Search Results (453)

The mechanical behavior of metallic core–shell nanoparticles is critical for their use as reinforcement particles and additive manufacturing feedstocks, yet their deformation mechanisms remain incompletely understood. This study employs molecular dynamics simulations to investigate the compressive response of a Cu-core/Al-shell nanoparticle and compares it with solid Cu, solid Al, and a hollow Al shell of the same size under uniaxial loading along ⟨100⟩, ⟨110⟩, ⟨111⟩, and ⟨112⟩ directions. The single-material nanoparticles show strong anisotropy: solid Cu exhibits orientation-dependent transitions from dislocation slip to deformation twinning, while introducing a void to form a hollow Al shell reduces stiffness and strength, confines plasticity to the shell wall, and suppresses extended load-bearing twins. The Cu–Al core–shell nanoparticle combines these behaviors in an orientation-dependent manner. Under ⟨110⟩ and ⟨112⟩ loading, deformation is largely shell-dominated, whereas ⟨100⟩ and ⟨111⟩ loading more strongly activates the Cu core. Mechanistically, ⟨100⟩ is characterized by Shockley partial activity and junction/lock formation in the Al shell coupled with twinning in the Cu core; ⟨110⟩ shows primarily shell partials with limited core involvement; ⟨111⟩ promotes partial-dislocation activity in both shell and core; and ⟨112⟩ produces localized, twin-dominated bands in the Al shell with shell-thickness-dependent twin extension into the Cu core. These trends are rationalized using Schmid factor considerations for $\left\{111\right\}⟨110⟩$ slip and $\left\{111\right\}⟨112⟩$ partial/twinning shear, together with the effects of faceted free surfaces and the Cu–Al interface. The core–shell geometry enables two concurrent interface-mediated pathways, i.e., (i) stress transfer and reduced cross-interface transmission and (ii) circumferential bypass within the shell, which together yield only slight flow-stress increases over solid Al while markedly reducing stress serrations compared with both solid Cu and solid Al. Across all orientations, the core–shell structures also exhibit delayed yielding (higher yield strain) relative to solid Cu, indicating enhanced ductility. The results provide an atomistic basis for designing Cu–Al core–shell nanoparticles for robust particle-based processing and additive manufacturing feedstock, and for informing multiscale models with mechanism-resolved, orientation-dependent inputs. Full article

This review examines biodegradable polymer-based core–shell nanoformulations encapsulating essential oils for acne treatment through the lens of physicochemical design and controlled delivery mechanisms. Acne is a common inflammatory skin disorder closely associated with sebum overproduction and microbial imbalance, while conventional therapies, although effective, may present long-term side effects. Increasing attention has therefore turned to sustainable dermatological materials derived from eco-friendly polymers combined with naturally active compounds. Recent advances show that core–shell nanostructures fabricated from biodegradable polymers function as physicochemically engineered carriers for volatile essential oils. They enhance their stability and protect them from premature degradation. They also enable controlled release governed by diffusion, polymer relaxation, interfacial interactions, and degradation kinetics. This review highlights how polymer chemistry, interfacial properties, particle morphology, and processing routes determine encapsulation efficiency, release profiles, and skin permeation behaviour. Particular emphasis is placed on structure–property–function relationships, including mass transport phenomena, thermodynamic compatibility between polymers and essential oils, surface charge, wettability, and nanostructure architecture, which collectively influence bioavailability and therapeutic performance. By integrating concepts from polymer physical chemistry, colloid and interface science, and drug delivery kinetics, these sustainable nanoformulations emerge as promising platforms for acne and sebum control. Overall, essential oil-loaded biodegradable polymeric core–shell systems represent a sustainable and scientifically grounded approach to acne management, although further physicochemical characterization, in vivo validation, and consideration of cost, technical challenges, and current limitations are required to support clinical translation. Full article

While self-healing concrete shows promise for infrastructure repair, its effectiveness is significantly compromised in low-temperature environments because of slowed reaction kinetics and the embrittlement of capsule shells. To address this limitation, novel composite microcapsules featuring an ethyl cellulose shell and a dual-core comprising expansive cement and epoxy resin were developed. These microcapsules were fabricated using a physical spheronization-coating method and subsequently incorporated into cement mortar. Response surface methodology was employed to identify the optimal system, which balances self-healing performance with the retention of mechanical properties: a microcapsule content of 3% (by mass of cement) and a particle size range of 1.4 to 1.7 mm. Under conditions of −20 °C, the optimal formulation achieved a crack surface healing ratio of up to 44.1% and a compressive strength recovery of up to 6.0%. Microstructural and spectroscopic analyses (SEM-EDS, XRD) revealed a synergistic healing mechanism. This mechanism involves the formation of calcium carbonate, C–S–H gel, and anorthite, all cohesively bonded within a polymerized epoxy network. This work establishes a functional material strategy for enabling autonomous crack repair in concrete structures subjected to cold climates. In such environments, even marginal strength recovery, when coupled with effective crack sealing, can significantly enhance structural durability. Full article

This study presents a theoretical analysis of the slow translation of a soft sphere through an unbounded micropolar fluid under steady, low Reynolds number conditions, accounting for the influence of interfacial stress jump. The soft sphere is modeled as a rigid solid core surrounded by a permeable porous gel layer, allowing fluid penetration and momentum exchange across the interface. This core–shell configuration captures the essential structural characteristics of coated or gel-like particles encountered in biological and engineering systems. Closed-form expressions for the velocity components, microrotation, stresses, and couple stresses are derived both within the porous micropolar gel layer surrounding the particle and in the exterior micropolar fluid. The flow inside the permeable coating is described using the general Brinkman solution in spherical coordinates, while the governing micropolar fluid equations are applied in the outer region. Appropriate boundary conditions are imposed at the solid core surface and at the permeable soft-sphere interface to ensure continuity of velocity and microrotation, together with the prescribed stress jump. The normalized drag force acting on the particle is obtained as a function of the particle-to-core radius ratio, permeability, stress-jump parameter, and micropolarity parameter. The results indicate that the hydrodynamic drag decreases as the porous layer becomes thicker and remains finite, approaching unity even when the soft sphere behaves as a solid particle or as a porous sphere translating through an infinite micropolar medium, with other parameters held fixed. Overall, the analysis elucidates the coupled roles of micropolar effects, interfacial stress jump, and porous-layer structure in governing the hydrodynamic resistance experienced by soft particles. Full article

Calcium carbide slag and silica fume was used as a cement replacement material, combined with excavated soil and EPS (expanded polystyrene) particles, to develop a new green and low-carbon lightweight fluid solidified soil (LFSS). Focusing on the performance regulation of LFSS, this study adopted the paste volume ratio (PV, defined as the volume ratio of paste to total mixture) and the water–binder ratio (w/b) to systematically construct a mix ratio design system and proposed EPS particle interface modification and shell formation technology to improve the weak interface bonding between EPS and the matrix. Firstly, based on the paste volume method, the effects of PV and w/b on the flowability and strength of LFSS were analyzed, and a linear correlation model between the water–solid volume ratio and flowability, as well as a quadratic function prediction model for 28-day strength, was established. Secondly, the “core–shell structure” of EPS particles was constructed by combining EVA (ethylene-vinyl acetate) modification with the coating of calcium carbide slag–silica fume paste. Considering the influence of the coating method, w/b, and material mass ratio on interface bonding comprehensively, the optimal process parameters were determined to achieve the interface reinforcement of EPS particle. The results showed that the water–solid volume ratio was significantly linearly correlated with the flowability of LFSS. PV and w/b respectively controlled the framework formation and pore structure evolution of LFSS, with optimal overall performance at PV = 0.55 and w/b = 2.5. The modification shell formation significantly reduced the shell loss rate of EPS particles and increased the 28-day compressive strength of LFSS by 21.7%. SEM (scanning electron microscope) and EDS (energy-dispersive spectroscopy) analysis further revealed that the shell-formation technique promoted the densification of the interface transition zone, enhanced the deposition of hydration products, and strengthened the synergistic effect of Na and Ca elements, thereby significantly improving interface bonding and overall structural stability. This study established a “mix ratio optimization-modification and shell formation” dual-regulation mechanism, providing an effective technical approach and theoretical basis for the engineering application of calcium carbide slag–silica fume-based LFSS. Full article

Microencapsulated phase change materials (MPCMs) offer a promising way to enhance the thermal performance of cement-based materials; however, their incorporation often compromises mechanical properties and durability, limiting practical application. A mechanistic understanding of how MPCM particle size governs the coupled thermal, mechanical, and transport behavior of cementitious systems remains incomplete. In this paper, two organic MPCMs with identical core–shell chemistry but distinct particle sizes (mean diameters of 10.78 μm and 34.21 μm) were incorporated into mortar at dosages of 10 wt.% and 20 wt.% under w/b ratios of 0.35 and 0.45. The effects of MPCM particle size and content on hydration kinetics, rheology, strength development, pore transport behavior, and thermal conductivity were systematically investigated using isothermal calorimetry, flow spread testing, compressive strength measurements, capillary water absorption, thermal conductivity analysis, X-ray diffraction, and SEM–EDS characterization. Results show that MPCM incorporation delays early-age hydration and reduces peak hydration rates, with finer particles exerting a stronger inhibitory effect due to increased specific surface area and water adsorption. While all MPCM-modified mortars exhibit reduced compressive strength and increased capillary absorption, larger MPCM particles mitigate strength loss by limiting the total interfacial transition zone (ITZ) area and reducing ITZ connectivity. In contrast, smaller MPCM particles more effectively decrease thermal conductivity, achieving up to a 33% reduction, owing to enhanced interfacial thermal resistance. Microstructural observations confirm that MPCMs do not alter cement hydration products but influence performance through interfacial defects, porosity evolution, and particle-scale interactions. These findings demonstrate that MPCM particle size critically controls the trade-off between thermal regulation and structural integrity, providing quantitative guidance for designing PCM-modified concrete through optimizing particle-size. Full article

Ni@TiO₂ core–shell nanoparticles were synthesized by magnetron sputtering and their structure verified by HRTEM and EDS analysis. The thermal stability of these particles was investigated using in situ TEM annealing and compared with that of pure Ni nanoparticles. While pure Ni particles sinter at 450 °C and exhibit significant growth at 800 °C, Ni@TiO₂ nanoparticles remain stable up to 700 °C, with the sintering onset between 700 and 800 °C. A simple thermal-mismatch model was applied to explain the stabilizing effect of the TiO₂ shell, demonstrating that differences in thermal expansion between Ni and TiO₂ generate interface stresses sufficient to crack the shell after the amorphous–rutile transformation. The TiO₂ coating effectively delays Ni coalescence by 250 °C relative to bare Ni, highlighting its role as a protective shell against high-temperature sintering. Full article

The development of flexible and self-powered electronic systems requires triboelectric materials that combine high charge retention, mechanical compliance, and stable dielectric properties. Here, we report a redox reaction approach to prepare liquid metal particle-reduced graphene oxide (LMP@rGO) core–shell structures and introduce into a poly(acrylic acid) (PAA) hydrogel to create a high-performance triboelectric layer. The spontaneous interfacial reaction between gallium oxide of LMP and graphene oxide produces a conformal rGO shell while simultaneously removing the native insulating oxide layer onto the LMP surface, resulting in enhanced colloidal stability and a controllable semiconductive bandgap of 2.7 (0.01 wt%), 2.9 (0.005 wt%) and 3.2 eV (0.001 wt%). Increasing the GO content promotes more complete core–shell formation, leading to higher zeta potentials, stronger interfacial polarization, and higher electrical performance. After embedding in PAA, the LMP@rGO structures form hydrogen-bonding networks with the hydrogel nature, improving both dielectric constant and charge retention while notably preserving soft mechanical compliance. The resulting LMP@rGO/PAA hydrogels show enhanced triboelectric output, with the 2.0 wt/vol% composite generating sufficient power to illuminate more than half of 504 series-connected LEDs. All the results demonstrate the potential of LMP@rGO hydrogel composites as promising triboelectric layer materials for next-generation wearable and self-powered electronic systems. Full article

Conventional quantum mechanics treats the electron as a point-like particle endowed with intrinsic properties—mass, charge, and spin—that are inserted as axioms rather than derived from first principles. Here, we propose a thermodynamic reformulation of the electron grounded in entropy field dynamics, based on S-Theory. In this framework, the electron is composed of three distinct entropic components: S_core (a collapsed entropy core from configurational mass), S_EM (a structured electromagnetic entropy field from charge), and S_thermal (a diffuse entropy component from ambient interactions). We show that spin emerges as a rotating S_EM shell around S_core, and that electron collapse—as in quantum measurement—can be modeled as a Recursive Amplification of Sfield (RAS) process driven by entropic feedback. Through mathematical formulation and high-resolution simulations, we demonstrate how the S-field components evolve under entropic excitation, culminating in a collapse threshold defined by local entropy density matching. This model not only explains the emergence of quantum properties but also offers a thermodynamic mechanism for electron–photon interaction, wavefunction collapse, and spin generation, revealing the inner structure and dynamics of one of nature’s most fundamental particles. Full article

pH-thermo-responsive polymeric nanoparticles (P-Nps) functionalized with carboxylic (–COOH) and amide (–NH₂) groups were synthesized by emulsion polymerization to obtain two series with varying functional group ratios and morphologies: core–shell and core–concentration gradient. P-Np dispersions were characterized by dynamic light scattering (DLS), electrophoresis (zeta potential, ζ), scanning electron microscopy (SEM), and rheology (viscosity, η) in a temperature range of 25 °C to 60 °C. In general, the results show that P-Nps exhibit average particle diameters ranging from 250 ≤ Dz/nm ≤ 1200, and exhibit high colloidal stability (−46 ≤ ζ/mV ≤ −22) as temperature rises. SEM analysis revealed irregular and different structures as the proportion of functional groups varied, while rheological measurements demonstrated non-Newtonian behavior as the average shear rate increased (0.01 ≤ γ ˙ /s⁻¹ ≤ 100). Their size, stability, and rheological properties depend on the temperature and location of the functional groups. These properties suggest potential applications such as in stimulating fluids in the oil industry. Full article

Magnetite (Fe₃O₄) nanoparticles are biocompatible, non-toxic, and easily functionalized. Coating them with mesoporous silica (mSiO₂) offers high surface area, pore volume, and tunable surface chemistry for drug loading. In this study, Fe₃O₄ magnetic nanoparticles were synthesized and coated with mSiO₂ shells enriched with calcium ions (Ca²⁺), aiming to enhance bioactivity for bone regeneration and tissue engineering. Different synthesis routes were tested to optimize shell formation Their characterization confirmed the presence of a crystalline Fe₃O₄ core with partial conversion to maghemite (Fe₂O₃) post-coating. The silica shell was mostly amorphous and the optimized samples exhibited mesoporous structure (type IVb). Calcium incorporation slightly altered the magnetic properties without significantly affecting core crystallinity or particle size (11.68–13.56 nm). VSM analysis displayed symmetric hysteresis loops and decreased saturation magnetization after coating and Ca²⁺ addition. TEM showed spherical morphology with some agglomeration. MTT assays confirmed overall non-toxicity, except for mild cytotoxicity at high concentrations in the Ca²⁺-enriched sample synthesized by a modified Stöber method. Their capacity to induce human periodontal ligament cell osteogenic differentiation, further supports the potential of Fe₃O₄/mSiO₂/Ca²⁺ core–shell nanoparticles as promising candidates for bone-related biomedical applications due to their favorable magnetic, structural, and biological properties. Full article

In the context of dust pollution contributing more than 30% to PM_2.5 during urbanization, this study optimally designed a multi-component coupled dust suppressant based on the coupling mechanism of chemical dust suppressants, oriented towards environmental friendliness. The concentration range of the core component was determined through single-factor experiments: surfactant sodium dodecylbenzene sulfonate (SDBS) 0.5–1.0% (minimum surface tension 27.8 mN/m), coagulant sodium polyacrylate 0.1–0.2% (viscosity ≥ 42 mPa·s), and water-retaining agent triethanolamine 0.1–1.0% (3 h water retention > 90%). The L9 (3⁴) orthogonal test was used to optimize the formulation with water retention rate, crust hardness, and wind erosion rate as indicators, combined with range and variance analysis (α = 0.05). The results showed that sodium polyacrylate concentration had an extremely significant effect on water retention (contribution rate 98.6%), and an increase in its concentration significantly enhanced shell hardness (up to 51HA) and reduced wind erosion rate (down to 0.05%). The optimal ratio was 0.2% sodium polyacrylate, 1.0% sodium dodecylbenzene sulfonate, and 2.5% triethanolamine. At this time, the 24 h water retention rate reached 35.14%, and the wind erosion resistance was 16 times higher than that of the control group. The system builds a three-dimensional cross-linked structure through a hydrogen bond network to synergistically achieve enhanced dust wetting, particle coalescence, and long-lasting consolidation, providing theoretical support and practical solutions for green dust suppression technology. Full article

This study presents a modification strategy to fabricate core–shell composite aggregates from reclaimed asphalt pavement (RAP), aligning with green chemistry principles for waste valorization. The method involves creating a porous cementitious shell on the surface of RAP particles through a controlled hydration process. This surface modification simultaneously addresses the inherent structural weaknesses and irregular morphology of raw RAP, enabling the design of materials with desired properties. A face-centered central composite design (FCCD) was employed to optimize the synthesis process, elucidating the nonlinear relationships between key synthesis parameters and the final material characteristics. The optimized synthesis yielded porous aggregates with significantly enhanced structural integrity, evidenced by a 43.9% reduction in crushing value. Furthermore, the surface modification effectively regulated the material’s morphology and particle size distribution, leading to a 3.6 mm increase in median particle size (D₅₀) and a 27.69% decrease in the content of fines (<4.75 mm). Microstructural characterization confirmed the formation of a rough, porous cementitious shell composed of hydration products, which provides the structural basis for the material’s enhanced performance. This work establishes a clear structure–property relationship, demonstrating a new pathway for the rational design and synthesis of functional porous materials from solid waste for application in high-grade pavements. Full article

Phase change materials (PCMs) are widely used for thermal energy storage; however, improving their thermal stability and minimizing supercooling effects remain important challenges. This study addresses these issues by synthesizing and characterizing new microencapsulated MCPs (microPCMs) that incorporate beeswax (BW), a sustainable biological source derived from animals, thus reducing the use of paraffins from petroleum resources, as the main material and calcium carbonate (CaCO₃) as the shell to improve overall performance. MicroPCMs with variable shell contents (20%, 40%, 60%, and 80%) were prepared and analyzed using Fourier Transform Infrared Spectroscopy (FTIR), X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), particle size distribution analysis (PES), and differential scanning calorimetry (DSC) to evaluate their structural, morphological, and thermal properties. The results reveal that microPCMs exhibit a spherical morphology and robust core–envelope integrity, with thermal energy storage capacities ranging from 121.39 to 122.22 J/g, compared to 137.62 J/g for pure beeswax. In addition, the composites demonstrated reduced supercooling and stable thermal performance during repeated cyclic tests. This work introduces the use of calcium carbonate shells combined with a natural beeswax core to create environmentally friendly microPCMs with enhanced thermal stability and reduced supercooling, offering a sustainable alternative for efficient thermal energy storage. Full article

The COVID-19 pandemic emerging in early 2020 triggered global responses. In China, stringent lockdown measures were implemented to suppress the rapid spread of infection, resulting in substantial reductions in anthropogenic emissions. However, several atmospheric haze episodes still occurred. Previous studies have investigated the cause of these haze events predominantly based on the average concentration obtained from bulk analysis, while the micro-scale structure and composition of the haze particles remain poorly understood. In this study, we analyzed the morphology and elemental composition of individual airborne particles collected from an urban area of Beijing in early 2020 using high-resolution transmission electron microscopy equipped with Energy Dispersive X-ray Spectroscopy. The results show that sulfur-dominant, ultrafine, and mixed particles were the most abundant types during the pollution process. Reduced human activities corresponded with a lower percentage of anthropogenic-derived soot, organic particles, and metal-containing particles. Atmospheric aging analysis demonstrated that secondary aerosols were the most significant component during the haze events. The proportion of core–shell particles increased with the intensification of the pollution, while the core/shell ratio of the particles decreased, suggesting a substantial contribution of secondary aerosols to the haze formation. Despite reductions in anthropogenic emissions, larger proportions of secondary aerosol formation enhanced aerosol aging and thereby caused episodic haze pollution during the lockdown period. Full article