納米級磁鐵和鐵氧體磁鐵復合材料
3.1.1 機械化學合金和煅燒
與混合氧化物固態(tài)反應相比，機械化學活化可以更好地混合起始材料[13,78]。同時，將起始材料研磨至100 nm左右，可以在較低的煅燒溫度下改善相的形成，減少顆粒的生長。亞微米六方體顆粒是制備高矯頑力六方體[39]的重要前提。以Fe2O3 (Sigma Aldrich, 99%純度)和SrCO3 (Sigma Aldrich, 99%純度)為原料制備SrFe12O19。采用德國Riedel-de Haen公司生產的al2o3(純度99.9%)代替六方鋁。工業(yè)上，如第2.3節(jié)所述，一種亞化學計量稱重比為SrO: Fe2O3 / 1: 5.5 - 5.9[6,53]。在此工作中，由于采用了退火粉末工藝路線，根據(jù)公式2.10，化學計量制得的粉末可以取得更好的效果。使用VMA-GETZMANN公司的臥式珠(球)磨機DISPERMAT SL對初始重量為600g的粉末進行研磨，在不同情況下都會發(fā)生機械化學活化。在這種情況下，粉末與異丙醇(研磨介質)的質量比為1:2。采用直徑為1mm的氧化鋯(ZrO2)研磨珠共0.75千克配合使用，球磨機內含的轉子材料為二氧化鋯(ZrO2)。不能用EDX測試來量化研磨珠和轉子的磨損情況。機械化學活化發(fā)生在超過6 小時且轉速為5500 rpm的研磨(最高溫度為34°c)。使用的DISPERMAT系統(tǒng)和基本結構如下圖所示。
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.
