An article published in the journal Industrial & Engineering Chemistry Research proposes a new method for designing and producing extremely efficient magnetic porous hybrid carbon aerogels for microwave absorption (MA) applications.
Study: Co Nanoparticles Encapsulated in Carbon Nanotubes Decorated Carbon Aerogels Toward Excellent Microwave Absorption. Image Credit: ioat/Shutterstock.com
Microwave Absorption Materials
Substantial efforts have been made over the last few decades to develop cost-effective procedures for synthesizing improved microwave absorption lightweight components with broad absorption and excellent absorbing power.
Carbon aerogels are widely known for their advantageous material properties, for instance, higher specific area of contact, significant porosity and moderate density. In particular, incorporating three-dimensional (3D) carbon aerogels with magnetic metals can boost synergistic effects between the separate components, allowing hybrid carbon aerogels to meet MA criteria.
As a result, they have been widely used in various fields, such as electronic safety, human healthcare equipment, and the defense-stealth business.
The use of nanoparticles with magnetic properties to decorate graphene is considered a promising strategy to attain impedance matching and in obtaining strengthened MA characteristics. Furthermore, nanostructures made of porous aerogels can have a lot of internal free space, which increases the number of microwave reflections through the confined three-dimensional formation of cell walls.
As such, 3-D aerogels are considered an excellent fit for building components for microwave absorption.
Heterogeneous Composition and Diverse Structure
On the contrary, combining heterogeneous materials into lucid carbonaceous structures as absorbers for microwaves provides high polarization and good magnetism, which is especially beneficial for conductivity and microwave exhaustion.
Metal organic frameworks (MOFs), which are structured by combining metal clusters/nodes with organic ligands, are receiving a lot of interest because of their heterogeneous composition and structure.
Complex specimens generated from MOFs have proved to be of use in the areas of microwave absorption due to their anti-corrosion properties, low density, large surface areas, programmable nanostructures and regulated porosity.
More specifically, the transformation of such ligands in the MOF stages can result in the production of on-site structuring of carbon species containing metal nanoparticles (NPs) with magnetic characteristics. Co nanoparticles covered with carbon shells have been explored as microwave absorbers.
To date, achieving MOF derivatives having both a significant level of visualization as well as strong metal NP dispensability for electromagnetic (EM) wave diminishing has been a difficult task.
Synthesizing metal NPs contained in carbon nanotubes (CNTs) generated from pyrolysis of MOFs under reductive environments has been proposed as a viable solution to the problem.
This prevents metal nanoparticles from agglomerating and restacking at higher temperatures. In addition to this, it also changes their electronic formation to increase interfacial polarization and conductivity.
The developed multilayer interface comprises enriched flaws and a high specific area, which are successful techniques to maximize electromagnetic wave loss capacity, thanks to 3D aerogels with 1D CNTs implanted on their exterior.
Porous Hybrid Aerogel
This study discusses the fabrication of a porous hybrid aerogel made of N-doped carbon nanotubes embedded with cobalt on 3D-linked carbon nanosheets.
The blended carbon aerogel possesses a structure with significant pores allowing various dispersing, along with three-dimensional uninterrupted networks that allow for structured electronic conductivity. Such a tailored aerogel demonstrates good MA performance with effective absorption bandwidth at a particularly lower thickness, owing to shared effects between cobalt NPs and N-doped CNTs.
The optimized aerogel's filling ratio is particularly low, and its comparative reflection loss is better than that of different aerogels.
The hybrid carbon aerogel, CNS/Co@ NCNTs, was prepared via intermixing, directional freezing, carbonization, and freeze-drying. This study aimed to demonstrate how to make three-dimensional hybrid carbon aerogels featuring cobalt nanoparticles enclosed in N-doped CNTs synthesized on carbon nanosheets.
Researchers found that the hybrid carbon aerogel exhibits superior MA performance. The study offers new insights into the fabrication of materials suitable for microwave absorption using structural engineering, which is important for enhanced sensors, energy storage, and wearable electronic equipment.
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Fei, Y., Wang, X., Yuan, M., Liang, M., Chen, Y., & Zou, H. (2022). Carbon Aerogels Decorated With Co Nanoparticles Encapsulated in Carbon Nanotubes For Excellent Microwave Absorption. Industrial & Engineering Chemistry Research. Available at: https://pubs.acs.org/doi/10.1021/acs.iecr.1c03585