単分散シリカ懸濁液からの繊維状シリカの生成メカニズム

概要

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Fibrous silica was prepared by drying a homogeneous suspension of monodispersed silica particles. The silica fibers consisted of almost closely packed particles. In this study, silica fibers as long as 7 cm and 40-200μm in width were obtained. The main driving force for fiber generation is considered to be the tensile stress which is generated by the water content distribution. The fiber forms in the following steps: (1)formation of closely packed homogeneous SiO_2 film; (2)generation of cracks by shrinking of the film; and, (3)formation of fibers by propagation of the cracks. The fiber width was large when the silica film was thick, the silica particles were large, and the drying temperature was low. Silica fibers were not obtained when the suspension pH was as low as 0.5, the suspension did not wet the substrate well and the silica film was not thich enough. The prepared fiber was very fragile, however, it can be strengthened by calcination. The fibers have ca. 20nm homogeneous pores after calcining at 800℃ for 1 h.
2001-02-01