Composite Spheres Research Articles

Highly enhanced thermal conductivity from boron nitride nanosheets and MXene phonon resonance in 3D PMMA spheres composites

Efficient thermal management materials are important for the proper operation of integrated circuits. In this work, the high-yield preparation of hydroxylated boron nitride nanosheets (BNNSs) was achieved by high-temperature ablation followed by ultrasonic exfoliation without the use of highly toxic solvents. The small-sized BNNSs have similar phonon vibration properties as the large-sized MXene, and they self-assemble by electrostatic adsorption on PMMA particles to form hybrid spheres. The appearance of thermal percolation threshold indicates the successful construction of thermal conductivity pathway. The exclusion effect is more pronounced for PMMA microspheres with a larger radius, and the best thermal conductivity of 4.13 W/m·K was achieved for the composite with 20 wt% nanosheet filling. The composite exhibited good thermal performance both in the finite element model and when used as an LED heat sink. Furthermore, the incorporation of fillers can also effectively improve the thermal stability and mechanical properties of the composite. Our study provides a facile and environmental exfoliation approach of h-BN and a new strategy for the preparation of high thermal conductivity electronic packaging materials.

The Design of 3D-Printed Polylactic Acid-Bioglass Composite Scaffold: A Potential Implant Material for Bone Tissue Engineering.

Bio-based and patient-specific three-dimensional (3D) scaffolds can present next generation strategies for bone tissue engineering (BTE) to treat critical bone size defects. In the present study, a composite filament of poly lactic acid (PLA) and 45S5 bioglass (BG) were used to 3D print scaffolds intended for bone tissue regeneration. The thermally induced phase separation (TIPS) technique was used to produce composite spheres that were extruded into a continuous filament to 3D print a variety of composite scaffolds. These scaffolds were analyzed for their macro- and microstructures, mechanical properties, in vitro cytotoxicity and in vivo biocompatibility. The results show that the BG particles were homogeneously distributed within the PLA matrix and contributed to an 80% increase in the mechanical strength of the scaffolds. The in vitro cytotoxicity analysis of PLA-BG scaffolds using L929 mouse fibroblast cells confirmed their biocompatibility. During the in vivo studies, the population of the cells showed an elevated level of macrophages and active fibroblasts that are involved in collagen extracellular matrix synthesis. This study demonstrates successful processing of PLA-BG 3D-printed composite scaffolds and their potential as an implant material with a tunable pore structure and mechanical properties for regenerative bone tissue engineering.

Fractional Order Dual-Phase-Lag Model of Heat Conduction in a Composite Spherical Medium.

In the paper, a solution of the fractional dual-phase-lag heat conduction problem is presented. The considerations are related to the heat conduction in a multi-layered spherical medium with azimuthal symmetry. The final form of the analytical solution is given in a form of the double series of spherical Bessel functions and Legendre functions. Numerical calculations concern the study of the effect of the order of the Caputo derivative on the temperature distribution in a composite solid sphere, hemisphere and spherical cone.

Microwave irradiation for the production of graphene-nanodiamond composite carbon spheres

Structured spherically shaped carbon nanomaterials exhibit great application potential in various fields. In this work, sub-micron composite carbon spheres (CCSs) were successfully fabricated directly from graphite (Gra) and a small percentage of nanodiamonds (NDs) mixture under microwave irradiation. This was achieved using a scalable micro-mixing of xylene solution of NDs with a colloidal suspension of Gra in dimethylformamide (DMF), with no surfactants, catalysts, or other auxiliary chemicals. The diameters, shape, and yield of the produced CCSs were found to depend on the microwave operating parameters, including reaction time, power, and relative concentration of NDs to that of Gra. The structure of CCSs was established/optimized using the microwave-assisted chemical route at a fixed power of 1000 W for 30 min. These CCSs were characterized using scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscope (XPS), Raman spectroscopy and Fourier transform infrared spectroscopy (FTIR). This new composite structure might be useful for various applications including energy harvesting, storage, batteries, supercapacitors, etc.

Microspheres of Si@Carbon-CNTs composites with a stable 3D interpenetrating structure applied in high-performance lithium-ion battery

The huge volumetric expansion (>300 %) of Si that occurs during the charge–discharge process makes it to have poor cycling ability and weak stable structure. These factors are considered as critical obstacles to the further development of Si as anode for lithium-ion batteries (LIBs). Herein, novel 3D interpenetrating microspheres, i.e., Si@C-CNTs, which consist of silicon nanoparticles interpenetrated with carbon nanotubes (CNTs) and stuck with amorphous carbon (C) have been designed and prepared via a spray-drying assisted approach. As anode of LIBs, Si@C-CNTs microspheres can achieve high silicon loadings of around 86 % and a high initial coulomb efficiency of 80.8 %. The electrodes maintain a reversible specific capacity of 1585.9mAh/g at 500 mA g−1 after 200 cycles, and deliver an excellent rate capability of 756.4 mAh/g at 5 A g−1. The outstanding performance of Si@C-CNTs can be due to their 3D interpenetrating structure and the synergy effect between the CNTs network and amorphous carbon therein. They synergistically act as conductive matrices which significantly improve the conductivity of the composite; they also act binders and reinforcing skeleton which help the composite spheres to have stable structure. Especially, the latter (reinforcing skeleton) alleviates the volumetric effect induced by the expansion and shrinkage of silicon particles during lithiation. The unique architecture provides an ideal model that can be used to design Si-based composite anode for advanced LIBs.

Synergistic behavior of vanadium pentoxide-carbon sphere electrocatalyst towards iron-based redox flow battery and supercapacitor applications

In this paper, the multifunctional, electron-rich, unique structured vanadium pentoxide-carbon sphere (V2O5-CS) composite was used as a catalyst for energy storage devices such as iron-based redox flow batteries (IRFBs) and supercapacitors. The V2O5-CS composite was synthesized using a single-step hydrothermal method and it was found to have a nano flake-like structure deposited on the surface of spheres. The collective synergistic effect offered by V2O5 and CS in V2O5-CS enables easy flow of electrons and hence improves the reversibility, faradaic redox reaction and stability of the material. The electrocatalytic activity of the composite towards IRBF was tested to analyze the kinetic reversibility and electrode-electrolyte resistance. The charge-discharge and life-cycle studies were carried out to evaluate the stability of the electrode. V2O5-CS modified graphite felt (V2O5-CS GF) electrode was stable up to 50 cycles and the cell resulted in coulombic efficiency (CE) of 89 %. The composite along with V2O5 and CS were coated on Toray carbon electrodes were tested for supercapacitor using CV, EIS, and galvanostatic charge-discharge (GCD) to calculate the specific capacitance (Cs) offered by the material to the variation of voltage and current density applied. The V2O5-CS resulted in a specific capacitance of 612 F/g at 5 A/g and it has been found to have specific capacitance retention of 58 % up to 1500 cycles at a current density of 10 A/g. This is a pioneering work to present V2O5-CS composite as an efficient, peculiar electrocatalyst for energy storage devices.

Ultraporous Polyquaternium-Carboxylated Chitosan Composite Hydrogel Spheres with Anticoagulant, Antibacterial, and Rapid Endotoxin Removal Profiles for Sepsis Treatment.

Hemoperfusion is an important method to remove endotoxins and save the lives of patients with sepsis. However, the current adsorbents for hemoperfusion have disadvantages of insufficient endotoxin adsorption capacity, poor blood compatibility, and so on. Herein, we proposed a novel emulsion templating (ET) method to prepare ultraporous and double-network carboxylated chitosan (CCS)-poly(diallyl dimethylammonium chloride) (PDDA) hydrogel spheres (ET-CCSPD), bearing both negative and positive charges. CCS was introduced to balance the strong positive charges of PDDA to improve hemocompatibility, and emulsion templates endowed the adsorbent with an ultraporous structure for enhanced adsorption efficacy. The ET-CCSPDs neither damaged blood cells nor activated complement responses. In addition, the activated partial thromboplastin time (APTT) was prolonged to 8.5 times, which was beneficial for reducing the injection of anticoagulant in patients. The ET-CCSPDs had excellent scavenging performance against bacteria and endotoxin, with removal ratios of 96.7% for E. coli and 99.8% for S. aureus, respectively, and the static removal ratio of endotoxin in plasma was as high as 99.1% (C0 = 5.50 EU/mL, critical illness level). An adsorption cartridge filled with the ET-CCSPDs could remove 84.7% of endotoxin within 1 h (C0 = 100 EU/mL in PBS). Interestingly, the ET-CCSPDs had a good inhibitory effect on the cytokines produced by endotoxin-mediated septic blood. By developing the ET method to prepare ultraporous and double-network adsorbents, the problems of low adsorption efficiency and poor blood compatibility of traditional endotoxin adsorbents have been solved, thus opening a new route to fabricate absorbents for blood purification.

Compressive and wear properties of Al2O3p/high manganese steel composites with a spatial lattice architecture

An Al2O3p/high manganese steel (HMS) composite with a spatial lattice architecture was fabricated by gravity casting infiltrating, in which Al2O3p/HMS composite spheres were distributed in HMS matrix to form a spatial lattice architecture. The effect of the volume fraction of the composite spheres (7.6, 15.2, 22.8, and 30.4 vol%) of the architecture composite (AC) on the compressive and wear properties were investigated, compared with both HMS and the uniformly dispersed Al2O3p/HMS composite (UDC). The results showed that, with the fraction of composite spheres increasing, both the strength and wear resistance first increase up to 22.8 vol%, then decrease, however the plasticity varies just the opposite. And the AC possesses superior comprehensive properties of strength and plasticity. The yield strength of the 30.4 vol% AC reaches 557.3 MPa, being 37.0% and 79.5% higher than those of HMS and the UDC, respectively, meanwhile the strain of the AC increases to more than six times that of UDC. When the impact energy was 1.5 J, the 22.8 vol% AC exhibited the lowest wear rate, which is 36.6% and 44.1% lower than those of HMS and the UDC, respectively.

A unique ternary Ce(III)-quercetin-phenanthroline assembly with antioxidant and anti-inflammatory properties

Quercetin is one of the most bioactive and common dietary flavonoids, with a significant repertoire of biological and pharmacological properties. The biological activity of quercetin, however, is influenced by its limited solubility and bioavailability. Driven by the need to enhance quercetin bioavailability and bioactivity through metal ion complexation, synthetic efforts led to a unique ternary Ce(III)-quercetin-(1,10-phenanthroline) (1) compound. Physicochemical characterization (elemental analysis, FT-IR, Thermogravimetric analysis (TGA), UV–Visible, NMR, Electron Spray Ionization-Mass Spectrometry (ESI-MS), Fluorescence, X-rays) revealed its solid-state and solution properties, with significant information emanating from the coordination sphere composition of Ce(III). The experimental data justified further entry of 1 in biological studies involving toxicity, (Reactive Oxygen Species, ROS)-suppressing potential, cell metabolism inhibition in Saccharomyces cerevisiae (S. cerevisiae) cultures, and plasmid DNA degradation. DFT calculations revealed its electronic structure profile, with in silico studies showing binding to DNA, DNA gyrase, and glutathione S-transferase, thus providing useful complementary insight into the elucidation of the mechanism of action of 1 at the molecular level and interpretation of its bio-activity. The collective work projects the importance of physicochemically supported bio-activity profile of well-defined Ce(III)-flavonoid compounds, thereby justifying focused pursuit of new hybrid metal-organic materials, effectively enhancing the role of naturally-occurring flavonoids in physiology and disease.

A porous V/SiO2 sphere composite for the selective oxidation of benzyl alcohol to benzaldehyde in aqueous phase through peroxymonosulfate activation

A porous V/SiO2 sphere composite (VOX@SiO2) was synthesized using one-step sol-gel method. Benefiting from the redox properties of vanadium and the hydrophilic property, VOX@SiO2 showed good catalytic performances for the selective oxidation of benzyl alcohol (BzOH) to benzaldehyde (BzH) in aqueous phase through peroxymonosulfate (PMS) activation, and performed far better in water than in various organic solvents. The redox cycle of VV/VIV was supposed to be responsible for PMS decomposition in the VOX@SiO2/PMS system. The SO4∙-, 1O2 and mediated electron transfer were revealed to play a major role in the selective oxidation of BzOH to BzH. The intrinsic kinetics was analyzed to calculate the chemical reaction rate (ra) and reaction order (n = 0.33) with respect to BzOH. This study provided some insights into the development of vanadium-based heterogeneous catalyst for the selective oxidation of BzOH to BzH through PMS activation.

Effective poroelastic properties of N-layered composite sphere assemblage: An application to oolitic limestone

This article derives the effective poroelastic properties of N-layered composite assemblage. The derivation is based on the Hashin composite sphere assemblage (CSA) model and the linear elastic solution of n-layer coated inclusion-reinforced materials proposed by Hervé and Zaoui. The contribution of this study consists in the consideration of the poromechanical coupling to derive not only the bulk and shear drained moduli but also the Biot coefficient and the solid Biot modulus. The theoretical solutions are used for studying the oolitic limestone from Bourgogne (France), in which the microstructure exhibits generally an assemblage of oolite grains surrounded by a matrix. They are linked via interphase where most of the macropores locate. A two-step homogenisation scheme is proposed. The first step consists in upscaling the mesoscopic poroelastic properties of each porous phase by using the differential self-consistent scheme. In the second step, the three different porous constituents (oolite, ITZ and matrix) are homogenised using the CSA model. Results are validated against the data collected from the open literature.

Three-Dimensional Hierarchical Hydrotalcite–Silica Sphere Composites as Catalysts for Baeyer–Villiger Oxidation Reactions Using Hydrogen Peroxide

The development of effective, environmentally friendly catalysts for the Baeyer–Villiger reaction is becoming increasingly important in applied catalysis. In this work, we synthesized a 3D composite consisting of silica spheres coated with Mg/Al hydrotalcite with much better textural properties than its 2D counterparts. In fact, the 3D solid outperformed a 2D-layered hydrotalcite as catalyst in the Baeyer–Villiger reaction of cyclic ketones with H2O2/benzonitrile as oxidant. The 3D catalyst provided excellent conversion and selectivity; it was also readily filtered off the reaction mixture. The proposed reaction mechanism, which involves adsorption of the reactants on the hydrotalcite surface, is consistent with the catalytic activity results.

Effects of internal swelling on residual elasticity of a quasi-brittle material through a composite sphere model

This paper describes the development of a micromechanical-based constitutive model accounting for the effect of internal expansion on the residual elasticity of a Hashin composite material. This material is made of spherical inclusions that are subjected to gradual swelling within a quasi-brittle matrix. The main focus of this work is to describe and analyze the material mechanical response, with an additional focus on the internal swelling’s effect on the stress–strain response and residual elasticity. Microstructural features and parameters of major importance for the mechanical responses were identified. The innovative characteristics of the proposed approach are summarized as follows: (1) a full determination of the physics of a complete-damage problem throughout the whole process of inclusion swelling with upscaling techniques, which transfers the microcrack-related properties from the lower scale to upper scale; and (2) an evolution of the mechanical fields and the corresponding residual elasticity for various inclusion swelling levels. Concerning the matrix–inclusion composite, it was hypothesized that only the matrix was susceptible to cracking, with varied degrees of damage, whereas the inclusions behave elastically and the elastic modulus of the expanding inclusions remains constant. It is to emphasize that the gradual swelling of inclusions is modeled by an increasing strain in the current micromechanical-based constitutive model, and the microcracks are represented by a set of randomly oriented penny-shaped microcracks with identical radii (namely, closed cracks). The main contribution of the current research is to establish the exact mathematical solutions for the mechanical fields (stress, strain) caused by the swelling of the inclusions (mechanical loading) and derive the effective residual elasticity of a composite (structural response) subject to internal expansion and quasi-brittle damage. Based on the assumption of closed cracks that could be extended to open cracks in the upcoming work, the results proposed by the present paper help to understand the non-linear mechanical behavior of quasi-brittle materials subject to microcracking and provide a theoretical framework to be used as academical benchmark for numerical simulations.

High-efficiency graphene oxide membranes intercalated by hollow TiO2 nanospheres and CNS@LDH composite spheres for enhancing dye separation from wastewater

Textile wastewater pollution with dyes has become a major source of water pollution. In the study, GO and composite nanospheres (CNS@LDH and HOTiO2) were used to form the composite materials by electrostatic self-assembly method, and the composite materials vacuum filtration on the surface of CA membrane to prepare the composite membranes for dyes separation. Among them, GO was used as a vertical separation layer in dyes separation, while the hollow structure of HOTiO2 nanosphere with a large specific surface area provided more adsorption sites, and the CNS@LDH nanosphere with core–shell structure played the role of expanding GO sheets and preventing HOTiO2 from collapsing. Compared with the GO membrane, the water flux of three dyes produced by GO/HOTiO2/CNS@LDH composite membrane increased by 18 times with a rejection rate of 99%. In addition, after 10 cycles of experiments, GO/HOTiO2/CNS@LDH composite membrane retained a rejection rate of over 98% with the flux of 79 L∙m−2∙h−1∙bar−1 for MB. GO/HOTiO2/CNS@LDH composite membrane retained a stable rejection rate on three dyes under extreme pH and ionic strength conditions. The composite membrane combined the adsorption and isolation effects of GO, HOTiO2, and CNS@LDH, which significantly enhanced the separation performance of dye wastewater. Accordingly, the GO/HOTiO2/CNS@LDH composite membrane has great potential in practical wastewater treatment.

Facile Preparation of Millimeter‐Sized Sodium Alginate‐Silica Composite Spheres for Highly Selective Adsorption of Heavy Metal Ions

AbstractMillimeter‐sized (∼3.5 mm) sodium alginate‐silica composite spheres with macroporous structure and functional groups of amino‐ (NH2‐SiO2/SA) and sulfhydryl (SH‐SiO2/SA), respectively, were successfully prepared by a simple hydrothermal copolycondensation. The obtained materials were characterized by FT‐IR, SEM, XPS, N2 adsorption‐desorption techniques, and their heavy metal ion adsorption performance was evaluated in detail under different conditions. Characterization results revealed that the functional group plays a key role in the selectivity of metal ions, that is, NH2‐SiO2/SA preferentially adsorbs the relatively hard Pb(II) ions while SH‐SiO2/SA favors the softer Ag(I) ion, which is attributed to the fact that S atoms are softer donor than N atoms. The adsorption kinetics and the adsorption equilibrium fitted well with the pseudo‐second‐order model and Langmuir adsorption isotherms, respectively. The adsorption experiments showed the maximum adsorption capacities of Pb(II) for NH2‐SiO2/SA and Ag(I) for SH‐SiO2/SA are 460 mg/g and 417 mg/g, respectively, giving good stability without a significant decrease in 5 recycles. Therefore, the synthesized materials display promising adsorbents for recycling heavy metal pollutants from wastewater due to their good selectivity, high adsorption capacity, stability and easy recovery due to their large size.

Potential one-pot synthesis of spherical magnesium silicate powder by mechanical milling

Synthetic magnesium silicate finds applications in adsorbents, catalysis, pharmaceuticals, foods, cosmetics, and in oil industry. This study introduces a method for potential one-pot preparation of narrowly sized, spherical magnesium silicate powders. After initial synthesis by precipitation from magnesium sulphate and sodium metasilicate solutions, the magnesium silicate precursor was ball-milled with two immiscible liquids, forming a particle-loaded emulsion. Hexane formed the continuous phase; the droplet phase was formed by either acetonitrile, methanol, or water-methanol mixtures. Suspended precursor particles were refined, their fragments became trapped in the droplets, where they were eventually compacted into composite spheres. Prepared spherical powders were characterized using scanning electron microscopy, nitrogen sorption, and low angle laser light scattering. The synthesized powders exhibited narrow size distributions with modes from 3.3 to 92 μm. The spherical powders showed an enhanced flowability and had specific surface areas comparable to or higher than the precipitated precursor powders.

Construction of a bioinspired Fe3O4/N-HCS nanozyme for highly sensitive detection of GSH

The catalytic synergy of different nanomaterials is a potential technique used to develop a highly active and stable nanozyme. Here, magnetite on nitrogen-doped hollow carbon sphere (Fe3O4/N-HCS) composites were prepared through solvent thermal method and exhibited excellent oxidase and peroxidase-like catalytic activity under different pH levels. The dual enzyme-like catalyzed reaction of Fe3O4/N-HCS conformed to the typical Michaelis–Menten kinetics, and Fe3O4/N-HCS had a strong affinity for substrate 3,3′,5,5′-tetramethylbenzidine (TMB) with H2O2. The remarkable performance of the composites was achieved by the synergistic effect of Fe3O4 and N-doped activated graphite carbon, which accelerated the formation of O2•- and •OH during the dual enzyme-like catalytic reaction. Furthermore, an effective colorimetric glutathione (GSH) sensor with a wide linear range from 0.02 µM to 250 µM and a detection limit as low as 9.3 nM was constructed based on the superior peroxidase-like activity of Fe3O4/N-HCS. The convenient colorimetric sensor monitored the content of GSH in the serum of mice, and the detection results were satisfactory, with a recovery of 96–103% and an RSD between 0.80% and 3.30%. This study discussed the internal mechanism of Fe3O4/N-HCS nanozyme and developed an efficient method for GSH detection to expand nanozyme application in bioanalysis.

One-Step Solvothermal Synthesis of Ni Nanoparticle Catalysts Embedded in ZrO2 Porous Spheres to Suppress Carbon Deposition in Low-Temperature Dry Reforming of Methane

Ni nanoparticle catalysts embedded in ZrO2 porous spheres and ZrO2 porous composite spheres, SiO2-ZrO2, MgO-ZrO2, and Y2O3-ZrO2, with 83−115 nm diameter and 167–269 m2/g specific surface area were prepared by a one-pot and one-step solvothermal reaction from precursor solutions consisting of Ni(NO3)2‧6H2O, Zr(OnBu)4, and acetylacetone in moist ethanol combined with either Si(OEt)4, magnesium acetylacetate, or Y(OiPr)3. The obtained Ni catalysts have high specific surface areas of 130–196 m2/g, even after high-temperature reduction by H2 at 450 °C for 2 h. They were utilized as catalysts for low-temperature dry reforming of methane (DRM) at 550 °C to suppress carbon deposition on Ni nanoparticles. The Ni catalysts embedded in SiO2-ZrO2 and Y2O3-ZrO2 demonstrated high catalytic activity and long stability in the reaction. Moreover, carbon deposition on Ni nanoparticles in the DRM reaction was effectively suppressed in when using the SiO2-ZrO2 and Y2O3-ZrO2 composites.Graphical abstract

Inactivation of bacteria present in secondary municipal wastewater effluent using the hybrid effect of Fe–TiO2 catalyst

A low-cost waste-driven visible active iron-titanium oxide composite was fabricated for the treatment of real municipal wastewater. The structured composite was characterized using morphological and spectroscopic techniques such as FE-SEM, XRD, UV-DRS, indicating that the fabrication procedure could uniformly coat the TiO2 particles over the clay-supported composite spheres. The iron-titanium oxide composite was efficient in introducing a hybrid effect of photocatalysis and photo-Fenton that is being facilitated by the use of waste foundry sand (WFS) and waste fly ash (WFA) (both natural sources of iron) with a TiO2 layer on the outer surface. The main emphasis was given to the disinfection of bacteria along with the degradation of organic matter in terms of BOD and COD present in municipal wastewater. This hybrid technology showed 100% inactivation of bacteria with optimized parameters such as 0.9 g L−1 of H2O2 dose, 5.5 pH, and 100% surface area covered with the catalyst in 60 min of treatment time. 54% and 40% reduction in BOD and COD was also observed in 60 min. The kinetic rate constant was found to be 2 times higher in the hybrid process as compared to the individual process. The damage to the cell wall was confirmed by potassium ion leakage and FE-SEM analysis. Fe–TiO2 composites demonstrated excellent stability even after recycling 35 times, indicating the lasting durability of the composites. The findings of this study demonstrate the possibility for waste materials to be used as a viable approach for the bacterial inactivation application with the potential of the field-scale application.

Hierarchical MnO2/hollow carbon spheres composites for asymmetric supercapacitors with enhanced performance

Hierarchical MnO2/hollow carbon spheres composites for asymmetric supercapacitors with enhanced performance