【作者】 刘畅；

【导师】 丁明惠；

【作者基本信息】 哈尔滨工程大学 ， 材料科学与工程， 2020， 硕士

【摘要】 钡铁氧体由于兼具磁损耗和介电损耗,故常用来做吸波剂,但由于其具有c轴各向异性,导致低磁导率和高的共振频率,因此对电磁波的吸收有限,故需对其进行改性。通常采用金属或稀土元素掺杂、材料纳米化等方式,来改善材料的电磁参数,但双稀土掺杂铁氧体的研究相对较少。鉴于此,本文通过制备聚吡咯包覆的Dy-Sm掺杂钡铁氧体复合吸波材料改善钡铁氧体的吸波性能,通过扫描（SEM）、红外（FTIR）、磁性能（VSM）、吸波性能（VNA）等测试手段对样品进行微观结构及性能表征。钡铁氧体采用溶胶凝胶及自蔓延方法制备,以十二烷基三甲基溴化铵（CTAB）为分散剂,分别以p H、柠檬酸加入量和分散剂浓度为变量,探究变量对样品形貌及性能的影响,结果表明当p H=7、n CA:n Ba²⁺=13和C_CTAB=0.01mol/L时,可获得杂质最少的片状钡铁氧体,当复合材料厚度为7.0mm时,反射损耗在14.64GHz处可达-2.15d B。为提高钡铁氧体的磁晶各向异性,在上述条件下制备稀土Dy、Sm掺杂的钡铁氧体,以掺杂量为变量,探究两种稀土元素单独掺杂时的最大掺杂量及混合掺杂时达到较大反射损耗的比例。结果表明,当n Dy³⁺:n Ba²⁺=0.20和n Sm³⁺:n Ba²⁺=0.10时掺杂量最大,无稀土铁氧化物的生成,并且稀土的掺杂可以增加样品的磁导率的虚部值,增加样品对电磁波的损耗。并且当n Dy³⁺:n Ba²⁺=0.10和n Sm³⁺:n Ba²⁺=0.050时,可获得较大反射损耗,即当复合材料厚度为7.0mm时,最大反射损耗分别为-4.54d B（16.79GHz）和-4.00d B（16.00GHz）。Dy-Sm掺杂共同掺杂可以获得最大的反射损耗,即当n Dy³⁺:n Sm³⁺=7:3时反射损耗最大,在7.0mm厚度条件下,反射损耗的最大值为-5.38d B,对应频率为15.38GHz。为提高样品的介电损耗,以获得较大的反射损耗,故在钡铁氧体表面包覆一层聚吡咯。以氯化亚铁和双氧水为氧化剂,采用原位聚合制备Ba Fe₁₂O₁₉@PPy复合吸波材料,以吡咯加入量为变量,探究获得较大反射损耗的加入量。结果表明,当m Py:m Ba Fe₁₂O₁₉=5:1时,样品的反射损耗最大,且包覆的反射损耗均大于共混时的反射损耗。其中聚吡咯包覆的Dy-Sm掺杂钡铁氧体复合吸波材料吸波性能最好,当材料厚度为7.0mm时,样品在4.93GHz处的反射损耗可达-12.46d B,在15.82GHz处的反射损耗可达-23.24d B,并且小于-10d B的吸收频宽可达4.81GHz。更多还原

【Abstract】 Barium ferrite is commonly used as a wave absorbing agent because it has both magnetic loss and dielectric loss.However,because of its c-axis anisotropy,it has low magnetic permeability and high resonance frequency which limits the absorption of electromagnetic waves.Therefore,the sample needs to be modified.Metal or rare-earth element doping,material nano-crystallization and other methods are usually used to improve the electromagnetic parameters of materials.But the research on double rare-earth doped ferrite is relatively less.Therefore,polypyrrole-coated Dy-Sm doped barium ferrite composite wave-absorbing materials are prepared in order to improve the property of absorbing electromagnetic waves of the barium ferrite.The microstructure and performance of the samples were characterized by SEM,FTIR,VSM,VNA and other testing methods.Barium ferrite is prepared by sol-gel and self-propagating method.CTAB is used as the dispersant.The p H,the amount of citric acid and the dispersant were used as the variable to investigate their effect on the morphology and performance of the samples.The results show that when p H=7,n CA:n Ba²⁺=13,and C_CTAB=0.01mol/L,the flaky barium ferrite with minimal impurities can be prepared.When the thickness of composite material is 7.0mm,the reflection loss can reach-2.15d B at 14.64GHz.In order to improve the magnetic crystal anisotropy of barium ferrite,the rare-earth Dy and Sm doped barium ferrites were prepared under the above conditions.The doping amount was used as a variable to investigate the maximum doping of the two rare earth elements of doping separately and the proportion to obtain large reflection loss when rare earth elements are co-doped.The results show that when n Dy³⁺:n Ba²⁺=0.20 and n Sm³⁺:n Ba²⁺=0.10,the doping amount is the largest and there is no formation of rare earth iron oxide.Moreover,the doping of rare earth can increase the imaginary part value of the magnetic permeability of the sample and the material’s resistance to electromagnetic waves.When n Dy³⁺:n Ba²⁺=0.10 and n Sm³⁺:n Ba²⁺=0.050,a larger reflection loss can be obtained.The maximum reflection loss is-4.54d B（16.79GHz）and-4.00d B（16.00GHz）at the thickness of 7.0mm respectively.The maximum reflection loss can be obtained by co-doping with Dy-Sm doping.Especially when n Dy³⁺:n Sm³⁺=7:3 the reflection loss can reach-5.38d B at 15.38GHz when the thickness is 7.0mm.A layer of polypyrrole was coated on the surface of barium ferrite in order to increase the dielectric loss of the sample and obtain a large reflection loss.Ba Fe₁₂O₁₉@PPy composite absorption was prepared by in-situ polymerization using ferrous chloride and hydrogen peroxide as oxidants.The addition of pyrrole was set as a variable to explore its suitable adding amount to get a large amount of reflection loss.The results show that the reflection loss of the sample is the largest and the reflection loss of the coating is greater than that of the blend when m Py:m Ba Fe₁₂O₁₉=5:1.Ba Fe₁₂O₁₉@PPy composite absorbing material has the best absorbing performance.When the thickness is 7.0mm,the reflection loss of the sample can reach-12.46d B at 4.93GHz,the reflection loss can reach-23.24d B at15.82GHz,and the absorption bandwidth of less than-10d B can reach 4.81GHz.更多还原