Tuned MWCNT/CuO/Fe3O4/Polyaniline nanocomposites with exceptional microwave attenuation and a broad frequency band

Progress in microwave absorbing materials: A critical review

Microwave-absorbing materials play a significant role in various applications that involve the attenuation of electromagnetic radiation. This critical review article provides an overview of the progress made in the development and understanding of microwave-absorbing materials. The interaction between electromagnetic radiation and absorbing materials is explained, with a focus on phenomena such as multiple reflections, scattering, and polarizations. Additionally, types of losses that affect the performance of microwave absorbers are also discussed, including dielectric loss, conduction loss, relaxation loss, magnetic loss, and morphological loss. Each of these losses has different implications for the effectiveness of microwave absorbers. Further, a detailed review is presented on various types of microwave absorbing materials, including carbonaceous materials, conducting polymers, magnetic materials, metals and their composites, 2D materials (such as MXenes and 2D-transition metal dichalcogenides), biomass-derived materials, carbides, sulphides, phosphides, high entropy (HE) materials and metamaterials. The characteristics, advantages, and limitations of each material are examined. Overall, this review article highlights the progress achieved in the field of microwave-absorbing materials. It underlines the importance of optimizing different types of losses to enhance the performance of microwave absorbers. The review also recognizes the potential of emerging materials, such as 2D materials and high entropy materials, in further advancing microwave-absorbing properties.

Synthesis of CuO/polyaniline/multiwalled carbon nanotube composites using Macaranga indica leaves extract as hydrogen gas sensor

In this study, we describe the fabrication of hydrogen gas sensors in the form of nanocomposites containing metal oxides such as copper oxide (CuO), multiwalled carbon nanotubes (MWCNTs), and polyaniline (PANI) using a green synthesis method. We used Macaranga indica (M. indica) leaf extract as a reducing and stabilizing agent to prepare copper oxide nanoparticles (CuONPs). The sample was analyzed using various techniques to determine its physicochemical, morphological, and elemental composition. The XRD data showed that the sample is a CuO/PANI/MWCNT nanocomposite by the best match with the reported data. SEM images revealed a uniform distribution of MWCNTs and spherical CuO nanoparticles of 30-40 nm throughout the CNT network. EDX confirmed that the prepared sample is a pure and inline combination of Cu, O, C, and N. Due to the presence of bioactive elements and PANI, we observed 17% and 25% weight loss for CuO and CuO/PANI/MWCNTs. It was found that this combination of materials can detect H2 gas in concentrations ranging from 110 to 2 ppm at temperatures of 200 and 250 °C. As H2 concentration increased, sensitivity varied from 5% to 20%, but response and recovery times were about 290 and 500 s, respectively, for 40 ppm H2 gas. A logistic function fit to Ra/Rg versus H2 was performed using Y = A2 + (A1 - A2)/(1 + (x/x0)p). The energy bands among the CuO/PANI/MWCNT heterointerfaces were used to demonstrate enhanced H2 gas-sensing properties.

Reduced Graphene Oxide/Barium Ferrite Ceramic Nanocomposite Synergism for High EMI Wave Absorption

The developed nanocomposite exhibits significantly enhanced shielding performance due to the synergistic effect of high dielectric and magnetic loss materials, which modifies the material's impedance and improves its absorption ability. Different weight percentages (0, 1, 5, 10, 15, 20, and 25 wt %) of thermally treated chemically reduced graphene oxide (TCRGO) were combined with two types of magnets, barium hexaferrite (BF) and magnetite (MAG), using a dry powder compaction technique to produce binary ceramic nanocomposite sheets. The shielding performance of a 1 mm thick compressed nanoceramic sheet over the X-band was evaluated using a vector network analyzer. The 25% TCRGO showed high shielding performance for both BF and MAG, while BF had a total shielding efficiency (SET) that exceeded MAG by 130%. The SET of 25 wt % TCRGO/BF was 52 dB, with a 41 dB absorption shielding efficiency (SEA). Additionally, the effect of different levels of incident electromagnetic wave power (0.001-1000 mW) at various thicknesses (1, 2, and 5 mm) was explored. At 1000 mW, the 5 mm TCRGO/BF had an SET of 99 dB, an SEA of 91 dB, and a reflection shielding efficiency (SER) of 8 dB. The use of BF as a hard magnet paired with TCRGO exhibited excellent and stable electromagnetic shielding performance.