Synthesis of crystallographically oriented olivine aggregates using colloidal processing in a strong magnetic field
Synthesis of crystallographically oriented olivine aggregates using colloidal processing in a strong magnetic field
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在强磁场中使用胶体加工合成晶体取向橄榄石聚集体
DOI：
10.1007/s00269-016-0826-5
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发表时间：
2016
影响因子：
1.4
通讯作者：
T. Hiraga
中科院分区：
文献类型：
--
作者：
S. Koizumi;T. Suzuki;Y. Sakka;K. Yabe;K.;T. Hiraga
本研究开发了一种制造技术，以获得不仅具有高密度和细晶粒尺寸而且具有晶体择优取向（CPO）的无铁和含铁（Fe:Mg = 1:9）橄榄石聚集体。将磁场 (≤12 T) 应用于分散在溶剂中的合成细粒 (~120 nm) 橄榄石颗粒。由于橄榄石的磁各向异性，预计颗粒的某些晶轴相对于磁方向排列。在排出溶剂的过程中，分散的颗粒逐渐固结在覆盖有固液分离过滤器的多孔氧化铝模具上。然后将所得的对齐固结骨料进行等静压和真空烧结。我们发现（1）制备完全反应的橄榄石颗粒，具有较小的聚结倾向； (2)制备颗粒高度分散的悬浮液； (3)施加一定强度的磁场对于获得良好烧结和良好排列的骨料至关重要。分别用单轴排列的 a 轴和 c 轴成功合成了高密度（即 <1 vol% 孔隙率）和细粒度（~1 μm）无铁和含铁橄榄石聚集体。通过在磁场中旋转悬浮液来单轴排列磁化难轴和三轴排列含铁橄榄石的尝试成功地获得了弱发育的CPO聚集体。
This study develops a fabrication technique to obtain Fe-free and Fe-bearing (Fe:Mg = 1:9) olivine aggregates not only with high density and fine grain size but with crystallographic preferred orientation (CPO). A magnetic field (≤12 T) is applied to synthetic, fine-grained (~120 nm), olivine particles dispersed in solvent. The alignment of certain crystallographic axes of the particles with respect to a magnetic direction is anticipated due to magnetic anisotropy of olivine. The dispersed particles are gradually consolidated on a porous alumina mold covered with a solid–liquid separation filter during drainage of the solvent. The resultant aligned consolidated aggregate is then isostatically pressed and vacuum sintered. We find that (1) preparation of fully reacted olivine particles, with less propensity to coalesce; (2) preparation of a suspension with highly dispersed particles; and (3) application of a certain strength of the magnetic field are essential to obtain well-sintered and well-aligned aggregates. High density (i.e., <1 vol% porosity) and fine grain size (~1 μm) Fe-free and Fe-bearing olivine aggregates were successfully synthesized with uniaxially aligneda- andc-axes, respectively. Attempts to uniaxially align the magnetization hard axis and to triaxially align Fe-bearing olivine by rotating the suspension in the magnetic field succeeded in obtaining weakly developed CPO aggregates.