Study On Preparation And Electromagnetic Properties Of Hot Pressed Sintered FeSiAl/Carbon-Based Absorbent/Al₂O₃ Composites

With the aggravation of electromagnetic wave pollution problem,electromagnetic shielding and absorbing materials have received increasing attention.The magnetic material has a low Curie temperature and is converted to paramagnetic under high temperature conditions,losing loss of capacity.Carbon materials are prone to oxidation at high temperatures and have reduced loss.The ceramic-based composite has the advantages of high temperature resistance and high strength.At present,the research on the addition of electrical/magnetic loss materials in ceramic matrix to fabricate composites of high-temperature absorbing properties and mechanical properties is increasing.In this paper,alumina-based composites are prepared by vacuum hot-press sintering technology.In this paper,FeSiAl/Al₂O₃ composites were prepared by using alumina as the matrix and flaky-ferrosilicon?FeSiAl?as the absorbent.The effects of FeSiAl content and particle size on the electromagnetic properties of the composites were investigated.On this basis,FeSiAl/FG/Al₂O₃ composites were prepared by adjusting the mass ratio of flake graphite?FG?and FeSiAl absorbent.FeSiAl/rGO/Al₂O₃ composites were prepared by adjusting the mass ratio of reduced Graphene Oxide?rGO?and FeSiAl absorbent.The mass ratio of FeSiAl to FG,the mass ratio of FeSiAl and rGO,and the influence of FeSiAl particle size on the electromagnetic properties of the composites were studied.It is expected to obtain composite materials with excellent absorbing properties and shielding properties.The microstructure and phase composition of the composites were analyzed by scanning electron microscopy and X-ray diffractometry.The mechanical properties of the composites were investigated by Vickers hardness test,density test and three-point bending test.S parameters and electromagnetic parameters of the composite material were measured by vector network analyzer.Using Matlab software to calculate the reflectivity and shielding efficiency of composites.In the FeSiAl/Al₂O₃ composite,FeSiAl is uniformly distributed in the Al₂O₃ matrix,with no new phase formed.With the increase of FeSiAl content and particle size,the microhardness of the composite decreases,the porosity increases,and the flexural strength increases.When the FeSiAl content is 15 wt.%and the particle diameter is 18-25?m,the flexural strength of composite is 458 MPa.The real and imaginary parts of the complex permittivity of the composites increase with increasing FeSiAl content and particle size.The electromagnetic shielding properties of the composites increase with increasing FeSiAl content and particle size.When the FeSiAl content is 15 wt.%and the particle diameter is18-25?m,the SE value is about 24-35 dB,and the composite is dominated by absorbing loss.The absorbing properties of the composite vary with the thickness of the sample and the matching frequency.When FeSiAl is 5 wt%and the particle size is 25-48?m,the composite has the best absorbing performance.The minimum reflection loss of-34.4 dB is achieved at11.7 GHz with thickness of 1.1 mm,and the effective bandwidth less than-10 dB reaches 1.4GHz?11.0-12.4 GHz?.In the FeSiAl/FG/Al₂O₃ composites,with the increase of FG content of FeSiAl/FG mixture,the microhardness of the composite decreases,the porosity increases,the flexural strength increases first and then decreases.As the mass ratio of FeSiAl to FG is 2:3,the flexural strength was 343.9 MPa.As the particle size of FeSiAl increases,the porosity of the composite increases,the lower the microhardness,the higher the flexural strength,and the maximum flexural strength is 326.9 MPa.The electromagnetic shielding performance of the composite increases with the increase FG content and FeSiAl particle size.When the mass ratio of FeSiAl to FG is 0:5 and the particle size of FeSiAl are 18-25?m,the SE value is about 27.3-32.8 dB.When the mass ratio of FeSiAl to FG is 4:1 and the particle size is 18-25?m,the reflection loss is-47.63 dB at 10.13 GHz with thickness of 1.3 mm,and the reflection loss values esceeding-10 dB are obtained 1.1 GHz?9.61-10.68 GHz?.In the FeSiAl/rGO/Al₂O₃ composite,with content of rGO of FeSiAl/rGO mixture increases,the microhardness of the composite decreases,the porosity increases,and the flexural strength increases.When the mass ratio of FeSiAl to rGO is 3:2,the maximum flexural strength of the composite is 349.89 MPa.As the particle size of FeSiAl increases,the porosity of the composite decreases,the higher the microhardness,the higher the flexural strengthen,and the maximum flexural strength is 359.22 MPa.When the mass ratio of FeSiAl to rGO is 1:4,the SE value of the composite is 24.6-21.9 dB when the particle size is 18-25?m.When the mass ratio of FeSiAl and rGO is 4:1 and the particle size is 18-25?m,the reflection loss less than-10 dB is obtained in the frequency of 9.75-10.87 GHz?1.12 GHz?,and the optimal minimum reflection loss of-35.42 dB is achieved at 10.2 GHz with the thickness is 1.4 mm.