Omelette Christian Soldier (![[info]](http://p-stat.livejournal.com/img/userinfo.gif){kind=small} georgelazenby) wrote,@ 2004-08-15 19:25:00 |
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| Current mood: | This entry took three friggin' hours. |
| Current music: | Son House - Death Letter |
Ok, one week after I actually did it, here is the story of what I did last weekend. I think you'll find it interesting. Included are a bunch of pictures, a few movies, a table, 200,000 KeV and several things I have never done before.
So, my friend Oliver has this thing for Iridium. If you've read Uncle Tungsten, you know about his thing for the chemical elements and particularly those with the most of atoms in the least space. In the density department, it's hard to beat Iridium, at ≈ 22.4 g/cm3. Oliver says in his book that, at the London Museum of Natural History, there used to be a wall-sized periodic table; in this table was a lump of Iridium commissioned by Napoleon III for his niece (don't ask; I don't know why) which England had somehow gotten a hold of, and stuck in this display. Anyway it was about the size of a fist and if it was close to or at the theoretical density of Iridium, 22.4 g/cm3, that would make it about twenty pounds. Oliver fixated upon this Iridium, what it would be like to hold it, and generally developed an obsession with obtaining something like it. However, Iridium is an extremely refractory metal, melting at 4,130 °F/2,446 °C. The hierarchy of refractory metals looks something like this:
| Tungsten | 3,422 °C | |
| Rhenium | 3,138 °C | |
| Osmium | 3,033 °C | |
| Tantalum | 3,017 °C | |
| Molybdenum | 2,623 °C | |
| Niobium | 2,477 °C | |
| Iridium | 2,446 °C | |
| Ruthenium | 2,334 °C |
So it's very difficult to melt in the first place; in addition, Iridium is almost never produced commercially in hunk form; it simply has no use as pure, solid Iridium. Rather, the totality of the Iridium market is an additive to other metal to imbue some of Iridium's properties to the resulting alloy. Thus, Iridium never leaves the powder stage of the refinement from its ores. The powder is simply thrown into the moulds for fountain pen nibs or whatever, along with the platinum that makes up 90% of the alloy.
Fast forward sixty years. Theo Gray and Max Whitby have teamed up to make museum installations very much like what was in the London Natural History Museum. Oliver knew Theo sorta through me, as all three of us have this fixation on the periodic table (I know Theo through
gwferguson and a post he made in spring 2002). Anyway, Oliver soon found out about Max through Theo, and through Max found out that Max could make Iridium buttons in an arc furnace Max had cobbled together. These buttons look exactly like this:
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A few months ago, Oliver bought a kilo of these buttons, and kept them in, what was for a while, the heaviest 6 fl. oz. jar of current jam in the universe. While I was up there, he gave me one of these buttons, which I promptly nearly killed myself with. But I'm getting ahead of myself.
So Oliver has these buttons in this current jam jar. The next logical step is to make the buttons one with each other, to get as close as possible to theoretical density. How to achieve this? Max's arc furnace can only fuse 5 gram buttons (poorly) into irregular buttons of about 50 grams. No, this project calls for industry, with its pumping pistons, its smoking smokestacks and desolated landscapes. Enter ********** [company name deleted]. Exeunt pumping pistons, smoking smokestacks and desolated landscapes. This, is in fact, the setting for the most advanced high purity metal processing plant in the United States:
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If you were to turn 180° from these pictures, you would see an uneventful tan industrial shed about fifty feet high and three hundred feet long. Inside this shed you would find three batshit insane Russians, one very quiet Russian and this:
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The Russians will be the subject of a later entry. For now, the furnace. The thing pictured above is an electron beam furnace. I'm bound by a confidentiality agreement with said batshit insane Russians not give technical details about this thing, but I'll explain the principle. This thing is really an elaborate television. All you have to do to a television to get this is: replace the screen with a crucible, stick a coolant system on it, juice up the cathode voltage from 10,000 electron volts to 200,000 eV, steal from a newly post-communist metallurgy lab, bring it to New Jersey and add one batshit insane Russian operator. It's a cinch.
Now, click on the picture above, a 190 k enlargement of the thumbnail should open; on it there are parts numbered one through eight. The picture is really two identical machines next to each other, and the number describe only the left hand set of machinery. This is what those main parts do.
1. The coolant tank, it is the reservoir for the cool water which circulates through the machine to.... wait for it... cool it.
2. The vacuum pump. This removes the air from the vacuum tank to allow the electrons free passage to the crucible. The vacuum also prevents the metal to be melted from oxidizing.
3. First vacuum staging tank, this allows cool air to be injected into the main vacuum tank when the melt is complete. The thin pipe spiraling around the tank cools this air.
4. Second vacuum staging tank. There is an airlock at the far side of this tank which allows the cool air to be admitted at the desired rate.
5. The main vacuum tank. In this sits the crucible, in the crucible sits the sample, and in the sample sits all our hopes and dreams. Both the vacuum tank and the crucible are cooled.
6. Control panel. This is where the operator addresses the finer points of voltage and current. The voltage and current come from the large bank of transformers directly behind the photographer.
7. The beam control panel. This allows the operator to control the width, intensity and focal length of the electron beam. This control comes from magnetic chokes that deflect the beam this way or that.
8. The cathode. This is the electrons are emitted. The gray cable to the right of the orange cylinder provides the cathode with its 200 KeV. The electrons travel down that stem, through the chokes and then into the vacuum chamber.
So, the metal goes in the crucible, the crucible goes into the vacuum chamber and all three get really hot. So, what does this look like?
Well, before that, I should probably talk about the set-up for photographing this. It is shot with a Nikon CoolPix 4500 (by Theo) through a viewing port. The Iridium in most of these pictures is at something like 2,500 °C. This is about the temperature of a 200 watt light bulb filament. So, what does a light bulb filament weigh? Half a gram? This means that Theo is photographing 900g/0.5 = 1,800 200 watt light bulbs from about eighteen inches away. The question that should be leaping to mind is "How in the hell do you photograph 360,000 watts of light?" I don't care how short the exposure time is on your camera; even if it is fast enough, your film or CCD will never be sensitive to get an image that doesn't look like a glowing blob. What's the solution? A strobe. Inside the viewing port there is a spinning disk that has a radial slit in it. Depending on how fast this disk spins, you can not only look at the melt with puny eyes, but also expose a decent frame of film or bits:
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The buttons just beginning to melt.
Click for a 3,562 KB QuickTime movie
A movie of the electron beam on the surface of the Iridium.
It is a wide beam, and, as you can see, conical in shape
(with the billet intersecting the cone). There is a rhythmic flicker
as the strobe synchs with the frame rate of the camera.
Click for a 729 KB QuickTime movie
A movie of the electron beam more tightly focused.
Click for a 1,832 KB QuickTime movie
There is a grain of oxide at the bottom of the melt which
decomposes and splatters some of the Iridium.
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The final shape of the Iridium, a square billet.
And so the Iridium was melted. Here is the final product:
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The day after this, that is, last Saturday, Oliver and I took the Iridium to Theo at the Plaza Hotel to have a QTVR made of it. So, in a room of the most disgusting hotel in the world, this QTVR was made. A QuickTime Virtual Reality object is made by taking a number of pictures of something and having QuickTime make a manipulatable object out of them. In this case, the Iridium billet was placed on a degree dial, and turned seventy-two times. This process is usually motorized and automated, but the Plaza being the den of deprivation that it is, we had to turn by hand (and by 'we' I mean Theo turned it while I played with Russian nesting dolls). The grayish background is a piece of black construction paper stuck to a big gilt mirror with a label ripped off a bottle of Fiji water (that was my sole contribution to this process).
Click this image for a QTVR of the billet.
After Theo made the QTVR, and after I had taken part in a skit, written by his five year old daughter, in which I played a fairy that made flowers grow, we all went to a deli around the corner. As we were walking away from the Plaza, Theo told me that he'd gotten an angry email from the batshit insane Russian who owned the company we were at the day before. In this email, Russian #1 detailed his suspicion that I was a representative of a competing firm come to steal his metallurgical secrets. This was, he said, the only way he could explain someone being so interested in high purity metals and alloys. Specifically, his high purity metals and alloys. I have to say I was flattered.
After lunch, we decided to go to the American Museum of Natural History, where I made a beeline to Ahnighito, the world's largest meteorite on display:
All 66,000 pounds of it. This was part of a much larger asteroid which exploded over Greenland about a thousand years ago, and one of a group of three that survived the blast. For the thousand years between when the thing fell out of the sky and when it was decided that pieces of metal this big were too important for white people to leave in the snow, Inuits worshiped Ahnighito and the smaller fragments. When explorers first came upon the Inuits, they found that they had high quality Nickel-Iron tools with no apparent mines or trade links. Then Robert Peary was led to the three enormous meteorites which the Inuits had been using as source or Iron for the past thousand years. Eventually it was decided that this much Iron was being wasted on all those seals and snow-people, so, in 1894 Peary constructed a rail line over miles of ice to the nearest port, where, after a few failed attempts, it made its way to New York City. Once there, the source of Greenland's Iron Age was sold to the American Museum of Natural History for $40,000.
But this is all sidebar stuff; the important thing about Ahnighito is that it has 10,000 times more Iridium in it than 66,000 pounds of representative earth rock. This hunk of Iron has about half an ounce per ton of Iridium, the same as the concentration of Gold in the best South African ores. This means that the newly conglomerated Iridium billet and this 33 ton piece of sky Iron contain roughly the same amount of Iridium. Hence this nice photo op:
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So that's what I did all of Friday, and about three hours of Saturday, last week. More to come about the Russians and maybe a crazy Jewish sculptor.
All images and movies taken and copyright by Theodore W. Gray</i></center>
