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.

Richard Daines