Naフッ素テニオライトとNaフッ素四ケイ素雲母の水熱処理による"Naセビオライト"繊維の生成

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A fibrous compound with the composition of NaMg_4Si_6O_<15>(OH)_3 was formed from synthetic-micas with swelling character (Na-fluor-tetra-silicic mica, NaMg_<2.5>Si_4O_<10>F_2, and Na-fluor-taeniolite, NaMg_2LiSi_4O_<10>F_2) by hydrothermal treatment with pure water or aqueous NaOH solutions. The temperatures and pressure applied were 300, 450, 600℃, and 100 MPa, respectively. The run duration was 7 days. The size and the aspect ratio of the fibrous compound were depended on the experimental conditions. An average size is about 100 μm in length and 0.5 μm in width. Because of the crystal habit, this compound may be a potential substitute of asbestos, and a new plastic filler. The fibrous compound showed almost the same XRD pattern as those of NaMg_4Si_6O_<15>(OH)_3 and Na_2Mg_4Si_6O_<16>(OH)_2 which have been reported independently to have the same triple-chain silicate structure. These two kinds of structure are quite similar to that of sepiolite but have from one to two Na ions instead of H_2O molecules which are found in sepiolite. The two compounds could be the end members of the solid solution system called here as "Na-sepiolite". The present fibers were identified as an end member of NaMg_4Si_6O_<15>(OH)_3. The conditions to produce the "Na-sepiolite" fiber in a high yield were as follows: to use Na-fluor-tetra-silicic mica and a solution of high NaOH concentration (≥5 M/dm^3), and to treat at higher temperatures than 450℃. Under these conditions, the Na-fluor-tetra-silicic mica was converted to "Na-sepiolite" almost completely.
社団法人日本セラミックス協会の論文
1993-05-01

Naフッ素テニオライトとNaフッ素四ケイ素雲母の水熱処理による"Naセビオライト"繊維の生成

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