Hollow Spheres Research Articles

Preliminary Investigation on Mechanical Properties of Hollow Glass Spheres

Hollow glass microspheres (HGM) have been employed in a wide range of applications such as thermal insulating coatings for construction and transportation applications and for acoustic insulation coatings. As such, it is expected for the HGM to exhibit an extremely high pressure tolerance in order to endure the harsh environment. In this present study, an effort has been made to investigate the mechanical properties of hollow glass microsphere. The glass sphere with diameters between 5-30 µm, 50-90 µm and 90-125 µm were used for this investigation. This study's objectives are to investigate the strength of HGM and gain an in-depth understanding of the mechanical characteristics of the sintered spheres.

High-Temperature, Lightweight Ceramics with Nano-Sized Ferrites for EMI Shielding: Synthesis, Characterisation, and Potential Applications.

The present study focuses on the synthesis and characterisation of a lightweight ceramic material with electromagnetic interference (EMI) shielding properties, achieved using mullite containing micrometre-sized hollow spheres (cenospheres) and CoFe2O4 nanoparticles. This research explores compositions with varying CoFe2O4 contents ranging from 0 up to 20 wt.%. Conventional sintering in an air atmosphere is carried out at a temperature between 1100 and 1300 °C. The addition of ferrite nanoparticles was found to enhance the process of sintering cenospheres, resulting in improved material density and mechanical properties. Furthermore, this study reveals a direct correlation between the concentration of ferrite nanoparticles and the electromagnetic properties of the material. By increasing the concentration of ferrite nanoparticles, the electromagnetic shielding effect of the material (saturation magnetisation (Ms) and remanent magnetisation (Mr)) was observed to strengthen. These findings provide valuable insights into designing and developing lightweight ceramic materials with enhanced electromagnetic shielding capabilities. The synthesized ceramic material holds promise for various applications that require effective electromagnetic shielding, such as in the electronics, telecommunications, and aerospace industries.

Tandem Carbon Hollow Spheres with Tailored Inner Structure as Sulfur Immobilization for Superior Lithium–Sulfur Batteries

AbstractThe construction of lithium–sulfur battery cathode materials while simultaneously achieving high areal sulfur‐loading, adequate sulfur utilization, efficient polysulfides inhibition, rapid ion diffusion, etc. remains a major challenge. Herein, an internal regulatory strategy to fabricate the unique walnut‐like yolk–shell carbon flower@carbon nanospheres is presented (WSYCS) as sulfur hosts. The internal carbon flower, suitable cavity, and external carbon layer effectively disperse the insulate sulfur, accommodate volumetric expansion, and confine polysulfides, thus improving the performance of lithium–sulfur batteries. The finite element simulation method also deduces the enhanced Li+ diffusion and lithium–sulfur reaction kinetics. More importantly, WSYCS2 is grafted onto carbon fiber (CF) by electro‐spinning method to form a tandem WSYCS2@CF 3D film as a sulfur host for the free‐standing electrode. The corresponding battery exhibits an extremely high areal capacity of 15.5 mAh cm−2 with a sulfur loading of 13.4 mg cm−2. Particularly, the flexible lithium–sulfur pouch cell delivers a high capacity of 8.1 mAh cm−2 and excellent capacity retention of 65% over 800 cycles at a relatively high rate of 1C, corresponding to a calculated energy density of 539 Wh kg−1 and 591 Wh L−1. This work not only provides guidance for tailoring thick carbon/sulfur electrodes but also boosts the development of practical lithium–sulfur batteries.

Dynamics of Electron Transfer in CdS Photocatalysts Decorated with Various Noble Metals.

To address charge recombination in photocatalysis, the prevalent approach involves the use of noble metal cocatalysts. However, the precise factors influencing this performance variability based on cocatalyst selection have remained elusive. In this study, CdS hollow spheres loaded with distinct noble metal nanoparticles (Pt, Au, and Ru) are investigated by femtosecond transient absorption (fs-TA) spectroscopy. A more pronounced internal electric field leads to the creation of a larger Schottky barrier, with the order Pt-CdS > Au-CdS > Ru-CdS. Owing to these varying Schottky barrier heights, the interface electron transfer rate (Ke) and efficiency (ηe) of metal-CdS in acetonitrile (ACN) exhibit the following trend: Ru-CdS > Au-CdS > Pt-CdS. However, the trends of Ke and ηe for metal-CdS in water are different (Ru-CdS > Pt-CdS > Au-CdS) due to the influence of water, leading to the consumption of photogenerated electrons and affecting the metal/CdS interface state. Although Ru-CdS displays the highest Ke and ηe, its overall photocatalytic performance, particularly in H2 production, lags behind that of Pt-CdS due to the electron backflow from Ru to CdS. This work offers a fresh perspective on the origin of performance differences and provides valuable insights for cocatalyst design and construction.

Synergistic Spatial Confining Effect and O Vacancy in WO3 Hollow Sphere for Enhanced N2 Reduction.

Visible-light-driven N2 reduction into NH3 in pure H2O provides an energy-saving alternative to the Haber-Bosch process for ammonia synthesizing. However, the thermodynamic stability of N≡N and low water solubility of N2 remain the key bottlenecks. Here, we propose a solution by developing a WO3-x hollow sphere with oxygen vacancies. Experimental analysis reveals that the hollow sphere structure greatly promotes the enrichment of N2 molecules in the inner cavity and facilitates the chemisorption of N2 onto WO3-x-HS. The outer layer's thin shell facilitates the photogenerated charge transfer and the full exposure of O vacancies as active sites. O vacancies exposed on the surface accelerate the activation of N≡N triple bonds. As such, the optimized catalyst shows a NH3 generation rate of 140.08 μmol g-1 h-1, which is 7.94 times higher than the counterpart WO3-bulk.

Influence of MgO-Al2O3 hollow sphere content on the microstructure and mechanical properties of calcium hexaluminate porous ceramics

ABSTRACT Calcium hexaluminate (CA6) porous ceramics were prepared by foaming and pore-forming agent methods, with Al2O3 and calcium aluminate cement (CAC) as raw materials and magnesium aluminum spinel hollow spheres (MASHSs) as pore-forming agent. The effects of the amount of magnesium aluminum spinel hollow sphere on the phase composition, bulk density, apparent porosity, flexural strength, microstructure, and thermal conductivity of CA6-based porous ceramics were systematically studied. The pores of such porous ceramics are mainly formed by the enhanced amount of MASHSs and the generation of CA6 phase. The results demonstrate that with the elevation of MASHSs content, the microstructure of the samples transforms from a uniform distribution of closed pores to an interconnected micro-pore arrangement. Notably, the fracture paths transition from cohesive to interfacial interactions between MASHSs. This intricate interplay culminates in a remarkable outcome – our ceramics exhibit thermal conductivities ranging from 0.210 to 0.451 W/(m/k), an augmented gas permeability of 25.96 × 10−11m2, and exceptional compressive strengths reaching up to 22.3 MPa. Overall, this study provides insights into the influence of MASHSs content on the microstructure and thermal-mechanical properties of porous materials, which may contribute to the development of advanced ceramic materials with tailored properties.

Living Seed Materials Made by Metal–Organic Framework‐Encapsulated Bacillus Subtilis Spore

AbstractGenetically modified microorganisms (GMMs) possess significant potential for a wide range of applications; however, their execution in real‐world scenarios, particularly in environments characterized by scarce nutrients and unpredictable conditions, proves daunting. Drawing inspiration from the adaptability of natural seeds, living seed materials that combine a core–shell structure ZIF‐8 and genetically engineered spores are introduced. By genetically modifying the Bacillus subtilis strain to express distinct fluorescent proteins, the visualization of spores within the hollow sphere is facilitated, allowing for differentiation between spore and bacteria states. Importantly, the ZIF‐8 shell exhibits responsiveness to diverse nutrient levels, providing enhanced environmental resistance in comparison to bare spores upon exposure to hypochlorous acid, UV‐C radiation, and even vacuum conditions. Moreover, the potential of living seed materials for living sensors of small molecules is showcased by elucidating that spores can be resuscitated into functional bacteria after release from ZIF‐8 material. This research establishes a novel approach for the general fabrication of Metal‐Organic Frameworks (MOF)‐based living spore hybrid materials, offering environmentally controlled release of living materials across a multitude of applications.

Multishell Copper Oxide Hollow Spheres Incorporated with Fatty Amines for High Light-To-Thermal Conversion.

Composite phase change materials (PCMs) are of great importance for the storage and conversion of energy. In this study, a multishell metal oxide hollow microsphere (CuOHS) was prepared by the hydrothermal method, and a new composite PCM (CuOHS@PCMs) for energy storage and conversion purposes was developed by effectively absorbing fatty amines [namely, tetradecylamine (TDA), hexadecylamine (HDA), and octadecylamine (ODA)] PCMs into the CuOHS via the abundant micropores located on the surface of the microsphere. The incorporation of uncontaminated phase alteration substances with CuOHS yields superior light absorption and leak prevention traits. The three CuOHS@PCMs, specifically CuOHS@TDA, CuOHS@HDA, and CuOHS@ODA, possess considerable latent heats of 198.8, 192.6, and 196.0 J·g-1, respectively, and exhibit desirable thermal properties even after completing 50 and 100 thermal cycles. Moreover, under illumination, the photothermal conversion efficiencies of the three variations of CuOHS@PCMs were 84.0, 81.4, and 78.0%. This CuOHS@PCMs, which are based on CuOHS, have considerable potential in the fields of photothermal conversion, solar energy harvesting, and storage.

Core of the Non-Universe in Jaina Cosmology as a Cube of Eight Space-Points

According to Jaina cosmology, the non-universe is a hollow sphere beyond and exists all round the universe, whose middle region is the horizontal universe resting on a circular disc. The Bhagavatī Sūtra and the Sthānāṅga Sūtra each mention that there is the core of the horizontal universe where a cube of eight space-points is and from those eight space-points ten directions originate. This paper presents a conjectural explanation for understanding that cube. The core of the non-universe is the core of a core-sphere when the core-sphere is formed using n core-circles such that they are stacked up and down in the same order from the nth core-circle to the first core-circle. The upper four points of the cube of eight points form the core of the horizontal universe and the cube of eight points is the core of the non-universe. The nth core-circle becomes the horizontal universe when n is innumerable and the nth core-sphere forms the non-universe when n approaches infinity. This paper also shows that the intermediate and cardinal directions are linear and planar respectively while the zenith and nadir ones are three-dimensional.

A spherical version of Feynman’s static field momentum example

The Feynman demonstration that electromagnetic field momentum is real—even for static fields—can be made more pedagogically useful by simplifying its geometry. Instead of Feynman’s disk with charged balls on its surface, this article uses the geometry of a hollow non-conducting sphere with uniform surface charge density. With only methods available in a typical upper-division electrodynamics course, the initial field angular momentum and the final mechanical angular momentum can then be calculated in closed form and shown to be equal.

Insight on MWW siliceous zeolites: From 2D precursors toward 3D structure

ITQ-1 layered zeolites, with MWW framework, were prepared using different synthesis and calcination procedures and fully characterized by means of X-ray diffraction, scanning electron microscopy, N2 sorption and vibrational and nuclear magnetic resonance spectroscopies. Exploring different compositions of the precursor gel, the role of the Organic Structure Directing Agent (OSDA) was definitely disclosed. We proved that the concentration of OSDA in the synthesis gel affects the short-range crystalline order of zeolite crystals. In particular, diluted precursor gels led to the formation of low-density materials in the form of hollow spheres, with partially disordered layers, thinner crystals and high defectivity. In general, all ITQ-1 samples had the same crystalline structure but different morphology, either rose-like or hollow spheres. Moreover, the calcination procedure had an impact on the structural defects of the ITQ-1 zeolite: the higher the removal rate of the OSDA, the higher the defectivity degree of the zeolite.

Microstructural insights of magnetic γ-Fe2O3/geopolymer nanocomposite for prospective green removal of heavy metals from aqueous solutions

The presented work was constructed to study the merging influence between the as-received fly ash (FA) hollow spheres (FA; 632 nm) and either nano-sized FA (18 nm) alone or combined with magnetic (40.81 emu/g) γ-Fe2O3 nanoparticles (20 nm) into the microstructural features of their resulted geopolymeric nanocomposites (nano-FA-GP and nano-MFA-GP, respectively). The neutron activation analysis proofed that the FA has a Si/Al ratio of 3.37 with a hypothesized sialate-multisiloxo structure of both nanocomposites. Batch kinetic systems were implemented to compare the capabilities of both sorbents to decontaminate simulated wastewaters containing some heavy metal (HM) ions. The percentage uptake, distribution coefficient, and decontamination factor were used as performance measures. Incorporation of the magnetic nano-γ-Fe2O3 into the nanocomposite (nano-MFA-GP) enhanced these measures especially at high temperature, with one order of magnitude where Pb2+ > Cu2+ > Cd2+ > Zn2+ >Ni2+. The transient behaviors of all systems were assessed and analyzed non-linearly revealing that all reactions were chemisorption controlled. Additionally, the intra-particle diffusion model was applied and the sorption reaction of Cu2+ and Ni2+ was exclusively onto the external surface layer of the nano-MFA-GP, at high temperature, while the other systems might be controlled by an additional diffusion mechanism into the interior pore structures.

Highly porous YSZ ceramic foams using hollow spheres with holes in their shell for high-performance thermal insulation

Highly porous YSZ ceramic foams using hollow spheres with holes in their shell for high-performance thermal insulation

Highly efficient ethanol sensor based on controllable synthesized ZnO hollow flower spheres

Highly efficient ethanol sensor based on controllable synthesized ZnO hollow flower spheres

Nano hollow carbon regulated by carbon dots as a high-performance anode for potassium and sodium ion battery

In this paper, carbon dots (CDs) derived from citrus peel were used as regulators to adjust the size of template SiO2 and further prepare hollow carbon spheres with different diameter. During the synthesis process of SiO2 templates, the abundant surface functional groups of CDs interact strongly with the functional groups (hydroxyl groups, etc.) possessed by silicic acid and TEOS, thereby inhibiting the growth of SiO2 spheres. By changing the content of CDs added, the size of the SiO2 template changes accordingly. A series of nano-hollow carbon spheres were prepared through high-temperature treatment of as-obtained SiO2 spheres coated with PDA and then acid washing. Among them, HCN-60 with optimized size and hollow structure exhibited excellent potassium/sodium storage performance. This research provides a new idea for the rational design of high-performance carbon anodes.

Loading capacity of welded hollow spherical joints strengthened by cone member

The Welded Hollow Sphere Joint (WHSJ) is frequently employed as a connection form in spatial grid structures. Structures don't retire immediately upon damage, necessitating reinforcement. However, effective solutions for reinforcing WHSJs still have shortcomings in practical engineering applications. Given this research context, a reinforcement scheme for WHSJs is proposed. Feasibility is confirmed through numerical simulation, showing that this reinforcement method is applicable to WHSJs with initial loads, enhancing their mechanical performance without being influenced by the initial loads. The study also initially uncovers the patterns of load-bearing capacity variation with geometric dimensions. Subsequently, an Artificial Neural Network (ANN) is used to predict compressive load-bearing capacity. It utilizes input variables such as sphere diameter (Ds), steel pipe diameter (Dp), reinforcement cone base diameter (Dt), sphere thickness (Ts), steel pipe thickness (Tp), cone thickness (Tt), and cone base angle (θ), with the output being the compressive load-bearing capacity of the welded hollow sphere joint post-reinforcement. Prediction errors are confined to within 10%. Using the Garson algorithm, the sensitivity analysis reveals that steel pipe thickness (Tp) and sphere thickness (Ts) play relatively significant roles in the prediction process.

Overlooked role of void-nanoconfined effect in emerging pollutant degradation: Modulating the electronic structure of active sites to accelerate catalytic oxidation

The efficient removal of emerging pollutant from water is the ultimate frontiers of advanced oxidation processes (AOPs), yet it is challenging to obtain higher catalytic activity and oxidation rate. Herein, a sustainable solution was proposed by optimizing the curvature of confined structure to modulate the electronic state of the active sites in nanochannels for improving the catalytic activity. In addition, the confined effect can enhance the oxidation rate by shorting the mass transfer of active species and pollutants. A void-nanoconfined nanoreactor was prepared by loading Fe2O3 into the nanochannels (<5 nm) of the hollow carbon sphere. An enhancement of 3 orders of magnitude was obtained in the degradation rate constant of void-nanoconfined catalytic system toward sulfamethoxazole (SMX) (6.25 min−1) compared with the non-confined system. The kinetics enhancement was attributed to the larger electron potential difference between the outer and inner nanochannel caused by the curvature increase of carbon sphere, accelerating the electron transfer, so that the energy barrier of SMX degradation reaction was reduced by 31 kcal/mol with the assistance of confinement energy. Importantly, the NC-IN/PDS system exhibited outstanding removal efficiency for the actual river water using a continuous flow reactor. This work provides a new insight into designing an efficient and stable catalytic nanoreactor, enriching the domain of advanced wastewater treatment strategies.

Superoxide dismutase-like cerium dioxide hollow sphere-based highly specific photoelectrochemical biosensing for ascorbic acid

Conventional N-type semiconductor-based photoelectrochemical (PEC) sensors are difficult to achieve high selectivity for ascorbic acid (AA) detection in real samples because co-existing reducing agents act as hole sacrificial agents like AA to promote the increase of photocurrent. Cerium dioxide (CeO2) is a superoxide dismutase-like nanozyme with the reversible Ce3+/Ce4+ redox pair as well as one of alternative N-type semiconductors. To address the problem of PEC detection selectivity of AA, bifunctional CeO2 is a good choice. Herein, a novel and rational PEC biosensor for AA is constructed based on CeO2 hollow spheres as both AA superoxide dismutase-like nanozyme and the photoelectric beacon, which enable the PEC approach with high selectivity. In this protocol, AA can selectively induce a decrease in the CeO2-based photoanode current, which is significantly different from the conventional N-type semiconductor-based PEC sensor, this unique working mechanism is also proposed. The results show that the CeO2-based photocurrent response decreases linearly with AA concentrations in the ranges of 1 μM–600 μM and 600 μM–3000 μM, with a limit of detection of 0.33 μM. Moreover, the fabricated PEC biosensor has advantages of cost-effectiveness, replicability, and stability. Additionally, the sensor is competent for AA determination in practical settings and has achieved satisfactory results.

Engineering Phase to Reinforce Dielectric Polarization in Nickel Sulfide Heterostructure for Electromagnetic Wave Absorption.

Engineering phase transition in micro-nanomaterials to optimize the dielectric properties and further enhance the electromagnetic microwave absorption (EMA) performance is highly desirable. However, the severe synthesis conditions restrict the design of EMA materials featuring controllable phases, which hinders the tunability of effective absorption bandwidth (EAB) and leads to an unclear loss mechanism. Herein, a seed phase decomposition-controlled strategy is proposed to induct nickel sulfide (NiSx) absorbers with controllable phases and hollow sphere nature. Transmission electron microscopy holography and theoretical calculations evidence that the reconstruction of atoms in phase transition induces numerous heterogeneous interfaces and lattice defects/sulfur vacancies to cause varied work functions and local electronic redistribution, which contributes to reinforced dielectric polarization. As a result, the optimized NiS2/NiS heterostructure enables enhanced EM attenuation capability with a wide EAB of 5.04GHz at only 1.6mm, compared to that of NiS2 and NiS. Moreover, the correlation between EAB and NiS phase content is demonstrated as the "volcano" feature. This study on the concept of phase transition of micro-nanomaterials can offer a novel approach to constructing highly efficient absorbers for EMA and other functionalities.

Utilization of Platelet-Rich Plasma (PRP) in the Performance of Blood Cultures

Sepsis is a leading cause of death and morbidity. A precise microbiologic diagnosis in these patients reduces mortality, morbidity, hospital length of stay and costs. Current blood culture technology is woefully inadequate in the detection of circulating bacteria, with detection rates in the range of only 32 to 71%. Platelets play a key role in innate immunity. Platelets interact directly with innate immune cells, exert important immunomodulatory effects, and promote leucocyte migration to sites of infection. During active bacterial infection, platelets release platelet factor -4 which binds onto a variety of bacterial surfaces, thus rendering bacteria more susceptible to opsonization by leucocytes. Platelet surface Toll-like receptors play a key role in regulating bacterial phagocytosis by leucocytes. FcgammaRllA mediates immune complex mediated platelet activation for killing of opsonized bacteria. Platelets also have been observed to “corral” circulating bacteria by forming hollow spheres around them. For these reasons, we performed a prospective pilot study involving 100 patients with suspected sepsis testing the hypothesis that BC performed with PRP is superior to traditional BC performed with whole blood in detecting circulating bacteria. PRP was prepared via centrifugation of blood contained in 3 cc CBC tubes containing EDTA obtained upon admission. PRP and whole blood were injected into separate and identical culture media bottles and cultures were incubated identically in our state-of-the art microbiology laboratory. PRP culture technique detected two patients with circulating bacteria in whom traditional blood cultures were negative: Enterobacter faecalis in an elderly woman with bilateral pneumonia and Burkolderia capecia in an immunocompromised elderly man with pneumonia. In two patients with urosepsis culture results were concordant with identification of E. coli in both techniques. In eight patients, traditional BC technique detected circulating bacteria, wherein PRP-generated cultures were negative: three with Klebsiella pneumoniae, two with Enterococcus faecalis, two with E. Coli, and one with anaerobic Bacteroides Theta-iota group. Three positive cultures generated by traditional methodology were deemed contaminants by I.D. consultation. No contaminants or false positives were detected by the PRP-generated technique. Thus, in this pilot study, evaluating the utility of blood cultures prepared from platelet-rich-plasma, two patients were detected to harbor pathogenic circulating bacteria which was undetected by standard state-of-the-art blood culture techniques. Two distinct disadvantages of BC prepared from PRP relative to traditional BC technique in this study were the time delay in preparing PRP from the patient's CBC tube: these had been stored in the lab for typically 4 to 48 hours before centrifugation and subsequent inoculation, and the dramatic difference in volume represented by PRP vs. traditional BC: typically .5 to 1.1 cc vs. 32 to 40 cc, respectively. An additional disadvantage was the presence of EDTA in CBC tubes, which is confirmed to exert antibacterial properties. The results of this pilot study are intriguing. Further studies comparing PRP-generated BC and traditional BC in the detection of circulating bacteria with emerging identification techniques such as metrogenomic analysis in detecting bacterial DNA, RNA or peptide signatures would be interesting.