I thought this would be a simple Google/Wiki search but either I suck at it or it’s more elusive than I predicted.
Tungsten is the most heat resistant element with a melting point of 3422 C (6192 F). So what’s the most heat resistant man made material that we know? Is it a ceramic? Some exotic alloy? Maybe a combination thereof? Any speculation on future technologies in this area?
The key word for Googling is “refractory”.
This page (and Wikipedia) both suggest that zirconium oxide is the most heat-resistant commonly used ceramic, but its melting point is around 2700ºC, considerably lower than that of tungsten.
Ask A Scientist says that diamond has the highest known melting point, at about 4000K (~3700ºC) ± 200. That’s almost on a par with strawberry Pop Tart filling after 90 seconds in the toaster.
However, this page says that graphite has a higher m.p. (actually it sublimes) than diamond.
Either way, it’s pretty darn toasty.
Edumacate me please.
Define “heat resistant.”
Does it simply mean “having a high melting point”?
Or does it mean, “reflects much of the heat around it, thus staying cooler than many other materials would”?
Or are those the same thing (I’m pretty sure not)?
Sorry for the third reply, but here’s more on carbon, with the snippet that “carbon has the highest melting/sublimation point of all elements. At atmospheric pressure it has no actual melting point as its triple point is at 10 MPa (100 bar) so it sublimates above 4000 K. Thus it remains solid at higher temperatures than the highest melting point metals like tungsten or rhenium, regardless of its allotropic form.”
[QUOTE=bup]
Edumacate me please.
Define “heat resistant.”
Does it simply mean “having a high melting point”?
Or does it mean, “reflects much of the heat around it, thus staying cooler than many other materials would”?
Or are those the same thing (I’m pretty sure not)?
[/QUOTE]
Me again… :o
Well, it’s not that the material will stay cooler, just that it will remain unaffected by the heat. So it mustn’t melt, obviously, but also mustn’t decompose, or react with the air, or whatever. So you would use different materials depending on what they were going to be in contact with at high temperatures. Some will react with oxygen, some will react with acids, and so on.
Here’s a brief article on tiles used on the space shuttles.
http://science.howstuffworks.com/question308.htm
They’re made of silica and have amazing insulation properties.
[QUOTE=Colophon]
Sorry for the third reply, but here’s more on carbon, with the snippet that “carbon has the highest melting/sublimation point of all elements. At atmospheric pressure it has no actual melting point as its triple point is at 10 MPa (100 bar) so it sublimates above 4000 K. Thus it remains solid at higher temperatures than the highest melting point metals like tungsten or rhenium, regardless of its allotropic form.”
[/QUOTE]
I always wondered about that. I’d never heard of liquid carbon at any temperature under normal pressures, and now I know why! 
[QUOTE=bup]
Edumacate me please.
Define “heat resistant.”
Does it simply mean “having a high melting point”?
Or does it mean, “reflects much of the heat around it, thus staying cooler than many other materials would”?
Or are those the same thing (I’m pretty sure not)?
[/QUOTE]
No material “reflects much of the heat around it, thus staying cooler than other materials.”
All materials at equilibrium with their environment are the same temperature as that of the environment.
However, materials have different thermal conductivities, which affects their behavior with respect to heat transfer.
For example, metals generally have a much higher thermal conductivity than wood or brick. This means that metals conduct heat more readily. This is why a large hot piece of metal feels hotter than a piece of wood at the same temperature. Your hand is cooler than the piece of metal, so heat flows from the metal into your hand, but because the metal conducts heat so readily, heat flows from the rest of the metal into the spot you are touching. In effect, your hand has to cool off the entire mass of metal before it stops feeling hot.
With a piece of wood, your hand cools off the spot you are touching, but because wood has a low thermal conductivity, heat does not readily flow from the rest of the wood to the cool spot, so the wood feels cooler to you.
(This is also why a large cold piece of metal feels colder than a piece of wood at the same temperature, which is also why you should not stick your tongue to a cold metal flagpole.)
Materials with low thermal conductivity (and a high melting point) make good heat insulators, and such materials are used for refractory brick, space shuttle tiles, etc. In these cases, only one side of the material faces the heat source. You therefore end up with a sharp temperature gradient from the hot side to the cool side.
OK, thanks. Now, then, what is the OP asking for? The best insulator? Or the highest melting point?
I was quite interested by this post so i decided to do a little research, as of 2010, since the discovery of “the 2d crystal”, it has come to my attention that the strongest crystaline substance known is a variation of carbon, known as graphene. This is currently the strongest material known, with a hardness rating of 10 (same as diamond) so, i thought to myself, why cant it be the most heat resistant?, as it turns out, and as far as i know at the moment, it is, with a melting point at a staggering 4900K or approximately 4,610 Celcius. das hawt.
Getting my BS in Ceramic Engineering we would have an annual open house in the department. We had a small cube of the “Space Shuttle Tile” silica you are talking about. The stuff is indeed amazing. We would demo it for people by putting it in a small furnace, heating it to glowing (~700 C), take it out with tongs, place it on the work table and then pick it up with bare fingers (by the corners).
The material was still glowing, but it transferred heat so slowly it wouldn’t’ burn your fingers. Very impressive demo.
Also worth noting that while carbon has a very high melting point, it will burn at a lower temperature (~1000°C) with enough supplied oxygen. Lavoisier demonstrated this in the late 1700s and there are YouTube videos of diamonds burning in liquid Oxygen.
I would assume that what the OP wants to know is what stuff will best protect whatever is on the other side of it from intense heat on one side. As such, being a good thermal insulator is going to be as important or more important than having a high melting point. Tungsten and carbon may have very high melting points, but they conduct heat rather well, so even if they don’t melt, whatever is on the other side is still going to get hot quite quickly. This why ceramics are frequently used for heat protection, such as the space shuttle tiles and the zirconium oxide mentioned in post 2. Their melting points may not be teh highest possible, but they protect from hat a darn site better than some things that are more resistant to melting. (They generally are also fairly resistant to chemical decomposition or other reactions caused by heat, unlike carbon, even in the form of diamond, which burns in air quite easily.)
Supposedly, there is this stuff, some form of plastic, called Starlite, which has incredibly heat resistant properties, being both an amazingly good thermal insulator and very resistant to melting and chemical breakdown. Unfortunately, however, it has all the hallmarks of being a hoax. Supposedly it was invented by an amateur chemist, who (probably) took the secret formula for making it to his grave. :rolleyes:
Hafnium carbide and tantalum hafnium carbide, since both diamond and graphite are not practical for lining furnaces.
Since we live in an atmosphere full of oxygen, what’s the most heat-resistant substance that won’t burn (or show accelerated corrosion) at high temperatures?
Platinum might be a good bet for that. It doesn’t melt until 1768 C, it’s a “noble metal”, and it also has the advantage of being very lustrous, which will mean that it reflects a lot of radiant energy, and so will heat up slower.
^
A rare earth metal. It wasn’t around when the term “noble metal” was ‘coined.’
Rare earth refers to the Lanthanide elements. I believe “noble” has by extension been granted to more recently discovered metals that have the property of being non-reactive under normal conditions.