Search Results (126)

This study provides a novel experimental setup and methodology for the quantitative investigation of evaporation-induced foaming behaviors in a polymer/small-molecule solution system (PSMS). In traditional dynamic test methods, it is difficult to precisely describe the evaporation-induced foaming process of a multicomponent solution because the concentration of light components in solution continuously decreases during ebullition, causing undesired changes in foaming behavior. In this study, a precisely controlled condensation reflux module was introduced into the setup to maintain pressure, temperature, and concentration of the PSMS at constant levels during the entire ebullition process, allowing dynamic test methods to quantify the evaporation-induced foamability. With this newly proposed device, experimental data of typical PSMS, polyolefin elastomer (POE)/n-hexane solution system, were obtained and modeled to illustrate the foam growth profile, thereby characterizing the dynamic foaming process based on a logistic growth function. The corresponding dimensionless number Σevap was calculated to evaluate evaporation-induced foam stability by analyzing the foam growth profile under varying pressure, concentration, and energy input levels. Furthermore, given that the PSMS represents a highly non-ideal system, the bubble nucleation rate J was modified in this work by introducing a correction coefficient δ to account for the non-ideal effects of macromolecules present in solutions. Additionally, another correction coefficient λ was incorporated into the Gibbs free energy term to adjust for supersaturation of liquid during nucleation. The experiment’s data align well with the modified bubble nucleation rate mechanism proposed herein. Full article

This study provides new insight into the mechanisms governing solid state dewetting (SSD) in SiGe alloys and underscores the potential of this bottom-up technique for fabricating self-organized defect-free nanostructures for CMOS-compatible photonic and nanoimprint applications. In particular, we investigate the SSD of Si_1−xGe_x thin films grown by molecular beam epitaxy on silicon-on-insulator (SOI) substrates, focusing on and clarifying the interplay of dewetting dynamics, strain elastic relaxation, and SiGe/SOI interdiffusion. Samples were annealed at 820 °C, and their morphological and compositional evolution was tracked using atomic force microscopy (AFM), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), and Raman spectroscopy, considering different annealing time steps. A sequential process typical of the SiGe alloy has been identified, involving void nucleation, short finger formation, and ruptures of the fingers to form nanoislands. XRD and Raman data reveal strain relaxation and significant Si-Ge interdiffusion over time, with the Ge content decreasing from 29% to 20% due to mixing with the underlying SOI layer. EDX mapping confirms a Ge concentration gradient within the islands, with higher Ge content near the top. Full article

This study systematically investigates the influence mechanism of the element Cr on the mechanical properties of the heat-affected zone in pipeline steels for supercritical CO₂ transportation. Microstructural evolution in the heat affected-zone was characterized through thermal simulation tests, Charpy impact testing (−10 °C), and microhardness measurements, complemented by multiscale microscopic analyses (optical microscopy, scanning electron microscopy, electron backscatter diffraction, and transmission electron microscopy). The results demonstrate that Cr addition enhances the base metal’s resistance to supercritical CO₂ corrosion but reduces its low-temperature impact toughness from 277 J to 235 J at −10 °C. Notably, the intercritical heat-affected zone exhibits severe embrittlement, with impact energy plummeting from 235 J (base metal) to 77 J. Microstructural analysis reveals that Cr interacts with carbon to form stable carbonitride particles, which reduce the free carbon concentration and diffusion coefficient in austenite, thereby inducing heterogeneous austenitization. Undissolved carbonitrides pin grain boundaries, creating carbon concentration gradients. During rapid cooling, these localized carbon-enriched microregions preferentially transform into core–shell-structured M-A constituent, characterized by a micro-twin containing retained austenite core encapsulated by high hardness lath martensite. The synergistic interaction between micro-twins and interfacial thermal mismatch stress induces localized stress concentration, triggering microcrack nucleation and subsequent toughness degradation. Full article

The practical implementation of transition state theory (TST) commonly assumes equivalence between theoretical and experimentally determined rate constants, represented by Arrhenius parameters—the activation energy and pre-exponential factor. Here, we employed the General Rate Equation (GRE) to analyse solid–gas-phase thermolysis in two paradigms: mass loss (e.g., calcite decomposition) and mass gain (e.g., methane pyrolysis leading to solid carbon formation). By partitioning the Gibbs free energy of activation into forwards and reverse contributions, plus an additional term accounting for concurrent physical phenomena (notably nucleation and diffusion-viscosity effects), we derived an empirical universal expression relating both Arrhenius parameters and $∆G^{+}$ across 500–1500 K. We further demonstrate the utility of the isokinetic temperature for interpreting cases where only Kinetic Compensation or Enthalpy–Entropy Compensation effects are observed. This framework unifies kinetic and thermodynamic descriptions of complex thermolysis processes. Full article

Background: Metastable zone width (MSZW) and solubility are crucial for developing crystallization procedures in the purification of active pharmaceutical ingredients (APIs). Traditionally, determining these properties involves labor-intensive methods that can take weeks or even months. With advancements in process analytical technologies (PAT) and the increasing focus on quality by design (QbD) in pharmaceutical manufacturing, more efficient and reliable protocols are needed. In this study, we employ in situ Fourier Transform Infrared (FTIR) spectroscopy and Focused Beam Reflectance Measurement (FBRM) to establish protocols for measuring solubility at different temperatures and MSZW at varying cooling rates. Methods: We experimentally determined MSZW and solubility using FTIR spectroscopy and FBRM. IR spectra were analyzed to obtain solubility concentrations, while FBRM counts were used to extract MSZW and supersolubility concentrations. The collected data were assessed using four theoretical models, including a newly developed model based on classical nucleation theory. By fitting experimental MSZW data to these models, we determined nucleation kinetics and thermodynamic parameters. Results: Our novel model exhibited excellent agreement with experimental MSZW data across different cooling rates, demonstrating its robustness. The nucleation rate constant and nucleation rate ranged between 10²¹ and 10²² molecules/m³·s. The Gibbs free energy of nucleation was calculated as 3.6 kJ/mol, with surface energy values between 2.6 and 8.8 mJ/m². The estimated critical nucleus radius was in the order of 10⁻³ m. Conclusions: The protocols we developed for predicting MSZW and solubility of paracetamol using PAT can serve as a guideline for other APIs. Our theoretical model enhances the predictive accuracy of nucleation kinetics and thermodynamics, contributing to optimized crystallization processes. Full article

Based on the literature data, including our published paper on the thermal decomposition of solids, research regarding the possibility of balancing free energy of activation against Gibbs free energy was extended. The importance of nucleation accompanying the thermal decomposition reaction/process was established. For calcite, a symmetrical model was considered for the formation of the active state, followed by the formation into the solid, crystalline decomposition product CaO. When the decomposition is chemical in nature, we do not identify nucleation processes. This is determined by the forwards–backwards balance compatibility, and when an additional term appears, a reversible structural transformation is to be expected. An excess free energy model was proposed to determine the rate constant of activation. It is shown that the results of tests under dynamic conditions allow, with a good approximation, the determination of this quantity as tending towards a maximum rate constant equal to the Arrhenius pre-exponential factor. The solid product of the thermal decomposition of calcite is of great developmental importance, currently utilized for Calcium Looping (CaL) or for Carbon Capture and Storage (CCS) technologies using a reversible reaction of carbonation. Full article

Laser conversion of commercial polymers to laser-induced graphene (LIG) using inexpensive and accessible CO₂ lasers has enabled the rapid prototyping of promising electronic and electrochemical devices. Frequently used to pattern interdigitated supercapacitors, few approaches have been developed to pattern batteries—in particular, full cells. Herein, we report an LIG-based approach to a planar, interdigitated Li-S battery. We show that sulfur can be deposited by selective nucleation and growth on the LIG cathode fingers in a supersaturated sulfur solution. Melt imbibition then leads to loadings as high as 3.9 mg/cm² and 75 wt% sulfur. Lithium metal anodes are electrodeposited onto the LIG anode fingers by a silver-seeded, pulse-reverse-pulse method that enables loadings up to 10.5 mAh/cm² to be deposited without short-circuiting the interdigitated structure. The resulting binder/separator-free flexible battery achieves a capacity of over 1 mAh/cm² and an energy density of 200 mWh/cm³. Unfortunately, due to the use of near stoichiometric lithium, the cycle-life is sensitive to lithium degradation. While future work will be necessary to make this a practical, flexible battery, the interdigitated structure is well-suited to future operando and ex situ studies of Li-S and related battery chemistries. Full article

The confinement-induced liquidlike-to-solidlike phase transition is a well-documented phenomenon observed in both experimental and computational settings. In order to better understand the kinetics and thermodynamics of this process, this study uses molecular dynamics (MD) simulations employing four different methods to examine the nucleation rate of crystalline argon from a confined liquidlike state between two solid walls. The results demonstrate that all four methods produce the same nucleation rate within a factor of two. By analyzing the mean first-passage time (MFPT) and steady-state probability distribution of the largest cluster, the free energy barrier of nucleation is also extracted, which is in the same order of magnitude as $k_{B}T$. These findings quantitatively explain why confinement-induced solidification is observed in direct brutal-force MD simulations and can occur simultaneously as the confinement approaches a critical thickness. This study also provides insight into the nature of heterogeneous nucleation in nanoconfinement. Full article

To obtain high-quality grain refiner, a new Al-5Ti-1B-1RE master alloy grain refiner was synthesized by the melt-matching method. Its microstructure and refining effect, refining properties, and refining mechanism were analyzed. The experimental results show that the second-phase particles of Al-5Ti-1B-1RE master alloy are mainly TiB₂, Al₃Ti, Ti₂Al₂₀RE, etc. The magnitude of the free energy ΔG of the synthesis reaction is calculated to be ΔG_TiB2 < ΔG_Al3Ti < ΔG_Ti2Al20RE. The nucleation rate N mainly depends on the kinetic atomic diffusion activation energy Q and the thermodynamic nucleation work. The microstructure of commercial pure aluminum refined by the new grain refiner has almost transformed from coarse columnar crystals to fine equiaxed crystals, with an average grain size of 70.2 μm, which was 36.18% and 20.66% smaller than that refined by domestic and imported Al-Ti-B wire master alloy grain refiner, its mechanical properties of tensile strength σ_b were increased by 11.94% and 8.29%, and elongation δ was improved by 31.79% and 17.41%, respectively. The main refinement mechanism is the formation of TiAl₃ on TiB₂ particles and the release of RE atoms from the Ti₂Al₂₀RE phase, which in turn is partially transformed into the TiAl₃ phase, which promotes dual nucleation refinement. Full article

The gypsum crystals (CaSO₄·2H₂O) crystallizes in a low symmetry system (monoclinic) and shows a marked layered structure along with a perfect cleavage parallel to the {010} faces. Owing to its widespread occurrence, as a single or twinned crystal, here the gypsum equilibrium (E.S.) and growth shapes (G.S.) have been re-visited. In making the distinction among E.S. and G.S., in the present work, the basic difference between epitaxy and homo-taxy is clearly evidenced. Gypsum has also been a fruitful occasion to recollect the general rules concerning either contact or penetration twins, for free growing and for twinned crystals nucleating onto pre-existing substrates. Both geometric and crystal growth aspects have been considered as well, by unifying theory and experiments of crystallography and crystal growth through the intervention of ${\mathsf{\beta }}_{\mathrm{adh}}$, the physical quantity representing the specific adhesion energy between gypsum and other phases. Hence, the adhesion energy allowed us to systematically use the Dupré’s formula. In the final part of the paper, peculiar attention has been paid to sediments (or solution growth) where the crystal size is very small, in order to offer a new simple way to afford classical (CNT) and non-classical nucleation (NCNT) theories, both ruling two quantities commonly used in the industrial crystallization: the total induction times (${\mathrm{t}}_{\mathrm{i}\mathrm{n}\mathrm{d}}^{\mathrm{t}\mathrm{o}\mathrm{t}\mathrm{a}\mathrm{l}}$) and crystal size distribution (CSD). Full article

The effect of cerium content (0, 0.011, 0.017, 0.075 wt%) on non-metallic inclusions and solidification microstructures of 55SiCr high-strength spring steel was experimentally studied, along with thermodynamic calculations. The results show that Ce addition changes the type and size of inclusions in this steel and influences the characteristics of the solidification microstructure. In the sample without Ce addition, the main inclusions are MnS, SiO₂, SiO₂–MnS, and CaO–SiO₂–MgO, and the equiaxed ratio in the solidification structure is 44.63%. However, when Ce content increases to 0.011 wt%, the inclusions in the steel become mainly Ce–S, Ce–O–S, and a small amount of MnS, and the equiaxed ratio increases to 50.42%. As the Ce content increases to 0.017 wt%, the inclusions are predominantly Ce–S, Ce–O–S, and Ce–O–S–Ca, while some Ce–P and Ce–O–P–C inclusions are also observed. The equiaxed ratio increases to 67.63%, showing the best effect on heterogeneous nucleation during solidification. When Ce content in the steel reaches 0.075 wt%, the Ce-containing inclusions are Ce–S, Ce–O, Ce–P, Ce–P–O, and Ce–O–S–As, and the size becomes larger. The formation mechanism of inclusions is explained by Gibbs free energy calculations and thermodynamic diagrams. Full article

The pores in lotus-type porous copper are formed due to the difference in hydrogen solubility between the liquid and solid phases of copper. In a pressurized hydrogen atmosphere, hydrogen gas is released at the gas release and crystallization temperature, which is the melting point of copper. This study systematically analyzes the effects of process parameters, including hydrogen ratio, total pressure, and continuous casting speed, on the pore structure of lotus-type porous copper, with the aim of identifying the most critical process parameters for controlling pore diameter and density. Within the hydrogen ratio up to 50%, it was observed that as the hydrogen ratio increases, the pores tend to increase in porosity, and the pore diameter increases. As the hydrogen ratio increased from 25% to 50%, the pore diameter increased from 300 μm to 400 μm, while the pore density decreased from 3.3 N·mm⁻² to 2.8 N·mm⁻². As the total pressure increased, the pore diameter tended to decrease, and the pore density increased. Specifically, when the total pressure increased from 0.2 MPa to 0.4 MPa, the pore diameter decreased from 1100 μm to 400 μm, while the pore density increased significantly from 0.5 N·mm⁻² to 2.8 N·mm⁻². In addition, as the continuous casting speed increased, 30 to 90 mm·min⁻¹, the pore diameter decreased from 850 μm to 400 μm, and the pore density increased from 0.7 N·mm⁻² to 2.8. N·mm⁻². Specifically, the increase in total pressure led to a decrease in Gibbs free energy and a reduction in the critical pore nucleation radius, which promoted pore formation and resulted in the creation of more, smaller pores. These results suggest that total pressure is the primary factor influencing both pore diameter and density in lotus-type porous copper. Full article

Anode-free lithium batteries (AFLBs) present an opportunity to eliminate the need for conventional graphite electrodes or excess lithium–metal anodes, thus increasing the cell energy density and streamlining the manufacturing process. However, their attributed poor coulombic efficiency leads to rapid capacity decay, underscoring the importance of achieving stable plating and stripping of Li on the negative electrode for the success of this cell configuration. A promising approach is the utilization of lithiophilic coatings such as silver to mitigate the Li nucleation overpotential on the Cu current collector, thereby improving the process of Li plating/stripping. On the other hand, inkjet printing (IJP) emerges as a promising technique for electrode modification in the manufacturing process of lithium batteries, offering a fast and scalable technology capable of depositing both thin films and patterned structures. In this work, a Fujifilm Dimatix inkjet printer was used to deposit Ag sites on a Cu current collector, aiming to modulate the interfacial electrochemistry of the system. Samples were fabricated with varying areas of coverage and the electrochemical performance of the system was systematically evaluated from bare Cu (non-lithiophilic) to a designed pattern (partially lithiophilic) and the fully coated thin film case (lithiophilic). Increasing lithiophilicity resulted in lower charge transfer resistance, higher exchange current density and reduced Li nucleation overpotential (from 55.75 mV for bare Cu to 13.5 mV for the fully coated case). Enhanced half-cell cyclability and higher coulombic efficiency were also achieved (91.22% CE over 76 cycles for bare Cu, 97.01% CE over 250 cycles for the fully coated case), alongside more uniform lithium deposition and fewer macroscopic irregularities. Moreover, our observations demonstrated that surface patterning through inkjet printing could represent an innovative, easy and scalable strategy to provide preferential Li nucleation sites to guide the subsequent Li deposition. Full article

Polymorphic transformation is important in chemical industries, in particular, in those involving explosive molecular crystals. However, due to simulating challenges in the rare event method and collective variables, understanding the transformation mechanism of molecular crystals with a complex structure at the molecular level is poor. In this work, with the constructed order parameters (OPs) and K-means clustering algorithm, the potential of mean force (PMF) along the minimum free-energy path connecting β-HMX and δ-HMX was calculated by the finite temperature string method in the collective variables (SMCV), the free-energy profile and nucleation kinetics were obtained by Markovian milestoning with Voronoi tessellations, and the temperature effect on nucleation was also clarified. The barriers of transformation were affected by the finite-size effects. The configuration with the lower potential barrier in the PMF corresponded to the critical nucleus. The time and free-energy barrier of the polymorphic transformation were reduced as the temperature increased, which was explained by the pre-exponential factor and nucleation rate. Thus, the polymorphic transformation of HMX could be controlled by the temperatures, as is consistent with previous experimental results. Finally, the HMX polymorph dependency of the impact sensitivity was discussed. This work provides an effective way to reveal the polymorphic transformation of the molecular crystal with a cyclic molecular structure, and further to prepare the desired explosive by controlling the transformation temperature. Full article

A new type of SiC_f/TiC-Ti₃SiC₂ composite was prepared by the Spark Plasma Sintering (SPS) method in this work. The phase transformation and interface cracking of this composite under ion irradiation (single Xe, Xe + He, and Xe + He + H ions) and subsequent annealing were analyzed using transmission electron microscopy (TEM), mainly focusing on the interface regions. Xe ion irradiation resulted in the formation of high-density stacking faults in the TiC coatings and the complete amorphization of SiC fibers. The implanted H ions exacerbated interface coarsening. After annealing at 900 °C for 2 h, the interface in the Xe + He + H ion-irradiated samples was seriously damaged, resulting in the formation of large bubbles and cracks. This damage occurred because the H atoms reduced the surface free energy, thereby promoting the nucleation and growth of bubbles. Due to the absorption effect of the SiC_f/TiC interface on defects, the SiC fiber areas near the interface recovered back to the initial nano-polycrystalline structure after annealing. Full article