scholarly journals Double-layer microwave absorber based on nanocrystalline CoFe2O4 and CoFe2O4/PANI multi-core/shell composites

2017 ◽  
Vol 35 (1) ◽  
pp. 94-104 ◽  
Author(s):  
Yewen Xu ◽  
Guozhu Shen ◽  
Hongyan Wu ◽  
Bin Liu ◽  
Xumin Fang ◽  
...  
Keyword(s):  
Double Layer ◽  
Reflection Loss ◽  
Oxidative Polymerization ◽  
Single Layer ◽  
Core Shell ◽  
Total Thickness ◽  
Absorption Bandwidth ◽  
Pani Composite ◽  
Line Theory ◽  
Minimum Reflection Loss

AbstractOrganic-inorganic nano-CoFe2O4/PANI (polyaniline) multi-core/shell composites have been successfully synthesized by chemical oxidative polymerization of aniline. The characterization results showed that the ferrite nanocrystals were efficiently embedded in PANI. The electromagnetic parameters of the composites were measured by a vector network analyser in the frequency range of 2 GHz to 18 GHz. Double-layer absorbers based on the CoFe2O4/PANI composite (matching layer) and calcined CoFe2O4 ferrite (absorbing layer) have been designed. The reflection loss of the microwave absorbers of both single layer and double-layer with a total thickness of 2.0 mm and 2.5 mm was calculated according to transmission-line theory. The results indicated that the minimum reflection loss of the CoFe2O4/PANI composite was −19.0 dB at 16.2 GHz at the thickness of 2.0 mm and −23.6 dB at 13.1 GHz at the thickness of 2.5 mm, respectively. The minimum reflection loss for double-layer absorbers reached −28.8 dB at 16.2 GHz at the total thickness of 2.0 mm, and −31.1 dB at 12.8 GHz at the total thickness of 2.5 mm. The absorption bandwidth under −10 dB was 4.2 GHz (13.8 GHz to 18.0 GHz) and 5.5 GHz (10.3 GHz to 15.8 GHz), respectively. The results show that the reflection loss and absorption bandwidth of the double-layer absorbers are obviously enhanced compared to corresponding single layer absorbers.

Synthesis and microwave absorption enhancement of BaTiO3 nanoparticle/polyvinylbutyral composites

2018 ◽  
Vol 53 (5) ◽  
pp. 593-601 ◽  
Author(s):  
Yüksel Akinay ◽  
Fatih Hayat
Keyword(s):  
Reflection Loss ◽  
Polyvinyl Butyral ◽  
Absorption Enhancement ◽  
Frequency Range ◽  
Ultrasonic Probe ◽  
Mixture Ratio ◽  
Line Theory ◽  
Extended Frequency ◽  
Probe Sonication ◽  
Minimum Reflection Loss

Barium titanate (BaTiO3)-polyvinyl butyral (PVB) composites at various weight concentrations were prepared via ultrasonic probe sonicator. The sonication was carried out at 20 kHz and 70% amplitude for about 2 h and BaTiO3 nanoparticles were dispersed well in the mixture of PVB/ethanol under probe sonication. As a microwave absorbent, the microwave absorbing properties of the BaTiO3 nanoparticle-PVB composites with different mixture ratios of 5 wt.% (RAM1), 10 wt.% (RAM2) and 15 wt.% (RAM3) BaTiO3 were investigated based on transmission line theory in the frequency range from 1 GHz to 14 GHz. The minimum reflection loss (RL) of the RAM1 reaches −3.47 dB at 5.57 GHz with a matching thickness of only 7.0 mm. For RAM2 with 4 mm and 4.2 mm thickness ( tm), the RL values are less than −10 dB obtained in the frequency 10.3–13.4 GHz. The RAM3 composite with 15 wt.% BaTiO3 mixture ratio shows a minimum reflection loss of −43.8 dB at 11.01 GHz with a −15 dB bandwidth over the extended frequency range of 10.2–13.2 GHz for a thickness of 2.8 mm and −44.2 dB at 4.77 GHz for a thickness of 6.5 mm.

scholarly journals Microwave Absorption Performance of Single-Layer and Multi-Layer Structures Prepared by CNTs/Fe3O4 Nonwoven Materials

Crystals ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 1000
Author(s):  
Rong Zhan ◽  
Jiaqiao Zhang ◽  
Qiang Gao ◽  
Qi Jia ◽  
Zhixiang Zhang ◽  
...  
Keyword(s):  
Reflection Loss ◽  
Single Layer ◽  
Frequency Range ◽  
Band Frequency ◽  
Layer Structures ◽  
X Band ◽  
Combination Scheme ◽  
Film Forming ◽  
Hot Rolled ◽  
Minimum Reflection Loss

Electromagnetic radiation can cause serious harm to the human body, such as the rise in body temperature and the decrease in immune function. In this study, the carbon nanotubes (CNTs)/Fe3O4 nonwovens were used to prepare wearable flexible absorbing materials. First, the single-layer absorbing structures were prepared by hot rolling, dipping, and film fabrication, respectively. Then, the single-layer structures were combined to form the multi-layer absorbing structures. By testing and analyzing the absorbing performance of various structures in the X-band frequency range, the optimum combination scheme was found, together with a good reflection loss value of CNTs/Fe3O4 nonwoven material. The experiment results displayed that the single-layer hot-rolled nonwovens modified by CNTs have the best wave absorbing performance. Its minimum reflection loss of −18.59 dB occurred at 10.55 GHz, and the efficient frequency occurred at 8.86–12.40 GHz. The modified film can significantly improve the absorbing performance of multi-layer structures. In addition, the absorbing performance was closely related to both the place where the absorbing film was introduced and the type of absorbing fillers. When the film-forming CNTs (FC) film was located at the bottom layer of the multi-layer structure, the hot rolled CNTs hot rolled mixed reagent film forming CNTs (HC-HM-FC) structure constructed exhibited the best absorbing effects. Its minimum reflection loss can reach −33 dB, and the effective absorbing frequency range covered half of the X-band.

Double Layer Microwave Absorption Characteristics of Barium Hexaferrite/Silica Composite for X-Band Frequencies

2018 ◽  
Vol 929 ◽  
pp. 109-115 ◽  
Author(s):  
Erfan Handoko ◽  
Iwan Sugihartono ◽  
Mangasi Alion Marpaung ◽  
Maulana Randa ◽  
Mudrik Alaydrus ◽  
...  
Keyword(s):  
Microwave Absorption ◽  
Double Layer ◽  
Reflection Loss ◽  
Barium Hexaferrite ◽  
Complex Permeability ◽  
X Ray Diffraction ◽  
Silica Composite ◽  
X Band ◽  
Line Theory ◽  
Absorption Characteristics

Microwave absorption characteristics of double layer of barium hexaferrite attached on the silica to from a composite on the basis of wave propagation theory have been investigated. Barium hexaferrite, BaFe12O19, was synthesized through ceramic method from stoichiometric mixtures of BaCO3 and Fe2O3 as precursors. The mixture was pelletized under the pressure of 10 MPa and sintered at 1100 °C for 5 hours. Silica in the forms of powder was purified by using HCl. The crystal structure of the samples was characterized using X-ray diffraction (XRD), microstructure was examined using scanning electron microscope (SEM), hysteresis curves recorded by PERMAGRAPH techniques, whereas the microwave absorbing properties for X-band was recorded using a vector network analyzer (VNA). Relative complex permeability and permittivity, and reflection loss values were calculated at given thickness according to transmittance line theory within the range 8.2–12.4 GHz. Based on this study, the layer dimension and frequency that results in low reflection loss can be estimated from the material properties of the barium hexaferrite/silica composite material.

Investigation of the electromagnetic absorption properties of Ni@TiO2 and Ni@SiO2 composite microspheres with core–shell structure

2015 ◽  
Vol 17 (4) ◽  
pp. 2531-2539 ◽  
Author(s):  
Biao Zhao ◽  
Gang Shao ◽  
Bingbing Fan ◽  
Wanyu Zhao ◽  
Rui Zhang
Keyword(s):  
Electromagnetic Wave ◽  
Reflection Loss ◽  
Core Shell ◽  
Absorption Properties ◽  
Electromagnetic Wave Absorption ◽  
The Core ◽  
Composite Microspheres ◽  
Electromagnetic Absorption ◽  
Core Shell Structure ◽  
Minimum Reflection Loss

The core–shell Ni–SiO2 composite exhibits the best electromagnetic wave absorption in the GHz range with a minimum reflection loss of −40.0 dB, which is superior to those of Ni–TiO2 and Ni microspheres.

scholarly journals Structural, microstructural, magnetic and electromagnetic absorption properties of spiraled multiwalled carbon nanotubes/barium hexaferrite (MWCNTs/BaFe12O19) hybrid

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Nurshahiera Rosdi ◽  
Raba’ah Syahidah Azis ◽  
Ismayadi Ismail ◽  
Nurhidayaty Mokhtar ◽  
Muhammad Misbah Muhammad Zulkimi ◽  
...  
Keyword(s):  
Carbon Nanotubes ◽  
Microwave Absorption ◽  
Multiwalled Carbon Nanotubes ◽  
Reflection Loss ◽  
Barium Hexaferrite ◽  
High Energy ◽  
Absorption Properties ◽  
Multiwalled Carbon ◽  
Absorption Bandwidth ◽  
Minimum Reflection Loss

AbstractMicrowave absorption properties were systematically studied for synthesised barium hexaferrite (BaFe12O19) nanoparticles and spiraled multiwalled carbon nanotubes (MWCNTs) hybrid. BaFe12O19 nanoparticles were synthesised by a high energy ball milling (HEBM) followed by sintering at 1400 °C and structural, electromagnetic and microwave characteristics have been scrutinized thoroughly. The sintered powders were then used as a catalyst to synthesise spiraled MWCNTs/BaFe12O19 hybrid via the chemical vapour deposition (CVD) process. The materials were then incorporated into epoxy resin to fabricate single-layer composite structures with a thickness of 2 mm. The composite of BaFe12O19 nanoparticles showed a minimum reflection loss is − 3.58 dB and no has an absorption bandwidth while the spiraled MWCNTs/BaFe12O19 hybrid showed the highest microwave absorption of more than 99.9%, with a minimum reflection loss of − 43.99 dB and an absorption bandwidth of 2.56 GHz. This indicates that spiraled MWCNTs/BaFe12O19 hybrid is a potential microwave absorber for microwave applications in X and Ku bands.

Facile Synthesis of Core-shell Structured CuS@PANI Microspheres and Electrochemical Capacitance Investigations

2017 ◽  
Vol 25 (6) ◽  
pp. 483-488
Author(s):  
Chunnian Chen ◽  
Qi Zhang ◽  
Chengyang Peng
Keyword(s):  
Current Density ◽  
Oxidative Polymerization ◽  
Core Shell ◽  
Discharge Process ◽  
Electrochemical Capacitance ◽  
Composite Microsphere ◽  
Pani Composite ◽  
Discharge Profile ◽  
A Current ◽  
Charge Discharge

A core-shelled structure CuS@PANI composite microsphere was successfully synthesized via chemical oxidative polymerization procedure and the electrochemical performance was investigated. The as-prepared composites were characterized by FE-SEM, TEM and XRD, and their particulate structure has been confirmed. Interestingly, the CuS microsphere was not a whole solid but composed of several sheet-like subunits, and the PANI was loosely-coated on the surface of spherical CuS particles. The advantage of this kind of core-shell structure is that PANI has better conductivity, which favors the electronic conductive channels to the CuS cores. Moreover, the loosely-attached PANI could buffer the disadvantages of the volume changes of CuS during the charge-discharge process. The galvanostatic charge/discharge profile shows a specific capacitance of 308.1 F g−1 at a current density of 0.5 A g−1 and the composite retained 71.6% of its initial capacitance after 1000 cycles at a current density of 1 A g−1.

scholarly journals Effect of different permeability on electromagnetic properties of absorbing materials

2018 ◽  
Vol 197 ◽  
pp. 02015 ◽  
Author(s):  
Riser Fahdiran ◽  
Yuliyanti Dwi Utami ◽  
Erfan Handoko
Keyword(s):  
Transmission Line ◽  
Reflection Loss ◽  
Single Layer ◽  
Electromagnetic Properties ◽  
Complex Permeability ◽  
Transmission Line Theory ◽  
Microwave Frequencies ◽  
Microwave Absorbing Properties ◽  
Absorbing Materials ◽  
Line Theory

In this study, we have simulated and investigated electromagnetic properties of six types materials using a single layer metal backed absorber model that were determined at microwave frequencies 8.2 up to12.4 GHz. The reflection loss was simulated for different thicknesses in the range of 0.85 to 1.05 mm based on the relative complex permeability and permittivity referring to transmission line theory. The optimal microwave absorbing properties was be resulted by A3 sample. The minimum RL of −23.84 dB can be obtained at 10.72 GHz with thin thickness of 0.95 mm. This method paves a new avenue to design magnetic and dielectric absorbing materials.

Electromagnetic and Microwave Absorption of Nanocrystalline Alloy Fe0.2(Co0.2Ni0.8)0.8 and Nanocomposite SrFe12O19/Ni0.5Zn0.5Fe2O4 Microfibers

2014 ◽  
Vol 1035 ◽  
pp. 355-360
Author(s):  
Min Li ◽  
Zhou Wang ◽  
Hong Bo Liu ◽  
Xiang Qian Shen
Keyword(s):  
Microwave Absorption ◽  
Double Layer ◽  
Reflection Loss ◽  
Layer Structure ◽  
Nanocrystalline Alloy ◽  
Electromagnetic Parameter ◽  
Total Thickness ◽  
Absorption Properties ◽  
Microwave Absorption Properties ◽  
Double Layer Structure

Magnetic nanocrystalline alloy Fe0.2(Co0.2Ni0.8)0.8 microfibers and nanocomposite SrFe12O19/Ni0.5Zn0.5Fe2O4 microfibers are used as the absorbents in the double-layer structure for microwave absorption. The double-layer absorbers with a total thickness of 2 mm consisting of Fe0.2(Co0.2Ni0.8)0.8 and nanocomposite SrFe12O19/Ni0.5Zn0.5Fe2O4 microfibers are designed, and their microwave absorption properties are predicted based on the electromagnetic parameter measurements. The results show that the double-layer absorber with the absorption layer of SrFe12O19/Ni0.5Zn0.5Fe2O4 microfibers and the thickness of 0.6 mm has the best microwave absorption properties, with the bandwidth ( the reflection loss less than −10 dB) of 7.3 GHz ranging from 10.7 GHz to 18 GHz, and the maximum reflection loss of −71.4 dB at 12.1 GHz.

scholarly journals The influence of some factors on the electrical conductivity and particle size of core/shell polystyrene/polyaniline composites

2005 ◽  
Vol 70 (11) ◽  
pp. 1263-1271 ◽  
Author(s):  
Gordana Nestorovic ◽  
Slobodan Jovanovic ◽  
Katarina Jeremic
Keyword(s):  
Particle Size ◽  
Size Distribution ◽  
Oxidative Polymerization ◽  
Composite Particles ◽  
Core Shell ◽  
Chemical Oxidative Polymerization ◽  
Electrically Conductive ◽  
Pani Composite ◽  
Order Of Magnitude ◽  
Polyaniline Composites

The electrically conductive, micron-sized, core/shell polystyrene (PS)/polyaniline (PANI) composite particles were synthesized by chemical oxidative polymerization of aniline in the presence of micron-sized PS particles in 1 M HCl. The conditions of the dispersion polymerization of styrene were optimized. The influence of the initiator type employed for the chemical oxidative polymerization of aniline and the aniline (ANI) concentration on the PS/PANI particle size and size distribution and their conductivity was investigated. The obtained results show that the conductivity of the samples increased with increasing ANI concentration. The conductivity of the PS/PANI composite particles obtained with the highest ANI concentration was of the same order of magnitude as that for PANI powder. The particle size did not depend on the concentration of ANI, while the particle size distribution was narrower at higher concentrations of ANI. .

scholarly journals Enhanced Electromagnetic Wave Absorption Properties of Ultrathin MnO2 Nanosheet-Decorated Spherical Flower-Shaped Carbonyl Iron Powder

Molecules ◽  
2021 ◽  
Vol 27 (1) ◽  
pp. 135
Author(s):  
Zhengwei Qu ◽  
Yi Wang ◽  
Pingan Yang ◽  
Wei Zheng ◽  
Nan Li ◽  
...  
Keyword(s):  
Electromagnetic Wave ◽  
Iron Powder ◽  
Oxidation Resistance ◽  
Reflection Loss ◽  
Carbonyl Iron ◽  
Absorption Properties ◽  
Absorption Bandwidth ◽  
Electromagnetic Wave Absorption ◽  
Wave Absorption ◽  
Minimum Reflection Loss

In this work, spherical flower-shaped composite carbonyl iron powder@MnO2 (CIP@MnO2) with CIP as the core and ultrathin MnO2 nanosheets as the shell was successfully prepared by a simple redox reaction to improve oxidation resistance and electromagnetic wave absorption properties. The microwave-absorbing properties of CIP@MnO2 composites with different filling ratios (mass fractions of 20%, 40%, and 60% after mixing with paraffin) were tested and analyzed. The experimental results show that compared with pure CIP, the CIP@MnO2 composites have smaller minimum reflection loss and a wider effective absorption bandwidth than CIP (RL < −20 dB). The sample filled with 40 wt% has the best comprehensive performance, the minimum reflection loss is −63.87 dB at 6.32 GHz, and the effective absorption bandwidth (RL < −20 dB) reaches 7.28 GHz in the range of 5.92 GHz–9.28 GHz and 11.2 GHz–15.12 GHz, which covers most C and X bands. Such excellent microwave absorption performance of the spherical flower-like CIP@MnO2 composites is attributed to the combined effect of multiple beneficial components and the electromagnetic attenuation ability generated by the special spherical flower-like structure. Furthermore, this spherical flower-like core–shell shape aids in the creation of discontinuous networks, which improve microwave incidence dispersion, polarize more interfacial charges, and allow electromagnetic wave absorption. In theory, this research could lead to a simple and efficient process for producing spherical flower-shaped CIP@MnO2 composites with high absorption, a wide band, and oxidation resistance for a wide range of applications.

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