Hollow Composites Research Articles

Fabrication on a Recycled and Wide-Band Absorber by 3D Printing

A recycled novel hollow pyramid absorbing structure added the carbonyl iron particles (CIPs) and FeSiAl was fabricated in the 3D printing process. The printed wires added the CIPs in the printer were made by the extruder. The electromagnetic parameters of the printed wires were measured in the vector network analyzer. The density of the composite could be controlled by setting the filling ratio in the printing process. The permittivity and permeability of the hollow composite were derived and then the reflection loss of the composite could be simulated. The results showed the pyramid absorbing material had the good absorbing property, and as the FeSiAl plate was the substrate the absorbing property in the low frequency 2-4GHz could be improved while the absorbing property in the high frequency 4-18GHz was better. The frequency band (RL<-10 dB) could be widened to 2.7-18 GHz with filling ratio 70% and the density could be decreased from 4.24 g/cm2 to 3.08 g/cm2, the total thickness of the pyramid was only 59.71mm.

Self-templated formation of AgCl/TiO2 hollow octahedra for improved visible-light photocatalytic activity

Composite semiconductor photocatalysts with hollow structures can present excellent photocatalytic performance by combining the advantages of composite photocatalyst and hollow structures. However, it is a great challenge to develop a facile synthetic route to realize the composite hollow nanostructures. In the paper, AgCl/TiO2 composite hollow octahedra were synthesized by a facile self-templated method via the direct addition of Ag2O octahedron template into TiCl4 ethanol solution. In the case, AgCl and TiO2 nanoparticles can be simultaneously formed to construct the shell of hollow octahedra along with the alcoholysis and hydrolysis of TiCl4 and the reaction of releasing H+ and Cl− ions with Ag2O template. Obviously, the synthetic method showed some advantages of economic reaction steps and uniform component distribution. After AgCl/TiO2 is illuminated by visible light, partial Ag metal can form in the sample due to the photosensitive property. Further photocatalytic results indicated that the Ag/AgCl/TiO2 hollow octahedron photocatalyst exhibited excellent photocatalytic activity and stability of performance. Importantly, the present Ag2O self-template method was also extended for the synthesis of other hollow octahedra such as AgCl/Bi2O3, AgCl/SnO2 and AgCl. Thus, the present work may provide new insights into design and synthesis of other hollow octahedron photocatalysts.

Stabilizing the nanostructure of SnO2 anode by constructing heterogeneous yolk@shell hollow composite

Herein, to effectively stabilize the nanostructure of SnO2 anode during long repeated discharge/charge process, a well-designed TiO2@Void@SnO2@C hollow nanospheres (defined as TiO2@Void@SnO2@C HNSs) composite with a distinctive heterogeneous yolk@shell hollow nanostructure has been prepared. The TiO2@Void@SnO2@C HNSs consists of core@shell SnO2@C hollow nanospheres (shells) with built-in TiO2 hollow nanospheres (yolks) (namely, TiO2 hollow nanospheres in SnO2@C hollow nanospheres). Thus, the TiO2@Void@SnO2@C HNSs has three main advantages in lithium storage in terms of structure. Firstly, the TiO2, as a robust built-in structure support, can restrain SnO2 from collapsing inward into the hollow cavity. Secondly, the inherently adequate free space including void (between shells and yolks) and hollow cavity as well as flexible carbon coating can accommodate the volume variation of SnO2, and therefore boosts the structural stability of whole composite. Finally, the good conductive carbon coating can improve the conductivity of entire composite, hence promotes the electrochemical reaction kinetics of lithium storage. As a result, the TiO2@Void@SnO2@C HNSs delivers a high capacity of 662 mAh g−1 after even 500 cycles as well as good rate properties, showing outstanding lithium storage performance as well as great potential as a high-performance anode for lithium-ion batteries.

Application of Hyperelastic Materials in a Composite Hollow Brick for Assessing the Reduction of Dynamic Loads - Numerical Analysis

The article addresses the use of hyperelastic materials to evaluate the redistribution of stresses in a composite structural hollow brick by means of numerical analysis. Both rubber and concrete were modelled as hyperelastic materials with appropriate energy potential. The concrete was modelled on the Murnaghan potential, while the rubber was modelled on the Zahorski potential. The analysed prefabricated hollow brick was loaded with a force impulse. As a result, redistribution of effective stress was observed, which was important for the evaluation of the operation of the analysed prefabricated product. The presented numerical analysis was carried out using the ADINA program.

Coral-like CoP hollow composites as effective host cathodes for lithium-sulfur batteries

Designing a better framework for anchoring sulfur is critical for lithium-sulfur battery. Coral-like CoP composites with interconnected pore channels were synthesized via precipitation and phosphorization and were used as the host materials for sulfur (CoP@S). The developed unique architecture possesses the ability to both physically confine polysulfides and chemically bind these species inside the host surface, efficient pathways to facilitate electron/ion transportation, good structural durability to buffer the volume variation of sulfur, and has an elastic protecting shell layer to block the soluble of polysulfides. Owing to these advantages, the resulting CoP@S electrode delivered a high charge capacity of 766 mAh/g with high first columbic efficiency of 98.2% at 0.2 C, good rate capability of 586 mAh/g at 1 C, and good long cycling stability (with a capacity of 438 mAh/g after 500 cycles at 2 C), suggesting excellent high-rate long cycling performance.

Preparation of Graphene–Polypyrrole Hollow Sphere by Pickering Emulsion Method and Their Electrochemical Performances as Supercapacitor Electrode

Graphene–polypyrrole hollow sphere composite was synthesized for the first time via Pickering emulsion polymerization using graphene oxide as Pickering stabilizer. It was found that polypyrrole and graphene were well hybrid and all graphene–polypyrrole composites had a uniform hollow sphere structure, whose diameters gradually decreased as the pyrrole content decreased. The electrochemical properties of the composites as supercapacitor electrode were investigated. The test results displayed that the specific capacitance of the optimal ratio of composite could reach 238[Formula: see text]F/g at a current density of 1[Formula: see text]A/g, and a 90.7% capacitance retention could be achieved after 1500 cycles, which was a significant improvement compared with the 62.2% retention of pure polypyrrole.

Hollow Nanospheres of Co/N‐C Composite as an Efficient Nonprecious Electrocatalyst for Oxygen Reduction Reaction

AbstractHollow nanospheres of Co/N−C composite have been synthesized using silica spheres with solid core and mesoporous shell (SCMS) as hard template and cobalt protoporphyrin as the precursor of C, N and Co by carbonization and etching. With the doping of only 0.68% Co into the hollow composite, activity and selectivity of ORR have been greatly facilitated. Moreover, hollow Co/N−C composite displays good electrochemical durability and tolerance to methanol crossover effect. The excellent catalytic performance of hollow Co/N−C nanospheres towards ORR can be ascribed to their unique hollow structure with mesopores, homogeneously distribution of Co nanoparticles, and suitable doping of N into carbon.

MOF-Based Nanotubes to Hollow Nanospheres through Protein-Induced Soft-Templating Pathways.

A controllable and facile strategy is established for constructing metal–organic frameworks‐based (MOF‐based) hollow composites via a protein‐induced soft‐templating pathway. Using metal‐sodium deoxycholate hydrogel as soft‐template, nanotubes are gained while the protein is absent. With the presence of protein, hollow nanospheres structure are prepared by changing the amount of protein. To verify the universality of the proposed pathway, two kinds of proteins (Burkholderia cepacia lipase and penicillin G acylase) and three kinds of MOF (ZIF‐8, ZIF‐67, and Fe‐MOF) are adopted as model proteins and materials, and the obtained protein‐containing composites (named protein@H‐MOF) possess high bioactivity and stability. This proposed strategy provides a facile method for preparing MOF‐based composites under mild conditions, facilitating the applications of MOF in the fields of biocatalyst construction, biomolecule encapsulation, and drug delivery.

Hollow metal organic frameworks composite prepared via an “escape from the cage” strategy

A step-by-step self-assembly and concurrent self-etching strategy that differs from previous methods used to prepare SiO2@UiO-66-NH2 hollow composite has been reported. The magnetic core was selectively etched to generate a hollow metal-organic framework superstructure. The physical and chemical properties were characterized by TEM and SEM techniques, composition by SEM-EDX. Benefit from the efficient mass transfer and enhanced active sites accessibility, the hollow SiO2@UiO-66-NH2 composite showed higher or comparable catalytic activity than the nano-sized UiO-66-NH2 in the Knoevenagel condensation as a solid basic catalyst. Furthermore, it could be recovered and stable in terms of activity and structure when recycled for at least four times.

Porous hollow composites assembled by NixCo1-xSe2 nanosheets rooted on carbon polyhedra for superior lithium storage capability

Transition metal chalcogenides (TMCs) have attracted considerable interest owing to their satisfied theoretical capacity, good safety and environmentally benign nature in lithium-ion batteries (LIBs). However, the poor conductivity as well as the severe volume changes during the discharge-charge process cause capacity fading rapidly, which severely impede the practical applications of TMCs. To address this challenge, a hollow hybrid architecture assembled by NixCo1-xSe2 nanosheets and strongly coupled porous carbon have been rational designed. Within this structure, the integration of nanosheets rooted on the surface of porous carbon not only provide three-dimensional conductive network but also offer plentiful pathways and active sites for electrolyte penetration and Li storage, and buffer a large volume expansion/contraction caused by lithium intercalation/deintercalation. As evidenced by electrochemical measurements, the NixCo1-xSe2/C composites used as anodes in LIBs exhibit a superior reversible high capacity of 1667 mA h g−1 at current density of 2.0 A g−1 over 600 cycles and an outstanding rate capability (1580 and 1093 mA h g−1 at 3.2 and 6.4 A g−1, respectively).

N-Doped Hollow Carbon Spheres/Sheets Composite for Electrochemical Capacitor.

Functional carbon materials with a combination of 0 dimension and 2 dimension are particularly interesting in the electrochemical field owing to the low density, high surface area, and strong ion-bearing capacity. Especially, hollow mesoporous carbon spheres (0 dimension) and nanosheet (2 dimension) composite hollow porous carbon spheres and nanosheet (HMCS/S) have received much attention as electrochemical capacitor electrode materials. However, it is challenging for effective preparation of this complex composite structure. In this work, a novel and simple procedure to prepare N-doping HMCS/S (N-HMCS/S) is presented. This approach adopted silica spheres as the core and employed [C18Mim]Br and tetraethyl orthosilicate as the structural directing agent for the formation of the flaky/spherical hybrid structure. The unique structure of nanosheets embedded by hollow carbon spheres and N-doping characteristics endow N-HMCS/S with good performance in electrochemical capacitor with high specific capacity (196.5 F g-1) in the three-electrode system and excellent high-rate capability with retention of 61.5% in the two-electrode system.

Fabrication and absorbing property of the tower-like absorber based on 3D printing process

The tower-like absorbing structures were designed and fabricated by the 3D printing process to achieve the good absorbing property and low density. The absorbing composite was composed of the carbonyl iron particles (CIPs) and the polylactic acid (PLA). The scanning electron microscopy was done to characterize the composite morphology, and X-ray diffraction (XRD) patterns were done to analyze the particle crystal grain structure. The complex permittivity and permeability of the printed wires were measured using a vector network analyzer, and the permittivity and permeability of the hollow composite were derived, the reflection loss (RL) of the composite could be simulated. The results showed that the tower-like absorbing structure had the good absorbing property, and based on the printing pathway the density of the composite could be decreased as the filling ratio was set. The frequency band (RL < −10 dB) was 12.9–18 GHz with filling ratio 70% and 9.5–18 GHz with filling ratio 100%. While as the microwave was oblique, the tower-like absorber had the better absorbing property as the incident angle was larger than 70°, the oblique RL was less than −20 dB in 12–18 GHz, which was about 11.2 dB lower than that of the simple pyramid.

Selective fabrication of hollow and solid polysaccharide composite fibers using a microfluidic device by controlling polyion complex formation

Natural polysaccharides are an important class of biomaterials that have attracted significant research interest for biomedical applications because of their high biocompatibility, biodegradability, and bioactivity. In this work, we fabricated water-insoluble composite hollow and solid fibers made of polyion complexes of chondroitin sulfate C (CS) and chitosan (CHI) using a single microfluidic device. A coaxial two-phase microfluidic device was constructed from stainless-steel needles and glass fibers, and CHI solutions and CS solutions were continuously infused into the core and sheath channels, respectively. The obtained fibers were flexible and homogeneous and had diameters of a few hundred micrometers. Hollow fibers were formed using water as the solvent of CS, while core-filled solid fibers were obtained using 20% (v/v) ethanol. The respective mechanisms for the fabrication of the hollow and solid fibers were discussed. An increase in the sheath flow rate or decrease in the core flow rate reduced the diameters of the fibers, while a reduction in the concentration of the CHI solution reduced the thickness of the hollow fibers. Furthermore, bovine serum albumin, used as a model protein, could be incorporated in the hollow and solid fibers by mixing them in the core flow solution. These results suggested the great potential of microfluidic techniques for the preparation of hollow and solid polysaccharide fibers. Hollow and solid fibers made of polyion complexes of chondroitin sulfate C (CS) and chitosan (CHI) were selectively fabricated using a coaxial two-phase microfluidic device. The selective fabrication was successfully achieved only by changing the solvent of the sheath flow that contained CS. Proteins and nanomaterials could be incorporated in both fibers by mixing them in the core flow, CHI-containing solutions. Results suggested the great potentials of microfluidic techniques for preparation of polysaccharide hollow and solid fibers.

RETRACTED: A transparent pressure-sensitive adhesive with high electrical conductivity based on water-soluble nano core-shell hollow composite

This article has been retracted: please see Elsevier Policy on Article Withdrawal ( https://www.elsevier.com/about/our-business/policies/article-withdrawal ). This article has been retracted at the request of the authors. The authors reported that their attempts to reproduce critical results in the paper were unsuccessful in their subsequent study. The Editors decided to retract the paper. The authors would like to apologize for this error on their part and profoundly regret any inconvenience and confusion that it might have caused.

Pretreatment Effect on Ceria‐Supported Gold Nanocatalysts for CO Oxidation: Importance of the Gold–Ceria Interaction

AbstractThe encapsulated Au/CeO2 hollow composite shows the effects of different pretreatment conditions on CO oxidation, showing complete conversion temperatures for CO in the order O2 pretreatment (T100=74 °C)&gt;N2 pretreatment (T100=142 °C)&gt;CO pretreatment (T100=167 °C). Because of the good confinement provided by the uniform pores of as‐prepared CeO2, the size of deposited Au nanoparticles embedded in the pores of CeO2 can be well controlled. Pretreated Au/CeO2 catalysts have a good stability with no clear deactivation even after 70 h. A systematic characterization was performed by employing various techniques (XRD, H2 temperature‐programmed reduction, scanning transmission electron microscopy with energy‐dispersive spectroscopy, Raman spectroscopy, X‐ray photoelectron spectroscopy, and in situ diffuse reflectance infrared Fourier transform spectroscopy) to understand the importance of the Au–CeO2 interaction. This revealed that the O2 pretreatment may result in (a) the migration of lattice oxygen atoms to the surface region and clearly increased number of oxygen vacancies in CeO2; (b) the increase of Au−Ox and Au−Ox−Ce bond lengths; (c) the creation of electron holes in the CeO2 substrate and electron deficiencies in Au nanoparticles as well as a strong Au–CeO2 interaction; and (d) increased number of bicarbonates on the surface and Auδ+−CO bonds were produced during CO oxidation. All these features are responsible for an overall enhanced activity of CO oxidation and high durability of the Au/CeO2 hollow composite.

Formation of uniform magnetic C@CoNi alloy hollow hybrid composites with excellent performance for catalysis and protein adsorption.

Metallic nickel- or cobalt-based composites with hollow nanostructures such as nanocages can serve as both advanced catalysts and protein adsorbents owing to their high surface area and increased active sites; hence, they have aroused great interest. Herein, we report a facile route to synthesize hollow carbon spheres (HCS) embedded with bimetallic NiCo nanoparticles (NPs) with hollow structures by using NiCo hydroxide layered nanosheet functionalized carboxyl polystyrene spheres (CPS) as a template and polydopamine (PDA) as both the carbon precursor and reductant. This unique hierarchical architecture, including meso- and macro-pores, provides a large specific surface area (244 m2 g-1) and efficient channels for the diffusion of small molecules and biomacromolecules (protein). These features greatly facilitate the excellent performances of C@CoNi for the reduction of 4-nitrophenol and His-rich protein adsorption. Moreover, the size of the surficial CoNi NPs can be facilely modulated by changing the calcination temperature, which can effectively control the catalytic and adsorption performances of the as-prepared nanocomposites. The as-prepared C@CoNi is employed as a catalyst to investigate its catalytic performance in the reduction of 4-nitrophenol (4-NP). Furthermore, the nickel nanoparticles decorated on the hollow microspheres display a strong affinity to His-rich proteins (BHb and BSA) via specific metal affinity forces between the polyhistidine groups and nickel nanoparticles.

Nitrogen-doped carbon nanotube supported double-shelled hollow composites for asymmetric supercapacitors

A double-shelled hollow structure N–C@NiMoO4 composite was prepared taking N-doped carbon nanotubes as a skeleton, and exhibited high electrochemical performance for supercapacitors.

Conjugated system in metal-free 1D polyaniline nanotubes/carbon nitride hollow composites with strong adsorption and enhanced visible-light photocatalytic activities

Metal-free 1D polyaniline nanotubes/carbon nitride (PNCN) hollow composites are fabricated by self-assembly chemisorption and solvent evaporation method for the first time. The results show that carbon nitride (g-C3N4) is successfully covered onto polyaniline (PANI) nanotubes. Due to similar electronic structures of nitrogen-rich materials of PANI and g-C3N4, the combination of two π-conjugated system not only benefits the separation of photogenerated charge carriers but also increases the light absorption range of g-C3N4. The compact contact of the PANI nanotubes and g-C3N4 nanosheets as well as their matched energy level is the determinant factor for interfacial heterojunction. Specially, the hollow 1D “Janus” heterojunction impels photogenerated charge pairs to separate and transfer to opposite directions in a short diffusion path, with the additional benefits of exposure of more active sites and transmission of reactants for catalytic surface reactions. As expected, PNCN composites are photoactive and exhibit enhanced photocatalytic performance under visible-light irradiation over pure g-C3N4 and PANI nanotubes. In addition, PNCN composites possess strong adsorption capacity. This versatile 1D PNCN hollow composites prepared from a cost-effective and green process have potential applications in catalysis, drug delivery system, sensors, and energy storage and conversion.

PDA-meditated green synthesis of amino-modified, multifunctional magnetic hollow composites for Cr(VI) efficient removal

Abstract Employing mussel-inspired concept, a controllable “Sol-Gel-like” condensation of dopamine (DA) and aminosilane coupling agents (A1, A2, A3 represent APTMS, TSPED and TPDA, respectively) was undertaken to synthesize magnetic hollow composites (Fe 3 O 4 @A/PDA), aiming for removing Cr(VI) from wastewater. Compared to reported magnetic amino-functionalized composites for heavy metal removal, it is a new green process via post-grafting pathways that can avoid using organic solvents and high-temperature treatment. Structural characterization and batch experiments are correlated to illustrate the adsorption performance of resultant composites. Upon screening resultant adsorbents, Fe 3 O 4 @A2/PDA exhibited the highest adsorption capacity; the maximum Cr(VI) removal amount could be up to 284.1 mg g −1 at 298 K and pH 2.0. The pseudo-second-order and Langmuir model preferably fitted the adsorption process, besides, the activation energy is 7.17 kJ/mol −1 . The hollow composites could be easily separated from solutions by a magnet, and over 70% Cr(VI) could be removed even after five cycles. Electrostatic attraction and reduction reaction could be used to explain the adsorption mechanism that on the basis of XPS analysis. According to thermodynamic analysis, the adsorption is a spontaneous endothermic process. The high Cr(VI) adsorption capacity, fast adsorption kinetics and easy separation properties of hollow Fe 3 O 4 @A2/PDA composites make it be potential to alleviate Cr-containing aqueous solutions.

Construction of hybrid hollow architectures by in-situ rooting ultrafine ZnS nanorods within porous carbon polyhedra for enhanced lithium storage properties

Constructing hybrid hollow composites based on metal chalcogenides and nanocarbon materials is of great interests for electrochemical energy storage applications. In this work, a metal-organic framework (MOF)-engaged template strategy is developed to mediate the in-situ formation of ultrafine ZnS nanorods rooted in the hollow carbon polyhedra (denoted as ZnS NR@HCP). The synthesis is realized through a simultaneous carbonization and sulfidation of Zn-based zeolitic imidazolate framework (ZIF-8) template at elevated temperatures. The as-prepared hybrid hollow composites exhibit a highly porous and robust structure with intimate coupling between ZnS nanorods and carbon supports, which provides facile ion and electron transport pathways as well as high mechanical stability. When evaluated as anode materials for lithium-ion batteries, these unique ZnS NR@HCP architectures manifest excellent lithium-storage performance in terms of ultrahigh reversible specific capacity (840mAhg−1 after 300 cycles at 600mAg−1) and exceptional rate capability (1388, 1063, 962, 824 and 608mAhg−1 at 100, 200, 400, 800 and 1600mAg−1).