Magnesium-substituted Mn0.8Zn0.2Fe2O4 ferrite is synthesized by the sol–gel combustion method using citrate acid as the complex agent. The electromagnetic absorbing behaviors of ferrite/polymer coatings fabricated by...Magnesium-substituted Mn0.8Zn0.2Fe2O4 ferrite is synthesized by the sol–gel combustion method using citrate acid as the complex agent. The electromagnetic absorbing behaviors of ferrite/polymer coatings fabricated by dispersing Mn–Zn ferrite into epoxy resin （EP） are studied. The microstructure and morphology are characterized by X-ray diffraction and scanning electron microscope. Complex permittivity, complex permeability, and reflection loss of ferrite/EP composite coating are investigated in a low frequency range. It is found that the prepared ferrite particles are traditional cubic spinel ferrite particles with an average size of 200 nm. The results reveal that the electromagnetic microwave absorbing properties are significantly influenced by the weight ratio of ferrite to polymer. The composites with a weight ratio of ferrite/polymer being 3：20 have a maximum reflection loss of –16 dB and wide absorbing band. Thus, the Mn–Zn ferrite is the potential candidate in electromagnetic absorbing application in the low frequency range （10 MHz–1 GHz）.展开更多
A two-dimensional metal model is established to investigate the stealth mechanisms of radar absorbing material （RAM） and plasma when they cover the model together. Using the finite-difference time-domain （FDTD） me...A two-dimensional metal model is established to investigate the stealth mechanisms of radar absorbing material （RAM） and plasma when they cover the model together. Using the finite-difference time-domain （FDTD） method, the interaction of electromagnetic （EM） waves with the model can be studied. In this paper, three covering cases are considered： a. RAM or plasma covering the metal solely; b. RAM and plasma covering the metal, while plasma is placed outside; e. RAM and plasma covering the metal, while RAM is placed outside. The calculated results show that the covering order has a great influence on the absorption of EM waves. Compared to case a, case b has an advantage in the absorption of relatively high-frequency EM waves （HFWs）, whereas case c has an advantage in the absorption of relatively low-frequency EM waves （LFWs）. Through the optimization of the parameters of both plasma and RAM, it is hopeful to obtain a broad absorption band by RAM and plasma covering. Near-field attenuation rate and far-field radar cross section （RCS） are employed to compare the different cases.展开更多
The article presents problems related to mechanical protection of vehicles with different add-on armours against chemical,biological and radiological contamination.This applies to vehicles with additional passive,reac...The article presents problems related to mechanical protection of vehicles with different add-on armours against chemical,biological and radiological contamination.This applies to vehicles with additional passive,reactive and hybrid protection in the form of cassettes against piercing with anti-tank projectiles,piercing with their kinetic energy of impact,and as a result of chemical energy of shaped charges as well as explosively formed projectiles.It has been shown how increased ballistic protection of these vehicles at the same time reduces their decontaminability in various places of the vehicle due to the increased additional surface of the vehicle with cassettes.Prevention of contamination of these cassettes has been presented as a way of reducing hard to reach surface for decontamination and a method of insulating construction elements(stands),fixing these cassettes to the vehicle,from the environment to prevent contact with contaminated liquids and dusts.The selection of appropriate materials is shown,which may affect the improvement of the decontamination efficiency of the vehicle with such cassettes.This applies to the use of materials with low absorption of chemical warfare agents,which prevent the accumulation of large amounts of these agents on contaminated surfaces and improve the effectiveness of decontamination.It also shows how to ensure better access of the disinfectant to as much of the vehicle surface as possible,covered with cassettes that have been contaminated.It shows how a vehicle,in particular with such cassettes,can provide protection against radar detection when Radar Absorbent Material is used on vehicle cassettes.展开更多
In this paper, we present an efficient method to obtain absorbers with broadened operating frequency bands. They are accomplished by using conventional magnetic absorbing materials （MAMs） in the forms of array and m...In this paper, we present an efficient method to obtain absorbers with broadened operating frequency bands. They are accomplished by using conventional magnetic absorbing materials （MAMs） in the forms of array and mesh structures, which are similar to those in the case of a frequency selective surface. The proposed approach is verified not only by simulations but also by experimental results under the normal incidence at microwave frequencies. Moreover, the wideband absorber is lighter than the conventional magnetic absorber. These results indicate that our proposed absorbing structures can be used for designing good electromagnetic absorbers.展开更多
The impregnated radar absorbing material(RAM) honeycomb is often used to fabricate parts of the war plane for reducing radar cross section. The incident wave vector may be divided into two components: one perpendicula...The impregnated radar absorbing material(RAM) honeycomb is often used to fabricate parts of the war plane for reducing radar cross section. The incident wave vector may be divided into two components: one perpendicular to its hole and the other to its side wall. Until now, there has not been a program to calculate the input impedance or its equivalent electromagnetic parameters for the later case. In this paper, an approach for analyzing the reflection characteristics of the impregnated honeycomb when its side wall faces the incident plane wave is proposed. Experiments prove it an effective, accurate and fast solution to this subject.展开更多
基金Project supported by the Specialized Research Fund for the Doctoral Program of Higher Education of China(Grant No.20121101110014)
文摘Magnesium-substituted Mn0.8Zn0.2Fe2O4 ferrite is synthesized by the sol–gel combustion method using citrate acid as the complex agent. The electromagnetic absorbing behaviors of ferrite/polymer coatings fabricated by dispersing Mn–Zn ferrite into epoxy resin （EP） are studied. The microstructure and morphology are characterized by X-ray diffraction and scanning electron microscope. Complex permittivity, complex permeability, and reflection loss of ferrite/EP composite coating are investigated in a low frequency range. It is found that the prepared ferrite particles are traditional cubic spinel ferrite particles with an average size of 200 nm. The results reveal that the electromagnetic microwave absorbing properties are significantly influenced by the weight ratio of ferrite to polymer. The composites with a weight ratio of ferrite/polymer being 3：20 have a maximum reflection loss of –16 dB and wide absorbing band. Thus, the Mn–Zn ferrite is the potential candidate in electromagnetic absorbing application in the low frequency range （10 MHz–1 GHz）.
基金National Nature Science Foundation of China(No.90405004)
文摘A two-dimensional metal model is established to investigate the stealth mechanisms of radar absorbing material （RAM） and plasma when they cover the model together. Using the finite-difference time-domain （FDTD） method, the interaction of electromagnetic （EM） waves with the model can be studied. In this paper, three covering cases are considered： a. RAM or plasma covering the metal solely; b. RAM and plasma covering the metal, while plasma is placed outside; e. RAM and plasma covering the metal, while RAM is placed outside. The calculated results show that the covering order has a great influence on the absorption of EM waves. Compared to case a, case b has an advantage in the absorption of relatively high-frequency EM waves （HFWs）, whereas case c has an advantage in the absorption of relatively low-frequency EM waves （LFWs）. Through the optimization of the parameters of both plasma and RAM, it is hopeful to obtain a broad absorption band by RAM and plasma covering. Near-field attenuation rate and far-field radar cross section （RCS） are employed to compare the different cases.
文摘The article presents problems related to mechanical protection of vehicles with different add-on armours against chemical,biological and radiological contamination.This applies to vehicles with additional passive,reactive and hybrid protection in the form of cassettes against piercing with anti-tank projectiles,piercing with their kinetic energy of impact,and as a result of chemical energy of shaped charges as well as explosively formed projectiles.It has been shown how increased ballistic protection of these vehicles at the same time reduces their decontaminability in various places of the vehicle due to the increased additional surface of the vehicle with cassettes.Prevention of contamination of these cassettes has been presented as a way of reducing hard to reach surface for decontamination and a method of insulating construction elements(stands),fixing these cassettes to the vehicle,from the environment to prevent contact with contaminated liquids and dusts.The selection of appropriate materials is shown,which may affect the improvement of the decontamination efficiency of the vehicle with such cassettes.This applies to the use of materials with low absorption of chemical warfare agents,which prevent the accumulation of large amounts of these agents on contaminated surfaces and improve the effectiveness of decontamination.It also shows how to ensure better access of the disinfectant to as much of the vehicle surface as possible,covered with cassettes that have been contaminated.It shows how a vehicle,in particular with such cassettes,can provide protection against radar detection when Radar Absorbent Material is used on vehicle cassettes.
基金Project supported by the Aeronautical Science Foundation of China (Grant No. 2011ZF88013)
文摘In this paper, we present an efficient method to obtain absorbers with broadened operating frequency bands. They are accomplished by using conventional magnetic absorbing materials （MAMs） in the forms of array and mesh structures, which are similar to those in the case of a frequency selective surface. The proposed approach is verified not only by simulations but also by experimental results under the normal incidence at microwave frequencies. Moreover, the wideband absorber is lighter than the conventional magnetic absorber. These results indicate that our proposed absorbing structures can be used for designing good electromagnetic absorbers.
文摘The impregnated radar absorbing material(RAM) honeycomb is often used to fabricate parts of the war plane for reducing radar cross section. The incident wave vector may be divided into two components: one perpendicular to its hole and the other to its side wall. Until now, there has not been a program to calculate the input impedance or its equivalent electromagnetic parameters for the later case. In this paper, an approach for analyzing the reflection characteristics of the impregnated honeycomb when its side wall faces the incident plane wave is proposed. Experiments prove it an effective, accurate and fast solution to this subject.
