Thermal Analysis Methods Research Articles

DEVELOPMENT OF TECHNIQUES AND EXPERIMENTAL INSTALLATIONS FOR DETERMINING THE HEAT CAPACITY OF IRON ORE MATERIALS

One of the most important thermophysical pellets characteristics is considered — their heat capacity, which affects the technological production process of iron ore pellets at the stage of their heat treatment in a layer on a conveyor belt. Since the physical heat capacity of materials is determined by the enthalpy value, the mixing method is used to measure the latter, which is implemented on an installation with an adiabatic calorimeter. The research object is Kachkanar pellets of different basicity. The average values of the pellets enthalpy and their physical heat capacity, taking into account changes in the phase and chemical composition of the material, are presented in the interpolation equations form. The temperature dependences of the apparent heat capacity of pellets of various basicity at different heating rates were determined using a newly created experimental setup that allows determining the complex of thermophysical characteristics. Estimates of the enthalpy change and the dependence of the apparent heat capacity on temperature for fluxed and unfluxed concentrates of Sokolovsko-Sarbaysky mining and processing plant were carried out on an experimental installation using the method of quantitative thermal analysis. The presented methods for determining the enthalpy and heat capacity of iron ore pellets and concentrates, as well as the designs created for the implementation of these methods can be used to determine the heat capacities of various materials of metallurgical production and to optimize the operating parameters of their heat treatment.

Design, Development, and In vitro Evaluation of Single Unit Hydrodynamically Balanced System of Captopril

Background: This study investigated the use of in situ polyelectrolyte complex formation by using two oppositely charged polysaccharides [Chitosan (cationic), Sodium Alginate (anionic)]. It forms 3-D intercalation and interpenetrating network helping in controlling the release of highly acid-soluble Captopril. Objective: To develop a polyelectrolyte complex based single unit gastroretentive tablet by using optimization based 3 (2) Taguchi factorial design for controlled delivery of Captopril. Materials and Methods: Gastroretentive Captopril tablets were prepared by the direct compression technique. Total 09 batches were prepared as per 3 (2) Taguchi factorial design studies of 100 tablets each. Results: Thermal analysis method revealed that there is a formation of PEC between chitosan and sodium alginate. In vitro buoyancy and T60%, drug release studies revealed that due to complex formation, formulation remains stable and remains buoyant. From factorial design studies, it was interpreted that for buoyancy time (Y1) chitosan desired effect value was found higher. For 60% drug release (T60%; Y2) both chitosan and sodium alginate have a synergistic effect. Durbin Watson's statistical model and residual data suggested that the model is statistically validated. All formulations follow the zero-order kinetics. Stability studies revealed that formulations F5 and F9 remain stable for long-term stability studies without showing any significant changes. The fit analysis studies indicated that the prepared formulation was different from the innovator product indicating low f1 and f2 values. Conclusion: From the result generated it was concluded that chitosan-sodium alginate polyelectrolyte complex has sufficient potential to retard the release of CPT.

Thermodynamic calculations and experimental studies of ternary molten salts for high-temperature thermal energy storage

Chloride, fluoride, and carbonate salts act as potentially promising thermal storage media for high-temperature thermal energy storage (TES) systems. In this study, the eutectic components of three ternary molten salts; i.e., NaCl–KCl–LiCl, NaCl–KCl–NaF, and NaCl–KCl–Na2CO3 were first predicted by using thermodynamic calculations and the accuracy was further verified by differential scanning calorimetry. Next, the melting point, thermal conductivity, latent heat, specific heat, and TES density of the three eutectic salts were determined and calculated by thermal analysis methods and compared with those of Solar and Hetic salts. The results show that the eutectic salt NaCl–KCl–Na2CO3 exhibits the highest TES density, which is 1.87 and 1.31 times higher than that of the Solar salt and Hetic salt, respectively. Moreover, the costs of the three eutectic salts were calculated and analyzed herein, and the cost per unit TES density of the eutectic salt NaCl–KCl–Na2CO3 accounted for only 17.01 % and 29.75 % of the cost of the Solar salt and Hetic salt, respectively. The three eutectic salts exhibit good thermal stability even at a high temperature of 700 °C, and thus act as potential candidates for thermal storage materials for the next-generation concentrating solar power plants.

Thermal analysis methods for wound rotor synchronous motors with water-cooling jackets

A thermal equivalent circuit (TEC) was presented as an effective thermal analysis method for a wound rotor synchronous motor (WRSM) with a water-cooling jacket. The effectiveness of the TEC analysis was verified by comparison with the results of the experiments and numerical analysis. The steady-state temperature obtained from the TEC matched well with those obtained from the experiments and numerical analysis. The transient temperature variation in each part of the WRSM estimated by the TEC was in good agreement with the experimental results. Therefore, TEC can easily estimate the temperature information of the WRSM.

Interactions of Clotrimazole with Certain d-Metal Compounds and with Organic Acids

During the interaction of aqueous-ethanol or ethanol solutions AgNO3, H[AuCl4], and CuCl2, as well as aqueous suspensions of slightly soluble copper(II) salts Cu(C6H4NO2)2·H2O, Cu(C7H5O2)2∙3H2O, and CuC7H4O3∙H2O with the ethanol solution of clotrimazole at pH of ~(5.0–5.5), the [Ag(C22H17ClN2)2]NO3·2H2O, [Au(C22H17ClN2)Cl3], [Cu(C22H17ClN2)2Cl2]·5H2O, Cu(C22H17ClN2)4(C6H4NO2)2, Cu(C22H17ClN2)4(C7H5O2)2, and Cu(C22H17ClN2)3(C7H4O3)·2H2O compounds are synthesised. They are characterised by elemental, thermal, thermogravimetric, and IR spectroscopic methods of analysis. The [Ag(C22H17ClN2)2]NO3·2H2O complex was shown to have a higher antimycotic activity against Saccharomyces cerevisiae fungi than that of AgNO3 and C22H17ClN2. Cocrystals/salts of the composition C22H17ClN2·C6H5NO2, C22H17ClN2·C7H6O2, 2C22H17ClN2·C7H6O3, and 2C22H17ClN2·C19H19O6N7·H2O are obtained from aqueous and aqueous ethanol suspensions containing nicotinic, benzoic, salicylic, and folic acids and clotrimazole (pH is 4.5–6.0). These cocrystals and salts were studied usin thermogravimetric, IR-spectroscopic methods. Diffraction patterns of the powders were obtained. The influence of the difference in the pKa components on the ability to form cocrystals/salts was assessed.

Thermal diffusion in discontinuous media: A hybrid peridynamics-based machine learning model

This paper introduces a novel hybrid formulation of a peridynamics-based machine learning model for thermal diffusion analysis in one-dimensional and two-dimensional problems with evolving discontinuities. The hybrid model employs a multivariate linear regression approach to establish the relationship between the temperature values of material points, their neighboring points, and the applied external heat flux. The thermal modal analysis method uses the finite element method to generate training and testing data. An efficient numerical procedure is also developed to couple the peridynamics model and the peridynamics-based machine learning model. The model is analyzed under multiple configurations of micro-thermal conductivity functions for one-dimensional thermal bar problems, under both steady-state and transient loading conditions, to identify the configuration that exhibits superior convergence behavior towards the local solution. Furthermore, benchmark problems demonstrate the high accuracy of the formulated hybrid model, including the analysis of thermal plates with discontinuities, such as a plate with a hole, a plate with a pre-existing insulated crack, and plate with a bi-material interface with stationary and evolving discontinuances. The hybrid model effectively captures intricate discontinuities and boundaries while being computationally efficient, indicating its potential for thermal diffusion analysis in one- and two-dimensional problems with stationary and evolving discontinuities.

A Numerical Method for Transient Thermal Analysis of No-Insulation REBCO Pancake Coils With Several Resistive Joints

A Numerical Method for Transient Thermal Analysis of No-Insulation REBCO Pancake Coils With Several Resistive Joints

Thermal performance design and analysis method for energy cast-in-place piles (E-CIPs) installed in diaphragm walls

Thermal performance design and analysis method for energy cast-in-place piles (E-CIPs) installed in diaphragm walls

Analysis of flow characteristics and cooling performance of a novel impingement/effusion structure with bypass hollow holes

As a promising cooling technique, the double-wall cooling structure has been integrated into the design of advanced aeroengine high-temperature components. However, its widespread application in configurations with low pressure ratios between secondary flow and the main flow is hindered due to significant internal flow resistance. To address this issue, a novel low-resistance hollow pillar double-wall structure (NHDW) is developed. This study conducts conjugated heat transfer numerical simulations of NHDW and the traditional solid pillar double-wall structure (TSDW) for comparative analysis. Flow characteristics are examined to understand the sources of internal flow resistance and the coupling mechanism between internal and external heat transfer. The results demonstrate that the NHDW exhibits substantially lower flow resistance than the TSDW, with the total pressure loss dropping to approximately 1/3 of the corresponding TSDW under hole inclination angles of 30°, 60°, and 90°. The reduced internal flow resistance of the NHDW is attributed to the parallel bypass flow within the hollow pillar. Moreover, the overall cooling effectiveness (ϕ) of NHDW is enhanced by 9.2%–16.9% for different inclination angles at a blowing ratio of M = 1.0. Additionally, the interaction vortex structure on the mainstream side surface of the NHDW significantly improves the external cooling effectiveness, contributing to the overall enhancement of the cooling performance. Furthermore, a one-dimensional thermal resistance analysis method is introduced to distinguish the contributions of internal cooling and external film cooling. This analysis highlights the importance of external cooling enhancements in the novel structure.

Numerical thermal analysis of synchronous reluctance generator for wind energy application

AbstractThis paper focuses on the thermal analysis of the synchronous reluctance generator with a rating of 2.1 kW. It mainly uses explicit, and implicit finite difference methods for thermal analysis to reduce the complexity of thermal calculation for the machine's components. It compares the results with the results obtained using a finite element analysis (FEA) and includes the experimental verification of the obtained results. The explicit, and implicit finite difference thermal analysis is relatively simple and computationally fast. Once the design parameters are known, the electric losses and iron losses of the synchronous reluctance generator are evaluated. These machine parameters are utilized in developing the explicit finite difference (EFD), an implicit finite difference (IFD), and a 3D FEA model for thermal analysis. It is observed that the obtained results from the EFD, IFD, FEA, and experiments are very close to each other, and the temperature rise for the designed machine is within the desired and acceptable range.

Luminescent Hybrid BPA.DA-NVP@Eu2L3 Materials: In Situ Synthesis, Spectroscopic, Thermal, and Mechanical Characterization.

A series of homogeneous hybrid BPA.DA-NVP@Eu2L3 materials were obtained through an in situ approach where the luminescent dopant was formed at the molecular level with different contents (0.1; 0.2; 0.5; 1; and 2% by weight). A Europium(III) complex (Eu2L3) with quinoline-2,4-dicarboxylic acid was applied as a luminescence additive while a polymer matrix consisted of a combination of bisphenol A diacrylate (BPA.DA) and N-vinylpyrrolidone (NVP) monomers. Synthesis steps and the final materials were monitored by NMR and Fourier transform infrared spectroscopy (FTIR). The emission, excitation spectra, lifetime, and quantum yield measurements were applied for the determination of the photophysical characteristics. The thermal and mechanical properties of the obtained materials were tested via thermal analysis methods (TG/DTG/DSC and TG-FTIR) in air and nitrogen atmospheres, dynamic mechanical analysis (DMA), and hardness and bending measurements. Generally, even a small addition of the metal complex component causes changes in the thermal, mechanical, and luminescent properties. Hybrid materials with a greater europium complex content are characterized by a lower stiffness and hardness while the heterogeneity and the flexibility of the samples increase. A very small amount of an Eu2L3 admixture (0.1% wt.) in a hybrid material causes an emission in the red spectral range and the luminescence intensity was reached for the BPA-DA-NVP@1%Eu2L3 material. These materials may be potentially used in chemical sensing, security systems, and protective coatings against UV.

Studying the properties of ash and slag waste for use in the manufacture of construction products

Purpose. The research purpose is to study the physical-chemical properties of ash and slag waste generated during the coal combustion at the Ekibastuz field in Kazakhstan, to determine the possibility of using waste as a secondary resource to reduce the negative human impact on the environment. Methods. The research uses the methods of X-ray phase and differential thermal analysis, as well as chemical analysis. The X-ray phase analysis makes it possible to determine the phase composition and structure of ash and slag wastes, while differential thermal analysis is used to study their behavior with temperature changes. A chemical analysis is performed to determine the composition of ash and slag. Findings. The chemical and granulometric composition of ash and slag waste from the Ekibastuz field coal combustion has been determined. Analysis of the ash chemical composition showed that its main components are silicon and aluminum oxides, as well as a significant amount of iron oxide. The results obtained confirm the possibility of using ash and slag waste as a secondary raw material to reduce the negative impact on the environment. Originality. It has been revealed that the thermal conductivity, ultimate strength and water-absorption of ceramic brick samples depend on the amount of ash added and the firing temperature. The possibility of obtaining building materials with minimum cement content has also been substantiated, which is a new and promising approach, given the high cost of cement as the main building material. Practical implications. The practical value of the research is in solving environmental problems associated with the use of ash and slag waste. Using these wastes as a secondary raw material, it is possible to reduce the anthropogenic burden on the environment, as well as the volume of ash dumps. In addition, vacant land previously occupied by ash and slag mixtures can be used for economic purposes.

Synthesis of cellulose nitrates from Miscanthus × giganteus var. KAMIS cellulose obtained under pilot production conditions

The work is devoted to the study of a novel national raw material resource Miscanthus × Giganteus var. KAMIS, which is positioned as one of the most promising natural sources for obtaining high-quality cellulose for the purpose of its further chemical functionalisation. A batch of technical cellulose isolated from raw materials under pilot production conditions using the nitric acid method having a cellulose content of 50.2% was characterized by high α-cellulose mass fraction (92.8%) and degree of polymerisation (1200) values. On the basis of the pilot batch of technical cellulose, a sample of cellulose nitrates offering basic functional properties was obtained: mass fraction of nitrogen – 11.18%; viscosity – 48 MPa·s; solubility – 94%. The synthesised sample is characterized by extremely high solubility in acetone, confirming the production of cellulose nitric acid esters, and a high yield of 150%. IR-Fourier spectroscopy was used to identify the main functional groups in the experimental batch of technical cellulose (3384, 2902, 1639, 1428, 1370, 1319, 1161, 700–500 cm-1) and in a sample of cellulose nitrates (1659, 1278, 834, 746, 683 cm-1). Acorresponding affiliation to cellulose and cellulose nitric acid esters was established. The structural and morphological features of the fibres of the experimental batch of technical cellulose and a sample of cellulose nitrates were characterised using scanning electron microscopy. Combined methods of thermogravimetric and differential thermal analyses were used to establish high initial temperature (197 °C) and specific heat of decomposition (6.92 kJ/g) values at the beginning of intensive decomposition. The obtained results substantiate the possibility to chemically functionalise cellulose isolated from a new alternative source into cellulose nitric acid esters with satisfactory functional properties.

Optical, thermal and gamma ray attenuation characteristics of tungsten oxide modified: B2O3–SrCO3–TeO2–ZnO glass series

The glass series modified by tungsten oxide was created using the compounds (75-x) B2O3– 10SrCO3– 8TeO2– 7ZnO - xWO3, where x = 0, 1, 5, 10, 22, 27, 34, and 40% mole percentage. A UV–visible spectrophotometer and thermogravimetric-differential thermal analysis (TG-DTA) methods were employed to characterize the specimen's optical and phase transition attributes, respectively. The mass-attenuation coefficient (AC) of all created glasses from BSTZW0 to BSTZ7 was estimated using Geant4 code from 0.05 to 3 MeV and compared to the XCOM software results, with a relative difference of less than 2% between the two results. The increase of WO3 percentage lead to an increase in the Linear-AC at each studied energy, and this is mainly due to the fact that the higher the percentage of WO3 in the glass increases its density which causes an increase in the Linear-AC, so an energy of 0.06 MeV, as an example, the values of the Linear-AC was 4.009, 4.509, 5.442, 6812, 8.564, 9.856, 10.999 and 11.628 cm−1 form BSTZW0 too BSTZW7, respectively. The Half-VL (value layer), Mean-FP (free path), Tenth-VL, and Radiation attenuation performance (RAP) were also calculated for the current BSTZW-glass samples and revealed that BSTZW7 had the best gamma ray attenuation performance at all discussed energies when compared to other studied glass samples.

ЭФФЕКТИВНОСТЬ ОГНЕЗАЩИТНЫХ ПРОПИТОЧНЫХ СОСТАВОВ ДЛЯ ДЕРЕВЯННЫХ КОНСТРУКЦИЙ

The article considers the results of evaluating the flame retardant effectiveness of various flame retardants by the method of fire exposure according to GOST 53292–2009 and by methods of thermal analysis (thermogravimetry, differential thermogravimetry, derivative thermal analysis). According to the results of fire of surface application of flame retardants from 350 to 550 kg/m2, group I or II of flame retardant
 efficiency is provided (mass loss from 8,67 to 25 %). It is shown that the group of flame-retardant effectiveness does not actually reflect the nature and degree of realization of the mechanism of flame retardant action of flame retardants, their ability to influence the features of thermal transformations of wood. It has been established that the type of flame retardant, its chemical component composition and the mechanism of flame retardant action to varying degrees affect the main stages of thermal oxidative decomposition of wood. The results obtained can be used to evaluate the effectiveness of fire protection in reducing the intensity of the charring process and predicting the intensity of smoldering (flameless) combustion of wood. tests, it was found that with the consumption

Synthesis of Li7P3S11 Solid Electrolyte for All-Solid-State Lithium-Sulfur Batteries

Sulfur-containing solid electrolytes are highly attractive to scientists and are increasing day by day. Recently, Li7P3S11, Li10GeP2S12, and Li11Si2PS12 solid electrolytes have been of great interest in literature. The ionic conductivity of these electrolytes can even be reached a value of 10-2 S/cm. For this purpose, Li7P3S11 solid electrolyte is synthesized by mechanical alloying method for all-solid-state Lithium Sulfur batteries in this study. To do this, Li2S and P2S5 ingredients were mixed in a ball mill at certain stoichiometric ratios. The crystallization temperatures of the obtained powders were determined by the DSC thermal analysis method, and they were crystallized under a protective atmosphere at the appropriate crystallization temperature. Then, the obtained powders, very sensitive to the open atmosphere, were subjected to XRD and Raman analysis with a custom-made trap. Structurally characterized powders were electrochemically tested with electrochemical impedance spectroscopy and cyclic voltammetry analyses in a special solid-state cell. It has been observed that the results are compatible with the literature, and it has been determined that the synthesized electrolyte can be used as a suitable candidate for lithium sulfur batteries.

Processability and reprocessability maps for vitrimers considering thermal degradation and thermal gradients

A lack of fundamental knowledge about the kinetic mechanisms governing the processing and reprocessing of vitrimers forces a trial-and-error procedure to be adopted when choosing treatment conditions. In this work, we develop diagrams to be used as a straightforward tool to decide the curing and thermoforming parameters of vitrimers. The thermal stability of a disulfide containing epoxy has been evaluated by means of thermal analysis methods. By characterizing the kinetics of the curing and decomposition of the resin through a model-free kinetic method, we have been able to generate an intuitive processability map based on Time-Temperature-Transformation plots. The resulting chart allows for the optimum curing conditions that will avoid degradation to be identified. A similar chart for reprocessability has been obtained by considering the exchange kinetics of the characteristic stress relaxation behavior of vitrimers. Furthermore, we have incorporated into the diagrams criteria to determine the critical thickness below which a tolerable thermal gradient is not exceeded. Our diagrams have been experimentally validated, thus proving to be a useful and valid tool for rapid decision-making situations.

Correction: Statistical Comparisons & Correlations of Thermal Analysis, Ultrasonic Velocity and Image Analysis Metallography Methods for Quantification of Ductile Iron Microstructure

Correction: Statistical Comparisons & Correlations of Thermal Analysis, Ultrasonic Velocity and Image Analysis Metallography Methods for Quantification of Ductile Iron Microstructure

Calcination and ion substitution improve physicochemical and biological properties of nanohydroxyapatite for bone tissue engineering applications

Nanohydroxyapatite (nanoHAP) is widely used in bone regeneration, but there is a need to enhance its properties to provide stimuli for cell commitment and osteoconduction. This study examines the effect of calcination at 1200 °C on the physicochemical and biological properties of nanoHAP doped with magnesium (Mg2+), strontium (Sr2+), and zinc (Zn2+). A synergistic effect of dual modification on nanoHAP biological properties was investigated. The materials were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), BET analysis, Fourier-transform spectroscopy, and thermal analysis methods. Furthermore, ion release tests and in vitro biological characterization, including cytocompatibility, reactive oxygen species production, osteoconductive potential and cell proliferation, were performed. The XRD results indicate that the ion substitution of nanoHAP has no effect on the apatite structure, and after calcination, β-tricalcium phosphate (β-TCP) is formed as an additional phase. SEM analysis showed that calcination induces the agglomeration of particles and changes in surface morphology. A decrease in the specific surface area and in the ion release rate was observed. Combining calcination and nanoHAP ion modification is beneficial for cell proliferation and osteoblast response and provide additional stimuli for cell commitment in bone regeneration.

Local Hydrogen Measurements in Multi-Phase Steel C60E by Means of Electrochemical Microcapillary Cell Technique

By utilizing hydrogen as an eco-friendly energy source, many metals are exposed to gaseous (pressurized) hydrogen. High-strength steels with an ultimate tensile strength of 800 MPa and above are especially susceptible to hydrogen-induced fracturing, also referred to as hydrogen embrittlement (HE). Both the microstructure and phase fractions within the steel, as well as lattice distortion, carbide precipitation, residual stress, etc., significantly affect the susceptibility to HE. Among others, one important cause for this observation is found in the locally varying hydrogen solubility within different microstructural phases such as martensite, bainite, pearlite, and ferrite. Both a thorough understanding of the HE mechanisms and taking countermeasures in the form of alloying design require an accurate analysis of local diffusive hydrogen concentrations within the material. Thermal analysis methods such as Thermal Desorption Mass Spectrometry only display an integral hydrogen concentration throughout the whole sample volume. To analyze the local diffusive hydrogen concentration, novel measuring techniques with a high special resolution must therefore be utilized. The current research presents first-of-its-kind hydrogen analyses by means of the electrochemical microcapillary cell. Using a 10 µm tip opening diameter allows for conducting local diffusive hydrogen measurements within individual grains of multi-phase carbon steel C60E (1.1221). The results confirm that hydrogen is distributed heterogeneously within multi-phase steels. Considering the individual phase fractions and the respective local diffusive hydrogen concentrations, a total diffusive hydrogen concentration can be calculated. The obtained value is in good agreement with reference thermal hydrogen analyses. Our results suggest that electrochemical microcapillary cell measurements offer great potential for further studies, which will provide a better understanding of HE and local hydrogen accumulation.