溶胶Solution12nd.pptx

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Simplified chart of sol-gel processes
The chemistry of precursors solutions
All types of precursors can be used, provided they are miscible.
Metallic salt MmXn, AlCl3, (NH4)2Ce(NO3)6.
Alkoxides, Al(OC2H5)3, Si(OCH3)pounds
1. Solvents
Water
Non aqueous solvents
水是最好的极性溶剂之一,主要原因是什么?
举3个非水溶剂的例子?
极性溶剂和非极性溶剂的主要区别是什么?
酸性、碱性、二性溶剂有何区别?
举例说明Protic, Aprotic, amphoteric(质子性、非质子性、***)溶剂?
Water, H2O
The angle HOH is in the gaseous state, and varies from 118o to 120o in the liquid state.
Dipole moment, = D (1 Debye = 10-30 C·m)
3a1 is delocalized, Lewis base, donating a pair of electrons
1b1 is non binding, a weak  donor
Negative partial charge of oxygen atom of (O) = -
Positive partial charge (H) = +
Results of polar structure I
Water is an excellent liquid medium in which to dissolve ionic solutes
0 = 10-12 F·m-1, the dielectric permittivity of vacuum
r, the relative dielectric constant, r,H2O = ; it consequently largely attenuates the coulomb interaction between two electrical charges.
Results of polar structure II
Molecules are bound by up to 4 hydrogen bonds to neighboring molecules.
Further increase the ability to dissolve ionic solutes.
Auto-dissociate
2H2O  H3O+ + HO-
Kw = [H3O+ ] [HO-] = 10-14 at 25oC
[H3O+ ] [H9O4+ ]
[HO-] [H7O4-]
In consequence, O2- practically does not exist in water, and when a solid oxide is dissolved it immediately undergo an acid base protonation reaction
Non aqueous solvents