Shell Phase Research Articles

Magnetic Properties and Microstructure of DyAlCu-diffusion Sintered Nd-Fe-B Magnets

The ability to improve the coercivity of sintered Nd-Fe-B diffused by Dy-Al-Cu alloy derived from electrolysis in a fluoride salt-oxide system was evaluated. The results show that with the increase in heat treatment time, the coercivity of the magnet firstly increased and then decreased. Holding at 900 ℃ for 4 h, tempering at low temperature for 3 h at 550 ℃, the coercivity of GBDPed magnet increased by 44.34 %, the remanence decreased by 1.26 %, the Dy-rich shell phase was recognizable, and the Nd-rich phase evenly distributed. Electron microscope analysis showed that when the GBDP time was longer than 4h, the diffusion of Dy from the shell phase to the matrix phase dominated, decreasing the coercivity with the increase in the diffusion time. The increase of Fe content in the grain boundary phase enhanced the exchange coupling between grains, which also reduced the coercivity of the GBDPed magnet. The infiltration of the matrix phase by excessive Dy and deterioration of (00L) texture of Nd-Fe-B resulted in the reduction of the remanence and the maximum energy product.

Core-Shell Enhanced Single Particle Model for lithium iron phosphate Batteries: Model Formulation and Analysis of Numerical Solutions

In this paper, a core–shell enhanced single particle model for lithium iron phosphate () battery cells is formulated, implemented, and verified. Starting from the description of the positive and negative electrodes charge and mass transport dynamics, the positive electrode intercalation and deintercalation phenomena and associated phase transitions are described with the core–shell modeling paradigm. Assuming two phases are formed in the positive electrode, one rich and one poor in lithium, a core-shrinking problem is formulated and the phase transition is modeled through a shell phase that covers the core one. A careful discretization of the coupled partial differential equations is proposed and used to convert the model into a system of ordinary differential equations. To ensure robust and accurate numerical solutions of the governing equations, a sensitivity analysis of numerical solutions is performed and the best setting, in terms of solver tolerances, solid phase concentration discretization points, and input current sampling time, is determined in a newly developed probabilistic framework. Finally, unknown model parameters are identified at different C-rate scenarios and the model is verified against experimental data.

ZnO‐Reinforced Thermal Regulating Microcapsules with Double‐Layer Shell via Atomic Layer Deposition

AbstractConventional plain organic or inorganic shell for microcapsules has their own drawbacks, the organic shell has defects in thermal conductivity and stability; while the compactness and coverage of inorganic shell are not satisfactory. Herein, a novel approach to synthesis of organic–inorganic composite double‐layer shell phase change microcapsule (DLSPCM) is proposed, which is achieved by forming inorganic outer shell on the surface of organic shell via atomic layer deposition (ALD). Taking the pristine microcapsule with paraffin core and melamine formaldehyde (MF) shell as an example, MF‐ZnO composite double‐layer shell (DLS) is formed in this paper. The melting enthalpy of DLSPCM obtained by 100 ALD cycles is 159.7 J g−1, which is only 12.1 J g−1 lower than that of paraffin @ MF microcapsules (control sample), while the thermal conductivity of DLSPCM surges by 77.8%, and the thermal energy storage ability and thermal regulation performance are basically maintained. After 900 thermal cycles, the heat storage capacity of DLSPCM obtained by 100 ALD cycles decreased by only 3%. Besides, the photocatalytic performance and antibacterial activity of ZnO‐reinforced DLSPCM are further confirmed. The successful design of DLSPCM via ALD is prospective for the encapsulation, modification, and reinforcement of phase change microcapsules.

Generation of liquid metal double emulsion droplets using gravity-induced microfluidics.

Several microfluidic applications are available for liquid metal droplet generation, but the surface oxidation of liquid metal has placed limitations on its application. Multiphase microfluidics makes it possible to protect the inner droplets by producing the structure of double emulsion droplets. Thus, the generation of liquid metal double emulsion droplets has been developed to prevent the surface oxidation of Galinstan. However, the generation using common methods faces considerable challenges due to the gravity effect introduced from the high density of liquid metal, making it difficult for the shell phase to wrap the inner phase. To overcome this obstacle, we introduce an innovative method – a gravity-induced microfluidic device – to creatively generate controllable liquid metal double emulsion droplets, achieved by altering the measurable inclination angle of the plane. It is found that when the inclination angle ranges from 30° to 45°, the device manages to generate liquid metal double emulsion droplets with perfect double sphere-type configuration. Additionally, the core–shell liquid metal hydrogel capsules present potential applications as multifunctional materials for controlled release systems in drug delivery and biomedical applications. By regulating pH or imposing mechanical force, the hydrogel shell can be dissolved to recover the electrical conductivity of Galinstan for applications in flexible electronics, self-healing conductors, elastomer electronic skin, and tumor therapy.

Preparation of core-shell ZSM-5@Beta molecular sieve and catalytic alkylation to 2,6-Dimethylnaphthalene

ZSM-5@Beta core-shell molecular sieve was prepared by dynamic hydrothermal synthesis method using ZSM-5 adhered Beta seed crystals as the core phase, and polydiallyl dimethyl ammonium chloride (PDDA) was used as a coupling agent to adhere Beta seed crystals on the surface of ZSM-5. The structure and physical properties of composite molecular sieves were characterized by XRD, N2 adsorption-desorption, SEM, TEM, ICP, NH3-TPD and Py-FTIR. The catalytic performance of composite molecular sieves for alkylation of 2-methylnaphthalene (2-MN) with methanol was investigated. The results showed that ZSM-5@Beta composite molecular sieve prepared by this method had a core-shell structure, and the particle size was about 500 nm. Compared with mechanically mixed binary molecular sieve, core-shell molecular sieve had higher specific surface area and external surface area, lower acid strength and stronger acid center density. Through the construction of core-shell interface and hierarchical porous, the catalytic activity was improved by shell phase Beta molecular sieve with 12-membered ring channel, and the catalytic selectivity was improved by core phase ZSM-5 molecular sieve with 10-membered ring channel in the alkylation reaction of 2-MN with methanol. The 2,6-/2,7-DMN ratio in the products reached 1.35, and the yield of 2,6-DMN reached 4.29%.

The thermal behavior and flame retardant performance of phase change material microcapsules with modified carbon nanotubes

The organic shell materials and phase change material (PCM) show the drawbacks of low thermal conductivity, poor thermal stability and flammability, restricting the application of the PCM microcapsules. A novel Fe3O4/carbon nanotubes (CNTs) modified PCM microcapsule (Fe–C-PCM) was successfully fabricated by the in-situ polymerization method and applied in the rigid polyurethane foam (RPUF-Fe-C-PCM) in this study. The results indicated that Fe3O4 microspheres with a diameter of about 200 nm were formed on CNTs. The thermostability of Fe–C-PCM was better than that of normal PCM microcapsules, which was proved by the results of TGA and MCC. The DSC results showed that the CNTs in Fe–C-PCM acted as internal and external heat transfer channels to ameliorate the thermal conductivity of PMMA. The results of cone calorimeter test indicated that RPUF-Fe-C-PCM had large inhibitory effect on the heat and smoke release of composite during the combustion process. The test results from small room model test and infrared thermal imager suggested that RPUF-Fe-C-PCM kept the indoor temperature stable within a certain range and exhibited excellent ability to absorb/release heat. These properties will greatly promote the application of Fe–C-PCM in insulation materials.

Evolution of the conductive filament system in HfO2-based memristors observed by direct atomic-scale imaging

The resistive switching effect in memristors typically stems from the formation and rupture of localized conductive filament paths, and HfO2 has been accepted as one of the most promising resistive switching materials. However, the dynamic changes in the resistive switching process, including the composition and structure of conductive filaments, and especially the evolution of conductive filament surroundings, remain controversial in HfO2-based memristors. Here, the conductive filament system in the amorphous HfO2-based memristors with various top electrodes is revealed to be with a quasi-core-shell structure consisting of metallic hexagonal-Hf6O and its crystalline surroundings (monoclinic or tetragonal HfOx). The phase of the HfOx shell varies with the oxygen reservation capability of the top electrode. According to extensive high-resolution transmission electron microscopy observations and ab initio calculations, the phase transition of the conductive filament shell between monoclinic and tetragonal HfO2 is proposed to depend on the comprehensive effects of Joule heat from the conductive filament current and the concentration of oxygen vacancies. The quasi-core-shell conductive filament system with an intrinsic barrier, which prohibits conductive filament oxidation, ensures the extreme scalability of resistive switching memristors. This study renovates the understanding of the conductive filament evolution in HfO2-based memristors and provides potential inspirations to improve oxide memristors for nonvolatile storage-class memory applications.

Nobel Ag–Cu ion-exchange bimetallic nanoclusters formation over gold ion (Au2+) implanted materials RBS and optical study

The ion-exchange from molten salts is a well-established, low-cost technology capable of altering the chemical–physical properties of glass materials. Technologically driven some glass materials containing metal clusters have attracted quite attention both in cluster research and in possible futuristic applications of such nanoclusters for magnetic or optoelectronic purposes. The amalgamation of transparency and hardness at ambient temperature, combined with a suitable mechanical forte and excellent chemical strength, makes this material essential for many applications in different potential technological fields (such as, for instance, the optical fibers which constitute the physical carrier for high-speed communication networks as well as the transducer for a wide range of high-performance sensors, transparency biomarker etc). In this regard, the formation of bimetallic alloys and core–shell nanostructures inside a soda-lime glass was prepared by simple ion-exchange methods and subjected to optical absorption (OA) studies. Further, an attempt has been made for the first time by a novel route for the synthesis of bimetallic nanoclusters, gold in various doses was directly implanted in a plain soda-lime glass as well as in a copper and silver ion-exchanged soda-lime glass using the tandem accelerator anticipating the core–shell or alloys phase between the metal species. Also, the post implanted gold (Au+) metal ions were investigated by Rutherford backscattering spectroscopy (RBS) analysis was performed on the Cu and Ag ion-exchanged samples to confirm the presence of bimetallic clusters formed by ion-exchange during implantation.

An Evaluation of a Systematic Series of Cobalt-Free Ni-Rich Core-Shell Materials as Positive Electrode Materials for Li-Ion Batteries

A wide range of Co-free Ni-rich core–shell precursors with different core/shell compositions, core sizes and shell thicknesses heated at various temperatures were evaluated in this work. In all cases, the shell phase had a larger Mn content than the core phase. The heating temperature of the precursor/lithium hydroxide mixture during synthesis must be carefully selected. Core–shell materials made at insufficient temperature have low specific capacity due to low crystallinity and a high percentage of Ni atoms in the Li layer. Materials made at excessive temperature show interdiffusion between the shell and core compositions leading to poor capacity retention and poor safety performance. When the heating temperature is selected appropriately, materials which retain the core–shell structure after synthesis can be made. Two of these materials show excellent specific capacity, capacity retention and safety performance. Accelerating rate calorimetry experiments show that charged core–shell materials with a thick and Mn-rich shell have the least reactivity with electrolyte at elevated temperatures, suggesting such materials will lead to the safest Li-ion cells.

Bimodal Microstructure Design of CrMnFeCoNi High-Entropy Alloy Using Powder Metallurgy

Single-phase equiatomic high-entropy alloy (HEA); CrMnFeCoNi, exhibits high strength and ductility at room temperature and low temperature due to the effect of twinning. In this study, a concept of a bimodal microstructure design for HEA using powder metallurgy was proposed. Microstructures of the sintered compact fabricated from HEA powder mechanically-milled using SUJ2 balls were analyzed by EBSD. A network structure of fine grains (Shell), which surrounded the coarse-grained structure (Core), was formed in the HEA compact. The hardness of the HEA with bimodal microstructure were higher than the compact fabricated from as-received HEA powder, and the network structure showed high hardness than Core phase. Furthermore, W-rich surface layer was formed on the HEA powder mechanically-milled using WC-Co balls owing to the transfer of WC-Co balls to the surface of HEA powder during mechanical milling. A network structure of the W-rich phase, which surrounded the HEA phase, was formed in the compact fabricated from the mechanically-milled HEA powder. In particular, the hardness of compact fabricated from HEA powder mechanically-milled using WC-Co balls was high due to the high concentration of tungsten and formation of Shell phase. These results indicate that developed method can control the microstructure of HEA; grain size and elementary diffusion distributions.

From nature to additive manufacturing: Biomimicry of porcupine quill

A porcupine’s quill is an extraordinary natural armor capable of withstanding high compression load. By unravelling the unique properties of the porcupine quill design, the bioinspired structures can be applied in engineering applications. The present work investigates both the mechanical and chemical properties of a porcupine quill. An axial compression test is conducted on the natural material in three states: the entire composite quill structure and the response of shell and foam phases individually. These mechanical responses are reported, and compressive failure modes are quantified by scanning electron microscopy (SEM) and micro-computed tomography (µCT). Fourier-transform infrared (FTIR) spectroscopy is conducted and a slight compositional variation is found between the shell and foam phases of the porcupine quill. The design of a porcupine quill inspired structure is achieved through fabrication by stereolithography (SLA) additive manufacturing (AM) technology. Based on these design workflows, the properties of the structures, including struts length and relative density are analysed. Random workflow has a higher number of short struts while longer struts dominate reflected workflow. Relative density increases with the increasing number of seeds. However, it decreases with a growing number of sectors. Qualitative analysis of the numerical simulation presented shows the importance of struts connectivity for efficient stress distribution.

3D printed bioinspired scaffolds integrating doxycycline nanoparticles: Customizable implants for in vivo osteoregeneration

3D printing has revolutionized pharmaceutical research, with applications encompassing tissue regeneration and drug delivery. Adopting 3D printing for pharmaceutical drug delivery personalization via nanoparticle-reinforced hydrogel scaffolds promises great regenerative potential. Herein, we engineered novel core/shell, bio-inspired, drug-loaded polymeric hydrogel scaffolds for pharmaceutically personalized drug delivery and superior osteoregeneration. Scaffolds were developed using biopolymeric blends of gelatin, polyvinyl alcohol and hyaluronic acid and integrated with composite doxycycline/hydroxyapatite/polycaprolactone nanoparticles (DX/HAp/PCL) innovatively via 3D printing. The developed scaffolds were optimized for swelling pattern and in-vitro drug release through tailoring the biphasic microstructure and wet/dry state to attain various pharmaceutical personalization platforms. Freeze-dried scaffolds with nanoparticles reinforcing the core phase (DX/HAp/PCL-LCS-FD) demonstrated favorably controlled swelling, preserved structural integrity and controlled drug release over 28 days. DX/HAp/PCL-LCS-FD featured double-ranged pore size (90.4 ± 3.9 and 196.6 ± 38.8 µm for shell and core phases, respectively), interconnected porosity and superior mechanical stiffness (74.5 ± 6.8 kPa) for osteogenic functionality. Cell spreading analysis, computed tomography and histomorphometry in a rabbit tibial model confirmed osteoconduction, bioresorption, immune tolerance and bone regenerative potential of the original scaffolds, affording complete defect healing with bone tissue. Our findings suggest that the developed platforms promise prominent local drug delivery and bone regeneration.

Plant Stress Granules: Trends and Beyond.

Stress granules (SGs) are dynamic membrane-less condensates transiently assembled through liquid–liquid phase separation (LLPS) in response to stress. SGs display a biphasic architecture constituted of core and shell phases. The core is a conserved SG fraction fundamental for its assembly and consists primarily of proteins with intrinsically disordered regions and RNA-binding domains, along with translational-related proteins. The shell fraction contains specific SG components that differ among species, cell type, and developmental stage and might include metabolic enzymes, receptors, transcription factors, untranslated mRNAs, and small molecules. SGs assembly positively correlates with stalled translation associated with stress responses playing a pivotal role during the adaptive cellular response, post-stress recovery, signaling, and metabolic rewire. After stress, SG disassembly releases mRNA and proteins to the cytoplasm to reactivate translation and reassume cell growth and development. However, under severe stress conditions or aberrant cellular behavior, SG dynamics are severely disturbed, affecting cellular homeostasis and leading to cell death in the most critical cases. The majority of research on SGs has focused on yeast and mammals as model organism. Nevertheless, the study of plant SGs has attracted attention in the last few years. Genetics studies and adapted techniques from other non-plant models, such as affinity capture coupled with multi-omics analyses, have enriched our understanding of SG composition in plants. Despite these efforts, the investigation of plant SGs is still an emerging field in plant biology research. In this review, we compile and discuss the accumulated progress of plant SGs regarding their composition, organization, dynamics, regulation, and their relation to other cytoplasmic foci. Lastly, we will explore the possible connections among the most exciting findings of SGs from mammalian, yeast, and plants, which might help provide a complete view of the biology of plant SGs in the future.

Core–Shell Droplet Generation Device Using a Flexural Bolt-Clamped Langevin-Type Ultrasonic Transducer

Droplets with a core–shell structure formed from two immiscible liquids are used in various industrial field owing to their useful physical and chemical characteristics. Efficient generation of uniform core–shell droplets plays an important role in terms of productivity. In this study, monodisperse core-shell droplets were efficiently generated using a flexural bolt-clamped Langevin-type transducer and two micropore plates. Water and silicone oil were used as core and shell phases, respectively, to form core–shell droplets in air. When the applied pressure of the core phase, the applied pressure of the shell phase, and the vibration velocity in the micropore were 200 kPa, 150 kPa, and 8.2 mm/s, respectively, the average diameter and coefficient of variation of the droplets were 207.7 μm and 1.6%, respectively. A production rate of 29,000 core–shell droplets per second was achieved. This result shows that the developed device is effective for generating monodisperse core–shell droplets.

Моделирование размерных эффектов при фазовых превращениях в субмикронных частицах сплава Au-Pt-Pd

Size effects act at phase equilibria in micro- and nanoparticles They appear as shifts of the characteristic lines and points in the phase diagrams. We simulated and visualized these effects in ternary systems, such as Au–Pt–Pd solid solution. We applied methods of chemical thermodynamics to study the influence of the alloy composition on the region where core-shell states for the particles with a radius of 250 nm exist. It was shown that the splitting area of the alloy decreases and splits due to competing core-shell states, with Pt segregation in either core or shell phase. The phase diagram contains nodes of stable and metastable core-shell equilibrium states. We studied some of the properties of these states (composition of coexisting solutions, radius of the core phase). The described effects are relevant for understanding the catalytic activity of Au–Pt–Pd alloy particles.

Molecular weight effect on the structural detail and chain characteristics of 33-armed star polystyrene

In this study, synchrotron X-ray scattering and quantitative data analysis were performed on a series of 33-armed polystyrenes with four different arm molecular weights in cyclohexane (CHX, Θ solvent) and tetrahydrofuran (THF, good solvent). The quantitative scattering analysis was successfully done, providing molecular structure details and their responses to the solvent change. Each star system is confirmed to be prepared in a very narrow unimodal size distribution; the distribution is slightly broadened with increasing the arm molecular weight. It has an oblate ellipsoid shape, which is composed of two phases, a denser and smaller core and a less dense and thicker fuzzy shell; the ellipsoidicity ranges in 0.56–0.62. The core and shell phases are enlarged and thickened respectively by the arm molecular weight increases. Both the phases are further expanded in THF. Interestingly, the THF-induced expansion is predominant in the core against the fuzzy shell with a Gaussian like density gradient. Overall, the 33-armed star polystyrenes in various molecular weights are quite unique in the structural details and performance in solvent changes, which would be beneficial for advanced applications in various technological areas including smart deliveries of desired molecules (drug, gene, imaging agent, etc.).

Facile Synthesis of Fluorine-Doped Hollow Mesoporous Carbon Nanospheres for Supercapacitor Application

Hollow mesoporous carbon nanospheres doped with fluorine (FHMC) were synthesized for high-performance supercapacitor applications. Monodisperse nanospheres with a copolymeric core-silica shell were produced by charge density matching. The copolymeric chains in the core phase were crosslinked through a Friedel-Crafts reaction, followed by carbonization at 800 °C under a N2 atmosphere to obtain the core-shell (CSC) nanospheres with a carbon core and silica/carbon composite shell. The silica phase of these core-shell nanospheres was etched selectively during the thermal decomposition of Teflon to synthesize the FHMC nanospheres. During the etching process of silica in the shell phase, the surfaces of the nanospheres were doped with fluorine. The BET surface area was increased significantly from 788 m2/g and 1.31 cm3/g for the CSC nanospheres to 1021 m2/g and 2.55 cm3/g for the FHMC nanospheres. The specific capacitance of the FHMC nanospheres prepared was approximately 174 F/g at a current density of 0.5 A/g. The capacity retention after 10000 charge/discharge cycles at a current density of 1 A/g was approximately 93.6%.

Adjusting the Néel relaxation time of Fe3O4/Zn x Co1−x Fe2O4 core/shell nanoparticles for optimal heat generation in magnetic hyperthermia

In this work it is shown a precise way to optimize the heat generation in high viscosity magnetic colloids, by adjusting the Néel relaxation time in core/shell bimagnetic nanoparticles, for magnetic fluid hyperthermia (MFH) applications. To pursue this goal, Fe3O4/Zn x Co1−x Fe2O4 core/shell nanoparticles were synthesized with 8.5 nm mean core diameter, encapsulated in a shell of ∼1.1 nm of thickness, where the Zn atomic ratio (Zn/(Zn + Co) at%) changes from 33 to 68 at%. The magnetic measurements are consistent with a rigid interface coupling between the core and shell phases, where the effective magnetic anisotropy systematically decreases when the Zn concentration increases, without a significant change of the saturation magnetization. Experiments of MFH of 0.1 wt% of these particles dispersed in water, in Dulbecco modified Eagles minimal essential medium, and a high viscosity butter oil, result in a large specific loss power (SLP), up to 150 W g−1, when the experiments are performed at 571 kHz and 200 Oe. The SLP was optimized adjusting the shell composition, showing a maximum for intermediate Zn concentration. This study shows a way to maximize the heat generation in viscous media like cytosol, for those biomedical applications that require smaller particle sizes.

Influence of Annealing Temperature on Structural Properties and Stability of CsPbBr3/TiO2 Core/Shell

Although all-inorganic CsPbBr3 perovskites quantum dots exhibit an excellent photophysical properties, which could be applied in various applications, they still suffer from poor structural stability owing to environment factors. Therefore, TiO2 was coated on the CsPbBr3 QDs as a protecting shell to enhance their stability. Moreover, anatase phase of TiO2 shell was obtained by annealing at more than 300°C due to its most effective electron extraction properties among other crystalline forms of TiO2. However, the CsPbBr3 QDs can be degraded under high temperature. Herein, the annealing temperatures ranging from 300-500°C were optimized to obtain the anatase TiO2 shell and good crystallinity of CsPbBr3 QDs core. The morphology and optical properties of CsPbBr3 QDs, CsPbBr3/TiOx and CsPbBr3/TiO2 were studied by using transmission electron microscope (TEM), photoluminescence (PL) measurement and UV-Visible spectroscopy, respectively. Finally, the CsPbBr3/TiO2 annealed at the optimum temperature was compared with the bare CsPbBr3 QDs to prove the enhancement of their structural stability under ambient air by using X-ray diffraction (XRD).

Migration of cations and shell functionalization for Cu-Ce-La/SSZ-13@ZSM-5: The contribution to activity and hydrothermal stability in the selective catalytic reduction reaction

A core–shell structure Cu–Ce–La/SSZ-13@ZSM-5 catalyst with a Cu–Ce–La/SSZ-13 core and a ZSM-5 shell was first synthesized by a self-assembly method and used for ammonia-selective catalytic reduction (NH3-SCR). In comparison with Cu–Ce–La/SSZ-13, Cu–Ce–La/SSZ-13@ZSM-5 with appropriate shell thickness presents better SCR activity and hydrothermal stability. We discovered an ion migration effect during the shell phase assembly process and further proposed that the ion migration effect was induced by the dissolution of the core phase during the growth of the shell. Part of the metal ions were migrated and redistributed during the assembly of the ZSM-5 shell, resulting in the transformation of [Cu(OH)]+–Z to Cu2+–2Z species and the functionalization of the shell phase. The functionalized shell is beneficial for the adsorption and activation of NH3. The results of an H2O resistance test and thermogravimetric analysis confirm that the coating of the hydrophobic shell can effectively improve the hydrothermal stability and H2O resistance of core–shell Cu–Ce–La/SSZ-13@ZSM-5.