Diamonds are forever

[Hero999]

Interesting tid-bit: Techically diamonds are NOT forever, they exist as a metastable state of carbon that will decay into graphite if given enough time. Takes some millions to billions of years but that beautiful diamond rock will eventually become a hunk graphite.... eventually...

I don't believe that, diomond seems pretty stable to me, it can stand pretty high temperatures without decaying into graphite so I can't see how this process will happen at room temperature even over billiions of years. The only way I can see this happening is if the diomond is exposed to high energy gamma rays or is composed of radioactive carbon but this would be the same with any substance.

 

[dknguyen]

Interesting tid-bit: Techically diamonds are NOT forever, they exist as a metastable state of carbon that will decay into graphite if given enough time. Takes some millions to billions of years but that beautiful diamond rock will eventually become a hunk graphite.... eventually...

As for some women liking expensive jewellery rather than well-thought of gifts here's a colorful story:

One time i spent 8 months of my free time creating my own synthetic sapphire. Even concocted a special inert atmosphere chamber to precisely control what impurities got in so i could control the color. Once i got the hunk of sapphire i smashed it and ground/buffed/polished down the pieces to get several sapphire gems.

I electroformed an intricate copper box and gold plated it. Then I set the sapphire stones into the box. I installed an MP3 player circuit into a hidden compartment inside the box. In the top of the box I installed a solar panel but placed a piece of faceted glass over the panel so that you could not distinguish the electrodes of panel and thus not realized it was a solar panel but still allowing the solar panel to collect light. This panel charged and powered the mp3 player. Upon opening the player the music would play.

Essentially a high-tech music box. Albeit one with gold plating and artificial gems.

Gave it to my girlfriend as an anniversary gift.

Then she dumped me saying i was so cheap to give her a gold-plated fake instead of an actual gold box with real gems that i didn't deserve her.

I stopped dating after that.

Makes you wonder. What's better? To know what is? Or what could have been?

 

[Mikebits]

Makes you wonder. What's better? To know what is? Or what could have been?

I don't get it. Is that like one of those sayings like; better to have loved than to never haved loved at all, sorta of things???

To me, a girl that does not appreciate a gift from the heart is not a keeper, and you are lucky she dumped you. Imagine if you had to dump her, you would have to have some crumby speech all memorized like, well babe, it is not you, I just need to find myself, or some crap like that, and what a pain that would be...

 

[dknguyen]

lol. "It's not you, it's me. Wait a second...no, it's you. Yeah it's definately you."

 

[Mikebits]

lol. "It's not you, it's me. Wait a second...no, it's you. Yeah it's definately you."

Oh, I see, you have given the speech. lol

 

[dknguyen]

Oh, I see, you have given the speech. lol

You know, I've always been saved the trouble. I've been told by friends I'm somewhat blinded after I've made up my mind- but I do have a very long memory.

i kinda look forward to the day when I get to dish it out to someone who deserves it. I'm an extreme believer in an eye for an eye. THe better people who know me says it's a problem.

 

[Mikebits]

Well, lets just hope the next one is Mr. Right. When you do find that person, you will know. You might find yourself studying botany because your partner does, or perhaps you become a NASCAR fan, just because your partner likes it. When this happens, you have found the right guy, and will never need the speech

 

[dknguyen]

*Mrs*. I'm a guy! What self-absorbed person would have a perfect self-portrait as their avatar? Guys are more sane than girls anyways...

 

[Mikebits]

Well in that case. Insert Mrs. for Mr. Same holds true.

Of course, any chance of me asking you to my prom is off now. lol

 

[Glyph]

I don't believe that, diomond seems pretty stable to me, it can stand pretty high temperatures without decaying into graphite so I can't see how this process will happen at room temperature even over billiions of years. The only way I can see this happening is if the diomond is exposed to high energy gamma rays or is composed of radioactive carbon but this would be the same with any substance.

Diamonds do not withstand high temperatures for very long. In fact, scientists (or alchemists, as this was very long ago...) determined the connection between carbon and diamond when they heated diamonds to 6000 degrees using giant magnifying lenses (i'm not joking). The diamonds burned! at that temperature the conversion was fast enough to ignite the graphite formed and sustain a flame for several minutes. Further, they tested the gas produced and determined it was indeed carbon dioxide, the same gas from burning graphite.

Diamonds are in a "metastable" state. Meaning they are unstable thermodynamically but are kinetically stable since the conversion is so slow. At room temperature they are essentially stable because they are "frozen" into that state. A good analogy is freezing food so it lasts longer. But the food will not last forever and neither will the diamond. The decay is accelerated at higher temperatures for both.

Most (80%) real diamonds that come out of the ground are not gem quality. Some of these are because the decay has already progressed too far and if you place these dull grey to black diamonds under a microscope you'll see tiny black specks of graphite, essntially "crystalizing" out of the diamond since the room temperature and pressure favor that state. This took millions of years to occur before we humans found it but it is happening.

Some types of artificial diamond are actually natural low-grade decaying diamonds that have been reversed by placing them in the same machine that makes totally artificial diamonds. The graphite specks now recrystalize into the diamond lattice because the conditions in the machine resemble the extreme temperature and pressure of the earth where the diamond state is more favorable over the graphite state.

If you still think i'm full of it, here are some links that mention the stability of diamonds

**broken link removed**

**broken link removed**

Diamond - Molecule of the Month

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Material properties of diamond - Wikipedia, the free encyclopedia

This phase diagram shows very clearly that at atmospheric pressure, diamond is not permanently stable at any temperature.

Diamond and graphite properties


Granted, internet sources are not the most reliable/accurate sources of information. So i reccomend you look up some geology textbooks, in particular: geochemistry. they all say that diamonds are unstable at atmospheric pressure.

 

[3v0]

Guys are more sane than girls anyways...

I see it this way. Either you have to view the females as totaly insane, or that they are of another species, and as such can not be expected to act or think like us.

 

[Mikebits]

I see it this way. Either you have to view the females as totaly insane, or that they are of another species, and as such can not be expected to act or think like us.

Well, they are from Venus afterall

 

[Hero999]

Glyph,
I know that diamonds can burn but I still doubt they will convert to graphite at room temperature and pressure because, as one of the articles you linked says, the activation energy for the reaction to occur is very high.

Somehow I doubt that graphite specks found in diomonds in the earth's crust formed at room temperature. I would think it's more likely that they were formed when the dimond was heated or as a result of other impurities when the diomond was formed.

 

[Glyph]

Glyph,
I know that diamonds can burn but I still doubt they will convert to graphite at room temperature and pressure because, as one of the articles you linked says, the activation energy for the reaction to occur is very high.

Somehow I doubt that graphite specks found in diomonds in the earth's crust formed at room temperature. I would think it's more likely that they were formed when the dimond was heated or as a result of other impurities when the diomond was formed.

Even with a high activation energy, if the product is more stable than the reactants, the reaction will proceed eventually. This is a scientific certainty. Although it may take eons, if something is unstable, it has to go.

The enthalpy of the reaction of diamond to graphite proceeds with a change of negative 2kJ/mol. Although small, this does prove that diamond is the unstable form over graphite.


As for activation energy. A high activation energy means the reaction is very slow, not that it can't happen at low energy. A first year chemistry text-book (i personally reccomend ones by Zumdahl) details this.

After digging through the scientific literature I found this article mentions the process as well as the activation energy:

Sacha Welz, Yury Gogotsi, Micheal J. McNallan, "Nucleation, growth, and graphitization of diamond nanocrystals during chlorination of carbides" Journal of Applied Physics, 4207, Vol.93

Using their calculations and numbers I came to a half-life, for pure diamond, of 3x10^15 years. Yes i realize this is a million times older than the universe but the point is, it does happen.

this website quotes the half-life at millions of years: **broken link removed**
Although personally i think they pulled that number out of their ass.

Anyway keep in mind, this calculation is for uncatalyzed pure diamond. Nature however is not that clean, most diamonds contain impurities that catalyze the reaction. In fact this is how diamonds are made articially in a few weeks by including a catalyst material (catalysts speed up both directions of reactions, forward and backward).

So the decomposition of natural diamonds can be sped up by the impurities in it. Those specks in low-grade diamonds, while i agree some of them are probably incorporated crap, others are actually nucleation sites around impurities which are catalyzing the decomposition. The aforementioned article cites a dozen papers where scientists are actively studying nucleation and catalysts.

Bottom line is, Diamonds may outlast humans, perhapes humanity as a whole, and possibly our earth and our sun. But they are certainly not forever. I'll stake my Ph.D in chemistry on that.

 

[Hero999]

Well I have a poor A-level in chemistry so you must be right.

I suppose nothing is forever, everything will revert back to its more stable state. The only thing is it will take a long time as you probably know the heat death of the universe (this seems the most plausible theory to me) will be an exponential decay.

 

[Mikebits]

The enthalpy of the reaction of diamond to graphite proceeds with a change of negative 2kJ/mol. Although small, this does prove that diamond is the unstable form over graphite.

I think I see where you got your -2kj/mole from.

From internet resource.

Carbon occurs in two forms: graphite and diamond. The enthalpy of combustion of graphite is -393.5 kJ, and that of diamond is -395.4 kJ

C(graphite) + O2(g) -> CO2(g) DH = -393.5 kJ

C(diamond) + O2(g) -> CO2(g) DH = -395.4 kJ

Calculate DH for the conversion of graphite to diamond

What we want is DH for the reaction:

C(graphite) -> C(diamond)

C(graphite) + O2(g) -> CO2(g) DH = -393.5 kJ

CO2(g) -> C(diamond) + O2(g) DH = +395.4 kJ

C(graphite) -> C(diamond) DH = +1.9 kJ

So I guess the inverse would be -2 kj C(diamond) -> C(graphite) which would be a exothermic reaction, and what you say makes sense.
Ughh thermodynamics.

 

[Glyph]

Well I have a poor A-level in chemistry so you must be right.

I suppose nothing is forever, everything will revert back to its more stable state. The only thing is it will take a long time as you probably know the heat death of the universe (this seems the most plausible theory to me) will be an exponential decay.

yeah, the death of the universe really throws a wrench into things. I should cash in my stocks...

Ah well, nothing lasts forever... I have it!!! Next time i get a girlfriend i'll give her nothing as that truly lasts forever!!!

 

[Sceadwian]

Bet you'll have a long stream of alternating girlfriends, I wonder if that's anything like AC current? You may have just solved the worlds energy problems! Being a bad partner could cause all our energy problems to vanish! =) Hell the heat output from the girlfriends rage might do it all by itself <snicker>