【作者】 任平；

【导师】 官建国；

【作者基本信息】 武汉理工大学 ， 材料学， 2004， 硕士

【摘要】 铁氧体是一种传统的优良的吸收剂，具有吸收强、工艺简单、价格便宜等特点，但同时存在密度大、吸收频带不够宽等问题。空心结构的铁氧体是对传统实心铁氧体的改造，不仅密度小，还具有特殊的电、磁功能，有可能使电磁波在其空腔中反复振荡吸收，成为电磁波的“黑洞”，从而增加材料的吸波能力，同时可通过调节核壳粒子的内外径来调控电磁参数。空心结构的吸波材料是吸波材料的研究趋势。 本文较为系统地概述了六角晶系铁氧体吸收剂的结构和基本特性；介绍了当前铁氧体超微粉末及空心微球的主要制备方法；用氧乙炔火焰粉末喷雾技术与等离子火焰溶液喷雾技术制备了六角晶系铁氧体空心微球，对其结构和性能进行了一系列的探讨工作。重点研究了热处理工艺（温度、时间、升温速率）对其相结构、微观形貌和微波性能的影响。 用氧乙炔火焰粉末喷雾热解技术制备了六角晶系平面W型BaCo₂Fe₁₆O₂₇和M型BaFe₁₂O₁₉铁氧体空心微球。实验结果表明：该方法制备的空心微球粒径分布较广，主要在4～20 μm之间，平均密度在2.50g／cm³左右。热处理过程表明，M型铁氧体直接由金属氧化物反应形成，未经历尖晶石中间相；W型铁氧体形成由金属氧化物到M相过渡相最终向W相的转变；当升温速率为5℃／min，温度在900℃，保温3小时和1200℃保温4小时，就分别形成单相M相和W相铁氧体；随着热处理温度的升高和保温时间的延长，衍射峰变尖锐，结晶更完整，空心微球的饱和磁化强度增大，矫顽力减小。随热处理温度的升高，W型铁氧体空心微球的介电常数降低；磁导率实部先增加后减少，虚部增加并出现明显的共振峰；M型铁氧体空心微球的介电常数增加，磁导率实部增加，虚部变化不明显。 用等离子火焰悬浮液喷雾热解技术制备了六角晶系W型BaCo₂Fe₁₆O₂₇铁氧体空心微球。实验结果表明：粒度分布较均匀，基本在2～10 μm之间，平均密度为1.50g／cm³左右；当升温速率为1.5℃／min、温度为1250℃，形成单相W相铁氧体空心微球，此时其饱和磁化强度为58emu／g，矫顽力为45Oe。更多还原

【Abstract】 Ferrites are conventional wave absorbing materials, which have such advantages as strong absorption, simple techniques and cheap raw materials, but they are quite heavy and have difficulties in increasing the permeability in GHz region. Hollow ferrites particles are the alternative to conventional solid ferrites particles, which have lower density, larger specific surface area and stability. Moreover, it is expected electromagnetic wave can be reflected and absorbed again and again in the cavum of hollow particles which become its black hole. In addition, their electromagnetic parameters can be adjusted in a certain range by changing the thickness of the shell and the diameter of hollow microspheres, and the ability of absorbing microwave can be expected to improve. Wave absorbing materials of hollow structure are the research trend.In this thesis, the structure and basic characteristic of hexagonal ferrite absorbent were summarized, and popular methods to prepare ultrafine ferrite particles and hollow microspheres were introduced. Hexagonal ferrite hollow microspheres were prepared by flame powders spraying technique and flame suspending solution spraying technique. The phase component, microstructure and electromagnetic properties of the synthesized hollow microspheres were studied as functions of heat-treated techniques (like temperature, time, the speed of heating) in detail.W-type BaCo2Fe16O27 and M-type BaFe12O19 hexagonal ferrite hollow microspheres were fabricated by flame powders spraying technique using oxygen and acetylene as fuel. The method resulted in abroad particle size distribution (mainly from 4 m to 20 m ), and the density was about 2.50 g/cm3. The process of heat-treatment showed M-type ferrite was straightly formed from metal oxide without the transition of spinel phase. The formation process of W-type ferrite underwent from oxide of metal, the M-type transition phase to final W-phase. When the heating rate was 5 ℃/min, at 900 ℃ for 3 hrs and 1200 ℃ for 4 hrs, pure M-type and W-type ferrites were formed in airrespectively. With heat treatment temperature increasing, crystal structure was more intact, the saturation magnetization increased and the coercive force decreased. With heat treatment temperature increasing, the complex permittivity of W-type ferrite hollow microspheres decreased; ’ firstly increased and then decreased, increased and there was an obvious resonance peak; the complex permittivity ?of M-type ferrite hollow microspheres increased; ’ increased, " was basically unchangeable.W-type BaCo2Fe16O27 hexagonal ferrite hollow microspheres were also fabricated by flame suspending solution spraying technique. The results showed hollow microspheres had a narrow particle size distribution (mainly from 2 m to 10 m ), and the density was about 1.50 g/cm3. When the speed of heating was 1.5 /min and heat-treatment temperature was 1250 , pure W-phase ferrite was formed. In this condition, the saturation magnetization was 58 emu/g and the coercive force was 45 Oe.更多还原