Study On The Design And Properties Of Temperature-insensitive Refractory Metamaterial Absorber

Microwave absorbers?MAs?have important applications in military stealth,electromagnetic compatibility,electromagnetic pollution protection and other fields.With the development of weaponry and equipment,modern warfare requires aircraft to have excellent high-temperature resistance in addition to good stealth performance.Although traditional refractory microwave absorbers?rfMAs?developed have both stealth and refractory performance,due to single electrical loss mechanism,the problems such as larger thickness,absorption sensitive to temperature,narrow bandwidth and the complex preparation process is seriously restricted in development and application.Metamaterial absorber have advantages of thin thickness,strong absorption,flexible designability and so on.However,due to the majority of metal-polymer materials system,current metamaterial absorber are not suitable for high temperature environment.Herein,we propose to use the design method of metamaterials and selects the high temperature resistant raw materials to designs and prepares two types of high temperature microwave absorber for solve the problems of single absorption mechanism,temperature sensitivity and narrow bandwidth andcomplex preparation process of traditional high temperature microwave absorber.The details as follows:Firstly,we have designed and experimentally demonstrated a refractory metamaterial microwave absorber?rfMMA?with the absorption insensitive to temperature by elaborately integrating refractory ceramics of conductive titanium diboride?TiB₂?and dielectric alumina?Al₂O₃?.The as-proposed all-ceramic rfMMA shows strong absorption in the X-band due to the magnetic resonance determined by the geometrical design of the metamaterial structure and the dielectric properties of Al2O3.A precise circuit model with clear physical implications is established to interpret and guide the metamaterial design.The results show that the absorption of as-proposed rfMMA almost remains when the temperature varies between 25°C and800°C since the geometrical parameters and dielectric properties of Al2O3 are nearly independent of temperature.The excellent chemical stability of TiB₂ and Al₂O₃ at high temperature further ensures the long-term service of the rfMMA,as confirmed by experiments.Secondly,A design and preparation method of high temperature broadband metamaterial microwave absorber are proposed.The broadband absorbing properties with the absorptivity over 90%in the whole X band are obtained,and the absorbing metamaterials working at room temperature up to 400°C.The structural parameters were obtained through finite element simulation and optimization.The preparation was completed by screen printing.Analysis shows that the absorption of electromagnetic waves by the absorbing metamaterials is due to the broadband impedance matching caused by the magnetic resonance mechanism and the loss of the electromagnetic waves is dominated by the ohmic loss occurring in the ohmic sheet.The change of the sheet resistance of the upper resistance film is the main factor that affects the absorption performance of metamaterials at high temperature.Used by silicon aluminate-graphite composite ohmic sheet at room temperature to 400°C have relatively stable electrical conductivity,and thus the wave absorption performance can keep the good stability.The high-temperature metamaterial microwave absorber has the advantages of wide bandwidth,strong absorption,thin thickness and convenient preparation and is expected to be used in the fields of high temperature absorbing wave and electromagnetic compatibility.