Journal of Thermal Analysis and Calorimetry最新文献

Ni-based layered double hydroxides (LDHs) are well-known as catalysts precursors; in fact, their properties allow for a homogeneous distribution of Ni on a matrix through simple and economic synthetic passages. In this work, NiAl-citrate LDH was synthetized through a recently developed synthetic pathway that led to the formation of almost single-layered hexagonal nanocrystals. These ones seem to be promising for the production of a Ni (0)-based material with a very high surface area, since through pyrolysis, the interlayered citrate could be turned into CO that simultaneously reduces the Ni (II) to Ni (0) and blow-up the original crystals. In this transformation, temperature plays a key role; therefore, the processes occurring during heating were investigated to discriminate which of them contribute to the material reduction. Additionally, the appropriate pyrolysis temperature was determined to achieve the desired compound that was a homogeneous distribution of nanopatterned micro-flakes of Ni (0) and Al/Ni mixed oxides, with a high specific surface area (177m²g⁻¹). The high surface area and the expected properties of this new material make it an interesting candidate for heterogeneous catalysis of high-temperature gas reactions, such as dry reforming, a noteworthy process that produces syngas from the two greenhouse gases CO₂ and CH₄. DRM applicability is limited by high temperatures required to obtain acceptable conversion and by solid carbon deposition on catalyst, both leading to its deactivation over time; so, it is important to develop new catalysts able to overcome those problems. For these purposes, some preliminary tests on the obtained material were performed confirming its catalytic behavior for the DRM, especially at temperatures > 800 K.

Gestrinone is an active pharmaceutical ingredient used in the treatment of endometriosis as capsules, with ongoing evaluation for intravaginal administration, while also having been studied for its potential antitumoral effects. The purpose of this study was to determine the compatibility of gestrinone with four excipients used in the development of solid pharmaceutical formulations (α-lactose monohydrate, magnesium stearate, starch, and talc) and to obtain a fully characterized thermoanalytical profile of gestrinone with the help of kinetic analysis. Preformulation studies were carried out on 1:1 mass/mass binary mixtures between gestrinone and each excipient by instrumental screening under ambient conditions using ATR-FTIR spectroscopy investigations, and later by studying the effect of thermal treatment over the samples (TG/DTG/DSC). The obtained results suggest that under ambient conditions, no chemical interactions take place between the active pharmaceutical ingredient and selected excipients, whereas under thermal stress incompatibilities are observed in all systems. The mechanism of decomposition was preliminary evaluated by the ASTM E698 and later completed by the isoconversional methods of Friedman, Kissinger–Akahira–Sunose, and Flynn–Wall–Ozawa, which suggest similar mean activation energies. The mechanism of decomposition was elucidated in the last part of the study, by employing the modified NPK method. This method suggests that gestrinone is thermally degraded by the contribution of two individual processes, both consisting of superimposed physical transformations and chemical degradations.

This review aims to analyze recent advancements in heat pump dryers (HPDs) with a focus on improving energy efficiency and conservation in drying processes. The objective is to evaluate the components, structures, and refrigerants used in HPDs, examining their environmental impacts and system performance. The methodology includes a comprehensive comparison of various assisted HPD systems, such as infrared-, ultrasound-, and solar-assisted technologies, to assess their experimental benefits and limitations. By using key performance metrics, the paper evaluates the energy efficiencies of HPDs in comparison with traditional drying methods, discussing their applications across different industries. The study also explores the significance of integrating alternative energy sources to enhance the efficiency and economic viability of HPDs. Future research directions are proposed to further develop the technology for commercial use, emphasizing HPDs’ potential to provide energy-efficient and high-quality drying solutions. In quantitative terms, the review notes that the coefficient of performance (COP) for HPDs ranges between 3.5 and 4.5, indicating a significant improvement over traditional drying methods. Specific moisture extraction rate (SMER) values for HPDs are reported to be between 0.8 and 1.2 kg kW⁻¹ h⁻¹, demonstrating superior efficiency in moisture removal. Additionally, specific energy consumption (SEC) for HPDs is found to be 0.5–0.7 kW h kg⁻¹ of evaporated moisture, which is substantially lower compared to conventional dryers. These metrics underscore the energy-saving potential and enhanced performance of HPD technology.

The technology known as organic rankine cycle (ORC) is a dependable method for transforming heat into electricity, whether it is for use in renewable energy sources such as biomass, geothermal, and solar, or for improving industrial energy efficiency. The range of ORC systems spans from small-scale (a few kW) for home cogeneration to sizable multi-megawatt geothermal power facilities. Since the 1970s, technology has undergone significant progress, largely due to increased economic incentives and rising energy costs, despite a slow start initially. Tracking the evolution of the technology worldwide is challenging due to the wide variety of applications, manufacturers, and countries involved. Hence, the present research scrutinizes the ORC technology to evaluate this system from the energy and economic perspectives. Aspen HYSYS, and Aspen Capital Cost Estimator simulations were used for the process, thermodynamic, and financial evaluations, respectively. In this research, the ORC is evaluated using various organic working fluids, specifically seven different types of fluids. The power and heat flow of the expander in all scenarios are considered at 1200 kW and 1.200 Mw, respectively, to determine the most appropriate organic fluid. Organic fluid toluene, due to its highest boiling point among the investigated fluids, was able to generate the required production power using the lowest molar flow rate for both input and output to the expander, considering these values. The results showed that the organic fluid toluene is technically and economically superior to other fluids. However, cyclopentane performs slightly better in terms of energy consumption and carbon dioxide output. However, toluene is chosen over cyclopentane due to current safety concerns.

Sartans, also known as angiotensin receptor blockers, comprise a category of antihypertensive medications designed to inhibit the actions of angiotensin II (Ang II) in the body, ultimately reducing blood pressure levels. This class of compounds is derived from 2-(1-benzyl-1H-imidazol-5-yl)-acetic acid, with its origin characterized by an imidazole core that underwent various substitutions at specific positions within the heterocyclic nucleus. We investigated the behavior of Losartan, Valsartan and Irbesartan and their compatibility with various excipients used in pharmaceutical tablet formulations by FTIR spectroscopic studies, thermal behavior by thermogravimetry and differential scanning calorimetry. The aim of the study was to determine the excipients to be used in pharmaceutical formulations containing drugs from the class of sartans as active ingredients. Our study concludes by recommending precautionary measures in elaborating new solid formulations containing lactose in the case of Losartan.

In this paper, a simulation is performed on nanofluids flow with double-diffusive natural convection. The enclosure is hexagonal, and hot obstacles of various shapes are placed inside it. The partial differential equations governing fluid flow and heat and mass transfer are solved using the finite element method. Mass diffusion, characterized by the Lewis number (Le), is a significant parameter affecting the behavior of two-phase flow. This parameter is the most influential parameter in concentration distribution. Temperature, velocity, and concentration fields inside the enclosure are analyzed using temperature, velocity, and concentration contours. The results of this study show that increasing the Le from 1 to 5 causes a reduction in the (overline{{{text{Nu}}}}) by 11.23%, 11.7%, 11.95%, and 11.03% and an increase in the (overline{{{text{Sh}}}}) by 64.41%, 70.82%, 69.64%, and 69.60% for circular, triangular, rectangular, and rhombus obstacles, respectively. Increasing the aspect ratio (AR) from 0.1 to 0.3 leads to an increase in the (overline{{{text{Nu}}}}) by 49%, 36%, 33.7%, and 45.3% and an increase in the (overline{{{text{Sh}}}}) by 48.8%, 39.4%, 44.3%, and 47.6% for circular, triangular, rectangular, and rhombus obstacles, respectively. The average Be decreases with an increase in the AR and increases with an increase in the Le. Increasing the Le leads to a decrease in fluid entropy generation (ENT) and total ENT but increases the AR, which increases fluid ENT and total ENT. However, the change in both thermal ENTs did not result in any significant change.