Chemistry Reference
In-Depth Information
organic solvents may be very different. Figure 3.5 plots the oxide thickness versus
forming voltage for methanol and glycol solutions.
404
The yield of 13.6 Å/V in methanol
is much higher than that in ethylene glycol.
The type of dissolved salts affects the anodization process as shown in Fig. 3.6.
404
The particular cation in the solution generally does not influence the anodization behav-
ior.
107
On the other hand, the effects of various anions on the anodization behavior are
significant.
404
In methanol, the presence of some anions such as and results
in no oxide film growth but severe pits at very low voltages, whereas in glycol, anodiza-
tion can be carried out up to 100 V. The presence of (curve a) prevents the rise of
voltage and thus the formation of thick anodic oxide. Similarly, it was found that silicon
oxide will not form in NMA containing NaCl.
107
The effect of a specific salt is also
dependent on the solvent. Oxide films of certain thicknesses can be formed in chloride-
containing NMA and ethylene glycol. In chloride- or sulfate-containing methanol,
