Two treatments have been done to Al substrate i.e. silane treatment and alkaline etching. The surface roughness of silane treated is rougher than alkaline etching treated. Why? Can anyone explain this?
Thank you. Do you have any reference papers regarding to your explanation?
Was this done with chloro- or alkoxy- silanes? Was it aqueous or anhydrous silynation? Look for hints in terms of how solutions at different pH values etch aluminum.
Also ... how did you measure the roughness, and what were the results? Are the roughness values different within a 95% confidence level, or are they just different numbers (with no confidence levels about a statistical difference)? Does your silane layer remain adherent or was it rinsed away?
The roughness have been measured by using a surface profilometer..the roughness value for NaOH treated surface was 0.68 micrometer (s.dev 0.1), for silane treated surface was 0.92 (s.dev 0.15). Yes, the silane layer remains on the substrate by the covalent bonding.
What was your starting roughness? Have you measured how thick and uniform your silane layer is? As asked already, do you know the chemistry of your surface before and after etching? Do you know whether the silane treatment changes that underlying chemistry? What happens to roughness if you silynate an alkaline etched surface?
Etching removes surface material. Silynation adds material to the surface but may also remove surface material in the process. I think you need to pursue experiments to confirm whether the alkoxy silane also etches the surface (differently) and how the added silane layer is covering your surface, for example in patches or agglomerates.
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