Ceramic Question
Ceramic Question
(OP)
I'm looking into ceramics for a high-temperature (up to 2000-deg C) high resistance application (resistance = heat). Are there ceramics that I can apply a current to (not quite sure how much power I will have available, but it should be pretty high) and have it generate enough heat to get up to 2000-deg C? I see that something like alumina loses resistivity as the temperature goes up, is that common for ceramics? Lowest temperature I need will be 650-deg C, but if I can get up to 2000, that would be better. Thanks.





RE: Ceramic Question
RE: Ceramic Question
Silicon Carbide and Molybdenum Disilicide are used for heating elements and are about the only thing readily available at a reasonable cost.
http://www.isquaredrelement.com/
RE: Ceramic Question
RE: Ceramic Question
Myself and other members will help if a little more information is given so others can contribute.
What shape do you need?
Working atmosphere?
Duty cycle?
Any Other information laying around.
RE: Ceramic Question
RE: Ceramic Question
The rest of this note assumes you are in an oxidizing atmosphere. Metallic heating elements can reach element temperatures up to 1400 C. Silicon carbide will get you to about 1625 C. The moly disilicide is good to about 1850 C. All these elements are protected by growing an oxide film at high temperatures. Changes in oxygen partial pressure can have a dramatic effect on element life. If you truly need to get to 2000 C, consider using zirconium oxide which will work well as an ionic conductor of oxygen above 600 C. This means you have to get the element to at least 600 C before you can get enough power through it to begin heating. Ultimate element temperature is on the order of 2100 C.
I have talked about element temperatures here. In a furnace environment it wouldn't be unusual to see the environment temperature a couple hundred degrees less than the element temperature.
Bruce
www.accuratus.com
RE: Ceramic Question
RE: Ceramic Question
As an aside, I have used Kanthal heating elements for many years and find them consistently high quality.
Bruce
www.accuratus.com
RE: Ceramic Question
RE: Ceramic Question
Bruce
www.accuratus.com
RE: Ceramic Question
RE: Ceramic Question
Bruce
www.accuratus.com
RE: Ceramic Question
RE: Ceramic Question
RE: Ceramic Question
RE: Ceramic Question
Bruce
www.accuratus.com
RE: Ceramic Question
RE: Ceramic Question
Here come my technical comments: the problem should be more clearly defined from the physical point of view. First of all, the only solid restrains I can read is the total awailable power of 13 kW ready to be dissipated and on top of it a desire to achieve certain minimum temperature level. This is not even close to any physical description of the system if nothing is said about heat transfer conditions. Here we also have to specify the regime: is it steady-state or transient (here heat capacity issues will kick-in). Also, do not ignore the electric power transfer issues: current & voltage of the source has to match the heating element.
The bottom line is: let's try to help each other but let's strive to build-up some kind of engineering discipline while describing the problem.
Slawomir
www.pkerengineering.com
RE: Ceramic Question
RE: Ceramic Question
Slawomir
www.pkerengineering.com
RE: Ceramic Question
RE: Ceramic Question
RE: Ceramic Question
Bruce
www.accuratus.com
RE: Ceramic Question
RE: Ceramic Question
RE: Ceramic Question
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RE: Ceramic Question
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RE: Ceramic Question
h-bar = (power (watts)/area (m^2))/delta-T
where delta-T is calculated as some theoretical maximum minus the theoretical ambient temperature (say 1273K - 293K).
I appreciate all the help you have given me in trying to figure this problem out. Like I said, one thermo class seven years ago and I haven't used it since. These forums have proved to be a valuable resource for someone who really has no idea what they are doing.
RE: Ceramic Question
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RE: Ceramic Question
density
thermal conductivity
specific heat capacity
emissivity
Thanks again for your assistance so far.
RE: Ceramic Question
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RE: Ceramic Question