Difference between revisions of "Passivation bending issue"
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Revision as of 03:33, 1 December 2013
All DMEs need to have a passivated surface. This means they must not have any open bonds. To archive this one usually resorts to the nonmetals of the fifth to seventh main group of the periodic table counting hydrogen to the seventh.
With the elements of the seventh group passivation is in most cases as easy as plugging every open bond wit a single hydrogen or halogenide atom. What makes this method undisirable in many cases is that those single bonds aren't very stiff to shearing forces. When two such surfaces slide along each other there is unnecessarily high dissipation meaning friction.
For sliding surfaces it is optimal when sixth row elements (Oxygen Sulphur) are used in such a way that the sliding direction lies in the plane spanned from the two bonds. Fifth row elements (Nitrogen Phosphorus) will work reasonably well.
The problem (or good thing) now is that atoms aren't perfect building bricks. If they "have" different numbrers of bonds they have different sizes. When a surface is passivated with sixth row elements over a whole lengthe in the bonding plane direction it begins quite strongly to bend (like a bimetal stripe).
[todo add alternation effect channel problem bearing use ...]
