The goal this week was to make more nano-silver laced membranes, react them with sulfur, and destructively test coupons to see how fast the sulfur-modified silver nano-particles leach. So, just like that one team playing for the world cup (yes, that one), I was close but missed my goal. I also had an unexpected set of data and a you-should-have-listened moment.
In week one I created a membrane and we sent off coupons to see how consistent the silver nano particle concentration was across the surface. We got the data back. We found a large (200%) difference between the center and the edge of the membrane. Well that changes things. I had observed while creating the membranes that sometimes during the agitation, the center of the coupon had a very thin amount of solution above it. So I modified the process to have a slightly deeper well of reactants (25mL instead of 20mL – with mentor permission). Maybe the center and corner coupons will be closer now. To make sure, I cut our 8 coupons (4 corner and 4 center) and we will test those. That took 24 hours.
I needed to make many more membranes, especially if the silver loading varies. How many? 8 coupons per membrane, with 5 different sulfur concentrations, with 6-8 timed leaching samples, and possibly 2-3 coupons per reading – that’s a lot of membranes. So I started Monday after the RET meetings. And the first membranes – failed. I should have listened. Previously someone mentioned that they thought one of the chemicals (NaBH4) had failed the day after they made the solution. The solution I used was even older. I should have listened. Do over on Tuesday.
Tuesday I created a fresh solution of NaBH4 and created 10 membranes. That took all day. The picture above was membrane #3 or 10.
I then cut out 40 coupons.
I then created the sulfidation chemicals – lots of stoichiometry, solubility, molarity, and -ty’s.
I then reacted everything which took another 24 hours. Note the black speckled lines on the coupons – that’s the silver sulfide. The picture is 16 of the 40 coupons.
So Tuesday this next week I will be doing the leaching. I will have to bring cookies for the mass spec person who will analyze the dozens of samples.
Then we decide what to do next.