Preparation of functionally graded glass by the ultracentrifuge method combined with sol-gel method and the physical properties.

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It is expected that sedimentation of colloid particles can easily occur in liquid (sol) under a comparatively low gravity field due to the large molecular weigh, although a very high acceleration field of the order of 1 million g was necessary to induce the sedimentation of atoms. We can manufacture glass by sol-gel method at lower temperatures than the melting method. The purpose of this study is to prepare the graded glass in molecular-scale by the ultracentrifuge method combined with sol-gel method, and to access the physical propertiesIn 2000, we produced an ultracentrifuge which can generate acceleration field up to 30,000 G at 40-80 ℃ in large specimen cylindrical capsules whose axis is coincide with the ultrcentrifuge direction. The graded glass in SiO_2-TiO_2 system was for the first time prepared. In 2001, the proper condition to prepare the graded bulk glass was examined especially focusing on The growth time of colloids before the centrifugation. A transparent SiO_2-TiO_2 glass with molecular-scale graded structure was obtained through many trials. The graded structure in molecular scale is confirmed by XRD and EPMA methods. We observed the infra-red absorption spectra at many points along acceleration field, and confirmed the graded structure in molecular-scale. In 2002, we tried to prepare the molecular-scale graded glass in ZrO_2-SiO_2, Al_2O_3-SiO_2, B_2O_3-SiO_2, V_2O_3-SiO_2 systems, etc., and succeeded in ZrO_2-SiO_2, Al_2O_3-SiO_2 systems. The number of crack of the graded glass was reduced by many trial of sol-gel process. It was confirmed that the graded or composite bulk or film glass in molecular-scale could be fabricated by the ultracentrifuge method combined with sol-gel method. We are going to proceed this research to prepare the functional graded materials for industry.