Thermodynamic Properties Research Articles

First principles investigation for the hydrogen storage properties of novel lithium-based XLiH3 (X=K, Rb) perovskite-type hydrides for advance hydrogen storage system

In this work, the density functional theory is used to investigate the structural, mechanical, electronic, dynamic, thermodynamic, optical and hydrogen storage properties of XLiH3 (X=K, Rb) for the first time. Both KLiH3 and RbLiH3 materials exhibit dynamic, mechanical and thermodynamic stability. The lattice parameters of KLiH3 and RbLiH3 are 3.908 and 4.070 Å, respectively. The investigation of Cauchy pressure, Poisson's ratio and B/G ratio shows that KLiH3 and RbLiH3 are brittle materials. Moreover, the electronic properties of XLiH3 hydrides demonstrate that KLiH3 and RbLiH3 show metallic nature. Optical properties of these compounds are studied and reveal that they have very high refractive indexes and dielectric functions. The thermodynamic properties, including heat capacity, entropy, enthalpy, and free energy of XLiH3, are investigated as well. The hydrogen storage capacities of KLiH3 and RbLiH3 are 5.805 and 3.071 wt%, respectively, confirming that KLiH3 has a high hydrogen storage capacity and is more suitable as a hydrogen storage material. Our study opens up a new-pathway for designing novel hydrogen storage materials.

Environmentally friendly production of petroleum systems with high CO2 content

Natural gas hydrates represents a huge source of energy. At the same time substantial leakages of natural gas from hydrates contributes significantly to climate changes. One of the most important reasons for these natural gas fluxes is leakage of seawater in to the hydrates from seafloor, through fracture systems. Hydrate dissociates if surrounding seawater is less than hydrate stability limit. Another interesting aspect of natural gas hydrates is the potential for safe CO2 storage. These different aspects of hydrates in natural sediments put demands on thermodynamic models. In addition to accurate description of pressure temperature hydrate stability there also a need to describe hydrate dissociation in concentration gradients towards surrounding water or surrounding gas as two examples. In this work we present new experimental data and an extensive thermodynamic model for hydrate. In contrast to conventional thermodynamic models for hydrate the model is consistent since all thermodynamic properties are derived from the Gibbs free energy. In this work we examine mixtures of CH4, C2H6, N2, CO2 from the China Sea and some synthetic mixtures, using this model. Maximum CO2 content in these mixtures are 60 mol% and the rest is dominated by CH4. Agreement between experimental data and model calculations are generally good and average deviations are below 5.5% for all the systems and conditions examined. Another aspect of the model is the ability for incorporation of effects of mineral surfaces. Specifically it is illustrated that adsorption of water on rust dominates liquid water drop out from gas as compared to water dew-point. Production of natural gas with such high CO2 content requires a strategy for CO2 separation and storage. It is proposed that the CH4 is separated from the C2H6, CO2 and N2 and cracked to H2 and CO2 using steam. Thermodynamic analysis indicates a significant potential for safe CO2 storage in natural gas hydrate and H2 as the only export product.

Stabilizing Effects of Higher-Order Quantum Corrections on Charged BTZ Black Hole Thermodynamics

In this paper, we study the thermodynamic properties and stability of static charged BTZ black holes with the inclusion of higher-order quantum corrections. The corrections to the entropy, mass, and Helmholtz free energy are derived, revealing the intricate interplay between quantum effects and classical gravitational forces in the context of black hole thermodynamics. The study of the specific heat capacity shows that higher-order corrections stabilize the system by removing the instabilities present at lower orders. The analysis of the van der Waals-like isotherms demonstrates the continuous transition from a highly compressible to an almost incompressible regime as the volume is decreased, akin to the behavior of supercritical fluids. Notably, the isotherms do not exhibit any regions of negative compressibility, indicating the absence of instabilities. Furthermore, the convexity of the Helmholtz free energy as a function of volume confirms the stability of the charged BTZ black hole system. These findings provide valuable insights into the complex thermodynamic landscape of three-dimensional black holes and the role of quantum corrections in shaping their behavior.

PRACTICAL SESSION USED FOR A DEEPER UNDERSTANDING OF VAPOUR COMPRESSION SYSTEMS – A PURPOSE OF TEACHING IN CONSTANTA MARITIME UNIVERSITY

In order to increase the knowledge of future marine engineers it is needed to bring closer the practical skills with theoretical gains. In Constanta Maritime University, Marine Refrigerating Plants is a discipline included in the curricula of future marine engineers. Practical learning can be also developed on low cost and effective means – as it will be proven in the paper. By using Coolselector 2, future marine engineers are trained to apply theoretical knowledge such as thermodynamics principles and to better understand the vapour compression cycle analysis, thermodynamic properties of refrigerants or the importance of the main components of a basic vapour compression refrigeration cycle. At the end of the practical session, students will gain important skills specific to theoretical aspects of refrigeration and thermodynamic processes and real situations.

Thermodynamic excess properties of the methyl tert-butyl ether + benzene + cyclohexane ternary system and its binary subsystems at temperature T = (293.15, 298.15, 303.15, and 313.15) K and ambient pressure

ABSTRACT This work reports for the first time, the experimental densities and sound speeds for the ternary system {methyl tert-butyl ether + benzene + cyclohexane} within the temperature range (293.15 to 313.15) K and under ambient pressure conditions. The related binary subsystems have also been reported. Experimental data were used to derive excess molar volumes and excess isentropic compressibilities. Redlich-Kister and Cibulka’s equations correlated the binary and ternary excess properties, respectively, with standard deviations falling below the estimated uncertainties of the corresponding properties. The results have been interpreted in terms of molecular interactions between mixtures’ components and structural effects. Additionally, two symmetric (Kohler and Muggianu) and two asymmetric (Hillert and Toop) binary contribution models have been tested for their ability to predict the excess properties of the ternary excess properties.

Microcanonical Monte Carlo of Lennard-Jones microclusters.

A novel statistical mechanical methodology is applied to clusters of N ≤ 7 atoms. Exact statistical analogs for any energy derivative of entropy ∂mS/∂Em are used in rigorous microcanonical Monte Carlo simulations to vastly enlarge the pool of measurable thermodynamic properties relative to previous work. All analogs are given for two alternative partition functions of the microcanonical ensemble. Coarse grained energy distributions are used to establish the existence of melting transitions. LJ7, LJ5, and LJ4 are found to exhibit trimodal distributions, a feature not being reported before. Varieties of combinations of entropy derivatives are tested for a direct detection of the melting region. It is shown that for such a purpose, derivatives of at least fourth order are necessary.

RASPA3: A Monte Carlo code for computing adsorption and diffusion in nanoporous materials and thermodynamics properties of fluids.

We present RASPA3, a molecular simulation code for computing adsorption and diffusion in nanoporous materials and thermodynamic and transport properties of fluids. It implements force field based classical Monte Carlo/molecular dynamics in various ensembles. In this article, we introduce the new additions and changes compared to RASPA2. RASPA3 is rewritten from the ground up in C++23 with speed and code readability in mind. Transition-matrix Monte Carlo is added to compute the density of states and free energies. The Monte Carlo code for rigid molecules is based on quaternions, and the atomic positions needed in the energy evaluation are recreated from the center of mass position and quaternion orientation. The expanded ensemble methodology for fractional molecules, with a scaling parameter λ between 0 and 1, now also keeps track of analytic expressions of dU/dλ, allowing independent verification of the chemical potential using thermodynamic integration. The source code is freely available under the MIT license on GitHub. Using this code, we compare four Monte Carlo (MC) insertion/deletion techniques: unbiased Metropolis MC, Configurational-Bias Monte Carlo (CBMC), Continuous Fractional Component MC (CFCMC), and CB/CFCMC. We compare particle distribution shapes, acceptance ratios, accuracy and speed of isotherm computation, enthalpies of adsorption, and chemical potentials, over a wide range of loadings and systems, for the grand canonical ensemble and for the Gibbs ensemble.

Observations of Kappa Distributions in Solar Energetic Protons and Derived Thermodynamic Properties

In this paper, we model the high-energy tail of observed solar energetic proton energy distributions with a kappa distribution function. We employ a technique for deriving the thermodynamic parameters of solar energetic proton populations measured by the Parker Solar Probe Integrated Science Investigation of the Sun EPI-Hi high-energy telescope, over energies from 10 to 60 MeV. With this technique, we explore, for the first time, the characteristic thermodynamic properties of the solar energetic protons associated with an interplanetary coronal mass ejection (ICME) and its driven shock. We find that: (1) the spectral index or, equivalently, the thermodynamic parameter kappa of solar energetic protons (κ EP) gradually increases, starting from the pre-ICME region (upstream of the CME-driven shock), reaching a maximum in the CME ejecta (κ EP ≈ 3.5), followed by a gradual decrease throughout the trailing portion of the CME; (2) the solar energetic proton temperature and density (T EP and n EP) appear anticorrelated, a behavior consistent with subisothermal polytropic processes; and (3) values of T EP and κ EP appear to be positively correlated, indicating an increasing entropy with time. Therefore, these proton populations are characterized by a complex and evolving thermodynamic behavior, consisting of multiple subisothermal polytropic processes, and a large-scale trend of increasing temperature, kappa, and entropy. This study and its companion study by Livadiotis et al. open up a new set of procedures for investigating the thermodynamic behavior of energetic particles and their shared thermal properties.

Computational insights into structural, electronic, optical and thermoelectric features of ternary chalcogenide Ca2GeX4 (X=S, Se, Te) compounds

The advancements in materials engineering for clean energy and greenhouse gas reduction has attracted global attention. Furthermore, the distinct electrical and optical properties of ternary chalcogenides are critical for their application in solar energy conversion. In this study, the electronic, optical, thermodynamic, and thermoelectric transport properties of the ternary chalcogenide Ca2GeX4 (X = S, Se, and Te) compounds are comprehensively investigated using the density functional theory-based WIEN2k package. The findings indicate that ternary chalcogenide Ca2GeX4 compounds possess substantial band gaps and display strong covalent bonding characteristics. Analysis of the density of states reveals minimal impact from S-s and S-p states, while highlighting the significance of Ca-s and Ge-s states. The investigated materials show significant UV absorption with reflectance between 30 and 40 % which peaks at 13.5 eV at about 65 %, confirming the optical properties of the ternary chalcogenide Ca2GeX4. The positive Seebeck coefficient suggests that holes are the primary charge carriers in tested materials, with thermal energy rising in accordance with the chalcogenide's atomic number. Several thermoelectric properties that demonstrate the suitability of these materials for thermoelectric applications were also discussed. Overall, the findings confirm the thermoelectric and optoelectronic properties of Ca2GeX4 materials, which may facilitate the creation and development of effective optoelectronic devices.

Retraction Note: Electronic, thermodynamic, optical, and thermoelectric properties of Sr2RuO4 compound: Ab-initio principle

Retraction Note: Electronic, thermodynamic, optical, and thermoelectric properties of Sr2RuO4 compound: Ab-initio principle

Ionic liquids based azeotropic separation of refrigerants R410A (R32+R125) and R508B (R23+R116) through hybrid extractive distillation

ABSTRACT The increment in GreenHouse Gases (GHGs) promotes high Global Warming Potential (GWP) due to the production and consumption of hydrofluorocarbons (HFCs) that diverts the aim toward the recycling and reclaiming of refrigerant gases. However, the presence of azeotrope in refrigerant mixtures restricts the recycling process. Therefore, in this work, the refrigerant R410A and R508B have been separated through the hybrid extractive distillation method by using [HMIM][TF2N] and [BMIM][BF4] as a solvent in ASPEN Plus. UNIFAC model has been used for the correlation of ionic liquid in ASPEN Plus. For thermodynamic properties, Cosmotherm has been used with the collaboration of TurbromoleX. The Vapor-liquid Equilibrium (VLE) data has been predicted by using the UNIFAC group contribution method. The Total Annual Cost (TAC) analysis with optimization has been performed. Besides that, the energy analysis has also been performed. In the overall separation process and (TAC) analysis, [BMIM][BF4] proves to be more efficient with high separation efficiency and minimal TAC requirements. Whereas, [HMIM][TF2N]/R508B provides less CO2 emission.

Ab-initio investigation of the structural, mechanical, electronic, thermodynamic and optical properties of V2FeNiGe2 and Hf2FeNiSb2 double half-Heusler compounds

In the present work, using ab-initio density-functional theory methods based on the Quantum ESPRESSO package, we have investigated the structural, elastic, electronic and optical properties of 18–electron V2FeNiGe2 and Hf2FeNiSb2 double half-Heusler alloys. The calculated elastic properties suggest a ductile behavior with metallic bonding for V2FeNiGe2 and a brittle behavior with covalent bonding for Hf2FeNiSb2. The thermodynamic properties (Debye temperature, melting temperature) are also predicted and discussed for the studied alloys. The alloys are found to be semiconducting with indirect band gaps of 0.53eV for V2FeNiGe2 and 0.47eV for Hf2FeNiSb2. We also computed and analyzed their optical properties (dielectric function, optical conductivity, refractive index, absorption index and reflectance) and our calculations suggest that both materials have high absorption coefficient and optical conductivity in the UV as well as visible region. The results make them potential candidates for the manufacture of opto-electronic devices.

Investigation of microstructure, hydrogen storage performance of Re-Mg-based alloy modified by RE2O3 (RE = Dy, Er, Yb)

In order to further study the hydrogen storage mechanism of Mg-based hydrogen storage materials, Mg90Ce5Y5 alloy was used as the basis, and three kinds of heavy rare earth oxides were doped into the alloy by ball milling technology. The microstructure and hydrogen storage properties were characterized by XRD, SEM, TEM and PCI. The results show that the hydrogen absorption rate and discharge rate of modified Mg90Ce5Y5 alloy are significantly increased, and the performance is Er2O3 > Dy2O3 > Yb2O3. The hydrogen storage capacity of Er2O3 catalyzed samples is 5.02 wt%, which is higher than 4.82 wt% and 4.80 wt% of Dy2O3 and Yb2O3 catalyzed samples. The hydrogen absorption saturation rate of the sample catalyzed by Er2O3 for 2 min is ∼90 %, the complete release of hydrogen only takes 50 min at 573 K, and the dehydrogenation activation energy is 76.9 kJ/mol. The hydrogen absorption and emission rate is fast, and the dehydrogenation activation energy is slightly lower than that of the other two catalysts. In the process of hydrogen absorption and desorption, the three catalysts exhibit different phase transitions, namely DyH2↔DyH3, ErH2↔ErH3 and irreversible YbH2. DyH2↔DyH3, ErH2↔ErH3 phase transitions have the "hydrogen pump" effect, which can effectively improve the hydrogen absorption and desorption kinetic rate of Mg90Ce5Y5 alloy. Some nano-rare earth compounds and phase transformation significantly improve the kinetic properties of the alloy. However, the enthalpy change of all three catalytic alloys is around 76 kJ/mol H2, which is considered only a slight improvement in thermodynamic properties.

Unraveling Superior Elasticity and Controlled Thermal Expansion in Trigonal MBO3 (M=Al, Ga) with Isolated [BO3] Group: A Theoretical Perspective

AbstractA comprehensive theoretical investigation employing density functional theory explores the electronic structure, temperature‐dependent elasticity, thermodynamic properties, and chemical bonding of trigonal MBO3 (M=Al, Ga) with isolated [BO3] groups. The results uncover MBO3 (M=Al, Ga) as indirect semiconductors with superior mechanical stability, characterized by greater resistance to volume compression over shear deformation. Their elasticity exhibits relatively weak temperature dependence, suggesting excellent thermal stability. Thermodynamic analysis predicts that GaBO3 has a higher thermal expansion coefficient than AlBO3, approximately 2.1×10−5 K−1 and 1.8×10−5 K−1 at 300 K, respectively. Significantly, the overall thermal expansion coefficients of GaBO3 and AlBO3 are lower compared to other borate materials containing isolated [BO3] groups. Chemical bonding insights reveal that GaBO3′s larger thermal expansion is attributed to its larger atomic displacement parameters and weaker Ga−O bond strength. This research positions MBO3 (M=Al, Ga) as prime candidates for optical device applications due to their well‐characterized elasticity and controlled thermal expansion.

Insights into catalytic co-pyrolysis of spent coffee grounds and high density polyethylene (HDPE) using acid mine drainage (AMD) treated sludge based catalyst: Analysis of kinetics, mechanism and thermodynamic properties

The present study aims to investigate the catalytic effect of acid mine drainage (AMD) treated sludge based catalyst on the co-pyrolysis of spent coffee grounds and HDPE. The sludge was generated during the treatment of AMD using eggshell and hydrogen peroxide. Theromogravimetric analysis of pyrolysis of spent coffee grounds (SC), HDPE (High density polyethylene), blend of spent coffee grounds and HDPE (SC+HDPE) in the ratio of 1:1, and blended feedstock with sludge derived catalyst (SC+HDPE_AMDC) (1:1 wt. ratio) was conducted at various heating rates of 10 °C/min, 20 °C/min, 30 °C/min and 40 °C/min respectively. Iso-conversional models such as Ozawa Flynn Wall (OFW), Kissinger Akahira Sunose (KAS), Friedman, and Starink were utilized for the determination of activation energy (Ea) of the process. The results showed that using AMD treated sludge based catalyst to the pyrolysis process, enhances its overall efficacy by lowering the activation energy (Ea) (OFW- Ea: 209.11 to 177.14 KJ/mol, KAS-Ea: 208.30 to 173.06 KJ/mol, Friedman- Ea:210.54 to 176.28 KJ/mol, and Starink- Ea:208.60 to 173.44 KJ/mol). Criado's z-master plot (CZMP) method was utilized to analyze the mechanism of the reaction. The pre-exponential factor and thermodynamic parameters were also evaluated. It is concluded that the incorporation of sludge based catalyst (AMDC) lowered enthalpy and randomness of system. Catalytic co-pyrolysis requires less energy, making it more environmental friendly choice for the sustainable processing of biomass and plastics. The present investigation will aid in the design, optimization and scalability.

A consistent model of the initiation, early expansion, and possible extinction of a spark-ignited flame kernel

Modelling the establishment and growth of spark-ignited (SI) flame kernels has always been a topic of great interest, especially due to their key role in affecting the performance of SI engines. A major issue is that the unsteady conditions and the small kernel size hinder the application of the typical (both linear and non-linear) flame stretch correlations, valid only long after the ignition stage. Overcoming such limitations, this work presents a novel, mathematically consistent, and compact model that enables prediction of flame kernel initiation and early expansion, including its possible extinction. Firstly, spark-driven initiation models from literature are discussed, and an effective flame kernel initiation method is proposed. Then, the expansion model is defined complementing the mass, energy, and species conservation equations for the spherical kernel with the reactant and temperature profiles outside of it using the theory of transient thermodiffusive flames. After accounting for the convective flow caused by the combustion-induced density reduction and the variable thermodynamic properties of the reacting fuel/air mixture, the result is a two-equation model that predicts the kernel expansion even up to its possible extinction due to flame stretch. After calibration of the expansion model, successful validation is achieved against literature data on lean propane/air flames, and the influence of the model parameters is examined in detail. The proposed expansion model is formulated also aiming for inclusion into the simulation of combustion in SI engines, enabling more accurate predictions at part loads, as well as more effective estimation of the cycle-to-cycle variation thanks to the good model sensitivity to the parameters most affecting the ignition.

Composition driven machine learning for unearthing high-strength lightweight multi-principal element alloys

High-strength, lightweight alloys are highly desired in the aerospace, automotive and marine industries. The optimization of such alloys is a multifaceted process, characterized by the consideration of diverse objectives and constraints. Various optimization methodologies exist, spanning from intricate first-principle approaches to the application of sophisticated machine learning algorithms. These algorithms might incorporate input features encompassing elemental composition, microstructural attributes, and thermodynamic properties to enhance prediction accuracies. In this work, we aim to streamline this complexity by employing solely the alloy's elemental composition as the input feature for the machine learning algorithm, improving the hardness while reducing the density of the alloy. We have curated a comprehensive database comprising 544 multi-principal element alloys and developed a robust surrogate model based on these compositions. This composition-driven model is subsequently coupled with principal component analysis (PCA) to facilitate the selection process. Remarkably, through a mere three iterations involving 14 samples, we successfully identified an alloy with an effective specific hardness surpassing the training database maximum by 8.6 %. The proposed composition-driven machine learning delineates a simplified approach for conducting optimization across multiple target material properties.

Analysis of Corrosion Potential of Zn, Ni, and Zn-Ni Alloy Using Ab Initio Calculations Supported by Experimental Thermodynamics Data

Abstract The purpose of this study is to investigate the corrosion properties of Zn, Ni, and Zn-Ni alloy using density functional theory (DFT). DFT can assist in predicting the thermodynamic properties of challenging compounds such as metals, alloys, and transition metal oxides. In the present work, DFT is used to predict Zn, Ni, and Zn-Ni alloy phase diagram. The Hubbard correction (U) and dispersion correction (D) are used to minimize the inherent error associated with the DFT. We studied the crystal structure, electronic structures, and thermodynamic energies of Zn and Ni compounds using the generalized gradient approximation (GGA) density functional employing Perdew Burke Ernzerhof (PBE). We have developed the corresponding Pourbaix diagram of Zn, Ni, and their alloy to compare the performance of density functional theory with the experimental observations. The corrosion behavior of various alloys including ZN11, NI2, ZnNi, ZNNi3 are compared and discussed. This can be useful for predicting the corrosion-resistant properties of these alloys.

Investigation of Thermodynamic Properties and Stability of Metal Oxide (CuO and Al2O3)/Deionized Water Nanofluids for Enhanced Heat Transfer Applications

The potential of nanofluids in improving heat transfer efficiency is well recognized, although there is a lack of clarity regarding the methods for assessing their stability and the influence on thermophysical properties. Moreover, the prevention of nanoparticle aggregation, which is essential for stability, requires further investigation. This study aims to address these issues by investigating the thermodynamic properties and stability of Al2O3/deionized water and CuO/deionized water nanofluids, which were prepared using magnetic stirring and ultrasonication. The stability assessment, conducted through standard deviation analysis, revealed that CuO (80 nm)/deionized water nanofluids exhibited greater stability compared to Al2O3 (80 nm)/deionized water nanofluids. The research explored the impact of temperature, volume concentration, and nanoparticle type under both static and dynamic conditions. Static tests focused on measuring thermal conductivity, viscosity, and specific heat, while dynamic tests involved a heat exchanger setup to determine heat transfer rates. The findings indicated that CuO nanofluids displayed the highest thermal conductivity and the most significant reduction in specific heat and heat transfer rate. Viscosity was found to increase with nanoparticle concentration and decrease with temperature. This study provides valuable insights into the thermophysical characteristics and stability of nanofluids, emphasizing the advantages of CuO-based nanofluids for heat transfer applications.

Synthesis and Thermodynamic Properties of Thulium Titanate

Synthesis and Thermodynamic Properties of Thulium Titanate