H2O Phase Diagram Research Articles

Comparison of phase diagrams of H2O, D2O, and inert substances

The phase diagrams for the light H2O, heavy D2O water, and inert substances (Ne, Ar, Kr, and Xe) have been compared. A method of choosing the starting point for entropy and internal energy was proposed. It allowed testing the principle of corresponding states using caloric variables. In the given coordinates of temperature, pressure, and chemical potential, the water isotopologues form one group of substances and have similar phase diagrams. The inert substances in the same coordinates form another group of substances with similar phase diagrams. The phase diagrams for inert Ne with significant de Boer quantum parameters differ to a certain extent from the phase diagrams of other inert substances.

Understanding the Water-in-Salt to Salt-in-Water Characteristics across the Zinc Chloride : Water Phase Diagram.

Using a series of time- and temperature-resolved synchrotron diffraction experiments, the relationship between multiple polymorphs of ZnCl2 and its respective hydrates is established. The δ-phase is found to be the pure anhydrous phase, while the α, β, and γ phases result from partial hydration. Diffraction, gravimetric, and calorimetric measurements across the entire ZnCl2·R H2O, 0 > R > ∞ composition range using ultrapure, doubly sublimed ZnCl2 establish the ZnCl2 : H2O phase diagram. The results are consistent with the existence of crystalline hydrates at R = 1.33, 3, and 4.5 and identify a mechanistic pathway for hydration. All water is not removed from hydrated ZnCl2 until the system is heated above its melting point. While hydration/dehydration is reversible in concentrated solutions, dehydration from dilute aqueous solutions can result in loss of HCl, the source of hydroxide impurities commonly found in commercial ZnCl2 preparations. The strong interaction between ZnCl2 and water exerts a significant impact on the solvent water such that the system exhibits a deep eutectic at a composition of about R = 7 (87.5 mol %) and a eutectic temperature below -60 °C.

Dynamic compression of water to conditions in ice giant interiors

Recent discoveries of water-rich Neptune-like exoplanets require a more detailed understanding of the phase diagram of H2O at pressure–temperature conditions relevant to their planetary interiors. The unusual non-dipolar magnetic fields of ice giant planets, produced by convecting liquid ionic water, are influenced by exotic high-pressure states of H2O—yet the structure of ice in this state is challenging to determine experimentally. Here we present X-ray diffraction evidence of a body-centered cubic (BCC) structured H2O ice at 200 GPa and ~ 5000 K, deemed ice XIX, using the X-ray Free Electron Laser of the Linac Coherent Light Source to probe the structure of the oxygen sub-lattice during dynamic compression. Although several cubic or orthorhombic structures have been predicted to be the stable structure at these conditions, we show this BCC ice phase is stable to multi-Mbar pressures and temperatures near the melt boundary. This suggests variable and increased electrical conductivity to greater depths in ice giant planets that may promote the generation of multipolar magnetic fields.

The adsorption thermodynamics of H2O and CO2 on PuO2(1 1 1) surface: A comparative study based on DFT+U-D3

The adsorption thermodynamics of active molecules on PuO2 surface are very important for the long-term storage and surface corrosion of Pu. Here, a comparative study is performed within DFT+U-D3 scheme to investigate the adsorption mechanisms, morphology, and phase diagrams of H2O and CO2 on PuO2(111) surface. The adsorption morphology of H2O will transition from the molecular state to a mixed adsorption state when the coverage is increasing, but CO2 always adsorbs in the molecular state. The differences in adsorption behaviors are mainly due to the hydrogen bonds and Coulomb interactions between the adsorbed molecules. The hydrogen bonds promote the polymolecular adsorption of H2O and the further partial dissociation at high coverage. The Coulomb attractive force among H2O is larger than CO2, and the attractive force among CO2 rapidly decreases as the coverage increases. Unlike the multilayer BET model of H2O adsorption, CO2 adsorption accords with monolayer Freundlich model as revealed by the calculated isotherms. The desorption temperature (Tdes) of H2O and CO2 are agreeing with the experimental results, and the Tdes of H2O is lower than CO2 at the same pressure. This work clarifies the adsorption behaviors of H2O and CO2, and it could provide some important insights into the prediction of the surface corrosion reactions of PuO2 in storage containers.

Valorisation of waste galvanizing dross: Emphasis on recovery of zinc with zero effluent strategy

Galvanizing dross-a waste product from steel industries but it can be a potential secondary resource for zinc through urban mining and recycling. In this concern, a novel and scalable recycling route with zero effluent strategy is developed for the recovery of zinc from galvanizing dross as high grade zinc salts along with value-added products through hydrometallurgical processing. In particular, as-such dross block was leached in 9% (v/v) sulphuric acid medium, wherein strong hydrogen gas effervescence results in alleviating the pulverization and stirring requirements; which are material and energy intensive. Leached zinc is purified and recovered as high purity ZnSO4.(H2O/7H2O) and Zn3(PO4)2.4H2O through controlled crystallization and phosphate precipitation respectively; which find application in fertilizers and anti-corrosive paints. Temperature difference method was opted for the crystallization of zinc sulfate salts, wherein 70 °C and 30 °C were found to be stability range of crystallization of ZnSO4.H2O and ZnSO4.7H2O respectively. ZnSO4–H2O phase diagram is developed using Factsage calculations to corroborate crystallization study. Moreover, exhaustive thermodynamic analysis of Zn2+-PO43--H2O system at 303 K on precipitation of zinc phosphate using di-ammonium hydrogen phosphate (80–240 g/L) is conducted and the results reveal that with increasing pH (3–6), intermediate hydrogen phosphate species (H3PO4, H2PO4− and H2PO42−) decompose to produce stable PO43− ions leading to zinc phosphate precipitation. Impurity like Iron and supernatant solution left after crystallization are recovered as hydrated iron-calcium sulfate mixture and ammonium sulfate salt respectively. This explored route is economical and easily adaptable with zero effluents, therefore, transcends serious challenges in terms of energy requirement, scale-up and effluent generation.

Phase Equilibria and Thermodynamic Properties in the Zinc Chloride–Zinc Methanesulfonate–Water System

Obtained isothermal sections of the ZnCl2–Zn(CH3SO3)2–H2O phase diagram at −10.8 and 25 °C (262.35 and 298.15 K) showed the Zn(CH3SO3)2·4H2O hydrate to be stable under 25 °C in compositions with hi...

Phase Diagram of an Ethylene Glycol–Hexamethylphosphorotriamide System

The phase diagram of an ethylene glycol (EG)–hexamethylphosphorotriamide (HMPT) system is studied over two wide temperature intervals (+25°С…−90°С…+40°С) and (−150°С…+40°С) by means of differential scanning calorimetry using INTERTECH DSC Q100 and METTLER TA4000 DSC instruments (Switzerland) in the DSC30 mode with variable cooling/heating rates. Substantial overcooling of the liquid phase, a glass transition, and different types of interaction are observed in the system. No thermal effects are observed in intermediate range of concentrations during the slow cooling/heating processes, and the system remains liquid until the glass transition. The presence of such a metastable phase is attributed to a sharp rise in the viscosity of the system due to different kinds of interaction between the components. HMPT: 2EG and HMPT: EG compounds with crystallization temperatures of +5 and −0.5°С, respectively, are observed upon rapid cooling and slow heating. Changes in enthalpy are calculated for all of the observed thermal effects. The distinction from the phase diagram of H2O–HMFT (literary data) is explained by the difference in the interactions between system components and by the structural differences between EG and H2O.

Effect of Solvent on Conversion and Selectivity during the Selective Oxidation of Cyclohexane by Nano-V2O5/Ti Membrane Electrode

An electrocatalytic membrane reactor (ECMR) with nano-V2O5 loading porous Ti electrode (V2O5/Ti) as an anode was conducted to the selective partial oxidation of cyclohexane (CHA). The ternary phase diagram of CHA, H2O and solvents was determined. The effect of the solvent system on the conversion rate of CHA and selectivity toward cyclohexanone (K) and cyclohexanol (A) during the selective oxidation of CHA was explored. Cyclic voltammetry (CV) and electron spin resonance (ESR) were employed to monitor the electrochemical behavior of CHA-H2O-solvent (acetone and acetic acid) system. Response surface methodology (RSM) was used to optimize the operating parameters of ECMR. Results showed that the conversion of CHA improved with an increasing solvent polarity. The selectivity to K was related to solvent solubility parameter. 16.8% conversion of CHA, 90.2% selectivity to K and 99.9% selectivity to KA oil were obtained from the reaction system with acetone as solvent and acetic acid as co-solvent (CHA concentration 20 mmol L−1). In particular, acetic acid promoted the production of hydroxyl radicals which played a critical role in the selective oxidation of CHA by ECMR.

Polytherm of the CO(NH2)2–KNO3–H2O phase diagram

The crystallization polytherm of the ternary CO(NH2)2–KNO3–H2O system is plotted for the first time via visual polythermal analysis and calculating ternary eutonics characteristics from data on the boundary elements of two-component systems. The ternary eutonics modeling error does not exceed 3.5%. In addition to the crystallization fields of individual components, the field of the redox reaction that occurs in the system between potassium nitrate and carbamide is shown in the CO(NH2)2–KNO3–H2O diagram by a dashed outline.

The influence of calcium chloride deicing salt on phase changes and damage development in cementitious materials

The conventional CaCl2–H2O phase diagram is often used to describe how calcium chloride behaves when it is used on a concrete pavement undergoing freeze-thaw damage. However, the chemistry of the concrete can alter the appropriateness of using the CaCl2–H2O phase diagram. This study shows that the Ca(OH)2 present in a hydrated portland cement can interact with CaCl2 solution creating a behavior that is similar to that observed in isoplethal sections of a ternary phase diagram for a Ca(OH)2–CaCl2–H2O system. As such, it is suggested that such isoplethal sections provide a reasonable model that can be used to describe the behavior of concrete exposed to CaCl2 solution as the temperature changes. Specifically, the Ca(OH)2 can react with CaCl2 and H2O resulting in the formation of calcium oxychloride. The formation of the calcium oxychloride is expansive and can produce damage in concrete at temperatures above freezing. Its formation can also cause a significant decrease in fluid ingress into concrete. For solutions with CaCl2 concentrations greater than about 11.3% (by mass), it is found that calcium oxychloride forms rapidly and is stable at room temperature (23 °C).

Characterization of solid content and distinction between type A and B crystals of TBAB hydrates by Time Domain NMR

Semiclatrate hydrate crystals of tetra-n-butyl ammonium bromide (TBAB) form at atmospheric pressure and at positive temperature. In suspension with water, they can be used as a heat transport medium or for gas separation. In terms of thermal energy storage and secondary refrigeration applications, TBAB hydrate slurries may be characterized by their flow properties under specific thermophysical conditions. The study presented here investigated one of these important properties, i.e. the crystal content, also called the solid fraction, that is usually estimated using the TBAB:H2O phase diagram. Our investigations revealed that Time-Domain Nuclear Magnetic Resonance (TD-NMR) relaxometry was remarkably sensitive to the solid content of TBAB:H2O hydrate slurries. Non-invasive and non-destructive measurements performed in real time demonstrated the power of NMR relaxometry to identify and quantify TBAB hydrates. Most importantly, NMR both measured and quantified type A and B hydrates, which no other technique can achieve without destroying the crystals or can only perform theoretically on the basis of a phase diagram, and thus without considering the possible conversion of type A to type B hydrates.

Dielectric Anomalies in Crystalline Ice: Indirect Evidence of the Existence of a Liquid–Liquid Critical Point in H2O

The phase diagram of H2O is extremely complex, in particular, it is believed that a second critical point exists deep below the supercooled water (SCW) region where two liquids of different densities coexist. The problem however, is that SCW freezes at temperatures just above this hypothesized liquid-liquid critical point (LLCP) so direct experimental verification of its existence has yet to be realized. Here, we report two anomalies in the complex dielectric constant during warming in the form of a peak anomaly near Tp=203 K and a sharp minimum near Tm=212 K from ice samples prepared from SCW under hydrostatic pressures up to 760 MPa. The same features were observed about 4 K higher in heavy ice. Tp is believed to be associated to the nucleation process of metastable cubic ice Ic and Tm the transitioning of ice Ic to either ices Ih or II depending on pressure. Given that Tp and Tm are nearly isothermal and present up to at least 620 MPa and ending as a critical point near 33-50 MPa, it is deduced that two types of SCW with different density concentrations exists which affects the surface energy of ice Ic nuclei in the "no man's land" region of the phase diagram. Our results are consistent with the LLCP theory and suggest that a metastable critical point exists in the region of 33-50 MPa and Tc > 212 K.

Damage development in cementitious materials exposed to magnesium chloride deicing salt

Magnesium chloride (MgCl2) is used in deicing applications due to its capability to depress freezing temperatures to a lower point than other salts such as sodium chloride (NaCl). The constituents of concrete (i.e., pores solution, calcium hydroxide, aluminate phases, and calcium silicate hydrate gel) can alter the MgCl2–H2O phase diagram when it is used to interpret the performance of concrete. Different chemical reactions may concurrently occur between MgCl2 and cementitious constituents to form brucite, Friedel’s salts, magnesium silicate hydrate, magnesium oxychloride, and/or secondary calcium oxychloride. In this study, it was observed that MgCl2 can be entirely consumed in concrete by the chemical reactions and produce CaCl2. As such, it was found that MgCl2 interacts significantly with a cementitious material and it follows a response that is more similar to the Ca(OH)2–CaCl2–H2O phase diagram than that of the MgCl2–H2O phase diagram. Mortar samples exposed to low concentration MgCl2 solutions (<10% by mass) for a short duration of freezing and thawing showed damage due to ice formation, while for higher concentrations (⩾10% by mass), the damage was most likely due to the chemical reactions between MgCl2 and cementitious constituents at room temperature (23°C). These chemical reactions occurred rapidly (within 5–10min) and caused a significant decrease in subsequent fluid ingress into exposed concrete.

New evaluation of the in vitro response of silicocarnotite monophasic material

In the present work the in vitro behavior in SBF of monophasic silicocarnotite material has been studied combining different techniques such as ICP-OES, FE-SEM-EDS, AFM, XRD, ATR-FTIR, and Confocal Raman microscopy. The nucleation of precipitates phases on the material surface has been observed from the first stage of the immersion test giving place to a precipitated layer with the increasing soaking time. This study put in evidence that this layer is constituted by a biphasic mixture of an amorphous Si–Ca–P–H material and carbohidroxyapatite phase. The response of silicocarnotite in SBF has been discussed on the basis of the CaO–SiO2–P2O5–H2O phase diagram. Finally, a mechanism describing the response of silicocarnotite in vitro conditions is proposed.

Improvements in the assessment of the thermodynamic properties of condensed and gaseous phases of the CsOH compound

Thermodynamic properties of condensed and gas phases of the CsOH compound are assessed. Thermal functions of the condensed phase are those already selected in a preceding compilation with some important modification concerning the melting temperature of CsOH(s,γ) that has been re-evaluated to be T=649±2K from recent mass spectrometric determination certifying the total lack of water impurity and from a comparison between the CsOH–H2O and the RbOH–H2O phase diagram shapes. The vapor phase thermodynamic properties – dealing mainly with the CsOH(g) and Cs2O2H2(g) molecules – are re-evaluated from the selection of a new dimerization equilibrium constant and a thorough analysis of preceding vaporization experiments. Besides, flame studies that give directly the dissociation energies of the CsOH bond are analyzed from the main assumed reactions as well as considering the different analytical methods as used. The reliability of flame results have also been analyzed in this work by thermodynamic adiabatic calculations of the flame. The mean formation enthalpies as retained in the present analysis are:ΔfH°(CsOH,g,298.15K)=-252.7±7.0kJ·mol-1, and ΔfH°(Cs2O2H2,g,298.15K)=-652.0±11.7kJ·mol-1.

H&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt;O and HCl trace gas kinetics on crystalline HCl hydrates and amorphous HCl / H&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt;O in the range 170 to 205 K: the HCl / H&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt;O phase diagram revisited

Abstract. In this laboratory study, H2O ice films of 1 to 2 μm thickness have been used as surrogates for ice particles at atmospherically relevant conditions in a stirred flow reactor (SFR) to measure the kinetics of evaporation and condensation of HCl and H2O on crystalline and amorphous HCl hydrates. A multidiagnostic approach has been employed using Fourier transform infrared spectroscopy (FTIR) absorption in transmission to monitor the condensed phase and residual gas mass spectrometry (MS) for the gas phase. An average stoichiometric ratio of H2O : HCl = 5.8 ± 0.7 has been measured for HCl &amp;amp;centerdot; 6H2O, and a mass balance ratio between HCl adsorbed onto ice and the quantity of HCl measured using FTIR absorption (Nin – Nesc – Nads) / NFTIR = 1.18 ± 0.12 has been obtained. The rate of evaporation Rev(HCl) for crystalline HCl hexahydrate (HCl &amp;amp;centerdot; 6H2O) films and amorphous HCl / H2O mixtures has been found to be lower by a factor of 10 to 250 compared to Rev(H2O) in the overlapping temperature range 175 to 190 K. Variations of the accommodation coefficient α(HCl) on pure HCl &amp;amp;centerdot; 6H2O up to a factor of 10 at nominally identical conditions have been observed. The kinetics (α, Rev) are thermochemically consistent with the corresponding equilibrium vapour pressure. In addition, we propose an extension of the HCl / H2O phase diagram of crystalline HCl &amp;amp;centerdot; 6H2O based on the analysis of deconvoluted FTIR spectra of samples outside its known existence area. A brief evaluation of the atmospheric importance of both condensed phases – amorphous HCl / H2O and crystalline HCl &amp;amp;centerdot; 6H2O – is performed in favour of the amorphous phase.

THE EFFECT OF TEMPERATURE EVOLUTION ON THE INTERIOR STRUCTURE OF H2O-RICH PLANETS

For most planets in the range of radii from 1 to 4 R⊕, water is a major component of the interior composition. At high pressure H2O can be solid, but for larger planets, like Neptune, the temperature can be too high for this. Mass and age play a role in determining the transition between solid and fluid (and mixed) water-rich super-Earth. We use the latest high-pressure and ultra-high-pressure phase diagrams of H2O, and by comparing them with the interior adiabats of various planet models, the temperature evolution of the planet interior is shown, especially for the state of H2O. It turns out that the bulk of H2O in a planet's interior may exist in various states such as plasma, superionic, ionic, Ice VII, Ice X, etc., depending on the size, age, and cooling rate of the planet. Different regions of the mass–radius phase space are also identified to correspond to different planet structures. In general, super-Earth-size planets (isolated or without significant parent star irradiation effects) older than about 3 Gyr would be mostly solid.

In situ Raman observation of the crystallization in NaNO3–Na2SO4–H2O solution droplets

Several double salts have been detected in building materials and most of these salts are incongruently soluble compounds. In contrast to single salts, however, no systematic investigations of the crystallization behavior and deleterious effects of incongruently soluble double salts exist. To assess the damage potential of these salts, a systematic investigation of their highly complex behavior is desirable. This paper deals with the crystallization behavior of various solids in the ternary mixed NaNO3–Na2SO4 system including the formation of the double salt darapskite, Na3NO3SO4·H2O. The crystallization sequence during droplet evaporation experiments at room conditions was determined using Raman and polarization microscopy. The basic idea of this research is to use deviations of the crystallization sequence of a salt or a mixed salt solution from the equilibrium pathway as an indicator to detect the degree of supersaturation. The observed crystallization pathway includes the formation of the metastable phases Na2SO4(III), Na2SO4(V) and darapskite. The experimental observations are discussed on the basis of the NaNO3–Na2SO4–H2O phase diagram and the results provide evidence for crystal growth from highly supersaturated solutions in both systems. If the crystals growing under these conditions are confined, these supersaturations result in substantial crystallization pressures.

High Pressure Kinetics Studies of Water Solidification in Dynamic-DAC

The phase diagram of water is both unusual and complex, exhibiting a wide range of polymorphs including proton-ordered or disordered forms. In addition, a variety of stable and metastable forms are observed. The richness of H2O phases attests the versatility of hydrogen bonded network structures that include kinetically stable amorphous ices. In addition, natural gas hydrates are observed upon cooling and/or pressurization. The structures of gas hydrates are quite different from ices, yet guest molecules are enclathrated inside hydrogen bonded water cages. Hence, the presence of small impurity molecules can affect strongly the behaviours of hydrogen bonding and alter the phase diagram and phase boundaries of H2O. In this paper, we report the effect of methane impurity on solidification and melting of H2O under dynamic loading conditions. The presence of impurity mainly affects the growth rate of metastable ice VII, slowing down from 1.4 m/s in pure H2O to 0.26 m/s in impure H2O, neither the occurrence of metastable ice VII nor the melting of ice VI.

Revision of the NaBO2–H2O phase diagram for optimized yield in the H2 generation through NaBH4 hydrolysis

The binary phase diagram NaBO2–H2O at ambient pressure, which defines the different phase equilibria that could be formed between borates, end-products of NaBH4 hydrolysis, has been reviewed. Five different solid borates phases have been identified: NaBO2·4H2O (Na[B(OH)4]·2H2O), NaBO2·2H2O (Na[B(OH)4]), NaBO2·2/3H2O (Na3[B3O4(OH)4]), NaBO2·1/3H2O (Na3[B3O5(OH)2]) and NaBO2 (Na3[B3O6]), and their thermal stabilities have been studied. The boundaries of the different Liquid + Solid equilibria for the temperature range from −10 to 80 °C have been determined, confirming literature data at low temperature (20–50 °C). Moreover the following eutectic transformation, Liq. → Ice + NaBO2·4H2O, occurring at −7 °C, has been determined by DSC. The Liquid–Vapour domain has been studied by ebullioscopy. The invariant transformation Liq. → Vap. + NaBO2·2/3H2O has been estimated at 131.6 °C. This knowledge is paramount in the field of hydrogen storage through NaBH4 hydrolysis, in which borate compounds were obtained as hydrolysis reaction products. As a consequence, the authors propose a comparison with previous NaBO2–H2O binary phase diagrams and its consequence related to hydrogen storage through NaBH4 hydrolysis.