Preparation And Electromagnetic Shielding Performance Of C_f/AL₂O₃ Ceramic Composites With Multi-layer Parallel Arrangement

Two-dimensional(2-D)materials and ceramics have complementary advantages.Ceramics are lightweight and resistant to high temperatures.Most of the 2-D materials have high-strength mechanical properties and excellent electrical properties.Composite with different kinds of ceramics makes the materials different physical and chemical properties.,which also are good electromagnetic interference(EMI)shielding material.However,2-D materials are easy to agglomerate and unevenly disperse in the matrix,which reduces the effective shielding effectiveness(SE)of the composites.Besides,the amount of 2-D materials to be doped is large,which causes preparation difficult.In this paper,the Cf/Al2O3 ceramic composites with multiple layers of parallel arrangement were designed and prepared,and their composition and shielding properties were studied.In this thesis,the electromagnetic shielding principle and the electromagnetic shielding characteristics of various materials were briefly described.The second chapter introduced the experimental process and experimental methods.The third chapter gave the basic principle of Finite Difference Time Domain(FDTD)method,and simulated the electromagnetic shielding perfomance of carbon fiber and alumina ceramic composites with different layers in parallel.Finally,the vacuum hot pressing sintering of alumina at 1300? was introduced and the method was applied to the preparation of multi-layer parallel arrangement of Cf/Al2O3 to further analyze the electromagnetic shielding properties of the composite.Results indicate that parallel aligned non-woven carbon fiber layers contribute significantly to the total EMI shielding effectiveness(SET)of Al2O3 composites by largely enhancing the EMI absorption,and seven parallel aligned thin non-woven carbon fiber layers finally make the almost microwave-transparent Al2O3 an excellent EMI shielding material with an EMI SET as high as 29?32 dB in the X-band frequency range.The volume fraction of carbon fibers in Al2O3 composites with seven carbon fiber layers is calculated to be only 0.5%,and therefore the EMI SE enhancement efficiency by parallel aligned large non-woven carbon fiber layers is much higher than other highly conducting nano fillers.It validates the significance of multiple reflections in achieving high EMI shielding properties in ceramic composites and provides an instructive approach to design efficient EMI shielding ceramic composites.