Study on space absorbing of multilayer MWCNTs/Fe3O4/NBR composites

In order to meet the requirements of “wide, thin, strong and light” for military stealth materials, it is of great practical value to study the absorbing characteristics of multi-layer MWCNTs/Fe3O4/NBR absorbing materials in space. First, we use the large-scale software COMSOL Multiphysics to simulate the absorbing characteristics of the composite thin plate in space. Then the four-port network matrix is used to calculate the absorbing characteristics of the composite plate in space. Finally, the Free-Space method is used to measure the reflection attenuation loss, and the results of the three methods are compared and analyzed. The results show that when the frequency is 10 GHz, the reflection loss of multi-layer MWCNTs/Fe3O4/NBR reaches the maximum value of −27.91, −27.01 and −22.56 dB by COMOSL numerical simulation, four-port network the matrix and Free-Space experimental measurement. The results of the three methods show that the reflection loss is less than −10 dB in the frequency band of 6–14 GHz.

STUDY OF THE INFLUENCE OF THE TILT ANGLE OF VERTICAL STABILIZERS OF AN AIRCRAFT ON THE EFFECTIVE SCATTERING SURFACE

Рассматривается зависимость значения эффективной площади рассеяния (ЭПР) самолета от угла наклона вертикальных стабилизаторов. Моделирование производится с использованием метода геометрической теории дифракции и физической оптики, так как размеры объекта во много раз превосходят размеры длины волны. Для облучения использовалась плоская волна X-диапазона - частота 10 ГГц. По полученным результатам отражения электромагнитной волны от объекта были построены диаграммы обратного рассеяния, на основе которых была сформирована таблица, содержащая максимальные значения эффективной площади рассеяния. Было замечено, что максимальное значение эффективной площади рассеяния возникает в ситуации, когда отсутствует какой-либо наклон вертикальных стабилизаторов, и при изменении угла наклона вертикальных стабилизаторов на 5 градусов наблюдается значительное понижение максимального уровня ЭПР. При этом возможно возникновение повторных отражений от горизонтальных хвостовых стабилизаторов, что, в свою очередь, приведет к повышению уровня эффективной площади рассеяния. Грамотная оптимизация угла наклона вертикальных стабилизаторов самолета позволяет добиться значительного снижения уровня ЭПР при сохранении аэродинамических характеристик самолета, а внедрение специальных композитных стелс материалов позволяет еще сильнее понизить уровень ЭПР The article considers the dependence of the value of the effective scattering area (ESA) of the aircraft on the tilt angle of the vertical stabilizers. Modeling is performed using the method of the geometric theory of diffraction and physical optics since the dimensions of the object are many times larger than the dimensions of the wavelength. For irradiation, an X-band plane wave was used - a frequency of 10 GHz. Based on the results of the reflection of the electromagnetic wave from the object, backscatter diagrams were built, on the basis of which a table was formed containing the maximum values of the effective scattering area. It was noted that the maximum value of the effective scattering surface occurs in a situation where there is no inclination of the vertical stabilizers, while when the angle of inclination of the vertical stabilizers is changed by 5 degrees, a significant decrease in the maximum ESA level is observed. In this case, repeated reflections from horizontal tail stabilizers may occur, which, in turn, will lead to an increase in the level of the effective scattering surface. Competent optimization of the angle of inclination of the vertical stabilizers of the aircraft allows one to achieve a significant decrease in the ESA level while maintaining the aerodynamic characteristics of the aircraft, and the introduction of special composite stealth materials allows one to further reduce the ESA level

3D porous biomass-derived carbon materials：biomass sources，controllable transformation and microwave absorption application

Nowadays, to prevent acute electromagnetic pollution and develop efficient stealth materials, enormous efforts have been taken to pursuit high-performance microwave absorbing (MA) materials. Comparing to classical microwave absorbers, biomass-derived porous...

Insights into the flexibility of ZrMxOy (M = Na, Mg, Al) nanofibrous membranes as promising infrared stealth materials

An undersized dopant dependent brittle to flexible transition in ZrMxOy (M = Na, Mg, Al) nanofibrous membranes was revealed. Al doped zirconia nanofibrous membranes with an ultra-flexibility of 23 mN exhibit low infrared emissivity.

Double Negative Property in Co/YIG Prepared by Low Temperature Impregnation Process

Impregnation method was used for fabricating Co/YIG (Y3Fe5O12) composites under low temperature, and the electromagnetic properties were tuned by adjusting the content (0 wt% - 35 wt%) and microstructure of the metal in composites. The XRD and SEM were used to analyze the phase and microstructure. Electromagnetism properties including reactance, permittivity and permeability of the composites were tested using impedance analyzer (10 MHz~1 GHz). The results indicated that, the high cobalt content leads to the formation of three-dimensional cobalt networks on the pore walls of porous YIG gradually, and their electromagnetic properties have also been changed significantly with the Co content increasing. Especially, double negative properties were achieved in Co/YIG composites when the content of Co reached 35 wt% at the frequency band of 575 MHz-1 GHz. The appearance of double negative properties in cermets provides promising applications in electromagnetic stealth materials, microwave antenna, and traveling wave tubes.