Study On Basic Properties And Microwave Absorbing Properties Of Graphene-Fe₃O₄ Cement Based Materials

Electromagnetic interference and electromagnetic radiation generated by various electronic and electrical equipments affect people s production and life.Therefore,how to reduce the electromagnetic interference between electromagnetic signals and the damage caused by electromagnetic radiation has become a hot issue in scientific research.At present,electromagnetic shielding and electromagnetic absorption are two general methods for resisting electromagnetic interference and electromagnetic radiation.However,electromagnetic shielding technology can not fundamentally weaken or eliminate electromagnetic waves,and even easily cause "secondary interference" of reflected electromagnetic waves on incident electromagnetic waves,so its application range is limited.Electromagnetic absorption technology absorbs and attenuates electromagnetic waves by converting electromagnetic waves entering the absorbing material into thermal energy or other forms of energy dissipation,that fundamentally solved the "electromagnetic pollution."Therefore.,it is necessary to prepare cement-based absorbing building materials and reduce electromagnetic pollution in the environment.In this paper,nano-Fe3O4 with dual complex properties and GR GO with resistance loss properties are selected as cement-based building materials for cement-based absorbing materials.0.01wto%?0.07wt%G?R,0.01wt%?0.07wt%GO and 5wt%?20wt%nano-Fe3O4 three kinds of absorbing agents are added to the cement matrix,study the basic properties of the corresponding cement-based composite materials.,including hydration heat,hydration products,strength and electrical resistivity,on the basis of ensuring the strength of the cement-based material,the mixing ratio of the minimum resistivity is obtained.At the same time,in the 0?3GHz frequency band,the subject used the coaxial probe method and the transmission/reflection method to test the dielectric constant and magnetic permeability of the corresponding cement-based materials under different amounts of GR,GO and Fe3O4,and the reflectivity of the above cement-based materials was tested by coaxial method,the effects of GR,GO and Fe3O4 on the absorbing properties of cement-based materials were analyzed.The main conclusions are as follows:(1)The effects of GR.,GO and Fe3O4 on the hydration heat,hydration products,strength and electrical resistivity of cement-based materials were discussed.The experimental results show that GR and GO can increase the total amount of hydration heat release of cement-based materials due to small size effect;X-ray diffraction(XRD)analysis shows that after the incorporation of GR and GO.,the cement-based material produces more hydration product-ettringite,nano-Fe3O4 can react with hydration product CH to form Fe-ettrimgite which is also the main reason for Fe3O4 to increase the total hydration heat release of cement-based materials;O.Olwt%?0.07wt%GR,GO can increase the strength of cement-based materials to varying degrees and 0.03wt%is GR,GO optimal intensity.5wt%of nano-Fe3O4 can enhance the cement-based material s strength due to its large specific surface area.However,if the content of Fe3O4 exceeds 5%by weight,the fluidity of the cement-based material will be deteriorated,which will hinder the hydration reaction,reducing the strength of the sample;After the combination of GR and GO with Fe3O4 and cement into the cement-based material,the strength of the sample will be reduced due to the encapsulation" of Fe3o4 to GR and GO and the "obstruction" of GR.,GO to Fe3O4 and CH secondary hydration.O.Olwt%?0.03wt%of GR and GO can make the resistivity of cement-based materials decrease in different degrees during 3?28 days and 0.03wt%addition is the minimum resistivity of GR or GO;5wt%?10wt%Fe3O4 can reduce the electrical resistivity of cement-based materials and 10wt%addition is the minimum resistivity of Fe3O4,but adding 15wt%?20wt%FeO4 is not obvious reducing the electrical resistivity of cement-based materials;Adding GR and GO has little effect on the electrical resistivity of Fe3O4 cement-based materials.(2)In the 0?3GHz frequency band,the addition of GR will increase the ?',?" and tan?e of the cement-based samples and the better dielectric loss performance of the 0.05wt%GR sample and 0.07wt%GR sample;The addition of O.Olwt%?0.07wt%GO can increase the ?',?",and tan?e of the cement-based samples,in the optimal ratio of dielectric loss of GO is 0.03wt%;5wt%?20wt%Fe3O4 content can increase the ?' ?",and tan?e of the cement-based samples,and the ratio of the dielectric loss of the Fe3O4 sample are 5wt%and 10wt%;Samples obtained by separately recombining O.Olwt%and 0.03wt%GO with 5wt%and lOwt%Fe3O4,and a composite of 0.07wt%GR and 20wt%Fe3O4 exhibited better dielectric loss.In the 0?3GHz frequency band,neither GO nor GR can significantly improve the magnetic loss performance of the cement matrix;In the frequency range of 600?800MHz,the tan?m,of the 5wt%?20wt%Fe3O4 samples are 0.11?0.67 higher than the blank sample,and 10wt%Fe3O4 sample has the best magnetic loss performance;Incorporation of non-magnetic materials GR GO don't enhance the magnetic loss capability of Fe3O4 samples.(3)Compared with the blank sample,the reflectivity of 5wt%?20wt%Fe3O4 samples are reduced in the frequency bands of 300?500MHz,700?865MHz,995?1155MHz,1340?1540MHz,1730?1840MHz and 2000?2100MHz.In the frequency range of 300?500MHz and 700?865MHz,20wt%Fe3O4 sample showed excellent absorbing properties.The absorbing properties of O.Olwt%?0.07wt%GO samples are superior to the blank sample in the bands of 210?500MHz,670?865MHz,1015?1165MHz,1340?1560MHz and 1700?3000MHz(excluding 2000MHz,2200MHz,2500MHz and 3000MHz frequencies)and the 0.07wt%GO sample has the lowest reflectivity and the greatest absorbing ability.In the remaining frequency bands,the reflectivity of the O.Olwt%to 0.07wt%GO samples all decreased by 0.20dB to 4.23dB.In the frequency range of 300?500MHz,1000?1150MHz,1340?1550MHz and the frequency of 1800MHz,after the O.Olwt%?0.07wt%GR is mixed,the reflectivity of the cement matrix decreases to some extent,of which 0.03wt%GR sample has minimum reflectance value of-11.71dB appears at the 500 MHz frequency.In the 0?3GHz frequency band.,the addition of GO has no significant effect on the reflectivity of Fe3O4 cement-based composites.After adding GR,the reflectivity of Fe3O4 samples decreased in the low frequency range of 300?500MHz,700?865MHz and 1000?1100MHz,the absorbing performances are enhanced,and after adding 0.03 wt%GR at 490 MHz,the reflectance of the 10wt%Fe3O4 sample is reduced from-7.89dB to-27.52dB.