Double anneal
This is a follow up to Jess’ protein separation post. She mentioned that some of the SC 073 samples were annealed twice: the first was a 700 C 60 s anneal to crystallize (before etching) and the second was a 800 C 5 min anneal to stabilize the membrane (after etching). I took some TEMs (of the same samples) before and after the second anneal to see if there were any changes to morphology.
There doesn’t seem to be a difference in porosity or cutoff. Thus, I believe that the second 800 C RTP does little to change the pore morphology and only crystallizes some of the remaining amorphous background. Perhaps pushing the second anneal to 1000 C would change things?
Although it appears the second anneal opened some of the background pores, a look at the high magnification image reveals that these features do not go all the way through the membrane.
An inside sample also showed little change after the second anneal.
It looks to me that the second anneal opened up the background pores. I think the porosity has increased.
I agree w/ Jim- the small pores are more apparent/frequent. Are the two pics typical or more like one of a kind?
Philippe
Also, the samples I used were all interior samples from SC073. From the TEMs these should have been completely crystallized. Do you expect changes with these samples?
I’ve made an update to the post to address your comments.
If we could eliminate the large pores and fully open the background pores, we would have a recipe for high porosity, small pore membranes. It is worth thinking about how that might be done.