Tungsten: highest melting point related to asbestos cleavage planes??

Wondering if there is some connection with cleavage planes and heat resistance. As per asbestos is highly heat resistant and has cleavage
planes. Whether those cleavages is responsible for the heat resistance of asbestos in some manner.
And whether tungsten has some sort of cleavage plane that accounts for its high heat resistance.
No-one has answered the question of at what temperature asbestos melts, given that tungsten melts at 3410 degrees C.
So is asbestos the lightest and least dense material with the highest melting point? And why does cleavage contribute to its heat resistance? And then, the important question is whether we can discover a even greater cleavage material that is even better at heat resistance than is asbestos.
Archimedes Plutonium, a snipped-for-privacy@hotmail.com whole entire Universe is just one big atom where dots of the electron-dot-cloud are galaxies
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Is a cleavage plane used in breast reductions?
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Archimedes Plutonium wrote:

Dale Trynor wrote: Long time ago I did melt a bit of it with an oxyacetylene torch and it didn't seam that difficult. My handbook shows it as Serpentine 3MgO2SiO2.2H2O. Because asbestos usually has some water in it, it gains an advantage in that this will help prevent the temperature from rising much until all the water is used up and or given off, that is of course providing that it hasn't already been heated and lost this water content. MgO or magnesium oxide dose have a rather high melting point of about 2,800 C and a boiling point of 3600 but dispite the high boiling point you should know that it tends to sublime rather easily. SiO2 melts at 1,710 C but other forms are listed with lower melting points for whatever reason ?. Hafnium oxide is especially good at 2812 C and I have been told is far less prone to evaporate i.e., sublimation. Thorium oxide is about the best of the oxides with a really good 3050 C melting point and a nice high boiling point of 4400 C and has been used in gas mantel wicks for a reason.

I believe there is a tantalum, hafnium carbide that melts at over 4000 C and it was mentioned in a rather old encyclopedia so one suspects better records for more up to date research.

Probably not but because its cheap it was used a lot.

Probably not but because it breaks up into fibers it becomes a better insulation. Remember that most insulation's work because they keep air from convicting and its the lower thermal conductivity of the air itself that provides the main part of the insulating effect.

Foams and or similar to the shuttle tiles however I believe they are silica and so should melt rather easily. The best idea for high temperatures would probably be a solid foam made of thorium oxide if it could be made.

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Wed, 17 Sep 2003 08:05:44 GMT Dale Trynor wrote:

Thanks for the information. Which leads me to a next question. It appears from you writing above that a solo element does not have the superlative record for heat resistance but rather instead a oxide compound. And involving transition metals around hafnium, tungsten, thorium etc. What is in the chemistry of these transition metals to explain why they have such high heat resistance?
Archimedes Plutonium, a snipped-for-privacy@hotmail.com whole entire Universe is just one big atom where dots of the electron-dot-cloud are galaxies
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I think one factor is the large atomic mass [takes a lot of energy to vibrate them, ie melt} of Tungsten. Many of their oxides have a large heat of formation [ie lots of bond energy between the metal and oxygen, so hard to break it apart]. Just my chemists hand waving... -J
Which leads me to a next question. It appears

entr0pyf0e
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Dale Trynor wrote:

[Archie.... your question is interesting, but you are barking up the wrong tree. Nice question though.]
Graphite.....
The Germans used graphite steering vanes in the V-2 engines as nothing else could take the high temperure, and it would have been too much engineering to try to add liquid (fuel) cooling to the steering vanes.
Graphite, as some of you know, has easy cleavage along the basal plane.
It is the most anisotropic solid known to man with Young's modulus of over 160 Million Psi in one direction and only a paltry few million perpendicular to the basal planes.
The shear modulus between basal planes is only a half a million Psi....
So in one sense, one direction of elasticity is over three hundred times stiffer than another(300X).
Mica is relatively isotropic, by comparison. I've lost the numbers, but the equivalent ratio for Mica was only about 30 or so.
Mica is a relative isotropic material compared to graphite.
I used to enjoy pestering the "official" graphite experts with why is is that a substance held with low enegey bonds, Van der Waals bonds, in the "c" direction is the most refractory solid we have..... in the absence of oxygen that causes it to combust, that is.
None of them was ever able to answer the question.
I was mean enough not to give them the analogous examples from other branches of elementary chemistry.
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