Hollow Microspheres Research Articles

Non-Sacrificial Synthesis of Silica/Polymer Hollow Microspheres for Enhanced Thermal Insulation in UV-Cured Coatings

Non-Sacrificial Synthesis of Silica/Polymer Hollow Microspheres for Enhanced Thermal Insulation in UV-Cured Coatings

Self-assembly of graphene hollow microspheres anchored with FeNi3/NiFe2O4 nanocrystal for highly efficient electromagnetic wave absorption

The graphene-based electromagnetic wave absorption materials have attracted extensive attention due to their lightweight, strong absorption, broadband, and thin thickness. In this work, graphene hollow microspheres anchored with FeNi-coupled nanocrystal (GHMs@FeNi3/NiFe2O4) were synthesized using water-in-oil (W/O) emulsification and high-temperature calcination. The GHMs@FeNi3/NiFe2O4 microspheres have a homogeneous spherical morphology and a pronounced hollow structure, and the FeNi-coupled nanocrystals are homogeneously embedded in a spongy shell assembled by rGO nanosheets. Owing to the optimized impedance matching and enhanced attenuation, the GHMs@FeNi3/NiFe2O4 composites exhibit outstanding microwave absorption ability, particularly in the Ku band. The minimum reflection loss (RLmin) value can reach −58.96 dB at 14.43 GHz with a matching thickness of 2.25 mm, and the effective absorption bandwidth (lower than −10 dB) is up to 6.29 GHz (11.71–18 GHz) covering the whole Ku band. We believe that our work provides an idea for the design of high-performance absorbing composite materials.

Hydrogen production coupled with benzyl alcohol oxidation promoted by PtO-CdS hollow microsphere photocatalysts

Simultaneous H2 production and benzyl alcohol oxidation is an effective strategy for fully utilizing photoexcited electrons and holes of the photocatalysts. Herein, PtO are decorated on hollow CdS microspheres to fabricate a coupling photocatalytic system for accelerating H2 generation and selective oxidation of benzyl alcohol to benzaldehyde. The PtO-CdS hollow microspheres have been prepared by a facile hydrothermal method without any template agents. Under simulated sunlight irradiation, the 1 %PtO/CdS exhibited the highest rates of H2 evolution and benzaldehyde production. In addition, the PtO-CdS photoctalyst is stable during five cycles of photocatalytic reaction. Photoelectrochemical analyses coupled with ESR measurement demonstrated that PtO decoration not only promotes the charge separation but also improves the stability of the CdS. It is hoped that this work would provide useful information for the synthesis of CdS nanostructure for target application.

Hollow VO2 microspheres anchored on graphene as advanced cathodes for aqueous zinc-ion batteries

Vanadium dioxide-based materials have been proved to be promising cathodes for aqueous zinc ion batteries (AZIBs) due to their cost-effectiveness and high theoretical specific capacity; nevertheless, the low electronic conductivity and poor cycle stability restrict their application. Herein, hollow VO2 microspheres anchored on graphene oxide (H-VO2@GO) are synthesized via a facile simple hydrothermal reaction as high-performance cathodes for AZIBs. The hollow micromorphology of the material provides a large specific surface area and effectively alleviates the volume changes during cycling, while the anchoring of VO2 on graphene oxide greatly improves the electronic conductivity and inhibits the agglomeration and pulverization of the material. Resulting from the combination of unique micromorphology and graphene oxide anchoring, the as-prepared H-VO2@GO exhibits the impressive specific capacity of 400.1 mAh/g at 0.5 A/g and excellent cycling performance with 96.1 % of capacity retention after 1500 cycles at 10 A/g. This investigation provides a use reference for designing high-performance cathodes materials for AZIBs by optimizing the microstructure of electrode materials.

Electromagnetic shielding effectiveness of silver‐coated hollow glass microsphere‐graded short carbon fiber epoxy composite

AbstractThe present study is investigating the use of short carbon fiber (SCF) and silver‐coated hollow glass microsphere (Ag@HGM) reinforced epoxy light‐weight composites for electromagnetic interference (EMI) shielding applications in the X‐band frequency range (i.e., 8–12 GHz). The study found that Ag@HGM along with SCF significantly improved the dielectric properties of the composites and enhanced the EMI shielding effectiveness of 34.6 dB. Thermal analysis indicates that the sample shows a high rate of heat dissipation and good thermal conductivity. The dynamic mechanical analysis has indicated that the composite has improved storage modulus, glass transition temperature, and activation energy.Highlights SCF and Ag@HGM epoxy composite is fabricated for EMI shielding application. Two steps: etching and electroless coating of HGM are used for silver coating. The addition of Ag@HGM has enhanced total SE from 27.4 to 34.6 dB. EM wave gets scattered, experiences internal reflections view SCF and Ag@HGM. Additionally, enhancement of thermal and mechanical properties is observed.

Hyperactivation of lipase by oil-water interface in interfacial immobilization on hierarchical porous hollow silica microsphere: dynamics, mechanism and application

Lipases exhibit high activity at oil−water interfaces due to interfacial activation effect. In this work, the interfacial immobilization of lipase was developed based on Pickering emulsion through using lipase solution as the aqueous phase, n-hexane as oil phase, and stabilized by modified hierarchical porous hollow silica microsphere (HPHSM-C1). The prepared immobilized lipase HPHSM-C1@AY400-II achieved highest specific activity (6.4 IU/mg) with the amount of immobilized protein of 34.5 mg/g, surpassing traditional adsorptive immobilized lipase (HPHSM-C1@AY400) by 1.89-fold, and retained 70 % of residual activity after ten operational cycles. The conformational change of HPHSM-C1@AY400-II was confirmed by Fourier transform infrared. The interfacial adsorption at oil-water interface was influenced by intraparticle and surface diffusion, as evidenced by adsorption kinetic. Finally, the HPHSM-C1@AY400-II was applied in enzymatic enrichment of ω-3 polyunsaturated fatty acids (ω-3 PUFAs) in glycerides, and the content of ω-3 PUFAs in the glyceride significantly increased from 32.35 % to 54.78 % after 3 h of selective hydrolysis. This study opens a promising avenue to improve lipase activity in immobilization process, contributing to enzymatic synthesis of functional lipids.

Innovative strategy for controlling resonant frequencies of syntactic polymer foams regulating by hollow microspheres

This study aims to precisely control the resonant frequency of synthetic composite foam materials with fixed dimensions. By incorporating rigid hollow glass microspheres XLD3000(XLD) and flexible hollow polymer microspheres MFL-81GCA(MFL) into the base resin (EP), we prepared synthetic composite foams containing different volume fractions of hollow microspheres (EP-XLD and EP-MFL). We conducted tests and analyses on the density, mechanical properties, resonant frequency, and microstructure of the EP-XLD and EP-MFL systems. Results indicate that as the volume fraction of hollow microspheres increases, the flexural specific modulus of the EP-XLD and EP-MFL systems, respectively, exhibits a linear increase and decrease, and the resonant frequency shifts linearly towards higher and lower frequencies. This trend aligns with theoretical predictions, affirming that the material’s resonant frequency is closely related to its flexural modulus. This research not only deepens the understanding of the control mechanisms for the resonant frequency of synthetic composite foams but also proposes an innovative material design strategy with broad application potential, particularly in the fields of acoustics, damping, and structural materials, where it promises to significantly enhance material performance and meet specific engineering needs.

Hollow FeCoNiAl microspheres with stabilized magnetic properties for microwave absorption

Hollow FeCoNiAl microspheres with stabilized magnetic properties for microwave absorption

Properties of epoxy resin matrix composites improved by silica sol‐activated hollow ceramic microspheres

AbstractSilica sol can activate the surface of hollow ceramic microspheres and improve the properties of composite materials by improving the interface between the microspheres and the epoxy resin. The group changes on the surface of microspheres were measured using infrared spectroscopy. The microspheres were observed with a scanning electron microscope. The density, water absorption, and mechanical properties of the materials were tested using scales and mechanical testing machines. The results showed that SiO2 and silane molecules were introduced on the surface of the microspheres after treatments. As the silica sol content increased, the slurry viscosity increased by 34.5%, the composite density increased by 5.8%, and the water absorption decreased by 35.8%. When the silica sol content was 25%, the flexural strength and compressive strength of the composites were 73.49 and 116.27 MPa, respectively, which were 37.8% and 23.6% higher than those of the untreated composites, and the mechanical properties became clearly improved. High mechanical properties enable the materials to be used in deeper ocean areas.Highlights Nanoparticles are introduced onto the surface of hollow microspheres. The activated microspheres can bind better to the silane coupling agent. Silane coupling agent assisted by silica sol improved interfacial bonding. Surface activation of microspheres improves the properties of composites.

Advanced Oxidation Processes for the oxyfunctionalisation of 1,2-dichlorobenzene: a review

Catalytic oxidation is an oxidation process that converts volatile organics and water carbon in the presence of the catalyst. A catalyst is a substance that is used to accelerate the rate of reaction at a given temperature without itself being consumed during the reaction and it can be used repeatedly. This review presents catalytic oxidation of ortho-dichlorobenzene over V2O5 loaded metal oxides (TiO2, SiO2 and Al2O3), supported transition metal oxides, ABO3- type perovskites and Ca-doped FeOx hollow microspheres. The review reveals different reaction conditions in which different catalysts were used during the degradation of 1,2-dichlorobenzene. The catalytic activity performance is reviewed and compared for all the catalysts used during the degradation of 1,2-dichlorobenzene. In our previous study, catalytic oxidation of orthodichlorobenzene in the presence of ozone and the catalyst at ambient reaction conditions was studied.

Facile Synthesis of Hollow V2O5 Microspheres for Lithium-Ion Batteries with Improved Performance

Micro-nanostructured electrode materials are characterized by excellent performance in various secondary batteries. In this study, a facile and green hydrothermal method was developed to prepare amorphous vanadium-based microspheres on a large scale. Hollow V2O5 microspheres were achieved, with controllable size, after the calcination of amorphous vanadium-based microspheres and were used as cathode materials for lithium-ion batteries. As the quantity of V2O5 microspheres increased, the electrode performance improved, which was ascribed to the smaller charge transfer impedance. The discharge capacity of hollow V2O5 microspheres could be up to 196.4 mAhg−1 at a current density of 50 mAg−1 between 2.0 and 3.5 V voltage limits. This sheds light on the synthesis and application of spherical electrode materials for energy storage.

An efficient molten‐salt electro‐deoxidation strategy enabling fast‐kinetics and long‐life aluminum–selenium batteries

AbstractAluminum–selenium (Al–Se) batteries have been considered as one of the most promising energy storage systems owing to their high capacity, energy density, and cost effectiveness, but Se falls challenges in addressing the shuttle effect of soluble intermediate product and sluggish reaction kinetics in the solid–solid conversion process during cycling. Herein, we propose an unprecedented design concept for fabricating uniform Se/C hollow microspheres with controllable morphologies through low‐temperature electro‐deoxidation in neutral NaCl–AlCl3 molten salt system. Such Se/C hollow microspheres are demonstrated to hold a favorable hollow structure for hosting Se, which can not only suppress the dissolution of soluble intermediate products into the electrolyte, thereby maintaining the structural integrity and maximizing Se utilization of the active material, but also promote the electrical/ionic conductivity, thus facilitating the rapid reaction kinetics during cycling. Accordingly, the as‐prepared Se/C hollow microspheres exhibit a high reversible capacity of 720.1 mAh g−1 at 500 mA g−1. Even at the high current density of 1000 mA g−1, Se/C delivers a high discharge capacity of 564.0 mAh g−1, long‐term stability over 1100 cycles and high Coulombic efficiency of 98.6%. This present work provides valuable insights into short‐process recovery of advanced Se‐containing materials and value‐added utilization for energy storage.

Self-templated formation of hierarchically porous TiO2 hollow microspheres with fast lithium-uptake performance

Hollow TiO2 microspheres composed of low-dimensional anisotropic building blocks (such as nanowires or nanosheets) possess a hierarchical porosity and thus favor mass/Li+ transfer. However, developing an easy-control method to synthesize this type of TiO2 is still a challenge. Herein, an aerosol-assisted self-assembly method is developed to construct the nanowire-assembled TiO2 hollow microspheres (NW-TOHMS). The nanowire-intertangle configuration results in forming large surface area (∼207 m2 g−1) and hierarchical porosity with a broad pore-size distribution from 2 to 100 nm. Moreover, finite element analysis suggests that nanowire-constructed open meso-/macro-pores benefit the Li+-transport/storage kinetics. As a consequence, the NW-TOHMS electrode exhibits a high specific capacity of 117 mA h g−1 at 5 A g−1 after 1000 cycles. Excitingly, the activated carbon/NW-TOHMS Li-ion capacitors demonstrate an energy density as high as 37 Wh kg−1 at the maximum power density of 6.1 kW kg−1. This work offers a new pathway for the synthesis of mesoporous TiO2 hollow superstructures used to fast energy storage and conversion.

Coupling effects of dielectric loss in N-doped carbon double-shelled hollow particles for high-performance microwave absorption

Microwave absorbing materials with lightweight and high-performance are of great significance for electronic technique, ecological environment and defense applications. The hollow structure of carbon microspheres is beneficial to achievement of high-performance microwave absorption due to high interfacial polarization. However, the key characteristic is still unclear to control interfacial polarization. Herein, double-shelled N-doped carbon hollow particles derived from polypyrrole by self-sacrifice template were synthesized. The polymerization process was controlled by the interface between solid and pyrrole acid liquid in Fe3O4 disperse system, subsequently, micro-nano structure of carbon was tuned. The N-doped carbon double-shelled hollow particles (DSHS) show a strong dielectric loss due to coupling effect of resistance loss and interfacial polarization owing to the double-shelled hollow structure. Thus, DSHS shows a high-performance microwave absorption with minimum reflection loss (RLmin) of −75.10 dB at a thickness of 2.48 mm and effective absorption bandwidth (RL ≤ -10 dB) of 6.08 GHz and 4.05 GHz covering the whole Ku band and almost the whole X with a thickness of 2.21 mm and 3.00 mm, respectively. This work provides a simple approach for synthesizing N-doped carbon particles with distinct micro-nano hierarchical structure, double-shelled hollow microspheres assembled by nanoparticles have potential application as a high-performance MAM.

Heterodimensional hybrids assembled with multiple-dimensional copper selenide hollow microspheres and graphene oxide nanosheets for electromagnetic energy conversion and electrochemical energy storage

Heterodimensional hybrids assembled with multiple-dimensional copper selenide hollow microspheres and graphene oxide nanosheets for electromagnetic energy conversion and electrochemical energy storage

NixSy/N, S-codoped carbon (NSC) hollow microspheres derived from a novel metal organic porous polymer for high performance lithium ion batteries

Addressing the challenges of volume expansion and polysulfide dissolution in transition metal sulfide (MxSy) anodes during the cycling process of lithium-ion batteries (LIBs) is crucial for their practical application. This work utilizes a novel organic ligand containing a thiol group, 5-mercapto-1-phenyl-1H-tetrazole (PTA), to design a series of metal-organic porous polymers, which are then derivatized into N, S co-doped MxSy@carbon encapsing materials. The PTA organic ligand not only serves as a dopants source of N and S but also undergoes in-situ sulfurization with metal to form MxSy nanoparticles coated with carbon. Particularly, the derived NixSy@carbon hollow microspheres feature a unique hollow spherical carbon structure that not only mitigates the volume expansion of nickel sulfide but also shortens the ion diffusion distance while providing a significant number of active sites in LIBs. The research also revealed that variations in crystal structures caused by temperature have a profound influence on the Li+ storage capabilities of the LIBs. When evaluated as anode materials for LIBs, the NiS1.03@NSC600 demonstrates excellent reversible specific capacity and good long-life cycling stability. After 700 charge/discharge cycles, the NiS1.03@NSC600 anode maintains a reversible specific capacity of 480.4 mAh g−1 at 1 A g−1. In addition, we also evaluated CuxSy@NSC and CoxSy@NSC as anode materials, both of which demonstrated excellent electrochemical performance.

Carbon quantum dots/UiO-66@polysulfone porous microspheres fabricated via pickering emulsion template for pollutant removal

The advancement of sophisticated photocatalytic materials for environmental amelioration has become increasingly imperative in the context of persistent organic pollutants in aqueous effluents. The amalgamation of metal-organic frameworks (MOFs) with nanocomposite constituents has demonstrated promising prospects in augmenting photocatalytic efficiency. Nevertheless, obstacles persist in the realms of optimizing photon absorption and the segregation of electron-hole pairs. The application of carbon quantum dots (CQDs) within this sphere, particularly in synergy with amino-functionalized MOFs such as UiO-66-NH2, remains underexplored. In this study, we elucidate the synthesis of UiO-66@Polysulfone porous microspheres, augmented by CQDs, employing an innovative Pickering emulsion template approach for the photocatalytic degradation of tetracycline. Our findings reveal that this composite material not only manifests a distinctive hollow microsphere architecture, contributing to an elevated specific surface area, but also markedly enhances the degradation efficacies of both methylene blue and tetracycline under visible light irradiation. Moreover, this research accentuates the material's exceptional recyclability and stability, highlighting its potential as a sustainable and efficacious solution for the remediation of wastewater and organic pollutant degradation.

The superiority of TiO2 hollow microspheres over nanoparticles upon integration into a coating formulation for VOC removal

AbstractHeterogeneous photocatalysis is a promising technology for the abatement of pollutants in the air. Practical application of this technology requires the incorporation of the photocatalyst into a coating formulation. The coating can subsequently be applied on surfaces with a large geometric area, promoting various catalytic reactions. Photocatalysts, such as TiO2, appear to be most active in the form of nanoparticles. However, there is a rising concern regarding the adverse health effects of the nano‐sized particles. In this study, we investigate the photocatalytic oxidation of isopropanol, a common VOC, and demonstrate that a water‐based acrylic coating containing TiO2 micrometer‐sized hollow spheres can outperform a nanoparticle‐based coating by a factor of 10 in the rate of isopropanol removal. The porous shell structure of TiO2 hollow microspheres enables a three‐dimensional surface porosity within the coating film, thereby enhancing the access to the active catalytic surface. Our findings underscore the importance of the catalyst morphology for practical applications of photocatalytic materials when integrated into a coating formulation.

Fabrication of gold nanoparticles supported on hollow microsphere of nanosized TS-1 for the epoxidation of propylene with H2 and O2

The TS-1 microsphere was facilely prepared via a direct spray drying of the mixture containing the nanocrystal TS-1 and mother liquor. The calcined TS-1 zeolites possess a hollow structure and numerous intercrystalline mesopores, which may facilitate the diffusion properties. Au nanoparticles were loaded on TS-1 support by utilizing a deposition–precipitation process to prepare the Au/TS-1-M catalysts for propylene epoxidation in the presence of H2 and O2 conditions. The effects of the Ti and Au loadings on the structure, porosity, morphology, and catalytic performances of the Au/TS-1 catalysts have been investigated by various techniques. Under the optimized synthesis conditions (Si/Ti molar ratio = 57, 0.49 wt% Au), a propylene conversion of 6.1 % and a PO selectivity of 91.7 % were obtained on the Au/TS-1 catalyst. A PO formation rate of 186.8 gPO·kgcat.−1·h−1 was achieved at the 20th hour.

Effect of Eccentricity Difference on the Mechanical Response of Microfluidics-Derived Hollow Silica Microspheres during Nanoindentation.

Hollow microspheres as the filler material of syntactic foams have been adopted in extensive practical applications, where the physical parameters and their homogeneity have been proven to be critical factors during the design process, especially for high-specification scenarios. Based on double-emulsion droplet templates, hollow microspheres derived from microfluidics-enabled soft manufacturing have been validated to possess well-controlled morphology and composition with a much narrower size distribution and fewer defects compared to traditional production methods. However, for more stringent requirements, the innate density difference between the core-shell solution of the double-emulsion droplet template shall result in the wall thickness heterogeneity of the hollow microsphere, which will lead to unfavorable mechanical performance deviations. To clarify the specific mechanical response of microfluidics-derived hollow silica microspheres with varying eccentricities, a hybrid method combining experimental nanoindentation and a finite element method (FEM) simulation was proposed. The difference in eccentricity can determine the specific mechanical response of hollow microspheres during nanoindentation, including crack initiation and the evolution process, detailed fracture modes, load-bearing capacity, and energy dissipation capability, which should shed light on the necessity of optimizing the concentricity of double-emulsion droplets to improve the wall thickness homogeneity of hollow microspheres for better mechanical performance.