Study On Absorbing Performance Of Carbon Fiber-Ferrite Cement-Based Composite

At present,with the rapid development of electronic technology,the impact of electromagnetic radiation on humans and the environment has become increasingly obvious.Therefore,research on cement-based absorbing materials is of great value for improving the electromagnetic environment and reducing the harm of electromagnetic wave radiation.This thesis is based on electromagnetic theory and material absorbing mechanism.Through a combination of experimental research,theoretical analysis and numerical simulation,chopped carbon fiber and ferrite are used as absorbing agents,and carbon fiber and ferrite are replaced by equal amounts of cement quality.They were mixed into the cement base to prepare carbon fiber-ferrite cement-based composite absorbing materials;the physical and mechanical properties,electromagnetic properties and microstructure of the prepared materials were studied;based on the electromagnetic wave finite difference time domain method（FDTD）,The electromagnetic wave absorbing performance of steel mesh reinforced carbon fiber-ferrite cement-based composite absorbing materials is studied,which provides methods and ideas for designing cement-based composite absorbing materials and predicting their absorbing performance.The main research conclusions of the thesis are as follows:（1）The incorporation of carbon fiber will increase the water consumption for the standard consistency of cement-based materials,while ferrite incorporation decreases the water usage;the setting time of cement-based materials will increase with the increase of carbon fiber and ferrite;with the addition of ferrite or carbon fiber,the heat of hydration of cement materials will decrease.（2）Under the condition of meeting the requirements of mechanical properties of materials,Adding ferrite or carbon fiber will reduce the mechanical properties of the cement mortar material;among them,30%ferrite content+The 0.5%carbon fiber content cement mortar material has the best compressive performance and flexural performance.（3）When the content of ferrite is unchanged and carbon fiber is added,the resistivity of ferrite-carbon fiber cement mortar material Will decrease with the increase of carbon fiber content.（4）Experimental research shows that the imaginary part of the dielectric constant and the dielectric loss factor of pure carbon fiber materials are significantly higher than that of cement paste.Pure carbon fiber materials have good dielectric loss performance;ferrite has high magnetic properties due to its ferromagnetism.Loss characteristics:adding carbon fiber and ferrite to the cement matrix can effectively improve the ability of the ferrite-carbon fiber cement-based composite absorbing material to absorb electromagnetic waves.（5）AFter 28 days of standard curing,6 sets of cement-based specimens（including pure cement paste specimens,ferrite-cement paste specimens,carbon fiber-cement paste specimens,carbon fiber-ferrite cement paste test specimens Among the hydration products of the sample）,there are CH crystals（calcium hydroxide）,C₂S（dicalcium silicate）,C₃S（tricalcium silicate）,AFt（calcium sulfoaluminate）and C-S-H（calcium silicate）gels Component;There are diffraction peaks of Fe₂O₃in the hydration products of the specimens doped with ferrite.（6）The SEM test results of each cement-based specimen show that the hydration product CSH gel is fibrous microscopically,AFt crystals are needle-shaped and rod-shaped microscopically,CH is plate-shaped microscopically,and ferrite microscopically It is spherical.（7）The electromagnetic wave finite difference time domain method（FDTD）can effectively simulate the absorbing performance of steel wire mesh reinforced carbon fiber-ferrite cement-based composites;Numerical simulation results of wave absorbing performance of steel mesh reinforced carbon fiber-ferrite cement-based composites show,30%ferrite+0.5%carbon fiber content steel mesh reinforced cement-based composite material has the best microwave absorbing performance,The steel mesh reinforced ferrite-carbon fiber cement-based composite material has a reflectivity of less than-5d B for electromagnetic waves at frequencies from 8 to 18 GHz.And the reflectivity of electromagnetic waves at 3.5GHz can reach the minimum value of-17.23d B;30%ferrite+0.5%carbon fiber content steel mesh reinforced cement-based composite material absorbs 8-18GHz frequency electromagnetic wave,the best matching thickness is 24mm.