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Old 08-20-2013, 09:34 AM   #1
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Doing a search, I did not come up with indium, although this may have already been discussed. Posted 'cause DCRB might be interested:

Indium, which is the 49th element on the table of periodic elements, is abbreviated with the letters. In. It is classified as a metal and has a melting point of 429.75K or 313.88 degrees Fahrenheit. Indium is used as a coating for industrial grade bearings. It is used in conjunction with Geranium in the manufacturing of transistors. It is used in the manufacturing of photoconductors, but more importantly it is used to make alloys. When the proper mixture of Indium and Gallium are combined they produce an alloy that remains a liquid at room temperatures. If you are using a LCD screen to read this article, then you are looking at an alloy made with Indium and Gallium.
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Old 08-21-2013, 07:52 AM   #2
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Indium is in fact very neat stuff, and I have a pound or so in my collection. It's nearly the most ductile metal there is - I can cut a pea sized piece off my ingot and easily make a 2" diameter sheet out of it. You can do about half that with your fingers alone - it's very, extremely soft.
A tiny hammer on an anvil does the rest, or you can roll it between rollers with no fear of it splitting along the outside as you stretch it. Kind of like somewhat stiffer bubblegum in mechanical properties.

Yes, the price has been rising dramatically - but it's all over the place as the economy demands more and less of it, pretty much like any other industrial metal.

In LCD's, indium-tin oxide is what's used for the transparent conductors to turn pixels on and off, not very much conductivity is required for that - they are more or less tiny capacitors you change the charge on to affect pixel brightness - I have some of that too. Indium/gallium is NOT used as it costs even more and doesn't have the desired property of being transparent and conductive at the same time in thin layers. Even ITO looks like a brown rock in bulk - the layers used for the XY matrix are quite thin.

Considerable effort is going into finding a replacement for it due to the rising cost of Indium (Tin isn't that cheap either). While there are other candidates out there, none are anywhere near as simply applied in fine patterns needed for things like LCD displays. ITO can be evaporated over a stencil, sputtered reactively, or deposited by MBE, but the supposed replacements (so far) have to be mechanically placed - things like carbon nanotubes, graphene and so on don't yet have the tech for making complex things out of them, the processes above would simply decompose them. Mechanical placement would cost so much that the more expensive but easier to apply precisely ITO is still the main thing in use outside labs. It's not trivial to "draw" thousands of foot long perfectly straight lines with mechanical placement, to say the least.

At one point it was considered for use making a glass surface conductive enough to replace those lines of stuff you see on most auto back windows for ice melting. But it's too fragile and expensive for that.

I use Indium here in the lab, along with silver, for a calibration check on my neutron counters.
The electrical based counters can be fooled by EMI, where there is no cheating indium or silver.

Indium was used for this in the earliest reactors (Fermi mentions it), and probably still is. When "activated" by neutrons, it then gives off some radiation, with a relatively short half life, so in a sense you "get all your counts back" in reasonable time, which is a very desirable trait, since there is always a background count to contend with in getting accurate results. Silver has an even shorter half-life when neutron-activated, so you see higher count rates for the same neutron dose, but it "cools off" much quicker, to the point where I have to take into account the time from exposure to measuring even if that is only 20 seconds or so, where I have more time (but less output) from indium, since it has a longer half-life. In general, I get about 1/10th the signal off the indium that I do from the silver, but that's not too bad in my case, and one checks the other. (quite a lot of my research is about making sure I'm measuring things right).
Ag: 12.5 minute half life (but it's a little more complex as there are several isotopes, some decay in seconds)
In: 54 min (again, not quite that simple, but it's about 4x longer, so it takes more neutrons in to make the same count rate out from the decay, and you have to let it "cool" longer between uses).

Indium is also used in semiconductors, mainly LEDs with gallium, arsenic, and a few other elements as dopants, depending on the color of light desired.

Gallium isn't cheap either and doesn't "play well with others" when it comes to making crystals of various alloys used in semiconductors - this problem was one of the first successful microgravity experiments done by NASA, as in gravity, things tend to differentiate during solidification too much to get a useful substrate for making LEDs, high-speed low-noise transistors and such. Quality crystals are so hard to grow, it was at one point theorized that it would actually be cheaper to grow them in space and return them to earth for we are talking real expensive, and luckily other fab methods have been worked out, though they aren't cheap, they still cost a lot less than launching even a cubesat and recovering it.

You can buy either at rotometals.
Which also sells some nice bullet casting alloys and other interesting things. They are my go-to vendor for the metals they sell, good guys.

Indium also wets glass, and was once used a lot for temporary or low temperature vacuum seals between glass or glass-metal seals. Its ductility helps stick together things with different tempcos.
It's usually alloyed with tin for low melt solders, and is a component in the low melt alloys used in fire sprinklers, chamber checking cast metal for gunsmiths, and some scientific gear.

It's really fun stuff to play with, I'm glad I got a nice chunk at a lower price than it is currently. Looks a lot like lead till you start handling it and realize how soft it is.

It's probably a bit of a crap-shoot as an investment, though mine has done well, I won't be selling it, I use the stuff. We are running out of it worldwide for certain. But we are also trying to find good substitutes for the main bulk use - LCD screens where it is near-impossible to recover/recycle due to the properties, and the fact that any one LCD screen doesn't have much in it - it's the fact we make so many of them that uses it up.

The price of the gallium alloys is so high we don't use them for things like CPU's vs silicon, even though we'd get a huge speed/power advantage from the better transistors. However, almost all cel phones do have at least one GaAs transistor in them for the high frequency reciever and transmitter part, due to the speed and low noise of these. Ditto cel towers, though they are going to even more exotic materials these days, and even superconducting tuned circuit cavities to tune and match the transceivers.

In is used in tiny quantities in some sleeve bearings but not the type DoChen sells, we are talking about new-old-stock crankshaft sleeve bearings. Too expensive now for new production. It had some nice properties since it also acts to help neutralize acids in the oil that are created by the combination of sulfur in the oil and blow-by. These days, far cheaper additives are simply put into the oil at manufacture for that purpose.

Gallium, BTW, is like water in that it expands a good deal when "freezing" which is not far from room temperature. People who don't understand that used to sell it in tiny glass bottles, leading to losses when the bottle cracked and it leaked out next time it was molten (a warm day will melt it).

Gallium has an interesting use, sadly "submarine patented" along with aluminium, for energy storage. A little Ga mixed into aluminum prevents the protective layer of Al2O3 from being so robust, and the alloy mixed with water releases hydrogen...but when it comes right down to it, Al is made with heat and electricity, and the "solution" isn't all that practical in real life. The Gallium doesn't react, but must then be extracted from the aluminium oxide later before refining that back into Al metal. (pardon my british-english spell checker...I seem to prefer the UK spellings of many things so it became my default).
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Old 08-23-2013, 05:47 AM   #3
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...yeah, I remember from my "Semiconductors" class in college, the lecturer was a huge fan of GaAs - that was back in the time, when Chipzilla was speeding up the next gen processors mostly by increasing clock speeds, and it looked like we're bumping against physical limits soon. Therefore, he believed firmly that switch from Silicone to GaAs is in the making - although he appreciated that GaAs had this snag of higher price going against it - even back then.
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Old 08-23-2013, 12:14 PM   #4
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The thing is, "lattice instability" currently prevents us from integrating GaAs into big complex circuits as well as we have worked out to do with silicon, neglecting that it also costs tons more. We now have silicon with many layers of P, N, insulator, metal - in almost any order, and can do tricks like P dope a slightly N doped piece selectively and change N to P (or vice versa) just where we want to - we don't know how to do that sort of thing with GaAs, grow oxide/nitride insulator layers as well, and so on. So we stuck with ever smaller silicon transistors so as to be able to make these huge multi-core processors, which few programs actually take good advantage of, and actually, in most cases, don't need to anyway. We're running out on that track as well, but it just doesn't seem to matter all that much at present.

This i5 system I'm running on (very recent build) is loafing, with about 100 stocks showing updates 1/second, 100 or so bids/asks/highs/lows/ten minute trend plots, plus whatever else I'm doing (big charts for TA, web, email, editing stuff) - I'm using about 10% of the system CPU/memory if that. I could fire up windows in Virtual box and get some more out of it, or start a bunch of other processes, but I'm at my own attention/do something about it limit as is. And oh, even with 4 HD LED 24" monitors - the whole mess draws only about 125 watts - nice if you're on solar power on a cloudy day, like I am now.

Wonder why PC sales dropped? The pundits might be right about some of it - I have a tablet too and it's great for joe average consumer to consume things on. Sucks for software dev and most creative tasks (unless taking pix and movies is creative - not for most people). So joe average's 5-8 year old PC is still doing it for him, he doesn't need to buy another one. I have several households I'm the computer support guy for, and they are all in that state. I'm urging them to replace/upgrade before some of this stuff just dies of old age - but you know how that goes when money is tight. The ones I really like I do free backups onto my own media for, because I know what's coming....but they have normalcy bias - it hasn't happened, therefore it won't. When it does, I predict a temporary upsurge in local PC parts won't move the market, though I wonder how many others are more or less in the same boat.

Looking back a little in history, this reminds me of the color TV business (my first good job was a repairman for stereos in a TV sales/repair business). For awhile, we had thriving manufacturing of TV's in this country - a few vendors, and others in Japan. All of a sudden, though, everyone who wanted a TV had one, and it became a replacement market we ceded to the Japanese. Now the only way to get more sales is to dupe us into buying things we don't really want/need - 3d, huge screens, blu ray vs DVD, buy the same content on a new media, junk like that is signs of desperation.

Last edited by DCFusor; 08-23-2013 at 12:21 PM.
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