Okay it appears there are a few brief aftershocks

Never mind it restarts around 9:00 better keep the volume down the whole video.

That's what the lime is for, to add that extra calcium.

Theoretically yes. But they would probably be pretty lousy. That having been said, I might try it and see just how well (badly) they work.

The mixture does have to be compressed while it is curing, otherwise the heat/water produced during the reaction seems to cause voids to form which affects the cohesion. I usually apply some weight on top of the mixture before adding the water. It also helps if the container you use for the mold has the ability to let water soak through. The faster the water can get into the mixture the better the result. If you cannot though, then the mixture should be submerged in the water for up to 24 hours to ensure it reaches all of the mixture.

That depends on what you mean by high temperature. Calcium in it's oxidized state is not volatile at high temperatures. The upper limit of the stability is going to be limited to the melting or decomposition temperature of the cation used. Phosphate is surprisingly stable.

Thanks!

These are all extremely good points. I had thought of trying to take care of the remaining calcium hydroxide with a bath of dilute phosphoric acid but the diffusion time would be very long. Also a good point regarding using it outdoors with exposure to rain.

Yes. I have been experimenting with that and it does work. You have to change the ratios of the phosphate to lime.

I have not. My main goal here was the make something that had the least amount of fiddling with chemical reactions. I have thought about trying to add some aluminum oxide to improve the high temperature limit.

I would say there is no comparison. This is meant for very high temperatures and the plaster of paris will dehydrate and loose it's cohesion at higher temperatures.

I think that is worth trying. Thank you for the suggestion.

I'm working on an electric furnace using this as the insulator. A functional forge is definitely up there on my list as well. I've been occupied revamping my workshop which will hopefully be done by August and then I will have a lot more capacity to do neat things like that.

Audio distortion? I'll check and see if I can clean that up.

Thank you for the comment. It is a good point.

Thank you. I would be interested to know how that works for you.

Well you are in luck because hydrated lime is Calcium Hydroxide, so you can use the same proportions.

يصلب هذا الخليط بسرعة كبيرة. أنها لا تحتاج إلى الموثق. أستخدم الورق المقوى للدعم عند التصنيع. يرجى عذر أي أخطاء الترجمة. شكرًا لك.

Yes, there are circuits that use SPI or I2C which can reduce the number of pins needed. But at the same time, it's fun to figure out how to accomplish this with simple components.

The refractory is 3.7 grams of Ca(H2PO4) for every 1 gram Ca(OH). I then mix equal volume of the refractory and powdered perlite. I hope that helps.

You mean the precursor that I use? I just buy it since it's a common fertilizer/farm animal supplement. I have no idea how to make it.

Well thank you! I was considering MgO since that's not too awful to source. If I recall right the big issue was that exposure to moisture was going to be a potential issue as the MgO would convert to Mg(OH)2 and back to MgO when heated. I imagine the volume change would cause a lot of spalling in the ceramic. SiO2... maybe you meant Al2O3? Silicon dioxide melts well below what Calcium phosphate can withstand. I have considered trying to use some alumina sand blasting powder as a surface treatment but have not gotten around to trying it.

@@Drjtherrien Intention to inform. Aluminium powder will induce bubbles when mixed into the mix. As soon the phosphates are leached out with the water the phosphoricacid formed will attack the aluminium and then produce pores. A standard recpie is: 1 : 0,6 parts and some water to get going Wollstonite + Phosphoricacid 40-60% (the higher the content the longer the acid will nagg at the silicate and wont get hard. The reaction goes on for days when not weeks we stoped the experiment after 4 days by just mixing in 30% water. The idea of the water is that it functions as a ion-transferfluid. Then can the free ion exchange between the substances and form a new group) 1. You ad 80g Wollstonite to a 200ml container, the stuff will foam up about 3x its volume and then go back 2. then ad some water and mix that to a very thick slurry. As thick as possible. You dont want a very high water content in the mix because that makes the drying time longer and the result more brittle. 3. Then you ad the phosphoricacid to the paste and stirr it very good, dont spill it over, it will foam up very. The colder the water used the less bubbles will be formed. When you add aluminiumpowder it will form bubbles to. 4. now we are entering the casting phase, when the bubbles go away you have about 30 seconds to cast the stuff. You will get a foamy ceramic like concrete. That insulates extremely well. You can pour the part into a foam and then inducing it to a vacuum chamber and getting the bubbles out, when the vacuum can be formed fast enough. Maybe by adding borax it will be longer fluid. But i would have to test that to. When you add some flyash as filler you have a +-2000°C refractory cement. You can also take metakaolin and mixing potassium waterglass in it BUT the silizium content has to be 1,75 Si to 1 part Kalium to get very good results. you can but concrete sealing waterglass based on Kalium that is cheap and works to. More recipes can be found in Davidovits geopolymer book.

Thanks for the sub!

This is just using your regular ammonium hydroxide solution you can get at a store. I once somehow got a stronger concentration of it from a hardware store and even through my respirator I couldn't stand the smell! Let me know how that goes. I also like the fact that unlike acid piranha this stuff is relatively benign to the environment.

Thanks. I do have that and will give it a try.

Hi, what would you like to know about it?

Well, getting actual tiles from the space shuttle might be a bit tough. But yes, the material they used is very impressive! I saw a demo of it once where the inside of the material was glowing red hot but the surface was col enough to hold without gloves.

Thank you for the comments. You should be able to get the Lye at a hardware store since it's used as a common drain cleaner. You are correct that any iron that has fully rusted will undergo a significant volume expansion and will mechanically break off. That stuff is unrecoverable. But there is still a layer of rust that has not yet completed the rusting process and that can be converted. Maybe some day I'll sneak in a piece and look at it under the electron microscope to get a more quantitative idea of what actually gets converted. Yep, 3.3V at 26 amps ought to get you something! I actually just became the proud owner of two variable output power supplies that can source up to 7V at 175 Amps!!! I don't think I will try that in this application unless I need to derust a car.

Ha ha! Well in my line of work stoichiometry comes up somewhat frequently. Theoretically it could stand up to 1,600 DegC. But I suspect there could be limitations before it reaches that. I can get it heated to forge welding temperatures without issue, so that may give a practical guide on what it can do.

Popcorn would probably get much denser in the process of crushing it up. But you are right that one could use something that will simply burn up; though I would worry if that would cause gasses to expand and crack the material. One thing that I could try is flour. It would burn out and leave the micron scale gas bubbles that would help with the insulation. I might give that a try.

Glad it was helpful!

I have been able to get a forge to welding temperatures with this. Theoretically it might withstand up to ~1,600 DegC but I would say that I have not formally confirmed a max temperature.

@@Drjtherrien thx I think I’ll try this mix for my next foundry I make when my old one goes

And could i just use bone meal fertilizer as the phosphate?

What about d dextromise Earth or DE?

So bone meal is a different chemical: hydroxyapatite. If you were to use that you would need to use phosphoric acid to convert it to the calcium phosphate. I have no idea if that would work well or not.

I have been able to get a forge to welding temperatures with this. Theoretically it might withstand up to ~1,600 DegC but I would say that I have not formally confirmed a max temperature.

Awesome! I look forward to hearing how they stand up. I think the fast reaction aspect become a bigger issue when you want to cast larger forms because you have to move a lot of material quickly. But as you mentioned, maybe there is a second stage to the curing that could give some extra time. I'll play around with that myself too. What I ended up adopting for the issue you mentioned of the dry bottom was to use something such as a cloth that can wick the water and deliver it to all the surfaces of the material.

Borax may slow down the reaction. It works for me pretty well with MgKPO4 cement, kind of similar, should work.

Tim, here in Australia we can buy Richgro Super Phosphate fertiliser from Bunnings. It is Ca(H2PO4)2 the same as the hi yield triple super phosphate product, but because it has no other phosphates in it, it is up to 100% Ca(H2PO4)2 instead of the 65% wt. in the hi yield product.

Yeah I was wrong, the product at bunnings says <100% Ca(H2PO4)2 on the SDS, but when you look at it by the NPKS value of 0-9.1-0-10, it works out to be: 34.38% Ca(H2PO4)2 + 42.46% CaSO4. I tried processing and purifying it, but it was so full of garden specific garbage that it wasn’t worth it. Worked pretty well in the garden though. The Hi Yield one may say Ca(H2PO4)2, but there’s other phosphates in it, based on the NPK of 45 alone. For example, Ca(H2PO4)2 is only 26.47% phosphorus. I made this recipe work though with a modification using a superplasticiser and some ground silica, but to be honest, the MgO + KH2PO4 bonded ceramicrete recipe was orders of magnitude better than any calcium phosphate cement. Try the ceramicrete recipe and add some perlite to it, you won’t be disappointed.

Ok so the USA uses a unique system to measure phosphorus. It measures phosphorus in NPK from % of equivalent mass of P2O5 (phosphorus pentoxide). Who knows why, they just do. So NPK of 0-45-0 means that the product has 45% of the amount of elemental phosphorus as an equivalent amount of phosphorus pentoxide. Confused? Yeah… So the product has 19.64% of elemental phosphorus, so under Australian NPK labelling it’s 0-19.64-0. It’s a bloody lot of phosphorus, more than twice the amount we get in our local products. Man that had me confused.

I use the perlite to provide thermal insulation. That and it should handle higher temperatures than potash. That being said, if you are aiming to use water glass the potash would be compatible with that. You still want to have something to increase the thermal insulation.

I was thinking about creating small air pockets by adding a small amount of sawdust evenly spread through the mixture that would burn out leaving airports. I saw another guy do this when making clay fire bricks.

@@LittleAussieRockets Why not ground up styrofoam?

@@Drjtherrien True! thanks

Cool! Well keep at it and hopefully you'll get there. Are you trying to dope the ZnO? I played around with that but wasn't satisfied with my ability to control impurities at the level needed.

@@Drjtherrien I just want to create a point contact diode close to 1N34 in its features , and before everything it should be stable against lite shocks caused by movement .

Yes that will be challenging. I think one issue is that ZnO is a relatively soft material and will be easily scratched. Combining that with the need for the film to be thin is going to make that challenging.