John paul III
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Is there a way to make soda lime glass conduct heat?
I want to make a hard and heat resistant ceramic by making glass heat conductive, as this would prevent the outside cooling much faster than the
inside and therefore thermal cracking.
What additives are used in heat conductive glasses? would graphite work? google did not help me much
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Fulmen
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I think you're barking up the wrong tree here mate. Glass isn't ceramic, it has a fairly low melting point and that's not due to low thermal
conductivity.
We're not banging rocks together here. We know how to put a man back together.
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John paul III
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depending on who you ask glass can also be considered a ceramic. And im not trying to make it more refractory, but more thermal shock resistant - and
the way to do it is either limit thermal expansion (difficult) or by making it more heat conductive
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Fulmen
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I doubt it. Glasses are amorphous, ceramics are crystalline. But whatever.
If your goal is to increase resistance to thermal shock the best option will probably be low thermal expansion. Pyrex uses boron oxide, that should be
simple enough to get? Alumina has also been used, but will probably require higher temperatures. Lead (crystal) glass is said to be elastic, perhaps
that could help?
Increasing thermal conductivity is an interesting approach, but I don't know of any simple tricks. The best conductors are metals, but I have no idea
how a glass/metal (or graphite) composite would behave.
We're not banging rocks together here. We know how to put a man back together.
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Chemetix
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I think you are trying to reinvent the wheel here, there are some very technical glasses that have been developed for heat tolerance, aluminosilicates
outperform quartz in some applications.
But if it's ceramic you are after, you need beryllium oxide ceramics, they conduct heat extraordinarily well if it's just thermal conduction
properties you want. I've mentioned the fabled Aluminium Oxynitride glass on here before. ALON. Almost indestructible.
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metalresearcher
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If you really need high thermal conductivity AND have lots of $$$, use diamond. Heat resistant as well.
But, no joking, quartz can do the job, some suppliers sell quartz labware, although more expensive than borosilicate glass.
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SWIM
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I think quartz is the right idea.
Prices have dropped a bit now that they make cheap quartzware in China, and the stuff sure doesn't crack under thermal stress.
But if you want to make it yourself you'll need some pretty hot torches and furnace. 1700 degrees or more I think (didn't check to see if google
agrees with me.)
And some good UV protection. Quartz is hot enough when worked to give off some fairly short wavelength UV.
I'm talking about fused quartz, by the way, not the crystalline stuff.
I suspect there must be flasks of crystalline quartz somewhere in this world, but I've never seen them.
They'd have to be awfully expensive considering they'd more or less have to be carved to shape.
(Sort of like making the crystal skull. You know, that famous one that was carved in Bavaria in the late 19th century but all those TV shows claim is
a magical object from an ancient culture.)
I don't recall the exact details, but crystalline quartz is supposed to be even more inert to some kinds of chemical corrosion than the amorphous
kind.
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chornedsnorkack
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Quote: Originally posted by SWIM  | I think quartz is the right idea.
Prices have dropped a bit now that they make cheap quartzware in China, and the stuff sure doesn't crack under thermal stress.
But if you want to make it yourself you'll need some pretty hot torches and furnace. 1700 degrees or more I think (didn't check to see if google
agrees with me.)
And some good UV protection. Quartz is hot enough when worked to give off some fairly short wavelength UV.
I'm talking about fused quartz, by the way, not the crystalline stuff.
I suspect there must be flasks of crystalline quartz somewhere in this world, but I've never seen them.
They'd have to be awfully expensive considering they'd more or less have to be carved to shape.
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Or you might grow them into shape.
But this is still problematic.
The standard conditions to grow quartz monocrystals are quoted as 300 Celsius water (requiring about 85 bar), and alkali or carbonates for solvent.
You will need a mold material that endures 300 Celsius alkaline water for prolonged time as the quartz is grown in and around it, and then can be
removed from the completed quartz object.
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RogueRose
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| Quote: Originally posted by SWIM | I think quartz is the right idea.
Prices have dropped a bit now that they make cheap quartzware in China, and the stuff sure doesn't crack under thermal stress.
But if you want to make it yourself you'll need some pretty hot torches and furnace. 1700 degrees or more I think (didn't check to see if google
agrees with me.)
And some good UV protection. Quartz is hot enough when worked to give off some fairly short wavelength UV.
I'm talking about fused quartz, by the way, not the crystalline stuff.
I suspect there must be flasks of crystalline quartz somewhere in this world, but I've never seen them.
They'd have to be awfully expensive considering they'd more or less have to be carved to shape.
(Sort of like making the crystal skull. You know, that famous one that was carved in Bavaria in the late 19th century but all those TV shows claim is
a magical object from an ancient culture.)
I don't recall the exact details, but crystalline quartz is supposed to be even more inert to some kinds of chemical corrosion than the amorphous
kind.
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Quartz seems to be exceptionally insulative of heat. I was working with a glass blower and they heated a quartz tube up to melting and the rod could
be held a few inches from the melted tip. I couldn't believe how poorly it conducted heat and made me really question how quartz lab ware works. I'm
wondering if anyone else has ever experienced or seen this same thing?
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Chemetix
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Quartz isn't much different to borosilicate glass when it comes to conduction of heat, they are about 300-400 W.m^-1.K^-1. Quartz does conduct energy
better via transmission of light. You can burn yourself at the cold end just from the emitted light.
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