Foundations Of Thermodynamics Research Articles

The formation mechanism of eutectic microstructures in NiAl-Cr composites.

NiAl-based eutectic alloys, consisting of an ordered bcc matrix (B2) and disordered bcc fibers (A2), have been a subject of intensive efforts aimed at tailoring the properties of many of the currently used nickel-based superalloys. A thermodynamic phase field model was developed on a thermodynamic foundation and fully integrated with a thermo-kinetic database of the Ni-Al-Cr ternary system to elucidate the resulting peculiar eutectic microstructure. Invoking a variation of the liquid/solid interfacial thickness with temperature, we simulated the characteristic sunflower-like eutectic microstructures in the NiAl-Cr composites, consistent with experimental observations. The mechanism that governs the formation of the peculiar eutectic morphology was envisioned from the modeled evolutions associated with six sequential steps. Our calculations show that the conditional spinodal decomposition occurring in sequence could further trim and revise the microstructure of the eutectics by generating fine-domain structures, thereby providing an additional method to explore the novel NiAl-based eutectic composites with tunable properties at elevated temperatures.

On the equivalence of storage functions in controlled thermodynamic systems

Motivated by thermodynamic concepts strongly related to the second law of thermodynamics, this paper deals with the mathematical foundations of thermodynamics to reconstruct some storage functions usable both for the stability analysis and control of homogeneous chemical processes through the case study of non isothermal continuous stirred tank reactors (CSTRs). Besides, the equivalence of the storage functions in the thermodynamics framework is also shown.

Nonergodic metallic and insulating phases of Josephson junction chains

Strictly speaking, the laws of the conventional statistical physics, based on the equipartition postulate [Gibbs J W (1902) Elementary Principles in Statistical Mechanics, developed with especial reference to the rational foundation of thermodynamics] and ergodicity hypothesis [Boltzmann L (1964) Lectures on Gas Theory], apply only in the presence of a heat bath. Until recently this restriction was believed to be not important for real physical systems because a weak coupling to the bath was assumed to be sufficient. However, this belief was not examined seriously until recently when the progress in both quantum gases and solid-state coherent quantum devices allowed one to study the systems with dramatically reduced coupling to the bath. To describe such systems properly one should revisit the very foundations of statistical mechanics. We examine this general problem for the case of the Josephson junction chain that can be implemented in the laboratory and show that it displays a novel high-temperature nonergodic phase with finite resistance. With further increase of the temperature the system undergoes a transition to the fully localized state characterized by infinite resistance and exponentially long relaxation.

Adsorption and catalysis for sustainable energy applications

This review addresses adsorption and catalytic thermochemical energy conversion (TEC) methods used to recover waste heat resulting from the combustion of primary organic fuels (oil, gas, and coal). We will consider the thermodynamic foundations of these methods, promising reactions and sorbents, the history and current state of the art in the R&D and practical implementation of TEC technologies, modern trends in TEC, and the ways of enhancing the TEC efficiency and specific power. Further progress in adsorption and catalytic TEC methods could provide a reliable base for the sustainable world energy sector.

Thermodynamic Foundations for the Analysis of Processes of Compression and Expansion in a Positive-Displacement Pump

Using the first law of thermodynamics of a medium of variable mass, the equation of conservation of mass, and the differential relations of thermodynamics, a unified system of equations is developed by means of which analyses of the working processes of positive-displacement compressors and pumps that take into account thermal, deformational, and mass-exchange interactions may be conducted.

Reactions of FeCr alloys with liquid zinc in hot-dip galvanizing

This study investigates reactions of FeCr alloys (containing 5, 30, 70 and 95at.% Cr) with liquid zinc for annealing times up to 1224h. Simple layered structure was observed at interfaces of Fe–5Cr/Zn and Fe–95Cr/Zn. However, alternating layers were found at interfaces of Fe–30Cr/Zn and Fe–70Cr/Zn. Thickness of the alternating layers varies linearly with square root of time, indicating that growth kinetic of the alternating layers is a diffusion controlled process. Periodic thermodynamic instability at the Fe–30Cr/(Cr) or Fe–70Cr/(Cr) interface causes the subsequent nucleation of new alternating layer pairs. The thermodynamic foundation and mechanism of formation of the alternating layers are elaborated in this paper.

Meaning and Measurability of Single-Ion Activities, the Thermodynamic Foundations of pH, and the Gibbs Free Energy for the Transfer of Ions between Dissimilar Materials.

Considering the relationship between concentration and vapor pressure (or the relationship between concentration and fugacity) single-ion activity coefficients are definable in purely thermodynamic terms. The measurement process involves measuring a contact potential between a solution and an external electrode. Contact potentials are measurable by using thermodynamically reversible processes. Extrapolation of an equation to zero concentration and ionic strength enables determination of single-ion activity coefficients. Single-ion activities can be defined and measured without using any extra-thermodynamic assumptions, concepts, or measurements. This method could serve as a gold standard for the validation of extra-thermodynamic methods for determining single-ion activities. Furthermore, it places the concept of pH on a thermodynamically solid foundation. Contact potential measurements can also be used to determine the Gibbs free energy for the transfer of ions between dissimilar materials.

A Novel Sequence of Exposition of Engineering Thermodynamics*

We present the foundations of thermodynamics in a novel sequence in which all basic concepts are defined in terms of well known mechanical ideas. Many definitions are new. The order of introduction of concepts is: system (constituents and parameters); properties; state; energy (without heat and work) and energy balance; classification of states in terms of time evolution; existence of stable equilibrium states; available energy; entropy (without heat and temperature) of any state (equilibrium or not) and entropy balance; properties of stable equilibrium states; temperature in terms of energy and entropy; chemical potentials; pressure; work; heat; applications of balances. This novel sequence not only generalizes the subject of thermodynamics to all systems (large or small) and all states (equilibrium and not equilibrium) but also avoids both the conceptual and definitional difficulties that have been recognized by so many teachers, and the confusion experienced by so many students.

The Interrelationship between Thermodynamics and Energetics: The True Sense of Equilibrium Thermodynamics

The interrelationship between the conventional thermodynamics and energetics has been discussed in detail. A number of flavors has been considered in the field of energetics, with the conclusion that the actual difference among all of them is rather superficial. A need to reconsider the foundations of thermodynamics and statistical physics has been pointed out. Such a re-consideration ought to facilitate formulating thermodynamics at any level of matter organization: from the microscopic through nano- and mesoscopic to the macroscopic one.

Entropy and its mathematical properties: consequences for thermodynamics

In this work, a comprehensive meaning for en- tropy is provided on the basis of foundations of information theory and statistical thermodynamics. For this purpose, the close relation between missing information and entropy is presented by emphasizing their probabilistic nature. Fur- thermore, the physical implications of the mathematical properties of the entropy function are exploited using the elementary notions of differential and integral calculus. Particularly, it is evidenced that the usual thermodynamic inequalities found in many textbooks of physical chemistry are direct consequences of the concavity of entropy. The aim of this work is to show that many concepts presented in textbooks of physical chemistry can be obtained in a simple and mathematically clear way.

Computational Thermodynamics and Kinetics for Magnesium Alloy Development

Abstract Computational thermodynamics and CALPHAD modeling prove useful for selecting and developing new magnesium alloys. This article summarizes an ongoing effort to establish a scientific foundation of computational thermodynamics and kinetics of magnesium alloys to achieve accelerated design and optimization of these alloys for weight reduction in the transportation industries.

Thermostatistical distribution of a trophic energy proxy with analytical consequences for evolutionary ecology, species coexistence and the maximum entropy formalism

Conventional thermodynamics and statistical mechanics deal with the study of physical systems under equilibrium conditions (EC). Internal EC at a temperature that differs from the environment temperature are sustained, in general, by some type of artificial boundaries imposed with research aims or with quotidian utility goals in many kind of domestic appliances; the typical example of academic lab is a closed system immersed in a thermal bath which keeps the temperature constant. However, the ecosystem is a far-from-EC open system. Therefore, conventional thermodynamics and statistical mechanics tend to be orthodoxly regarded as limited to explain the ecosystem functioning since, at the first glance; there seem to be several essential functional differences between it and the previously-mentioned kind of physical systems. This viewpoint averse to conventional physics is paradoxical in regard to the current ecological paradigm given the fully thermodynamic foundation of ecosystem ecology. However, additional evidence in favor of the usefulness of conventional physics to describe the ecosystem functioning have recently been published, pointing out to the possibility that the analytical approach to ecology based on our undergraduate knowledge of physics, unfortunately, could have been hastily neglected before producing its most valuable results. This paper, fully based on the above-mentioned evidence, performs an unavoidable additional step in order to complete such a proposal by showing that the Boltzmann distribution of molecular energy values can be simply and successfully adapted to model the distribution of values of a proxy for trophic energy across an increasing gradient of energy levels, in a very similar fashion to that of a standard trophic pyramid. Starting from this result and by using a balanced combination between plausible theoretical considerations and abundant empirical data, we analyze why this approach is in agreement with well-known ecological principles, at the same time that we explore the general empirical advantages and aftermaths derived from this suggestion. Finally, the article explores the usefulness of the thermo-statistical modeling of eco-kinetic energy per plot to understand those essential physical factors that: promote biological evolution, facilitate species coexistence, can explain the holes in the fossil record, and enhance our current viewpoint about the ecological meaning of entropy. In summary, this article provides simply understandable additional information that indicates, despite its far-from-EC nature, any natural ecosystem is not far away from the most orthodox principles of conventional physics.

Formation of alternating interfacial layers in Au-12Ge/Ni joints

Au-Ge alloys are promising materials for high-power and high-frequency packaging, and Ni is frequently used as diffusion barriers. This study investigates interfacial reactions in Au-12Ge/Ni joints at 300°C and 400°C. For the reactions at 300°C, typical interfacial morphology was observed and the diffusion path was (Au) + (Ge)/NiGe/Ni5Ge3/Ni. However, an interesting phenomenon – the formation of (Au,Ni,Ge)/NiGe alternating layers – was observed for the reactions at 400°C. The diffusion path across the interface was liquid/(Au,Ni,Ge)/NiGe/···/(Au,Ni,Ge)/NiGe/Ni2Ge/Ni. The periodic thermodynamic instability at the NiGe/Ni2Ge interface caused the subsequent nucleation of new (Au,Ni,Ge)/NiGe pairs. The thermodynamic foundation and mechanism of formation of the alternating layers are elaborated in this paper.

Microelement Formulation of Free Energy for Quasi-Brittle Materials

AbstractThis study aimed to find a simplified micromechanical formulation of Helmholtz free energy for quasi-brittle materials by making use of a system of microelements, and to provide a thermodynamic foundation for the development of multiscale constitutive theories. The microscopic incompatible strain field and residual stress field in an uncracked matrix between frictional microcracks were reproduced with microsprings, faults, and sliders by taking the microscopic fracture strain as a random variable. The locked microscopic additional strain energy—plastic free energy—was represented in an abstract way by the locked deformation energy within the microelement system. Straightforward free-energy functions dependent on the probability distribution of microscopic fracture strain were derived, which can be used in both deterministic and stochastic constitutive modeling.

A Unified View of “How Allostery Works”

The question of how allostery works was posed almost 50 years ago. Since then it has been the focus of much effort. This is for two reasons: first, the intellectual curiosity of basic science and the desire to understand fundamental phenomena, and second, its vast practical importance. Allostery is at play in all processes in the living cell, and increasingly in drug discovery. Many models have been successfully formulated, and are able to describe allostery even in the absence of a detailed structural mechanism. However, conceptual schemes designed to qualitatively explain allosteric mechanisms usually lack a quantitative mathematical model, and are unable to link its thermodynamic and structural foundations. This hampers insight into oncogenic mutations in cancer progression and biased agonists' actions. Here, we describe how allostery works from three different standpoints: thermodynamics, free energy landscape of population shift, and structure; all with exactly the same allosteric descriptors. This results in a unified view which not only clarifies the elusive allosteric mechanism but also provides structural grasp of agonist-mediated signaling pathways, and guides allosteric drug discovery. Of note, the unified view reasons that allosteric coupling (or communication) does not determine the allosteric efficacy; however, a communication channel is what makes potential binding sites allosteric.

Thermodynamic Measurements of Alloys and Compounds by Double Knudsen Cell Mass Spectrometry and Their Application to Materials Processing.

For the development and optimization of materials processing a collection of thermodynamic information concerning substances that participate in the reactions is important. One fundamental way to obtain such information is to measure the vapor pressure of gas species under conditions where they are in equilibrium with the condensed phases. Over the past 60 years Knudsen cell mass spectrometry has been used to identify and quantitatively determine gas species at high temperatures. This article describes thermodynamic foundation and examples of measurements in order to demonstrate the use of mass spectrometry focusing on the field of process metallurgy and recycling processes.

Comments on “The Gibbs Equation versus the Kelvin and the Gibbs-Thomson Equations to Describe Nucleation and Equilibrium of Nano-Materials”

An intriguing article was recently published, in which the historical foundations of surface thermodynamics of small particles were claimed to require revision.1 The Kelvin equation and the Gibbs-Thomson equation were claimed to be wrong, and the difference in the behavior of nanosystems compared to macro-systems was identified to be due to their high specific surface area and not to the high curvature of their interface. Unorthodox theoretical papers which attempt to alter the foundations of science are often difficult to get published in journals. In this sense, Kaptay’s paper1 is refreshing. However, its conclusions are flawed, as will be discussed in the following. When one treats an interface by the theory of thermodynamics, surface excess terms need to be added into a fundamental equation for the bulk material. For the Gibbs free energy the fundamental relation reads

Computational design of nanostructured steels employing irreversible thermodynamics

Recent theory demonstrates that the Kocks–Mecking formulation of plasticity has a foundation in multiscale irreversible thermodynamics. The key terms in the formulation can be obtained form experiments and from fundamental calculations. This offers two advantages to materials scientists and alloy designers: the Kocks–Mecking approach goes beyond being a phenomenological approach, gaining a solid physical foundation in multiscale computational physics; the new formulation can be employed to conceive new alloys displaying complex synergistic interactions at several scales and among several phases. This approach is ideal for designing and modelling nanostructured steels. This work incorporates four concomitant strengthening effects: solid solution, Hall–Petch, dislocation forest and precipitation. The new formulation is applied to nanostructured martensitic, dual phase and twinning induced plasticity steels, describing with excellent accuracy of their stress–strain behaviour.

On the thermodynamic foundations of solid-state cooler based on multiferroic materials

In this work, we present the theoretical description of thermodynamics of the solid-state cooler based on multiferroic materials. By virtue of the derived equations, we examine the temperature dependence of multiferroic with simultaneous exposure to the periodic electric, magnetic, and elastic fields. The presence of heat exchange with the environment is taken into account. It is demonstrated that the modulation of the applied electric field by magnetic and/or elastic ones can increase the temperature change in 2–3 times in comparison with just the electric field contribution. Additionally, the paper pays careful attention to the layered multiferroic structure. The temperature distribution of this system as a function of position is investigated. The obtained results provide a theoretical basis and physical insights for further development of the efficient solid-state cooler based on multiferroic materials.

ChemInform Abstract: Cooperativity and the Chelate, Macrocyclic and Cryptate Effects

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