Microwave Absorption Of Plasma Sprayed Al₂O₃ Ceramics

With the development of radar detection technology,the absorbing coating on equipment surface has higher performance requirements.At present,there are many reports on the preparation of alumina-based ceramic coating and thermal barrier coating by plasma spraying technology,but there are few researches on the preparation of alumina-based ceramic absorbing coating by plasma spraying technology.Therefore,it is of practical significance to prepare alumina-based ceramics by plasma spraying and study the dielectric properties and absorbing properties of the coatings.In this paper,the phase composition,surface morphology,surface and section microhardness of the absorbing coating under different spraying characteristic parameters,as well as the phase composition and absorbing properties of the coating after heat treatment were studied by using the characteristic plasma spraying parameter（CPSP）control and optimization scheme.The main research contents and results of this paper are as follows:1.Spray feeding with different ball milling time was prepared by ball milling method.It was found that the morphology of spray feeding was closely related to the ball milling time.With the increase of ball milling time,Mo Si₂and Al₂O₃and Cu particles are the first to be crushed in spray feeding,depending on the hardness of the material itself.By phase analysis,the X-ray diffraction pattern of spraying feed of different milling time did not change obviously,indicating that mechanical alloying did not occur in the ball milling process and spraying feed was not polluted.2.Four kinds of coating with different spraying characteristic parameters were prepared by characteristic plasma spraying parameters.It is found that the absorbing coating mainly contains six phases including Al₂O₃,Mo Si₂,Cu,Mo₅Si₃,Si O₂and Cu₂O with the increase of spraying characteristic parameters.Mo₅Si₃,Si O₂and Cu₂O are produced in the process of spraying.3.The microhardness of the absorbing coating increases with the increase of spraying characteristics and parameters.Due to the increase of the melting area of the coating,the bonding force of the coating increases;The porosity of the absorbing coating decreases gradually with the increase of the characteristic spraying parameters.The micrograph shows that the increase of molten particles fills the pores in the absorbing coating,resulting in the decrease of porosity.4.At room temperature,when the characteristic spraying parameters are 0.28,0.34 and0.38,the absorbing coating has certain absorbing performance,and the prepared absorbing coating has the absorption peak with the minimum reflection loss less than-5d B in x-band.5.After heat treatment,the absorbing coating prepared by spraying characteristic parameters of 0.28 and 0.34 has certain absorbing performance,It has certain wave absorption performance,and the absorption rate of electromagnetic wave is more than 50%.The reason that affects the absorbing performance of the coating is that Si O₂is produced on the surface of the coating after heat treatment,thus affecting the absorbing performance of the absorbing coating.