from Cu2SnS3. Cu4SnS6 was added to the phase diagram at 400 °C. Significant differences in reaction rate when forming Cu4SnS4 from either elemental or binary sulfide precursors are noted and explained. The NMR results are generalized to aid in distinguishing octahedral versus tetrahedral Sn4+ coordinations.

Phase equilibria in medium basicity region of CaO-SiO2-Nb2O5-(5%, 10%, 15%) La2O3 system

The thermodynamic information, such as primary phase fields and liquidus temperatures, in the CaO-SiO2-Nb2O5-La2O3 quaternary system phase diagram is important for the comprehensive utilization of niobium and rare earth resources. In the current work, the phase equilibria of CaO-SiO2-Nb2O5-(0–15%)La2O3 system within medium basicity region at 1373–1673 K were experimentally studied. X-ray diffraction (XRD), scanning electron microscope (SEM), and energy dispersive spectrometer (EDS) were used to identify the type and composition of equilibrium phases in the quenched samples after thermodynamic equilibrium experiment. According to the experimental results, the univariate line between CaNb2O6-Ca2Nb2O7-LaNbO4 primary phase fields, the bivariate interface between CaNb2O6-Ca2Nb2O7 primary phase fields, the bivariate interface between CaNb2O6-LaNbO4 primary phase fields, and isothermal liquidus surfaces in CaNb2O6 and Ca2Nb2O7 primary phase fields were determined, respectively. Finally, CaO-SiO2-Nb2O5-La2O3 phase diagram within specific region was spatially constructed, and the results were also presented in the form of CaO-SiO2-Nb2O5 pseudo-ternary system phase diagram with w(La2O3) = 5%,10% and 15%. The research results are important for the comprehensive utilization of Nb and RE resources, meanwhile, they are also important for the improvement of related phase diagrams.

Three-Dimensional Predominance Volume Diagrams: The Ni-As-S-O System

The 3D predominance volume diagram (PVD) for the Ni-As-S-O system at 700 K (427 °C) was constructed using independent gases O2, SO2, and As4O6. The system has 15 four-condensed-phase invariant points. Invariant points, fixed by any combination of boundaries and condensed phases totaling four, were determined by a Gibb’s minimization routine that searched from a corner of the PVD along each undetermined line emanating from this and subsequently-identified invariants. The search direction was determined from the cross product of the two independent planes’ normal direction vectors. The 0.25 atm and 1.00 atm isobaric surfaces intersect the Ni3As2O8, NiO, NiSO4, Ni1−xS, NiS2, and Ni11As8 phases. The 1.00 atm surface also intersects the NiAs phase. The PVD results agree with published ternary and quaternary phase diagram Alkemade lines. If the roasting of gersdorffite (NiAsS) parallels the roasting of enargite (Cu3AsS4), gersdorffite is expected to initially react irreversibly with O2 in the roasting gas to form NiS and NiSO4 topochemical layers with arsenic being expelled as As4O6 gas and perhaps As4 gas once a diffusion-controlled topochemical reaction sequence is established. Thermochemical calculations showed that the formation of NiO from NiSO4 and Ni3As2O8, if present, becomes more favorable as the temperature is increased with complete conversion to NiO above 1086 K and 1160 K (813 °C and 887 °C), respectively, at 1.00 atm.

Morphological changes in asymmetric PES membranes by addition of polyurethanes: A thermodynamic and experimental study

The effect of adding two types of polyurethane (PU) namely: polyether urethane (ETPU) and polyester urethane (ESPU), on polyether sulfone (PES) blend membrane is investigated. The morphology of the prepared membranes is studied by phase diagram. For this purpose, Hansen solubility parameters are calculated by Van Krevelen and Hoy methods, and the ternary and quaternary phase diagrams for the prepared membranes are produced using Flory Huggins theory. The membranes are prepared by phase inversion method. Different tests such as permeability, water contact angle, FTIR and SEM images are carried out to determine the membranes' characteristics. The results indicate that porosity and gas permeability of PES blend membranes increase by addition of PU as an additive. The PES/ETPU blend membrane has higher permeability and porosity in comparison with the PES/ESPU due to higher compatibility of the polymers and lower de-mixing rate between solvent and non-solvent in PES/ESPU membrane. It should be mentioned that by increasing the additive concentration, viscosity increases and high viscosity acts as a barrier to mass transfer between the solvent and non-solvent. Therefore, the delayed de-mixing rate reduces pore size and permeability.

Dual-Drug Chiral Resolution: Enantiospecific Cocrystallization of (S)-Ibuprofen Using Levetiracetam

In this work we show the feasibility of resolving a racemic drug substance with a second chiral drug. Via enantiospecific cocrystallization a dual-drug cocrystal is obtained. Such a method can be useful not only for chiral resolution but also for the parallel creation of dual-drug formulations. Here, racemic ibuprofen is resolved using levetiracetam through the formation of an enantiospecific cocrystal. Cocrystallization is utilized as a resolution tool for (in this case) (S)-ibuprofen, the active enantiomer. To find the right conditions to resolve the system, the appropriate ternary and quaternary phase diagrams were constructed. Since these diagrams are governed by thermodynamics, where the kinetic forms are prevented via seeding, the system is robust under scale-up conditions and is an interesting alternative to chiral chromatography or enantioselective synthesis for the pharmaceutical industry.

Solid–Liquid Equilibria in the Quaternary System Na+,K+//HPO42–,Cl––H2O and Its Subsystems Na+//HPO42–,Cl––H2O, K+//HPO42–,Cl––H2O, and Na+,K+//HPO42––H2O at 298.2 K

The solid–liquid equilibrium of the quaternary system Na+,K+//HPO42–,Cl––H2O and its subsystems Na+//HPO42–,Cl––H2O, Na+, K+//HPO42–,Cl––H2O, Na+,K+//HPO42––H2O at 298.2K were investigated by the isothermal solution saturation method. The solubility of salts and the equilibrium solid phases were determined. The ternary phase diagram, quaternary dry-salt phase diagram, and the water-content diagram were constructed. There is one invariant point, two univariant curves, and four crystallization regions in the ternary system Na+//HPO42–,Cl– −H2O and K+//HPO42–,Cl––H2O. The ternary system Na+,K+//HPO42––H2O contains two invariant points, three univariant curves, and six crystallization regions. The quaternary system Na+,K+//HPO42–,Cl––H2O contains three invariant points, seven univariant curves, and five crystallization regions corresponding to KCl, NaCl, Na2HPO4·12H2O, Na2HPO4·7H2O, and K2HPO4·3H2O. In the quaternary system, KCl occupies the largest crystallization region while K2HPO4·3H2O crystallization region is the smallest. Three kinds of hydrated salts were found in the system while there is no double salts or solid solution. HPO42– is the main factor that affects the relative water content in the liquid phase. All the data and results obtained in this paper are of great significance to the crystallization technology of K2HPO4 and the new production process of KH2PO4.

Solidification sequence of Ni-Si-Cr ~3wt% B brazing alloys

Various Ni-Si-Cr-B brazing alloys with a similar boron content (3 wt%) are investigated. Alloy compositions cover a section of the quaternary phase diagram that connects BNi-3 to BNi-9 ternary alloys for industrial use. Samples were melted and solidified at low cooling rate (1 K/min) under secondary vacuum to minimize oxidation and the metastable phase formation. Transformation temperatures, microstructures, and chemical analyses are reported. Experimental conditions were found to play a significant role on the accuracy of obtained data. Thermodynamic data were collected upon heating. Before analyzing quaternary alloys, the results of investigated ternary alloys were compared with the literature and discussed.