We've discovered a metal BETTER than firebrick! (Just one caveat)

Gordon Haverland wrote:

I have nothing really to add to this, good stuff. All I have to say is that the incandescence often times correlates with accelerated oxidation, particularly in steel, stainless steel, nickel, copper, and other common metals. Much like how CO output correlates with grams per hour of fine particles even though they are different. Oxide coatings are usually expensive.

Materials science is my field.  

If Fe/Ni/Cu surfaces give rise to light emission at elevated temperature in an oxygen environment, you might think of it as combustion.  Maybe.  Different metals will have different emission curves as a function of temperature, but nominally yellow heat for steel should be the same for cast iron, nickel, stainless, copper, tungsten, tantalum, rhenium, iridium, ....

Some kind of surface chemistry on the fine particles?  There is a chemical equilibrium between CO, CO2 and C.

The coatings are cheaper than making the bulk material out of a resistant material.

But that is sort of why I brought up the aluminides.  Unlike aluminum metal, the part stays solid.  Like aluminum, the surface is protected in large part by alumina.  It can help to add other things to this alumina layer.  Ductility has been a historical problem, but if you are comparing them to refractories they are probably okay.  I suspect your cheapest one is going to be iron aluminide, and it probably has the worse properties of the 3.  But, it has been a while since I read much about it.

Cold spraying might form a useful coating, but I think the various hot spraying methods might be better for you.

I do think your limiting factors are thermal fatigue of the coating (leading to spalling) and sulfur (selenium, tellurium).

I didn't know much about your stoves, and just read a bit at Wikipedia (before my first reply).

Neat. I'm glad there are people here that know more about this stuff than I do. We basically have a steel J shaped combustion system and thus far stainless 330 is looking very appealing. I want a metal that will be strong enough to contain a thin 1/4" layer of aerogel or other super insulation and protect it from abrasion and other ways the insulation might be damaged. So my tube will be as this: 1/4" steel tubing on the outside, insulation, and a protecting layer of metal to line the stoves combustion chamber. I also like Stainless because it has a high emissivity and will reflect a lot of the infrared heat back onto the delfegration wave and the fuel to assist in a cleaner burn. BUT if there are coatings for the stainless steel or other steel parts then thats definitely something I want to know about. I have greatly considered using foamed carbon insulation and then shielding it from oxygen but thats for a model WAY down the road.

Hello Sky,

I'm not sure if you saw my post above about GeoPolymers... If you have, I wanted to also add another way it could be helpful to solve your problem and on the real cheap. If you play with the Alumina and silica ratios when making a GeoPolymer mix (See: https://www.geopolymer.org/science/chemical-structure-and-applications/ for ratios and specific features), you can create an epoxy like coating that has been used to coat metals (sprayed) to protect them from rust or heat. It ends up being very similar to a powder coating, but the coating is a ceramic coating that is UV stable and with the proper ratio, will resist heat without problem. The nice part is that all that process is done at room temperature and next morning (A few hours later) you have a ceramic coating on your surface. They've tested it and there was a pdf out there with recipes that were tested from what I remember. The nice part about doing it that way is that you don't have a heavy item like when doing the full cast of a 1:1 mix ratio and end up something similar to a granite casted burn tunnel but much harder and that will cost a lot to ship. You have the shape made out of cheap steel and you coat it on the inside. I was planning on coating all machines I'm planning on building (wood gasifier, bio char maker, rock grinder etc...).  If you are interested, I could check quickly in my pdf archives if I already have the study paper.

Cheers

Jan

Austenitic stainless (300 series) is nominally a lousy conductor of heat.  Can be good or bad.

The one aerogel application I follow, is in stick frame construction.  You put (staple?) 1/4 inch thick aerogel that is 1.5 inch wide to the wood 2x, put up the drywall, and then screw nail the drywall to the stud.  So, aerogel can take a bit of a beating.  Maybe your aerogel doesn't?

Mineral wool is in general probably not as high tech as aerogel, but there are fibrous refractories which take abuse.  Maybe a pottery site?

It is possible to get basalt fibre (many mineral wools could be described as basalt fibre), including as an engineering fabric (similar to fibreglass).

With respect to our geopolymer friend, by an epoxy like substance are you referring to phenolic resin?  Ablative heat shields are often (typically?) phenolic, and as they heat up, they char.  The high porosity cuts down on heat transfer to the substrate.  There are places where phenolic resin is the preferred adhesive for wood.  I think Aircraft Spruce has some.  WHether you can add stuff to the phenolic to tailor properties, I have never had the chance to try.

About half way between epoxy and phenolic, is that the active group in cashew shell nut liquor is a phenol compound, and some people have used CNSL where they insert epoxy groups.  So, the compound could be referred to both ways.

If temperatures are so high that steel is melting (or you are worried about this), you might need to look out for sand (silicon dioxide) turning into silicon monoxide, which is a gas.  Sort of like sublimation of water.  This is a short-circuiting reaction which is observed in ferrous pyrometallurgy.

But if steel (whatever you are working with) works, something to think about.  I came up with this vis a vis wood fired pizza ovens.  But, heat transfer is across an area.  If you want good heat transfer, you optically polish both surfaces flat.  If you want lousy heat transfer, you want rough surfaces.  If you can find a single layer fabric (like a fibreglass deck cloth) that is 0.1mm thick and some grit that is bigger (say 0.25mm), a layer of steel, a dusting of grit, a layer of cloth, repeated could work.  The cloth is there to keep the grit from moving around.  Nominally, the only path for heat transfer is through the grit particles.  And they likely only have "points" of contact (irregular shapes), so the area for heat transfer is vanishingly small.  If you make the heat transfer coefficient small enough, you may need to worry about melting.  The metal used could actually even be good at conducting heat, which would cause each metal sheet to have about the same temperature everywhere, lowering local temperature gradients.  Can a person take several layers of this, and form it to a shape?  Maybe.  Depending on the shape, you might be able to stack already formed sheets.  But then you need to sort of attach the grit to the cloth, as there is no level surface to spread it on.

Gordon Haverland wrote:Austenitic stainless (300 series) is nominally a lousy conductor of heat.  Can be good or bad.

Lousy heat conductors are exactly what we want. Some GunSafes use stainless steel to dissipate heat and as a torch resistant layer of metal. It can act a little like an insulation.

The grit between sheets avoids one problem and steps into another.  Depending on the metal, you could have substantial radiative heat transport between the sheets.  And your temperatures are a bit higher than a wood fired pizza oven.  Convert to absolute temperature and raise to the 5th power, and you could move a lot of heat that way.

The things you think about when reading a bunch of nerds (like myself) try to measure the specific gravity of wort.  

Hello Gordon,

GeoPolymers are not a plastic at all. It was discovered and developed over the last 30 years by the GeoPolymer Institute in France. In the 70's, they had a bad wave of city fires and were looking for a material that wouldn't burn and release toxic fumes. The name GeoPolymers was coined because the scientist that discovered the process was a plastic polymer researcher and realized that you could apply polymerization to rock minerals in the same way as applied with plastic polymers but by using alkalies to soften up the rock bonds. Over the last 30 years, they discovered many applications and different ways to use it. This technology can be applied to so many fields that it would be hard to cover it all in a single post. GeoPolymers is a mean of making rocks at room temperature. Depending on ratios of minerals (Aluminas and Silicas), you get very different properties. Some mixes can be quite liquid before hardening or have a harder consistency than fresh uncured concrete on the other end of the spectrum. With the more
liquid mixes, it looks like and acts like an epoxy, except that it hardens as a rock once cured (curing is crazy fast). They used it like epoxy, with fiberglass to make statues and the like. They also experimented in making sealant. Imagine using a sealant that doesn't ever degrade to UV like the silicon sealant we use and is as hard as a rock. They also used it as a coating on metals which would be similar in some ways as a ceramic coating on a ceramic cooking pot once it's cured but all of that is done at room temperature. Some recipes may require heat, but the heat needed is nothing crazy. The more the silica to alumina ratio, the more heat resistance you have, which is what the Op wants. The range the Ops would want to look into are 20:1 up to 35:1 silicates to aluminates. They even looked into using casted GeoPolymers panels as a liner on foundries. At those ratios, it's almost like having pure sand that can be casted/sprayed, so the heat resistance would be VERY high. If you're curious to know more, this short pdf I linked goes over the last 30 years of research and the different fields they applied the technology:

https://www.geopolymer.org/fichiers_pdf/30YearsGEOP.pdf

The possibilities are pretty much limitless. I've come across one article that talked about GeoPolymers on permies to use in rocket mass heaters while looking to find recipes and others, but the info was minimal and I can't recall if it was more AAM (Alkalies Activated Materials) or a true GeoPolymer. Some people confuses both of them as the same and that has led to a bad rap for the product. The confusion was spread by the concrete industry and I would believe that it's possibly because the product can be used to replace concrete. Imagine if you can cast a granite block (amorphous and not crystalline like granite is normally found) for your house foundation, you'll never have cracks and will last 1000's of years easily. Also, because the molecular formation is a rock polymer, it's completely waterproof. So can be used for water tanks, under water, completely inert to alkalis, acids and salt water. At some point in his career, the scientist was asked to study the pyramids in Egypt and due to his knowledge of Geopolymers, he was able to recreate the blocks they made when building the pyramids and proved very easily that the pyramid are casted blocks at room temperature. He gives the recipe that they used if someone searches for it. The bottom first row of the pyramid was casted using some kind of burlap shapes and exhibits oozing at the bottom of the forms (which proves they were casted). The subsequent layers are casted in wooden forms, which explain their precision. Anyway, the material can be used for so many things. It's perfect for all of us that wants to have more freedom and less dependencies on stuff that breaks and needs constant repair but will require a bit of fiddling around.

I hope this helps clarify a bit what GeoPolymers are.

Cheers

Jan

What about magnesia?

Jan Corriveau wrote:
Hello Gordon,

GeoPolymers are not a plastic at all. It was discovered and developed over the last 30 years by the GeoPolymer Institute in France. In the 70's, they had a bad wave of city fires and were looking for a material that wouldn't burn and release toxic fumes. The name GeoPolymers was coined because the scientist that discovered the process was a plastic polymer researcher and realized that you could apply polymerization to rock minerals in the same way as applied with plastic polymers but by using alkalies to soften up the rock bonds. Over the last 30 years, they discovered many applications and different ways to use it. This technology can be applied to so many fields that it would be hard to cover it all in a single post. GeoPolymers is a mean of making rocks at room temperature. Depending on ratios of minerals (Aluminas and Silicas), you get very different properties. Some mixes can be quite liquid before hardening or have a harder consistency than fresh uncured concrete on the other end of the spectrum. With the more
liquid mixes, it looks like and acts like an epoxy, except that it hardens as a rock once cured (curing is crazy fast). They used it like epoxy, with fiberglass to make statues and the like. They also experimented in making sealant. Imagine using a sealant that doesn't ever degrade to UV like the silicon sealant we use and is as hard as a rock. They also used it as a coating on metals which would be similar in some ways as a ceramic coating on a ceramic cooking pot once it's cured but all of that is done at room temperature. Some recipes may require heat, but the heat needed is nothing crazy. The more the silica to alumina ratio, the more heat resistance you have, which is what the Op wants. The range the Ops would want to look into are 20:1 up to 35:1 silicates to aluminates. They even looked into using casted GeoPolymers panels as a liner on foundries. At those ratios, it's almost like having pure sand that can be casted/sprayed, so the heat resistance would be VERY high. If you're curious to know more, this short pdf I linked goes over the last 30 years of research and the different fields they applied the technology:

https://www.geopolymer.org/fichiers_pdf/30YearsGEOP.pdf

The possibilities are pretty much limitless. I've come across one article that talked about GeoPolymers on permies to use in rocket mass heaters while looking to find recipes and others, but the info was minimal and I can't recall if it was more AAM (Alkalies Activated Materials) or a true GeoPolymer. Some people confuses both of them as the same and that has led to a bad rap for the product. The confusion was spread by the concrete industry and I would believe that it's possibly because the product can be used to replace concrete. Imagine if you can cast a granite block (amorphous and not crystalline like granite is normally found) for your house foundation, you'll never have cracks and will last 1000's of years easily. Also, because the molecular formation is a rock polymer, it's completely waterproof. So can be used for water tanks, under water, completely inert to alkalis, acids and salt water. At some point in his career, the scientist was asked to study the pyramids in Egypt and due to his knowledge of Geopolymers, he was able to recreate the blocks they made when building the pyramids and proved very easily that the pyramid are casted blocks at room temperature. He gives the recipe that they used if someone searches for it. The bottom first row of the pyramid was casted using some kind of burlap shapes and exhibits oozing at the bottom of the forms (which proves they were casted). The subsequent layers are casted in wooden forms, which explain their precision. Anyway, the material can be used for so many things. It's perfect for all of us that wants to have more freedom and less dependencies on stuff that breaks and needs constant repair but will require a bit of fiddling around.

I hope this helps clarify a bit what GeoPolymers are.

Cheers

Jan

This is amazing stuff. I've been looking into it since it was mentioned here and there's so much information I dont even know what to say.

Sky, there's a fait bit of information
At donkey's and most certainly at Karl's website.        

I believe I may have not been fully clear about GeoPolymers, many of the recipes do require a higher temperature while curing . The temperature are never above 100C and I think I recall seeing 60C as the average temperature needed in many of those recipes. Some are done at room temperature (like concrete substitutes). I just thought I'd add that for clarity. Building the equivalent of a pottery kiln that would go to those lower temperatures would be fairly cheap and easy. It could even be used in conjunction to a wood gasifier for heat generation.

I also attached 3 PDF referring to studies made on using it as a coating on metals in case it helps someone. I haven't read them all, so not sure what they say, but may save the time for someone to have to find them. I can see GeoPolymers as a really nice way to make a burn chamber that can last an eternity and only need regular cleaning of ashes... The downside is that it's not a simple product that you can buy off the shelves and you're done. It will require some small or larger level of dedication to make it work, but the reward, in my opinion is in what it gives people like us that are into prepping and would like to have control of our technologies and do everything on the cheap. What I want to do with that new science on my ranch are water tanks, roads, pond sealant, CNC machine frames (dampens vibration), coating on metal to preserve and limit rust, insulation (sprayed or pre-cast like concrete), Construction replacement (foundation, walls, and name it), and the last is material science (they made high amp fuses out of that stuff. There's got to be more uses). That's just what comes to mind very quickly.

Cheers

Jan

309 SS handles a lot of heat, they use it in furnace heat exchangers and such, I am using it in my rocket stove grate/basket with pellets, it glows red when stove is running hot!!!, I use the 1/8th inch rods to build the basket, I will let you know next spring how they last, because I will be running it all winter long...if the good lord willing....
another thing is what they make stove heating elements out of would be a good look into.....just my 2 cents....

Sky if you are trying to keep your stove rugged, shippable and all metal Here is some info for ya.

I have always stated its not metal but the "type" of metal used that keeps a stove from being an official rocket stove. I have mentioned Tungsten before. If a person uses heavily insulated tungsten tube burn chamber and Heat riser, you could have your self an all metal rocket stove reaching desired temp and high temp burning efficiency.

Tungsten, also known as wolfram, is a chemical element with symbol W and atomic number 74. The word tungsten comes from the Swedish language tung sten, which directly translates to heavy stone.  source: Wikipedia
Symbol: W
Atomic number: 74
Melting point: 6,191°F (3,422°C)


Here are some places to get Tungsten and Tungsten alloy Tubes:

https://www.alibaba.com/product-detail/China-products-tungsten-square-tubes-tungsten_60450714251.html

https://www.alibaba.com/product-detail/Manufacture-tungsten-pipe-tungsten-carbide-tube_1726398953.html

http://www.thomasnet.com/products/tungsten-tubes-88615026-1.html

https://www.alibaba.com/product-detail/high-quality-tungsten-carbide-ceramic-tube_1394288839.html

https://www.americanelements.com/tungsten-tube-7440-33-7

http://www.thomasnet.com/profile/00985767/ultramet.html?what=Tungsten+Tubes&cov=NA&heading=88615026&searchpos=1&cid=985767

Burra Maluca wrote:

Chris Southall wrote:Why not use cast iron or even boiler plate - good enough for wood stoves and cooking ranges for centuries past.  I used recycled heavy steel tube for my rocket stove and I am confident it will last many years

A properly functioning rocket stove will reach temperatures that will burn out cast iron and steel.  This has been demonstrated over and over ad nauseam

Permies.com does not recommend the use of metal in the burn tunnel or heat riser of a rocket stove or mass heater.  Please check out this thread - using metal in the burn tunnel and heat riser

I agree with Burra... Partially. It is my opinion that the topic she mentions "Permies.com does not recommend the use of metal in the burn tunnel or heat riser" should be changed to "Permies.com does not recommend the use of LOW TEMP metal in the burn tunnel or heat riser for a very serious and factual reason; although there are many metals that can withstand 3000+ F temps but the availability may or may not be obtainable to the average person.

Though metals like W(3400), Re(3186), Os(3025),Ta(2980), Mo(2620),Ru(2482) ,Nb(2470) have m.pts(C) equal to or higher than 2500C but it it found that many alloys of these metals have mpts less than 2500C. So an attempt is made to give the names and % composition of the alloys of these metals having mpts in the range of 2500C .It is not the final list and if one tries to go deep into literature survey, one may find more examples. The last two alloys have mpts higher than either of the contituent metals.

Ta-C[C-2] (2843C).
W-C [W1.3] (2715C).
R05252 97.5% Ta 2.5% W (2996-3000C).
R05252 90.0% Ta 10.0% W [2996-3000C].
R05240 Ta=60%; Nb=40 % [Appxo2900C].
W-Mo alloy W=25-30%.Mo=70-75(depending upon %, mpts vary but are always more than 2620C).
Many Waspsloys with varying weight % of Ni, Co,Fe,Cr,Mo, Al, Ti,C,Mn, Si,B,Cu,Zr have melting range 2475-2500C.
TZM (Mo ~99%, Ti ~0.5%, Zr ~0.08% and traces of carbon with mpt2623C).

MICROALLOY M310" OSMIUM ALLOY (Os 35%, Tungsten carbide 59%, Co 6%).
Mo:Ru (5:3).
W:Ru (5:3).

source:https://www.researchgate.net/post/Which_alloys_have_melting_temperature_higher_than_2500_degree_celcius

I expect any of these super-high-temp elements or alloys would be so expensive that the quantities needed would be prohibitive for the ordinary builder.

There is also the factor mentioned numerous times that it is not just melting temperature, but corrosion resistance at high temperatures, that limits many materials.

Glenn Herbert wrote:I expect any of these super-high-temp elements or alloys would be so expensive that the quantities needed would be prohibitive for the ordinary builder.

There is also the factor mentioned numerous times that it is not just melting temperature, but corrosion resistance at high temperatures, that limits many materials.

Glenn, I respect your opinion but Its seems as though you may not have clicked any of the links before you commented. The manufacturer of these materials rate these tubes for high heat furnaces and Nuclear applications. You cant get any harsher than Nuclear and rocket fuel environments.

as for price many of the manufacturers i listed sell in bulk and depending on what Sky orders may get him a break and is up to him what he wants to pay or what he finds affordable. As I said i found many places where to look and shop around for the best price for what Sky deems he needs.

From the site: Application:
Tungsten tube is widely used in the thermocouple protection tube, sapphire crystal furnace and high temperature furnace, etc. Tungsten is usually sintered processed and with 8mm wall thickness. Tungsten tube contributes stability to the hot zone. While high in thermal inertia, tungsten tube may prolong the growth cycle of the sapphire.

Nuclear aerospace and military industry (carrying boat,radiation shield,tungsten crucible for renewable nuclear fuel,rocket nozzle,throat,penetrator).

10,Vacuum or gas protected high temperature furnace material (sintering furnace,monocrystalline furnace,annealing furnace)

I didn't look at any of the links, as I did not feel the need to take the time now. They are obviously used for various industrial or military purposes, although I think those are all more tolerant of expensive parts than an individual RMH builder is, or probably a commercial builder who has to sell his product to the permies. I expect Sky has already investigated most of the high-temp metals available and rejected most of them for whatever factors, including cost, workability, and operating characteristics.

Steel has a melting point of around 2600-2800F depending on the alloy, but softens at 1000 degrees lower; it would be interesting to know the temperature-to-strength characteristics of these other metals. Nichrome wire used in heating elements expands and softens, yet does not corrode, at kiln temperatures. Some metals are obviously strong at much higher temperatures.

F Styles wrote:

Glenn Herbert wrote:I expect any of these super-high-temp elements or alloys would be so expensive that the quantities needed would be prohibitive for the ordinary builder.

There is also the factor mentioned numerous times that it is not just melting temperature, but corrosion resistance at high temperatures, that limits many materials.

Glenn, I respect your opinion but Its seems as though you may not have clicked any of the links before you commented. The manufacturer of these materials rate these tubes for high heat furnaces and Nuclear applications. You cant get any harsher than Nuclear and rocket fuel environments.

as for price many of the manufacturers i listed sell in bulk and depending on what Sky orders may get him a break and is up to him what he wants to pay or what he finds affordable. As I said i found many places where to look and shop around for the best price for what Sky deems he needs.

From the site: Application:
Tungsten tube is widely used in the thermocouple protection tube, sapphire crystal furnace and high temperature furnace, etc. Tungsten is usually sintered processed and with 8mm wall thickness. Tungsten tube contributes stability to the hot zone. While high in thermal inertia, tungsten tube may prolong the growth cycle of the sapphire.

Nuclear aerospace and military industry (carrying boat,radiation shield,tungsten crucible for renewable nuclear fuel,rocket nozzle,throat,penetrator).

10,Vacuum or gas protected high temperature furnace material (sintering furnace,monocrystalline furnace,annealing furnace)

The links you provided, I've seen them and many others before.
1: The tungsten ceramic is 50 to 300 dollars per kilogram. Tungsten is literally just as dense as gold, and so the amount would add up to be hundreds of dollars, perhaps even close to a thousand dollars. And yes, thats with bulk pricing.
2: Stainless 330 as another poster pointed out has a heat resistance of 2000 F.
3: The problem with tungsten is that it cant be cut, shaped, or formed easily.

Its not just the heat that Glenn and many others are saying will destroy steel. the moisture of any kind with o2 can get into the pours of the 330 steel and expand it 1500 times and it can eventually weaken it.

F Styles wrote:Its not just the heat that Glenn and many others are saying will destroy steel. the moisture of any kind with o2 can get into the pours of the 330 steel and expand it 1500 times and it can eventually weaken it.

http://www.pennstainless.com/stainless-grades/high-temps-grades/330-stainless-steel/

I doubt that moisture will effect this stainless steel. Its used in high temperature boilers, steam and gas turbines, ore processing for perlite, petrochemical processing and furnaces (which means its chemically not very reactive) and even high temperature salt pots. So given the spec sheets of this high grade stainless steel, which is 37% nickel and another large percentage of chromium. I've looked at the specs of 330 SS since it was suggested and I'm very impressed. Its also cost effective, and thats important as well.

Yes many people here have reviewed 330 SS alloy and it is recommended not to exceed 1900 F. The better question may be are you going down the 330 SS alloy path so you can insulate the heat riser and if so, how can you guarantee the stove stops at the 1900 F suggested weakening point? If you decide to insulate your heat riser, it will turn your great stove craftsmanship into a dragon beast that may not have a guaranteed tame-able temperature limit. With many different types of wood burning at different temperatures no one type of design can guarantee a certain temp all the time from all woods and stages of dryness. It was also suggested Inconel for higher than 1900 F temps and you can find some links here of some suppliers and prices.  

http://pacificalloys.com/Inconel.html

http://www.reliantpipes.com/inconel-incoloy-pipetubes-tubing/index.html

http://www.steeltubes.co.in/inconel-alloy-600-625-pipes-tubes-supplier-exporter/


source: https://www.marlinwire.com/blog/what-is-the-temperature-range-for-304-stainless-steel-vs-316-vs-330

F Styles wrote:Yes many people here have reviewed 330 SS alloy and it is recommended not to exceed 1900 F. The better question may be are you going down the 330 SS alloy path so you can insulate the heat riser and if so, how can you guarantee the stove stops at the 1900 F suggested weakening point? If you decide to insulate your heat riser, it will turn your great stove craftsmanship into a dragon beast that may not have a guaranteed tame-able temperature limit. With many different types of wood burning at different temperatures no one type of design can guarantee a certain temp all the time from all woods and stages of dryness. It was also suggested Inconel for higher than 1900 F temps and you can find some links here of some suppliers and prices.  

http://pacificalloys.com/Inconel.html

http://www.reliantpipes.com/inconel-incoloy-pipetubes-tubing/index.html

http://www.steeltubes.co.in/inconel-alloy-600-625-pipes-tubes-supplier-exporter/


source: https://www.marlinwire.com/blog/what-is-the-temperature-range-for-304-stainless-steel-vs-316-vs-330

We've looked into inconel. Again, its too cost prohibitive.

http://www.pennstainless.com/stainless-grades/high-temps-grades/330-stainless-steel/

^Here it says that SS 330 is good up to 2200 F.

And we thoroughly test our heaters with fuel types of all kinds and types before we introduce it to market. Right now I'm not worried about t getting past 2000 F. because our firetube size is very small. The RMH designs that have heat issues are the 6" and especially the 8" inch core systems. The larger the core the higher the temperatures involved. Our stove has a 4.5" core so its very very small even compared to the 6" RMH. We all know the 6" RMH core burns much cooler than an 8" RMH core. the 4.5" burn tube also doesn't get nearly as hot as a 6" system. So for now, I'm not worries about it. When we make an Liberator Rocket Heater XL version then we will start to think about ceramics, refractory's, and so on. Right now our 4.5" tubes are much too small to fit any amount of refractory's in there. We are just looking at a small 1/4" layer of super-insulation with a stainless liner to increase longevity and get a little more performance.

Have you thought about testing the idea of stacking in tongue and grooved ceramic rings (to avoid temp fluctuation cracks) that have ribs on the outside to put air space on the inside of a metal tube for burn chamber and heat riser and ship with removable Styrofoam inserts to avoid shipping breaks, that way you can insulate around the metal and keep it from breaking down the heat and also use cheaper metals?

you could warranty the ceramic inserts for a certain time period and then create another market for replaceable ceramic inserts and sell them separately to people that are too rough on their system after the warranty runs out as you would design them to slide in and out.

F Styles wrote:Have you thought about testing the idea of stacking in ceramic rings (to avoid temp fluctuation cracks) that have ribs on the outside to put air space on the inside of a metal tube for burn chamber and heat riser and ship with removable Styrofoam inserts to avoid shipping breaks, that way you can insulate around the metal and keep it from breaking down the heat and also use cheaper metals?

Thats actually a good idea, about the ceramic rings. However we feel that the burn tube is just as if not more important to insulate than the heat riser. So we will need custom shaping as well, hence the SS liner for the burn tube. Again all these idea's are probably going to be implemented in the next version of the heater.

am i correct in saying that you want a fix for the builds you have now and a 330 SS thin sleeve insert would help mitigate a potential problem until your next build?

i think you are correct in saying the burn tube is important also and i was actually thinking of using the ceramic rings in the burn tube as well and think it would creat more of a market for you as replacement parts or upgrades.

you could sell outer insulation sleeves and inner ceramic ring upgrades for currant units if its possible?

F Styles wrote:am i correct in saying that you want a fix for the builds you have now and a 330 SS thin sleeve insert would help mitigate a potential problem until your next build?

i think you are correct in saying the burn tube is important also and i was actually thinking of using the ceramic rings in the burn tube as well and think it would creat more of a market for you as replacement parts or upgrades.

you could sell outer insulation sleeves and inner ceramic ring upgrades for currant units if its possible?

There is no way to "fix" the heat riser because the top is not removable.

The burn tube must stay rectangular for cleaning and if the customer is using pellets.

Therefore we just want a material for the burn tube for the future, it will be an improved model of the current heater. With better machinery and higher sales volumes we expect this heater to be a great gravity fed pellet/wood stove but nothing industry changing. Right now we just want an improved version of what we have. We are developing something super secret I wont tell anyone here much about that will change the entire industry.

you can tell us here. We promise we wont tell anyone. just post it here on this thread and it will be safe.

F Styles wrote:you can tell us here. We promise we wont tell anyone. just post it here on this thread and it will be safe.

Dont worry, it will become public information in time. Hopefully within a year or two tops.

Sky, I think a class of materials with the properties you're looking for might be "cermet".
http://en.wikipedia.org/wiki/Cermet