Calvet Calorimeter Research Articles

Excess second-order thermodynamic derivatives of the {2-propanol + water} system from 313.15 K to 403.15 K up to 140 MPa. Experimental and Monte Carlo simulation study

In this work, the density of the aqueous solution of 2-propanol was measured from atmospheric pressure up to 140MPa in the 313.15–403.15K temperature interval throughout the composition range by using a vibrating tube densimeter. From these data, the volume, the isobaric thermal expansivity and the isothermal compressibility were derived using usual procedures, as well as their respective excess properties. Likewise, measurements of the isobaric heat capacity of the system were carried out by a Calvet calorimeter at p=0.1, 20, 40MPa from 313.15K to 393.15K at various concentrations of the alcohol. All this rich experimental information has been compared with Monte Carlo simulations, which were performed in coincident thermodynamic conditions by using a potential based on the OPLS for 2-propanol and the TIP4P/2005 for water, with the Lorentz–Berthelot mixture rules for determining crossing interactions. They were found to be in reasonable agreement with all observations. Likewise, the experimental results were compared with data previously reported in the field in order to further ensure the reliability of this work.

Sequential Evolution of Different Phases in Metastable Gd2–xCexZr2–xAlxO7 (0.0 ≤ x ≤ 2.0) System: Crucial Role of Reaction Conditions

The Gd(2-x)Ce(x)Zr(2-x)Al(x)O7 (0.0 ≤ x ≤ 2.0) series was synthesized by the gel combustion method. This system exhibited the presence of a fluorite-type phase, along with a narrow biphasic region, depending upon the Ce/Gd content in the sample. Thermal stability of these new compounds under oxidizing and reducing conditions has been investigated. The products obtained on decomposition of Gd(2-x)Ce(x)Zr(2-x)Al(x)O7 in oxidizing and reducing conditions were found to be entirely different. It was observed that in air the fluorite-type solid solutions of Gd(2-x)Ce(x)Zr(2-x)Al(x)O7 composition undergo phase separation into perovskite GdAlO3 and fluorite-type solid solutions of Gd-Ce-Zr-O or Ce-Zr-Al-O depending upon the extent of Ce and Al substitution. On the other hand, Gd(2-x)Ce(x)Zr(2-x)Al(x)O7 samples on heating under reducing conditions show a phase separation to CeAlO3 perovskite and a defect-fluorite of Gd2Zr2O7. The extent of metastability for a typical composition of Gd(1.2)Ce(0.8)Zr(1.2)Al(0.8)O7 (nano), Gd(1.2)Ce(0.8)Zr(1.2)Al(0.8)O(6.6) (heated under reduced conditions), Gd(1.2)Ce(0.8)Zr(1.2)Al(0.8)O7 (heated in air at 1200 °C) has been experimentally determined employing a high temperature Calvet calorimeter. On the basis of thermodynamic stability data, it could be inferred that the formation of a more stable compound in the presence of two competing cations (i.e., Gd(3+) and Ce(3+)) is guided by the crystallographic stability.

Standard molar enthalpy of formation of Bi2WO6(s) and Bi2W2O9(s) compounds

Bismuth tungstates have attracted lot of attention due to their excellent intrinsic properties, such as ferroelectric-piezoelectricity, catalytic behavior, nonlinear dielectric susceptibility and photo catalytic activity. Thermodynamics plays an important role in predicting long term stability of these materials under different reactive conditions. The present paper describes determination of standard molar enthalpies of formation of Bi2WO6(s) and Bi2W2O9(s) compounds employing a high temperature solution calorimeter. The reaction enthalpies of Bi2O3(s), WO3(s), Bi2WO6(s) and Bi2W2O9(s) in liquid Na2O+MoO3 solvent (3:4M ratios) at 983K were measured using a Calvet Calorimeter. The standard molar enthalpy of formation of the compounds at 298K (ΔfH°298) were calculated by combining the experimentally determined values of the reaction enthalpies with the auxiliary data from the literature. The values of ΔfH°298 of Bi2WO6(s) and Bi2W2O9(s) at 298K were found to be −(1426.0±7.9)kJ·mol−1 and −(2379.7±6.8)kJ·mol-1, respectively.

Heat capacities of selected chlorohydrocarbons

Isobaric heat capacities in the liquid phase of seven selected halogenated hydrocarbons (1,1,2-trichloroethylene, (Z)- and (E)-1,2-dichloroethylene, 1,1-dichloropropane, 1,2-dichloropropane, 2,2-dichloropropane, and (trichloromethyl)benzene) were measured by using a highly sensitive Tian–Calvet calorimeter in the temperature range from 260K to 340K. Due to high volatility of the studied compounds the correction for sample evaporation was applied. Vapor pressure equations required for applying this correction were iteratively developed by simultaneous correlation of the literature vapor pressures and related thermal data (calorimetrically obtained vaporization enthalpies, heat capacities in the liquid and ideal-gas state). The thermodynamic properties in the ideal gaseous state were calculated using the methods of statistical thermodynamics based on fundamental vibrational frequencies and molecular structure data calculated by DFT at the B3LYP/6-311+G(2df,p) level of theory. Data on liquid heat capacities obtained in this work were merged with available literature data, critically assessed and correlated as a function of temperature.

Influence of dilution on the thermophysical properties of Dax peloid (TERDAX®)

In thermotherapy, the efficiency of a peloid depends in particular on its thermal quality and an appropriate and detailed chemical and physical characterization is necessary to understand the thermal behaviour of these products. The most influential physical properties are the specific heat capacity, the thermal conductivity and the density. This work focuses on the study of the evolution of those properties of Dax peloid mixed with thermal and mineral water as a function of the mud concentration. The experimental specific heat capacity data were measured using a Calvet calorimeter, SETARAM BT 2.15, which permits studying with high precision all kind of substances and materials (oils, polymers, hydrates, powders) and simulate almost any process condition (reactions, crystallisation, freezing, etc.) and in the temperature range from 298.15 to 314.15K. The pycnometer method and an Anton-Paar DMA-4500 vibrating-tube densimeter were used to measure density values while the thermal conductivity was determined by the Model KD2 Pro, Decagon Devices Inc. The experimental data show the expected behaviour: the specific heat capacity increases with temperature and decreases with concentration whereas density decreases with temperature and increases with concentration. Besides the thermal conductivity increases with both temperature and concentration. The results of this study will be used to determine the best proportion between peloid and mineral water for an individual mud bath.

The Effect of Sb Addition on Sn-Based Alloys for High-Temperature Lead-Free Solders: an Investigation of the Ag-Sb-Sn System

Today there is renewed interest in alloys belonging to the Sb-Sn-X (X = Cu, Ag, Bi) ternary systems and their phase equilibria, phase transformations, and thermodynamic properties because of their possible use as high-temperature lead-free solders in the electronics industry. The integral mixing enthalpy of Ag-Sb-Sn liquid alloys has been measured along five different sections (Ag0.25Sn0.75, Ag0.50Sn0.50, Sb0.30Sn0.70, Sb0.50Sn0.50, and Sb0.70Sn0.30) at 530°C, 600°C, and 630°C, using a high-temperature Calvet calorimeter by dropping pure elements (Ag or Sb) in the binary alloy liquid bath. The ternary extrapolation models of Muggianu and Toop were used to calculate the integral enthalpy of mixing and to compare measured and extrapolated values. Selected ternary alloys have been prepared for thermal investigation by using a differential scanning calorimeter at different heating/cooling rates in order to clarify the temperature of the invariant reactions and the crystallization path.

Instrumentation and calibration of the Calvet calorimeter

The original Calvet calorimeter, made from aluminum block, were instrumented. The cells for the solution calorimetry measurement have been projected and constructed. The calibration of calorimeter was performed by measurement of the dependence of reference material on temperature and the influence of mechanical events on thermograms. The enthalpies of solution in water and 0.01 M HCl were investigated for chlorides and bromides of alkali metals (Na···Cs), PrBr3 and Rb3PrBr6. The enthalpies of solution of alkali halides have been compared to the reference data obtained for infinite solution. The decomposition of Rb3PrBr6 at temperatures lower than 399 K has been stated. The enthalpy of solution PrBr3 at 298.15 K has been determined.

Specific heat of mixtures of bentonitic clay with sea water or distilled water for their use in thermotherapy

In thermotherapy, an appropriate and detailed chemical and physical characterization of the different clays and thermal muds is necessary for the use of these products. In order to predict the thermal behaviour of a mud the analysis of its physical properties is required; among these, those that have bigger influence are the specific heat capacity, the thermal conductivity and the density. This work focuses on the study of the behaviour of the specific heat of a bentonitic clay (composed mainly of 55% Na-saturated smectite, 28% sepiolite, and 15% illite) mixed with distilled water or sea water as a function of the water concentration in the temperature range 293.15–317.15 K. The experimental data were measured using a Calvet calorimeter, SETARAM BT 2.15, which permits studying with high precision all kind of substances and materials (oils, polymers, hydrates, powders) and simulate almost any process condition (reactions, crystallisation, freezing, etc.). The obtained specific heat values in the studied temperature range are between 851 and 889 J kg −1 K −1 for mineral phase, 3479 and 3505 J kg −1 K −1 for 19.9% bentonite + distilled water, and 2724 and 2758 J kg −1 K −1 for 39.8% bentonite + sea water. The results of this study can be used in the spas or thermal centres to determine the suitability and quality of the bentonitic muds for pelotherapy.

Enthalpy increment and heat capacity of Pb 3Bi

Enthalpy increments of Pb 0.71Bi 0.29 compound and enthalpy change associated with peritectic decomposition reaction of the compound were determined using high temperature Calvet calorimeter. The heat capacity of the compound was determined in the temperature range 230–440 K using heat flow DSC. The enthalpy increment data was fitted into the following polynomial equations. Δ H 298.15 K T ( J/mol ) = − 6492.2 + 21.2775 T + 0.00919 T 2 − 199,341 T ( 298.15 – 457 K ) The enthalpy of decomposition reaction of the compound at the peritectic temperature, 457 K, was found to be 984 J/mol. The heat capacity of the compound determined using DSC was fitted into the following polynomial equation. C P ( J/mol K ) = 23.486 − 0.01482 T + 97,338.4 T 2 ( 228 – 457 K ) The heat capacity values obtained from DSC were in reasonably good agreement with the values calculated from enthalpy increment equation and both were slightly higher than the heat capacity values calculated using Neumann–Kopp's rule.

Environmental exposure of 2LiBH4+MgH2 using empirical and theoretical thermodynamics

It has been shown that the consequence of environmental exposure can be qualitatively predicted by modeling the heat generated as a result of environmental exposure of reactive hydrides along with heat loss associated with conduction and convection with the ambient surroundings. To this end, an idealized finite volume model was developed to represent the behavior of dispersed hydride from a breached system. Semi-empirical thermodynamic calculations and substantiating calorimetric experiments were performed in order to quantify the energy released, energy release rates and to quantify the reaction products resulting from water and air exposure of a lithium borohydride and magnesium hydride combination. The hydrides, LiBH4 and MgH2, were studied in a 2:1 “destabilized” mixture which has been demonstrated to be reversible. Liquid water hydrolysis reactions were performed in a Calvet calorimeter equipped with a mixing cell using pH-neutral water. Water vapor and gaseous oxygen reactivity measurements were performed at varying relative humidities and temperatures by modifying the calorimeter and utilizing a gas circulating flow cell apparatus. The results of these calorimetric measurements were used to develop quantitative kinetic expressions for hydrolysis and air oxidation in these systems. Thermodynamic parameters obtained from these tests were then incorporated into a computational fluid dynamics model to predict both the hydrogen generation rates and concentrations along with localized temperature distributions. The results of these numerical simulations can be used to predict ignition events and the resultant conclusions will be discussed.

Calorimetric investigations on stoichiometric barium and uranium oxides

Heat capacities and enthalpy increments of barium uranates: BaU 2O 7(s), Ba 2U 3O 11(s), Ba 2.875UO 5.875(s) and Ba 3UO 6(s) were measured using a differential scanning calorimeter and a high-temperature Calvet calorimeter. The heat capacities and enthalpy increments were measured in the temperature range 126–304 K and 299–1011 K, respectively. A set of self consistent thermodynamic functions such as entropy, Gibbs energy function, heat capacity and Gibbs energy and enthalpy of formation values for BaU 2O 7(s), Ba 2U 3O 11(s), Ba 2.875UO 5.875(s) and Ba 3UO 6(s) have been computed for the first time using the data obtained in the present study and other available experimental data.

Calibration of a low temperature calorimeter and application in the determination of isobaric heat capacity of 2-propanol

Nowadays, the experimental thermodynamic characterization of solvents in an extended range of temperatures and pressures is essential for the development of a wide variety of industrial applications (refrigeration, reactors, pumping, etc.). Moreover, accurate experimental data are also the key for the successful development and subsequent benchmarking of thermodynamic theoretical models. In the particular case of isobaric heat capacities, there are quite a lot of reported experimental high temperature data but, on the other hand, low temperature data are practically inexistent for most compounds. Bearing this limitation in mind, the present work is focused on the development of a new calibration methodology for calorimetric determination of isobaric heat capacities in liquid state at low temperatures. For this purpose, a Calvet calorimeter, SETARAM BT 2.15 has been used. By means of the calibration procedure explained below, this calorimeter allows to determine phase transitions and thermodynamic properties in a wide range of temperature (233.15–473.15 K) and pressure (0.1–100 MPa).

Spectroscopic and thermal studies of bentonites from Ünye, Turkey

Three bentonites from Turkey were investigated by X-ray diffraction (XRD), X-ray fluorescence (XRF), differential thermal analysis (DTA), thermogravimetric analysis (TG), Fourier transform infrared (FT-IR), magic angle spinning nuclear magnetic resonance (MAS NMR) and surface area measurement techniques. The XRD patterns showed that all three bentonite samples (B1, B2 and B3) were mainly composed of montmorillonite accompanied by cristobalite. In addition, albite appears in B3 sample studied. The heats of immersion of the bentonite samples (B1, B2 and B3) measured with a Calvet calorimeter at 30 °C in water were determined as −75.70, −54.69 and −68.22 J/g, respectively.

Enthalpy of formation of the La–Mg intermediate phases

The aim of this work is to complete the available set of thermodynamic data on the La–Mg system in order to get reliable optimisation of this system by the CALPHAD method. Indeed the CALPHAD method requires a large set of consistent input data including both phase diagram and thermodynamic data. The enthalpies of formation of the La–Mg intermediate compounds were determined at 298 K by means of solution calorimetry in liquid Sn in a Tian–Calvet calorimeter. In these experiments, the partial enthalpies of solution of the compounds at infinite dilution in liquid tin were measured at 665 K. The enthalpies of formation of LaMg, LaMg 2 and La 2Mg 17 compounds were also calculated at 0 K by density functional theory to compare experimental and calculated values.

The thermochemistry of coronene revisited

A thermochemical study of coronene has been performed by several calorimetric techniques, including micro-combustion calorimetry in a Calvet calorimeter and conventional isoperibol static bomb combustion calorimetry. Standard enthalpies of combustion and formation were derived from the experimental results. Reliable results for the enthalpy of sublimation were obtained by using a quartz crystal microbalance and then applied to derive an accurate enthalpy of formation in the gas phase. The enthalpy associated with a suitable homodesmic reaction, computed from density functional theory energies and the experimental enthalpies of formation for pyrene, triphenylene, and benzene, were used in order to obtain the theoretical Δ f H m ∘ ( g, 298.15 K ) for coronene. A comparison against the experimental values was done. The study supplies an assessed series of thermochemical data for this key compound.

Excess Enthalpy and Luminescence Studies of SnO2 Nanoparticles

The extra reactivity of nano materials is attributed to the excess surface energy stored in the sample. The excess enthalpy of SnO2 nano-particles were measured as a function of particle size using a calvet calorimeter. SnO2 with particle size 11, 27, 47 nm and bulk samples (1 microm) were dropped from room temperature to 987, 936 and 885 K and their H(T)-H298 values were determined. The excess enthalpies for SnO2 samples with particle sizes 11, 27 and 47 nm compared to the bulk sample calculated from the difference between H(T)-H298 values of the nano and the bulk samples were found to be 15.06, 3.05, 2.21 kJ x mol(-1) respectively. Luminescence experiments reveal that the surface trap electron density decreases with increase of particle size. The excess enthalpy is related to the surface trap intensity.

Standard enthalpy of formation of compounds of the Cd–Zr system

Thermodynamic properties of two intermetallic phases CdZr 2(s) and Cd 3Zr(s) in the binary Cd–Zr system have been investigated. The standard molar enthalpy of formation Δ f H 298 0 of CdZr 2(s) and Cd 3Zr(s) was obtained by measuring the reaction enthalpy of CdZr 2(s), Cd 3Zr(s) and Zr(s), respectively, using Cd(l) in a Calvet calorimeter. The values of Δ f H 298 0 of CdZr 2(s) and Cd 3Zr(s) at 298 K were found to be −(61.7 ± 1.2) kJ mol −1 and −(72.3 ± 0.9) kJ mol −1, respectively.

Thermochemical characteristics of La n+1 Ni nO 3 n+1 oxides

Lanthanum nickelates: La 2NiO 4+ δ , La 3Ni 2O 7− δ , La 4Ni 3O 10− δ and LaNiO 3− δ the members of Ruddlesden–Popper series La n+1 Ni n O 3 n+1 were prepared using citrate route. Dissolution enthalpies of complex oxides as well as a number of subsidiary substances were measured by means of Calvet calorimeter in 1 M solution of hydrochloric acid at 25 °C. The dissolution scheme of complex oxides in hydrochloric acid was proposed and enthalpies of formation of the complex oxides from binary oxides were calculated considering oxygen nonstoichiometry of these substances. Enthalpies of step-by-step oxidation were evaluated. Partial enthalpy contribution of LaO layers was calculated endothermic equals to 30.9 J/mol while partial enthalpy contribution of perovskite LaNiO 3 layers was negative equals to −97.0 J/mol. Enthalpy of formation of any complex oxide of Ruddlesden–Popper series fits very well to the linear regression based on these values.

Enthalpies of formation of Cd 0.917Sr 0.083, Cd 0.857Sr 0.143 and Cd 0.667Sr 0.333 intermetallic compounds

Cadmium is expected to be the solvent for pyrochemical processing of the metallic nuclear fuel. Therefore, thermodynamic properties of cadmium with various fuel and clad elements are of interest. Enthalpies of formation of the intermetallic compounds of Cd–Sr system, Cd 0.917Sr 0.083, Cd 0.857Sr 0.143 and Cd 0.667Sr 0.333 were determined by precipitation using Calvet calorimeter. Enthalpies of formation of the compounds were found to be −3.05 ± 0.5 kJ mol −1 at 723 K, −14.2 ± 0.7 kJ mol −1 at 843 K and −28.4 ± 0.8 kJ mol −1 at 863 K, respectively. Enthalpies of formation of Cd 0.917Sr 0.083 and Cd 0.857Sr 0.143 were also determined by partial enthalpy of formation measurements and the values were found to be −3.9 ± 1.1 kJ mol −1 at 723 K and −13.42 ± 1.2 kJ mol −1 at 843 K, respectively. Miedema model was used to estimate the enthalpies of formation of these compounds and the estimated values were compared with the experimentally determined values.

Saturated Heat Capacities of Some Linear and Branched Alkylbenzenes between (332 and 401) K

The saturated heat capacities of some linear alkylbenzenes (ethylbenzene, propylbenzene, butylbenzene, hexylbenzene, 1-phenylheptane, and 1-phenylhexadecane) and branched alkylbenzenes (m-xylene, cumene, (1-methylpropyl)benzene, (1,1-dimethylethyl)benzene, and (2-methylpropyl)benzene) in the temperature range from (332.15 to 401.15) K have been measured. A Calvet calorimeter C80D from Setaram (France) with batch cells modified from the standard vessels of Setaram, along with the “step by step method”, has been used to perform the measurements. The estimated uncertainty of the saturated heat capacities was better than 0.5 % for the substances with higher purity and of the order of 1 % for the others. In the literature there exists csat(T) data for some of the liquids studied. Agreement with our measurements is within the range of the experimental uncertainties.