[maxh]

Addition of an aldehyde to Tollens' reagent (a silver-diamine complex) causes Ag to precipitate and plate onto the glass of the container, creating a mirror.

My questions are:

1. How tightly does the Ag adhere to the glass?
2. How would it adhere to alumina ceramic (Al2O3)?
3. How thick do you think the layer can be made?

[plu]

Addition of an aldehyde to Tollens' reagent (a silver-diamine complex) causes Ag to precipitate and plate onto the glass of the container, creating a mirror.

My questions are:

1. How tightly does the Ag adhere to the glass?
2. How would it adhere to alumina ceramic (Al2O3)?
3. How thick do you think the layer can be made?

Things you might want to consider: What is the chemical composition of the glass of the container?  How does this substance (and its properties) compare with alumina?  What are the crystal structures of this substance, alumina, and silver?  If the crystal structures of the binding surfaces were similar to that of silver metal, what would that mean?

[maxh]

In case anybody's interested, I went ahead and performed some experiments.

First, I plated the inside of a borosilicate glass testtube, which I thought I had cleaned thoroughly (solvents, NaOH (aq.), HNO3). It plated fine, producing a pretty mirror, but when I pick at it with a spatula, it chips and comes off.

Next, I thoroughly cleaned a piece of alumina (1"diameter x 1"length) and wrapped a piece of tape around one end to produce a small vessel with the end of the alumina cylinder as the bottom. I performed the reaction in this, then rinsed and scrubbed with soap and water.
The surface was a brownish color, clearly contrasting with the original bright white color. However, my multimeter treated the layer as an open circuit when I tried to measure the resistance of it.
So, I performed the reaction four more times, each time cleaning the surface well, and after these 5 depositions, I had a shiny, silver layer on my Al2O3!
This layer would not peel up when I picked at it with a metal spatula. I attempted to measure the thickness of the layer, but had somewhat uncertain results. It was around .0001", or maybe half that.
The resistance measured 1 ohm with multimeter leads placed .25" apart, and 2 ohms with the leads 1" apart (at the edges).
So that's that!

Now I'm attempting to build the layer up to .001" with brush-electroplating. My first trial burned the layer up (my voltage was too high, especially considering the poor thermal conductivity of alumina compared to metals), but I have high hopes for the next attempt.

[pantone159]

So, I performed the reaction four more times, each time cleaning the surface well, and after these 5 depositions, I had a shiny, silver layer on my Al2O3!

Did this cleaning involve HNO3 like the first?  (I would figure that would remove the Ag.)

[maxh]

No, just soapy water and scrubbing, followed by a rinse with d.i. water. Excess Ag precipitates out as a flocculent, brown mess which needs to be removed before the next layer is put on.

HNO3 does dissolve Ag readily.

BTW, the plating worked very well. I got up to .0005", half of my target of .001". (I ran out of solution or I would have kept on going.) But now that I know it will work, next time it'll be at least .001"!

For my electroplating solution, I simply dissolved .415 g AgNO3 in H2O to a final weight of 5.00 g.