【作者】 张义桃；

【导师】 田旭；

【作者基本信息】 武汉理工大学 ， 凝聚态物理， 2008， 硕士

【摘要】 吸波材料无论是在民用还是军事上都有着非常重要的研究与实用价值,而铁氧体吸波材料具有吸收强、吸收频带宽、成本低廉、制备工艺简单等优点,成为吸波材料研究领域的热门课题。在吸波材料的设计合成中,人们多注意物质的化学组分和合成方法等,制备吸波性能良好的铁氧体。利用高压这一极端条件设计制备吸波材料却尚未见报道。本文致力于研究压力对材料吸波性能的影响,以期制备高性能铁氧体吸波材料。研究结果表明,高压处理可以明显改善四氧化三铁的微波电磁参数,提高其反射损耗,增大吸收带宽,得到了比较理想的结果。同时,用陶瓷法制备钡铁氧体,测试其反射损耗,这样化学和高压处理两种方法在一定的程度上形成了比较。本文的研究工作为吸波材料的设计合成提供新的研究思路和方法,为铁氧体吸波材料的进一步发展注入了新的活力。本文研究的主要内容以及得到的结论有以下方面:（1）用陶瓷法制备了M型钡铁氧体,并对其进行了X射线衍射（XRD）分析和扫描电镜（SEM）的表征,结果表明:在1300℃下煅烧3h空冷后经研磨得到均匀的铁氧体粉末,经XRD分析为较纯单相钡铁氧体,从SEM可以看出钡铁氧体的形貌主要呈六角形分布,晶粒大小在1.4μm～3.2μm之间;（2）用聚氨酯软质泡沫为基材,分别充填铁氧体,碳粉以及他们的混合体,制备了平板,通过弓形反射法测量聚氨酯软质泡沫复合材料的微波吸收性能,测试频段为4～8GHz。结果表明:充填5g铁氧体和15g炭黑的平板具有良好的吸波效果,反射系数约为-7dB。（3）对Fe₃O₄粉末进行2GPa、4GPa、6GPa的高压处理,经XRD分析并未出现新相,但是衍射峰存在宽化的现象,SEM显示出粒径有所减小;（4）用矢量网络分析仪,对高压处理后的Fe₃O₄进行电磁参数的测量。结果表明:高压处理能有效调整Fe₃O₄的微波电磁参数,与常压相比,有较大的利好变化。磁导率的实部μ′增大和介电常数的实部ε′减小,这有利于实现阻抗匹配;磁导率的虚部μ′和介电常数的虚部ε″都有较大增加,这有利于提高能量衰减,满足吸波材料的两大条件。（5）经模拟得到2mm厚度下不同压力处理后的Fe₃O₄粉末在2～18GHz范围内的反射损耗曲线,反射损耗都比常压下要小,且峰值变大,带宽变宽,特别是处理压力为2GPa时的Fe₃O₄微波吸收性能最好,反射损耗峰值达-24dB,反射损耗小于-8dB的带宽达到7.5GHz。结果说明高压处理有利于制备轻、薄、宽的铁氧体吸波材料。更多还原

【Abstract】 Absorbing materials has a very important practical value in civilian and military, the Ferrite-absorbing materials has the advantages of strong absorbability,matching impedance,good absorption frequency bandwidth,low cost,simple preparation,so it becomes the hot topic.In the design and synthesis of absorbing materials,people pay more attention to the chemical composition and methods of synthesis of substances, then made the good performance of ferrite.Althought using the extreme condition high pressure to design absorbing material has not been reported.This paper is dedicated to research high pressure treatment of absorbing properties,hope to prepare high-performance ferrite absorbing materials.The results show that: high-pressure could significantly improved the microwave electromagnetic parameters and enhanced its reflection loss,increased absorption bandwidth of ferrite, had been received satisfactory results.At the same time,also used Chemistry method -ceramic technique to make the ferrites,this two methods could be compared in certain basic.This paper provided a new ideas and research methods to research work of absorbing materials,and injected new vitality to ferrite absorbing materials for the further development.In this paper,it mainly obtained the conclusions as the following aspect:（1）Samples of M-type barium ferrites（BaM）were synthesized using the ceramic technique,phase identifications were performed by the X-ray power diffraction （XRD）the microstructure features were observed by scanning electron microscope （SEM）,the results showed that:calcined inair at 1300℃for 3h,after the attrition,it obtained the uniformity ferrites.All samples were identified to be single phase with only M-type hexagonal barium ferrites,no other phases were detected.BaM particles are approximating hexagonal-shaped and the average grain size was about 1.4-3.2μm.（2）Carbon black,barium ferrite and the mixture of them were filled in the soft foamed polyurethane.The microwave absorption properties were measured by the arch reflection method from 4 to 8GHz using an HP 8320B vector network analyzer （VNA）.The experiment indicated:filled with 5g ferrites and 15g carbon black plate has better absorbability,the reflectance approximately was-7dB.（3）Carried on 2GPa,4GPa,the 6GPa processing to Fe₃O₄,using the XRD and SEM, they had not appeared the new phase,but diffraction peak was widened,the particle size obviously had reducesd.（4）With the vector network analyzer to measure the electromagnetism parameter of the sample,the results showed that:high pressure can be good for adjusting microwave electromagnetic parameter,compared to normal pressure,effect of high pressure,μ′increased with increasing frequency,ε′decreased,it was propitious to realize the impedance matching;μ″andε″both increased,it was propitious to enhance energy attenuation.（5）The reflection loss of one-layer absorber was numerically calculated from 2 to 18GHz under 2mm thickness.The reflection loss were all decreased,peak value and bandwidth were both increased,especially when the pressure was 2GPa,the bandwidth could reached 7.5GHz for reflcting rate below-8dB,the biggest reflection loss was-24dB.All this proved that high pressure can be good for preparing ferrite absorbing material with properties of light,thin and width.更多还原