Stirlingengineforum.com

I report discussion made by Vile_fly with information of Ian, and mine from other topic.
I think is an important turning point
Quote ////
Re: another displacer material--aerogel.
Postby Ferraccio » 12 Mar 2012, 14:12
I found very good material: is Rescor 740.
Is very hot resistant: 1250 celsius degrees, quite good mechanical performance, very light (0.65 kg/dm3) , is a cold-casting foam.
I suppose is expensive, I think was the used for the Space Shuttle tiles.
Is commercialized, perhaps is small quantities.
Ferraccio

Re: another displacer material--aerogel.
Postby Ferraccio » 12 Mar 2012, 19:44
about material:
http://www.cotronics.com/catalog/59%20%20740.pdf
Ferraccio

Re: another displacer material--aerogel.
Postby vile_fly » 15 Mar 2012, 03:54
Thanks for the link, Ferraccio. These newer ceramic materials are better than what I had found, and priced better, too. The idea of casting foam ceramic is very appealing, and cost effective.
The boron nitride lubricant that Cotronics.com sells also caught my eye.

1500°F Boron Nitride Spray on Coating and Lubricant
"Rescor 112 has excellent electrical insulation, high thermal conductivity and is a superior high temp lubricant. It is inert to most molten metals, glasses and salts and can be used continuously to 1500°F in air and to 3600°F in an inert atmosphere.
This unique combination makes for an ideal high temp. lubricant, mold release and electrically resistant coating. Applications include mold release, lubricant, barrier layer and as an anti-splatter compound."
vile_fly

Postby Ferraccio » 15 Mar 2012, 09:21
......
Rescor 740 can be worked (filed, machined, drilled and milled),
There are other Rescor ceramics, cold moldable, solid, very high high features, with (instead) good thermal conduction.
Ceramic materials and not-oil lubricant are THE condition to make an high performance engine, pressurized.
Very well!
This is an important turning point, thanks for your indication on lubricant. and other.
////Unquote
Ferraccio

The material is proposed low weigh not conducing for displacers.
Ferraccio

What I think would be interesting use of ceramic......casting a stirling engine block with regular castable ceramic, use castable foam ceramic for the displacer, a ceramic filter for the regenerator, and possibly a graphite power piston. All of this might be possible with the high temp boron nitride lubricant or without it, for that matter. The ceramic dust generated from wear may be an issue, so dissassembly after a break-in period may be needed to clean it out. The hot head and cylinder will probably still be stainless steel or cast iron for thermal conductivity reasons.
What I am unsure of is the viscocity of the lubricant. Is it a dry film or a moist liquid? I suspect it is a dry film....but am not certain of it.

I also found a 1200'F stainless steel paint that looks promising for coating the ceramic foam to keep it from flaking away under vibrational movement. Might even be used as a liner material for a ceramic cylinder, but I think that is pushing it a little far.

Here are other interesting coatings a materials with a price list, too. The rescor-112 high temp lubricant is $53.75 per can. There is also a brush-on teflon coating they sell, Duralco T507, good for 500'F. http://www.cotronics.com/catalog/37%20n ... 206105.pdf

I suppose that boron ritride "exagonal" (said white graphite) as lubricant, may be is a powder.
I think is improbable that is a liquid.
Good notices vile fly, now I carefully translate ...

I found a very cheap supply of aerosol boron nitride powder as well as raw bulk powder. $15.00 per 13oz can. here is the link: http://www.lowerfriction.com/product-pa ... egoryID=24# The powder is available from 5 micron to 70nm form. It ranges from $54.00 to $108.00 per pound, depending on micron rating. 1LB yields 198cc of material.

After looking up its properties, I concluded that it can be mixed with castable ceramic, making it self-lubricating like cast iron is. This would excellent once the proper ratio is determined by experimentation. I wonder if it would make the cured ceramic more machinable?