Preparation And Properties Of Ni-Doped Iron-based Rare Earth Alloys

With the rapid development of science and technology,the use of electronic products is becoming more and more common,and radar communication technology is becoming more and more developed.The resulting electromagnetic pollution has brought great harm to people’s daily lives.Absorbing materials play an important role in the military and civilian fields.Traditional magnetic materials are limited by the Snoek limit,the properties of materials in high frequency microwave fields are only related to the saturation magnetization of the materials,so traditional magnetic materials cannot meet the application requirements of absorbing materials.In the 1950s,Philips laboratories discovered that planar anisotropic magnetic materials can break the Snoek limit.The high frequency intrinsic(₄)-1)1)of the material is greatly improved,thereby obtaining a microwave magnetic material applicable to high frequency.Based on the above theoretical guidance,in this thesis,Y₂(Fe_1-xNi_x)₁₇N_3-δ,Dy₂(Fe_1-xNi_x)₁₇N_3-δand Sm₂(Fe_1-xNi_x)₁₄B with planar anisotropy were prepared by arc melting and vacuum stripping.The rare earth-3d transition group intermetallic compound was successfully prepared by ball milling and then nitriding,and the effect of atomic doping on the static and high frequency magnetic properties of the sample was studied.The interface reflection model explains the formation mechanism of high-frequency magnetic and microwave absorption properties of composite materials.The main conclusions are as follows:Y₂(Fe_1-xN_ix)₁₇N_3-δmagnetic powders,（1）Y₂(Fe_1-xNi_x)₁₇ prepared at the maximum speed by the melt rapid quenching method has a Th2Ni17 structure.For the sample with a strip,there is noα-Fe;the sample is ball-milled under fixed ball milling conditions.,All show flaky particles,but as the amount of Ni doped increases,the flaky samples become more and more uneven,and the thickness of the flakes also increases,which will affect the high-frequency use of the material.（2）As the amount of Ni added increases.The saturation magnetization of the sample is decreasing.Due to the introduction of nickel atoms with negative magnetic crystal anisotropy,the magnetic crystal anisotropy of the material decreases,and the initial magnetic permeability of the material increases.（3）For the Y₂Fe₁₇N₃ball milled sample/polyurethane（20vol%）composite material,the calculation of the wave absorption properties of the sample found that the sample’s perfect match point was indeed3.72GHz,the best match thickness was 3.06mm,and the reflection loss reached-57.7dB.It shows that Y₂Fe₁₇N₃ can be used as a good absorbent.Dy₂(Fe_1-xNi_x)₁₇N_3-δmagnetic powders,（1）Dy₂(Fe_1-xNi_x)₁₇ prepared at the maximum speed by the melt rapid quenching method has a Th2Ni17 structure.For the sample with a strip,noα-Fe appears;the sample is ball-milled under fixed ball milling conditions,All show flaky particles,but as the amount of Ni doped increases,the flaky samples become more and more uneven,and the thickness of the flakes also increases,which will affect the high-frequency use of the material.With the increase of Ni content.The saturation magnetization of the sample is decreasing.（2）The magnetic permeability of Dy₂(Fe_1-xNi_x)₁₇N_3-δ/polyurethane composite（vol50%）is not very high,only 3.The doping of Ni atoms did not greatly improve the relative complex permeability of Dy₂(Fe_1-xNi_x)₁₇N_3-δSm₂Fe₁₄B magnetic powders,（1）The prepared Sm₂(Fe_1-xNi_x)₁₄B（x=0-0.3）are all tetragonal Sm₂Fe₁₄B phases.With the increase of the amount of Ni atoms,the saturation magnetization of the powders decrease,and the coercivity increases before it decreases（2）The microwave permeability of the Sm₂(Fe_1-xNi_x)₁₄B ball milled sample/polyurethane composite（50vol%）increases first and then decreases as the amount of Ni doped increases.The real part of the permeability decreases slowly at 0.1-10GHz.The imaginary part of the magnetic permeability shows a double-peak structure,but the domain wall resonance peak is not obvious,and its natural resonance peak is around 12GHz.（3）The prepared Sm₂(Fe_1-xNi_x)₁₄B-α-Fe dual-phase alloy,the main phase of which is the tetragonal Sm₂Fe₁₄B phase.As the amount of Fe increases during smelting,the Fe peak in the XRD pattern becomes more and more obvious..The saturation magnetization of the alloy does not change significantly when theα-Fe phase is small.When theα-Fe phase decreases from 15%,the saturation magnetization increases significantly.（4）The microwave permeability of the Sm₂Fe₁₄B-α-Fe dual-phase alloy ball-milled sample/polyurethane composite（60vol%）is highest when theα-Fe phase is the main phase,and its initial magnetic permeability is about 10.8.It drops sharply within 0.1-18GHz,and the natural resonance peak is 7GHz.When Sm₂Fe₁₄B is the main phase,the magnetic permeability of the sample is about 3,and the natural resonance peak is around 7GHz.