稀土改性钴镍铁氧体纳米粒子的制备及磁性能的研究

【作者】 王欣；

【导师】 王桂华；

【作者基本信息】 上海师范大学 ， 物理化学， 2003， 硕士

【摘要】 提高磁记录介质的密度是人们多年所追求的目标，这要求磁性材料具有高矫顽力和相应的高饱和磁化强度。本论文在对铁氧体掺入钴、镍和稀土元素等杂质离子后，研究了这些杂质离子对其磁性能的影响。并对α?FeOOH掺30%钴，制备出了较理想的针形的铁氧体粒子。本文先后用水热法、溶剂热法和溶胶凝胶法制备了掺稀土的钴、镍铁氧体纳米粒子。结果表明，对水热法制备的铁氧体粒子，杂质离子能够进入其尖晶石晶格中，并因稀土离子的半径较大，而绝大部分占据尖晶石的B位，铈元素因被氧化成为四价离子，离子半径相对较小，而主要占据A位。总体上来说，掺稀土钴铁氧体的矫顽力要比无稀土的要大。而因钴离子的特殊物理性质，钴铁氧体的矫顽力比镍铁氧体的要大。其中一掺钴和铈的铁氧体晶体，因粒子形状表现出各向异性，该样品具有很好的磁性能。溶剂热法制备的铁氧体样品中，铈离子以三价形式存在，因而主要占据尖晶石晶格的B位。溶胶凝胶法制备的样品因粒子的粒径稍高于临界尺寸而显示出相对较高的矫顽力。由于针形磁性纳米材料的形状对其矫顽力的影响最大，因此本论文在研究水解法制备针状α-Fe2O3和α?FeOOH的纳米粒子的基础上，用微波法制备了α?FeOOH，得到了轴比较好的针形α?FeOOH，并对其进行掺30%钴的实验条件的摸索，制备出了较理想的针形的铁氧体粒子，对该粒子的生长机理进行了分析。本论文还用拉曼光谱技术分别对铁表面和铁氧化物表面的有机分子的吸附情况作了分析。结果表明，当有机分子吸附在铁氧化物表面时，仍是吸附在Fe原子上，而没有和氧原子发生吸附作用。更多还原

【Abstract】 Scientists have been devoting to enhance the density of magnetic recording media for years. Magnetic materials are expected to be with high coercivity and high saturation magnetization. In this thesis, cobalt, nickel and rare earth elements are doped into ferrite and their effects on magnetic performance of ferrite are studied.Ferrite nano particles doped with cobalt, nickel and rare earth elements are prepared by hydrothermal, solvent-thermal and sol-gel method. According to the sample prepared by hydrothermal method, the doping cations can enter the spinel lattice. Rare earth cations mostly occupy position B because of their big radius. Cerium are oxidized to Ce4+, whose radius is relatively small, and Ce4+ mostly occupies position A. As a whole, the coercivity of cobalt ferrite doped with rare earth element is bigger than that of pure cobalt ferrite. The coercivity of ferrite containing cobalt is bigger than that of ferrite containing nickel because of special physical properties of cobalt. Among all the samples, one sample shows outstanding magnetic properties as the shape anisotropy of the sample plays an important role on the magnetic properties. The cerium in the sample prepared by solvent-thermal method exists as Ce3+, and it mostly occupies position B of spinel. The size of the particles prepared by sol-gel method is little bigger than critical dimension and accordingly these samples have relatively high coercivity.Acicular α-Fe2O3 and α?FeOOH nano particles are prepared by hydrolytic method and α?FeOOH with good axial ratio is prepared by microwave-induced method, then 30% cobalt is doped into this α?FeOOH sample. Ideal acicular ferrite samples have been prepared and the formation mechanism has also been studied.The adsorption behavior of organic molecules on the surface of iron and iron oxide has been studied by Raman spectroscopy. When the organic molecules adsorb on the surface of iron oxide, they only adsorb on iron element in stead of oxygen element. This means the mechanism of the effect of shape-controller on the growth process of nano-particles can be studied by Raman spectroscopy in the future.更多还原