Study On Structure And Absorbing Properties Of Dy-Co Alloy

In order to deal with the increasingly serious electromagnetic pollution phenomenon,the research of absorbing materials is very important.In this paper,the alloy micro-powder is prepared by arc melting,uniform heat treatment and high-energy ball milling,and solid paraffin is a composite wave absorbing material pressed by adhesive.The effects of doping of non-magnetic metals Mn,magnetic metals Fe,Ni and light（La,Ce）and heavy（Tb,Ho）rare earth on morphology,phase composition,electromagnetic parameters,magnetic properties and absorbing properties of Dy-Co alloy system were investigated.Dy₂Co_17-xMn_x is mainly flake after high-energy ball milling.Because Mn is a non-magnetic element,the doping of Mn leads to a gradual decrease in saturation magnetization（Ms）and an increase in coercivity（Hc）at first and then a decrease.Improved dielectric constant and permeability,and adjust impedance matching performance.The effective absorption bandwidth（EAB）of sample Dy₂Co_16.9Mn_0.1 is 3.2 GHz when the thickness is 1.4mm,which was then compounded with carbonyl iron powder to improve EAB.In the thickness range of 1.2～2.4 mm,it almost covers the whole S,C and X bands and part of Ku band,achieving efficient absorption performance in low and middle frequency bands with thinner thickness and reducing costs.The main phase of Dy₂Co_17-xFe_x and Dy₂Co_17-xNi_x alloy powders does not change with the increase of Fe and Ni doping amount,and still retains Dy₂Co₁₇ phase.As the atomic radius of Fe is larger than that of Co,the lattice distortion and crystal plane spacing increase,and the increase of electrical conductivity leads to the significant enhancement of the imaginary part of dielectric constant（ε"）.The sample Dy₂Co_16.9Fe_0.1 has the best performance when the thickness is 1.4 mm,and the minimum reflection loss(RL_min)at 11.12GHz is-37.5 d B,EAB=1.92 GHz（10.24～12.16 GHz）.Appropriate proportion of Si O₂ can effectively adjust the impedance matching performance,in the thinner thickness range of the simulation,EAB includes part of the C-band,Ku-band and the entire X-band,achieving effective combination of improved bandwidth;The doping of Ni leads to the decrease of Ms,andε"has a significant increase,the permeability has no significant change.When the matching thickness of Dy₂Co_16.5Ni_0.5 is 2.0 mm,at 7.12 GHz,RL_min=-44.50 d B,EAB is 1.52GHz,and the corresponding impedance matching Z is 0.99.The performance of Dy₂Co_16.5Ni_0.5 is good in C、X（4～8 GHz、8～12 GHz）band.XRD results show that the doping of light（La,Ce）and heavy（Tb,Ho）rare earths does not change the crystal phase of the alloy,and the morphology after high-energy ball milling is mainly flake.When doping amount x=0.4 in Dy_2-xCo₁₇La_x,when the matching thickness is 1.0 mm,the best EAB=2.56 GHz（11.2～13.76 GHz）,RL_min=-25 d B.When the thickness range is 1.4～1.6 mm,the absorption rate of all samples reaches 99%,showing excellent absorption performance.With the increase of doping amount,the effective absorption band of bandwidth tends to move to low frequency band.Therefore,we should choose appropriate thickness and use absorbing material in appropriate frequency band;When the thickness of Dy_2-xCo₁₇Ce_x alloy powder is 1.6 mm,the best absorption rate of all samples is more than99%,and the absorption performance is good in X-band;With the increase of Tb doping amount,the reflection loss peak of Dy_2-xCo₁₇Tb_x shifts to low frequency,Dy_1.8Co₁₇Tb_0.2 at the corresponding peak Z=1.01,the attenuation constant is greatly improved from the original 133.55 to 374.38,RL_min=-40.90 d B,EAB=1.6 GHz（9.28～10.88 GHz）;The EAB values of Dy_2-xCo₁₇Ho_xwere 0.8,2.08,1.92 and 2.24 GHz when the thickness of Dy_2-xCo₁₇Ho_x was 1.6 mm.Dy_1.5Co₁₇Ho_0.5 has the best Z value of 1.01 and a good attenuation constant of among the four samples,and the best performance is obtained under the synergistic effect of attenuation capability and impedance matching performance.