纳米级磁铁和铁氧体磁铁复合材料
3.1.1 机械化学合金和煅烧
与混合氧化物固态反应相比，机械化学活化可以更好地混合起始材料[13,78]。同时，将起始材料研磨至100 nm左右，可以在较低的煅烧温度下改善相的形成，减少颗粒的生长。亚微米六方体颗粒是制备高矫顽力六方体[39]的重要前提。以Fe2O3 (Sigma Aldrich, 99%纯度)和SrCO3 (Sigma Aldrich, 99%纯度)为原料制备SrFe12O19。采用德国Riedel-de Haen公司生产的al2o3(纯度99.9%)代替六方铝。工业上，如第2.3节所述，一种亚化学计量称重比为SrO: Fe2O3 / 1: 5.5 - 5.9[6,53]。在此工作中，由于采用了退火粉末工艺路线，根据公式2.10，化学计量制得的粉末可以取得更好的效果。使用VMA-GETZMANN公司的卧式珠(球)磨机DISPERMAT SL对初始重量为600g的粉末进行研磨，在不同情况下都会发生机械化学活化。在这种情况下，粉末与异丙醇(研磨介质)的质量比为1:2。采用直径为1mm的氧化锆(ZrO2)研磨珠共0.75千克配合使用，球磨机内含的转子材料为二氧化锆(ZrO2)。不能用EDX测试来量化研磨珠和转子的磨损情况。机械化学活化发生在超过6 小时且转速为5500 rpm的研磨(最高温度为34°c)。使用的DISPERMAT系统和基本结构如下图所示。
Nanoskalige Magnete und Magnetkomposite auf Ferritbasis
3.1.1 Mechanochemical alloy and calcination
The mechanochemical activation serves to better mix the starting materials compared to the mixed oxide solid state reaction [13, 78]. At the same time, the starting materials are ground to a few 100 nm, which should allow for improved phase formation at lower calcination temperatures and reduced particle growth. Submicrometer hexaferrite particles are an important prerequisite for highly coercive hexaferrites [39]. As starting materials of SrFe12O19, Fe2O3 (Sigma Aldrich, 99% purity) and SrCO3 (Sigma Aldrich, 99% purity) are used. Al 2 O 3 from Riedel-de Haen GmbH (99.9% purity) is used for Al-substituted hexaferrites. Industrially, as described in Section 2.3, a sub-stoichiometric weighing in the ratio SrO: Fe2O3 of 1: 5.5 - 5.9 [6, 53]. In the present work, due to the used powder process route through annealing, better results could be achieved for the stoichiometrically produced powder according to equation 2.10. The mechanochemical activation takes place in each case for a 600 g initial weight of the starting powder in a DISPERMATR type attritor SL of the company VMA-GETZMANN. In this case, the mass ratio of powder to isopropanol (grinding medium) is 1: 2. The grinding balls used are 0.75 kg of ZrO 2 balls with a diameter of 1 mm. The used rotor is also made of ZrO2. A significant abrasion of the grinding balls and the rotor material could not be quantified by EDX measurements. The mechanochemical activation takes place at a rotor speed of 5500 rpm over a period of 6 h (maximum temperature about 34 ° C.). The basic structure and the system used are shown in FIG.
