Hybrid Core Research Articles

Synthesis and characterization of poly(N-isopropylacrylamide-co-N,N′-methylenebisacrylamide-co-acrylamide) core – Silica shell nanoparticles by using reactive surfactant polyoxyethylene alkylphenyl ether ammonium sulfate

We report a novel approach based on using polyoxyethylene alkylphenyl ether ammonium sulfate (HS10) as an anion reactive surfactant, which greatly reduced the size of poly(N-isopropylacrylamide-co-acrylamide-co-N,N′-methylenebisacrylamide) [P(NIPAM/AM/MBA)] microgel core – silica shell particles. First, the microgel cores were synthesized by copolymerization of N-isopropylacrylamide (NIPAM), N,N′-methylenebisacrylamide (MBA) with a variation of acrylamide (AM) and HS10 concentration in water. It followed by silica encapsulation of the microgel cores via the addition of 3-glycidyloxypropyltrimethoxysilane (GLYMO) and tetraethyl orthosilicate (TEOS) at alkaline environment (pH 12). It is interesting to note that the size of both PNIPAM-based microgel cores and PNIPAM-based microgel core – silica shell particles were well-controlled by using a small level of HS10. Furthermore, SEM images of the hybrid core – shell particles show the well-defined spherical morphology with monodisperse particle size distribution. As expected, HS10-containing samples are covered by the porous silica shell layer, instead of continuous silica shell obtained from HS10-free samples observed in TEM images. This novel incorporation not only well controls the core size and shell morphology, leading to increase their specific surface area but also does not greatly affect the thermo-sensitivity of final products. The resultant thermo-responsive microgel core – silica shell particles with controlled particle morphology and physicochemical properties are useful for biomedical application fields.

Development and optimization of low-speed and high-efficiency permanent magnet generator for micro hydro-electrical generation system

In this paper, a low-speed and high-efficiency permanent magnet generator (LHPM generator) for micro hydro-electrical generation system was developed, and two different low-speed generators by using silicon steel and SPCC core (Common Cold Steel Plate) were fabricated and compared. The proposed LHPM generator can have high no-load electromotive force (EMF) and high efficiency at low speed by optimizing its parameters, and shows possibility to reduce its production cost by comparing the performance with different ferromagnetic materials of iron cores. Firstly, the principle of the low-speed and high-efficiency permanent magnet generating system was introduced, and the parameter design of the LHPM generator was proposed. Then the performance with different ferromagnetic materials of cores was analyzed. Finally, various Finite Element Analysis (FEA) simulation, optimization studies and experiments were performed. The cogging torque reduction method, effect of PM’s parameters, and the influence of different materials of cores were also investigated. Furthermore, as a tradeoff between the generator’s performance and the production cost, so-called hybrid core type generator, of which the rotor is made of SPCC core and the stator is made of silicon steel core was proposed. The simulation and experimental results demonstrate the effectiveness of the proposed structure.

Sound absorption of micro-perforated sandwich panel with honeycomb-corrugation hybrid core at high temperatures

A combined theoretical and numerical study is carried out to evaluate the sound absorption performance of a micro-perforated sandwich panel with perforated honeycomb-corrugation hybrid core (PHCH) at high temperatures up to 700 K. The theoretical model is established based on the classical Maa theory for micro-perforated panels and the method of electro-acoustic analogy. Validity of the model is checked against direct numerical simulations performed on COMSOL Multiphysics. Sound absorption properties of PHCH and its competitors obtained at different temperatures reveal that temperature affects remarkably their low-frequency performance. Average particle velocity in the perforation hole is numerically calculated as a function of temperature, and good agreement between sound absorption peaks and particle velocity peaks is achieved. To further demonstrate the superiority of PHCH in low-frequency sound absorption, the half-absorption bandwidths of PHCH are compared to those of its competitors at high temperatures. The influence of facesheet and corrugation are also studied, illustrating that the former plays a more significant role than the latter. The proposed sandwich structure shows promising engineering applications not only as a load-bearing structure, but also as a sound absorber, even at high temperatures.

Boosting Fuel Cell Durability under Shut-Down/Start-Up Conditions Using a Hydrogen Oxidation-Selective Metal-Carbon Hybrid Core-Shell Catalyst.

Performance degradation generated by reverse current flow during fuel cell shut-down/start-up is a big challenge for commercialization of polymer electrolyte membrane fuel cells in automobile applications. Under transient operating conditions, the formation of H2/O2 boundaries on Pt surfaces and the occurrence of undesired oxygen reduction reaction (ORR) in an anode cause severe degradation of carbon supports and Pt catalysts in a cathode because of an increase of the cathode potential up to ∼1.5 V. Herein, to directly prevent the formation of H2/O2 boundaries in the anode, we propose a unique metal-carbon hybrid core-shell anode catalyst having Pt nanoparticles encapsulated in nanoporous carbon shells for selective H2 permeation. This hybrid catalyst exhibits high hydrogen oxidation reaction (HOR) selectivity along with fully subdued ORR activity during long-term operation because of the excellent stability of the carbon molecular sieves. Furthermore, the HOR-selective catalyst effectively suppresses the reverse current flow in a single cell under shut-down/start-up conditions.

Modeling and analysis of optical properties of nanoparticles and nanofluids for effective absorption of solar radiation and their heating

This review presents a comprehensive analysis of the recent studies and advances related to optical properties of nanoparticles, their heating under solar irradiation and heat conversion, relevant equations and theoretical modeling approaches and application of nanofluids for direct absorption of solar radiation. A lot of papers including theoretical, numerical and experimental up-to-date works are reviewed and summarized carefully to give a panoramic overview of the role of the nanoparticles. Modern nanotechnology can produce various homogeneous and hybrid (core–shell) nanoparticles from different metals and materials which have unique optical and thermal properties. It was found that the application of nanoparticles selected on the basis of the presented analysis has shown remarkable properties and offers unique advantages over conventional fluids in optical absorption, thermo-physical and heating properties of nanofluids. This fact can play a crucial role in increasing the efficiency of solar energy harvesting.

Synthesis and characterization of PNIPAM microgel core–silica shell particles

We developed a simple effective approach to prepare poly(N-isopropylacrylamide-co-acrylamide-co-N,N′-methylenebisacrylamide) (PNIPAM/AM/MBA) microgel core–silica shell particles with narrow particle size distribution via the sol–gel reaction of silica precursor deposited directly on the microgel particle surface in the presence of 3-glycidyloxypropyltrimethoxysilane (GLYMO). MBA was used as the cross-linking agent for the formation of microgel with the cross-linked network structure and GLYMO used as a coupling agent. The morphology of hybrid core–shell particles including the shape, core size, shell thickness and surface roughness was governed by the key components of AM and GLYMO. PNIPAM/AM/MBA microgel core–silica shell particles show desirable spherical shape, distinct core–shell structure and raspberry-like particle morphology. In contrast, PNIPAM/MBA microgel core–silica shell particles formed without resort to AM and GLYMO result in very poor silica encapsulation, thereby leading to undesired particle morphology. Incorporation of AM units into PNIPAM/MBA microgel particles increases the lower critical solution temperature (LCST). Furthermore, encapsulation of PNIPAM/AM/MBA microgel particles by silica does not affect the LCST to an appreciable extent, but it greatly reduces the thermo-sensitivity of the hybrid core–shell particles. Finally, the feasibility of using these PNIPAM-based core–silica shell particles as drug carriers was demonstrated.

Constructing High Performance Hybrid Battery and Electrocatalyst by Heterostructured NiCo2O4@NiWS Nanosheets

It is very important to design hybrid core–shell structured electrode materials to obtain superior electrochemical and electrocatalytic performance. In this work, we reported hybrid NiCo2O4@NiWS na...

Hybrid core–shell scaffolds for bone tissue engineering

The tissue engineering applications of coaxial electrospinning are growing due to the potential increased functionality of the fibres compared to basic electrospinning. Previous studies of core and shell scaffolds have placed the active elements in the core, however, the surface response to a biomaterial affects the subsequent behaviour, thus here hydroxyapatite (HA) was added to the shell. Coaxial electrospun polycaprolactone (PCL)-polylactic acid (PLA)/HA (core–shell) scaffolds were produced in 2D sheets using a plate collector, or 3D tubes for bone tissue engineering using a rotating needle collector. The scaffolds include high hydroxyapatite content while retaining their structural and mechanical integrity. The effect of the collector type on fibre diameter, fibre alignment and mechanical properties have been evaluated, and the impact of HA incorporation on bioactivity, BMP-2 release, cell behaviour and mechanical properties for up to 12 weeks degradation were assessed. Fibre uniformity in coaxial electrospinning depends on the relative flow rate of the core and shell solutions. Using a rotating needle collector increased fibre alignment compared to a stationary collector, without affecting fibre diameter significantly, while HA content increased fibre non-uniformity. Coaxial PCL-PLA/HA fibres exhibited significantly higher bioactivity compared to PCL-PLA scaffolds due to the surface exposure of the HA particles. Apatite formation increased with increasing SBF immersion time. Coaxial tubular scaffolds with and without HA incorporation showed gradual reductions in their mechanical properties over 12 weeks in PBS or SBF but still retained their structural integrity. Coaxial scaffolds with and without HA exhibited gradual and sustained BMP-2 release and supported MSCs proliferation and differentiation with no significant difference between the two scaffolds types. These materials therefore show potential applications as bone tissue engineering scaffolds.

Experimental and numerical investigation of sandwich structures with balsa core and hybrid corrugated composite/balsa core under three-point bending using digital image correlation

Sandwich structures are commonly used in automotive, aerospace, and civil infrastructure applications due to their high strength-to-weight and stiffness-to-weight ratios. In the present work, the performance of sandwich structures with aluminum facings and two different types of core, including balsa wood core and hybrid corrugated composite/balsa core subjected to three-point bending, is investigated, both experimentally and numerically. The face sheets are 6061-T6 aluminum alloy and the hybrid core has been made of balsa wood with average density of 125 kg m−3 and E-glass woven fabric, bonded together using epoxy resin. For data acquisition during the tests, a linear variable differential transformer has been placed under the mid-span of the specimens and a digital image correlation technique has been used for monitoring the full-field strain distributions and deflection pattern as well. Continuum damage mechanics has been employed for the finite element model analysis of the three-point bending tests. In order to predict the maximum load-bearing capacity and failure modes, a wood material behavior model for balsa and a combination of Hashin and Puck failure criterion for corrugated composite were imported into ABAQUS/Explicit via VUMAT subroutines. It was found that combining balsa core with corrugated composite results in prevention of catastrophic failure and consequently gradual decrease of load-bearing capacity. Furthermore, the results demonstrate that the hybrid core increases the strength-to-mass density and stiffness-to-mass density ratios by 34.7% and 28.2%, respectively. Numerical findings have been successfully compared to experimental data, which reveals its suitability for parametric analysis of the proposed hybrid core sandwich structure.

Energy absorption investigation of square CFRP honeycomb reinforced by PMI foam fillers under quasi-static compressive load

A type of hybrid core made up of thin-walled square carbon fiber reinforced polymer (CFRP) honeycomb and Polymethacrylimide (PMI) foam fillers was proposed and prepared. Numerical model of the core under quasi static compression was established and validated by corresponding experimental results. The compressive properties of the core with different configurations were analyzed through numerical simulations. The effect of the geometrical parameters and foam fillers on the compressive response and energy absorption of the core were analyzed. The results show that the PMI foam fillers can significantly improve the compressive strength and energy absorption capacity of the square CFRP honeycomb. The geometrical parameters have marked effects on the compressive properties of the core. The research can give a reference for the application of PMI foam materials in energy absorbing structures and guide the design and optimization of lightweight and energy efficient cores of sandwiches.

Core–shell assembly of carbon nanofibers and a 2D conductive metal–organic framework as a flexible free-standing membrane for high-performance supercapacitors

A hybrid core–shell material based on carbon nanofibers and a 2D conductive metal–organic framework has been fabricated into a flexible free-standing membrane as an electrode material for supercapacitors.

Energy based design of a novel timber-steel building

Energy-based methodology is utilized to design novel timber-steel hybrid core wall system. The timber-steel core wall system consists of cross laminated timber (CLT), steel columns, angled brackets and t-stub connections. The CLT wall panels are stiff and strong, and ductility is provided through the steel t-stub connections. The structural system was modelled in SAP2000 finite element program. The hybrid system is explained in detail and validated using first principles. To evaluate performance of the hybrid core system, a 7-story building was designed using both forced-based design and energy based design (EBD) approaches. Performance of the structure was evaluated using 10 earthquakes records selected for 2500 return period and seismicity of Vancouver. The results clearly served as a good example of the benefits of EBD compared to conventional forced based design approaches.

Star‐shaped hybrid polymers as insulators for organic field effect transistors

Synthesis of star‐shaped polystyrene (PS) and poly (methyl metachrylate) (PMMA) containing a polyhedral oligomeric silsesquioxane (POSS) core are fabricated by combination of atom transfer radical polymerization (ATRP) and copper (I) catalyzed azide‐alkyne cycloaddition (CuAAC) click reaction techniques. The synthetic route proceeds in two steps; firstly, clickable alkyne‐end functionalized polymeric arms and a POSS‐(N3)8 core are prepared independently by arm‐first approach using ATRP and nucleophilic substitution reaction of octa‐(3‐chloropropyl) silsesquioxane POSS‐(Cl)8 with sodium azide. Finally, the CuAAC click reactions between inorganic‐organic hybrid core POSS‐(N3)8 and alkyne functionalized PMMA and PS arms provide the targeted star‐shaped polymers. Their chemical structures and molecular characteristics are clearly confirmed by FT‐IR, 1H‐NMR, and GPC analyses. The obtained polymers are utilized as insulators for organic field effect transistors (OFETs) using perylene as an active n‐type organic semiconductor. Compared with linear PMMA and PMMA‐POSS, the POSS‐(PMMA)8 exhibited better output and transfer characteristics for the OFET device.

Compression and low velocity impact response of sandwich panels with polyester pin-reinforced foam filled honeycomb core

Hybridization of face, core and their combination is of great interest to develop high performance composite sandwich panels. In this regards, hybrid core of ‘polyester pin-reinforced foam filled h...

Equivalent properties of composite sandwich panels with honeycomb–grid hybrid core

Combining the complementary properties of honeycomb cores and grid cores, a composite sandwich panel with honeycomb–grid hybrid core was proposed to enhance the structural performance of composite sandwich panels. However, important gaps remain in calculating the structural performance of the composite sandwich panels. In this paper, an equivalent stiffness model was proposed to analytically estimate the stiffness matrix of composite sandwich panels with honeycomb–grid hybrid core. The reliability and accuracy of the equivalent stiffness model were verified by experimental measurements from three-point bending tests. Furthermore, the effects of face-sheet thickness, core height, grid spacing, rib width and material properties on structural stiffness were investigated for the design of sandwich structures with hybrid core. The parameter studies demonstrated that core height had the most significant influence on the specific bending stiffness, while grid spacing was most important for specific in-plane stiffness of sandwich panels with carbon-fiber grid. Moreover, using carbon-fiber grid, although increases manufacturing cost, could further enhance the specific stiffness.

A Versatile Pt‐Based Core–Shell Nanoplatform as a Nanofactory for Enhanced Tumor Therapy

AbstractHypoxia, one of the representative characteristics in solid tumors, not only reduces the effectiveness of multiple treatments, but also relates to the tumor invasion and metastasis. Here, a hybrid core–shell nanoplatform to produce adequate oxygen, supporting for more effective tumor treatment, is developed. Composed of polydopamine cores, platinum nanoparticle interlayers, and zirconium‐porphyrin (PCN) shells, the hybrid core–shell nanoplatform works like a nanofactory, providing necessary products at different time and space. Platinum nanoparticle interlayers can catalyze the endogenous H2O2 to O2, which plays a dual rule in the enhanced tumor treatment. In the presence of light irradiation, O2 can be converted into the lethal reactive oxygen species by the PCN shell. In the absence of light irradiation, O2 ameliorates the hypoxic microenvironment, thereby reduces the invasion and metastasis of the tumor. Through a synergism of enhanced treatment and reduced metastasis, tumors could be treated more vigorously.

Mechanical and Acoustic Performance of Sandwich Panels With Hybrid Cellular Cores

Sandwich structures that are embedded with cellular materials show excellent performance in terms of mechanics, electromagnetics, and acoustics. In this paper, sandwich panels with hybrid cellular cores of hexagonal, re-entrant hexagonal, and rectangular configurations along the panel surface are designed. The spectral element method (SEM) is applied to accurately predict the dynamic performance of the sandwich panels with a reduced number of elements and the system scale within a wide frequency range. The mechanical performance and the acoustic performance at normal incidence of the proposed structures are investigated and compared with conventional honeycomb panels with fixed cell geometries. It was found that the bending stiffness, fundamental frequencies, and sound transmission loss (STL) of the presented sandwich panels can be effectively changed by adjusting their hybrid cellular core configurations. Shape optimization designs of a hybrid cellular core for maximum STL are presented for specified tonal and frequency band cases at normal incidence. Hybrid sandwich panels increase the sound insulation property by 24.7%, 20.6%, and 109.6% for those cases, respectively, compared with conventional panels in this study. These results indicate the potential of sandwich structures with hybrid cellular cores in acoustic attenuation applications. Hybrid cellular cores can lead to inhomogeneous mechanical performance and constitute a broader platform for the optimum mechanical and acoustic design of sandwich structures.

Organic Nanostructures on Inorganic Ones: An Efficient Electrochromic Display by Design

Improved electrochromism has been reported from a hybrid nanoheterostructure-based array designed using transition-metal oxides and conducting polymers. An improvement in color contrast, coloration efficiency, and operating voltage makes these hybrid core–shell-type nanostructures (NSs) suitable for power efficient and reversible electrochromic applications showing switching between transparent and opaque states rather than resulting in colored/bleached switching. Nanopetals (NPs) of nickel oxide have been used as the backbone to grow nanohemispheres (NHs) of polyaniline onto a fluorine-doped tin oxide electrode using a two-step synthesis methodology consisting of a hydrothermal method, followed by an electrodeposition method. The coaxial NPs/NHs core–shell arrays exhibit a better electrochromic performance compared to their individual constituents. Devices fabricated using these hybrid NSs show power efficient optical switching between transparent and opaque with fast response and a good cycle life of ap...

Photo‐Induced Programmable Morphological Transition of the Hybrid Coassembles

AbstractMorphology and nanoparticle's distribution are both key factors to the hybrid coassemblies. A fancy method to dynamically control the morphology of hybrid core–shell microspheres (CSMs) with UV light is introduced. The CSMs used here are fabricated with azobenzene (AZO) ended hyperbranched poly(ether amine) in the shell and AZO containing polyhedral oligomer silsesquioxane in the core through coassembly. Upon UV irradiation, the dynamic morphology transition from core–shell microsphere to vesicle is realized by synergistic effects and photothermal effects of AZO, resulting in the size of coassemblies increasing from 1.2 to 2.5 µm. And versatile multivesicular structures can be fixed and captured as mid‐states in taking advantage of the easy control of ON/OFF of UV light. This programmable morphology transition provides a new insight for fabricating light‐controlled hybrid materials with ideal structure in soft nanotechnology which matches with requirements in in situ tunable functions, controlled release, and so on.

One‐Step Synthesis of Hybrid Core–Shell Metal–Organic Frameworks

AbstractEpitaxial growth of MOF‐on‐MOF composite is an evolving research topic in the quest for multifunctional materials. In previously reported methods, the core–shell MOFs were synthesized via a stepwise strategy that involved growing the shell‐MOFs on top of the preformed core‐MOFs with matched lattice parameters. However, the inconvenient stepwise synthesis and the strict lattice‐matching requirement have limited the preparation of core–shell MOFs. Herein, we demonstrate that hybrid core–shell MOFs with mismatching lattices can be synthesized under the guidance of nucleation kinetic analysis. A series of MOF composites with mesoporous core and microporous shell were constructed and characterized by optical microscopy, powder X‐ray diffraction, gas sorption measurement, and scanning electron microscopy. Isoreticular expansion of microporous shells and orthogonal modification of the core was realized to produce multifunctional MOF composites, which acted as size selective catalysts for olefin epoxidation with high activity and selectivity.