Difference between revisions of "Pure metals and metal alloys"

Revision as of 10:39, 13 December 2023

Pure metals and (checkerboard pattern mechanosynthesized) metal alloys
may often not be suitable for gemstone metamaterial technology.

That is due to:

• surface diffusion at room temperature and
• limits on passivatability => metallic welding on contact
• strong tendency to oxidation (not relevant if well encapsulated - most of advanced nanomachinery will be well encapsulated and in PPV)

Diffusion

Actually it depends:

With no grain boundaries and no internal vacancies or interstitial defects
many metals will likely feature no internal diffusion at room temperature.

If surfaces are completely flat all the way to full crystallographic plane turns
with no crystallographic steps on the planes, then there usually won't be any diffusion on the surfaces too.

Accumulated defects from radiation may start to diffuse around though.
Also mechanical overload may lead to introduction of defects that start to diffuse
instead of staying pinned down or causing a "clean" break right away, like in the case of the more covalently bonded typical gemstones.

Some metals have quite covalent character:

• Tungsten (it's very rare though so not very interestig as a structural material)
• Tin in its covalent "grey tin" phase where it crystallizes into a sparsely filled high volume crystal structure like silicon and diamond (elements of the same group)
  Mechanical properties of solid (mechanosyntesized) grey tin are as of yet unknown.
  We only know it as a powder originating from an usually undesired phase transition.
• Copper needs only to be put into a 2:1 ratio with oxygen (Cu₂O) and it already becomes a transparent nonmetallic gemstone called cuprite. Quite odd.
  It seems it's nobleness (few available hull electrons to give away to form bonds) puts it near to nonmetallicness.
  It's not mechanically brittle on it's own though (like tungsten and alpha tin).
  Quite the opposite actually.

Oxidation

If used as nanoscale functional elements pure metals or alloys must be kept in PPV.
Otherwise by contact with oxygen they would be very quickly destroyed by formation of an
macroscale oxide layer (possibly porous) that would grow thicker than the part itself.
Thereby blowing it up in volume distorting maybe cracking it and whatnot.
See: macroscale surface passivation An exception to this is gold which is nonreactive enough to mostly ignore exposure to gaseous oxygen.
But it is to scarce soft and heavy for larger scale structural applications.

Related

• Nanomachinery encapsulation and Practically perfect vacuum
• Passivation (disambiguation)
• Feynman Path
• Scaled down 3D printing

Complementary materials more suitably for gem based APM

• Gemstone-like compound
• Gemstone
• The defining traits of gem-gum-tec

• Passivation (disambiguation)
• Passivation layer mineral
• Oxidation