Bismuth Crystals

[Hephaestus]

Greetings.

 

Has anyone tried making mega-huge bismuth crystals? I have tried following the methods of theodore gray (cf his website) but I don't want plain old crystal clusters on the bottom of a pan. Some fellows on ebay are selling beautiful large crystals such as http://stores.ebay.com/BISMUTH-CRYSTALS-UNLIMITED_W0QQssPageNameZl2QQtZkm

My single crystals exhibit faces of maximum 1cm square edge. Has anyone acheived larger than this, and if so can you describe scale and methods used.

 

What metals doesn't Bi alloy with?

How do you minimise formation of oxide and hence degradation of your 99.99% Bi?

 

I try growing crystals in a stainless steel beaker, approx 500mL Bi, heating with a bunsen until just molten then dipping in a coathanger.

Cheers.

[jdurg]

Crystals will form on their own without the need for a 'seed' as long as the Bi is pure enough and it's allowed to cool down. As it cools, crystals will form and then grow and rise to the top of the liquid as solid Bi is actually less dense than liquid Bi. When they rise, you just pluck them out and there ya go.

[mmalluck]

I've always been told the slower the cooling process, the larger the crystals will be.

 

The best way to do this would to heat up until it's all melted and then use a oven to slowly cool the bismith over the course of several hours to a day or more.

 

You'll have to play to get it right.

[jdurg]

I've always been told the slower the cooling process' date=' the larger the crystals will be.

 

The best way to do this would to heat up until it's all melted and then use a oven to slowly cool the bismith over the course of several hours to a day or more.

 

You'll have to play to get it right.[/quote']

 

 

I 100% fully agree. The slower the cooling process, the more time the crystals have to form.

[Mendelejev]

Well, I've tried it this afternoon with some Bismuth I got from the university labs. I placed it in a flask and heated it quite heavily, but when it was starting to melt, there began to form a sort of crust, gray, not beautiful at all. I stopped heating, and I got some nasty gray powder that don't shine anymore. What did I do wrong ?? Is it the oxidation that was to heavy ?

[H2SO4]

maybe your Bi had some contaminations in it. If you heat your Bi to long, it will eventualy get ugly. The secret to the buitiful colored oxidation is not to overdo the heating process, but stop it when neccasary.

[Mendelejev]

mmm, yeah. I think I've heated it a little to much. So, if I understand. You put some of your bismuth in a flask, heat it with a bunsen flame, BUT not to much, when it begin to melt, stop heating. And wait until the liqiud Bi forms crystals. Correct ?

[H2SO4]

I usualy dont heat it in a flask, but a metal container, but theres no difference. I usualy melt it but dont go to much over its melting pointer. Keep it to a minumum i believe would be best.

[akcapr]

i always though crystals grew bigger in cold temperature

[jdurg]

The temperature isn't what matters. What matters is how quickly it goes from one temperature to another. When a liquid cools slowly, the crystals have time to form and grow on each other as the liquid turns into a solid. If the liquid is cooled quickly, the crystals just don't have time to form before the liquid has gone below its melting point. As a result, you get a large amount of tiny crystals since the crystals don't have enough time to grow in size. A good analogy with this is ice-cream. If you take some ice cream and let it sit out so that it starts to melt, then you put it back in the freezer, it takes a while for the liquid to cool down so the ice crystals that form are very large and the ice cream becomes almost 'gritty'. Now if you take the ice-cream and instantly freeze it via dry ice or liquid nitrogen, the crystals don't have any time to form and you get some of the smoothest ice cream there is. That's the difference between soft serve and 'normal' ice cream. In soft serve ice cream, the mixture was cooled very rapidly which did not give the ice cream enough time to form sizeable crystals. With normal ice cream, the mixture is cooled much more slowly so crystals have time to grow.

[Hephaestus]

Never make Bi crystals in a beaker - it expands on cooling, cracking the beaker.

I will try the oven. I find using the same batch of Bi several times degrades it due to the formation of oxide. To get rainbow coloured oxides need 4N grade, else oxide tends toward blue.

[crazybean]

I have a huge Bismuth crystal at home that I bought for about £1 in Germany.

I read somewhere they are slightly radioactive! Is this only the denser isotopes, or is this just a lie?

[budullewraagh]

any radioactivity is negligible in a bismuth crystal

[crazybean]

yay thanks. so like a mobile then. i gets it now.

[H2SO4]

like a mobile? A mobile phone? If thats what you mean, then the radiation that Bi emits is completely different from microwave radiation.

[Hephaestus]

The halflife of bismuth was determined late last year, being several magnitudes greater than the expected life of the universe. Bi is considered the last stable atom in the periodic table. No radiation to worry about. Got any granite at home? Granite is a much much greater source of radiation...

[Gallium Guy]

I just stumbled onto this thread perhaps a few years late... Last year I succeded in breaking the 6 inch barrier for a single crystal, and this week have a twin cluster that is 7 and 1/2 inches tall with no attachment points except the base.

I am not sure if there is a world record for Bismuth crystal size but would like to know. I have up to 5 pound single crystals and clusters to 8 pounds.

Besides Gallium, Bismuth is my other obsession.

[Alchamisto]

I just scrapped 19,000 lbs of Aluminum that contained .09 % Bismuth and the load value was greatly hurt. I now am on the hunt for the biggest peice of Bismuth i can put on my desk so that i can always remember this day.

 

Does anyone know where i can buy a piece OR would anyone here be willing to make me one !?

 

Thanks !

 

Al

[michealm890]

Slow cooling will increase the crystal size, but to really improve the crystal size temperature control is most important. the best results would be achieved by holding the melt just below the melting temperature. This inhibits the nucleation, so the growth of single crystals is promoted. If a seed crystal is introduced the melt would grow on this seed crystal. If you grew these crystal in an oven, a controlled atmosphere would be advantageous. This could be easily achieved by putting some dry ice in the oven as it is heating up. The Bi metal would be in the oven as well so that you would not have to open the oven until after the metal was melted. Since CO2 is heavier than air, so it should stay in the oven. According to the Ellingham diagram generated in the URL http://www.engr.sjsu.edu/ellingham/page3.php and using 0.21 atm of oxygen and selecting all of the Bi compunds and CO and CO2, CO2 is much more stable than the other compounds of Bi at the solidification temperature of Bismuth. If you are worried a chunk of dry ice could be placed over the oven vent to replace any CO^2 that exited the oven. This would prevent the Bi from forming a slag. I would think that the slag is actually a halide rather than an oxide (unless the slag is an oxide of the impurities.) If the edges of the crucible melting the bismuth are kept above the melting temperature and the center of the top of the melt is cooled, the crystals should form there. This is partially due to the fact that Bi crystals are less dense than liquid Bi liquid (which is rare, like ice crystals floating in liquid water, most solids are more dense than their liquids), so the crystals can float in the center of the pool of metal. The best thing would be to promote nucleation on a desired point, rather than on the surface of the vessel.

 

If an ideal crystal growth environment was designed it would be a cooled single crystal of bismuth that was dropped into a melt of bismuth just above the melting temperature and slowly withdrawn. The whole thing would be shielded by an inert atmosphere. Argon would diffidently work. I think N2 should work (if you could get liquid nitrogen) or SF6 since it is so dense (I can't confirm that a nitride or fluoride of Bi would not form.) This would be similar to the Czochralski process. For the type of growth that the average person would want (faceted), the crystal would just be placed in the melt just above the solidification temperature and left there as the melt was cooled. The cooled crystal could be achieved by taking a previously created crystal, and attaching it to a copper wire (actually silver wire would be better, as it has a higher thermal conductivity) and connecting that wire to a cooled surface. Say welding it to a metal bowl filled with ice water. In a pinch, the CO2 could be produced in a pitcher with vinegar and baking soda and "poured" over the pot used to melt the Bi. As an example

 

Any references are in the post or come from the curriculum of my masters in metallurgy. If I am wrong in any of my facts, let me know. Hopefully this helps.

[Johnny83]

On 26/04/2012 at 7:21 PM, Alchamisto said:

I just scrapped 19,000 lbs of Aluminum that contained .09 % Bismuth and the load value was greatly hurt. I now am on the hunt for the biggest peice of Bismuth i can put on my desk so that i can always remember this day.

 

Does anyone know where i can buy a piece OR would anyone here be willing to make me one !?

 

Thanks !

 

Al

 

 

 

2 minutes ago, Johnny83 said:

 

 

 

Probably abit late now but there you go !!!

Edited March 15, 2018 by Johnny83

[Endy0816]

They are cool looking.