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Re: [Phys-l] Stuck powder



The simplest possible conclusion might be that if the substrate is highly cleaned,
and the carrier fluid is highly cleaned, then the powder contamination might be
the cause of the stiction? It has plenty of surface area to contaminate - by definition!

It is experimentally verified that cleaned glass surfaces carry a layer of surface water - so that
precision balances avoid glass containers where practical.

Brian W

On 7/16/2010 11:10 AM, curtis osterhoudt wrote:
I have a suspension of diamond nano-powder (let's say, though it works for many
types of powders) in distilled water (deionized or not). This is put on a
typical glass microscope slide, and allowed to dry under normal conditions.

After drying (I suspect even this definition could get argued about), the powder
is stuck to the slide, until mechanically dislodged. Once dislodged, the powder
is no longer "stuck" to the slide, at least for most macroscopic disturbances.

Why?

Does the water get much of the powder "close enough" -- to the slide, and to
neighboring grains -- to allow shorter-range forces to come into play?

Is there enough of the glass (or powder) material dissolved to serve as a
glue matrix?

Is there enough air absorbed to serve as a glue matrix?

Upon "drying", is there a significant amount of water left behind to serve as
a mono-layer glue?