低维M型钡铁氧体及其复合物的制备,磁和微波吸收性能研究

Microwave absorption materials play an important role in both civil and military fields as a result of the serious electromagnetic interference pollution arising from mobile phones, radar systems and various electromagnetic stealth military equipments. Microwave absorption materials have attracted a growing and widespread attention in the past decades due to their vast application prospect and huge market potential. However, nowadays most of studies on microwave absorption materials were focused on millimicron and submicron ferrites.There are few previous reports about low-dimensional M-type ferrites and their composites.In this project, we choose low-dimensional M-type ferrites and their composites as our objectives as well as investigate their magnetic and microwave absorption properties systematically. Chemical coprecipitation method and hydrothermal method will be used to prepare low-dimensional M-type ferrites.Microstructural, magnetic and microwave absorption properties were systematically investigated by XRD, FESEM, M(T), M(H) and RL(f)curves.The influence of different nanostructured material and prepation method on the composition, morphology, magnetic and microwave absorption properties of low-dimensional M-type ferrites will be studied. Encapsulating the magnetic nanostructures into light dielectric nonmagnetic materials, i.e.MgO, ZnO, SiO2, SrTiO3 etc., not only can efficiently enhance microwave absorption properties but also overcome the degradation of microwave absorption properties caused by the eddy current in the high-frequency region. We will try to combine experiment and theory in order to understand low-dimensional M-type ferrite nanocomposites completely. We expect we can explore two or more excellent microwave absorption nanocomposites, which will lay experimental and theoretical foundation for the practical applications of low-dimensional M-type ferrite composites on a large scale.

由于微波吸收材料在民用防电磁辐射产品和军事装备电磁"隐身"技术的发展中扮演着十分重要的角色,有着广阔的应用前景和巨大的潜在市场，微波吸收材料在材料领域已得到了广泛关注。目前关于磁性吸波材料的研究和应用主要集中在微米和亚微米的铁氧体方面，有关低维M型铁氧体及其复合物的研究鲜有报道。本项目拟采用化学共沉和水热法合成多种低维结构M型铁氧体吸波剂，研究不同纳米结构和制备方法对材料的化学组分、微结构、形貌、磁以及微波吸收性能的影响；再在吸波剂表面包裹一层轻质介电材料，通过微结构和微波吸收和磁性能等测量研究不同种类复合吸波材料及其不同比例、颗粒尺寸对复合材料磁和微波吸收性能的影响和变化规律，并建立材料结构、磁、吸波性能相互作用的微观机制。从而探索出具有性能较优越的纳米复合微波吸收材料，为其实际应用奠定理论和实验基础。

六角晶系铁氧体由于其丰富的原材料和优异的磁性能，被广泛应用于微波器件和微波吸收等领域。本项目以M型六角铁氧体(BaFe12O19为研究对象，较系统深入地研究了母体以及掺杂化合物的制备与磁性相关的性能和内在物理机制，取得的主要研究结果如下：.(1)M型六角铁氧体BaFe12O19以及Fe位掺杂体系的低温的合成方法及其磁性研究。结果表明，采用溶剂热法在较低晶化温度下合成了单相的M型铁氧体；Ni-Ti共掺Fe位能够明显降低体系的矫顽力，同时又不会恶化饱和磁化强度；La-Co共掺Fe位，在低掺时，矫顽力出现了最大值，但饱和磁化强度是单调减少的。这一结果对M型铁氧体在微波吸收和高密度磁存储应用方面具有实际意义。.(2)以聚乙烯吡咯烷酮(PVP)和金属盐为原料用静电纺丝法制得Sr0.8La0.2Fe11.8Co0.2O19纳米纤维，在经过热处理后得到了M型铁氧体纳米纤维的样品。通过对样品的XRD图谱的分析我们得知样品是六角晶系M型Sr铁氧体；通过形貌分析可知用静电纺丝制备的 M型铁氧体纯度较高，样品颗粒分布比较均匀，也可以较清楚地分辨出晶界，直径大约分布在0.1~0.3 μ m之间；由红外可知样品随着温度升高透射峰逐渐向低波数移动；分析电磁参量可知，镧钴掺杂的M型铁氧体具有良好的微波吸收性能。.(3)为了降低羰基铁粉的介电常数值以及涡流效应，以提高微波吸收性能，采用了简单的水热合成技术，通过控制反应体系中的pH值（pH=12, 13，14），合成了核壳结构CIP/Fe3O4复合材料。对pH值为13的产物（CIP/Fe3O4，pH=13），在宽频区获得了强的微波吸收性能。当其匹配厚度为2.0mm时，反射损耗低于-10dB的频率范围从8.7GHz一直到15.0 GHz，最大反射损耗峰达到−38.1dB。吸波性能远远超过了CIP和Fe3O4单一组分吸波剂所具有的吸波性能。.(4)采用简单的溶剂热方法，合成了轻质的空心微珠/Fe3O4复合材料（Hollow glass microspheres/Fe3O4，HGMs/Fe3O4）。所得复合材料呈现优异的吸波性能。当样品厚度超过1.5mm时，出现强的吸收峰。对于反应2h的样品，在频率6.0-11.8GHz频率范围内反射损耗值低于-20dB。当样品厚度为3.0mm时，在7.3GHz处，最大反射损耗峰达到-36.2dB。