Search Results (277)

Background/Objectives: Tegoprazan (TPZ) is a potassium-competitive acid blocker (P-CAB) used to treat conditions such as gastroesophageal reflux disease, peptic ulcer, and Helicobacter pylori infection. It exists in three solid forms: amorphous, Polymorph A, and Polymorph B. This study investigates the molecular basis of polymorph selection, focusing on conformational bias and solvent-mediated phase transformations (SMPTs). Methods: The conformational energy landscapes of two TPZ tautomers were constructed using relaxed torsion scans with the OPLS4 force field and validated by nuclear Overhauser effect (NOE)-based nuclear magnetic resonance (NMR). Hydrogen-bonded dimers were analyzed using DFT-D. Powder X-ray diffraction (PXRD), differential scanning calorimetry (DSC), solubility, and slurry tests were conducted using methanol, acetone, and water. Kinetic profiles were modeled with the Kolmogorov–Johnson–Mehl–Avrami (KJMA) equation. Results: Polymorph A was thermodynamically stable across all analyses. Both amorphous TPZ and Polymorph B converted to A in a solvent-dependent manner. Methanol induced direct A formation, while acetone showed a B → A transition. Crystallization was guided by solution conformers and hydrogen bonding. Conclusions: TPZ polymorph selection is governed by solution-phase conformational preferences, tautomerism, and solvent-mediated hydrogen bonding. DFT-D and NMR analyses showed that protic solvents favor the direct crystallization of stable Polymorph A, while aprotic solvents promote the transient formation of metastable Polymorph B. Elevated temperatures and humidity accelerate polymorphic transitions. This crystal structure prediction (CSP)-independent strategy offers a practical framework for rational polymorph control and the mitigation of disappearing polymorph risks in tautomeric drugs. Full article

This study systematically investigates the impact of hydrolytic degradation on the crystallization kinetics and morphology of poly(butylene succinate-co-adipate) (PBSA). Gel Permeation Chromatography (GPC) confirmed extensive chain scission, significantly reducing the polymer’s weight-average molecular weight (M_w from ~103,000 to ~16,000 g/mol) and broadening its polydispersity index (PDI from ~2 to 7 after 64 days). Differential scanning calorimetry (DSC) analysis revealed that hydrolytic degradation dramatically accelerated crystallization rates, reducing crystallization time roughly 10-fold (e.g., from ~3000 s to ~300 s), and crystallinity increased from 34% to 63%. Multiple melting peaks suggested the presence of lamellae with varying thicknesses, consistent with the Gibbs–Thomson equation. Isothermal crystallization kinetics were evaluated using the Avrami equation (with n ≈ 3), reciprocal half-time of crystallization, and a novel inflection point slope method, all confirming accelerated crystallization; for instance, the slope increased from 0.00517 to 0.05203. Polarized optical microscopy (POM) revealed evolving spherulite morphologies, including hexagonal and flower-like dendritic spherulites with diamond-shape ends, while wide-angle X-ray diffraction (WAXD) showed a crystallization range shift to higher temperatures (e.g., from 72–61 °C to 82–71 °C) and a 14% increase in crystallite diameter, aligning with increased melting point and lamellar thickness and overall increased crystallinity. Full article

The prediction of microstructure evolution during thermal processing plays a crucial role in tailoring the mechanical properties of metallic components. Therefore, this work presents a comprehensive, multiscale modelling approach to simulating phase transformations in large-diameter steel rings during cooling. A finite-element-based thermal model was first used to simulate transient temperature distributions in a large-diameter ring under different cooling conditions, including air and water quenching. These thermal histories were subsequently employed in two complementary phase transformation models of different levels of complexity. The Avrami model provides a first-order approximation of the evolution of phase volume fractions, while a complex full-field cellular automata approach explicitly simulates the nucleation and growth of ferrite grains at the microstructural level, incorporating local kinetics and microstructural heterogeneities. The results highlight the sensitivity of final grain morphology to local cooling rates within the ring and initial austenite grain sizes. Simulations demonstrated the formation of heterogeneous microstructures, particularly pronounced in the ring’s surface region, due to sharp thermal gradients. This approach offers valuable insights for optimising heat treatment conditions to obtain high-quality large-diameter ring products. Full article

Growing requirements in the field of environmental protection and waste management result in the need to search for new and effective methods of recycling various types of waste. From the perspective of technical and natural sciences, the disposal of hazardous waste, which can lead to environmental degradation, is of utmost importance. A particularly hazardous waste is asbestos, used until recently in many branches of the economy and industry. Despite the ban on the production and use of asbestos introduced in many countries, products containing it are still present in the environment and pose a real threat. This paper presents the results of research related to the process of asbestos neutralization, especially the chrysotile variety, by the thermal decomposition method. Changes in the mineralogical characteristics of asbestos waste were studied using the following methods: TG-DTA-EGA, XRD, SEM-EDS and XRF. The characteristics of the chrysotile asbestos sample were determined before and after thermal treatment at selected temperatures. The second part of the study focuses on the kinetic aspect of this process, where the chrysotile thermal decomposition process was measured by two techniques: ex situ and in situ. This study showed that the chrysotile structure collapsed at approximately 600–800 °C through dehydroxylation, and then the fibrous chrysotile asbestos was transformed into new mineral phases, such as forsterite and enstatite. The formation of forsterite was observed at temperatures below 1000 °C, while enstatite was created above this temperature. From the kinetic point of view, the chrysotile thermal decomposition process could be described by the Avrami–Erofeev model, and the calculated activation energy values were ~180 kJ mol⁻¹ and ~220 kJ mol⁻¹ for ex situ and in situ processes, respectively. The obtained results indicate that the thermal method can be successfully used to detoxify hazardous chrysotile asbestos fibers. Full article

High-energy ball milling for different durations was used to synthesize nanocrystalline Mg₆₀Ni₂₅Cu₁₀Ce₅ powders. The morphology and microstructure of the milled powders were investigated by scanning electron microscopy and X-ray diffraction, respectively. It was found that different milling times result in considerably different phase composition. The powder milled for 1 h is characterized by elemental Mg, Ni, Cu and Ce with some minor content of intermetallics. In total, 3 h milling promotes the intensive formation of intermetallic compounds, while 10 h of powder processing results in a partially amorphous state coupled with compound phases. Isothermal hydrogenation and dehydrogenation experiments were conducted in a Sieverts’-type apparatus. It was found that all powders absorb H₂ reversibly, while the shortest milling time provides the best overall capacity. Excellent kinetics without any activation cycle were obtained for the 3 h milled composite, releasing and absorbing 50% of the total hydrogen content within 120 s. Each kinetic measurement has satisfactorily been fitted by the Johnson–Mehl–Avrami function. X-ray diffraction analysis on the dehydrided powders confirmed the complete desorption. Full article

This study investigates the impact of various nucleating agents on the crystallization behavior, thermal stability, and mechanical properties of poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (P3HBHHx) with 6 mol% 3-hydroxyhexanoate (3HHx) units. Nucleating agents, including boron nitride (BN), poly(3-hydroxybutyrate) (PHB), talc, ultrafine cellulose (UFC), and an organic potassium salt (LAK), were incorporated to enhance the crystallization performance. Differential scanning calorimetry (DSC) revealed that BN and PHB significantly increased the crystallization temperature and reduced the crystallization time by half, with BN exhibiting the highest nucleation efficiency. Isothermal kinetics modeled using the Avrami and Lauritzen–Hoffman theories confirmed faster crystallization and reduced nucleation barriers in nucleated samples. Polarized optical microscopy (POM) revealed that the nucleating agents altered the spherulite morphology and increased the growth rates. Under fast cooling, only BN induced crystallization, confirming its superior nucleation activity. Thermogravimetric analysis (TGA) indicated minimal changes in thermal stability, while mechanical testing showed a slight reduction in stiffness without compromising the tensile strength. Overall, BN emerged as the most effective nucleating agent for enhancing the P3HBHHx crystallization kinetics, providing a promising strategy for improving processing efficiency and reducing the cycle times in industrial applications. Full article

Reducing the environmental impact is a key reason for developing recyclable insulation materials for high-voltage industries. In this study, polypropylene (PP) blends were prepared via melt mixing with styrene–ethylene–butylene–styrene (SEBS), a thermoplastic elastomer, to improve breakdown strengths at various cooling speeds. A systematic investigation was conducted to evaluate the influence of crystal size, degree of crystallinity, and nucleation growth rate on the breakdown strength. Crystallization behavior was analyzed using isothermal and non-isothermal methods based on the Avrami model. Increasing SEBS content reduced crystallinity, with the lowest nucleation growth rate observed at 35% SEBS. Breakdown strength correlated with crystallization behavior and was further validated by Weibull distribution method. Notably, PP/SEBS blends containing 35% SEBS exhibited the highest breakdown strength of 66.4 kV/mm at a cooling speed of 10 °C/mm. This improvement reflected a reduction in the degree of crystallinity from 36.0% to 22.9% and the lowest growth rate constant (k) at 35% SEBS. Furthermore, the predicted lifetime of PP/SEBS blend containing 35% SEBS, calculated using the oxidation induction time and the Arrhenius equation, was 42 years. These findings demonstrate that SEBS content and cooling rate effectively modulate crystallization and breakdown strength, enabling recyclable PP/SEBS with XLPE-comparable performance for sustainable high-voltage insulation. Full article

Additive Manufacturing (AM) has become a revolutionary technology in manufacturing, attracting considerable attention in industrial applications recently. It allows for intricate fabrication, reduces material waste, offers design flexibility, and has economic implications. Nonetheless, the residual stresses generated during the AM process and their effects on microstructural evolution and material properties continue to pose significant challenges hindering its advancement. This paper investigates the evolution of microstructures, focusing on texture and grain size as influenced by processing parameters. It examines how these factors affect the performance of multi-phase materials, specifically in terms of elastic modulus, Poisson’s ratio, and yield strength, leading to variations in residual stress through analytical simulation. The authors developed a thermal model that considers heat transfer boundaries and the geometry of the molten pool. They simulated grain size by considering the heating and cooling processes, including thermal stress, the Johnson-Mehl-Avrami-Kolmogorov (JMAK) model, and grain refinement. The texture was simulated using the Columnar-to-Equiaxed Transition (CET) model, thermal dynamics, and Bunge calculations. The self-consistency model determines the properties based on the established texture distribution. Finally, both microstructure-affected and non-affected residual stresses were modeled and compared. Two gaps between microstructure-affected residual stress and non-affected analytical models appear at the depths of 0.02 mm and 0.078 mm. The results indicate that controlling process parameters and optimizing microstructures can effectively reduce residual stresses, significantly enhancing the overall performance of AM components. Hence, this work provides a more accurate analytical residual stress model and lays the foundation for better control of residual stress in the AM industry. Full article

With the rapid technological development in the 21st century, the increasing consumption of electronic devices has led to a rise in the generation of waste electrical and electronic equipment (WEEE) due to the disposal of equipment considered obsolete. A significant portion of these wastes contain printed circuit boards (PCBs), which serve as substrates for the connection of microchips, resistors, capacitors, and other components. These boards are composed of various materials, primarily metals such as copper. Thus, this study investigated the recovery of copper from PCB waste (WPCBs) from computers through alkaline leaching, using EDTA and hydrogen peroxide at temperatures of 40 °C, 60 °C, and 80 °C, with a concentration of 0.6 mol/L and varying particle sizes. Using a UV-VIS spectrophotometer, it was observed that the copper extraction process with EDTA at 0.6 mol/L and a temperature of 60 °C achieved a recovery rate of 78.6% for particles smaller than 0.177 mm after 180 min, following the Avrami kinetic model. The results highlight the potential of EDTA as a complexing agent in copper extraction, positioning it as a promising technique to reduce environmental contamination and recover strategic resources through urban mining through the recovery of metals from WEEE. Full article

For many years, countries around the world have been struggling with the problem of storing asbestos waste, especially in, those countries where the production and use of asbestos products have been legally banned. Following the adoption of plans for cleaning up asbestos waste, countries are struggling with the problem of its disposal, which mainly involves storing it in specialist landfills. At the same time, scientists are looking for alternatives to this type of “disposal” of asbestos by developing methods for degrading the harmful fibers. Particular attention has been paid to methods based on the thermal treatment of this waste, which results in hazardous asbestos fibers being thermally decomposed. This work focuses on the kinetic study of the thermal decomposition process of cement–asbestos using an exsitu thermal treatment. The results obtained made it possible to interpret this thermal transformation kinetically. Kinetic analysis of the isothermal data using an Avrami–Erofeev model yielded values for the overall reaction order. On this basis, the value of the apparent activation energy of the thermal decomposition process of the tested cement–asbestos samples was obtained, which was approximately 140–180 kJ mol⁻¹. Full article

Zr₄₈Cu_47.5Al₄Co_0.5 bulk amorphous alloy composites were prepared by selective laser melting (SLM) technology under different processing conditions and their non-isothermal crystallization behaviors were systematically investigated. The results show that the crystallization phases are Cu₁₀Zr₇ and CuZr₂ for both gas-atomized powder and SLMed samples. The dependence of volume fraction of Cu₁₀Zr₇ and CuZr₂ on laser energy density can be fitted by an exponential function. The crystalline sizes of Cu₁₀Zr₇ and CuZr₂ linearly increase with increasing energy density. The thermal stability is larger for the gas-atomized powders than for the SLMed bulk samples. It is interestingly found that there is an exponential relationship between the crystallization enthalpy ΔH_x and the amorphous content. In addition, the glass transition is more difficult for the gas-atomized powders than for the SLMed bulk samples. The crystallization procedure is more difficult for the SLMed bulk samples than for the gas-atomized powders. The local activation energy E_α decreases with increasing α for the gas-atomized powder and the SLMed bulk samples. In addition, the E_α is larger for the SLMed bulk samples than for the gas-atomized powder at the corresponding crystallization fraction α. The dependence of the local Avrami exponent n(α) on the α is similar for both the gas-atomized powders and the SLMed bulk samples at studied heating rates. The crystallization mechanism is also discussed. Full article

The development of sustainable waste management for environmental remediation has highlighted the potential of biochar produced from agricultural wastes as an effective adsorbent for gas pollutant capture. This work focuses on the production and activation of biochar derived from pistachio shells for CO₂ and H₂S adsorption. Adsorbents were obtained by pyrolysis and subsequently activated through two methods: chemical activation with KOH and physical activation with CO₂. Adsorption studies were conducted to evaluate the influence of these activation methods on textural properties and adsorption capacities. Chemical activation enhanced microporosity and increased the specific surface area (531 m²/g), resulting in a better performance, obtaining adsorption capacities of 87 mgCO₂/g_adsorbent and 9.6 mgH₂S/g_adsorbent. Non-linear kinetic models were identified as the most suitable for fitting CO₂ adsorption data, with the Avrami model presenting the best fit results. Dynamic H₂S adsorption tests revealed the influence of moisture present in the adsorbent, favoring H₂S dissociation and thus improving capture processes, especially when chemical activation biochar is employed. This enhancement is attributed to the greater development of active centers on its surface, including micropores and heterogeneous atoms introduced though impregnation. Full article

Nanoscale Cu-rich precipitates (CRPs) play a crucial role in the irradiation embrittlement of reactor pressure vessels (RPVs), and binary Fe-Cu alloys serve as practical models to study the evolution of these precipitates. This study investigates the electrical resistivity of an Fe-1.17 wt.% Cu model alloy aged at 450 °C to enhance the understanding of electrical measurements for the non-destructive assessment of RPV irradiation embrittlement. Multi-level characterization methods were used to obtain quantitative data on multi-scale microstructures, including precipitates, dislocations, and grains. The formation and growth of CRPs were found to align closely with the Johnson–Mehl–Avrami model, and the variation in electrical resistivity showed a strong correlation with the evolution of the microstructure. Combined with detailed quantitative microstructure evolution analysis, an electrical resistivity prediction model that considers microstructural mechanisms has been developed. This model can accurately show the effect of CRPs on resistivity and can potentially be extended to RPV steels with other solute-rich precipitates, with a maximum absolute percentage error not exceeding 5%. These results provide a robust basis for the non-destructive and in-service evaluation of RPV irradiation embrittlement using electrical resistivity. Full article

This note aims for a non-local extension of the Johnson–Mehl–Avrami–Kolmogorov (JMAK) kinetic equation, describing solid phase transformation through the implementation of the time-fractional Caputo derivative and Mittag-Leffler function instead of the exponential Avrami kinetics. These are preliminary results that include tests on some published data and a clarification of the concept. Full article

In this research, fully biobased composites consisting of poly(butylene 2,5-furandicarboxylate) (PBF) and cellulose nanocrystals (CNC) were successfully prepared through a common solution and casting method. The influence of CNC on the crystallization behavior, mechanical property, and hydrophilicity of PBF was systematically investigated. Under different crystallization processes, the crystallization of PBF was obviously promoted by CNC as a biobased nucleating agent. The Ozawa equation was not suitable to fit the nonisothermal melt crystallization kinetics of PBF and PBF/CNC composites. The nucleation activity of CNC was quantitatively calculated by the Dobreva method; moreover, the nucleation efficiency of CNC was further evaluated through the self-nucleation procedure. The isothermal melt crystallization kinetics of PBF and PBF/CNC composites was well described by the Avrami method; moreover, the crystallization mechanism and the crystal structure of PBF remained unchanged despite the presence of CNC. CNC also greatly enhanced both the mechanical property and hydrophilicity of PBF in the composites. In sum, low loadings of CNC simultaneously improved the crystallization, mechanical property, and hydrophilicity of PBF, which should be of significant importance and interest in fully biobased polymer composites from a sustainable viewpoint. Full article