Thermodynamic Regularities Research Articles

Термодинамічні закономірності структуроутворення високоміцного чавуну при модифікуванні та різних умовах кристалізації розплаву

The article presents the results of the analysis of thermodynamic regularities of structure formation of high-strength cast iron during modification and under different conditions of melt crystallization. The concept of the formation of graphite nuclei in high-strength cast iron is proposed. It has been established that during the modification of molten iron, as a result of a significant redistribution of all elements dissolved in it, impurities (sulfur, phosphorus, etc.) are removed, which makes it possible to obtain the structure of cast iron with nodular graphite with the use of modifiers. During the crystallization of cast iron with the release of austenite, direct microliquation of silicon with a distribution coefficient less than one is characteristic, manganese is more evenly distributed in the metal, and carbide stabilizing elements are treated in the liquid phase. A thermodynamic calculation of the thermal effects of the reactions of the release of graphite from carbon dissolved in iron, the transition of silicon and manganese from a liquid state to a solid state in the process of forming high-strength cast iron is presented. The physical and latent heat of crystallization of high-strength cast iron was determined by the enthalpy method. Thermodynamic calculations were performed and the thermal effects of reactions (9) in the melt of high-strength cast iron were determined, depending on their concentrations and the temperature of the melt. Using the results of thermodynamic calculations makes it possible to study the crystallization process by changing the number and composition of phases that are formed under the influence of heat release of phase transformations. It was found that the introduction of Si into pre-eutectic alloys (from 1 to 5% at.) leads to a slight decrease in the latent heat ΔН of crystallization of primary graphite (up to 3% for each atomic percentage of Si). As a result of the change in the temperature interval, its release causes a decrease in the total physical heat of crystallization Qf. It is shown that the thermodynamic analysis of the processes that occur during the crystallization of cast iron based on the data on the change in enthalpy for the system Fe-C-Xi (Xi = Si, Mn) indicates that with an increase in carbon, the change in enthalpy in the crystallization interval changes approx lyzno by 16 kJ/mol. The physical heat of crystallization has a significant effect on the change in the value of the total heat of crystallization of cast iron Qkr Fe-C-Xi (Xi = Si, Mn) in comparison with the Fe-C alloy. The latent heat of crystallization during solidification of high-strength cast iron is between 245 and 275 kJ/kg.

Comments on the calculation of thermodynamic adsorption equilibrium constant using the distribution coefficient in Journal of Molecular Liquids 380 (2023) 121725

This comment discussed the calculation of the standard equilibrium constant thermodynamic parameters about the paper published in Journal of Molecular Liquids 380 (2023) 121725. Recently, Khankhasaeva et al. (2023) published a high academic paper to reveal the adsorption kinetic and thermodynamic regularities of diclofenac (DCF) on Fe2O3-pillared montmorillonites (Fe-PMts). Although the author tries to convert the distribution coefficient (Kd) to the standard equilibrium constant (Ko), the calculation formula is incorrect due to the confusion of adsorbate and adsorbent. This creates dimension for Ko obtained from Eq. (2). In this comment, the origin and background of this kind of error is analyzed and the method for correcting the error is presented. We hope this comment clarifies the essence of calculating the standard equilibrium constant by using the distribution coefficient, so others avoid the propagation of this kind of error.

PHYSICO-CHEMICAL STUDIES OF RAW MATERIALS FOR OBTAINING PHOSPHORUS-CONTAINING FERTILIZERS

To date, accumulated industrial waste creates serious environmental problems in the regions. Therefore, their processing in order to obtain valuable products is an urgent task. As a result of the reduction electric smelting of phosphorite raw materials in the Novo-Dzhambul phosphorus plant, about 150-160 kg of cuttrel dust is formed per 1 ton of yellow phosphorus. The resulting cuttrel dust is considered as a secondary raw material, it can be used to obtain phosphoruscontaining mineral fertilizers, since the boiler dust contains a proportion of phosphorus and other useful components. The purpose of this work is the processing of phosphorus production waste - cuttrel dust with the use of sulfuric acid to obtain phosphorus-containing mineral fertilizers. Methodology. For the processing of cuttrel dust under experimental conditions, instrumental test methods were chosen using a scanning electron microscope (SEM) of the Jeol JSM-6490l V brand, a multi-parameter portable cyberscanner (PCD 650 Eutech) and a Q-1500 Derivatograph. Results. According to the results of microscopic studies, it was determined that the content of the main useful component in the cuttrel dust P2O5 in the range of 30-31%. The thermodynamic regularities of the process of decomposition of cuttrel dust with the help of a solution of sulfuric acid have been studied. The standard thermal effects of changes in the enthalpy, entropy and the value of the Gibbs energy of the system at a temperature of 333–363K were determined using the HSC-6 complex program. The methods of mathematical processing are considered in order to determine the reliability of the results of the experimental work. The optimal technological parameters of this process have been established and determined. Conclusion. A technology has been developed for obtaining phosphorus-containing monocalcium phosphate based cuttrel dust from the waste of the Novo-Dzhambul phosphorus plant using sulfuric acid solutions. The advantage of the resulting phosphorus-containing component is that it has a high solubility and absorption of phosphorus to plants. They are also characterized by a high content of phosphorus-containing substances, which ensure the growth and productivity of agricultural plants and plant resistance to environmental stress factors.

Recovery of used acetic acid via sulfuric acid

Kazakhstan has a huge phosphate raw material base, where the basis is made up of micro-grained phosphate ores of the Karatau basin. The depletion of reserves of high-quality commercial ores leads to the search for new methods of using the enrichment and sorting of low-grade technogenic ores, one of which is phosphate-siliceous slates. The presented study was carried out in two stages: at the first stage, phosphate-siliceous shales were enriched by the acetic acid method, regime technological parameters, kinetic and thermodynamic regularities of the process were determined. At the second stage of the research a method for recycling used acetic acid during the enrichment of low-grade phosphate-siliceous slates is proposed. In this case, sulfuric acid was chosen as the regenerating agent of acetic acid. The reliability of the performed studies was proved by the use of modern complex research methods: scanning electron microscopy, Energy Dispersive X-Ray and X-Ray difraction analyses. To determine the course of a particular reaction, a thermodynamic analysis was performed using modern HSC 6.0 software. The kinetic data are determined by calculation. The obtained experimental data were subjected to statistical analysis (Chaddock scale, standard deviation, coefficient of determination). The mechanism of interaction of an acetate solution with sulfuric acid is illustratively described. In conclusion, the sulfuric acid method is suitable for the regeneration of applied acetic acid. In this case, a by-product is formed in the form of calcium sulfate. This product can be used as a building binder (confirmed by the protocol of the “National Center of Expertise” of the Republic of Kazakhstan).

Investigation of Thermodynamics of Adsorption of Cadmium Ions Cd (II) from Model Solutions by Glass Fiber Materials

Thermodynamic regularities of the adsorption of cadmium ions Cd (II) using BSTV basalt fiber and M20-STV-2.0 and M20-UTV-0.6 glass fibers are investigated. The adsorption capacity of the investigated fibers with respect to the cadmium ion Cd (II) was determined. The degree of adsorption, values of the distribution coefficient, and adsorption equilibrium constants for the Langmuir and Freundlich models were determined. The adsorption equilibrium for the cadmium ion Cd (II) is well described by the Langmuir model. Thermodynamic characteristics of the process were determined: the change in the Gibbs energy, the change in the enthalpy and entropy of the adsorption process at three temperatures. The change in the Gibbs energy corresponds to the spontaneous occurrence of the adsorption process. A decrease in the change in the Gibbs energy of adsorption in a series of fibrous materials (BSBV basalt fiber–M20-STV-2.0 glass fiber–M20-UTV-0.6 glass fiber) is due to the entropy effect. The adsorption of cadmium ions Cd (II) on glass fiber materials is exothermic. The values of the thermal effects, found by the graphical method in accordance with the isobar equation of the chemical reaction, do not exceed 25 kJ / mol and indicate the physical nature of the process.

Thermodinamics and Mutual Distribution of Macromolecules in the Systems: Chlorine Chlorocontaining Polymers

In given work a scientific base compatibility of polymers, produced by industry have been studied by revealing of thermodynamically regularities of polymer mixtures. The most significant thermodynamic regularities of the mixtures of polyolefin , produced by industry and heterochained polymers have been revealed and on this base the scientific bases of their compatibility have been developed for creation of multicomponent compositional materials with given complex of operating properties.

Infinite Teaching (R) In Collection and (R*) By Allegory and Conformity

In given work a scientific base compatibility of polymers, produced by industry have been studied by revealing of thermodynamically regularities of polymer mixtures. The most significant thermodynamic regularities of the mixtures of polyolefin , produced by industry and heterochained polymers have been revealed and on this base the scientific bases of their compatibility have been developed for creation of multicomponent compositional materials with given complex of operating properties. Key words: polymer-polymer mixtures, chlorinated polyethylene (CPE), polymethylmetaacrylate (PMMA), polyethylene of low density (PELD), chlorcarboxylated polyethylene of low density (CCPE) chlorinated PELD (CPE), polyvinyl chloride (PVC), criteria of compatibility, chlorination, upper and lower critical temperature, specific holding of volume, Qibbs mixing energy, parameter of solubility, distribution of macromolecules, chlorine-chlorocontaining polymers, polar groups, thermodynamically compatibility, sorbate, gas-carrier.

Thermodinamics and Mutual Distribution of Macromolecules in the Systems: Chlorine Chlorocontaining Polymers

In given work a scientific base compatibility of polymers, produced by industry have been studied by revealing of thermodynamically regularities of polymer mixtures. The most significant thermodynamic regularities of the mixtures of polyolefin , produced by industry and heterochained polymers have been revealed and on this base the scientific bases of their compatibility have been developed for creation of multicomponent compositional materials with given complex of operating properties. Key words: polymer-polymer mixtures, chlorinated polyethylene (CPE), polymethylmetaacrylate (PMMA), polyethylene of low density (PELD), chlorcarboxylated polyethylene of low density (CCPE) chlorinated PELD (CPE), polyvinyl chloride (PVC), criteria of compatibility, chlorination, upper and lower critical temperature, specific holding of volume, Qibbs mixing energy, parameter of solubility, distribution of macromolecules, chlorine-chlorocontaining polymers, polar groups, thermodynamically compatibility, sorbate, gas-carrier.

Исследование закономерностей и разработка модели процесса гидрокрекинга вакуумного газойля

In this work, the regularities of the vacuum gasoil hydrocracking process were studied, which include: determination of the key components of the reacting mixture and key reactions, studying the thermodynamic regularities, identification of the regularities of the influence of technological parameters on the transformation of the key reacting components. The model of the process was developed.

Integrated mathematical modeling of catalytic cracking and zeolite-containing catalyst oxidative regeneration

The work is aimed at establishing the thermodynamic, kinetic and hydrodynamic regularities of the vacuum gas oil catalytic cracking and the zeolite-containing catalysts regeneration, which served as a catalytic cracking reactor mathematical model development basis. The prediction calculations ensured the catalyst circulation ratio optimization depending on the catalyst flow temperature after regeneration. To maintain the gasoline fraction maximum yield (58.47 and 58.38 wt%) it is necessary to keep the catalyst circulation ratio at the level of 6 and 9.5 tonscat/tonsfeed if the catalyst flow temperature after regeneration are 700 and 650 °C, respectively.

Thermodynamic Regularities of Nuclei Growth during Crystallization of Metastable Alloys

The process of crystal growth in a metastable multicomponent melt has a high speed of the solidification front, which captures atoms of some other components. As a result of such a growth, at the surface of the growing crystal the effect of “impurity capture” is observed, and the concentrations of components significantly deviate from the local equilibrium. Under such conditions, the conventional physico-chemical methods for description of processes at the interfacial surface become inapplicable. Therefore, a new variational approach was applied for an integrated description of diffusion and thermal processes at the phase interface. The growth rate of crystal nucleus in a metastable melt was obtained, using the methods of non-equilibrium thermodynamics. The developed approach allows estimation of the degree of metastable effects influence on a crystal growth rate.

Peculiarities of application of natural and man-caused materials for steel alloying and modifying

Considerable reserves of improvement of steel quality and reduction of costs of its production are concealed in a possibility of active and purposeful formation their structure and the properties by introduction into the melt modifiers, alloying and microalloying additives. Due to the task of decreasing costs, studies on alloying and modifying of metal by natural and man-caused materials are very actual. Thermodynamic regularities of steel alloying and modifying processes by natural and man-caused materials, including manganese ores of various structures, BOF vanadium slag, barium- strontium modifier, obtained from the complex ores containing barium and strontium considered. Possibilities of wide application of various structure manganese ores for steel alloying by manganese without use of standard manganese alloys as well as vanadium slag for microalloying by vanadium demonstrated. Metallurgical properties barium-strontium natural modifier obtained and the possible mechanism of the modifying impact of barium and strontium on quality of metal studied. It was determined, that the effect of modifying by barium can revealed in steels, deoxidized only by silicon, and for modifying by strontium or joint modifying by barium and strontium it is necessary to apply aluminum as deoxidizing agent. Industrial testing of the above-stated materials showed reliability of studies, accomplished at thermodynamic modeling and laboratory studies of calculations and conclusions. Recommendations on optimization of technologies of steel alloying and modifying made. It was proved that use of the materials of the study allows to improve technical and economic indices of the process of production of steels and to increase considerably quality of final steel products. Conclusions on significant expansion of natural and man-caused materials prospects worded.

Physicochemical fundamentals of phase formation in silicon layers implanted with oxygen and carbon

The thermodynamic and kinetic regularities of processes occurring during heat treatment in silicon layers implanted with oxygen and carbon ions have been considered. We have analyzed the regularities of silicon deformation, impurity distribution and defect formation after different annealing modes. Diffusion smearing of implanted impurities in these layers has not been observed during carbon and oxygen implantation. As-annealed carbon does not occupy sites of the silicon lattice, in contrast to the implantation behavior of other impurities, e.g. boron and phosphorus. Phase formation regularities in implanted layers during subsequent heat treatment have been analyzed. Changes in the free energy of the system during heterogeneous and homogeneous precipitate nucleation have been compared. Sequential implantation with carbon and oxygen ions has been found to initiate diffusion flows of carbon and oxygen toward the center of the ion doped layer (the uphill diffusion phenomenon). The possibility of uphill diffusion has been analyzed from the standpoints of the Onsager theory. We show that the contribution of the chemical interaction between oxygen and carbon is far greater than the entropy contribution to the diffusion flux. We have demonstrated the high efficiency of ion doping with oxygen and carbon for gettering of uncontrolled impurities from active regions of silicon structures. The efficiency of this gettering process has been assessed for epitaxial structures in which layers had been grown on silicon wafers implanted with these impurities. Uphill diffusion in the layers after double doping with carbon and oxygen has led to the formation of more defects which may provide for efficient gettering. We have found the optimal oxygen and carbon implantation dose ratio for maximal gettering efficiency.

Foundation of statistical mechanics: The auxiliary hypotheses

AbstractStatistical mechanics is the name of the ongoing attempt to explain and predict certain phenomena, above all those described by thermodynamics on the basis of the fundamental theories of physics, in particular mechanics (classical or quantum), together with certain auxiliary assumptions. In another paper in this journal, Foundations of statistical mechanics: Mechanics by itself, I have shown that some of the thermodynamic regularities, including the probabilistic ones, can be described in terms of mechanics by itself. But in order to prove those regularities, in particular the time asymmetric ones, it is necessary to add to mechanics assumptions of three kinds, all of which are under debate in contemporary literature. One kind of assumptions concerns measure and probability, and here, a major debate is around the notion of “typicality.” A second assumption concerns initial conditions, and here, the debate is about the nature and status of the so‐called past hypothesis. The third kind of assumptions concerns the dynamics, and here, the possibility and significance of “Maxwell's Demon” is the main topic of discussions. This article describes these assumptions and examines the justification for introducing them, emphasizing the contemporary debates around them.

CORRELATION OF PROPERTIES OF VITA-MEDIUM AND THEIR INTERPRETATIONS IN INTELLIGENT MODEL

It is shown that the maximally full description of vita-medium with “the substantially sensor system” on the basis of expressed syntax properties implies introduction of complex assertions of experts built on elementary estimates. Natural conditions of determinacy and completeness are put on multiple models by corresponding to all sensor components which control vita-medium properties. The trueness of assertions by experts and inadequacy measure of vita-medium properties provision have been considered in the process of sensor control.It is shown that thermodynamics ideas of informational processes can be used for the generalized description of vita-medium during sensor control of its properties. In order to find out thermodynamic regularities of the censor control procedure the series circuit of conversions is considered: object property – controlled parameter – feature distortion – generalized coordinate – information model. During the high precision control the information quantity is determined with the aid of relative precision logarithm, and in case of comparatively rough determination of vita-medium parameters it depends on the square of sensor control relative precision.Reasons and consequences of distorted sensor images have been considered with the use of technical means of outlines of events and vita-medium properties provision. A contradictory, two-value character of impact on the process of control of extra technical means is shown, which are included between the controlled object and “the subjective sensor system”. Probability of provision of successful collection, procession, accumulation and renewal of information on vita-medium parameters with intelligent system means has been analyzed.

Classical and quantum many-body effects on the critical properties and thermodynamic regularities of silicon

Using molecular simulation, we determine the critical properties of Si as well as the loci for several remarkable thermodynamic contours spanning the supercritical region of the phase diagram. We consider a classical three-body potential as well as a quantum (tight-binding) many-body model, and determine the loci for the ideality contours, including the Zeno line and the H line of ideal enthalpy. The two strategies (classical or quantum) lead to strongly asymmetric binodals and to critical properties in good agreement with each other. The Zeno and H lines are found to remain linear over a wide temperature interval, despite the changes in electronic structure undergone by the fluid along these contours. We also show that the classical and quantum model yield markedly different results for the parameters defining the H line, the exponents for the power-laws underlying the line of minima for the isothermal enthalpy and for the density required to achieve ideal behavior, most notably for the enthalpy.

The Size Dependence of Dissolution Thermodynamics of Nanoparticles

Dissolution of nanoparticles is involved in the preparation, research and application of nanomaterials, but there is a surprising difference in dissolution thermodynamics between nanoparticles and the corresponding bulk materials. In the paper, the relations of dissolution thermodynamic properties, equilibrium constant of nanoparticles, respectively, and particle size were derived by introducing interface variables and the surface chemical potential. Experimentally, the solubility of nano-barium sulfate with different average particle sizes at different temperatures were determined by the method of electrical conductivity, obtaining the influencing regularities of particle size on the dissolution thermodynamic properties and the equilibrium constant. The regularities are in accordance with the theory. The results show that there are remarkable effects of particle size of nanoparticles on the dissolution thermodynamic properties and the equilibrium constant; with the decreasing of the size of nanoparticles, the dissolution equilibrium constant increases, while the standard dissolution Gibbs free energy, the standard dissolution enthalpy and the standard dissolution entropy decrease; and the logarithm of the dissolution equilibrium constant, the standard dissolution Gibbs free energy, the standard dissolution enthalpy and the standard dissolution entropy are linearly associated with the reciprocal of particle size, respectively. This new theory provides a quantitative description of nanoparticles dissolution behavior, and has important scientific significance for understanding and predicting of thermodynamic regularity of dissolution concerned in the preparation, researches and applications of nanomaterials.

Amino-functionalized ionic liquids as carbon dioxide scavengers. Ab initio thermodynamics for chemisorption

Carbon dioxide (CO2) capture by aqueous amine solutions is an industry grade technology nowadays. Some drawbacks of this technology motivate development of new CO2 scavengers. Due to low volatility, thermal stability, non-flammability, and tunability, room-temperature ionic liquids (RTILs) are viewed as prospective universal solvents. The amino groups can be grafted to the organic cations yielding species with the increased CO2 capture performance. Many favorable physical properties of the original RTILs can be retained in this way. We report systematic computational analysis (enthalpy, entropy, Gibbs free energy, geometric parameters, partial charges, vibrational frequencies) of six organic cations, each representing a different family of RTILs. We found that the longer side hydrocarbon chain of the cations offer the most prospective sites in view of the CO2 capture. In turn, chemisorption in the rings is less thermodynamically favorable. It was possible to corroborate the thermodynamic regularities in terms of electrophile+nucleophile organic reactions involving partial charges and structure perturbations due to carbamate formation. The reported results foster development of alternative CO2 scavengers by eliminating their volatility and increasing reaction yields.

Towards new thermodynamic regularities for dense fluids based on the effective attraction pair potential via the perturbation theory

In the present work, several new thermodynamic linear isotherm regularities for the dense fluids have been derived for the first time. For this purpose, the thermodynamic perturbation theory (TPT) employing only the attractive effective pair potential (AEPP) as u(r)=−εeff (σeff/r)m was used, where σeff which is the effective hard core diameter, is temperature dependent and m>0. Based on the derived regularities, the isotherm (Z−Z(0))v2 is a linear function of ρ2, ρ and 1/ρ, depends on the values of m=12, 9 and 6, respectively where Z−Z(0) is the difference between the experimental compressibility factor of the real fluid (Z) and that of the reference fluid (Z(0)). Also, Z−Z(0) is a linear function of ρ2 when the value of m=3 and is linear in terms of ρ1/3 for m=1. The latter linearity is similar to the results obtained using the Yukawa effective pair potential along with TPT. It is worthy to note that the observed regularities are only due to the contribution of the effective intermolecular attraction in the fluid. We have noticed that the effective hard core diameter depends on the range of attraction from of the effective pair potential, in such a way that it increases when the range of attraction is longer. The experimental data have been used to check the validity of the derived regularities for eleven fluids namely, Ar, Kr, H2, N2, NH3, CH4, C2H6, C3H8, C6H6, CH3OH and CO2. The most important outcome of this study is that different types of the regularities in the dense fluids may be derived by using the perturbation theory with a suitable reference fluid with temperature dependency for the σeff.

Regarding the Universality of Some Consequences of the van der Waals Equation in the Supercritical Domain

We show that some of the thermodynamic regularities, following from the van der Waals (VDW) equation, are valid for the real substances and models described by completely different equations of state. These regularities relate to lines of ideal enthalpy, enthalpy minima, and isothermal compressibility maxima. The first one appears to be the straight line on the density-temperature plane, while for the two others there are universal relations, which are the same for various substances and models (argon and Lennard-Jones system as examples). The model systems were studied by Monte Carlo simulations (NVT MC), while experimental data were analyzed for the real substances. Our numerical calculations and the analysis of experimental data have shown that for the considered systems these curves are similar to the VDW ones.