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Sol-gel Processing
1. Principles
??????? (organometallic precursors, ex : alkoxide) ?
? ?? ???? (hydrolysis)?? 1¦Ìm ?? ??? ???
???? ???? ?? ?(sol)? ?? ??, ???? (poly-
condensation)? ??? ? ???? 3??? ???? (3-D
network)? ??? ?(gel) ??? ??? ??? ???? ?
?, ???, ???? ??
2. ?? ? ??
1) high purity
2) high homogeneity
3) low processing temperatures
4) preparing multi-component system
5) ??? ????
6) ??? ??
3. Sol-gel ??? ???? ??
4. ?? ?? ??
1) pH
2) solution composition
3) temperature
5. Examples
6. 3?? ????? ?? : precursor? ??? ??
1) silica¡¤sol-gel processing
2) metal alkoxide processing
3) Pechini-type processing
6-1. Silica Sol-Gel processing
1) Step 1. : Hydrolysis and Polycondensation
- Precursor : liq. alkoxide, Si(OR)4 R = CH3, C2H5, C3H7
- Reactant : Water
- Catalyst : acid or ammonia
- Hydrolysis reaction
- Condensation reaction : forming ¡ÔSiOSi¡Ô bonds
- Polycondensation reaction
: linkage of additional hydrated silica tetrahedra(Si(OH)4)
: forming a SiO2 network
: the water remains in the pores of the network
- Results : formation of the spherical silica particles as
colloidal particles or a sol.