納(nà)米級磁(cí)鐵和(hé)鐵(tiě)氧體磁鐵復(fù)合(hé)材(cái)料(liào)

3.1.1 機械(xiè)化(huà)學合金(jīn)和(hé)煅燒

與(yǔ)混(hùn)合氧化物固態反(fǎn)應相(xiāng)比(bǐ)，機(jī)械(xiè)化學活化可以(yǐ)更(gēng)好地混合起始材(cái)料[13,78]。同時，將(jiāng)起(qǐ)始(shǐ)材料(liào)研磨(mó)至100 nm左(zuǒ)右，可以(yǐ)在較(jiào)低(dī)的(dí)煅燒溫度下改善相的(dí)形成(chéng)，減(jiǎn)少(shǎo)顆粒的生長。亞微(wēi)米六(liù)方體(tǐ)顆粒(lì)是製(zhì)備高矯頑力(lì)六(liù)方體[39]的重(zhòng)要(yào)前提(tí)。以(yǐ)Fe2O3 (Sigma Aldrich, 99%純度)和SrCO3 (Sigma Aldrich, 99%純(chún)度)為原料製備SrFe12O19。采(cǎi)用(yòng)德國Riedel-de Haen公司生產的al2o3(純度99.9%)代(dài)替六方(fāng)鋁。工業上，如第(dì)2.3節所述(shù)，一(yī)種亞化學(xué)計量(liáng)稱重比(bǐ)為(wéi)SrO: Fe2O3 / 1: 5.5 - 5.9[6,53]。在此工作中，由於(yú)采用了(liǎo)退(tuì)火粉(fěn)末工藝路(lù)綫，根據公式(shì)2.10，化(huà)學(xué)計(jì)量(liáng)製得的(dí)粉(fěn)末可以取(qǔ)得(dé)更(gēng)好(hǎo)的效果。使用(yòng)VMA-GETZMANN公(gōng)司(sī)的臥(wò)式(shì)珠(球)磨(mó)機(jī)DISPERMAT SL對(duì)初始重(zhòng)量為(wéi)600g的粉末進(jìn)行(háng)研磨(mó)，在(zài)不同(tóng)情(qíng)況下都會發(fā)生機械化(huà)學活化(huà)。在(zài)這種(zhǒng)情(qíng)況下(xià)，粉(fěn)末與異丙(bǐng)醇(chún)(研磨(mó)介質)的(dí)質(zhì)量比(bǐ)為1:2。采用直(zhí)徑(jìng)為(wéi)1mm的氧(yǎng)化鋯(ZrO2)研磨珠(zhū)共0.75千克配合使用，球磨(mó)機(jī)內含(hán)的轉子(zǐ)材料(liào)為(wéi)二氧(yǎng)化(huà)鋯(gào)(ZrO2)。不能(néng)用(yòng)EDX測試來(lái)量化研(yán)磨(mó)珠(zhū)和轉(zhuǎn)子(zǐ)的(dí)磨損情(qíng)況(kuàng)。機械(xiè)化(huà)學活化(huà)發生(shēng)在(zài)超過6 小(xiǎo)時且轉(zhuǎn)速為5500 rpm的研(yán)磨(最高(gāo)溫(wēn)度(dù)為(wéi)34°c)。使(shǐ)用的DISPERMAT係統(tǒng)和基本結構如(rú)下圖(tú)所示(shì)。

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.