Design Of Fe₃O₄ Based Broadband Electromagnetic Functional Material Structure And Direct Write Printing Process

With the development of modern information technology,electromagnetic waves have become the primary medium for the development of communication,sensing,wireless control,and computer technology,which are widely used in communication,medicine,national defense,industry,household electronic appliances,etc.It is an essential tool for the interconnection of everything and human understanding of the microscopic world.How to efficiently use electromagnetic waves while shielding electromagnetic interference and reducing electromagnetic radiation is an important direction for the development of modern technology.Electromagnetic functional materials have specific effects on electromagnetic waves’reflection,absorption,and transmission.They are an essential means of efficiently using electromagnetic waves for communication and display services while reducing electromagnetic interference and radiation hazards.There are many kinds of electromagnetic functional materials.Different electromagnetic functional materials must regulate the reflection,absorption,and transmission of electromagnetic waves in different wavelengths.There are still few multi-band compatible ultra-wide electromagnetic functional material systems.In this paper,based on the ability of Fe₃O₄ nanoparticles to absorb microwave electromagnetic waves with both dielectric and magnetic losses and the magnetic response of its dispersion system with structural color effect,we develop efficient ultra-wide electromagnetic functional material devices for microwave and visible light regulation by starting from the structural design of composite materials and the regulation of dispersion system with the help of direct writing 3D printing and molding.The main research contents and conclusions of this thesis are as follows:（1）Magnetically responsive Fe₃O₄ nanoparticles with different particle sizes were prepared by a solvothermal method using two different chemical structures of poly（4-styrenesulfonate-co-maleic acid）sodium salt（PSSMA）as surfactants and modulating the reaction conditions,respectively.Magnetically responsive Fe₃O₄ nanoparticles with different particle sizes were prepared,and the effects of deionized water and ferric chloride addition on Fe₃O₄ particle size were investigated separately to probe the reflection of Fe₃O₄ with different particle sizes and dispersion solvents in the visible light range.The results show that Fe₃O₄ at190 nm synthesized with PSSMA（3:1）as surfactant under a weak alkali environment has excellent optical properties,with reflectance up to 55%in aqueous dispersion and 70%in ethylene glycol（EG）.（2）Using direct-write 3D printing technology（DIW）,biocompatible polydimethy-lsiloxanes（PDMs）were selected,and Fe₃O₄/EG/PDMs printing pastes with optical properties were formulated,Fe₃O₄/EG/PDMs magnetic response absorbing materials were molded using DIW technology,their morphology was characterized and electromagnetic parameters were tested,and based on these parameters CST simulations were used to calculate The reflection loss of Fe₃O₄ samples with different particle sizes and mass fractions was calculated by CST simulation.It is shown that the 30 wt%Fe₃O₄ composite has a weak attenuation capability,with the most substantial absorption peak at t=6.6 mm thickness,frequency f=7.78 GHz,reflection loss of-10.12 d B,and adequate absorption bandwidth of 0.3 GHz.（3）Based on the preparation study,optical properties,and wave absorption properties of Fe3O4,a multifunctional Fe₃O₄/r GO composite with a three-dimensional network structure was designed to compensate for its deficiencies in microwave absorption properties.The effect of r GO content on the optical properties and wave absorption properties of Fe₃O₄/r GO was investigated by in situ growth of Fe₃O₄ with GO as the substrate using the solvothermal method.It was found that the Fe₃O₄/r GO aqueous dispersions showed good optical properties with magnetic field under the condition of the applied magnetic field,and the maximum reflectivity of each sample was above 60%,and the maximum reflectivity reached 90%when the GO addition was 0.2;the matching thickness of 20 wt%Fe₃O₄/r GO multifunctional composite became thinner compared with Fe3O4,and the frequency band of the minimum reflection loss shifted to high frequency.While the 50 wt%Fe₃O₄/r GO multifunctional composite exhibits good microwave absorption performance with the most substantial absorption peak of-53.3 d B at 10.78 GHz and an adequate absorption bandwidth of 3.04 GHz.