If diamonds are made of carbon? and coal is made out carbon

  • Thread starter Sammyg
  • Start date
4
0
If diamonds are made of carbon? and coal is made out carbon, why are diamonds transparent and coal is not transparent?
 
4,222
1
Re: Diamonds

Crystaline structure?
 
49
0
Re: Diamonds

Diamonds are carbon put into high amounts of pressure and heat.

The whole process is very expencive, too expencive for any practical use in making them. The quantity of diamond you get out of any amount of carbon is too costly to be beneficial, therefore, this process is rarely used, if ever.
 

ZapperZ

Staff Emeritus
Science Advisor
Education Advisor
Insights Author
2018 Award
35,109
3,914
Re: Diamonds

If diamonds are made of carbon? and coal is made out carbon, why are diamonds transparent and coal is not transparent?
What Phrak said. It is the crystal structure that is different, i.e. how the carbon atoms are arranged.

Note that it isn't just the optical properties that's different due to the crystal structure difference. The physical strength of the material is also different. Compare the hardness of graphite versus diamond.

This is a good example on why many of the properties of solids depends NOT on the "atomic" properties of the individual atoms making up the solid, but on the "collective" property of the atoms, i.e. how they behave as a whole group. This is why how the atoms of the material are arranged and how they behave collectively are extremely important.

Zz.
 
4,660
5
Re: Diamonds

Diamond density is about 3.5 to 3.53 grams per cubic cm, while graphite is only 2.0 to 2.25 grams per cubic cm.
 

Vanadium 50

Staff Emeritus
Science Advisor
Education Advisor
23,211
5,537
Re: Diamonds

Diamond density is about 3.5 to 3.53 grams per cubic cm, while graphite is only 2.0 to 2.25 grams per cubic cm.
And what does that have to do with transparency?
 
4,660
5
Re: Diamonds

[Bob S] Diamond density is about 3.5 to 3.53 grams per cubic cm, while graphite is only 2.0 to 2.25 grams per cubic cm.
And what does that have to do with transparency?
Diamond is one of several carbon allotropes, which include fullerenes {buckyballs), nanotubes, graphite, graphene, and coal (not really an allotrope). Graphite is a good electrical conductor, while diamond is a good insulator. Diamond is a very good thermal conductor but at the same time an electrical insulator (doesn't obey the Wiedeman Franz law). If sulfur can have red, yellow, and black allotropes, why can't carbon have one that is transparent?
 
Last edited:
4,222
1
Re: Diamonds

Diamonds are carbon put into high amounts of pressure and heat.

The whole process is very expencive, too expencive for any practical use in making them. The quantity of diamond you get out of any amount of carbon is too costly to be beneficial, therefore, this process is rarely used, if ever.
Yes, but the industry produces in the region of 3 billion carats, or 600 metric tons of synthetic diamonds a year.
 

f95toli

Science Advisor
Gold Member
2,932
425
Re: Diamonds

Yes, but the industry produces in the region of 3 billion carats, or 600 metric tons of synthetic diamonds a year.
Indeed, diamonds are much more common that most people think; the reason you don't see more often them is simply that most of the diamonds are quite small (e.g. the ones used on tools such as drills etc).
That said, there are "simple" methods that can be used to grow quite large diamonds but the ones I've seen have all been almost pink so they weren't exactly something you would make jewelry of; but they are still as hard as a "proper" diamond so they have their uses.

There are some companies that can grow large, transparant, diamonds that can be used in jewellry; the ones from e.g. Apollo Diamond are apparantly very good.

There are also companies that are trying to make large diamond substrates for e.g the semiconductor industry. Large diamonds can actually also be used as a substrate for growing YBCO thin films (a high temperature superconductor) although there aren't many people doing that:tongue:
 
103
0
Re: Diamonds

If diamonds are made of carbon? and coal is made out carbon, why are diamonds transparent and coal is not transparent?
Maybe we can explain using semiconductor concept. Semiconductor has a band gap which is the difference between valence band and conduction band, and photons of larger energy than this band gap can be absorbed. In diamond the band gab is larger than visual light I think, but in silicon it is not. So silicon can be used as a infrared light pass filter blocking visual light. Coal is obviously mixture of many crystal like forms so the overall band gap is almost zero, meaning that all frequency light will be absorbed.
 

Related Threads for: If diamonds are made of carbon? and coal is made out carbon

Replies
1
Views
823
  • Posted
Replies
1
Views
16K
Replies
1
Views
9K
  • Posted
Replies
1
Views
4K
  • Posted
Replies
8
Views
11K
  • Posted
Replies
1
Views
473
  • Posted
Replies
7
Views
4K

Physics Forums Values

We Value Quality
• Topics based on mainstream science
• Proper English grammar and spelling
We Value Civility
• Positive and compassionate attitudes
• Patience while debating
We Value Productivity
• Disciplined to remain on-topic
• Recognition of own weaknesses
• Solo and co-op problem solving
Top