Preparation, Characterization, and Microwave Absorption Properties of Cobalt-Doped SrFe12O19 Nanoparticles

2021 ◽  
Vol 16 (6) ◽  
pp. 998-1004
Author(s):  
Yuan Liu ◽  
Jie Lai ◽  
Yun Liu
Keyword(s):  
Microwave Absorption ◽  
Sol Gel ◽  
Engineering Application ◽  
Strontium Ferrite ◽  
Complex Permeability ◽  
Composite Powders ◽  
Simple Method ◽  
Pure Lead ◽  
Co Substitution ◽  
Before And After

Ferrite is the major absorbing components of conventional radar absorbing materials (RAM). However, conventional RAM made of the single-absorbing components cannot meet the comprehensive requirements of “thin, wide, light, and strong.” To overcome this limitation, a composite compound of cobalt-doped SrFe12O19 nanoparticles is currently exploited to improve absorbing ability. SrFe12−xCoxO19 (x = 0, 0.05, 0.1, 0.15, 0.20, 0.25) composite ferrites were prepared using the sol-gel method. Results show that the powders obtained are pure lead-magnetite ferrite, and the properties of the samples are improved evidently after Co substitution. At room temperature, the samples substituted using Co exhibit typical permanent magnetism. When x = 0.2, the maximum saturation magnetization and coercivity of the powders are 55.8 A·2/kg and 302.4 kA/m, respectively. The real complex permittivity part of SrFe12−xCoxO19 first increases and then decreases with the increase in x and has a maximum value of x = 0.2. The complex imaginary permittivity part fluctuates with the increase in x; it first decreases, then increases, and finally decreases. With the increase in x, the complex permeability real part of the sample does not change much between 2 GHz to 16 GHz but first increases and then decreases in the range of 16-18 GHz. The imaginary part of the complex permeability first increases and then decreases, reaching its maximum at x = 0.2. The attenuation constants and absorbing properties of the samples before and after substitution were analyzed. The matching thickness of strontium ferrite (SrFe12O19) is 5.2 mm, the matching thickness of SrFe11,8Co0.2O19 (x = 0.2) is reduced to 2.4 mm, the minimum reflectivity is −24.7 dB (13.8 GHz), and the microwave absorption bandwidth lower than −10 dB is 4.7 GHz (11.6-16.3 GHz). These results indicate that an appropriate amount of Co substitution could greatly improve the absorbing performance of SrFe12O19. This study provides a simple method for the preparation of Co doped strontium ferrite. The microwave absorbing properties of the composite powders are excellent and have potential engineering application value.

Formation and microwave absorption of barium and strontium ferrite prepared by sol‐gel technique

1993 ◽  
Vol 63 (20) ◽  
pp. 2836-2838 ◽  
Author(s):  
C. Sürig ◽  
K. A. Hempel ◽  
D. Bonnenberg
Keyword(s):  
Microwave Absorption ◽  
Sol Gel ◽  
Strontium Ferrite ◽  
Gel Technique

Preparation and Microwave Absorption Property of Nickel Spinel Ferrite

2012 ◽  
Vol 531-532 ◽  
pp. 36-39
Author(s):  
Yuan Liu ◽  
Xiang Xuan Liu ◽  
Ze Yang Zhang
Keyword(s):  
Citric Acid ◽  
Microwave Absorption ◽  
Imaginary Part ◽  
Combustion Temperature ◽  
Structural Characteristics ◽  
Spinel Ferrite ◽  
Sol Gel ◽  
Complex Permeability ◽  
Microwave Absorbing ◽  
Absorbing Property

NiFe2O4 ferrite was synthesized by sol-gel method. Its structural characteristics, morphology, electromagnetic and microwave absorption properties were analyzed by X-ray diffraction, scanning electron microscope and network analyzer, and analyzed the influence of the combustion temperature and citric acid. The results indicated that the particle size be enlarged with an increased combustion temperature and be diminished first, then increased with the increased of citric acid, and the best ratio of citric acid with metal ions for nCA: nFe: nNi = 4:2:1. Its microwave absorbing property is increased with the increased combustion temperature. Its complex permittivity imaginary part first decreases with temperature increases and then increases, the imaginary part of complex permeability with increasing temperature increases, indicating that the increase of calcination temperature, help to improve the sample microwave absorbing properties.

scholarly journals Fabrication and Electromagnetic wave absorption Properties of Co-Cu-substituted Ni-Zn Spinel Ferrite-epoxy Composites

2020 ◽  
Vol 58 (12) ◽  
pp. 887-895
Author(s):  
Ji-Eun Yoo ◽  
Young-Min Kang
Keyword(s):  
Spinel Ferrite ◽  
Sol Gel ◽  
Complex Permeability ◽  
Ferrite Powder ◽  
Frequency Range ◽  
Absorption Properties ◽  
High Frequency Region ◽  
Wave Absorption ◽  
Co Substitution ◽  
Average Grain Size

Spinel ferrites (Ni0.5Zn0.5)1-<i>x-y</i>Co<i>x</i>Cu<i>y</i>Fe2O4, (<i>x</i> = 0 and <i>y</i> = 0, <i>x</i> = 0.2 and <i>y</i> = 0, <i>x</i> = 0.1 and <i>y</i> = 0.1, <i>x</i> = 0 and <i>y</i> = 0.2) were prepared by sol-gel method and post-annealed at 1100 <sup>o</sup>C. The grain growth of the sample is very sensitive to the Cu substitution <i>y</i>. The average grain size of the non-doped sample (<i>x</i> = 0, <i>y</i> = 0) was ~400 nm and it increased to ~3 μm at the sample with <i>x</i> = 0 and <i>y</i> = 0.2. The real and imaginary parts of permittivities (<i>ε', ε"</i>) and permeabilities (<i>μ', μ"</i>) were measured on the spinel ferrite powder-epoxy (10 wt%) composite samples by a network vector analyzer in the frequency range of 0.1 ≤ <i>f</i> ≤ 15 GHz. The <i>μ'</i> and <i>μ"</i> depend on Co substitution <i>x</i> and the <i>ε'</i> is sensitive to Cu doping <i>y</i>. Reflection loss (RL), which implies electromagnetic (EM) wave absorption properties, were analyzed based on the complex permeability, permittivity spectra. In the RL map plotted as functions of sample thickness (<i>d</i>) and frequency (<i>f</i>), the intensive EM absorbing area (RL < -30 dB) shifted to a high frequency region with increasing Co substitution. This can be attributed to a permeability spectra shift, due to the increase in ferromagnetic resonance frequency produced by the Co substitution. The samples with <i>x</i> = 0.1 and <i>y</i> = 0.1, <i>x</i> = 0.2 and <i>y</i> = 0 also exhibited a very broad-ranged EM wave absorbing performance with a <i>d</i> < 3 mm, indicated by RL < -10 dB being satisfied in the frequency range 7~14 GHz.

scholarly journals Experimental Study on the Water Selective Dense Membrane under an Absolute Pressure Difference with Simplified Test Method

2021 ◽  
Vol 11 (4) ◽  
pp. 1710
Author(s):  
Jinwook Lee ◽  
Hyo-Sun Kim ◽  
Donik Ku ◽  
Jihun Lim ◽  
Minkyu Jung ◽  
...  
Keyword(s):  
Measurement Methods ◽  
Test Method ◽  
Coefficient Of Performance ◽  
Absolute Pressure ◽  
Air Conditioner ◽  
Experimental Conditions ◽  
Simple Method ◽  
Performance Factors ◽  
Dense Membrane ◽  
Before And After

Membrane-based vacuum dehumidification technology is currently being actively studied. In most studies, the performance of the membrane-based systems is evaluated under the assumption that the membrane can achieve ideal separation, which results in ideal coefficient of performance (COP) values. However, the performance factors for membranes vary depending on the experimental conditions and measurement methods. Therefore, relevant values can only be calculated if the data are measured in an environment close to that of the application conditions. The cup measurement method is a simple method to measure the permeability, however, there are limitations regarding adding variables during the experiment. To overcome these limitations, a new experimental device was constructed that combines pressurized cell with the cup method. Using the device, the performance of polyethylene-amide-bonded dense membranes was evaluated under conditions where absolute pressure differentials occurred before and after the membrane, such as in air conditioner dehumidification systems.

scholarly journals Fish bone-derived interconnected carbon nanofibers for efficient and lightweight microwave absorption

2021 ◽  
Vol 3 (2) ◽  
Author(s):  
Yangyang Gu ◽  
Peng Dai ◽  
Wen Zhang ◽  
Zhanwen Su
Keyword(s):  
Microwave Absorption ◽  
Carbon Nanofibers ◽  
Three Dimensional ◽  
Fish Bone ◽  
Absorption Properties ◽  
Simple Method ◽  
Microwave Absorption Properties ◽  
Absorption Performance ◽  
Microwave Absorption Performance ◽  
Better Than

AbstractIn this work, we demonstrated a simple method for preparing three-dimensional interconnected carbon nanofibers (ICNF) derived from fish bone as an efficient and lightweight microwave absorber. The as-obtained ICNF exhibits excellent microwave absorption performance with a maximum reflection loss of –59.2 dB at the filler content of 15 wt%. In addition, the effective absorption bandwidth can reach 4.96 GHz at the thickness of 2 mm. The outstanding microwave absorption properties can be mainly ascribed to its well-defined interconnected nanofibers architecture and the doping of nitrogen atoms, which are also better than most of the reported carbon-based absorbents. This work paves an attractive way for the design and fabrication of highly efficient and lightweight electromagnetic wave absorbers.

Silica Sol-Gel Supported Nickel Nano-Catalyst for Hydrogen Production Using Microreactors

2005 ◽  
Vol 885 ◽  
Author(s):  
Krithi Shetty ◽  
Shihuai Zhao ◽  
Wei Cao ◽  
Naidu V. Seetala ◽  
Debasish Kuila
Keyword(s):  
Steam Reforming ◽  
Average Pore Size ◽  
Sol Gel ◽  
Supported Catalyst ◽  
Silica Sol ◽  
Average Pore ◽  
Steam Reforming Of Methanol ◽  
Nano Catalyst ◽  
Before And After ◽  
Reforming Reactions

ABSTRACTThe goal of this research is to investigate the activities of a non-noble nano-catalyst (Ni/SiO2) using Si-microreactors for steam reforming of methanol to produce hydrogen for fuel cells. The supported catalyst was synthesized by sol-gel method using Ni (II) salts and Si(C2H5O)4 as starting materials. EDX results indicate that the actual loading of Ni (5-6%) is lower than the intended loading of 12 %. The specific surface area of the silica sol-gel encapsulated Ni nano-catalyst is 452 m2/g with an average pore size of ∼ 3 nm. Steam reforming reactions have been carried out in a microreactor with 50 µm channels in the temperature range of 180-240 °C and atmospheric pressure. Results show 53% conversion of methanol with a selectivity of 74 % to hydrogen at 5 l/min and 200 °C. The magnetic properties of the catalysts were performed using a Vibrating Sample Magnetometer (VSM) to study the activity of the catalysts before and after the steam reforming reactions. The VSM results indicate much higher activity in the microreactor compared to macro-reactor and Ni forms non-ferromagnetic species faster in the microreactor.

Microwave absorption properties of SrFe12O19/ZnFe2O4 composite powders

2007 ◽  
Vol 139 (2-3) ◽  
pp. 256-260 ◽  
Author(s):  
Na Chen ◽  
Guohong Mu ◽  
Xifeng Pan ◽  
Keke Gan ◽  
Mingyuan Gu
Keyword(s):  
Microwave Absorption ◽  
Composite Powders ◽  
Absorption Properties ◽  
Microwave Absorption Properties

High-Speed Synthesis and Electric Properties of Magnesium Doped Lead Titanate Ceramics

2007 ◽  
Vol 121-123 ◽  
pp. 149-152
Author(s):  
Liang Sheng Qiang ◽  
Dong Yan Tang ◽  
Xing Hong Zhang ◽  
L. Jin
Keyword(s):  
Lead Titanate ◽  
High Speed ◽  
Sintering Temperature ◽  
Water Solution ◽  
Sol Gel ◽  
Electric Properties ◽  
Synthesis Process ◽  
Pure Lead ◽  
Alcohol Water ◽  
Titanate Ceramics

By adding methyl alcohol/water solution with certain concentration into sol to hydrolysis directly and sintering the fresh sol directly, lead titanate(PbTiO3) ceramics doped with magnesium are prepared by using magnesium acetate as doper to prohibit the disadvantages contained in conventional sol-gel method, such as low hydrolytic rate, high sintering temperature, long preparation period. The changes of structure, microstructure, synthesis process and electric properties of modified ceramics are studied in detail. The sizes and morphology of high purely and high density magnesium doped lead titanate nanocrystals thus obtained are observed by TEM photographs and the structures and affection of sintering temperature of to lattice constant and sizes of nanocrystals are detected by XRD. Electric properties detection results show that doped lead titanate ceramics exhibite excellent dielectric, ferroelectric and pyroelectric properties compare with pure lead titanate.

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