Separation Of Magnetospheres Of Fly Ash And Preparation Magnetospheres@C And Study On Absorption Properties

Fly ash magnetospheres are one of the main components of by-products produced after coal combustion.The fine separation and high value-added functionalization of magnetospheres are of great social,economic and academic value.1)In this paper,the combined process of magnetic separation,shaker and particle size classification was used to realize the fine classification of fly ash magnetospheres.Through the characterization of the microstructure,chemical composition and mineral phase of the magnetospheres,it was found the magnetospheres were mainly composed of magnetite,maghemite,hematite,magnesium ferrite and other iron-bearing phases and quartz.Fe was the main component element;The lower the iron content of magnetospheres,the weaker the magnetic properties,the smaller the density,the larger the spaces between the spinels,and the more aluminosilicates;As the particle size decreased,the size of iron spinel particles inside the magnetospheres decreased and the distribution becomed more uniform.2)Taking the natural advantage of iron oxides in magnetospheres,magnetospheres@C composites were prepared by chemical vapor deposition.Through the comparison of the amount of carbon deposition and graphitization degree,it was found that increasing the growth temperature accelerated the carbon deposition rate and increased the graphitization degree,but when the temperature was higher than 750℃,the I_D/I_Gvalues increased;With the increase of growth time,the amount of carbon deposition increased,the carbon deposition rate decreased,and the I_D/I_Gvalues increased;The increase of C₂H₄partial pressure increased the carbon deposition rate and the decrease of H₂partial pressure increased the I_D/I_Gvalues;The grinding process increased the deposition rate of carbon,but did not affect the saturated deposition amount of carbon;Delaying the cooling stage contributed to the sufficient reaction and the stable precipitation of dissolved carbon atoms.In the reaction stage,the iron particles gradually underwent phase transition and eventually existed in cementite;The deposition of carbon materials caused the whole magnetospheres to crack and form core@shell structure at the top of the carbon materials.3)Through the characterization of the electromagnetic parameters of the magnetospheres@C,it was found that theε’values of the magnetospheres@C increased due to the interface polarization and the dipole polarization at the defect of the carbon materials,and itsε"values increased due to the increase of electrical loss caused by the graphite carbon materials;The magnetic loss of magnetospheres@C was increased because of the cementite core with higher saturation magnetization.Under the synergistic effect of polarization loss,electric loss,magnetic loss and multiple reflections caused by core@shell structure,the magnetospheres@C had good microwave absorption capacity.The effective absorption bandwidth of 2 mm magnetospheres@C composite can reach 4.3 GHz,and the minimum reflection loss was-32.4 d B,indicating that magnetospheres@C have potential advantages as microwave absorbing materials.