【作者】 杜敏生；

【导师】 李国栋；

【作者基本信息】 内蒙古大学 ， 凝聚态物理， 2008， 硕士

【摘要】 本文采用合金熔炼法,经星行球磨和适当退火处理后制得一种新型的吸波材料,并对其微波波段的吸波特性进行了研究。实验结果表明:经不同时间球磨、退火处理以及铁含量的不同均会对材料的吸波性能产生影响,其中退火处理后样品吸波性能明显高于未经退火处理的样品;球磨时间及铁含量只有处于最佳值时,吸收量才达到最大。同时本文还对掺杂稀土钇后材料抗氧化性的变化进行了研究。在Nd_8-xYFe_84.5+xB_6.5（x=0,0.5,1）三种不同配比的材料中,未经退火处理时,x=0.5吸波性能最好,最高吸收值达到36.843 dB,相对于x=0和x=1都有显著的提高。因此可以看出:材料并不遵守随铁元素含量增多吸波性能提高的原则,而是适量最佳。经过不同时间（t=10min、15min、20min）退火处理后,样品的吸波性能较未经退火处理的样品吸波性能均得到很大幅度提高,其中退火15分钟后样品的吸波性能达到最大,最高吸收峰为137.36dB,并且整个微波段平均吸收量比退火t=10和t=20分钟时均高出约10dB,因此,样品退火时间也存在一个最佳值。样品经不同时间（t=6h、8h、10h、12h）球磨后,当t=8h时样品在微波段的平均吸收量达到最大,此时不难看出并不是球磨时间越长颗粒越小样品吸收量越好,而是存在一个匹配值。在本文的实验条件下样品的最佳粒径为0.2微米。掺杂稀土钇的样品与未掺杂稀土钇的样品相比,在空气中放置一段时间后再对其吸波性能进行测量,总体上看掺杂稀土钇的样品吸收量减小幅度相对较小,因此样品掺杂钇后抗氧化性有了一定的增强。为了进一步探讨试样的吸波机理,我们又测试了样品的介电常数虚部、磁导率虚部及XRD图谱。由实验结果可知:未经退火处理时,磁导率虚部峰值所对应的频率与吸收峰所对应的频率非常接近,且它们的峰值随频率改变的规律相近。由此可知,此时样品主要是通过改变对磁损耗的影响来改变对微波的吸收率。退火处理后样品的吸收量图谱和介电常数图谱很相似,且它们的峰值随频率改变的规律相近,此时样品主要是通过对介电损耗的影响来改变其对微波的吸收率。由XRD图谱可知此类新型微波吸收材料,主要是通过金属颗粒被氧化物间隔开形成彼此绝缘的合金集聚体的弥散质点,按容积均匀分布的方式复合而成的,这为此种性能优异的吸波剂提供了更好的吸波通道。更多还原

【Abstract】 A novel absorption material is obtained after vacuum smelting,steelball pulverizing and proper annealing disposal.At the same time,their microwave absorption property is studied.The result shows that the absorption property of the material which pulverized at different time is different;The anneled and steelball absorption property is better than the one without anneled,and the material absorption property is best when annealed time and the content of Fe are proper.At the same time,we have also studied the anti-oxidant property change of the material when doped with yttrium.In the chemical proportion of molecular of Nd_8xYFe_84.5+xB_6.5（x=0,0.5,1）, material absorption property is best when x=0.5 without annealed,and the highest absorption value is 36.843dB,compared with x=0,1,the value increases obviously.The above indicates that the absorption property of these materials doesn’t change as the mount of Fe regularly,only doping proper a mount of Fe can improve its microwave absorption property.The absorption property of the annealed material increases obviously than the one without annealed,When annealed for 15min,the absorption property is at best,the highest absorption value is 137.36dB,and the average absorption has the height of 10dB than the one annealed for 10min or 20min.Therefore,the annealed time can get a proper value.After the sample pulvevized at different time（t=6h,8h,10h,12h）,the microwave absorption property is best when the sample pulvevized for 8h.The above indicates that the absorption property of these materials doesn’t change as the time of pulverized regularly,but there exists a matching time.The extent of weakening of the absorption property value of the sample that doped with yttrium is smaller than the one without doped with yttrium in the air after a period of time.Therefore,the anti-oxidant property is strengthened when the sample is doped with yttrium.In order to study the microwave-absorbing mechanism,imagionary part of permeability,dielectric constent and XRD spectrum of the sample are measured.The results of experiments indicate that the frequency corresponding to the peak of imagionary part of permeability is close to the one corresponding to the peak of absorption when the sample without annedled,and their changing rules of the peak of imagionary part of permeability and absorption change with frequency are similar.Therefore,the absorption property of the sample without annealed rests on imagionary part of permeability,but the frequency corresponding to the peak of imagionary of dielectric is close to the one corresponding to the peak of the absorption.And their changing rules of the peak of imagionary part of dielectric constent are similar when the sample annealed.From the XRD spectrum,we can see that the sample formed the configuration that the oxid and metal particulate distribute symmetrically according to cubage,which provides a finer absorbing way for the sample.更多还原