Diamonds are forever - Page 3 - Electronic Circuits Projects Diagrams Free

**3v0** · 6th July 2008, 09:33 AM

Quote:

Originally Posted by dknguyen

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 · 6th July 2008, 09:36 AM

Quote:

Originally Posted by 3v0

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 · 6th July 2008, 11:05 AM

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 · 6th July 2008, 03:13 PM

Quote:

Originally Posted by 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.

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: INTRODUCTION TO CARBON
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 · 6th July 2008, 08:21 PM

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 · 6th July 2008, 09:09 PM

Quote:

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.

Quote:

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 · 6th July 2008, 09:34 PM

Quote:

Originally Posted by 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.

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 · 6th July 2008, 09:41 PM

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>

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6th July 2008, 11:05 AM	(permalink)
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. __________________ I also post at the following sites: http://www.stop-microsoft.org http://www.heated-debates.com Screen name: Aloone_Jonez

6th July 2008, 08:21 PM	(permalink)
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. __________________ I also post at the following sites: http://www.stop-microsoft.org http://www.heated-debates.com Screen name: Aloone_Jonez

6th July 2008, 09:41 PM	(permalink)
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> __________________ "Because I be what I be. I would tell you what you want to know if I could, mum, but I be a cat, and no cat anywhere ever gave anyone a straight answer, har har."