| Summary: | 碩士 === 中國文化大學 === 材料科學與製造研究所 === 91 === The objectives of this research were two: First, to explore and discuss the synthesized particle diameters by altering reaction temperature condition and reaction time in the preparation of silica microspheres by sol-gel method. Second, we used gravitational sedimentation method, i.e. a bottom-up self-assembly, to obtain regularly arrayed colloidal crystal structure using mono sized SiO2 spherical particles.
1. The preparation of submicron monodispersive silica microspheres by sol-gel method: The synthesis started from tetra-ethyl orthosilicate (TEOS) as precursor, ethanol as reaction solvent, and ammonia solution as catalyst, and processed in basic-catalyzed aqueous medium. After hydrolysis, condensation, cross-linking and gelation reactions, submicron silica microspheres were formed. The synthesis reaction temperature ranged from 0oC~75oC and the reaction time was 2 hours. The particle diameter of the synthesized spheres were analyzed by the particle-size analyser. Experimental results indicated that the size of the synthesized silica microspheres varied from 0.443 mm to 0.625 mm. As the reaction time was increased the diameter of silica microspheres increased (from 0.473 to 0.625mm). As the reaction temperature was increased the diameter of silica microspheres was fond to decrease accordingly (from 0.625 to 0.443mm).
2. Use of mono-sized SiO2 particles for self-assembly of regularly arrayed, colloidal crystal structure: In this work, we used gravitational sedimentation method to assemble SiO2 particles on Si wafer template epitaxially to grow regularly crystal-like structure, and to use the field emission scanning electron microscope (FE-SEM) to observe the packing structure. Experimental results indicated that in different volume fraction (0.5 vol.%~3 vol.%) and sedimentation temperature range (50oC and 100oC, respectively), as the solids fraction was held at 3 vol.% and the sedimentation temperature was 50oC, a larger area (about 250 ´ 250 mm2) of regularly arrayed, colloidal crystal structure was resulted.
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