Adiabatic Heat-capacity Research Articles

Heat capacity and thermodynamic properties of PbS: Optimization based on calorimetric and electrochemical data

Heat capacity of PbS (galena) has been measured in the temperature range from 12 to 338 K using adiabatic calorimetry. Results of the measurements are consistent with previous adiabatic calorimetric data measurements but differ notably from those obtained by relaxation calorimetry. Using experimental data on adiabatic heat capacity measurements in the range of 12–338 K (including our data), results of EMF measurements, and literature data on H0(T) – H0(298.15 K) as inputs, we have optimized the thermodynamic properties of lead sulfide (PbS, galena) based on the quasi-harmonic model vibrational spectrum proposed by Kieffer and advanced to consider intrinsic anharmonicity. In this approach, the volume and temperature dependence of vibrational frequencies are considered, and the enthalpy of formation of PbS, ΔfH0(298.15 K), is treated as an optimized model parameter. The thermodynamic properties of PbS are described with a single set of model parameters over the entire range of its stability (0–1374 K) at a pressure of 1 bar. The model can be optimized based on either the reduced (Cp0 and ΔfG0(T)) or full (Cp0, H0(T) – H0(298.15 K), ΔfG0(T)) datasets. The both variants of the optimization predict the similar thermodynamic properties of PbS, in particular, values of the enthalpies of formation differ less than 0.1 kJ mol−1 and are consistent with ΔfH0(298.15 K) obtained experimentally by oxide melt solution calorimetry. The low-temperature adiabatic calorimetry data and high-temperature results of EMF experiments (or other reliable experimental data on ΔfG0(T)) represent a minimal sufficient set of input data providing optimization of thermodynamic properties at ambient pressure by the technique established in present study.

Simulation and Techno-Economic Analysis of a Power-to-Hydrogen Process for Oxyfuel Glass Melting

As an energy-intensive industry sector, the glass industry is strongly affected by the increasingly stringent climate protection targets. As established combustion-based production systems ensure high process stability and glass quality, an immediate switch to low greenhouse gas emission processes is difficult. To approach these challenges, this work investigates a step-by-step integration of a Power-to-Hydrogen concept into established oxyfuel glass melting processes using a simulation approach. This is complemented by a case study for economic analysis on a selected German glass industry site by simulating the power production of a nearby renewable energy park and subsequent optimization of the power-to-hydrogen plant performance and capacities. The results of this study indicate, that the proposed system can reduce specific carbon dioxide emissions by up to 60%, while increasing specific energy demand by a maximum of 25%. Investigations of the impact of altered combustion and furnace properties like adiabatic flame temperature (+25 °C), temperature efficiency (Δξ = −0.003) and heat capacity flow ratio (ΔzHL = −0.009) as a function of H2 content in the fuel mixture and resulting furnace efficiencyindicate that pure hydrogen-oxygen combustion has less impact on melting properties than assumed so far. Within the case study, high CO2 abatement costs of 295 €/t CO2-eq. were determined. This is mainly due to the insufficient performance of renewable energy sources. The correlations between process scaling and economic parameters presented in this study show promising potential for further economic optimization of the proposed energy system in the future.

Thermal expansion, heat capacity and Gr�neisen parameter of grossular at high temperature and high pressure

The thermodynamic properties of grossular garnet (Ca3Al2Si3O12) were determined as a function of pressure and temperature in this study. With a numerical iterative procedure, the unit-cell volume, adiabatic bulk modulus, thermal expansion, heat capacity, and Gr�neisen parameters of grossular up to 25 GPa, 2000 K were extracted from experimental elastic wave velocities at high temperature and high pressure conditions. The calculated unit-cell volume and adiabatic bulk modulus agree well with the previous studies. The results imply that our calculated thermal expansion, heat capacity, and Gr�neisen parameters of grossular are all decrease with elevated pressure, and both thermal expansion and heat capacity show nonlinear pressure dependences. On the other hand, the Gr�neisen parameter shows a linear pressure dependence. The pressure derivative of thermal expansion display a regularity increase with temperature, while the pressure derivatives of heat capacity and Gr�neisen parameters display a rapid decrease at low temperature and a slow growth above ~1000 K.

Thermodynamic properties of 2–methylindole: Experimental and computational results for gas-phase entropy and enthalpy of formation

Abstract Measurements leading to the calculation of thermodynamic properties in the ideal-gas state for 2-methylindole (Chemical Abstracts registry number [95–20–5]) are reported. Experimental methods were adiabatic heat-capacity calorimetry, differential scanning calorimetry (d.s.c.), comparative ebulliometry, inclined-piston manometry, and oxygen bomb calorimetry. The critical temperature of 2-methylindole was determined experimentally with d.s.c. Molar thermodynamic functions for the condensed and ideal-gas states were derived from the experimental results. Statistical calculations were performed based on molecular geometry optimization and vibrational frequencies using B3LYP hybrid density functional theory with the def2-TZVPPD basis set. Excellent accord between computed and experimentally-derived ideal-gas entropies is shown. The enthalpy of formation for 2-methylindole in the gas phase was computed with an atomization-based protocol described recently, and excellent agreement with the experimental values is seen. The experimental literature for enthalpies of formation in the gas phase for 1- and 2-ring pyrrollic compounds is reviewed, and comparisons with computed values further support the findings here. All experimental results are compared with property values reported in the literature, where possible.

Measurements of the magnetic and magnetothermal properties of heavy rare earths

The adiabatic temperature change, magnetization, heat capacity and thermal conductivity coefficient of a set of commercial purity heavy rare earth metals were measured. The temperature and magnetic field dependences of the adiabatic temperature change and magnetization were measured by direct and induction methods, respectively, in dynamic mode closely corresponding to the operational conditions of working magnetic refrigerators. The temperature dependences of the heat capacity and thermal conductivity coefficient in a constant magnetic field were measured by adiabatic calorimetry and steady-state methods. The obtained experimental results were compared with the literature data on high-purity heavy rare earths magnetothermal properties. The possible effect of the material purity on magnetic refrigerators parameters and ability to use the commercial purity materials in such devices are discussed.

Heat capacity and thermodynamic functions of sphalerite: Implication to sulfide solid-state galvanic cell measurements

New adiabatic calorimeter measurements of heat capacity of sphalerite from 13.23 to 312.85K at ambient pressure agree well with previous adiabatic calorimeter results but overestimate PPMS-derived data (Cardona et al., 2010) at T>150K. The adiabatic calorimeter low-temperature heat capacity data and drop-calorimetric high-temperature data on H0(Т)−H0(298.15) are rationalized in the framework of the Kieffer-type vibrational spectrum model accounting for dependence of vibrational frequencies on volume and temperature. Thermodynamic properties of sphalerite are calculated by the elaborated model from 0 to 1300K.Present calorimetric results conform to those from high-temperature electromotive force (EMF) experiments (Osadchii et al., 2015) using the Cu/Cu2S buffer. The disagreement with data based the Ag/Ag2S buffer is explained by deviation of silver sulfide from stoichiometry in the EMF experiments. A correction to the Gibbs energy of formation obtained in high-temperature EMF experiments using the Ag/Ag2S buffer is suggested.

ACTIVATION ENERGY OF REARRANGEMENTS CLUSTER STRUCTURES OF WATER

Despite intensive research on the structure and molecular dynamics of liquid water is still not known thermodynamic mechanism of differentiation of the extreme points of the temperature dependences of the properties of water. In the present work studied the anomalous temperature dependencies, by using the method of linear approximations. Estimated temperature gradient and the activation energy for each dependency and compared them with the energy of hydrogen bonds and energies of their own and cooperative motions of water molecules in clusters. Found that the reaction rupture of hydrogen bonds limit mainly thermodynamics anomalies dynamic viscosity, self-diffusion and conductivity of water. Thermodynamics cooperative and resonance effects in the cluster structures is the basis of density anomalies, adiabatic heat capacity, speed of sound, surface tension and compressibility. Almost all linear approximation had a fracture in the area of 25 °C. Given the known data suggested that at this point, a phase transition occurs between States of water with varying degrees of helicity of hydrogen bonds.

Thermodynamic properties of indan: Experimental and computational results

Measurements leading to the calculation of thermodynamic properties in the ideal-gas state for indan (Chemical Abstracts registry number [496-11-7], 2,3-dihydro-1H-indene) are reported. Experimental methods were adiabatic heat-capacity calorimetry, differential scanning calorimetry, comparative ebulliometry, and vibrating-tube densitometry. Molar thermodynamic functions (enthalpies, entropies, and Gibbs energies) for the condensed and ideal-gas states were derived from the experimental studies at selected temperatures. Statistical calculations were performed based on molecular geometry optimization and vibrational frequencies calculated at the B3LYP/6-31+G(d,p) level of theory. Computed ideal-gas properties derived with the rigid-rotor harmonic-oscillator approximation are shown to be in excellent accord with ideal-gas entropies derived from thermophysical property measurements of this research, as well as with experimental heat capacities for the ideal-gas state reported in the literature. Literature spectroscopic studies and ab initio calculations report a range of values for the barrier to ring puckering. Results of the present work are consistent with a large barrier that allows use of the rigid-rotor harmonic-oscillator approximation for ideal-gas entropy and heat-capacity calculations, even with the stringent uncertainty requirements imposed by the calorimetric and physical property measurements reported here. All experimental results are compared with property values reported in the literature.

Thermodynamic properties of 1-phenylnaphthalene and 2-phenylnaphthalene

Measurements leading to the calculation of thermodynamic properties in the ideal-gas state for 1-phenylnaphthalene (Chemical Abstracts registry number [605-02-7]) and 2-phenylnaphthalene (Chemical Abstracts registry number [612-94-2]) are reported. Experimental methods for 1-phenylnaphthalene were adiabatic heat-capacity calorimetry, differential scanning calorimetry, inclined-piston manometry, comparative ebulliometry, vibrating-tube densitometry, and combustion calorimetry. For 2-phenylnaphthalene, the experimental methods were adiabatic heat-capacity calorimetry, differential scanning calorimetry, and comparative ebulliometry. Critical properties were estimated for both compounds. Molar thermodynamic functions (enthalpies, entropies, and Gibbs free energies) for the condensed and ideal-gas states were derived from the experimental studies at selected temperatures. Statistical calculations were performed based on molecular geometry optimization and vibrational frequencies calculated at the B3LYP/6-31+G(d,p) and B3LYP/cc-pVTZ levels of theory. Ideal-gas entropies derived with two the independent methods are shown to be in good accord for 1-phenylnaphthalene, but significant differences are apparent for 2-phenylnaphthalene. These differences are likely due to a disorder of unknown type in the crystals of 2-phenylnaphthalene at low temperatures, as evidenced by the presence of a glass-like transition in the measured heat capacities for the solid state. All experimental results are compared with property values reported in the literature.

Adiabatic heat capacity and related properties of ammonium hexachlororuthenate, (NH4)2RuCl6, at temperatures from 5 ⩽ T/K ⩽ 325

The heat capacity of ammonium hexachlororuthenate, (NH4)2RuCl6, was measured over the temperature range 5⩽T/K⩽325 using adiabatic calorimetry. Our results show that a structural phase transition is not present. However, an anomalous increase in the heat capacity Cp,m occurs in the region 70⩽T/K⩽105 and the heat capacity reaches its maximum at T=(93.5±0.1) K. The molar entropy change associated with this increase amounts to ΔSm=(0.465±0.006)R. Standard molar thermodynamic functions are presented at selected temperatures from 5K to 325K.

The maximal cooling power of magnetic and thermoelectric refrigerators with La(FeCoSi)13 alloys

Using our data on magnetic entropy change ΔSm, adiabatic temperature change ΔTad and heat capacity CH for La(FeCoSi)13 alloys, the upper limit of heat Qc transferred per cycle, and the lowest limit of consumed work Wc were established for magnetic refrigerators operating in Δμ0H=1.9 T. In order to estimate the cooling power, attributable to thermoelectric refrigerators with La(FeCoSi)13, thermal conductivity λ, resistivity ρ, and Seebeck coefficient α were measured and the maximal cooling power QL, the input power Pi, and coefficient of performance have been calculated.

Thermodynamic properties of 9-fluorenone: Mutual validation of experimental and computational results

Measurements leading to the calculation of thermodynamic properties for 9-fluorenone (IUPAC name 9H-fluoren-9-one and Chemical Abstracts registry number [486-25-9]) in the ideal-gas state are reported. Experimental methods were adiabatic heat-capacity calorimetry, inclined-piston manometry, comparative ebulliometry, and combustion calorimetry. Critical properties were estimated. Molar entropies for the ideal-gas state were derived from the experimental studies at selected temperatures T between T=298.15K and T=600K, and independent statistical calculations were performed based on molecular geometry optimization and vibrational frequencies calculated at the B3LYP/6−31+G(d,p) level of theory. Values derived with the independent methods are shown to be in excellent accord with a scaling factor of 0.975 applied to the calculated frequencies. This same scaling factor was successfully applied in the analysis of results for other polycyclic molecules, as described in recent articles by this research group. All experimental results are compared with property values reported in the literature. Thermodynamic consistency between properties is used to show that several studies in the literature are erroneous.

Thermodynamic properties of three-ring aza-aromatics. 2. Experimental results for 1,10-phenanthroline, phenanthridine, and 7,8-benzoquinoline, and mutual validation of experiments and computational methods

Measurements leading to the calculation of standard entropies for 1,10-phenanthroline (Chemical Abstracts registry number [66-71-7]) in the crystal, liquid, and ideal-gas state are reported. Experimental methods were adiabatic heat-capacity calorimetry and comparative ebulliometry. Thermodynamic properties for phenanthridine [229-87-8] and 7,8-benzoquinoline [230-27-3] were reported previously and included those measured with adiabatic heat-capacity calorimetry, comparative ebulliometry (7,8-benzoquinoline only), inclined-piston manometry, and combustion calorimetry. New measurement results for phenanthridine and 7,8-benzoquinoline reported here are densities determined with a vibrating-tube densimeter and heat capacities for the liquid phase at saturation pressure determined with a differential scanning calorimeter (dsc), and vapor pressures by comparative ebulliometry (phenanthridine only). All critical properties were estimated. Molar entropies for the ideal-gas state were derived for all compounds at selected temperatures. Independent calculations of entropies for the ideal-gas state were performed at the B3LYP/6-31+G(d,p) model chemistry for the three compounds studied. These are shown to be in excellent accord with the calorimetric results for 1,10-phenanthroline and phenanthridine. Results for 7,8-benzoquinoline indicate that the crystal state is disordered. All new experimental results are compared with property values reported in the literature.

Thermodynamic properties of three-ring aza-aromatics. 1. Experimental results for phenazine and acridine, and mutual validation of experiments and computational methods

Measurements leading to the calculation of thermodynamic properties for phenazine (Chemical Abstracts registry number [92-82-0]) in the ideal-gas state are reported. Experimental methods included adiabatic heat-capacity calorimetry, inclined-piston manometry, and combustion calorimetry. Thermodynamic properties for acridine (Chemical Abstracts registry number [260-94-6]) were reported previously and included those measured with adiabatic heat-capacity calorimetry, comparative ebulliometry, inclined-piston manometry, and combustion calorimetry. New measurement results for acridine reported here are densities determined with a vibrating-tube densimeter and heat capacities for the liquid phase at saturation pressure determined with a differential-scanning calorimeter (d.s.c.). All critical properties were estimated. Molar entropies for the ideal-gas state were derived for both compounds at selected temperatures. Independent calculations of entropies for the ideal-gas state were performed at the B3LYP/6-31+G(d, p) model chemistry for phenazine and acridine. These are shown to be in excellent accord with the calorimetric results. All results are compared with experimental property values reported in the literature.

Development of a Small Scale Adiabatic Calorimeter (Room Temperature to 600°C) and Heat Capacity Measurement of Synthetic Cu3BiS3

Development of a Small Scale Adiabatic Calorimeter (Room Temperature to 600°C) and Heat Capacity Measurement of Synthetic Cu3BiS3

Thermodynamic Relationship between Structural Isomers of the Thermochromic Compound Bis(N-Isopropyl-5,6-benzosalicylideneiminato)nickel(II)

A pair of structural isomers was isolated at room temperature for the thermochromic nickel complex bis( N-isopropyl-5,6-benzosalicylideneiminato)nickel(II); one is a diamagnetic green form with square-planar coordination geometry (G phase), and the other is a paramagnetic brown form with a tetrahedral geometry (B phase). However, a question as to which form is thermodynamically stable was left open. To solve this problem, thermal and magnetic properties of this complex were investigated by adiabatic heat capacity calorimetry in the 6-508 K temperature range and magnetic measurements in the 2-400 K region. In addition to the two forms previously reported, two metastable crystal forms (G' and B' phases) were found. The stable phase sequence was G phase, B phase, and then liquid upon heating. The supercooled B phase gave rise to a small phase transition with nonmagnetic origin at around 50 K. By rapidly cooling the liquid, a glassy liquid state was realized below approximately 290 K. The order of thermodynamic stability at 298.15 K was revealed to be the G, B, G', and then the B' phase. The entropy, enthalpy, and Gibbs energy differences between the B and the G phases at 298.15 K were S degrees (B) - S degrees (G) = 32.8 J K (-1) mol (-1), H degrees (B) - H degrees (G) = 16.0 kJ mol (-1), and G degrees (B) - G degrees (G) = 6.25 kJ mol (-1), respectively.

Thermodynamic properties of 1,2-dihydronaphthalene: Glassy crystals and missing entropy

Measurements leading to the calculation of the standard thermodynamic properties for gaseous 1,2-dihydronaphthalene (Chemical Abstracts registry number [447-53-0]) are reported. Experimental methods include oxygen combustion-bomb calorimetry, adiabatic heat-capacity calorimetry, vibrating-tube densitometry, comparative ebulliometry, and inclined-piston gauge manometry. 1,2-Dihydronaphthalene decomposed significantly when heated to temperatures above T = 480 K. Consequently, the critical temperature, critical pressure, and critical density were estimated. Standard molar entropies, standard molar enthalpies, and standard molar Gibbs free energies of formation were derived at selected temperatures between T = 250 K and 500 K. The standard state is defined as the ideal gas at the pressure p = p ∘ = 101.325 kPa. Standard entropies are compared with those calculated statistically on the basis of assigned vibrational spectra from the literature for the vapor phase. A large and near constant difference between the entropies calculated statistically and those determined calorimetrically was observed over the entire temperature range studied. Two glass-like features are observed in the heat capacity against temperature curve for the solid state, indicating that the crystals are disordered. A quantitative accounting for the entropy discrepancy is proposed based on possible molecular orientations of 1,2-dihydronaphthalene. Results are compared with experimental values reported in the literature.

Spin Crossover Phenomenon Accompanying Order−Disorder Phase Transition in the Ligand of [FeII(DAPP)(abpt)](ClO4)2Compound (DAPP = Bis(3-aminopropyl)(2-pyridylmethyl)amine, abpt = 4-Amino-3,5-bis(pyridin-2-yl)-1,2,4-triazole) and Its Successive Self-Grinding Effect

The spin crossover phenomenon of the recently described spin crossover complex [FeII(DAPP)(abpt)](ClO4)2 [DAPP = bis(3-aminopropyl)(2-pyridylmethyl)amine, abpt = 4-amino-3,5-bis(pyridin-2-yl)-1,2,4-triazole] accompanying an order-disorder phase transition of the ligand was investigated by adiabatic heat capacity calorimetry, far-IR, IR, and Raman spectroscopies, and normal vibrational mode calculation. A large heat capacity peak due to the spin crossover transition was observed at T(trs) = 185.61 K. The transition enthalpy and entropy amounted to Delta(trs)H = 15.44 kJ mol-1 and Delta(trs)S = 83.74 J K-1 mol-1, respectively. The transition entropy is larger than the expected value 60.66 J K-1 mol-1, which is contributed from the spin multiplicity (R ln 5; R: the gas constant), disordering of the carbon atom of the six-membered metallocycle in the DAPP ligand, and one of the two perchlorate anions (2R ln 2), and change of the normal vibrational modes between the high-spin (HS) and low-spin (LS) states (35.75 J K-1 mol-1). The remaining entropy would be ascribed to changes of the lattice vibrations and molecular librations between the HS and LS states. Furthermore, [Fe(DAPP)(abpt)](ClO4)2 crystals disintegrated and became smaller crystallites whenever they experienced the phase transition. This may be regarded as a successive self-grinding effect, evidenced by adiabatic calorimetry, DSC, magnetic susceptibility, and microscope observation. The relationship between the crystal size and the physical quantities is discussed.

Thermodynamic properties of methylquinolines: Experimental results for 2,6-dimethylquinoline and mutual validation between experiments and computational methods for methylquinolines

Measurements leading to the calculation of the standard thermodynamic properties for gaseous 2,6-dimethylquinoline (Chemical Abstracts registry number [877-43-0]) are reported. Experimental methods included adiabatic heat-capacity calorimetry, vibrating-tube densimetry, comparative ebulliometry, inclined-piston gauge manometry, differential-scanning calorimetry (d.s.c.), and combustion calorimetry. The critical temperature was measured with d.s.c. The critical pressure and critical density were estimated. Molar entropies, molar enthalpies, and molar Gibbs free energies of formation for the ideal gas state were derived at selected temperatures between 298.15 K and 700 K. Results are compared with experimental property values reported previously in the literature. Independent calculations of the ideal gas entropies were performed at the B3LYP/6-31+G(d,p) model chemistry for 2,6-dimethylquinoline and other methylquinolines (including hindered internal rotations) and are shown to be in excellent accord with the calorimetric results. Implications of these results are discussed.

Calorimetry of nanoparticles, surfaces, interfaces, thin films, and multilayers

Calorimetry gives insight into the stability of nanophase materials. Using TiO 2 as an example, the interplay of energetics of polymorphism, surface energy, and surface hydration is discussed. Oxide melt solution calorimetry, water adsorption calorimetry, and adiabatic heat capacity studies together show the following. The metastability of bulk polymorphs increases in the order rutile, brookite, anatase, while the surface energy increases in the opposite order. This leads to crossovers in phase stability at the nanoscale, which appears to be a general phenomenon. Hydration plays a major role in stabilizing nanoparticles and the first layers of water are tightly bound. There is little excess heat capacity and no significant excess vibrational entropy in nanophase rutile or anatase. Further applications of calorimetry to thin films, interfaces, multilayers, and sub-milligram samples are presented.