磁场中制备的硅水凝胶结构各向异性的再认识
Reconsideration on structural anisotropy of silica hydrogels prepared in magnetic field
摘要：
在以前的论文[A。Mori，T. Kaito，H.古川，脱线。Lett. 62（2008）3459-3461]，我们对在磁场中制备的Pb（II）掺杂的二氧化硅水凝胶进行双折射测量（B）。对于5 T样品，我们观察到光轴沿B方向的负双折射。当时，假设二氧化硅具有正的固有双折射，我们推测在双折射凝胶中，凝胶网络垂直于B延伸。本文的目的是在前人和最近的结果的基础上重新考虑这一推测[T。Kaito，S.- I. Yanagiya，A. Mori，M.库鲁马达角Kaito，T. Inoue，J. Cryst. Growth 289（2006）275-277; T. Kaito，A.莫里角Kaito，J. Chem. Chem. Eng.，9（2015）61-66]。在前者中，硅胶被用作PbBr_2晶体生长的介质，并且获得了长轴平行于B的定向微晶阵列。在后者中，Pb（II）纳米晶体形成在二氧化硅干凝胶通过电子辐照。PbBr_2微晶的短轴和Pb（II）微晶的直径均为几十纳米。该尺寸必须是受磁场影响而伸长的凝胶网络中的孔的短轴的尺寸。由于PbBr 2微晶沿磁场方向被拉长，我们得出结论：Pb（II）掺杂的硅胶网络沿磁场方向排列。
英文摘要：
In a previous paper [A. Mori, T. Kaito, H. Furukawa, Mater. Lett. 62 (2008) 3459-3461], we carried out birefringence measurements of Pb(II)-doped silica hydrogels prepared in a magnetic field (B). For a 5T sample, we observed a negative birefringence with the optic axis along B. At that time, providing a positive intrinsic birefringence of silica, we speculated that in the birefringent gels the gel network extended perpendicular to B. The purpose of this paper is to reconsider this speculation on the basis of previous and recent results [T. Kaito, S.-i. Yanagiya, A. Mori, M. Kurumada, C. Kaito, T. Inoue, J. Cryst. Growth 289 (2006) 275-277; T. Kaito, A. Mori, C. Kaito, J. Chem. Chem. Eng., 9 (2015) 61-66]. In the former, the silica gels were used as a medium of a crystal growth of PbBr2 and aligned arrays of crystallites with long axis parallel to B were obtained. In the latter, Pb(II) nanocrystallites were formed in silica xerogels by electron irradiation. Both of the short axis of PbBr2 crystallites and the diameter of Pb(II) crystallites were a few tens of nanometers. This size must be a size of short axis of pores in the gel networks elongated affected by the magnetic field. Since the PbBr2 crystallites were elongated along the magnetic field, we conclude that the Pb(II)-doped silica gel networks aligned along the magnetic field.
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