Equation of State and Thermodynamic Properties of Pure D2O and D2O + H2O Mixtures in and Beyond the Critical Region

A parametric crossover model is adapted to represent the thermodynamic properties of pure D₂O in the extended critical region. The crossover equation of state for D₂O incorporates scaling laws asymptotically close to the critical point and is transformed into a regular classical expansion far from the critical point. An isomorphic generalization of the law of corresponding states is applied to the prediction of thermodynamic properties and the phase behavior of D₂O + H₂O mixtures over a wide region around the locus of vapor-liquid critical points. A comparison is made with experimental data for pure D₂O and for the D₂O + H₂O mixture. The equation of state yields a good representation of thermodynamic property data in the range of temperatures 0.8T _c(x)T1.5T _c(x) and densities 0.35_c(x)1.65_c(x).     

Experimental Study of the Thermodynamic Properties of Diethyl Ether (DEE) at Saturation

The isochoric heat capacities \({({C_{V1}^{\prime}} ,{C_{V1}^{\prime\prime}},{C_{V2}^{\prime}},{C_{V2}^{\prime\prime}})}\), saturation densities (\({\rho _{\rm S}^{\prime}}\) and \(({\rho_{\rm S}^{\prime\prime})}\)), vapor pressures (P _S), thermal-pressure coefficients \({\gamma_V=\left({\partial P/\partial T}\right)_V}\), and first temperature derivatives of the vapor pressure γ _S = (dP _S/dT) of diethyl ether (DEE) on the liquid–gas coexistence curve near the critical point have been measured with a high-temperature and high-pressure nearly constant-volume adiabatic piezo-calorimeter. The measurements of \({({C_{V1}^{\prime}} ,{C_{V1}^{\prime\prime}},{C_{V2}^{\prime}},{C_{V2}^{\prime\prime}})}\) were made in the liquid and vapor one- and two-phase regions along the coexistence curve. The calorimeter was additionally supplied with a calibrated extensometer to accurately and simultaneously measure the PVT, C _V VT, and thermal-pressure coefficient, γ _V , along the saturation curve. The measurements were carried out in the temperature range from 416 K to 466.845 K (the critical temperature) for 17 liquid and vapor densities from 212.6 kg · m^?3 to 534.6 kg · m^?3. The quasi-static thermo- (reading of PRT, T ? τ plot) and baro-gram (readings of the tensotransducer, P ? τ plot) techniques were used to accurately measure the phase-transition parameters (P _S ,ρ _S ,T _S) and γ _V . The total experimental uncertainty of density (ρ _S), pressure (P _S), temperature (T _S), isochoric heat capacities \({({C_{V1}^{\prime}} ,{C_{V1}^{\prime\prime}},{C_{V2}^{\prime}},{C_{V2}^{\prime\prime}})}\), and thermal-pressure coefficient, γ _V , were estimated to be 0.02 % to 0.05 %, 0.05 %, 15 mK, 2 % to 3 %, and 0.12 % to 1.5 %, respectively. The measured values of saturated caloric \({({C_{V1}^{\prime}} ,{C_{V1}^{\prime\prime}},{C_{V2}^{\prime}},{C_{V2}^{\prime\prime}})}\) and saturated thermal (P _S, ρ _S, T _S) properties were used to calculate other derived thermodynamic properties C _P , C _S, W, K _T , P _int, ΔH _vap, and \({\left({\partial V/\partial T}\right)_P^{\prime}}\) of DEE near the critical point. The second temperature derivatives of the vapor pressure, (d² P _S/dT ²), and chemical potential, (d² μ/dT ²), were also calculated directly from the measured one- and two-phase liquid and vapor isochoric heat capacities \({({C_{V1}^{\prime}} ,{C_{V1}^{\prime\prime}},{C_{V2}^{\prime}},{C_{V2}^{\prime\prime}})}\) near the critical point. The derived values of (d² P _S/dT ²) from calorimetric measurements were compared with values calculated from vapor–pressure equations. The measured and derived thermodynamic properties of DEE near the critical point were interpreted in terms of the “complete scaling” theory of critical phenomena. In particular, the effect of a Yang–Yang anomaly of strength R _μ on the coexistence-curve diameter behavior near the critical point was studied. Extended scaling-type equations for the measured properties P _S (T), ρ _S (T), and \({({C_{V1}^{\prime}} ,{C_{V1}^{\prime\prime}},{C_{V2}^{\prime}},{C_{V2}^{\prime\prime}})}\) as a function of temperature were developed.     

PVT Measurements for Pure Ethanol in the Near-Critical and Supercritical Regions

The PVT properties of pure ethanol were measured in the near-critical and supercritical regions. Measurements were made using a constant-volume piezometer immersed in a precision thermostat. The uncertainty of the density measurements was estimated to be 0.15%. The uncertainties of the temperature and pressure measurements were, respectively, 15 mK and 0.05%. Measurements were made along various near-critical isotherms between 373 and 673 K and at densities from 91.81 to 497.67 kg · m⁻³. The pressure range was from 0.226 to 40.292 MPa. Using two-phase PVT results, the values of the saturated-liquid and -vapor densities and the vapor pressure for temperatures between 373.15 and 513.15 K were obtained by means of an analytical extrapolation technique. The measured PVT data and saturated properties for pure ethanol were compared with values calculated from a fundamental equation of state and correlations, and with experimental data reported by other authors. The values of the critical parameters (T _C,P _C,ρ _C) were derived from the measured values of saturated densities and vapor pressure near the critical point. The derived values of the saturated densities near the critical point for ethanol were interpreted in term of the “complete scaling” theory.     

Thermodynamic Properties at Saturation Derived from Experimental Two-Phase Isochoric Heat Capacity of 1-Hexyl-3-methylimidazolium bis[(trifluoromethyl)sulfonyl]imide

New measurements are reported for the isochoric heat capacity of the ionic liquid substance 1-hexyl-3-methylimidazolium bis[(trifluoromethyl)sulfonyl]imide ([C6mim][NTf2]). These measurements extend the ranges of our earlier study (Polikhronidi et al. in Phys Chem Liq 52:657, 2014) by 5 % of the compressed liquid density and by 75 K. An adiabatic calorimeter was used to measure one-phase \((C_{\mathrm{V1}})\) liquid and two-phase \((C_{\mathrm{V2}})\) liquid + vapor isochoric heat capacities, densities \((\rho _s)\), and phase-transition temperatures \((T_s)\) of the ionic liquid (IL) substance. The combined expanded uncertainty of the density \(\rho \) and isochoric heat capacity \(C_\mathrm{V}\) measurements at the 95 % confidence level with a coverage factor of \(k = 2\) is estimated to be 0.15 % and 3 %, respectively. Measurements are concentrated in the immediate vicinity of the liquid + vapor phase-transition curve, in order to closely observe phase transitions. The present measurements and those of our earlier study are analyzed together and are presented in terms of thermodynamic properties \((T_s\), \(\rho _s\), \(C_{\mathrm{V1}}\) and \(C_{\mathrm{V2}})\) evaluated at saturation and in terms of key-derived thermodynamic properties \(C_\mathrm{P}\), \(C_\mathrm{S}\), \(W_\mathrm{S}^{{\prime }}\), \(K_{\mathrm{TS}}^{{\prime }}\), \(\left( {\partial P/\partial T} \right) _{\mathrm{V}}^{\prime }\), and \(\left( {\partial V/\partial T} \right) _\mathbf{P}^{\prime })\) on the liquid + vapor phase-transition curve. A thermodynamic relation by Yang and Yang is used to confirm the internal consistency of measured two-phase heat capacities \(C_{\mathrm{V2}} \), which are observed to fall perfectly on a line as a function of specific volume at a constant temperature. The observed linear behavior is exploited to evaluate contributions to the quantity \(C_{\mathrm{V2}} = f(V, T)\) from chemical potential \(C_{{\mathrm{V}\upmu }} =-T\frac{\mathrm{d}^{{2}}\mu }{\mathrm{d}T^{2}}\) and from vapor pressure \(C_{\mathrm{VP}} =VT\frac{\mathrm{d}^{2}P_{\mathrm{S}} }{\mathrm{d}T^{2}}\). The physical nature and specific details of the temperature and specific volume dependence of the two-phase isochoric heat capacity and some features of the other derived thermodynamic properties of IL at liquid saturation curve are considered in detail.     

Isochoric Heat Capacity Measurements for Light and Heavy Water Near the Critical Point

The isochoric heat capacity was measured for D₂O at a fixed density of 356.075 kg·m^–3 and for H₂O at 309.905 kg·m^–3. The measurements cover the range of temperatures from 623 to 661 K. The measurements were made with a high-temperature, high-pressure, adiabatic calorimeter with a nearly constant inner volume. The uncertainty of the temperature is 10 mK, while the uncertainty of the heat capacity is estimated to be 2 to 3%. Measurements were made in both the two-phase and the one-phase regions. The calorimeter instrumentation also enables measurements of PVT and the temperature derivative (P/T)_V along each measured isochore. A detailed discussion is presented on the experimental temperature behavior of C_V in the one- and two-phase regions, including the coexistence curve near the critical point. A quasi-static thermogram method was applied to determine values of temperature at saturation T_S() on measured isochores. The uncertainty of the phase-transition temperature measurements is about ±0.02 K. The measured C_V data for D₂O and H₂O are compared with values predicted from a recent developed parametric crossover equation of state and IAPWS-95 formulation.     

PVTx Measurements and Partial Molar Volumes for Aqueous Li2SO4 Solutions at Temperatures from 297 to 573 K and at Pressures Up to 40 MPa

Densities of four aqueous Li₂SO₄ solutions (0.0944, 0.2798, 0.6115, 0.8850 molkg^–1) have been measured in the liquid phase with a constant-volume piezometer immersed in a precision liquid thermostat. Measurements were made for ten isotherms between 297 and 573 K. The range of pressure was from 3.9 to 40 MPa. The total uncertainty of density, pressure, temperature, and concentration measurements were estimated to be less than 0.06%, 0.05%, 10 mK, and 0.014%, respectively. The reliability and accuracy of the experimental method was confirmed with measurements on pure water for two isobars at 10 and 38 MPa. Experimental and calculated (IAPWS formulation) densities for pure water show excellent agreement within their experimental uncertainties (average absolute deviation within 0.02 to 0.05%). Saturated liquid densities were determined by extrapolating experimental P- data to the vapor pressure at fixed temperature and composition using an interpolating equation. Apparent and partial molar volumes were derived using measured densities for aqueous solutions and pure water. Derived apparent molar volumes were extrapolated to zero concentration to yield partial molar volumes of electrolyte (Li₂SO₄) at infinite dilution. The temperature, pressure, and concentration dependences of partial and apparent molar volumes were studied. A polynomial type of equation of state for specific volume was obtained as a function of temperature, pressure, and composition by a least-squares method using the experimental data. The average absolute deviation (AAD) between measured and calculated values from this polynomial equation for density was 0.02%. Measured values of solution density, and apparent and partial molar volumes were compared with data reported in the literature by other authors.     

Experimental Study of the Critical Behavior of the Isochoric Heat Capacity of Aqueous Ammonia Mixture

The isochoric heat capacity of a NH₃ + H₂O (0.2607 mole fraction of ammonia) mixture has been measured in the near- and supercritical regions. Measurements were made in the single- and two-phase regions including the coexistence curve using a high-temperature, high-pressure, nearly constant-volume adiabatic calorimeter. Measurements were made along 38 liquid and vapor isochores in the range from 120.03 kg · m⁻³ to 671.23 kg · m⁻³ and at temperatures from 478 K to 634 K and at pressures up to 28 MPa. Temperatures at the liquid–gas phase transition curve, T _S(ρ), for each measured density (isochore) and the critical parameters (T _C and ρ _C) for the 0.2607 NH₃ + 0.7393  H₂O mixture were obtained using the quasi-static thermograms technique. The expanded uncertainty of the heat-capacity measurements at the 95 % confidence level with a coverage factor of k = 2 is estimated to be 2 % to 3 % in the near-critical and supercritical regions, 1.0 % to 1.5 % in the liquid phase, and 3 % to 4 % in the vapor phase. Uncertainties of the density, temperature, and concentration measurements are estimated to be 0.06 %, 15mK, and 5×10⁻⁵ mole fraction, respectively. An unusual behavior of the isochoric heat capacity of the mixture was found near the maxcondetherm point (in the retrograde region). The value of the Krichevskii parameter was calculated using the critical properties data for the mixture and vapor-pressure data for the pure solvent (H₂O). The derived value of the Krichevskii parameter was used to analyze the critical behavior of the strong (C _P , K _T ) and weakly (C _V ) singular properties in terms of the principle of isomorphism of critical phenomena in binary mixtures. The values of the characteristic parameters (K ₁, K ₂), temperatures (τ ₁, τ ₂), and the characteristic density differences (Δρ ₁, Δρ ₂) were calculated for the NH₃ + H₂O mixture by using the critical-curve data.     

Growth and Properties of Hybrid Organic‐Inorganic Metalcone Films Using Molecular Layer Deposition Techniques

Molecular layer deposition (MLD) is a useful technique for fabricating hybrid organic‐inorganic thin films. MLD allows for the growth of ultrathin and conformal films using sequential, self‐limiting reactions. This article focuses on the MLD of hybrid organic‐inorganic films grown using metal precursors and various organic alcohols that yield metal alkoxide films. This family of metal alkoxides can be described as “metalcones”. Many metalcones are possible, such as the “alucones” and “zincones” based on the reaction of trimethylaluminum and diethylzinc, respectively, with various organic diols such as ethylene glycol. Alloys of the various metalcones with their parent metal oxide atomic layer deposition (ALD) films can also be fabricated that have an organic‐inorganic composition that can be adjusted by controlling the relative number of ALD and MLD cycles. These metalcone alloys have tunable chemical, optical, mechanical, and electrical properties that may be useful for designing various functional films. The metalcone hybrid organic‐inorganic materials offer a new tool set for engineering thin film properties.     

Atomic Layer Deposition of Y2O3 Using Tris(butylcyclopentadienyl)yttrium and Water

Russian Microelectronics - In this work, atomic-layer deposition (ALD) of yttrium oxide (Y2O3) was demonstrated using tris(butylcyclopentadienyl)yttrium (Y(CpBut)3) and H2O . Yttrium precursor...