Birefringence of silica hydrogels prepared under high magnetic fields reinvestigated

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 PbBr 2 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 PbBr 2 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 PbBr 2 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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“…In Ref. [18], we have reinvestigated the results for quartz cells and overturned the conclusion of Ref. [17] on the sign of birefringence.…”

Section: Resultsmentioning

confidence: 80%

“…[17] on the structural anisotropy in silica hydrogels prepared in a high magnetic field. To do so, a consideration is given relying on a previous result [1] and a recent one [27] with help of a result of the reinvestigated birefringence [18]. Further analysis of SMILS result in Ref.…”

Section: Introductionmentioning

confidence: 99%

Reconsideration on structural anisotropy of silica hydrogels prepared in magnetic field

Mori

Kaito

Furukawa

2015

Colloids and Surfaces A: Physicochemical and Engineering Aspect

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“…Contrary, for compare of the difference between properties along the direction of the magnetic field and those across that the samples were prepared with the magnetic field applied normal to the long axis of the cell. [16] Anyway, the transmission direction of P is set along x-axis. Also the fast axis of Q is set along x-axis.…”

Section: Setupmentioning

confidence: 99%

“…It has taken only a few minutes to measure at one point. The time required for measurement have been greatly decreased as compared with a previous method [13,16] .…”

Section: Measurementsmentioning

confidence: 99%

Semi-Automated Sènarmont Method for Measurement of Small Retardation

Mori

Tomita

2015

Instrumentation Science & Technology

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In usual measurement with the Sènarmont method using a conventional polarization microscope, the azimuth angle of the analyzer at extinction of the emerging light is detected by naked eyes. If the intensity of light is measured as a function of the azimuth angle of the analyzer, one can find the direction at which the intensity is minimized more accurately by fitting. However, this procedure requires much numbers of operations as compared to the usual method, and thus is time-consuming. To circumvent this problem a setting with which the intensity is measured as a function of the azimuth angle of the analyzer is constructed with rotation of the analyzer through a computer control. As a result, the time required for the measurement has been greatly decreased.

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“…It was found that whereas the negative birefringence was obtained for the borosilicate glass cells, a positive birefringence was observed for the quartz cells. Birefringence of silica hydrogels has recently been reinvestigated using quartz cells [24]; the conclusion of the negative birefringence has been overturned. In addition, improvement of the equipment of the Sènarmont measurement has now been in progress [25].…”

Section: Introductionmentioning

confidence: 99%

Electron-Irradiation Induced Nanocrystallization of Pb(II) in Silica Gels Prepared in High Magnetic Field

Kaito¹,

Mori²,

Kaito³

2015

JCCE

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In a previous study, structure of silica gels prepared in a high magnetic field was investigated. While a direct application of such anisotropic silica gels is for an optical anisotropic medium possessing chemical resistance, we show here their possibility of medium in materials processing. In this direction, for example, silica hydrogels have so far been used as media of crystal growth. In this paper, as opposed to the soft-wet state, dried silica gels have been investigated. We have found that lead (II) nanocrystallites were formed induced by electron irradiation to lead (II)-doped dried silica gels prepared in a high magnetic field such as B = 10 T. Hydrogels made from a sodium metasilicate solution doped with lead (II) acetate were prepared. The dried specimens were irradiated by electrons in a transmission electron microscope environment. Electron diffraction patterns indicated the crystallinity of lead (II) nanocrystallites depending on B. An advantage of this processing technique is that the crystallinity can be controlled through the strength of magnetic field B applied during gel preparation. Specific skills are not required to control the strength of magnetic field.

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Birefringence of silica hydrogels prepared under high magnetic fields reinvestigated

Cited by 7 publications

References 27 publications

Reconsideration on structural anisotropy of silica hydrogels prepared in magnetic field

Reconsideration on structural anisotropy of silica hydrogels prepared in magnetic field

Semi-Automated Sènarmont Method for Measurement of Small Retardation

Electron-Irradiation Induced Nanocrystallization of Pb(II) in Silica Gels Prepared in High Magnetic Field

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