How does the rolling process affect the surface morphology of tin foil? This may influence its folding or how it interfaces with different materials.
1. Surface of rolled metal. When Aluminium foil is fabricated, it is rolled between two rollers, one of which is smooth, the other rough, to prevent tearing or slipping. A thin layer of lubricant is applied to the rollers to aid the process. Imaging the foil at the submicron and even nanometre scale allows us to see the effects of the rolling process, as shown here.
2. At the 20 μm scale, the shiny surface looks like this The grooves formed by the rolling process have a period of around 1 micron and depth of 20-100 nm.
3. At the 6 μm scale We can now start to see finer structure with a period of around 200 nm in the grooves, and evidence of surface contamination - in this case the organic lubricant used during rolling. In this case, the average roughness is of the order 20 nm, with the submicron grooves having a depth of around 2-5 nm.
4. At the 2 μm scale: We can see the ~200 nm features more clearly with evidence of even finer features below 100nm. At this scale, there are 50nm period structures with mean roughness 2-4 nm. The lubricant particles are now more evident.
Conclusion:This particular brand of foil has characteristic features with length-scales ranging from several microns to a few nanometres, and has a high coverage of contamination.