Re: Chemical synthesis of F2


"Rue John D'Ian" <istjohn@xxxxxxxxxxx| A lifelong pursuit of "impossible" chemistry. Christe, Karl. Loker
| Hydrocarbon Research Institute, University of Southern California, Edwards
|

[snip]


----------------------------------
New Scientist 6 May 2000
Opinion interview

Handle with care!

Karl Christe takes danger in his stride. He has to. In forty years as a chemist developing
explosives and rocket propellants, he's seen how bad it can get. But then, it's not an
area that attracts faint hearts. Christe has earned a reputation for ignoring conventional
wisdom. He's synthesised dozens of previously unknown compounds several the test
books said were impossible. His latest made headlines last yeas as one of the most
violently explosive materials ever produced. It was also the first new form of nitrogen in
more than a century. Jonathan Knight wondered what spurred him on ...

You spent many years developing rocket fuel for the civil sector, now you?re doing more
explosive work for the US Air Force. How come?

I came to the US after getting my PhD in Germany and worked as a fluorine chemist for
five years in the Bay area. Then a colleague has an accident that burned down the
laboratory. That and a shift in commercial interests prompted the company to cancel its
fluorine research. The leader in rocket propulsion was Rocketdyne. I convinced them to
hire me and worked there for 27 years making novel rocket fuels and oxidizers. That
also came to an abrupt end when two colleagues got killed. They were burning old
explosives and had a premature ignition. Rocketdyne abandoned chemistry. I wanted to
continue, and the USAF research laboratory in Edwards was one of the few places
where basic rocket propulsion research was still being done.

Do such accidents happen often?

No, they?re very rare. These were people working on conventional explosives on a
large scale. Usually it?s human error or poor judgement. It?s no more dangerous than
mining or the chemical industry.

So you?ve really got to know what?s worth trying and what isn?t

You must use your own judgement to decide if a compound should exist or shouldn?t
exist. If conventional wisdom says something can?t be made, the challenge is to make it
anyway. The reason I have tried so many different things over the years is I get very
bored with routing work. I want to do the breakthrough work on energetic materials and
let other people fill in the details.

Is the term ?energetic materials? a euphemism for explosives, or is there a difference?

No, it doesn?t mean exclusively explosives. There are different applications for energetic
materials?they can be used as rocket propellants, or in batteries or fuel cells.

So not all energetic materials would work well as explosives?

Absolutely. You need a certain detonation velocity. If something just burns and it
releases a lot of energy but the kinetics are too slow, then it wouldn?t make a good
explosive. You have to know what the kinetics are, whether it decomposes very rapidly
or not. If you have a reaction going in a closed container, you build up pressure, and the
reaction kinetics increase with the square of the pressure. So in a closed container,
what starts out as combustion will turn into an explosion. But if you have the same
material in a wide open system, burning won?t turn into an explosion?you?d get
propulsion.

One of your early successes was to make elemental fluorine using a chemical reaction
even though everyone said it could only be done electrochemically. How did you do it?

In 1986, I was invited to give a review paper on the chemical synthesis of fluorine at a
jubilee celebrating the discovery of fluorine. As I started to make my visuals, I realized it
would make a hell of a boring lecture to tell everyone you can?t make it. You could read
that in any high-school textbook. I became convinced that there was no reason why you
shouldn't be able to make it. So a week before the meeting, I went into the lab, and in
three days I had made elemental fluorine by chemical means.

Last year, you made the N5+ ion, the first new form of nitrogen in more than 100 years.
Didn't you blow up a piece of equipment in the process?

Well, you know that sort of thing is usually blown out of proportion by the press. All they
look for are sensational stories. With N5+ there were press reports that it was the most
powerful explosive ever made, but this was hype. For one thing, we can only prepare it
as a relatively stable salt. And for another, what does "most powerful explosive" mean?
Highest detonation pressure? Highest detonation velocity? Do you include only
practical explosives or extremely unstable ones too? It's not black and white.

So what really happened?

Our experiment was carried out on a very small scale, and maybe 2 or 3 milligrams of
the material shattered a glass flask. It was quite spectacular that such a small amount
could do so much damage. Our first expectations were that the compound would be
very unstable and very violent when it decomposed. But since we had been able to
handle it safely up to that point, I was very concerned that maybe we hadn't made it
after all.

So you were relieved when it blew up?

Yes.

Are you still working with nitrogen?

Yes, we're trying to make the first allotrope of nitrogen, which is an extension of the N5+
work. An allotrope is an alternate molecular form of an element. With carbon you have
diamond, graphite, buckyballs. Sulphur has almost 30 allotropes. But nitrogen has none,
there is only nitrogen gas, N2. By itself, N5+ isn't a nitrogen allotrope because it's
charged. But if you can make a counter-ion exclusively of nitrogen, you'd have a true
nitrogen allotrope. So we want to make N5+N3-. This is much more challenging than
making other allotropes because nitrogen allotropes are extremely unstable and
explosive. It's like a ball sifting on a very high mountain with just a tiny ledge keeping it
from rolling downhill.

So this allotrope is even more dangerous than the N5+ salts that you already made?

Imagine surrounding each energetic N5+ ion with a sort of padding, much as you would
protect a box filled with very fragile glass bulbs. If there is packaging material-or
ions-between each bulb, the implosion of one bulb won't spread. Now take the pack-
aging material out, and put explosive material in between the bulbs. If one bulb goes,
the whole box immediately blows up. That's the difference between N5+ and its
"packaging" ions and something like N5+N3- where the balancing anion is also
energetic. You're walking a very fine line.

Wouldn't N6 be neutral by itself? Why not make that?

Cyclic N6, the benzene analogue, is unstable. Catenated N6 which has a Z shape,
should be more stable. It might be possible to make it by combining two N3 radicals.
The problem with catenated N6, however, is that its central bond is quite weak and its
barrier to decomposition is low. I work with numerous theoreticians on this. I come up
with a structure that looks desirable to me, they do their calculations if they find one
bond is very long know it's a very weak bond and I won try to make the compound.
Remember the ball sitting on top of the mountain. ledge?which represents the barrier
to decomposition?is extremely small, then the thermal energy at room temperature will
be enough to vibrate the molecule apart. In other words, our ball over at the slightest
tremor.

What are these polynitrogen compounds good for?

If we can make N5+ N3-, it would be an extremely powerful explosive with a detonation
pressure three to four times the state of the art explosives such as HMX and RDX.
These are maybe 60 per cent more explosive than TNT. And as a rocket propellant it
would double the power of the typical monopropellants that are used today. The
question is how sensitive these materials are, because they release so much energy. If
they are very sensitive, they could be extremely dangerous. If you have an astronaut
sitting on top of a rocket, the propellant has to be safe.

Is there a Holy Grail in your field?

Probably a compound that is several times more powerful than the best-known
materials, but is completely safe to handle, cheap and environmentally friendly. Polyni-
trogen wouldn't be cheap and probably not completely safe to handle.

Do you ever worry about the morality of developing these explosive materials?

There's nothing immoral about increasing the energy content of materials. Take
nuclear research. You can run nuclear power plants for peaceful applications, or you
can build an atomic bomb. The morality of the user is what counts. It's the same thing
here. A strong defense is the best guarantee of peace. Just because N,' is highly
energetic doesn't mean we must use it for aggression. We're trying to push the limits of
science: we want to make the first allotrope of nitrogen, we want to see how much
energy you can pack into a compound and still be able to handle it. You can kill plenty
of people with conventional explosives. You don't need any exotic materials.

Joseph Rotblat, the Nobel prizewinner who campaigned against nuclear weapons,
suggested that scientists take a Hippocratic oath....

I don't think it's a good idea. How could Albert Einstein or Otto Hahn have predicted
that people would build an atomic bomb? To tell them that they should never have done
their work because it would find applications in mass destruction would be fatal for
science.

Has anything that came out of your work been used in conflicts such as the Gulf
War or the NATO action in Kosovo?

No.

Nothing. Not a squeak.

Does your research have any specific peacetime applications?

Yes. We have a contract with a German company to develop industrial materials.

Do you find working with energetic materials stressful?

Doing challenging chemistry in this field is like mountain climbing. It would be suicidal
for a recreational hiker to attempt to climb Mount Everest alone without oxygen. But
there might be a few highly skilled experts who are willing to test the limits. If they do it
right, they have a good chance of succeeding and surviving. We work very carefully on
very small scales, so even if something explodes it's more like a firecracker. And we use
safety gear.

Have you ever thought, this work is too dangerous, I'm going to pack it in?

No. You have to know what you're working with. It's like driving a fast car. It doesn't
mean you shouldn't drive the car, it's just if you do you have to be more careful.

--------
For a pic of Karl Christe http://itss.raytheon.com/whats-new/98archive/hedm.html



donald j haarmann
------------------------
What we could do with round here is a good war.
What else can you expect with peace running wild
all over the place? You know what the trouble with
peace is? No organization. Bertolt Brecht


.

Relevant Pages

  • Re: TERROR PLOT or police make false claims
    ... "Detective also found a suspected bomb factory containing liquids and other ... materials that could be put together to make explosives. ...
    (uk.legal)
  • Re: Taliban downs two US choppers
    ... >>> explosives to take down a huge building or blow up a subway train in ... >>> reduce dusting and hazard and make a slurry. ... >> Do you have any idea how much gunpowder you'd have to sneak on to a bus ... > binder material, dissolved in a solvent, and mix the materials with an ...
    (rec.boats)
  • Re: Strongest chemical explosive/mass
    ... mixtures of combustible materials with an oxidizer. ... approaching the speed of sound. ... latter will rise quickly as the internal pressure rises. ... The term 'high explosive' is used for explosives that typically have ...
    (sci.military.naval)
  • Re: Gordon Moore on explosives, and semiconductors
    ... >Moore was a chemist by training, and explained that he got into chemistry ... >successful explosives hobbyist: All digits present.) ... When using sugar and potassium nitrate to make rocket fuel, ... Chlorate, Zinc, Sulfer, Ethylene Oxide, Picric Acid, white and yellow ...
    (sci.electronics.design)
  • Re: ATFs alledged information on club permits
    ... The commenters' contention that the proposed rule, if adopted, will have a negative effect on small businesses is based on their assumption that there will be reduced participation in the hobby by sport rocket hobbyists. ... Many commenters argued that the permitting, storage, and other requirements for rocket motors containing more than 62.5 grams of propellant are overly burdensome for the average sport rocket hobbyist and, as such, many will choose to leave the sport. ... the result of the exemption would be to lessen the burden of complying with requirements of the Federal explosives laws and to encourage participation in sport rocketry. ... ATF has recently advised rocket clubs that, if they hold a valid Federal explosives user permit, they may sponsor rocket launches and provide rocket motors to club members. ...
    (rec.models.rockets)