Search Results (121)

This study systematically investigates the homogenization-induced Laves phase dissolution kinetics and recrystallization mechanisms in laser powder bed fusion (L-PBF) processed IN718 superalloy. The as-built material exhibits a characteristic fine dendritic microstructure with interdendritic Laves phase segregation and high dislocation density, featuring directional sub-grain boundaries aligned with the build direction. Laves phase dissolution demonstrates dual-stage kinetics: initial rapid dissolution (0–15 min) governed by bulk atomic diffusion, followed by interface reaction-controlled deceleration (15–60 min) after 1 h at 1150 °C. Complete dissolution of the Laves phase is achieved after 3.7 h at 1150 °C. Recrystallization initiates preferentially at serrated grain boundaries through boundary bulging mechanisms, driven by localized orientation gradients and stored energy differentials. Grain growth kinetics obey a fourth-power time dependence, confirming Ostwald ripening-controlled boundary migration via grain boundary diffusion. Such a study is expected to be helpful in understanding the microstructural development of L-PBF-built IN718 under heat treatments. Full article

Aluminum (Al) alloys exhibit exceptional mechanical properties, seeing widespread use in various industrial fields. Here, we use a multiscale simulation method combining phase field method, dislocation dynamics, and crystal plasticity finite element method to reveal the evolution law of precipitates, the interaction mechanism between dislocations and precipitates, and the grain-level creep deformation mechanism in 7A09 Al alloy under creep loading. The phase field method indicates that Al alloys tend to form fewer but larger precipitates during the creep process, under the dominant effect of stress-assisted Ostwald ripening. The dynamic equilibrium process of precipitate is not only controlled by classical diffusion mechanisms, but also closely related to the local strain field induced by dislocations and the elastic interaction between precipitates. Dislocation dynamics simulations indicate that the appearance of multiple dislocation loops around the precipitate during the creep process is the main dislocation creep deformation mechanism. A crystal plasticity finite element model is established based on experimental characterization to investigate the macroscopic creep mechanism. The dislocation climb is hindered by grain boundaries during creep, and high-density dislocation bands are formed around specific grains, promoting non-uniform plastic strain and leading to strong strain gradients. This work provides fundamental insights into understanding creep behavior and deformation mechanism of Al alloy for deep-sea environments. Full article

Crystalline products with a narrow and uniform distribution of crystals by size (CSD), characterized by a desired average size, are necessary in many practices. Therefore, extensive, but mostly experimental, research is devoted to the problem of obtaining such CSDs. Alternatively, this manuscript presents a theoretical approach for calculating CSD resulting from crystallization in unstirred solutions. First, classical equations for the rates of diffusion-controlled and kinetically controlled growth of crystals are used to discuss the size-dependent growth of the nucleated crystals and the initial CSD (which arises from the non-simultaneous nucleation of crystals). Then, applying the law of conservation of matter, it is proved that the CSD continues to expand during the growth stage. Furthermore, it is substantiated that, due to their uneven spatial distribution, crystals of the same size can grow at different rates. This depends on whether the crystals are outside the diffusion fields of other crystals or are clustered together in “nests”. Moreover, by calculating the growth rates of crystals in “nests”, an explanation is given for the observation that closely spaced crystals are smaller in size than the separately growing crystals. Finally, the CSD established during the Ostwald ripening is discussed quantitatively, step-by-step. Full article

Mesoporous ZnO/ZnCo₂O₄ nanocomposites with excellent gas-sensing performance were synthesized using the Ostwald ripening method. The as-prepared ZnO/ZnCo₂O₄ comprised aggregated monodisperse nanoparticles, and the nanoparticle size grew with increasing thermal treatment temperature. Increasing the calcination temperature did not significantly change the overall size of the ZnO/ZnCo₂O₄ nanocomposites, but the pore size and specific surface area were noticeably affected. The gas-sensing results showed that ZnO/ZnCo₂O₄ composites calcined at 500 °C exhibited the highest response to H₂S at 200 °C, with a detection limit of 500 ppb. The ZnO/ZnCo₂O₄ composites also exhibited remarkable selectivity, response/recovery speed, and stability. Their excellent gas-sensing performance might be attributed to their porous structure, large specific surface area, and the heterogeneous interface between ZnO and ZnCo₂O₄. This work not only represents a new example of the Ostwald ripening-based formation of inorganic hollow structures in a template-free aqueous solution but also provides a novel and efficient sensing material for the detection of H₂S gas. Full article

In this study, we investigated the formation mechanism of organo-metal halide perovskite nanostructures through a two-step process categorized as dissolution–recrystallization. It is proposed that the initial formation of nanostructures is governed by the generation of seed grains, whereas the Ostwald ripening model explains only the subsequent growth stage of these structures. We suggest that newly generated grains—formed adjacent to pre-positioned grains—experience compressive stress arising from volume expansion during the phase transition from PbI₂ to the MAPbI₃ perovskite phase. Owing to their unstable state, these grains may serve as effective seeds for the nucleation and growth of nanostructures. Depending on the dipping time, diverse morphologies such as nanorods, plates, and cuboids were observed. The morphology, including the aspect ratio and growth direction of these nanostructures, appears to be strongly influenced by the residual compressive stress within the seed grains. These findings suggest that the shape and aspect ratio of perovskite nanostructures can be tailored by carefully regulating nucleation, dissolution, and growth dynamics during the two-step process. Full article

Ti₂AlNb-based alloys are widely used in aerospace applications due to their excellent high-temperature mechanical properties. This study aims to investigate the texture, microstructural evolution, and phase transformation behavior of Ti₂AlNb-based alloy sheets during heat treatment and their effects on tensile properties. During heat treatment, B2 → O phase transformation occurs at 550 °C and 650 °C, while Ostwald ripening takes place at 700 °C and 850 °C. The α₂ phase undergoes spheroidization around 1000 °C due to grain boundary separation and recrystallization. Additionally, the B2, O, and α₂ phases all exhibit strong textures. The B2-phase texture follows a cubic orientation ({100}<001>), rotated ~30° around the normal direction (ND). The O-phase texture consists of a strong {100}<010> rolling texture and a weaker texture component <001>//RD, influenced by the B2-phase texture, rolling deformation, and variant selection during O-phase precipitation. Each B2 grain generates four variants, forming distinct O-phase textures within the same grain. The α₂-phase texture exhibits typical rolling textures, [0001]//TD, <$\overline{1}$2$\overline{1}$0>//ND, and {11$\overline{2}$0}<01$\overline{1}$0>, remaining stable after heat treatment. Tensile tests show that the rolled sheet has better ductility along the rolling direction (RD), while the transverse direction (TD) demonstrates higher yield strength (up to 1136 MPa). The anisotropy in tensile properties is mainly attributed to the O-phase texture, with minor contributions from the α₂-phase and B2-phase textures. These findings provide a theoretical basis for optimizing the mechanical properties of Ti₂AlNb-based alloys. Full article

The aim of this study was to investigate the effect of Ostwald ripening inhibitors on D-limonene (D-LMN) nanoemulsions and to elucidate their impact on oral cancer cells. Various inhibitors, including olive oil, soybean oil, and perilla oil, were incorporated into D-LMN nanoemulsions at different ratios (25:75–75:25, D-LMN to inhibitor). The resulting nanoemulsions were evaluated for droplet size, size distribution, zeta potential, stability, droplet morphology, cytotoxicity, antimetastatic and anti-invasive activities, apoptosis induction, and cell cycle arrest. Results showed that the 75:25 D-LMN to inhibitor ratio produced the smallest droplet size and exhibited great stability, particularly with perilla oil. Notably, D-LMN nanoemulsions displayed strong anti-oral cancer effects by reducing cell viability, metastasis, and invasion. Apoptosis was induced, as evidenced by nuclear fragmentation, Annexin V binding, and altered expression of BAX, BCL-XL, Cytochrome c, and Caspase-9. Additionally, the nanoemulsions caused cell cycle arrest via downregulation of Cyclin D1, CDK2, CDK4, and CDK6. These findings highlight the potential of D-LMN nanoemulsions as a promising alternative therapeutic strategy for oral cancer treatment. Full article

Solution processing represents a widely adopted methodology for perovskite solar cell (PSC) fabrication. Nevertheless, the prevalent use of toxic solvents and anti-solvents in conventional approaches presents significant challenges for PSC commercialization. Water, as an environmentally benign solvent with exceptional Pb(NO₃)₂ solubility, offers a promising alternative for perovskite film preparation. However, the sluggish conversion kinetics of Pb(NO₃)₂ to perovskite often results in morphological imperfections and incomplete conversion, particularly detrimental to planar inverted PSCs derived from aqueous solutions, which currently exhibit limited power conversion efficiencies (PCE) of approximately 6%. To mitigate the Ostwald ripening effect induced by slow reaction kinetics and enhance the conversion efficiency of deep-layer Pb(NO₃)₂ and PbI₂, this study proposes a strategy of increasing the pore size in porous Pb(NO₃)₂ structures. Through the incorporation of sodium dodecyl sulfonate (SDS) surfactant into the Pb(NO₃)₂ precursor solution, we successfully fabricated high-quality perovskite films. Comprehensive characterization revealed that SDS doping effectively modified the surface properties of Pb(NO₃)₂ films, accelerating their conversion to perovskite. The optimized PSCs based on SDS-modified perovskite films demonstrated improved energy level alignment, enhanced charge carrier extraction, and suppressed non-radiative recombination. Consequently, the PCE of planar inverted aqueous PSCs increased significantly from 12.27% (control devices) to 14.82% following surfactant modification. After being stored in a nitrogen glove box for 800 h, the performance of the device still remained above 90% of its original level. It can still maintain 60% of its original performance after a 100 h heating aging test at 80 degrees. Full article

Directionally solidified (DS) superalloys have become a primary material choice for turbine blade applications. Due to the complex shape of the blades, certain regions inevitably experience stress axes oriented orthogonally to the crystal growth direction. Therefore, this study explores the creep characteristics of a DS superalloy in different orientations (transverse (T) versus longitudinal (L) with respect to grain growth direction) under intermediate and high temperatures (980 °C and 1070 °C), while simultaneously analyzing their respective deformation mechanisms and microstructural transformation behaviors. Experimental findings reveal pronounced orientation-dependent variations in creep performance, deformation modes, and microstructural development. Notably, the T specimen exhibits higher creep resistance at 980 °C, which can provide a basis for the design of some components that require high creep resistance and maintain small deformation. At 980 °C, L specimens primarily undergo γ′ phase shearing via antiphase boundaries (APBs) pairs, whereas T specimen exhibits APB pairs and superlattice intrinsic stacking faults (SISFs) shearing mechanisms. At 1070 °C, the L specimen exhibits dislocation shearing of γ′ alongside dislocation bypassing of tertiary γ′, while the T specimen demonstrates dislocation climbing within the γ channels. Additionally, the L specimen exhibits significant N-type rafting, while the T specimen shows significant Ostwald ripening characteristics, with an Ostwald ripening rate constant of 1.04 × 10⁻²⁰ m³/h. Full article

Precise control of forging and heat treatment parameters is essential to achieve microstructural homogeneity in turbine disks, ensuring optimal mechanical performance for aerospace applications. This study examines the influence of the hot deformation temperatures on the grain size and γ′ phase characteristics of U720Li alloy following subsequent heat treatments. Samples extracted from a hot-extruded U720Li billet were subjected to isothermal compression within the temperature range of 1100–1130 °C, followed by holding at 1100 °C and 1120 °C for 4 h and air cooling. The results demonstrate that increasing the deformation temperature from 1100 °C to 1120 °C reduces the γ′ phase volume fraction at grain boundaries from 13% to 5%, weakens pinning effects, promotes grain growth during deformation, elevates grain boundary energy, and diminishes stored deformation energy, despite maintaining an equivalent degree of dynamic recrystallization. When the sub-solvus heat treatment temperature was 20 °C below the effective deformation temperature, Ostwald ripening dominated, resulting in a multimodal γ′ phase distribution after cooling. Conversely, when the sub-solvus heat treatment temperature 20 °C exceeded the effective deformation temperature, a significant portion of the intergranular γ′ phase dissolved, leaving a bimodal distribution comprising both large- and small-sized particles. Full article

Developing sustainable and efficient electrocatalysts for the oxygen evolution reaction (OER) is crucial for advancing energy storage technologies. This study explored the dual role of phosphorus as a dopant in carbon matrices and a key component in nickel phosphides (Ni₂P and Ni₁₂P₅), synthesized using dopamine (PDA) and ammonium phosphate as eco-friendly precursors. The phase formation of nickel phosphides was found to be highly dependent on the P/PDA ratio (0.15, 0.3, 0.6, and 0.9), allowing for the selective synthesis of Ni₂P or Ni₁₂P₅. Operando Raman spectroscopy revealed that both phases undergo surface transformation into nickel (oxy)hydroxide species under OER conditions, yet Ni₂P-based catalysts demonstrated superior activity and long-term stability. This enhancement is attributed to efficient electron transfer at the dynamic Ni₂P/NiOOH interface. Additionally, hollow nanostructures formed at intermediate P/PDA ratios (≤0.3) via the Kirkendall effect and Ostwald ripening contributed to an increased specific surface area and micropore volume, further improving the catalytic performance. Electrochemical impedance spectroscopy confirmed reduced interfacial resistance and enhanced charge transport. These findings offer new insights into the rational design of high-performance electrocatalysts and propose a green, tunable synthesis approach for advanced energy conversion applications. Full article

The microstructure and mechanical properties of GNP-reinforced aluminum composites obtained by powder metallurgy and hot extrusion (at 400 °C, 500 °C, and annealing at 3 h at 610 °C), were investigated. It was found that: (i) depending on the processing applied, the composites showed an increase in yield strength (YS) and ultimate strength (US) of up to 283%, and 78%, respectively; (ii) depending on the size of the ex situ GNP and in situ Al₄C₃ reinforcements, two fracture mechanisms are observed: ductile and brittle–ductile; (iii) annealing for 3 h at 610 °C did not improve the mechanical properties; (iv) the plot of YS vs. the volume fraction of the GNP introduced showed a peculiar pattern not been reported so far. Theoretical analysis of the results showed: (1) the major contributor to the YS increase is the Hall–Petch mechanism; (2) the reinforcements contribution to YS, complements that of Hall–Petch; (3) the main contributor to the composite strength is GNP; (4) a critical size of the reinforcement exists, 1.43 nm, at which the YS is maximal, 260 MPa; (5) the increase in the processing temperature and time leads to Ostwald ripening and increase of Al₄C₃ size and deterioration of mechanical properties. Full article

Nanoemulsions are significant for cosmetic products intended for skin care and for health products due to the reduced size (range 20 to 500 nm) of the globules, which avoids processes of instability. They present transparency, fluidity, wettability, and spreadability; increase skin penetration; and have good sensation. The main instability mechanism of nanoemulsions is called Ostwald ripening, responsible for increasing the average diameter of emulsion globules. Sesame Seed Oil (SO) and Raspberry Seed Oil (RO) are indicated as moisturizing agents recently used in the cosmetic industry and for reducing transepidermal water loss, preventing damage to the skin barrier. They contain specific compounds with common properties such as antioxidant, moisturizing, emollient, and photoprotective actions, making them attractive alternative and complementary treatments to soften the process of skin aging. Below, we present the results of this research on the development of nanoemulsions containing Sesame Seed Oil added with Raspberry Seed Oil by the low-energy method. SO nanoemulsions at HLB = 8.0 were obtained with PEG 15 castor oil (A) and PEG 30 castor oil (F.80) and had globule sizes of 50 nm and 200 nm, respectively, along with pH values considered suitable for skin care products and lower viscosity values allowing for the easy application of nanoemulsions to the skin. Nanoemulsions A and F.80 showed antioxidant activities of 68.71% and 67.75%, respectively. SO nanoemulsions with PEG 15 and PEG 30 castor oil were obtained at 85 °C and 75 °C, respectively, and have the lowest Ostwald ripening index (1.33 × 10²² m³ s⁻¹). The in vitro evaluation conducted using the HET-CAM method for nanoemulsions and PEG 15 and PEG 30 castor oils showed that they were slightly irritating and could be used in cosmetic products. Full article

Fungi polysaccharides are nutraceutical-rich compounds with bioactive properties, offering promising applications in food formulation. This study examined the non-covalent complexation of commercial polysaccharides derived from the fruiting bodies of Auricularia auricula-judae (AA) and Ganoderma lucidum (GL) and soy protein isolate to enhance emulsifying properties. Complexes were examined across protein-to-polysaccharide ratios (0:1 to 1:0), pH levels (3 to 7), and heat treatment conditions. Results indicated a maximum insoluble association at pH 4 for both SPI-AAP and SPI-GLP complexes, with SPI-AAP complexes remaining soluble at pH 3, while SPI-GLP complexes exhibited insolubility. Heat treatment had a limited effect on electrostatically driven complexation but resulted in larger particles through a protein-denaturation-induced increase of hydrophobic interactions. In terms of emulsifying properties, individual GLPs demonstrated superior performance compared to individual AAPs. The GLPs engaged in competitive adsorption at the oil–water interface alongside SPI, resulting in larger emulsion droplet sizes compared to either component alone. The association of either AAPs or GLPs with SPI enhanced the emulsion stability against coalescence and Ostwald ripening. Commercial fungal polysaccharides demonstrate substantial potential for incorporation into manufactured food products, particularly in colloidal formulations. Full article

Poor solubility of many drugs, with ensuing low bioavailability, is a big challenge in pharmaceutical development. Nanosuspensions have emerged as a platform approach for long-acting injectables and solid dosages that enhance drug bioavailability. Despite improvements in nanosuspension preparation methods, ensuring nanosuspension stability remains a critical issue. Conventionally, synthetic and semi-synthetic polymers and surfactants are used in nanosuspension formulations. However, no polymer or surfactant group is universally applicable to all drugs. This fact, as well as their toxicity and side effects, especially if used in excess, have sparked the interest of researchers in the search for novel, natural stabilizers. The objective of this paper is to provide a comprehensive analysis of non-traditional natural stabilizers reported in the literature published over the last decade. First, physical stability and stabilization mechanisms are briefly reviewed. Then, various classes of non-traditional natural stabilizers are introduced, with particular emphasis on their stabilization potential, safety, and pharmaceutical acceptability. Wherever data were available, their performance was compared with the traditional stabilizers. Furthermore, the benefits and limitations of using these stabilizers are examined, concluding with future prospects. This review is expected to serve as a valuable guide for researchers and formulators, offering insights into non-traditional natural stabilizers in drug nanosuspension formulations. Full article