Hollow Spherical Materials Research Articles

Heteroatom (N, P)-driven carbon nanomaterials for high-energy storage in supercapacitors

Nanoflower-like hollow carbon sphere (CS) materials with two different heteroatoms doping (N, P) were prepared by a simple synthetic method (NPCS). The specific surface area of NPCS can reach a high value of 396 m2/g. The NPCS has a high degree of hollowness and the self-assembled nanosheet of NPCS forms a fast electron transport channel, and also increases active area in contact with electrolyte. The doping of heteroatoms increases the defect level of the carbon-based nanomaterials and changes the local electron state of the material, thus forming storage sites on the surface of the material, which can be used as a station for ions collecting and distributing. The material was studied as an active material for supercapacitors, and the specific capacitance reached 274.9 F/g. After the 4000th cycle stability test, it still maintained 95.2% of the specific capacitance, indicating that the material has excellent properties of supercapacitor materials.

A comprehensive study on using expanded silica gel size as hollow sphere material in different aluminum alloy-based syntactic foams

PurposeMetal foams are a structural and functional composite materials that have received wide attention due to their specific structures and properties. The aim of this study is to investigate the mechanical properties of syntactic foam by using expanded silica gel with the spacer technique.Design/methodology/approachIn this research paper, the vacuum casting production method was used to produce metal syntactic foams including AlSi12 and AlSi8Cu3 matrix and expanded silica gel fillers with diameters of 2–4.75 mm and 4.75–5.6 mm.FindingsAs a result of the study, it was observed that as the foam densities increased, the compressive strength values of the samples increased due to the increasing volume fraction of the metallic matrix. Samples with the AlSi12 matrix showed higher compressive strength than samples with the AlSi8Cu3 matrix.Originality/valueThe originality of the study is the comparison of two different main matrix alloys (AlSi12 and AlSi8Cu3) and different pores using expanded silica gel.

Enhanced structural and cycling stability of O3-type NaNi1/3Mn1/3Fe1/3O2 cathode by Al replacement of Mn studied in half cell/full sodium-ion batteries

This study uses ball-milling spray drying to prepare a hollow spherical cathode material by doping non-electrochemically active Al into O3-NaNi1/3Mn1/3Fe1/3O2 (NMF) cathode material. The effects of modification on the material's properties were analysed, and the optimum-doped ratio of NaNi1/3Mn(1/3−x)Fe1/3AlxO2 (x = 0.005, NMFA 0.005) was determined. For half-batteries, NMFA 0.005 exhibits a good initial discharge capacity of 115.1 mAh g⁻1 at 1 C and capacity retention of 87.8 % after 200 cycles, which is 16.1 % higher than that of NMF samples. Furthermore, at a high rate (5 C), the initial capacity was 92.3 mAh g−1 and the capacity decline rate was 16.14 %. However, the initial discharge capacity at high voltage was still 136.9 mAh g⁻1. For full batteries, NMFA 0.005 delivered a discharge capacity of 81.1 mAh g⁻1 with a capacity retention of 82.2 % after 100 cycles. Capacity retention was reinforced by approximately 37 % compared with the matrix. Ex situ X-ray diffractometry (XRD), scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS) failure analysis results put together show that an appropriate amount of Al doping could successfully alleviate the Jahn–Teller effect caused by Mn3+, decrease the oxygen loss and increase the stability of the layered structure, all of which result in an excellent electrochemical performance.

Architecture of bimetallic-MOF/silicate derived Co/NC@mSiO2 as peroxymonosulfate activator for highly efficient ciprofloxacin degradation

Bimetallic-ZIF@silicate derived Co/NC@mSiO2 hollow sphere was developed as an excellent peroxymonosulfate (PMS) activator for ciprofloxacin (CFL) antibiotic and parabens degradation. First, bimetallic Zn-Co/ZIF frameworks were prepared by a solvothermal method and then coated with a silica layer. Subsequently, Zn-Co/ZIF@mSiO2 was carbonized under nitrogen gas to obtain the Co, N co-doped porous carbon material. The evaporation of zinc metal in Zn-Co/ZIF@mSiO2 by inert gas flow played an important role in the formation of porous carbon material. In the presence of a small quantity of PMS, this hollow sphere material acts as a highly efficient catalyst for the degradation of CFL with a rate constant of 0.07 min−1. The findings obtained from the quenching radical test and electron paramagnetic resonance (EPR) reveal that Co site within the hollow sphere nanoreactor catalyzed PMS to the generation of the HO, SO4−, and 1O2 for CFL degradation. Notably, the presence of Co NPs in the hollow sphere material enables the facile separation of the catalyst from the reaction mixtures using an external magnet. Furthermore, the as-prepared catalysts exhibited antibacterial activity in Staphylococcus aureus (S. aureus). The current study provides new horizons to develop ZIF-derived hybrid hollow materials in eliminating organic pollutants.

Eco-friendly poly(dopamine)-modified glass microspheres as a novel self-floating adsorbent for enhanced adsorption of tetracycline

Hollow glass microspheres (HGM), as a promising hollow spherical ultra-light material, have the advantages of uniform particle size, regular shape, high mechanical strength and stable physical and chemical properties. It has been widely utilized in many fields but its application in water treatment is yet to be developed. Herein, a novel self-floating composite adsorbent was obtained by forming a poly(dopamine) (PDA) biomass coating on the surface of HGM and introducing sulfonic acid groups. The hollow composite material (HGM@PDA-SO3H) was utilized in the adsorptive elimination of tetracycline (TC) from aqueous solutions. In addition to great adsorption performance, HGM@PDA-SO3H also exhibited satisfactory self-floating solid-liquid separation capability. Langmuir, pseudo second-order and Elovich models correlate isotherms and kinetic data relatively well, respectively. The theoretical saturated TC adsorption amount of HGM@PDA-SO3H evaluated by Langmuir model reached 333.70 mg g−1. Thermodynamic analysis confirmed the spontaneous exothermic property of the adsorption process. There was no serious decline in the adsorption of TC by the material after 5 adsorption cycles, and the adsorbent saturated with contaminants could be easily regenerated via solution desorption, reflecting its satisfactory renewability and stability. Based on the results of batch experiments and characterization analysis, it could be concluded that the corresponding adsorption mechanisms mainly involve electrostatic attraction, hydrogen bonding and π-π stacking interactions. This research aimed to decorate HGM with biomaterials and apply it in the adsorptive purification of TC-contaminated water, which brought some insights and inspiration for the environmental application of HGM, and proved its potential applicability.

A review on performance of cenosphere utilization in concrete

Cenospheres are waste merchandise generated from coal combustions. It is a lightweight particle present in fly ash. Cenospheres are hollow spherical material that mainly consists of silica and alumina in large amounts filled with air or inert gases. They are lightweight and have a low density which offers them greater buoyancy. They are used in the production of Light-Weight Concrete as they offer less density and excellent thermal resistance. This paper presents a review of the performance of Cenosphere utilization in the concrete. The cenospheres blended into cementitious composite altered the mechanical and durability properties. Hence, it's critical to look into cenospheres' characteristics and their properties. Several assessments had been performed using distinct methods. Cenospheres are blended with unique substances in unique compositions and tested for their mechanical and durability properties. Cenospheres can be mixed into cementitious materials, resulting in Light-Weight Concrete.

NiCo2N hollow sphere with interconnected nanosheets shell: A potential anode material for high performance lithium-ion batteries

Transition metal nitrides are of great interest for lithium storage application due to their high electrical conductivity and low voltage plateau. However, the relative cycling stability restricts their practical application. Herein, a stable bimetal nitride NiCo2N hollow sphere material with interconnected nanosheets shell was successfully synthesized via a facial solvothermal route. When used as anodes for lithium-ion batteries, the unique structure can effectively relieve the volume change of the electrode material, and shorten the diffusion distance of lithium ions during the repeated cycling processes. As a result, the NiCo2N electrode exhibits an excellent electrochemical performance. It delivers high discharge capacity of 1244.5 mAh g−1 at a current density of 1 A g−1 after 400 cycles, the capacity can maintain 529.4 mAh g−1 at high current density of 5 A g−1. Furthermore, the electrochemical reaction mechanism of the electrodes is revealed by ex situ XRD, ex situ EIS, and ex situ HRTEM characterization.

Enhanced Electrochemical Kinetics with Highly Dispersed Conductive and Electrocatalytic Mediators for Lithium-Sulfur Batteries.

Lithium-sulfur (Li-S) batteries are promising energy-storage devices because of their high theoretical energy densities. However, the practical application of Li-S batteries is still impeded by the poor cycling performance and rate capability at practical conditions. In order to improve the performance of practical Li-S batteries, a hierarchical Mo2 C nanocluster/carbon nanosheets hybrid based hollow spherical material (Mo2 C/CHS) is designed and prepared. The hollow spheres composed of stacked carbon nanosheets can facilitate the infiltration of electrolyte. The ultrasmall and highly conductive Mo2 C nanocrystals are confined in the carbon nanosheets and expose more active sites for anchoring and conversion of lithium polysulfides and increase the number of the nuclei for Li2 S2 /Li2 S precipitation. Benefitting from the synergistic effects, Mo2 C/CHS greatly promotes electrochemical kinetics in Li-S batteries with high sulfur loading (5 mg cm-2 ). Even under lean electrolyte conditions (E/S = 7 μL mgsulfur -1 ), the Li-S batteries with Mo2 C/CHS added exhibit a discharge capacity of 904 mAh g-1 at the high current rate of 0.5 C, and with 894 mAh g-1 maintained after 200 cycles. This work provides a fundamental understanding of the electrochemical processes and guides the rational design of host and additive materials for practical Li-S batteries.

Solvothermal synthesis of hollow spherical CuCo2O4 as high-performance non-enzymatic glucose sensors

We prepared a hollow spherical CuCo2O4 material by solvothermal and calcination methods to use as an electrode material for non-enzymatic glucose electrochemical detection. Under alkaline conditions, the CuCo2O4/GCE electrode showed a high response to glucose; the highest sensitivity was 2929.4 μA mM−1 cm−2 in a detection range from 2 to 1800 μM, with a detection limit of 0.27 μM (S/N = 3). In addition, CuCo2O4/GCE had good selectivity and good stability in the presence of common interfering substances. Electrochemical test data showed CuCo2O4 is a promising and sensitive material for electrochemical detection of glucose.

Synthesis of Hollow Microspheres LiNi0.5Mn1.5O4 Coated With Al2O3 and Characterization of the Electrochemical Capabilities

AbstractSpinel LiNi0.5Mn1.5O4 (LNMO) has become one of the most practical power lithium-ion battery cathode materials due to its advantages of three-dimensional Li+ diffusion channel, higher potential window (3.5–5V), high-energy density (∼660 Wh/kg), and high-power density. In this manuscript, a hollow spherical LNMO material with large size and high crystallinity is prepared by a modified coprecipitation method using ethyl alcohol as a peptizator. Subsequently, the prepared LNMO material is further modified by an Al2O3 coating to improve its cycle stability. Results show that the initial discharge-specific capacity of LNMO material with 1 wt% Al2O3 coating is 133.7 mAh g−1 at 0.2 C rate, and the capacity retention rate is 97.7% after 100 cycles. The effective increase in the cycle life of the battery can be attributed to the uniform and dense Al2O3 coating on the surface of the material.

Preparation of Al2O3 hollow microsphere via calcining carbon template and its adsorption application

Carbon microsphere was synthesized from glucose via hydrothermal method, and then alumina hollow microsphere was prepared using carbon template. At reaction time of 6 h, the carbon sphere displayed uniform diameter of 800 nm. After removal of carbon core during calcination, it obtained 600 nm of γ-Al2O3 hollow sphere with shell thickness of 80 nm and surface area of 186 m2/g. For adsorption of methylene blue, material exhibited adsorption capacity of 26.5 ± 1.2 mg/g, fitting well with Langmuir isotherm. It is demonstrated that calcining carbon template was an effective and facile approach to obtain hollow sphere material.

Effects of Calcination on Sol-gel Synthesis of Hollow Spherical 8%B-TiO2 for Photocatalytic Degradation of RBR X-3B -Characterization and Activity

Background: TiO2-based materials can be utilized in both polluted air and wastewater treatments. Ion doping is the most applied modification method, and many kinds of metal ions and nonmetal ions are doped into a TiO2 crystalline skeleton. The hollow spherical photocatalyst can both easily suspend in wastewater under aeration and settle down after treatment to release the water. Methods: The hollow spherical B-TiO2 photocatalyst was prepared by a sol-gel method. Tetrabutyl titanate and tributyl borate were used as the titanium and boron sources. The materials were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), infrared spectrum (FTIR), and N2 adsorption-desorption techniques. Results: The 8%B-TiO2 material is composed of anatase TiO2 when the calcination temperature is below 600°C. The graphical template is burnt out during calcination to leave a hole in the spherical 8%B-TiO2. The BET surface area of the materials declines from 53.2 m2/g at 400°C to 10.6 m2/g at 700°C. High-temperature thermal treatment results in the small surface area and large pore size. The activity of the 8%B-TiO2 materials was studied on adsorption and photocatalytic degradation of RBR X-3B dye. The 8%B-TiO2 sample prepared at 600°C has the maximum activity on RBR X-3B degradation. After five cycles, decoloration efficiency on the 8%B-TiO2 decreases from 100% in the first cycle to 80% in the fifth cycle. Conclusion: Photocatalytic activity of the hollow spherical material depends on calcination temperature with the optimum activity on the sample obtained at 600°C. The hollow spherical 8%B-TiO2 has satisfactory performance for recycling. Photocatalytic degradation of RBR X-3B can be proven by the UV-Vis spectra during the degradation process.

Design and synthesis of a calcium modified quaternized chitosan hollow sphere for efficient adsorption of SDBS

In this study, a new pleated hollow sphere material (CS@Ca@CTA) was prepared by mixing chitosan (CS) and calcium chloride (CaCl2) in acetic acid solutions followed by crosslinking with glutaraldehyde (GA), and quaternized using (3-chloro-2 hydroxypropyl) trimethylammonium chloride (CTA). The natural biopolymer chitosan (CS) was used to prepare an environmentally friendly adsorbent material which can efficiently adsorb sodium dodecylbenzene sulfonate (SDBS). The adsorption of SDBS on CS@Ca@CTA can be efficiently improved by CTA at different pH values and Ca can promote the precipitation. The adsorption process of SDBS is as follows. First, SDBS can be adsorbed by electrostatic attraction and Cl- of CTA is used to ion exchange DBS- of SDBS. Then DBS- can bind stably with the Ca2+ in a bidentate form. Furthermore, CS contains NH2 and OH groups, which can provide enormous vacant active sites to adsorb SDBS, and a pleated surface have an ability to capture SDBS. The results indicated that the saturated adsorption capacity of CS@Ca@CTA up to 2300 mg g-1 at pH 3.0 within 240 min. Additionally, adsorption kinetics, isotherm and thermodynamic parameters were discussed. The aim of this article is to present CS@Ca@CTA, which has a great effect on adsorbing the SDBS.

Immobilization of U(VI) on Hierarchical NiSiO@MgAl and NiSiO@NiAl Nanocomposites from Wastewater

The emerging radioactive pollution caused by human activity has attracted increasing attention in the recent years. Uranium (U(VI)) is one of the key radionuclides in the environment, but its migration behavior is firmly controlled by the sorption properties on the environmental matrix. Herein, three hollow spherical materials (NiSiO, NiSiO@MgAl, and NiSiO@NiAl) were rationally designed and constructed by the template method, which showed great potential in the immobilization of U(VI). The engineered functional nanomaterials exhibited fast sorption kinetics, which could be illustrated by the pseudo-second-order model, and favorable thermodynamics, which showed a spontaneous and endothermic process. On the basis of the batch experimental investigations under different conditions, the immobilization of U(VI) on the as-synthesized nanomaterials followed the monolayer mechanism in the form of innersphere surface complexes. The maximum removal capacity (Qmax) of U(VI) on NiSiO@NiAl (136.94 mg g–1) was much hig...

Sol-gel Preparation of Hollow Spherical x%B-TiO2 Photocatalyst: The Effect of Boron Content on RBR X-3B Decoloration

Background: The potential of applying TiO2-based materials has been ascertained in both wastewater and polluted air. Boron is proven to be an effective dopant to promote the activity of TiO2 in our previous work. The density of hollow material is little larger than water so that the hollow photocatalyst can suspend in wastewater under stirring or aeration. Methods: The graphical spheres were prepared from glucose using hydrothermal method. The hollow spherical x%B-TiO2 was synthesized through a sol-gel route, using tetrabutyl titanate and tributyl borate in the precursor. The materials were characterized by X-ray diffraction, scanning electron microscope, infrared spectrum, X-ray photoelectron spectroscopy, and N2 adsorption-desorption techniques. Photocatalytic degradation of RBR X-3B dye was studied to show the activity of the x%B-TiO2 materials. Results: Anatase TiO2 phase forms in all the x%B-TiO2 samples despite the difference in boron content. An absolute Ti4+ oxidation state exists in the x%B-TiO2, which is hardly affected by the doped boron. XPS analysis proves the formation of B-Ti-O structure in anatase TiO2 lattice. BET surface area increases with rising boron doping content in the hollow spherical x%B-TiO2 samples. Photocatalytic activity of TiO2 is enhanced after doping boron. The photocatalytic efficiency on RBR X- 3B degradation reaches the maximum value when n(B)/n(Ti) is 8%. After five photocatalytic cycles, decoloration efficiency on 8%B-TiO2 is as much as 80% of the initial value. Conclusion: A continuous expansion of TiO2 crystal happens with increasing boron content. The Ti4+ oxidation state of titanium in the hollow spherical material is not changed after doping boron. BET surface area of the hollow spherical x%B-TiO2 increases with rising boron doping content. The hollow spherical 8%B-TiO2 has satisfactory performs for recycling and lifetime.

TiO2 hollow spheres as a novel antibiotic carrier for the direct delivery of gentamicin

The TiO2 hollow spheres were synthesized using a green, cheap, and easy process, in which carbonaceous spheres were chosen as the removable template. The prepared materials were characterized by X-ray diffraction (XRD), Field emission scanning electron microscopy (FESEM), Energy-dispersive X-ray spectroscopy (EDX), Atomic force microscopy (AFM), Fourier Transform Infrared Spectroscopy (FTIR), and Brunauer–Emmett–Teller (BET) analysis. According to the results, the obtained mesoporous TiO2 hollow spheres demonstrated an external diameters less than 200 nm with shell thickness around 40 nm. The antibacterial activities of the TiO2 hollow spheres were evaluated against gram-positive (Bacillus subtilis and Staphylococcus aureus) and gram-negative (Escherichia coli and Pseudomonas aeruginosa). No antibacterial activity was found for TiO2 hollow spheres in the used concentrations. TiO2 hollow spheres were loaded with gentamycin as a selected antibiotic to magnify their benefits in biomedical applications. TiO2 hollow spheres exhibited good antibiotic carrier activity for the direct delivery of gentamicin, which was attributed to interaction between gentamicin and surface due to their larger specific surface area, more abundant porous structure, and their spherical morphology. The application of TiO2 hollow spheres as gentamicin carrier undoubtedly opens an avenue to use hollow sphere materials in other drug delivery applications.

Synthesis of Hollow Sphere and 1D Structural Materials by Sol-Gel Process.

The sol-gel method is a simple and facile wet chemical process for fabricating advanced materials with high homogeneity, high purity, and excellent chemical reactivity at a relatively low temperature. By adjusting the processing parameters, the sol-gel technique can be used to prepare hollow sphere and 1D structural materials that exhibit a wide application in the fields of catalyst, drug or gene carriers, photoactive, sensors and Li-ion batteries. This feature article reviewed the development of the preparation of hollow sphere and 1D structural materials using the sol-gel method. The effects of calcination temperature, soaking time, pH value, surfactant, etc., on the preparation of hollow sphere and 1D structural materials were summarized, and their formation mechanisms were generalized. Finally, possible future research directions of the sol-gel technique were outlined.

Metal hollow sphere electrocatalysts

Metal micro-/nano hollow spheres have been widely applied in numerous fields during the last decade. This review will only focus on the synthetic strategies to synthesize hollow spherical structures in the enhancement of their electrocatalytic activity, especially the metal hollow spherical materials. We present a comprehensive overview of synthetic strategies for metal hollow spherical structures which have been approached specifically in electrochemical reactions. These synthetic methods are mainly categorized as hard templates, soft templates, sacrificial templates and without templates. The review further includes electrocatalytic approaches of hollow spherical metals in different electrochemical processes, especially the methanol electro-oxidation reaction for methanol fuel cell application and hydrogen and oxygen evolution reactions in water electrolyzer, as metal hollow spherical materials are especially applied in these specific reactions.

Photocatalytic reduction of Hg using core–shell Fe/CeO2 hollow sphere nanocomposites

A sol–gel method was used to prepare Fe/CeO2 hollow sphere nanocomposites. For comparison, a direct calcination of cerium nitrate was used to prepare CeO2 nanoparticles and Fe/CeO2 nanoparticles. The photocatalytic reduction of Hg was used to study the photocatalytic performance of the prepared nanocomposite photocatalysts using visible-light irradiation. The BET surface areas of the CeO2 nanoparticles and CeO2 hollow spheres were 76 and 160m2/g, respectively. The BET surface area of the hollow sphere CeO2 and CeO2 nanoparticles decreased to 145 and 57m2/g, respectively, by adding iron nanometal. The TEM results revealed that the shapes of the CeO2 nanoparticle and hollow sphere materials are spherical nanoparticles and uniform nanospheres, respectively. The Fe/CeO2 nanoparticles and Fe/CeO2 hollow spheres are spherical nanoparticles and core–shell, respectively. The photocatalytic performance by the Fe/CeO2 hollow spheres was 50, 3.9, and 1.4 times more efficient than that observed from the CeO2 nanoparticles, Fe/CeO2 nanoparticles, and CeO2 hollow spheres, respectively.

Negative Poisson’s ratio in hollow sphere materials

This paper presents a study on the auxetic behaviour of the materials composed of hollow spheres. Although, as a newly developed material, the hollow sphere structures have gained a great deal of scientific attention, few studies have acknowledged its auxetic performance. Auxetic materials or materials with a negative Poisson’s ratio have been a subject of intensive research due to their unusual and, in many extents, superior mechanical properties. A number of different auxetic systems that have been developed commonly based on designing special geometry of the material microstructure. However, in the hollow sphere structures, this mechanism is essentially different and the auxetic effect is attributed to the peculiarities of deformation of a thin-wall hollow sphere and to the interaction between the spheres in the assembly. In this study it is shown that the negative Poisson’s ratio in this material is due to the high ratio between tangential to normal stiffnesses of a thin-wall hollow sphere. To evaluate the mechanical properties of these materials a homogenisation procedure based on the Cosserat 3D continuum theory is adopted. In this procedure, an assembly of the flexible thin-wall spheres is modelled as a stack of rigid spheres connected by a set of linear springs. The developed continuum model is validated against the direct finite element analysis of a regular assembly of the hollow spheres. Influence of the various design parameters on the macroscopic mechanical behaviour of the hollow sphere materials is investigated. The numerical study is focused on the auxetic behaviour of various kinds of packing arrangements of the hollow spheres.