Dopamine-derived cavities/Fe3O4 nanoparticles-encapsulated carbonaceous composites with self-generated three-dimensional network structure as an excellent microwave absorber

Polydopamine-functionalized capsules: From design to applications

In recent years, polydopamine (PDA)-functionalized capsules have garnered significant interest from researchers in the field of materials, owing to its remarkable properties of adhesion, biocompatibility, photothermal conversion capabilities, chemical reactivity, and so on. At present, numerous studies have reported various structures and morphologies of PDA-functionalized capsules fabricated via diverse strategies, that have found applications across a broad spectrum of disciplines. However, there are few comprehensive and systematic reviews focusing on various preparation strategies of PDA-functionalized capsules with various structures. This paper systematically reviewed the preparation strategies and related applications of PDA-functionalized capsules. These strategies of PDA-functionalized capsules were discussed in detail from four parts including PDA-functionalized capsules based on hollow PDA, mesoporous PDA (MPDA), directly encapsulating emulsion, and surface modification of capsules. Then the review outlined the applications of PDA-functionalized capsules in biomedicine, energy, textiles, and the environment. Furthermore, this review summarized the current research findings on PDA-functionalized capsules and outlines their future development directions. Overall, we aim for this review to inspire researchers and offer valuable guidance for the synthesis and application of advanced PDA-functionalized capsules.

Architectural Design of a Multichannel Porous Carbon Fiber for Efficient Electromagnetic Microwave Absorption

An ingenious microstructure of electromagnetic microwave absorption materials is crucial to achieve strong absorption and a broad bandwidth. Herein, one-dimensional (1D) carbon fibers with implantation of zero-dimensional (0D) ZIF-8-derived carbon frameworks and construction of a three-dimensional (3D) microcosmic multichannel porous structure are fabricated by electro-blown spinning, solvent-thermal reaction, and high-temperature pyrolysis techniques. The 1D carbon fiber skeleton with a multichannel structure provides a direct axial conductive pathway for charge transport, which plays an important role in dielectric loss. The 0D surface carbon frameworks offer plenty of heterogeneous interfaces to trigger intensive interfacial polarization loss and act as dihedral angles for microwave scattering. The 3D microcosmic multichannel pores can not only generate multiple reflections as much as possible to dissipate electromagnetic microwave energy but also supply huge interior cavities to improve impedance matching. Thanks to the synergistic effect of a strong electrically conductive pathway for enhancing the conductive loss, a plenteous heterogeneous interface for triggering intensive interfacial polarization loss, microcosmic multichannel pores for generating multiple reflections and improving impedance matching, and N and O atom doping for inducing dipole polarization, the optimal sample with an ingenious microstructure delivers an excellent absorption performance of a minimum reflection loss of -35.5 dB at a thickness of 5.0 mm and an effective absorption bandwidth of 6.72 GHz (10.96-17.68 GHz) at a thickness of 2.0 mm. Such a well-designed multichannel porous carbon fiber may pave the way for the exploitation of high-performance microwave absorbing materials.

Multi-interfaced Ni/C@RGO/PTFE composites for electromagnetic protection applications with high environmental stability and durability

To efficiently address the growing electromagnetic pollution problem, it is urgently required to research high-performance electromagnetic materials that can effectively absorb or shield electromagnetic waves. In addition, the stability and durability of electromagnetic materials in complex practical environments is also an issue that needs to be noticed. Therefore, the starting point for our problem-solving is how to endow magnetic/dielectric multi-interfaced composite materials with excellent electromagnetic protection capability and environmental stability. In this study, magnetic/dielectric multi-interfaced Ni/carbon@reduced graphene oxide/polytetrafluoroethylene (Ni/C@RGO/PTFE) composites were developed to utilize as excellent EWA (electromagnetic wave absorption) and EMI (electromagnetic interference) shielding materials. Due to their diverse heterogeneous interfaces, rich conductive networks, and multiple loss mechanisms, the Ni/C@RGO/PTFE composite exhibits an optimal reflection loss of -61.48 dB and an effective absorption bandwidth of 7.20 GHz, with a filler loading of 5 wt%. Furthermore, Ni/C@RGO/PTFE composite films have an optimal absorption effectiveness value of 9.50 dB and an absorption coefficient of 0.49. Moreover, Ni/C@RGO/PTFE can hold high EWA performance in various corrosive media and maintain more than 90% of EMI shielding effectiveness, which can be attributed to the carbon coating and PTFE matrix acting as dual protective barriers for the susceptible metal Ni, thus obviously improving the stability and durability of composites. Overall, this work presents an effective strategy for the growth of high-performance EWA and EMI shielding materials with outstanding environmental stability and durability, which have wide application prospects in the future.

Facile Recycling of Waste Biomass for Preparation of Hierarchical Porous Carbon with High-Performance Electromagnetic Wave Absorption

Hierarchical-porous-structured materials have been widely used in the field of electromagnetic wave (EMW) absorption, playing a critical role in minimizing EMW interference and pollution. High-quality EMW absorbers, characterized by a lower thickness, lighter weight, wider absorption band, and stronger absorption capacity, have been instrumental in reducing damage and preventing malfunctions in the automotive and aviation industries. The utilization of discarded nut shells through recycling can not only alleviate environmental problems but relieve resource constraints. Herein, a facile method for the preparation of hierarchical porous biomass carbon derived from abandoned Xanthoceras Sorbifolium Bunge Shell (XSS) biomass was developed for high-performance EMW absorption. The porous structures of XSS biochar were studied by using different levels of the K2CO3 activator and simple carbonization. The effect of K2CO3 on the EMW parameters, including the complex permittivity, complex permeability, polarization relaxation, and impedance matching, was analyzed. The best EMW absorption performance of the XSS biochar was observed at a mass ratio of activator-to-biomass of 2:1. A minimum reflection loss (RLmin) of -38.9 dB was achieved at 9.12 GHz, and a maximum effective absorption bandwidth (EABmax) of up to 3.28 GHz (14.72~18.0 GHz) could be obtained at a 1.8 mm thickness. These results demonstrated that hierarchical porous XSS carbon was prepared successfully. Simultaneously, the prepared XSS biochar was confirmed as a potential and powerfully attractive EMW-absorbing material. The proposal also provided a simple strategy for the development of a green, low-cost, and sustainable biochar as a lightweight high-performance absorbing material.

N-S co-doping lignin-based carbon magnetic nanoparticles as high performance supercapacitor and electromagnetic wave absorber

Recently, multifunctional lignin-based materials are gaining more and more attention due to their great potential for low-cost and sustainability. In this work, to obtain both an excellent supercapacitor electrode and an outstanding electromagnetic wave (EMW) absorber, a series of multifunctional nitrogen-sulphur (N-S) co-doped lignin-based carbon magnetic nanoparticles (LCMNPs) had been successfully prepared through Mannich reaction at different carbonization temperature. As compared with the directly carbonized lignin carbon (LC), LCMNPs had more nano-size structure and higher specific surface area. Meanwhile, with the increase of carbonization temperature, the graphitization of the LCMNPs could also be effectively improved. Therefore, LCMNPs-800 displayed the best performance advantages. For the electric double layer capacitor (EDLC), the optimal specific capacitance of LCMNPs-800 reached 154.2 F/g, and the capacitance retention after 5000 cycles was as high as 98.14 %. When the power density was 2204.76 W/kg, the energy density achieved 33.81 Wh/kg. In addition, N-S co-doped LCMNPs also exhibited strong electromagnetic wave absorption (EMWA) ability, whose the minimum reflection loss (RL) value of LCMNPs-800 was realized -46.61 dB at 6.01 GHz with an thickness of 4.0 mm, and the effective absorption bandwidth (EAB) was up to 2.11 GHz ranging from 5.10 to 7.21 GHz, which could cover the C-band. Overall, this green and sustainable approach is a promising strategy for the preparation of high-performance multifunctional lignin-based materials.

Rational construction of yolk-shell structured Co3Fe7/FeO@carbon composite and optimization of its microwave absorption

The construction of yolk-shell composites with dielectric/magnetic multiple loss mechanisms has become a promising strategy to obtain high-efficiency microwave absorbing materials. An ideal microwave absorber should possess dielectric and magnetic loss abilities, thereby leading to the attenuation and absorption of incident electromagnetic radiation. Herein, the yolk-shell structured CoFe₂O₄@carbon (YS-CoFe₂O₄@C) and Co₃Fe₇/FeO@carbon (YS-Co₃Fe₇/FeO@C) composites were designed and synthesized through a series of processes, which include in-situ coating, heat-treating, etching and subsequent carbonization reduction reaction. The composite materials with specific structure, composition, and electromagnetic parameters could be effectively obtained by controlling the reaction conditions. The combination of alloy with high magnetic loss and carbon with advanced dielectric loss as well as the unique yolk-shell structure endow YS-Co₃Fe₇/FeO@C improved impendence matching and large attenuation constant. The YS-Co₃Fe₇/FeO@C composites show optimized microwave absorption behaviors, the minimum reflection loss is up to -57.6 dB at 12.30 GHz with the of 2.5 mm and the corresponding effective absorption bandwidth is 5.27 GHz (10.10-15.37 GHz). Moreover, the widest effective bandwidth could reach 7.0 GHz (11-18 GHz) with the thickness of 2.3 m. This design provides a novel concept for tuning microwave absorption efficiency of magnetic/dielectric composites to prepare high-performance microwave absorbers.

Recent progress in biomass-derived carbonaceous composites for enhanced microwave absorption

Carbonaceous microwave absorbing materials are in vital demand due to the extensive electromagnetic pollution in 5G network era and urgent requirements for stealth technology in national defense domain. Rather than the complicated vapor deposition method, a simple biomass-derived approach sheds light on the mass production of carbon materials for its ubiquitous, environmental-friendly, cost-off, and sustainable advantages. Herein, a concise review of recent advances in designing carbonaceous materials for EM attention is provided with particular stress on the biomass categories and the synthetic method. The three dimensional (3D) interconnected network of carbon materials are highlighted in analysis regarding the biomass selection, functional process, pore-forming strategy and the microwave absorption performance of the corresponding composites. Nature fiber-derived carbon materials, possessing high-aspect ratio fiber structure, are also discussed due to their potential in weaving manufacture and diverse application for flexible cloaking fabric. In the end, the current challenge and the directional perspective for utilizing biomass-derived carbon absorbing materials with effective EM properties are outlined.

Multistage reclamation of Co2+-containing alginate hydrogels as excellent reduction catalyst and subsequent microwave absorber by facile transformation

The multistage reclamation of materials has made contributions to sustainable development, but further progress is still sought after. In this work, functionalized seaweed-based composites were successfully prepared and utilized in multiple stages. Specifically, Co²⁺-containing alginate hydrogels (CHB-Co²⁺) prepared by sol-gel self-assembly and adsorption method using interior/exterior co-functionalized calcium alginate as raw materials were utilized for efficient reduction of p-nitrophenol. After coupling with freeze-drying and carbonization procedures, a high-performance Co/N co-doped carbonaceous microwave absorber was obtained and investigated in detail. By virtue of unique 3D interconnected network, heterogeneous interfaces and doped heteroatom N species, by which endowing the absorber with optimal impedance matching and attenuation ability, as-fabricated NC-Co-700 exhibited prominent microwave absorption performance with -54.2 dB of RL_min at 6.4 GHz and 5.3 GHz of maximum absorption bandwidth (from 12.7 to 18.0 GHz). Additionally, in view of the dielectric loss and magnetic loss caused by the synergy effect among the functional components, the underlying absorption mechanism was proposed. This work provided a novel idea for designing biomass-based functional materials and simultaneously achieved economic benefits through the rational utilization of other products in the preparation process.

Toner Waste Powder (TWP) as a Filler for Polymer Blends (LDPE/HIPS) for Enhanced Electrical Conductivity

Rapid urbanization proportionally increases the waste products which force humankind to find a suitable waste management system. This study aims at identifying the possibility of using toner waste powder (TWP) as a filler for fabricating polymer composites for enhanced electrical conductivity of polymer blends. TWP was successfully incorporated into a polymer blend of low-density polyethylene/high impact polystyrene (LDPE/HIPS) at a high loading percentage of up to 20 wt %. Elemental analysis (SEM-EDS and XRF) showed that the main constituents of TWP are carbon and iron with traces of other metals such as Ca, Cs, Ti, Mn, Si. The electrical conductivity of LDPE/HIPS is significantly enhanced by loading the TWP into the polymer blend. The addition of TWP to LDPE/HIPS blend decreases the electrical resistivity of the LDPE/HIPS/TWP composite to ~2.9 × 107 Ohm.cm at 10 wt % of TWP, which is several orders of magnitude lower than that of the neat blend with maintaining the thermal stability of the polymer composite. The prepared polymer composite is lightweight and shows electrical conductivity, thus it can have potential applications in electronic materials and automotive industries.

Performance enhanced electromagnetic wave absorber from controllable modification of natural plant fiber

Short, surface rough carbon rods, which were derived from natural sisal fiber and went through two different modifications, with excellent electromagnetic wave absorption performance, were studied in this work for the first time. The structure–property relationship was clearly established here. It was shown that these green, cheap and easily obtained carbon rods with mass preparation possibility presented eye-catching absorbing behaviors towards electromagnetic wave. Based on the natural structure of sisal fiber, the minimum reflection loss of KOH activated product reached −51.1 dB and the maximum effective absorbing bandwidth achieved 7.88 GHz. The magnetically modified sample presented −48.6 dB of minimum reflection loss and 4.32 GHz of optimal absorbing bandwidth. Its pioneering application in this field not only opens a new road for this traditional textile sisal fiber but also would possibly make a referable contribution to the design and synthesis of superior carbonaceous electromagnetic wave absorption materials based on bioresource.

Novel carbon rods derived from plant fiber with excellent electromagnetic wave absorption performance have been facilely accomplished via two different modifications.