- #1
Are blocks (billets) of metal crystals?
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Discussion Overview
The discussion centers on whether aluminum billets can be considered as crystalline forms of aluminum or merely aggregates of aluminum atoms held together by metallic bonds. The scope includes conceptual clarification about the nature of metallic bonds and crystal structures, as well as inquiries about the characteristics of metals in bulk form.
Discussion Character
- Conceptual clarification
- Debate/contested
Main Points Raised
- One participant questions whether aluminum billets are in a crystalline form or just a collection of atoms held together by metallic bonds.
- Another participant states that metallic bonds involve a crystal structure, suggesting that calling it a "crystalline state" is a matter of semantics and interpretation.
- A participant notes that aluminum blocks are polycrystalline, consisting of many individual crystals or grains, with sizes typically ranging from 10 nm to 100 μm.
- Another participant challenges the typical grain size by sharing an anecdote about visible grain boundaries in brass door pushes, indicating that grains can be much larger, up to an inch across.
- There is a light-hearted exchange regarding the implications of corrosion and cleanliness related to the observed grain sizes in the context of a school setting.
Areas of Agreement / Disagreement
Participants express differing views on the classification of aluminum billets as crystalline or not, with some agreeing on the polycrystalline nature while others emphasize the variability in grain size and structure. The discussion remains unresolved regarding the semantics of crystalline states.
Contextual Notes
There are limitations in the discussion regarding the definitions of "crystalline" and "metallic bond," as well as the variability in grain sizes across different metals and conditions.
- #2
zhermes
- 1,253
- 3
I enjoyed the picture.
The answer is both. Metallic bonds are when the metal atoms are held in a crystal structure, sharing a 'sea' of electrons. If you would call this a "crystalline state (form)" is semantics... and up to interpretation. A crystal structure is just a highly regular one (i.e. based on repeating units), which a metal is; a 'crystal' is generally a substance in a crystal structure, that often isn't (e.g. carbon is usually in the form of graphite, or coal, or whatever, rarely in a crystal; or quartz--which is the crystal form of silica[sand]).
The answer is both. Metallic bonds are when the metal atoms are held in a crystal structure, sharing a 'sea' of electrons. If you would call this a "crystalline state (form)" is semantics... and up to interpretation. A crystal structure is just a highly regular one (i.e. based on repeating units), which a metal is; a 'crystal' is generally a substance in a crystal structure, that often isn't (e.g. carbon is usually in the form of graphite, or coal, or whatever, rarely in a crystal; or quartz--which is the crystal form of silica[sand]).
- #3
Jbcourt
- 22
- 0
Thank you zhermes.
I have always wondered about this and couldn't get the answer I wanted from the open net.
O'yeah, are all other metal like this also?
I have always wondered about this and couldn't get the answer I wanted from the open net.
O'yeah, are all other metal like this also?
- #4
Mapes
Science Advisor
Homework Helper
Gold Member
- 2,591
- 21
The aluminum block (along with all common metals in bulk form) is http://en.wikipedia.org/wiki/Polycrystal" , made up of many individual crystals, or grains, with sizes typically 10 nm - 100 μm.
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- #5
AJ Bentley
- 667
- 0
Mapes said:
Not always, my old chemistry teacher was fond of pointing out the brass door pushes in the school latrine were so etched by uric acid that the grain boundaries were clearly visible.
The grains were up to an inch across.
- #6
Mapes
Science Advisor
Homework Helper
Gold Member
- 2,591
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Neat!
You can hardly find better examples of (1) corrosion and (2) probability distribution of aim than at a urinal.
You can hardly find better examples of (1) corrosion and (2) probability distribution of aim than at a urinal.
- #7
AJ Bentley
- 667
- 0
I think it was mainly unwashed hands.
The trail extended several fire-doors down the corridor.
The trail extended several fire-doors down the corridor.
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