scholarly journals Tuning Dielectric Loss of SiO2@CNTs for Electromagnetic Wave Absorption

Nanomaterials ◽  
2021 ◽  
Vol 11 (10) ◽  
pp. 2636
Author(s):  
Fenghui Cao ◽  
Jia Xu ◽  
Xinci Zhang ◽  
Bei Li ◽  
Xiao Zhang ◽  
...  
Keyword(s):  
Electromagnetic Wave ◽  
High Performance ◽  
Low Cost ◽  
Impedance Matching ◽  
3D Structure ◽  
Carbon Matrix ◽  
Current Approach ◽  
Matrix Composites ◽  
Simple Method ◽  
Absorption Performance

We developed a simple method to fabricate SiO2-sphere-supported N-doped CNTs (NCNTs) for electromagnetic wave (EMW) absorption. EMW absorption was tuned by adsorption of the organic agent on the precursor of the catalysts. The experimental results show that the conductivity loss and polarization loss of the sample are improved. Meanwhile, the impedance matching characteristics can also be adjusted. When the matching thickness was only 1.5 mm, the optimal 3D structure shows excellent EMW absorption performance, which is better than most magnetic carbon matrix composites. Our current approach opens up an effective way to develop low-cost, high-performance EMW absorbers.

Morphology-dependent electromagnetic wave absorbing properties of iron-based absorbers: one-dimensional, two-dimensional, and three-dimensional classification

2019 ◽  
Vol 87 (2) ◽  
pp. 20901 ◽  
Author(s):  
Zehao Zhao ◽  
Zirui Jia ◽  
Hongjing Wu ◽  
Zhenguo Gao ◽  
Yi Zhang ◽  
...  
Keyword(s):  
Electromagnetic Wave ◽  
Electromagnetic Interference ◽  
High Performance ◽  
Low Cost ◽  
Impedance Matching ◽  
Three Dimensional ◽  
Microwave Absorbing Materials ◽  
Dimensional Classification ◽  
Absorbing Materials ◽  
Microwave Absorbing

Owing to the fast development of wireless techniques at the high-frequency range, the electromagnetic interference problem has been of increasing significance and attracting global attention. It is urgent to develop efficient microwave absorbing materials to attenuate the harmful electromagnetic wave. Iron and Fe-based composites are advantageous in the low-cost and attractive magnetic properties, so they have been widely studied in microwave absorption. This review focuses on the latest advances in nanostructured Fe-based materials including nanostructured iron, Fe/C (carbon nanotubes, nanofibers, nanocapsules, etc.), Fe/semiconductor (TiO2, MnO2, ZnO, SiO2, MoS2, etc.), Fe/polymer (polyaniline and polypyrrole), FeCo alloy, etc. However, most of these Fe-based materials suffer from the poor impedance matching and oxidation, which seriously impede their implementation as high-performance microwave absorbing materials. In this review, the main synthesis and modification methods, as well as the practical performance of Fe-based microwave absorbing materials are discussed. Moreover, challenges and perspectives of Fe-based composites for further development in microwave absorbing materials are proposed.

scholarly journals Microstructural Design of Necklace-Like Fe3O4/Multiwall Carbon Nanotube (MWCNT) Composites with Enhanced Microwave Absorption Performance

Materials ◽  
2021 ◽  
Vol 14 (17) ◽  
pp. 4783
Author(s):  
Mu Zhang ◽  
Sinan Song ◽  
Yamin Liu ◽  
Zaoxia Hou ◽  
Wenyi Tang ◽  
...  
Keyword(s):  
Dielectric Constant ◽  
Microwave Absorption ◽  
Impedance Matching ◽  
Interfacial Polarization ◽  
Carbon Matrix ◽  
Thermal Method ◽  
Multiwall Carbon Nanotube ◽  
Matrix Composites ◽  
Experimental Parameters ◽  
Absorption Performance

In order to manufacture microwave absorbers with strong attenuation abilities and that are light weight, in this paper, ferromagnetic carbon matrix composites were prepared by the composite of carbon nanotubes with adjustable dielectric constant and Fe3O4. Fe3O4/MWCNT composites with well-designed necklace-like structure and controllable size in the range of 100–400 nm have been successfully achieved by a simple solvent thermal method. A series of samples were prepared by changing experimental parameters. The microwave absorption characteristics of these samples were studied from the dielectric constant and magnetic permeability in two aspects. The electromagnetic absorption properties of the composites show obvious differences with different microsphere sizes, different microsphere density and different proportion of additives. When the solvothermal time is 15 h and the microsphere size is 400 nm, the reflection loss reaches −38 dB. The interfacial polarization caused by the unique structural design and good impedance matching produce composites that possess excellent electromagnetic loss ability.

RF-MEMS Components and Networks for High-Performance Reconfigurable Telecommunication and Wireless Systems

2012 ◽  
Vol 81 ◽  
pp. 65-74 ◽  
Author(s):  
Jacopo Iannacci ◽  
Giuseppe Resta ◽  
Paola Farinelli ◽  
Roberto Sorrentino
Keyword(s):  
High Performance ◽  
Microelectromechanical Systems ◽  
Rf Mems ◽  
Low Cost ◽  
Impedance Matching ◽  
Phase Shifters ◽  
Rf Systems ◽  
Mems Technology ◽  
And Performance ◽  
Rf Performance

MEMS (MicroElectroMechanical-Systems) technology applied to the field of Radio Frequency systems (i.e. RF-MEMS) has emerged in the last 10-15 years as a valuable and viable solution to manufacture low-cost and very high-performance passive components, like variable capacitors, inductors and micro-relays, as well as complex networks, like tunable filters, reconfigurable impedance matching networks and phase shifters, and so on. The availability of such components and their integration within RF systems (e.g. radio transceivers, radars, satellites, etc.) enables boosting the characteristics and performance of telecommunication systems, addressing for instance a significant increase of their reconfigurability. The benefits resulting from the employment of RF-MEMS technology are paramount, being some of them the reduction of hardware redundancy and power consumption, along with the operability of the same RF system according to multiple standards. After framing more in detail the whole context of RF MEMS technology, this paper will provide a brief introduction on a typical RF-MEMS technology platform. Subsequently, some relevant examples of lumped RF MEMS passive elements and complex reconfigurable networks will be reported along with their measured RF performance and characteristics.

Dual-band metamaterial absorber with stable absorption performance based on fractal structure

2021 ◽  
Author(s):  
Shuguang Fang ◽  
Lianwen Deng ◽  
Pin Zhang ◽  
Lei-Lei Qiu ◽  
Haipeng Xie ◽  
...  
Keyword(s):  
Fractal Structure ◽  
Low Cost ◽  
Impedance Matching ◽  
Metamaterial Absorber ◽  
Dual Band ◽  
Fractal Structures ◽  
Absorption Bands ◽  
Electromagnetic Resonance ◽  
Absorption Performance ◽  
Multi Band

Abstract In this paper, two kinds of dual-band metamaterial absorbers (MMAs) with stable absorption performance based on fractal structures are proposed. As the key feature, with the increase in fractal order, the fractal MMAs can reduce the weight while keeping the absorption performance. The multi-band absorption property is analyzed by multiple L-C resonances generated by the fractal structure. By virtue of good impedance matching characteristics and the synergy of the circuit and electromagnetic resonance, effective and stable microwave absorption is readily achieved. Finally, two prototypes are fabricated for demonstration, and the measurement result is consistent well with the simulation one. As expected, the proposed fractal MMAs have the advantage of low-cost, light-weight, and dual-effective absorption bands, and have great potential in the application of multi-band radar stealth.

scholarly journals Broadband Bi-Directional Polarization-Insensitive Metamaterial Absorber

Materials ◽  
2021 ◽  
Vol 14 (23) ◽  
pp. 7339
Author(s):  
Feng Tian ◽  
Xia Ma ◽  
Han Hao ◽  
Xuewen Li ◽  
Jingdao Fan ◽  
...  
Keyword(s):  
Electromagnetic Wave ◽  
Impedance Matching ◽  
Middle Layer ◽  
Metamaterial Absorber ◽  
Metal Plate ◽  
Equivalent Circuits ◽  
Practical Applications ◽  
Polarization Insensitive ◽  
Absorption Performance ◽  
Metamaterial Absorbers

Conventional metamaterial absorbers eliminate the transmitted electromagnetic wave by attaching the metal plate with the unidirectional absorption performance; these absorbers limit the practical applications to a large extent. In this paper, we present a broadband bi-directional metamaterial absorber by etching chip resistors on the resonators for expanding the bandwidth, and two orthogonal I-shaped structures are pasted on the both sides of the ultra-thin substrate (FR-4) instead of the metal plate for enhancing absorptance of the absorber. Simulated results show that absorptance of the designed absorber is larger than 0.9 in 1.43–2.51 GHz along the forward and backward directions under both TE and TM polarizations. Microwave experiments in the chamber are performed to verify the simulations, and the experimental results exhibit the excellent agreement with the simulations. Additionally, two I-shaped structures are orthogonally pasted on an ultrathin substrate, leading to the impedance-matching of both forward and backward directions, and the absorptance can be tailed dynamically via the middle layer of the substrate. The physics of the absorption are visualized by using a transmission line based on equivalent circuits. We claim that the designed bi-directional metamaterial absorber can be a good candidate for electromagnetic stealth and energy harvesting.

scholarly journals A simple method for the quantification of diclofenac potassium in oral suspension by high-performance liquid chromatography with UV-detection

2013 ◽  
Vol 49 (3) ◽  
pp. 589-597 ◽  
Author(s):  
Alexandre Machado Rubim ◽  
Jaqueline Bandeira Rubenick ◽  
Luciane Varine Laporta ◽  
Clarice Madalena Bueno Rolim
Keyword(s):  
High Performance ◽  
Low Cost ◽  
Oral Suspension ◽  
Reverse Phase ◽  
Intermediate Precision ◽  
Simple Method ◽  
Ultraviolet Detection ◽  
Relative Standard ◽  
Validation Parameters

A rapid, simple and low cost method was developed to determine diclofenac potassium (DP) in oral suspension, using a reverse-phase column (C8, 150 mm x 4.6 mm, 5 µm), mobile phase containing methanol/buffer phosphate (70:30 v/v, pH 2.5), at a flow rate of 1.0 mL/min, isocratic method, and ultraviolet detection at 275 nm. A linear response (r = 1.0000) was observed in the range of 10.0-50.0 µg/mL. Validation parameters such as linearity, specificity, precision, accuracy and robustness were evaluated. The method presented precision (repeatability: relative standard deviation = 1.21% and intermediate precision: between-analyst = 0.85%). The specificity of the assay was evaluated by exposure of diclofenac potassium under conditions of stress such as hydrolysis, photolysis, oxidation and high temperature. The method presented accuracy values between 98.28% and 101.95%. The results demonstrate the validity of the proposed method that allows determination of diclofenac potassium in oral suspension and may be used as an alternative method for routine analysis of this product in quality control.

Phosphotungstic Acid Modified Expanded PTFE based Nafion Composites

2011 ◽  
Vol 14 (4) ◽  
pp. 217-222 ◽  
Author(s):  
K. Pattabiraman ◽  
K. Ramya
Keyword(s):  
Contact Angle ◽  
High Performance ◽  
Phosphotungstic Acid ◽  
Composite Membranes ◽  
Matrix Composites ◽  
Simple Method ◽  
Impregnation Process ◽  
Matrix Modification ◽  
The Matrix ◽  
Matrix Modifications

Composite membranes have been prepared by impregnation of PFSI(perfluorosulphonic acid ionomer) solution (Nafion®) into the expanded polytetrafluoroethylene (EPTFE) matrix. The matrix was modified by Na/Naphthalene treatment and with phosphotungstic acid (PTA). The matrix modifications helped in reducing the contact angle thereby improving the impregnation process by reducing the hydrophobicity of the matrix. The fuel cell made with these composite membranes showed that the performance of PTA modified matrix is comparable to that of Na/ naphthalene modified matrix. Further the performances of matrix modified membranes were higher than that of the as received matrix-composites. PTA treatment offers a simple method of matrix modification to achieve high performance.

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