High temperature displacer

[Tom Booth]

I put all the big pieces of silicon carbide back in the oven.

Without the clay pot, just loosely covered with some insulation, more to protect the microwave from the heat than anything, the pieces heated up to over 1100°F easily in a few minutes.

Resize_20230324_035239_9417.jpg (184.82 KiB) Viewed 1969 times

So I don't think the big kiln was too much for the microwave to handle, just the big clay flowerpot.

[Tom Booth]

I've been reviewing available information about foamed glass and foamed ceramic in preparation for using the kiln, which I'm going to need to do over.

Anyway - in the process I came across this:

https://marjanvanaubel.com/foam-porcelain/

A foamed porcelain recipe and methodology leaning towards the artistic as well as practical.

I don't particularly see anything all that novel to justify a patent. There is a claim that no foaming agents is required, but the ingredients listed include several gas generating materials, when heated, the most common being simply water.

The patent ("abandoned"), however, reviews and references prior art that might also be interesting and also demonstrates the wide variety of possible ingredients and formulations possible.

US20150018195A1
United States
https://patents.google.com/patent/US20150018195A1/en

Some excerpts:

This results in a strong, hard, lightweight and transparent porcelain-type ceramic material featuring a macroporous, foam-like structure and a smooth Surface, that can be applied in a variety of decorative and practical purposes. ... (Also...) The foamed porcelain-type ceramic is further characterized by being fireproof and thermally insulating...

Video of the foamed porcelain expanding in a kiln:

https://youtu.be/fkUYyKNuAVc

[Tom Booth]

Looking for foamed glass recipes I came across some videos about "elephant toothpaste".

With some refractory and maybe Portland cement, perhaps glycerine instead of dish soap who knows, experiment, but looks like potentially a quick way to experiment with different formulations in small batches to make up a bunch of foamed cement without needing to use any kind of foam generating machine.

https://youtu.be/Kou7ur5xt_4

[skyofcolorado]

Looking for foamed glass recipes I came across some videos about "elephant toothpaste".

With some refractory and maybe Portland cement, perhaps glycerine instead of dish soap who knows, experiment, but looks like potentially a quick way to experiment with different formulations in small batches to make up a bunch of foamed cement without needing to use any kind of foam generating machine.

After futzing with all manner of alternative foaming agents, I finally bought a jug of Drexel 160 to use with lightweight concrete, plaster, and other formulations. Works great every time and it's not necessary to use a foaming machine for small quantities. Just whip it with a drill and a loop of wire. Makes a very fine foam that lasts plenty long enough for most mixes to set.

[Tom Booth]

Looking for foamed glass recipes I came across some videos about "elephant toothpaste".

With some refractory and maybe Portland cement, perhaps glycerine instead of dish soap who knows, experiment, but looks like potentially a quick way to experiment with different formulations in small batches to make up a bunch of foamed cement without needing to use any kind of foam generating machine.

After futzing with all manner of alternative foaming agents, I finally bought a jug of Drexel 160 to use with lightweight concrete, plaster, and other formulations. Works great every time and it's not necessary to use a foaming machine for small quantities. Just whip it with a drill and a loop of wire. Makes a very fine foam that lasts plenty long enough for most mixes to set.

Thanks, I might try it, but at $50/gal I'll probably be trying the yeast and peroxide first (mixed with clay, cement or whatever.)

Yeast is only 3 packets for $1 and feed it some sugar you can even grow your own. Peroxide is $1 / qt and probably only need a teaspoonful. Maybe wishful thinking though. Cement or clay might neutralize the reaction between the peroxide and yeast.

I'm also thinking this process is pretty highly exothermic generating a lot of heat, which I'm hoping would help the foamed concrete to set quickly.

Also the foam is generated by the release of oxygen internally on a molecular level. That should produce a very uniform cell structure, as seems evident from the various "elephant toothpaste" videos. The expansion ratio seems very good while maintaining a fine but dense cell structure, by all appearances. The reaction is also controllable, which is not quite as easy with a premixed formula.

Also, the foam generated would be due to an internal reaction, rather than depending on folding the foam into a separate cement mixture, just pour in the activator and stand back. I like the nearly instantaneous results.

I imagine by combining the elephant toothpaste with a self setting cementitious element instant concrete sculptures could be produced.

Anyway, it looks like it could be a lot of fun, if it works. I actually just got back home a few minutes ago after driving around shopping for yeast and peroxide.

[Tom Booth]

As of now, your good advice stands skyofcolorado. In trying to reinvent the wheel, my results are pretty horrific so far:

Resize_20230326_083725_5150.jpg (323.06 KiB) Viewed 1920 times

Resize_20230326_083724_4015.jpg (334.83 KiB) Viewed 1920 times

At the initial foaming up stage the method seemed promising but with such a high water content, failed to set or hold its shape as it very very slowly started to, but never really dried.

I have not tried Portland cement as yet. The above was a concoction of refractory cement, kaolin clay with some glass microspheres and some "Insuladd" thrown in, along with some squirts of vegetable glycerin and a little sodium silicate blended up into a slurry with hydrogen peroxide,... Then the warm yeast water added in and stirred up a bit.

It foamed up OK but stayed wet, eventually crumbling or cracking.

Putting some in the microwave and heating it up a bit, it foamed up like crazy, but collapsed back down almost immediately.

If the foam had held its shape any length of time I might have tried firing it in a kiln (that has yet to be constructed (or rebuilt), but of course, never got that far.

Even after drying overnight, part of the time in the conventional oven on very low heat, the stuff is still just mushy and damp.

[Tom Booth]

I got to thinking that the method for binding the silicon carbide into a strong hard shell worked so effectively, it is even relatively lightweight:

Resize_20230326_113942_2921.jpg (172.88 KiB) Viewed 1916 times

But probably not really lightweight enough. Could be lighter anyway, but just about perfect. Certainly fireproof.

So I thought, maybe the same method would work using something fireproof but lighter weight than silicon carbide.

I have bags of Perlite and vermiculite sitting around just for such an occasion, and I already had some water glass and water solution mixed up in a spray bottle (bout 30% "laboratory grade" water glass to 60% distilled water).

So I smeared a flowerpot bottom plate with a little petroleum jelly to make a sticky surface and sifted some vermiculite and perlite, in alternating layers over that. Giving them a spritz of water glass between layers and gently pressing it down with a flat jar lid after each layer to compact it a little:

Resize_20230326_113940_0775.jpg (193.8 KiB) Viewed 1916 times

I'm trying to cure/dry the product in the oven, gradually increasing the temperature. I did the same thing with the flowerpot kiln to dry it before putting it in the microwave.

Not sure what I'll do to heat treat this thing after it comes out of the oven...

Resize_20230326_113942_2036.jpg (149.64 KiB) Viewed 1916 times

Edit: one change in methodology was to use Vaseline rather than water the first layer. I had a difficult time with the silicon carbide getting it to stick to the wet flower pot, then some added difficulty getting it loose after heating in the microwave. The petroleum jelly certainly made a nice sticky surface. Hopefully it will let the "displacer" come loose easily afterwards.

[Tom Booth]

As far as the vermiculite goes that was a total fail, it did not even begin to hold together after drying in the oven to over 500°F

The thin layers of sifted Perlite however (screened at about 180 grit size) looks pretty good considering. The layers of perlite were very thin, inconsistent and partly mixed with vermiculite.

Perlite powder and water glass displacer

Resize_20230326_141956_6016.jpg (177.21 KiB) Viewed 1911 times

Resize_20230326_141956_6819.jpg (161.72 KiB) Viewed 1911 times

Quite a lot of the perlite sandwiched between layers of vermiculite held together nicely, and is strong enough to handle, but the vermiculite just crumbled.

So why the difference?

My theory is that the vermiculite is more porous and basically absorbed all the relatively weak water glass solution it came in contact with so the waterglass couldn't act as a very effective "glue".

The Perlite on the other hand is much more glass-like so the waterglass stayed on the surface binding the particles together much better.

[Tom Booth]

Flame testing the new material:

https://youtu.be/x_pFJorX5ZE

I got the idea of seeing how well this stuff could hold up to sudden extremes of temperature.

Held upsidedown "canned air" or "duster" produces some really cold below freezing temperatures.

However, I did not realize it was also extremely flammable, and gives off a nasty toxic (probably) acrid stench when burned. The Perlite/waterglass material is, on the other hand, completely odorless when heated and I believe, completely non-toxic afaik.

https://youtu.be/PA_w1Fao4fg

[Tom Booth]

I was browsing/searching the internet to see if there are any really fireproof paper products available on the market.

Some "fire resistant" stuff, basically meaning; treated with fire retardant, but still burns and turns black under direct flame.

There was one pretty old article about a fire and water resistant paper invented by scientists in China, but the material was rather exotic I think: "hydroxyapatite nanowires"

Certainly there must be something out there?

Anyway, I came across this video which apparently shows a relatively easy and inexpensive way to make a nearly fireproof paper from ordinary newspaper pulp baking soda and plaster of Paris.

The video also says a little vinegar, but in the comments he says, on further testing the vinegar is not necessary. Also the paper will eventually burn, but can apparently withstand the heat of a welding torch for an impressively long time.

Paper making is actually rather easy, from recycled paper and rags. I may just try making some extra lightweight extremely fireproof paper tomorrow using more conventional paper making methods rather than what I did this morning.

https://youtu.be/3I3zHe-eDS8

Lots of videos on making paper. Here's one that basically shows the method I'm familiar with.

https://youtu.be/rn9UsSafWHI

So,... My plan is to add some Perlite, probably some ceramic blanket fibers for extra strength, the baking soda and plaster of Paris, seemed to work well (I might just test that first), and who knows what else, might add some waterglass to the slurry, or spritz it on after.

I'm thinking for a displacer, maybe put layers of this fireproof paper together to make something like corrugated cardboard.

Fire it up in a kiln and maybe glaze it with some crushed colored glass for extra strength on the outer surface, as well as making it look decorative.

[Tom Booth]

I decided to see how the Aerogel blanket insulated engine would do on the 100 watt ceramic heat lamp.

It was really banging away, and the displacer, rather than hopping around at the bottom of the chamber started almost hovering around at the top.

I thought I'd get a video of this odd displacer behavior with the very high heat. I was starting to smell the odor of glue/plastic burning.

By the time I grabbed my phone, the engine only ran a little while longer before it came apart.

Somewhat remarkably I thought, it continued running for a while even with the seal holding the bottom plate on seriously compromised.

https://youtu.be/WCNsmE-Evbc

I put this here because it illustrates the need for high temperature materials in building a Stirling engine.

Remarkably this little magnetic LTD seemed quite capable of utilizing the relatively high, sustained heat of the 100 watt ceramic heater without "overheating", even with the sink covered by a Aerogel blanket.

It was just the glue/plastic that failed, not the thermodynamics of the engine.

The engine ran like crazy for maybe about 5 minutes before the glue holding it together failed.

I had actually wanted to take one of these engines apart anyway, and coat the inside ceiling of the displacer chamber with hollow glass microspheres for one more layer of insulation on the inside to prevent heat escaping to the "sink".

[Tom Booth]

Wow, I hadn't noticed before, but rewatching that video, I heard a strange sound, like a sneeze or something, but I was pretty sure that wasn't me sneezing. So I watched a few more times.

The knife I took out of the sink apparently had some drops of water on it, so when I used it to separate the bottom metal plate from the engine, the water touching the bottom of the engine sizzled and even produced a puff of steam that can be seen in the video.

I had not realized the bottom of the engine had gotten quite that hot.

It had also been laying there after being taken off the ceramic heater for a minute or two before the wet knife touched it, so that thing must have been really really hot.

The engine, where I picked it up, on the top and sides did not feel hot at all.

[Tom Booth]

Here goes;

I picked up a few items:

A cheap blender, some needlepoint hoops, and some paint straining cloth.

Resize_20230402_224045_5422.jpg (174.13 KiB) Viewed 1833 times

Resize_20230402_224044_4299.jpg (179.97 KiB) Viewed 1833 times

Other materials I already had; some ceramic fiber blanket, Perlite, waterglass, plaster of Paris, kaolin clay powder and baking soda.

I cut a piece of ceramic fiber blanket up into smallish pieces (but not too small, I want it for the long fibers) and put it in the blender with some water. It blended up much better than I had anticipated, just about as well as cellulose fiber, staying suspended in the water.

I started out with just about a cup of water but had to keep adding more as the fiber separated and expanded:

Resize_20230402_224041_1875.jpg (272.1 KiB) Viewed 1833 times

Then I added about an equal part sifted Perlite, and about a tablespoon each of the powdered clay plaster of Paris and baking soda.

Also about an ounce of waterglass, right into the mixture.

Blended it all up, poured it out into a bowl and scooped up a portion with the strainer cloth stretched out in the needlepoint hoop

Resize_20230402_224043_3069.jpg (289.95 KiB) Viewed 1833 times

I think it's looking pretty good so far.

I'm starting out with just a very small (about 3 inch diameter) hoop and small batch of "paper" mush to see how it goes.

There is no real rhyme or reason to the proportion of the ingredients, but have to start somewhere.

[Tom Booth]

I used this lace border, instead of the paint strainer for the little test, partly because I wanted to see how it would take a watermark.

Resize_20230403_023802_2944.jpg (188.42 KiB) Viewed 1824 times

The stuff (potential mini test displacer) came out of the form OK after it dried. I was extra careful and loosened the screw on the frame and pressed the displacer out of the form with the rim of a drinking glass that just fit inside.

Resize_20230403_024750_0265.jpg (162.48 KiB) Viewed 1825 times

Seemed still rather fragile to me, so I also gave it a few sprays of the stronger waterglass solution.

I've got it baking in the oven. It is much thicker than the previous Perlite "paper" and not very paperlike at this point. More like a light weight but very hard, almost glass like ceramic as far as I can tell from the minimal handling I've done so far just shifting it around and turning it over in the oven.

Resize_20230403_023804_4923.jpg (159.39 KiB) Viewed 1825 times

Hopefully, as can be seen in the photo, it took the "watermark" impression from the lace quite nicely

[Tom Booth]

Well,... It's getting there, but far from perfect. Not satisfactory even, really.


https://youtu.be/4plspDShI-g


I don't like the black soot. Not sure what is causing that.

The Perlite alone doesn't turn black. Not the ceramic fiber either, by itself.

I suspected the baking soda but that didn't turn black under the torch flame either surprisingly. I did discover something else interesting though in the process of testing.

Apparently baking soda lowers the melting point of perlite.

I first tried torching perlite to see if I got a "bad batch" or something. It stayed white. Then I dumped out some baking soda to try that.

Well the baking soda stayed white, but the Perlite and baking soda melted together into a puddle and formed a kind of white sort of plastic substance.

Resize_20230403_043638_8344.jpg (197.35 KiB) Viewed 1816 times

The displacer also retained quite a lot of heat for a rather long time as compared with either perlite or ceramic fiber blanket, both of which cool off and can be handled almost immediately after being heated red or white hot.

It was also still quite fragile and broke into pieces fairly easily. Something between an cookie and an egg carton, not actually hard like foamed glass, but very light weight at least, and very fire resistant.

Maybe the plaster of Paris?

I thought that was commonly used as refractory.

The kaolin clay powder?

Maybe something formed by the combination of materials.