Design and Performance of Periodic Structure Absorbing Material Based Ceramic Coating

Author:Yang Chao Ning

Supervisor:luo fa


Degree Year:2018





With the development of electronic information technology,especially the combination of radar detection technology and strike weapon system with precise interception,all weapons and equipment will be great danger to survive in the war.Absorbing material as a function material that can effectively combat radar detection,which is highly valued by all countries in the world.In recent years,some studies have shown that the absorbing material composed of the artificial periodic structure and the traditional absorbing coating is expected to become a new generation of stealthy material.At present,the research on periodic structure absorbing material is mostly from the following two aspects,one is to combine the periodic structure with resin composite materials,this kind of absorbing material has a wide absorption band,but its temperature resistance,corrosion resistance and strength performance is not very good.Another kind is to use of two-dimensional or three-dimensional periodic structure with metal,this kind of material has a very strong absorption resonance peaks,but the absorbing bandwidth is too narrow,and the three-dimensional periodic structure made up of pure metal is complicated and high cost.Ceramic coating have the advantages of high temperature resistance,high strength and good chemical stability relative to resin materials.Compared with the pure metal periodic structure,the preparation process of ceramic is mature and has the advantages of corrosion resistance and high temperature,but the bandwidth is narrow.Therefore,it is necessary to study the composition of periodic structure and ceramic coating.In addition,the traditional radar absorbing coating is usually prepared by the method of painting.The preparation of coatings by atmospheric plasma spraying technology is not only simple and efficient,but also has the advantages of easy coating and low cost.In this paper,the composite of periodic structure and absorbing coatings is studied,A series of ceramic coating with different components were prepared by atmospheric plasma spraying technology.The influence of different types of periodic structure on the absorbing performance of the coating in the frequency of X-band(8.2 GHz to 12.4 GHz)is studied.The main work and conclusions are as follows:The Al2O3/TiO2 coatings were prepared through atmospheric plasma spraying technology.Microstructure and phase composition of the coating were characterized by SEM and XRD,Dielectric properties and microwave absorption properties of absorbing coating samples were studied.After that,the ceramic coating samples with better absorbing performance are selected,the absorbing material with circular periodic structure was designed,the influence of structural parameters on reflectivity of the coating were studied,the reflectivity of absorbing material with periodic structureare optimized by genetic algorithm.The results showed that the morphology of the coating showed a typical morphology of layered ceramic coating.With the increase of TiO2 content,the dielectric constant of the coating gradually increased,and the microwave absorbing property increased.The absorbing performance of the coating waws greatly improved by the circular periodic structure.When the incident angle of the electromagnetic wave is between 0 and 30 degrees,the periodic structure absorbing material shows a relatively stable absorbing performance.The CrTiO coatings were prepared by atmospheric plasma spraying,the microstructure,phase composition,dielectric properties and microwave absorption properties of the coating were characterized and analyzed.After that,the coating samples with better absorbing performance was selected.The absorbing materials with a periodic structure composed of four circular period unit and square period unit were designed,the effect of square patch,the circular patch on the reflectivity of the coating were studied.The structural parameters of period structure absorbing materials were optimized by genetic algorithm.The results show that the real and imaginary parts of the dielectric constant increase as the Cr ion doping content increases,and the coating have smaller permeability property.The absorbing properties of coating are also gradually increased as the Cr ion doping content increases.The absorbing properties of the coating are improved by the design method of combination of periodic structure,the electromagnetic wave absorption is produced by resonance effect of square metal patch,circular metal patch and bottom coating,and electromagnetic absorption of circular metal patchis is greater than the square metal patch.Compared with the previously designed Al2O3/TiO2 coating with circular periodic structure,the thickness of the CrTiO coating is thinner,but the absorbing intensity is not as good as the Al2O3/TiO2 coating.Moreover,the absorbing stability of the periodic structure absorbing material is not as good as the former under the polarized wave incident.The LaSrMnO3/Al2O3 coatings were prepared by atmospheric plasma spraying.The microstructure and phase composition of the coating were analyzed,and the dielectric constant and microwave absorbing property of the coating were studied.Afterwards,a coating with good absorbing properties is selected to design,and a absorbing material with square periodic structure is designed based on the LaSrMnO3/Al2O3 coating.The influence of various structural parameters on the reflectivity of the coating are studied.The results show that with the increase of LaSrMnO3 content,the complex permittivity of the ceramic coating increases gradually,and the absorption peak in the reflectivity curve moves to the low frequency gradually,and the intensity of absorption peak first increases and then decreases,and the minimum reflectivity value decreases.When the periodic structure is added,the reflectivity of the coating gradually presents a double absorption peak structure in the X-band.Compared with the period C,the square size a has more obvious regulation on the absorption peak position.After that,an absorbing material composed of cross type periodic structure is designed,and then the two periodic absorbing materials with different shape units are optimized by genetic algorithm.Compare the optimization results,the cross periodic structure is relative to the square periodic structure,and the absorbing performance of coating is further improved.