recoil from nature's best spring?

no. see the phase diagram for carbon:

you will produce liquid carbon at these temperatures. Additionally graphite is thermodynamically unstable above 14 GPa at any temperature, so you will never get to a higher pressure with your method.

I will consider this more. Thank you for your input!

-Scott

I fail to see any relevance to Percy Bridgeman's expression on "best Sping" in your hypothetical experiment.

You are actually talking about volume change under phase transformation.... not really what Bridgemen meant when talking about most perfect springs.

Incidentally, what is a "Best Spring" anyway, so we could all recognize it if we saw it?

Jim

Bridgeman subjected graphite to over 400kBar at room temperature. It did not convert to diamond and it's volume remained unchanged. I don't know if "natures best" statement is a fact or just a lament in frustration. Hex is so dissimilar to fcc that it won't "collapse" without the aid of a lot of heat and time even under 100s of thousands of atmospheres of pressure.

What do you think he meant?

It doesn't matter what I think.

I don't think about it cause I never read it or the context surrunding it.

Jim

If you're into squeezing rocks you'd find Bridgeman very interesting :) Otherwise it probably sounds like sillyness.

I read Bridgeman in the early 1960's and he was one of my scientific heros.

I feel that you have trivialized the work and thinking of a great man.

Jim

trivialized? how?

Annother error I made was overlooking rate of the conversion. I presumed that the reaction would proceed quickly and continually above

1700K and following the diamond-graphite equilibria curve like train following a track (pressure increasing with increasing temperature in a perfect container).

On of the warning signs was an anecdote from "the diamond makers" that explained how Percy Bridgeman subjected graphite and a diamond seed to thermite ignition (3000 deg c for a few seconds) at 30,000 bar. Dispite no diamond growth observed, the seed survived, indicating they were on the right track (can't grow diamond on a seed that gets destroyed in the process).

This link discusses the rate of diamond graphitization in low pressures.

I gather from this link that It takes 10^84 sec for diamond (at STP) to revert to graphite, which to me is.. practically forever.

Kinetics is a facinating problem. I've read that solvent/catalysts are a double edge sword in HPHT synthesis. Molten iron is an effective graphite to diamond catalyst in the diamond stability field and conversely it can increase the rate of diamond to graphite conversion at sea level. This fact makes transition metal cemented diamond grit unstable above 800c, effectivly destroying the part.

Could there be a catalyst that enables graphitization of diamond but wouldn't aid diamondization of graphite? I suppose this would be the exact opposite of what Uncle Al is working on, right?

-Scott