Does anyone know what happens to ceramic material at really extreme temperatures? I know it can survive getting stupidly hot but there must be some tolerance point where it gives up – does it melt / burn / vaporise or something else?
Ceramics
- Thread starter PeteMC
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A lot probably depends on the specifics of the material and how it's being used. They make parts of spacecraft from ceramics.
I know they do, which is what is making me wonder about it. Re-entry temperatures must be truly ridiculous but surely there's a maximum temp any material can cope with, whatever it is. I know a metal would melt past whatever it's top end tolerance may be, but I don't know how a ceramic would behave under the same conditions.
I'm a materials engineer. In brief, the answer to your question is, "the same thing that happens to anything else." That's basically one of three options:
- Melting (it becomes liquid)
- Sublimating (becomes gas)
- Burning (charring, combustion of some sort)
Exactly what it is will vary by material and the pressure of the surroundings. I'm not aware of any common ceramics that do anything besides melting at reasonable pressures, though. In a lot of cases, the melting temperature of ceramics is high enough that we really don't worry about it.
That's brilliant, thank you. This is why I love AW, there's always an expert on whatever you ask about!
I wasn't sure if a ceramic *could* melt, or if it would just catch fire and burn instead.
So a couple more questions of your expertise if I may:
What impact does pressure have on the equation - is this relevant at atmospheric sea level or only under extreme conditions?
How would a molten ceramic look and behave - glowing and runny like a metal, or different?
What roughly *is* the melting point of a reasonably normal ceramic? Nothing too esoteric like space shuttle tiles, I'm thinking specifically about those knives that supposedly don't set off metal detectors etc.
I wasn't sure if a ceramic *could* melt, or if it would just catch fire and burn instead.
So a couple more questions of your expertise if I may:
What impact does pressure have on the equation - is this relevant at atmospheric sea level or only under extreme conditions?
How would a molten ceramic look and behave - glowing and runny like a metal, or different?
What roughly *is* the melting point of a reasonably normal ceramic? Nothing too esoteric like space shuttle tiles, I'm thinking specifically about those knives that supposedly don't set off metal detectors etc.
"Ceramic" is a very broad term that covers everything from earthen ware pots to the ablative shield on spacecraft that re-enter. I don't know what those knives are made of, but most ceramics are mixtures of metal oxides, with aluminum oxide being one of the common ones with a melting point of 3762F. Zirconium Oxide is another material, and it has a melting temperature of 4919 degrees Fahrenheit.
Molten ceramics look like molten glass, which is a similar type of material with a lower melting point.
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My family used to have a pottery. I've seen pieces melt. They just sort of start to droop. There was one small statue that came out bent at the waist like he was picking something up off the floor when the original was with the figure standing. Charring was very rare. I think I maybe saw it once. I've never observed sublimation, but then it's like baking a cake. You watch it. If you started the kiln set at maximum and just leave, then yeah those other things. Pressure isn't really an issue since kilns aren't pressurized (at least none that I know of) and the variances of atmospheric temperature, also like making a cake do alter firing times but at those temperatures, it's not much of an issue. Now if you had a kiln on Mars, I'm sure it would make a difference. As far as looking like glass, it probably will have a glasslike sheen, but will not become transparent.