Three-dimensional Porous Network Research Articles

Controllable preparation of carbon nanofiber membranes for enhanced flexibility and permeability

The electrospinning-produced carbon nanofiber membranes (CNFM) have been applied in many fields for their three-dimensional porous networks, however, the natural fragility impedes their practical applications. Introducing plasticizers into carbon fibers has been proven an efficient way to increase the flexibility of CNFM but the extent is limited. This work explored dual plasticizers strategy to improve the flexibility of CNFM. The addition of zinc acetate and tetraethyl orthosilicate leads to bigger carbon nanofibers and higher mean pore diameters. They can be transformed into SiO2 and ZnO nanoparticles that embed in the carbon fibers, and act as plasticizers to inhibit stress diffusion. The Young's modulus of the optimal SZCNFM-2.0-1.5-700 is 31.0 MPa, which is lower than single plasticizer can reduce. The mechanism of dual plasticizers collaboratively improving the flexibility of SZCNFM was proved based on the characterization results. The SZCNFM-2.0-1.5-700 with well flexibility also revealed high permeability, for instance, the gravity-induced cyclohexane flux is 486.67 L m−2 h−1. Furthermore, the SZCNFM-2.0-1.5-700 requires only half the time compared to the commercial filter membrane when separating the same amount of Pd@CN suspension in the suction filter.

Vanadium sulfide decorated at carbon matrix as anode materials for “fast-charging” lithium-ion batteries

Vanadium sulfide is considered a promising electrode material for achieving rapid lithium storage ascribing to its high specific capacity, unique crystal structure, and abundant valence states. Unfortunately, the structural collapse induced by volume expansion during charging and discharging is the key factor affecting rapid lithium storage. This article prepares composite materials with different morphologies through a strategy of decorating vanadium sulfide at carbon matrix. Among them, graphene oxide modified vanadium tetrasulfide composite materials with three-dimensional conductive networks exhibit excellent electrochemical performance. When the current density is 50 mA g−1, the discharging specific capacity reaches 1, 560 mAh g−1. After 2, 500 cycles at a high current density of 10, 000 mA g−1, the specific capacity is about 188 mAh g−1 with charging time of approximately 70 s. GITT testing indicates that the order of magnitude of the logarithm of the initial diffusion coefficient is 10−11 cm2 s−1 owing to the three-dimensional porous conductive network, which not only shortens ion diffusion path but also provides more active sites for lithium-ion storage, rendering it a promising anode material for “fast-charging” lithium-ion batteries.

Preparation of cellulose derived carbon/reduced graphene oxide composite aerogels for broadband and efficient microwave dissipation

The development of cellulose derived carbon-based composite aerogels with light weight, broad bandwidth and strong absorption remains a challenging task. In this work, the cellulose derived carbon/reduced graphene oxide composite aerogels were prepared by a two-stage process of chemical crosslinking and high-temperature carbonization. The results revealed that the as-fabricated binary composite aerogels had a unique lightweight characteristic and three-dimensional porous network structure, which was chemically crosslinked by epichlorohydrin. Furthermore, the weight concentration of graphene oxide (GO) had a notable influence on the electromagnetic parameters and microwave absorption properties of the composite aerogels. The obtained binary composite aerogel possessed the optimal microwave dissipation capability when the concentration of GO was 1.5 mg/mL. Remarkably, the minimum reflection loss reached −50.42 dB at a thickness of 2.47 mm and a filling ratio of 17.5 wt%. Concurrently, the composite aerogel with a comparable thickness of 2.73 mm showed a wide effective absorption bandwidth of 7.28 GHz, spanning the total Ku-band and extending into a portion of the X-band. The radar cross section contribution of binary composite aerogels in the far-field was also simulated by computer simulation technique. In addition, the potential microwave attenuation mechanism was proposed. It was believed that the results of this paper would offer a reference for the preparation of cellulose derived carbon-based composite aerogels as efficient and broadband microwave absorbers.

Construction of chitosan/alginate aerogels with three-dimensional hierarchical pore network structure via hydrogen bonding dissolution and covalent crosslinking synergistic strategy for thermal management systems

To replace traditional petrochemical-based thermal insulation materials, in this work, the chitosan (CHI)/alginate (ALG) (CA) aerogels with three-dimensional hierarchical pore network structure were constructed by compositing CHI and ALG using a synergistic strategy of hydrogen bonding dissolution and covalent crosslinking. The structure and properties were further regulated by crosslinking the CA aerogels with epichlorohydrin (ECH). The CA aerogels exhibited various forms of covalent crosslinking, hydrogen bonding and electrostatic interactions, with hydrogen bonding content reaching 79.12 %. The CA aerogels showed an excellent three-dimensional hierarchical pore network structure, with an average pore size minimum of 15.92 nm. The structure regulation of CA aerogels obtained excellent compressive properties, with an increase of stress and strain by 137.61 % and 45.05 %, which can support a heavy object 5000 times its weight. Additionally, CA aerogels demonstrate excellent thermal insulation properties and low thermal conductivity, comparable to commercially available insulation materials. More importantly, CA aerogels have good cyclic insulation stability and thermal properties, and they have a flame retardancy rating of V-0, which shows the stability of insulation properties and excellent safety. CA aerogels provide new ideas for the development of biomass thermal insulation materials and are expected to be candidates for thermal management applications.

Enhancing bioactivity and biocompatibility of polyetheretherketone (PEEK) for dental and maxillofacial implants: A novel sequential soaking process

Polyetheretherketone (PEEK) exhibits excellent biocompatibility, fatigue resistance, and an elastic modulus similar to bone, presenting broad application prospects in the field of dental and maxillofacial implants. However, the bioinertness of PEEK limits its applications. In this study, we developed a method to generate biocompatible and bioactive PEEK through a simple sequential soaking process, aimed at inducing bone differentiation and enhancing antibacterial properties. Initially, a three-dimensional (3D) porous network was introduced on the PEEK surface by soaking in concentrated sulfuric acid and water. Subsequently, the sulfonated PEEK surface was treated with oxygen plasma, followed by immersion in a dopamine solution to coat a polydopamine (PDA) layer. Finally, polydopamine phosphate ester-modified 3D porous PEEK was obtained through the reaction of phosphoryl chloride with surface phenolic hydroxyl groups. Systematic studies were conducted using scanning electron microscopy, X-ray photoelectron spectroscopy, water contact angle analysis, cell proliferation and adhesion, osteogenic gene expression detection, alkaline phosphatase staining, alizarin red staining, and bacterial culture. Overall, compared to unmodified PEEK, the modified PEEK significantly enhanced in vitro cell proliferation and adhesion, osteogenic differentiation, and antibacterial properties. The simple surface modification measures combined in this study may represent a promising technology and could facilitate the application of PEEK in dental and maxillofacial implants.

Analysis and Characterization of Micro–Nano Pores in Coal Reservoirs of Different Coal Ranks

Coalbed methane represents a promising source of clean and efficient unconventional energy. The intricate network of micro–nano pores within coal serves as the primary adsorption space for gas, contributing to the complexity of gas migration channels. In this study, based on the box-counting method, three coal samples representing low, medium, and high ranks were subjected to high-precision micro-CT scanning and nano-CT scanning to generate three-dimensional (3D) pore network models using Avizo visualization software. This facilitated the accurate and quantitative characterization of the micro–nano pore structures within coal reservoirs. The results indicated that the face rate distribution range of each sample was large, indicating relatively strong heterogeneity in each sample. The volume fractal dimension of each sample, determined through micro–nano-CT scanning, was around 2.5, while the surface fractal dimension exhibited oscillatory characteristics with moderate uniformity. The pore equivalent radius and throat equivalent radius distributions were unimodal across all the samples, with the micro-CT scanning revealing a concentration primarily within the range of 100–400 μm for the pore equivalent radius and within 200 μm for the throat equivalent radius. Conversely, the nano-CT scanning exhibited concentrations primarily within the range of 500–2500 nm for the pore equivalent radius and within 2000 nm for the throat equivalent radius. The analysis of the 3D reconstruction structures indicated that the middle-rank coal exhibited more developed large–medium pores compared with the low-rank and high-rank coal, while the low-rank and high-rank coal exhibited relatively more micro–small pores. Furthermore, the low-rank coal exhibited the fewest number of pores but the largest average pore equivalent radius and throat radius. Additionally, the middle–high-rank coal exhibited a relatively larger number of pores. Despite the complex topological structures observed in each sample, a significant proportion indicated a coordination number of 0–20, indicating excellent connectivity within the coal samples. This study is conducive to the optimization of coalbed methane surface development blocks and the formulation of reasonable development plans.

Investigation on the Tea Polyphenol/Swelling Gels to Inhibit Coal Spontaneous Combustion: An Experimental Study

ABSTRACT Developing new fire-fighting material is most significant for effective prevention and control of coal spontaneous combustion. To enhance the flame-retardant performance of the gel, the tea polyphenol/swelling gels are developed using a water-soluble polymerization method. Thermogravimetric analysis, programmed temperature experiments, and Fourier-transform infrared spectroscopy are used to reveal the structural characteristics, microscopic morphology, and thermal stability of the gel. Experimental testing the tea polyphenol/swelling gels’ water absorption, water retention, and reusability as well as their inhibitory effect on coal spontaneous combustion. The results showed that the prepared tea polyphenol/swelling gels exhibited a porous three-dimensional network structure, with a maximum swelling ratio of 607.2 g/g and a salt absorption rate of 121.4 g/g. After the testing coal sample is treating by the tea polyphenol/swelling gels, its CO production rate is sharply decreased, but the corresponding ignition point temperature and flame-retardant rate are significantly increased. The activation energy in the first stage is increased by 32.2 kJ·mol−1, in the second stage by 4.0 kJ·mol−1, and in the third stage by 23.2 kJ·mol−1. Additionally, the active functional groups such as hydroxyl and methyl in the coal are also reduced by the treatment of tea polyphenol/swelling gels. Correlation analysis indicate that the inhibition effect of coal spontaneous combustion can be achieved by reducing -OH, CH3/CH2 groups, while the increasing of C = C, C- O, C- H functional groups in the coal. Moreover, the tea polyphenol/swelling gels performing the characteristics of excellent water absorption, inhibiting coal spontaneous combustion by absorbing heat, covering the coal microstructure, and inhibiting the oxidative activity of coal molecules. This study can provide theoretical guidance for the application of swelling gels in inhibiting coal spontaneous combustion.

Immunometabolic checkpoint-mediated macrophage metabolic reprogramming accelerates infected wound healing

Immunometabolic disorders, triggered by excessive oxidative stress, lead to macrophage dysfunction, consequently impeding the healing of infected wounds. The uncontrolled accumulation of reactive oxygen species (ROS) in infected wounds is primarily attributed to persistent bacterial infections, excess exudate, and hypoxia. Herein, an immunometabolic checkpoint-mediated macrophage metabolic reprogramming strategy based on a nanofiber aerogel loaded with catalase (CAT) and tannic acid (TA) is proposed. The three-dimensional porous network of the nanofiber aerogel effectively absorbs exudates, maintains wound dryness, and prevents tissue saturation. CAT catalyzes oxygen generation, alleviates hypoxia, and reduces ROS, while TA acts as a natural antioxidant and antibacterial agent, collaboratively mitigating oxidative stress and bacterial infections. More importantly, the CAT-TA nanofiber aerogel, as an immunometabolic checkpoint regulator, can reshape the glutathione (GSH) metabolic pathway, enhancing intrinsic antioxidative capacity, allowing the reversion of macrophage functions, and ultimately promoting wound healing. This macrophage metabolism therapy (MMT), centered on the modulation of immunometabolic checkpoint, effectively enhances the regenerative capacity of infected wounds and provides a pioneering perspective for the treatment of regeneration disorders in infected tissues.

Facile synthesis of an acrylic acid-co-2-acrylamide-2-methylpropanesulfonic acid copolymer / polyvinylpyrrolidone semi-IPN hydrogel with excellent swelling and anti-leakage properties

Water scarcity becomes an increasingly serious problem for humankind due to climate change and population growth, especially the water leakage in arid and semi-arid areas. Hydrogel polymers show increasingly important roles on water resources utilization. A novel hydrogel copolymer, acrylic acid-co-2-acrylamide-2-methylpropanesulfonic acid copolymer / polyvinylpyrrolidone (P(AA-co-AMPS)/PVP) semi-interpenetrating network (semi-IPN) hydrogel, was designed and successfully synthesized via a facile one-pot free radical copolymerization method. The main parameters during the synthesis process were optimized, including relative contents of polymer monomers, cross-linking agent, initiator and neutralization agent. Physical characterizations demonstrate that, P(AA-co-AMPS)/PVP hydrogel shows porous three-dimensional network structure, including a crosslinked network structure in P(AA-co-AMPS) copolymers and their intermolecular hydrogen bonding interactions with linear PVP. The as-synthesized P(AA-co-AMPS)/PVP hydrogel not only can deliver superior water absorbing capability (up to 1689.95 g g−1) and good reswelling performance, but also shows excellent water anti-leakage performance when being composed with red clay, demonstrating its multi-role applications in future sustainable agriculture.

Scleroglucan-Based Foam Incorporating Recycled Rigid Polyurethane Waste for Novel Insulation Material Production.

This study details the synthesis and performance evaluation of a novel lightweight thermal and acoustic insulation material, resulting from the combination of a scleroglucan-based hydrogel and recycled rigid polyurethane waste powder. Through a sublimation-driven water-removal process, a porous three-dimensional network structure is formed, showcasing notable thermal and acoustic insulation properties. Experimental data are presented to highlight the material's performance, including comparisons with commercially available mineral wool and polymeric foams. This material versatility is demonstrated through tunable mechanical, thermal and acoustic characteristics, achieved by strategically adjusting the concentration of the biopolymer and additives. This adaptability positions the material as a promising candidate for different insulation applications. Addressing environmental concerns related to rigid polyurethane waste disposal, the study contributes to the circular economy.

Separation of ovomucin from duck egg white and its “acid-tight /alkali-loose” self-supporting gel properties under different pH

Ovomucin is a key component in maintaining the viscous nature of egg white and has vast potential in the utilization of food industry. The objectives of the study were to determine the effect of different pH on the extractability and gel properties of ovomucin. After removing lysozyme through ion exchange, the diluted duck egg white was acidified to a narrow pH range (4.50, 4.75, 5.00, 5.25, 5.50, 5.75 and 6.00) to precipitate ovomucin. By comprehensive study of purity, yield, and convenience of large-scale preparation, 4.75 was chosen as the optimal pH to extract ovomucin with the highest purity of 85.17 ± 2.31% and a compromised yield of 4.60 ± 0.06 mg/g duck egg white. A series of self-supporting gels were prepared with freeze-dried ovomucin powder at room temperature upon rehydration and centrifugation, and the gels properties were highly associated with pH. Gel formed around pH 5 was the aggregate of natural globular proteins with lowest hydrophobicity and electrostatic interaction, relatively dense structure and high water-holding capacity (WHC). Stronger acidic conditions disrupted the disulfide bonds and formed a rougher spherical aggregate. Under alkaline conditions, however, the protein gradually unfolded and broke into linear basic polypeptides, thus a porous three-dimensional network was formed. Overall, this study provided insights into the formation mechanism of the “acid-tight/alkali-loose” ovomucin gels, and introduced a potential candidate for the development of bioactive substance delivery materials.

A three-dimensional BaFe11.6(ZrSm)0.2O19/rGO composite aerogel with superior microwave absorption properties

The combination of dielectric and magnetic materials can significantly improve microwave absorption properties. In this work, we introduce a novel Zr–Sm doped barium ferrite BaFe11.6(ZrSm)0.2O19, which is compounded with rGO aerogel and presents superior microwave absorption properties. The results show that the BaFe11.6(ZrSm)0.2O19/rGO composite aerogel exhibits a unique three-dimensional porous network structure which enhances the reflection and scattering of electromagnetic waves. Meanwhile, the addition of BaFe11.6(ZrSm)0.2O19 abounds the folds and defects on the surface of rGO sheet layer, generating a large amount of polarisation and relaxation. In addition, with the increase of BaFe11.6(ZrSm)0.2O19 content, the permeability gradually increases, while the dielectric constant gradually decreases. At a certain content, both of them can be well balanced to obtain high attenuation constants and great impedance matching, which regulates the wave-absorbing properties of the material. The minimum reflection loss (RLmin) of BaFe11.6(ZrSm)0.2O19/rGO composite aerogel can reach −53.17 dB at a matching thickness of 2.9 mm, and the absorption bandwidth reaches 7.04 GHz, which has been improved by 40% than pure BaFe11.6(ZrSm)0.2O19. Therefore, it is expected to be a candidate for lightweight, thin, high loss, large bandwidth microwave absorbing materials.

Synthesis and Electrochemical Characterization of Nitrate-Doped Polypyrrole/Ag Nanowire Nanorods as Supercapacitors.

Polypyrrole (PPy)-capped silver nanowire (Ag NW) nanomaterials (core-shell rod-shaped Ag NW@PPy) were synthesized using a one-port suspension polymerization technique. The thickness of the PPy layer on the 50 nm thickness/15 μm length Ag NW was effectively controlled to 10, 40, 50, and 60 nm. Thin films cast from one-dimensional conductive Ag NW@PPy formed a three-dimensional (3D) conductive porous network structure and provided excellent electrochemical performance. The 3D Ag NW@PPy network can significantly reduce the internal resistance of the electrode and maintain structural stability. As a result, a high specific capacitance of 625 F/g at a scan rate of 1 mV/s was obtained from the 3D porous Ag NW@PPy composite film. The cycling performance over a long period exceeding 10,000 cycles was also evaluated. We expect that our core-shell-structured Ag NW@PPy composites and their 3D porous structure network films can be applied as electrochemical materials for the design and manufacturing of supercapacitors and other energy storage devices.

Advanced three-dimensional hierarchical porous α-MnO2 nanowires network toward enhanced supercapacitive performance

Hierarchical α-MnO2 nanowires with oxygen vacancies grown on carbon fiber have been synthesized by a simple hydrothermal method with the assistance of Ti4+ ions. Ti4+ ions play an important role in controlling the morphology and crystalline structure of MnO2. The morphology and structure of the as-synthesized MnO2 could be tuned from δ-MnO2 nanosheets to hierarchical α-MnO2 nanowires with the help of Ti4+ ions. Based on its fascinating properties, such as many oxygen vacancies, high specific surface area and the interconnected porous structure, the α-MnO2 electrode delivers a high specific capacitance of 472 F g−1 at a current density of 1 A g−1 and the rate capability of 57.6% (from 1 to 16 A g−1). The assembled symmetric supercapacitor based on α-MnO2 electrode exhibits remarkable performance with a high energy density of 44.5 Wh kg−1 at a power density of 2.0 kW kg−1 and good cyclic stability (92.6% after 10 000 cycles). This work will provide a reference for exploring and designing high-performance MnO2 materials.

Turning Polysaccharides into Injectable and Rapid Self-Healing Antibacterial Hydrogels for Antibacterial Treatment and Bacterial-Infected Wound Healing.

Great efforts have been devoted to the development of novel and multifunctional wound dressing materials to meet the different needs of wound healing. Herein, we covalently grafted quaternary ammonium groups (QAGs) containing 12-carbon straight-chain alkanes to the dextran polymer skeleton. We then oxidized the resulting product into oxidized quaternized dextran (OQD). The obtained OQD polymer is rich in antibacterial QAGs and aldehyde groups. It can react with glycol chitosan (GC) via the Schiff-base reaction to form a multifunctional GC@OQD hydrogel with good self-healing behavior, hemostasis, injectability, inherent superior antibacterial activity, biocompatibility, and excellent promotion of healing of methicillin-resistant Staphylococcus aureus (MRSA)-infected wounds. The biosafe and nontoxic GC@OQD hydrogel with a three-dimensional porous network structure possesses an excellent swelling rate and water retention capacity. It can be used for hemostasis and treating irregular wounds. The designed GC@OQD hydrogel with inherent antibacterial activity possesses good antibacterial efficacy on both S. aureus (Gram-positive bacteria) and Escherichia coli (Gram-negative bacteria), as well as MRSA bacteria, with antibacterial activity greater than 99%. It can be used for the treatment of wounds infected by MRSA and significantly promotes the healing of wounds. Thus, the multifunctional antibacterial GC@OQD hydrogel has the potential to be applied in clinical practice as a wound dressing.

Advancements in Noble Metal-Decorated Porous Carbon Nanoarchitectures: Key Catalysts for Direct Liquid Fuel Cells.

Noble-metal nanocrystals have emerged as essential electrode materials for catalytic oxidation of organic small molecule fuels in direct liquid fuel cells (DLFCs). However, for large-scale commercialization of DLFCs, adopting cost-effective techniques and optimizing their structures using advanced matrices are crucial. Notably, noble metal-decorated porous carbon nanoarchitectures exhibit exceptional electrocatalytic performances owing to their three-dimensional cross-linked porous networks, large accessible surface areas, homogeneous dispersion (of noble metals), reliable structural stability, and outstanding electrical conductivity. Consequently, they can be utilized to develop next-generation anode catalysts for DLFCs. Considering the recent expeditious advancements in this field, this comprehensive review provides an overview of the current progress in noble metal-decorated porous carbon nanoarchitectures. This paper meticulously outlines the associated synthetic strategies, precise microstructure regulation techniques, and their application in electrooxidation of small organic molecules. Furthermore, the review highlights the research challenges and future opportunities in this prospective research field, offering valuable insights for both researchers and industry experts.

Study on pore-crack evolution and connectivity of coal subjected to controlled electrical pulse based on CT scanning technology

Controlled electric pulse (CEP) technology is a novel method for enhancing coal seam permeability. To study the pore-crack evolution and connectivity of the coal body by CEP, a self-built CEP cracking and enhancing permeability of coal rock test system was used to test five groups of coal samples under different breakdown voltages (BVs). We established a three-dimensional crack structure and equivalent pore network model for before and after penetration using high-precision micro-CT technology to quantitatively study the evolution and connectivity of the pore and crack structures of the coal body. The results showed that with rising BV, coal body crushing intensifies, leading to an increased cracking ratio and fractal dimension. This summarised the three stages of coal sample crushing by CEP. In addition, the proportion of larger equivalent pores and throat radii in the breakdown coal body was significantly increased compared to that of raw coal, and the connectivity structure was improved to different degrees compared to that of raw coal. Eventually, a three-dimensional crack network structure formed inside the coal samples, which was broken at both ends and complex in the middle, providing a transport channel for coalbed methane mining.

A cellulose derived nanofibrous nitrogen-doped carbon/TiO2/SnO2/carbon composite anodic material for lithium storage

SnO2 with high theoretical specific capacity is regarded as a desirable anodic material for lithium storage. However, the serious volume variation during discharge/charge cycling and poor conductivity significantly constrain the electrochemical performance. Herein, nanofibrous nitrogen-doped carbon (NC)/TiO2/SnO2/carbon composite was fabricated through layer-by-layer assembly of SnO2 and TiO2-gel layers alternately using cellulosic filter paper as the structural scaffold, followed by deposition of polypyrrole on the surface by chemical polymerization method, and subsequent calcination of the as-obtained matter in inert atmosphere. The achieved composite possesses a typical three-dimensional fibrous porous network structure inherited from the cellulosic substrate, and complete NC nanolayer coating on each nanofiber by adjusting the amount of pyrrole, which can alleviate the volume change and increase the conductivity of SnO2. Furthermore, the interlaced TiO2 multilayer can enhance the cycling stability during cycling, as well as facilitate the lithium-ion transfer through abundant interface. The optimal NC/TiO2/SnO2/carbon composite delivers an initial discharge capacity of 1492.6 mAh g−1 at a current density of 100 mA g−1, and retains a reversible capacity of 680.8 mAh g−1 after 200 discharge/charge cycles. This work provides an efficient strategy for design and construction of metal-oxides/carbon composite anodic materials with hierarchical microstructure that hold great potential in lithium storage.

The Formation Process and Mechanism of the 3D Porous Network on the Sulfonated PEEK Surface.

A three-dimensional (3D) porous network can be prepared on the PEEK surface by sulfonation with enhanced osseointegration and antibacterial properties. However, few studies have been conducted on the formation mechanism of a 3D porous network. In this work, the surface and cross-sectional morphologies, chemical compositions, functional groups, surface wettability, and crystalline states of sulfonated PEEK were investigated at different sulfonation times and coagulant concentrations. The results show that the number of nodular structures and broken fibers on the sulfonated PEEK surface as well as the size of macrovoids in the cross sections increase with increasing sulfonation times when water is used as a coagulant. In contrast, dilute sulfuric acid as a coagulant can inhibit the formation of surface porous structures and macrovoids in the cross sections. Moreover, all of the sulfonated PEEK samples have the same chemical compositions but exhibit better hydrophilicity as the number of microsized pores decreases. It is proposed that non-solvent-induced phase separation (NIPS) occurs during the sulfonation process, and the formation mechanism of surface and cross-sectional morphologies is discussed. Furthermore, it is assumed that the air is trapped in the microsized pores, leaving the surface of the 3D porous network in the Cassie-wetting state. All of these preliminary results throw light on the nature of the sulfonation process and may guide further modification of the structures of sulfonated PEEK.

Construction of three-dimensional porous network Fe-rGO aerogels with monocrystal magnetic Fe3O4@C core-shell structure nanospheres for enhanced microwave absorption

Single dielectric loss material has defects such as strong dielectric properties and impedance mismatch. Hence, developing electromagnetic wave (EMW) absorption materials with both outstanding EMW absorption and favourable impedance matching performances is still a great challenge. A large number of literature have reported that combining dielectric materials with magnetic materials to enhance microwave absorption. However, there is little literature on the effect of crystal structure on the absorbing properties of materials. Owing to the virtues of light weight, low density and thin thickness of aerogel, which has been widely utilized in EMW absorption materials. Herein, Fe-based metal organic framework-reduced graphene oxide (Fe-rGO) aerogel was synthesized via simple hydrothermal method and freeze-drying. Besides, Polyvinyl Pyrrolidone (PVP) was used as a surfactant to endow Fe3O4 nanospheres with uniform size and smooth morphology. Moreover, Fe3O4 nanospheres with different crystal phase (monocrystal and polycrystal) structure were obtained under different carbonization temperatures (600 and 800 °C). Through comparison, the monocrystal Fe3O4 nanospheres show better microwave absorption and impedance matching performance than that of polycrystal Fe3O4 nanospheres. In addition, the electromagnetic parameters can be adjusted by regulating the mass ratio of Fe-based metal organic framework (Fe-MOF) to GO. As a consequence, the prepared 600Fe-rGO 2:1 aerogel achieves the minimum reflection loss (RLmin) of −64.89 dB and a broad effective absorption bandwidth (EAB) of 6.96 GHz with a low filling content of 5 wt%, showing excellent EMW absorption and impedance matching property. In short, the structural design of single crystal magnetic Fe3O4 nanospheres provides inspiration and guidance for future research of enhanced microwave absorption materials.