Enhancing electromagnetic wave absorption with core‐shell structured SiO_(2)@MXene@MoS_(2)nanospheres

Material composition and structural design are important factors influencing the electromagnetic wave(EMW)absorption performance of materials.To alleviate the impedance mismatch attributed to the high dielectric constant of Ti_(3)C_(2)T_(x)MXene,we have successfully synthesized core‐shell structured SiO_(2)@MXene@MoS_(2)nanospheres.This architecture,comprising SiO_(2)as the core,MXene as the intermediate layer,and MoS_(2)as the outer shell,is achieved through an electrostatic self‐assembly method combined with a hydrothermal process.This complex core‐shell structure not only provides a variety of loss mechanisms that effectively dissipate electromagnetic energy but also prevents self‐aggregation of MXene and MoS_(2)nanosheets.Notably,the synergistic combination of SiO_(2)and MoS_(2)with highly conductive MXene enables the suitable dielectric constant of the composites,ensuring optimal impedance matching.Therefore,the core‐shell structured SiO_(2)@MXene@MoS_(2)nanospheres exhibit excellent EMW absorption performance,featuring a remarkable minimum reflection loss(RL_(min))of−52.11 dB(2.4 mm).It is noteworthy that these nanospheres achieve an ultra‐wide effective absorption bandwidth(EAB)of 6.72 GHz.This work provides a novel approach for designing and synthesizing high‐performance EMW absorbers characterized by“wide bandwidth and strong reflection loss.”

Acoustic radiation force on a cylindrical composite particle with an elastic thin shell and an internal eccentric liquid column in a plane ultrasonic wave field

A model with three-layer structure is introduced to explore the acoustic radiation force(ARF)on composite particles with an elastic thin shell.Combing acoustic scattering of cylinder and the thin-shell theorem,the ARF expression was derived,and the longitudinal and transverse components of the force and axial torque for an eccentric liquid-filled composite particle was obtained.It was found that many factors,such as medium properties,acoustic parameters,eccentricity,and radius ratio of the inner liquid column,affect the acoustic scattering field of the particle,which in turn changes the forces and torque.The acoustic response varies with the particle structures,so the resonance peaks of the force function and torque shift with the eccentricity and radii ratio of particle.The acoustic response of the particle is enhanced and exhibits higher force values due to the presence of the elastic thin shell and the coupling effect with the eccentricity of the internal liquid column.The decrease of the inner liquid density may suppress the high-order resonance peaks,and internal fluid column has less effects on the change in force on composite particle at ka>3,while limited differences exist at ka<3.The axial torque on particles due to geometric asymmetry is closely related to ka and the eccentricity.The distribution of positive and negative force and torque along the axis ka exhibits that composite particle can be manipulated or separated by ultrasound.Our theoretical analysis can provide support for the acoustic manipulation,sorting,and targeting of inhomogeneous particles.

Control and vibration analyses of a sandwich doubly curved micro-composite shell with honeycomb,truss,and corrugated cores based on the fourth-order shear deformation theory

Curved shells are increasingly utilized in applied engineering due to their shared characteristics with other sandwich structures,flexibility,and attractive appearance.However,the inability of controlling and regulating vibrations and destroying them afterward is a challenge to scientists.In this paper,the curve shell equations and a linear quadratic regulator are adopted for the state feedback design to manage the structure vibrations in state space forms.A five-layer sandwich doubly curved micro-composite shell,comprising two piezoelectric layers for the sensor and actuator,is modeled by the fourth-order shear deformation theory.The core(honeycomb,truss,and corrugated)is analyzed for the bearing of transverse shear forces.The results show that the honeycomb core has a greater effect on the vibrations.When the parameters related to the core and the weight percentage of graphene increase,the frequency increases.The uniform distribution of graphene platelets results in the lowest natural frequency while the natural frequency increases.Furthermore,without taking into account the piezoelectric layers,the third-order shear deformation theory(TSDT)and fourth-order shear deformation theory(FOSDT)align closely.However,when the piezoelectric layers are incorporated,these two theories diverge significantly,with the frequencies in the FOSDT being lower than those in the TSDT.

Facile in situ synthesis and characterization of Fe@Si/zeolite Na composites with magnetic core–shell structures from natural materials for enhanced curcumin loading capacity

Curcumin is a natural polyphenol that is used in various traditional medicines.However,its inherent properties,such as its rapid degradation and metabolism,low bioavailability,and short half-life,are serious problems that must be resolved.To this end,a drug carrier incorporating natural magnetic cores in a zeolite framework was developed and applied to the loading of curcumin in ethanol solutions.In this system,curcumin is encapsulated in a zeolite Na(ZNA)magnetic core–shell structure(Fe@Si/ZNA),which can be easily synthesized using an in situ method.Synthesis of Fe_(3)O_(4) nanoparticles was carried out from natural materials using a co-precipitation method.Analysis of the prepared magnetic core–shell structures and composites was carried out using vibrating-sample magnetometery,Fourier transform infrared spectroscopy,transmission electron microscopy,and x-ray diffraction.The cumulative loading of curcumin in the ZNA composite with 9%nanoparticles was found to reach 90.70%with a relatively long half-life of 32.49 min.Stability tests of curcumin loading in the composite showed that adding magnetic particles to the zeolite framework also increased the stability of the composite structure.Adsorption kinetics and isotherm studies also found that the system follows the pseudo-second-order and Langmuir isotherm models.

Heterostructural NiFeW disulfide and hydroxide dual‐trimetallic core‐shell nanosheets for synergistically effective water oxidatio

A stable and highly active core‐shell heterostructure electrocatalyst is essential for catalyzing oxygen evolution reaction(OER).Here,a dual‐trimetallic core‐shell heterostructure OER electrocatalyst that consists of a NiFeWS_(2)inner core and an amorphous NiFeW(OH)_(z)outer shell is designed and synthesized using in situ electrochemical tuning.The electrochemical measurements of different as‐synthesized catalysts with a similar mass loading suggest that the core‐shell Ni_(0.66)Fe_(0.17)W_(0.17)S_(2)@amorphous NiFeW(OH)_(z)nanosheets exhibit the highest overall performance compared with that of other bimetallic reference catalysts for the OER.Additionally,the nanosheet arrays were in situ grown on hydrophilic‐treated carbon paper to fabricate an integrated three‐dimensional electrode that affords a current density of 10 mA cm^(−2)at a small overpotential of 182 mV and a low Tafel slope of 35 mV decade^(−1)in basic media.The Faradaic efficiency of core‐shell Ni_(0.66)Fe_(0.17)W_(0.17)S_(2)@amorphous NiFeW(OH)_(z)is as high as 99.5%for OER.The scanning electron microscope,transmission electron microscope,and X‐ray photoelectron spectroscopy analyses confirm that this electrode has excellent stability in morphology and elementary composition after long‐term electrochemical measurements.Importantly,density functional theory calculations further indicate that the core‐shell heterojunction increased the conductivity of the catalyst,optimized the adsorption energy of the OER intermediates,and improved the OER activity.This study provides a universal strategy for designing more active core‐shell structure electrocatalysts based on the rule of coordinated regulation between electronic transport and active sites.

Stability of Ag@SiO2 core–shell particles in conditions of photocatalytic overall water-splitting

Core–shell nanoparticles containing plasmonic metals（Ag or Au） have been frequently reported to enhance performance of photo-electrochemical（PEC） devices. However, the stability of these particles in water-splitting conditions is usually not addressed. In this study we demonstrate that Ag@SiOcore–shell particles are instable in the acidic conditions in which WO-based PEC cells typically operate, Ag in the core being prone to oxidation, even if the SiOshell has a thickness in the order of 10 nm. This is evident from in situ voltammetry studies of several anode composites. Similar to the results of the PEC experiments, the Ag@SiOcore–shell particles are instable in slurry-based, Pt/ZnO induced photocatalytic water-splitting. This was evidenced by in situ photodeposition of Ag nanoparticles on the Pt-loaded ZnO catalyst, observed in TEM micrographs obtained after reaction. We explain the instability of Ag@SiOby OH-radical induced oxidation of Ag, yielding dissolved Ag+. Our results imply that a decrease in shell permeability for OH-radicals is necessary to obtain stable, Ag-based plasmonic entities in photo-electrochemical and photocatalytic water splitting.

TOUGHENING OF POLYCARBONATE WITH PBA-PMMA CORE-SHELL PARTICLES

The miscibility,mechanical properties,morphology and toughening mechanism of PC/PBA-PMMA blends wereinvestigated.The dynamic mechanical results show that PC/PBA-PMMA blend has good miscibility and strong interfacialadhesion.The Izod impact strength of blend PC/PBA-PMMA with 4%(volume fraction)PBA-PMMA core-shell modifier is16 times higher than that of pure PC.The core-shell volume fraction and thickness of the PMMA shell have effect on thetoughness of PC/PBA-PMMA blends.As PMMA volume fraction increases,the toughness of PC/PBA-PMMA blendincreases,and reaches a maximum value at 30% volume fraction of PMMA or so.The tensile properties of PC/PBA-PMMAblend with a minimum amount of PBA-PMMA modifier show that brittle-tough transition has no significant variance incomparison with that of pure PC.The scanning electron microscopic(SEM)observation indicates that the tougheningmechanism of the blend with the pseudo-ductile matrix modified by small core-shell latex polymer particles is the synergeticeffect of cavitation and shear yielding of the matrix.

THE PREPARATION AND CHARACTERIZATION OF SBR/PS CORE-SHELL PARTICLES BY GAMMA IRRADIATION

A kind of core(SBR)-shell(PS)particles was synthesized by using SBR latex and grafting with St under gammairradiation.The influences of absorbed dose and dose rate on the grafting yield of PS on SBR seed latex have beeninvestigated.Results show there was a transition layer which contained the SBR/PS graft copolymer between the SBR coreand PS shell.Dynamic laser scattering(DLS)and differential scanning calorimetry(DSC)results confirm the existence ofgrafted polystyrene,and transmission electron microscope(TEM)observation verifies the core-shell structure of SBR-g-PSlatex.Such SBR/PS core-shell latex could be processed easily to ultrafine rubber powders by using spray drying andexpected to be used as an impact modifier for PS.

Polybutylacrylate/poly (methyl methacrylate) Core-Shell Elastic Particles as Epoxy Resin Toughener: Part Ⅱ Toughness on DGEBA/DDM system

Mechanlcal properties of epoxy resin were investigated by adding core-shell elastic particles (CSEP). The results indicated that optimized core-shell ratio was 60/40 and the loading volume of CSEP was 10 phr (per hundred parts of epoxy resin by weight). The impact strength of modified systems increased apparently with the decrease of core sizes. However, the shearing strength changed gently with the particle sizes. CSEP with lightly crosslinked rubbery core showed more effectiveness on toughness than others. With solution blending, CSEP could be dispersed in epoxy matrix well, and the morphologies of dispersed rubber domains were controlled perfectly by CSEP whose structure was predesigned. A cavitation-shearing band toughness mechanism was observed from the SEM micrographs of fracture surface. It also was found that the deforming temperature (DT) of modified epoxy did not decline apparently.

Regulating surface In–O in In@InO_(x) core‐shell nanoparticles for boosting electrocatalytic CO_(2) reduction to formate

To solve the excessive emission of CO_(2) caused by the excessive use of fossil fuels and the corre‐sponding environmental problems,such as the greenhouse effect and climate warming,electrocat‐alytic CO_(2) reduction to liquid fuel with high selectivity is of huge significance for energy conversion and storge.Indium has been considered as a promising and attractive metal for the reduction of CO_(2) to formate.However,the current issues,such as low selectivity and current activity,largely limit the industrial application for electrocatalytic CO_(2) reduction,the design optimization of the catalyst structure and composition is extremely important.Herein,we develop a facile strategy to regulate surface In–O of In@InO_(x) core‐shell nanoparticles and explore the structure‐performance relation‐ship for efficient CO_(2)‐to‐formate conversion though air calcination and subsequent in situ electro‐chemical reconstruction,discovering that the surface In–O is beneficial to stabilize the CO_(2) interme‐diate and generate formate.The optimized AC‐In@InO_(x)‐CNT catalyst exhibits a C1 selectivity up to 98%and a formate selectivity of 94%as well as a high partial formate current density of 32.6 mA cm^(-2).Furthermore,the catalyst presents an excellent stability for over 25 h with a limited activity decay,outperforming the previously reported In‐based catalysts.These insights may open up op‐portunities for exploiting new efficient catalysts by manipulating their surface.

Review:Progress in Core-shell Rubber Particles for Efficiently Toughening Resins

Core-shell toughening particles are structured composite particles consisting of generally two different components, one at the center as a rubbery elastic core and surrounding by the second as a glassy inelastic shell. The design, preparation, and application of core-shell polymer particles have been briefly reviewed. Morphological characteristics of the core-shell particles by transmission electron microscopy(TEM) and scanning electron microscopy(SEM) are focused. The vital factors that are useful to control core-shell morphology and toughening properties including core-shell monomer species, polymerization conditions, cross-linking reagents, synthetic method, and post-processing techniques are analyzed. Distinguished properties are mainly considered as the most desirable features that endow core-shell polymer particles with various applicabilities, particularly as effectively toughening components in brittle epoxy resin and polylactide that are substrate of copper clad laminate widely used in the modern electronic world and environmentally friendly materials that are useful as packaging films, disposable tableware, biomedical equipment, and new energy vehicles.

Engineering core–shell Co_(9)S_(8)/Co nanoparticles on reduced graphene oxide: Efficient bifunctional Mott–Schottky electrocatalysts in neutral rechargeable Zn–Air batteries

It is significant for the rational construction of the high–efficient bifunctional electrocatalysts for in–depth understandings of how to improve the electron transfer and ion/oxygen transport in catalyzing oxygen reduction reaction and oxygen evolution reaction(ORR and OER),but still full of vital challenges.Herein,we synthesize the novel“three–in–one”catalyst that engineers core–shell Mott–Schottky Co_(9)S_(8)/Co heterostructure on the defective reduced graphene oxide(Co_(9)S_(8)/Co–rGO).The Co_(9)S_(8)/Co–rGO catalyst exhibits abundant Mott–Schottky heterogeneous–interfaces,the well–defined core–shell nanostructure as well as the defective carbon architecture,which provide the multiple guarantees for enhancing the electron transfer and ion/oxygen transport,thus boosting the catalytic ORR and OER activities in neutral electrolyte.As expected,the integrated core–shell Mott–Schottky Co_(9)S_(8)/Co–rGO catalyst delivers the most robust and efficient rechargeable ZABs performance in neutral solution electrolytes accompanied with a power density of 59.5 mW cm^(-2) and superior cycling stability at 5 mA cm^(-2) over 200 h.This work not only emphasizes the rational designing of the high–efficient bifunctional oxygen catalysts from the fundamental understanding of accelerating the electron transfer and ion/oxygen transport,but also sheds light on the practical application prospects in more friendly environmentally neutral rechargeable ZABs.

Ionic liquid-derived core–shell gold@palladium nanoparticles with tiny sizes for highly efficient electrooxidation of ethanol

To maximize the size and structural advantages of nanomaterials in electrooxidation of ethanol, we herein report the synthesis of core–shell gold(Au)@Palladium(Pd) nanoparticles smaller than 3 nm in an ionic liquid, which combines the advantages of ionic liquids in preparing fine metal nanoparticles with the benefits of core–shell nanostructures. This synthetic strategy relies on the use of an ionic liquid(1-(2'-aminoethyl)-3-methyl-imidazolum tetrafluoroborate) as a stabilizer to produce Au particles with an average size of ca. 2.41 nm, which are then served as seeds for the formation of tiny core–shell Au@Pd nanoparticles with different Au/Pd molar ratios. The strong electronic coupling between Au core and Pd shell endows the Pd shell with an electronic structure favorable for the ethanol oxidation reaction. In specific, the ionic liquidderived core–shell Au@Pd nanoparticles at an Au/Pd molar ratio of 1/1 exhibit the highest mass-and area-based activities, approximately 11 times than those of commercial Pd/C catalyst for ethanol electrooxidation.

Polybutylacrylate/poly(methyl methacrylate) Core-Shell Elastic Particles as Epoxy Resin Toughener: Part I Design and Preparation

Polybutylacrylate (PBA)/poly(methyl methacrylate) (PMMA) core-shell elastic particles (CSEP), whose rubbery core diameter ranged from 0.08 μm to 1.38μm, were synthesized by using conventional emulsion polymerization, multi-step emulsion polymerization, and soapless polymerization. Allyl methacylate (ALMA) and ethylene glycol dimethacrylate (EGDMA) were selected as crosslinking reagents for core polymerization. Methacrylic acid (MAA) was used as functional co-monomer with methyl methacrylate as shell component. The content of vinyl groups in PBA rubbery core increased with the amount of crosslinking reagents. The core-shell ratio affected great on the morphology of the complex particles. Furthermore, the amounts of carboxyl on the surface of core-shell particles, copolymerized with acrylic acid, were determined by potentiometric titration. Results showed that methylacrylic acid was distributed mostly on the surface of particles.

Controlling Shell Thickness of PS/SiO_2 Core-Shell Particles and Their Crystallization into 3-D Ordered Thin Film

PS/SiO2 particles with core-shell structure were synthesized by coating silica on surface of polystyrene(PS) colloidal particles.The reaction parameters,such as initial tetraethyl orthosilicate(TEOS) concentration,water concentration and reaction temperature,have been investigated to control the thickness of silica shells.The shell thickness was prepositional to the square root of the initial concentration of TEOS and first increased with increasing water concentration,reached a maximum at about 2.0 mol/L and then started decreasing beyond that concentration.It was also found that the shell thickness decreased firstly with the reaction temperature added,then tended to a constant.The so-synthesized PS/SiO2 core-shell particles were directly crystallized into 3-D ordered thin film,then sintered at 570℃ into the ordered macroporous thin film.Compared with the conditional method,the present approach avoids repeatedly filling the precursor in the templetes and save time more.

Optimized high performance liquid chromatography–ultraviolet detection method using core-shell particles for the therapeutic monitoring of methotrexate

Methotrexate （MTX） is an antineoplastic drug, and due to its high toxicity, the therapeutic drug mon- itoring is strictly conducted in the clinical practice. The chemometric optimization and validation of a high performance liquid chromatography （HPLC） method using core-shell particles is presented for the determination of MTX in plasma during therapeutic monitoring. Experimental design and response surface methodology （RSM） were applied for the optimization of the chromatographic system and the analyte extraction step. A Poroshel1120 EC-C18 （3.0 mm × 75 mm, 2.7 μm） column was used to obtain a fast and efficient separation in a complete run time of 4 min. The optimum conditions for the chroma- tographic system resulted in a mobile phase consisting of acetic acid/sodium acetate buffer solution （85.0 mM, pH =4.00） and 11.2% of acetonitrile at a flow rate of 0.4 mL/min. Selectivity, linearity, accuracy and precision were demonstrated in a range of 0.10-6.0 μM of MTX. The application of the optimized method required only 150μL of patient plasma and a low consumption of solvent to provide rapid re- sults.

Structural response of aluminum core–shell particles in detonation environment

Natural aluminum particles have the core-shell structure.The structure response refers to the mechanical behavior of the aluminum particle structure caused by external influences.The dynamic behavior of the structural response of aluminum core-shell particles before combustion is of great importance for the aluminum powder burning mechanism and its applications.In this paper,an aluminum particle combustion experiment in a detonation environment is conducted and analyzed;the breakage factors of aluminum particles shell in detonation environment are analyzed.The experiment results show that the aluminum particle burns in a gaseous state and condenses into a sub-micron particle cluster.The calculation and simulation demonstrate that the rupture of aluminum particle shell in the detonation environment is mainly caused by the impact of the detonation wave.The detonation wave impacts the aluminum particles,resulting in shell cracking,and due to the shrinkage-expansion of the aluminum core and stripping of the detonation product,the cracked shell is fractured and peeled with the aluminum reacting with the detonation product.

Photochemical synthesis of bimetallic Au-Ag nanoparticles with “core-shell” type structure by seed mediated catalytic growth

The colloidal Au core/Ag shell structure composite nanoparticles were synthesized in PEG-acetone solution by photochemical route. The monodispersed Au nanoparticles with average diameter of 3.9 nm were used as growth seeds. The optical property of colloids and the sizes of composite nanoparticles were characterized when the molar ratio of Au to Ag ranges from 4∶1 to 1∶4. The results show that a composite nanoparticle structure similar to strawberry shape is formed at the molar ratio of Au to Ag from 4∶1 to 1∶1; the composite nanoparticles consisting of a core of Au and shell of Ag were generated at the 1∶4 molar ratio, having a striking feature of forming (interconnected) network structure.

Synthesis of Ag@Al_2O_3 Core-shell Structure Nanoparticles and Their Enhancement Effect on Dielectric Properties for Ag@Al_2O_3/Polyimide Nanocomposites

A novel core-shell structure Ag@Al2O3 nano-particles were synthesized and doped into polyimide as conductive fillers to prepare the composite films with high dielectric properties and low dielectric loss. The morphology and structures of the Ag@Al2O3 nano-particles were characterized by transmission electron microscopy （TEM）, X-ray diffraction （XRD）, and UV-visible spectroscopy. All the results proved that the Ag@Al2O3 nano-parficles had a typical core-shell structure, for the Ag particles were coated by Al2O3 shell and the average sizes ofAg@Al2O3 particles were between 30 to 150 nm. The as-prepared Ag@Al2O3 nanoparticles were doped into the polyimide with different mass fractions to fabricate the Ag@Al2O3/PI composite films via in-situ polymerization process. SEM analysis of composite films showed that the Ag@Al2O3 nano- particles homogeneously dispersed in polyimide matrix with nanoseale. As dielectric materials for electronic packaging systems, the Ag@Al2O3/PI composites exhibited appropriate mechanical properties and erthaneed dielectric properties, including greatly enhanced dielectric constant and just a slight increase in dielectric loss. These improvements were attributed to the core-shell structure of fillers and their fine dispersion in the PI matrix.

Preparation of novel core-shell nanoparticles by electrochemical synthesis

Nanostructural gold/polyaniline core/shell composite particles on conducting electrode ITO were successfully prepared via electrochemical polymerization of aniline based on 4-aminothiophenol (4-ATP) capped Au nanoparticles. The new approach to the fabrication included three steps: preparation of gold nanoparticles as core by pulse electrodeposition; formation of ATP monolayer on the gold particle surface, which served as a binder and an initiator; polymerization of aniline monomer initiated by ATP molecules under controlled voltage lower than the voltammetric threshold of aniline polymerization, which assured the formation of polyaniline shell film occurred on gold particles selectively. Topographic images were also studied by AFM, which indicated the diameter of gold nanoparticles were around 250 nm. Coulometry characterization confirmed the shell thickness of polyaniline film was about 30 nm. A possible formation mechanism of the Au/polyaniline core-shell nanocomposites was also proposed. The novel as-prepared core-shell nanoparticles have potential application in constructing biosensor when bioactive enzymes are absorbed or embedded in polyaniline shell film.