Study On Microwave Absorbing Properties And Preparation Of Y₂Ti₂O₇ Composites

With the development of electronic communication technology,electromagnetic pollution has seriously damaged human health and equipment operation.To solve the problem of electromagnetic pollution,it is urgent to develop efficient electromagnetic wave absorbing materials.In this paper,Sr-doped Y₂Ti₂O₇,Y₂Ti₂O₇@SiO₂/C and Co Ni@C/Y₂Ti₂O₇ composites were synthesized by chemical method,and the relationship between crystal structure,micro-morphology,chemical valence change,conductivity change induced by carbon graphitization/magnetic alloy and microwave absorbing properties was analyzed in detail.The experimental results are as follows:（1）In this paper,Y_2-xSr_xTi₂O₇（x=0,0.05,0.1,0.15）solid powder was synthesized by simple sol-gel technique.XRD and Full Prof refinement results confirmed the formation of pure pyrochlore phase（space group:Fd-3m）of Y₂Ti₂O₇.With the doping of Sr²⁺ions,the lattice distortion become more serious gradually.TEM and FESEM show that the microstructure is a layered porous network structure,and rich interfaces and narrow apertures are beneficial to multi-interface polarization and electromagnetic wave transmission.The XPS results depict that there are oxygen vacancies in the samples,and less oxygen vacancies will hinder the crystal growth and enhance the interfacial polarization.Excellent microwave absorption performance put down to the Sr²⁺doping.At12.08 GHz,Y_1.9Sr_0.1Ti₂O₇ sample achieved the RL_min of-51.11 d B as the thickness of 2mm,and the EAB is 3.55 GHz.After adjusting the thickness to 2.5 mm,the optimal EAB reaches 4.63 GHz.（2）Y₂Ti₂O₇@SiO₂/C was prepared by solvothermal and precipitation methods.Amorphous carbon nucleates and grows alone,the core-shell structure of SiO₂@C failed to take shape.RAMAN test shows that C-2 sample has the best graphitization and carbon defects degree.The electromagnetic parameters can be controlled effectively by adjusting the filler content.When the annealing temperature increases from 600℃to 750℃,the graphitization and carbon atom defects increase gradually.The sample of Y₂Ti₂O₇@SiO₂/C-2 annealed at 650℃obtained the best absorbing performance.When the filler content is 50%,RL_min is-22.95 d B at 14.64 GHz,EAB reaches 6.6 GHz,and the corresponding matching thickness is 2.5 mm.By adjusting the filler content to 67%,the RL_min reached-49.36 d B at 2.8mm,while the EAB is 4.64 GHz.（3）Nano-flower-shaped Co Ni@C/Y₂Ti₂O₇ composite microwave absorber was synthesized,the terephthalic acid acted as the MOF.XRD and SEM results demonstrated that the flower-like structure consists of flaky Co Ni@C with porous structure.When the mass of Co Ni alloy accounts for 60%in the composite,the sample possesses the best microwave absorbing performance.When the thickness is 1.9 mm,EAB reaches the widest5.12 GHz,and the RL is-39.14 d B.By adjusting the thickness to 2.6 mm,the RL_min is-46.94 d B at 12.88 GHz,and the corresponding EAB is 4.06 GHz.The composite synthesized in this paper provides a reference for developing new lightweight and good-absorbing materials.