You put a regular glazed ceramic coffee cup into a very high temp kiln/oven and keep raising the temperature. Does it melt, burn, vaporize or blow up? As the temperature rises what stages does it go through?
What happens at very high temps to ceramic?
If you put cone 6 (red) clay in a cone 10 kiln, it melts. But porcelain clays which are often used in commercial ceramics survive the highest usual kiln temps.
I assume you’re talking about going above cone 15 which is hard to do in a ceramics kiln. My guess is it’ll eventually melt or burn up, but I have no experience with that.
Yes, assume the high temp oven/kiln/heat source can keep going out to 10,000 degrees+ F. What would happen to a coffee cup placed in that environment?
That is approximately the temperature of the surface of the sun. What do you think would happen?
The coffee would get really hot, and then someone would spill it in their lap.
I don’t know. I’m sure it will disintegrate at some point as the ceramic silica matrix can only hold it’s integrity so far as energy increases, but *getting to that point *does a fired clay cup melt like glass at some point as the temperature keeps rising, does it begin to burn or explode into dust? What happens?
Lawsuit!
Ceramics come in many flavors. Is there a standard material for coffee mugs?
Will we see phase changes and chemical changes first? We’re talking about pretty stable materials. They’ll dehydrate, to a point. That might be detrimental to structural integrity of the mug if it is not fully dehydrated. They’re already oxides, and are unlikely to react further to oxygen in the air. Although some ceramics can incorporate variable oxygen levels into their matrix.
If it doesn’t crumble first, I expect it to eventually melt. The temperature where that happens depends highly on its makeup.
We might even eventually see it decomposing and gassing off some material. Even alumina and silica will boil around 3000 °C.
Most (?) commercial ceramics are a form of Porcelain which has a variety of properties depending on the specific recipe used.
This chart has some properties, but I don’t know enough to know if any is relevant to this conversation.
I took a class at a clay studio at some point, and one of the requirements for anything that was going to come in contact with anything that was going to be consumed would have to be coated with a food-safe glaze and all of those were cone 10 glazes so the clay had to be high-fire clay (although probably not porcelain, because that was expensive and hard to work with). I’m not sure if it is a general rule food-safe glazes are necessarily high-fire glazes, or if it was just the selection at this studio.
At my studio, all our cone 10 glazes are food safe (although you don’t really want to use the matte finishes). Our cone 6 glazes aren’t recommended for food surfaces. We have 4 clay bodies; terracotta (cone 6), dark stoneware (10), light stoneware (10), and porcelain (10). Nearly all of our students use the high fire clay bodies.
Finally my Ceramic Engineering degree can be put to good use! Actually it already has…
To address the really, really high temperature question…it obviously depends on the composition. If the material has any free silica (a=oxide) it would vitrify. That is, form a glassy phase that would melt into a puddle. Toilets are vitrious sanitaryware. they have a high glass content that seals the surface to keep out nasty bits. If the ceramic is of a composition that does not vitrify, it will continue the process that started during its initial firing: solid state sintering. It’s a process where heat causes the crystal structure of the material to vibrate/move and connect/ reconnect with nearby crystals. A clay pot is a simple example of this process. If you keep heating, you;ll keep sintering until you have a solid crystal (with a lot of defects). Basically it a fuses into a big chunk. It’s not ogin to melt or explode or vaporize (unless it does. Chrome Oxide will sublimate at high temperatures).
Thanks for joining in. Cool degree.
But if you keep cranking up the temp well above what a real-world kiln will produce what then? After the sintering process runs its course?
It would certainly vaporize at some point (2950°C for SiO2; 2977°C for Al2O3).
If it contains significant Ca and C , you could end up with Calcium Carbide… CaC2
Now if you throw that into water near a naked flame…
it makes C2H4 , acetylene… high energy and explosive (in fact, no naked flame needed, its rather sensitive)
However you’d have to be specifically intending to make Ca2C because it vaporises at 2300 C.
A rare earth carbide might melt at 3000 C and boil at 5000 C.
So if you cook pottery, you may end up with ash- salts (or metal non-metal covalents), such as chlorides, and metal carbides …
No, because part of the (lengthy) intaglio on the cup would read “Not For Use On The Surface Of The Sun.”