| Interference absorbing materials is a material which inserts interferer into the matrix with suitable electromagnetic parameters so that the electromagnetic wave interferes and then disappears when transmitting in the matrix.The absorbing properties of interference absorbing materials could be effectively regulated by adjusting the structural parameters of interferer,so interference absorbing materials have the advantages of simple absorbing mechanism,controllable absorbing performance and large design freedom,and become one of the research focuses of absorbing materials.Polymers have the advantages of simple molding process and good mechanical properties,and most of them have excellent electromagnetic wave permeability,so they were often used as the matrix of interference absorbing materials,so that most of the interference absorbing materials are constructed with polymer matrix.Due to the shortcomings of polymer matrix in high temperature resistance,it is difficult for polymer-based interference absorbing materials to serve in harsh and complex conditions.By analogy,ceramics with excellent wave permeability can also be used as the matrix of interference absorbing materials,and the excellent high temperature resistance,aging resistance,acid and alkali resistance of ceramics could make the ceramicbased interference absorbing materials have excellent comprehensive properties.However,the preparation of ceramic matrix composites is more difficult than that of the polymer matrix composites,which greatly limits the development of ceramic-based interference absorbing materials.This paper aims to establish the construction mechanism of ceramic-based interference absorbing materials,replace polymer matrix with ceramic matrix,explore the material system and preparation process of ceramic-based interference absorbing materials,and provide basis for the preparation of ceramic-based interference absorbing materials.In the specific research,noncompact carbon fiber film(CFF)and wire mesh screen(MWS)were first used as interferers,and quartz with excellent wave permeability was used as the main material of ceramic matrix.By adding flux and viscosity regulator and adjusting sintering process,the ceramic matrix and the interferers were well combined.By studying the influence of raw material ratio and the preparation process on the microstructure,physics,mechanics and absorbing properties of the materials,the construction mechanism of ceramic-based interference absorbing materials based on different interferers and ceramic matrixes was established,and the construction mechanism was also explained.The details of the study are as follows:(1)Take CFF as interferer,and produced ceramic matrix(SC)from the mixture of quartz,calcium carbonate,talcum powder and sodium tetraborate,a quartz ceramic-based interference absorbing material(SC/CFF)were prepared by sintering.The effects of preparation technology and CFF layer number on the microstructure,physics,mechanics and absorbing properties of SC/CFF composites were studied in detail.The key of preparing SC/CFF composites was to protect CFF from oxidation by the molten ceramic matrix during sintering.The introduction of CFF had great effect on the volume shrinkage,density and bending strength of SC/CFF composites.When the sintering temperature was 780?,the bond performance between CFF and ceramic matrix was the best,so that the SC/CFF composites possessed the highest bending strength.The electromagnetic absorbing properties of SC/CFF composites were significantly improved by using non-compact CFF as interferer.The reflectivity curves of SC/CFF composites with double-layer CFF were below-10 d B with the mean reflectivity of-11.3d B in the 8.0-18.0 GHz frequency range.(2)Using CFF as interferer,and produced foam ceramic matrix(FC)from the mixture of quartz,albite,potassium feldspar,sodium tetrborate and calcium carbonate,a foam ceramic-based interference absorbing material(FC/CFF)were prepared by high temperature foaming method."Foaming by calcium carbonate at high temperature" and "heating rapidly" were two key conditions for preparing FC matrix.At elevated temperature,the oxidation of CFF could be avoided by the melting ceramic matrix and the foaming gas.Due to the special structure of "porous inside and dense surface" of the ceramic matrix,FC/CFF composites had high total porosity of 82%-84% and closed porosity 81%-83%,possessed relatively high compressive strength of 3.3?3.5MPa and surface hardness of1.1GPa.The FC/CFF composites with double-layer CFF had the best absorbing performance with the reflectivity curve below-10 d B and the mean reflectivity of-10.9d B in the 8.0-18.0 GHz frequency range.(3)Take MWS as interferer,and produced ceramic matrix(SC)from the mixture of quartz,sodium tetrborate,talcum powder,zinc oxide and calcium carbonate,a quartz ceramic-based interference absorbing material(SC/CFF)were prepared by sintering.The influence of preparation process on the integrity of SC/MWS composites was studied in detail,and the effect of the layer number and structural parameter of MWS on the microstructure,physics,mechanics and absorbing properties of SC/MWS composites was investigated."Rapid heating and slow cooling" was the key to successfully prepare SC/MWS composites.The introduction of MWS has little effect on the density,porosity,surface hardness and compressive strength of the composites,but the layer number and structural parameter of MWS had great influence on the absorbing properties of the composites.By optimizing the structural parameters of MWS,the SC/MWS composites with single-layer MWS had good absorbing performance with the whole reflectivity curve below-6.5d B and mean reflectivity of-8.2d B in the 8.0-18.0 GHz frequency range and lowest reflectivity of-9.4d B at 13.5GHz.By combining two-layer MWS with appropriate structural parameters,the SC/MWS composites with double-layer MWS had the best absorbing performance with the whole reflectivity curve below-10 d B and mean reflectivity of-12.9d B in the 8.0-18.0 GHz frequency range and lowest reflectivity of-15.2d B at12.4GHz.By summing up,interferer could be well combined with the ceramic matrix by using scientific preparation process,so as to prepare the ceramic-based interference absorbing materials.Compared with polymer-based interference absorbing materials,the preparation process of ceramic-based interference absorbing materials was indeed more complicated.However,once the ceramic-based interference absorbing materials have been successfully prepared,they would certainly have excellent high temperature resistance,and could be used in various harsh and complex conditions,which were obviously desirable for the polymer-based interference absorbing material. |
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