Transient responses of double-curved sandwich two-layer shells resting on Kerr's foundations with laminated three-phase polymer/GNP/fiber surface and auxetic honeycomb core subjected to the blast load

This work uses refined first-order shear theory to analyze the free vibration and transient responses of double-curved sandwich two-layer shells made of auxetic honeycomb core and laminated three-phase polymer/GNP/fiber surface subjected to the blast load.Each of the two layers that make up the double-curved shell structure is made up of an auxetic honeycomb core and two laminated sheets of three-phase polymer/GNP/fiber.The exterior is supported by a Kerr elastic foundation with three characteristics.The key innovation of the proposed theory is that the transverse shear stresses are zero at two free surfaces of each layer.In contrast to previous first-order shear deformation theories,no shear correction factor is required.Navier's exact solution was used to treat the double-curved shell problem with a single title boundary,while the finite element technique and an eight-node quadrilateral were used to address the other boundary requirements.To ensure the accuracy of these results,a thorough comparison technique is employed in conjunction with credible statements.The problem model's edge cases allow for this kind of analysis.The study's findings may be used in the post-construction evaluation of military and civil works structures for their ability to sustain explosive loads.In addition,this is also an important basis for the calculation and design of shell structures made of smart materials when subjected to shock waves or explosive loads.

Preparation of Self-crosslinked Fluorocarbon Polymer Emulsion with Core-shell Structure by the Method of Soap-free Emulsion Polymerization

Using methyl methacrylate （MMA）, butyl acrylate（BA） and hexafluorobutyl acrylate（HFBA） as main raw materials, we prepared self-crosslinked fluorocarbon polymer emulsion with core-shell structure via soap-free emulsion polymerization when the conception of particle design and polymer morphology was adopted. Moreover, the influence of mole ratio of BA to MAA, pH value on the oligomer was studied. And the effects of the added amount of oligomer, self-crosslinked monomer and HFBA, mass ratio of BA to MMA, reaction temperature and the initiator on the polymerization technology and the performance of the product, were investigated and optimized. The structure and performance of the fluorocarbon polymer emulsion were characterized and tested with FTIR, TEM, MFT and contact angle and water absorption of the latex film. The experimental results show that the optimal conditions for preparing fluorocarbon polymer emulsion are as follows： for preparing the oligomer, tool ratio of BA to MAA is equal to 1.0 ： 1.60, and pH value is controlled within the range of 8.0 and 9.0; for preparing fluorocarbon polymer emulsion, the added amount of oligmer[P（BA/MANa）] is 6%; mass ratio of BA to MMA is 40 ＂ 60; the added amount of self-crosslinked monomer is 2%, the added amount of HFBA is 15 %; reaction temperature is 80 ℃; the mixture of potassium persulfate and sodium bisulfite is used as the initiator. The film-forming stability of the fluorocarbon polymer emul- sion and the performance of the latex film, which is prepared with the soap-free emulsion polymerization, are better than that prepared with the conventional emulsion polymerization.

NARROW-DISPERSED CROSSLINKED CORE-SHELL POLYMER MICROSPHERES PREPARED BY SURFACE-INITIATED ATOM TRANSFER RADICAL POLYMERIZATION

Grafting of polystyrene with narrowly dispersed polymer microspheres through surface-initiated atom transferradical polymerization(ATRP)was investigated.Polydivinylbenzene(PDVB)microspheres were prepared by dispersionpolymerization with poly(N-vinyl pyrrolidone)(PVP)as stabilizer.The surfaces of PDVB microspheres werechloromethylated by chloromethyl methyl ether in the presence of zinc chloride as catalyst to form chloromethylbenzeneinitiating core sites for subsequent ATRP grafting of styrene using CuCl/bpy as catalytic system.Polystyrene was found to begrafted not only from the particle surfaces but also from within a thin shell layer,resulting in the formation of particles sizeincreased from 2.38-2.58 μm,which can further grow to 2.93 μm during secondary grafting polymerization of styrene.Thisdemonstrates that grafting polymerization proceeds through a typical ATRP procedure with living nature.All of the preparedmicrospheres have narrow particle size distribution with coefficient of variation around 10%.

MICRON CORE-SHELL PARTICLES PREPARED BY GRAFTING POLYMERIZATION OF METHYL METHACRYLATE FROM NARROW DISPERSE SURFACE OF CHLOROMETHYLATED POLYDIVINYLBENZENE VIA ATRP

Grafting of poly(methyl methacrylate)from narrow disperse polymer particles by surface-initiated atom transferradical polymerization(ATRP)was investigated.Polydivinylbenzene(PDVB)particles were prepared by dispersionpolymerization with poly(N-vinyl pyrrolidone)(PVP)as the stabilizer.Chloromethylated PDVB was used as initiating coresites for subsequent ATRP of methyl methacrylate with CuBr/bpy as catalyst system.It was found that poly(methylmethacrylate)was grafted not only from the particle surfaces but also from within a thin shell layer,leading to particles sizeincreases from 2.38-3.00 μm with a core-shell structure particles.The grafted core-shell particles were characterized withFTIR,SEM,DSC.

Synthesis and Characterization of Poly (Methyl Methacrylate)/Polyethylenimine Grafting Core-Shell Nanoparticles for CO2 Adsorption Using Soap-Free Emulsion Copolymerization

Unlike previous emulsion polymerization, we used grafting reactions in soap-free emulsion systems. In this study, we synthesized grafted PMMA/PEI core-shell nanoparticles by varying the MMA/PEI content and molecular weight of PEI (Mn = 600, 8000, and 10,000). The size and morphology of the core-shell nanoparticles were characterized by a particle size analyzer and scanning electron microscopy. The nanoparticles were 178 - 408 nm in diameter and swelled in water or methanol by 30 - 75 nm. The size of the nanoparticles increased with MMA contents, whereas the size distribution progressively became homogeneous with increasing molecular weight of PEI. Lastly, we measured CO2 adsorption capacity of the grafted PMMA/PEI core-shell nanoparticles, and we found the capacity to be limited at a level of 0.69 mg, which occurred for nanoparticles prepared from emulsions at a pH value of 11.

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.”

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.

Synergistic Effect of Core/Shell‑Structured Composite Fibers:Efficient Recovery of Rare‑Earth Elements from Spent NdFeB Permanent Magnets

NdFeB magnets are third-generation permanent magnets that are employed as indispensable components in various industries.Notably,rare-earth elements(REEs)such as Dy and Nd must be efficiently recovered from end-of-life magnets to enable resource circulation and reinforce unstable supply chains.To that end,this paper reports synergistically performing core/shell-structured composite fibers(CSCFs)containing sodium polyacrylate and nanoporous zeolitic imidazolate framework-8(NPZIF-8)nanocrystals as a readily recoverable adsorbent with an exceptional REE-adsorbing ability.The CSCF core forms an NPZIF-8 nanocrystal shell on the fiber surface as well as draws REEs using its dense sodium carboxylate groups into the NPZIF-8 nanocrystal lattice with high specific surface area.The CSCFs exhibit significantly higher maximum adsorption capacities(468.60 and 435.13 mg·g-1)and kinetic rate constants(2.02 and 1.92 min-1)for the Nd3+and Dy3+REEs than those of previously reported REE adsorbents.Additionally,the simple application of the CSCFs to an adsorption reactor considerably mitigates the adsorbent-shape-induced pressure drop,thereby directly influencing the energy efficiency of the recovery.Moreover,the high REE-recovery ability,tractability,and recyclability of the CSCFs offers a pragmatic pathway to achieving cost-effective REE recovery.Overall,this study provides new insights into designing synergistically performing core/shell architectures for feasible REE recovery.

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.

Synthesis of core-shell structured polymers with inserted thioether from a multi-functional scaffold

The synthesis of a thioether inserted, core-shell structured polymer from the scaffold of hyperbranched polyglycerol (PG) was described. PG was first allyl functionalized, and in the presence of AlBN, the allyl groups further underwent radical addition to thiol compounds, thus thiol functional polyethylene oxide monomether (MPEO) were grafted onto PG. Similarly, 2-mercaptoethylammonium chloride was introduced onto PG via thiol addition, and the residual amino groups were further quaternized with decyl bromide, leading to an amphiphilic core-shell structure polymer. (c) 2007 De Cheng Wan. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved.

Au_(core)Co_(shell)纳米粒子的制备、表征及其表面增强拉曼光谱研究

AucoreCoshell nanoparticles with different shell thicknesses were prepared by using chemical reduction method and characterized by scanning electron microscopy（SEM） and cyclic voltammetry（CV）. The results reveal that the prepared core-shell nanoparticles were covered by Co shell and exhibited the similar electrochemistry property with the Co nanoparticles surface. Surface enhanced Raman spectroscopy（SERS） activities of these nanoparticles were studied by using pyridine as a probe molecule. It was found that the SERS intensity depended on the Co shell thickness of the core-shell nanoparticles and was weakened with the increasing shell thickness. The SERS intensity of these AucoreCoshell nanoparticles is found to be about twenty times higher than that obtained on an electrochemically roughened cobalt electrode.

Fe_(core)-Pt_(shell)/C核壳型纳米催化剂电催化还原氧的性能

应用两步化学还原法合成不同壳层厚度的Fecore-Ptshell纳米粒子,并用SEM、TEM、EDS和XRD手段对其进行物理表征,应用动电位、交流阻抗和循环伏安法进行氧还原电催化活性及抗甲醇性测试。结果表明,样品Fecore-Ptshell纳米颗粒粒径分布集中,其中Fecore,1-Ptshell,0.5平均值为50nm,核芯直径约34nm,壳层厚度约8nm;与Pt/C相比,Fecore-Ptshell/C对氧还原的催化活性和抗甲醇性明显提高,Fe与Pt原子比为1:0.5的Fecore-Ptshell/C在0.5mol·L-1H2SO4中氧还原的最大峰电流密度可达到184.7mA·mg-1,是相同反应条件下Pt/C电流密度的1.45倍,抗甲醇性显著提高。

Fabrication of a highly dispersed Pd_(core)@Pt_(shell) electrocatalyst for the oxygen reduction reaction

Core-shell nanostructures have been widely investigated to improve the electrocatalytic perfor-mance of platinum. However, organic precursors, surfactants or high temperature are usually nec-essary during the preparation procedure. Unfortunately, these requirements limit the application of these methods on a large scale. Herein, a Pdcore@ Pt shell nanostructure was fabricated through the reduction of fcPtCU by dissociated hydrogen at room temperature without the assistance o f either a surfactant or a high-boiling point solvent. The shell thickness of this nanostructure was successfully controlled by varying the amount of fcPtCU; core-shell nanoparticles with a shell thickness of 0.45, 0.75 and 0.90 nm w ere obtained, as determined by TEM. The remarkable crystallinity and epitaxial growth of the Pdcore@ Pt shell nanostructure were revealed by HRTEM and EDS. According to ICP and XPS, surface segregation of Pt was established. The impressive ORR performance was attributed to the weak adsorption strength of the OHads species, which resulted from the electron transfer impact between the Pdcore and Ptshell. The facile and clean preparation method can be used to prepare other core-shell nanostructures under a mild atmosphere.

Synthesis of Various Metal/TiO2 Core/shell Nanorod Arrays

We present a general approach to fabricate metal/TiO2 core/shell nanorod structures by twostep electrodeposition. Firstly, TiO2 nanotubes with uniform wall thickness are prepared in anodic aluminum oxide （AAO） membranes by electrodeposition. The wall thickness of the nanotubes could be easily controlled by modulating the deposition time, and their outer diameter and length are only limited by the channel diameter and the thickness of the AAO membranes, respectively. The nanotubes＇ tops prepared by this method are open, while the bottoms are connected directly with the Au film at the back of the AAO membranes. Secondly, Pd, Cu, and Fe elements are filled into the TiO2 nanotubes to form core/shell structures. The core/shell nanorods prepared by this two-step process are high density and free-standing, and their length is dependent on the deposition time.

Cu_(core)Pt_(shell)/C纳米催化剂电催化氧还原性能

通过控制前驱体材料的比例分别为1∶1、1∶0.5、1∶2,采用两步化学还原法合成了不同壳层厚度的Cu_(core)Pt_(shell)纳米粒子。使用XRD表征纳米粒子的结构和组成,动电位扫描法测试其对氧还原反应的活性和抗甲醇性能。结果显示:所制备的材料为核壳结构,Pt壳层平均厚度约5.5 nm;Cu_(core)Pt_(shell)/C催化剂的氧还原活性随着Pt元素比例的增加而增加,都小于Pt/C催化剂,但其抗甲醇性能优于Pt/C催化剂。

Polarization properties of elliptical core non-hexagonal symmetry polymer photonic crystal fibre

In this paper, polarization properties and propagation characteristics of polymer photonic crystal fibres with elliptical core and non-hexagonal symmetry structure are investigated by using the full vectorial plane wave method. The results show that the birefringence of the fibre is induced by asymmetries of both the cladding and the core. Moreover, by adjusting the non-symmetrical ratio factor of cladding η from 0.4 to 1 in step 0.1, we find the optimized design parameters of the fibre with high birefringence and limited polarization mode dispersion, operating in a single mode regime at an appropriate wavelength range. The range of wavelength approaches the visible and near-infrared which is consistent with the communication windows of polymer optical fibres.

A Hybrid Electrode of Co_3O_4@PPy Core/Shell Nanosheet Arrays for High-Performance Supercapacitors

Herein, combining solverthermal route and electrodeposition, we grew unique hybrid nanosheet arrays consisting of Co_3O_4 nanosheet as a core, PPy as a shell. Benefiting from the PPy as conducting polymer improving an electron transport rate as well as synergistic effects from such a core/shell structure, a hybrid electrode made of the Co_3O_4@PPy core/shell nanosheet arrays exhibits a large areal capacitance of 2.11 F cm-2at the current density of 2 m A cm^(-2), a *4-fold enhancement compared with the pristine Co_3O_4electrode; furthermore, this hybrid electrode also displays good rate capability(*65 % retention of the initial capacitance from 2 to 20 m A cm^(-2)) and superior cycling performance(*85.5 % capacitance retention after 5000 cycles). In addition, the equivalent series resistance value of the Co_3O_4@PPy hybrid electrode(0.238 X) is significantly lower than that of the pristine Co_3O_4electrode(0.319 X). These results imply that the Co_3O_4@PPy hybrid composites have a potential for fabricating next-generation energy storage and conversion devices.

One-dimensional ZnS-based Hetero-,Core/shell and Hierarchical Nanostructures

A focus of the current nanotechnology has shifted from routine fabrication of nanostructures to designing functional electronic devices and realizing their immense potentials for applications. Due to infusion of multi-functionality into a single system, the utilization of hetero-, core/shell and hierarchical nanostructures has become the key issue for building such devices. ZnS, due to its direct wide bandgap, high index of refraction, high transparency in the visible range and intrinsic polarity, is one of the most useful semiconductors for a wide range of electronics applications. This article provides a dense review of the state-of-the-art research activities in one-dimensional （1D） ZnS-based hetero-, core/shell and hierarchical nanostructures. The particular emphasis is put on their syntheses and applications.