904 Ceramic Adhesive

[HyperSonic]

I wanted to try out this 904 Zirconia from Cotronics as a shield from friction and heat on my leading edges of my fins while flying at extreme velocity. The only rocket I have to try it on right now is my L3 rocket, which its top speed is only Mach 2. IMHO, that is where the party starts. I'm thinking on trying this stuff on my N5800 MD rocket. (my next build) That one will be in the Mach 3 range at very low altitude. I want to get a little experience using this stuff, as the numbers on strength are no way close to epoxy. What I ended up doing was thinning out the 904 (thinner came from cotronics made for the 904) to almost water consistency, doesn't take much thinner. Then I coated both sides of a piece of 7/8 inch wide fiberglass tape, got the leading edges wet with 904, and laid the tape over the leading edges of all three fins. Let cure. This stuff doesn't sand very easy, if at all.

I believe one weak point of this stuff is its staying put power. If any air gets underneath it at high Mach, it will peel off like a banana. So I put a couple coats of 4461SS Cotronics epoxy over the 904 to help keep it in place. Sanded everything super smooth, and she's ready for some Mach travel. These fins were coated many times with 4461SS before the 904 was applied.

If anybody has used this stuff before, I would like to hear your opinion on it. And if not, I'd still like to hear any thoughts on what I've done up until now. Thoughts anyone????????

 

[A5tr0 An0n]

I have used this before. I went through a trial phase with a bunch of cotronics stuff. I would argue that it is unsandable. I took an electric sander, dremel, etc. to it and it would just glow orange and then cool down as if nothing happened lol. I ended up having to remove it with a hammer drill and hours of elbow grease. Never ended up flying it, but I think it would of held. However, after my first experience with it (applied it to a fincan & NC) i determined it less than ideal and haven't used it sense.


You don't need to go beyond using adequate bonding techniques and a good quality resin to survive a M2 flight. I wouldn't worry about anything till you're approaching M3+.


In the picture it appears that you applied your fillets over the 904? That didn't worry you about a weak bond on the front end of the fins? Don't know that I would go about the same bonding methods on the MD N5800.

 

[Andrew_ASC]

The Bio med industry used Zirconium for hip implants. Smith and Nephew ultimately used belt sanders (many hours) and eventually came up with a non patented ceramic hershy kiss drop (blue fine grit surface) that fit in a VAT and spun real fast to polish parts. Zirconium metals had a unmachinable reputation. It was heck on tool bits the industrial cobalt heat treated variant that cut all grades of titanium and tool steel as if those materials were butter. Machine coolant companies must love that bio med company as a favored buyer. Zirconium is best for low friction metal to metal joint, for hips. Absolute bear and half for the guys and gals working with material on the factory floor. This is the resin ceramic nightmare version. A poor man's X-15 ablative. Might as well add ultrasonic machining processes at micro units per pass. Normally aluminum gets 30 thousandths inch per pass, easily machined. Steel 5 thousandths per pass. Ceramics are like micro units. I'm guessing Zirconia is a Zirconium dust inside a ceramic resin and what you sir have found is an unmachineable, unsandable, yet thermal wonder in a tub. It'll work for a leading edge ablative. Seems like total overkill and you've got Skunkworks style post processing problems now. The glowing was probably related the dremel bit eating itself and heat transfer to epoxy.

I would argue that it is unsandable. I took an electric sander, dremel, etc. to it and it would just glow orange and then cool down as if nothing happened lol.

​

The bio med factory resorted to using custom ceramic tools to sand ceramics. The Zirconium metal ate industrial cobalt tool bits too rated for thousands of hours of longevity in several hours, so they changed tool bits on rotor links connected to CNC mills often. CNC couldn't get tolerances tight enough then belt sanders were used years ago. I wouldn't be surprised it glows and it eats diamond dust coated tool bits all the lesser materials around the diamond dust. I wouldn't trust it as a structural fillet, but an ablative seems doable if you ever finish it right. Never used the material. Absurdly overkill outside of an X-43A ablative application.

Look at this datasheet on Mi-15 Lockheed Martin Previous uses were "Missiles" thermal protection.
https://www.lockheedmartin.com/cont...protection/factsheets/MI-15 product sheet.pdf
And it only went to 950 F.

Anyways you really beat it on pricing.
https://www.silmid.com/silicones/si...tin-mi-15-sealant-3-part-a-b-c-type-1usg-kit/
So they weren't even messing with non sandable ablatives. ROFL.

Some kind of silicone elastomer was X-15 Mach 6.33 good! The MA-25S X-15/Spaceshuttle external tank.
https://www.lockheedmartin.com/cont...rotection/factsheets/MA-25S product sheet.pdf

 

[HyperSonic]

I have used this before. I went through a trial phase with a bunch of cotronics stuff. I would argue that it is unsandable. I took an electric sander, dremel, etc. to it and it would just glow orange and then cool down as if nothing happened lol. I ended up having to remove it with a hammer drill and hours of elbow grease. Never ended up flying it, but I think it would of held. However, after my first experience with it (applied it to a fincan & NC) i determined it less than ideal and haven't used it sense.

I found that with my little experience working with the 904, you cannot cake it on and expect to sand it down where you want it. Your right, it doesn't sand at all. It must be applied in very thin coats (thinned out to water consistency) as smooth as possible while it is wet. Then after it cures, I use a high quality fine sandpaper to smooth it out the best I can. It doesn't take off material, just makes it smooth to the touch. It might take a few sheets of sandpaper and some effort, but we are only sanding the leading edges here. After smoothing it out, I then apply more thin coats of epoxy to help keep it in place. I did a sloppy job getting it all over the place on this rocket, but my next one will be a better job. Live and learn.

You don't need to go beyond using adequate bonding techniques and a good quality resin to survive a M2 flight. I wouldn't worry about anything till you're approaching M3+.

I realize that this rocket does not need the 904. The ONLY reason it is on here was to gain some experience working with it.

In the picture it appears that you applied your fillets over the 904? That didn't worry you about a weak bond on the front end of the fins? Don't know that I would go about the same bonding methods on the MD N5800.

Good point taken about the 904 being underneath the fillet. This rocket has more epoxy under the airframe that you don't see (TTW, injection, ect..) so I wasn't worried about the fin pulling out of the slot at the top of fin. But if they were surface mounted like my MD N5800 will be, it would definitely make a big difference to keep the 904 on top of the fillet. Thank you for all your input.

Not many replies to this thread??? I get that most people might not have any experience with this stuff. Neither did I, but I was hoping for more opinions I guess.

 

[Steve Shannon]

I found that with my little experience working with the 904, you cannot cake it on and expect to sand it down where you want it. Your right, it doesn't sand at all. It must be applied in very thin coats (thinned out to water consistency) as smooth as possible while it is wet. Then after it cures, I use a high quality fine sandpaper to smooth it out the best I can. It doesn't take off material, just makes it smooth to the touch. It might take a few sheets of sandpaper and some effort, but we are only sanding the leading edges here. After smoothing it out, I then apply more thin coats of epoxy to help keep it in place. I did a sloppy job getting it all over the place on this rocket, but my next one will be a better job. Live and learn.




I realize that this rocket does not need the 904. The ONLY reason it is on here was to gain some experience working with it.





Good point taken about the 904 being underneath the fillet. This rocket has more epoxy under the airframe that you don't see (TTW, injection, ect..) so I wasn't worried about the fin pulling out of the slot at the top of fin. But if they were surface mounted like my MD N5800 will be, it would definitely make a big difference to keep the 904 on top of the fillet. Thank you for all your input.

Not many replies to this thread??? I get that most people might not have any experience with this stuff. Neither did I, but I was hoping for more opinions I guess.

I’m not offering opinions because I’m enjoying the thread.

Partially stabilized zirconia has been used to make hammer heads and knife blades.

 

[Charles_McG]

Andrew, zirconia is the metal oxide of zirconium. ZrO2. It’s the analog of alumina, Al2O3. I’ve made it a few times, but for solid superacid catalysts.


Sent from my iPhone using Rocketry Forum

 

[prfesser]

Just to clarify, because both terms are being used in this thread. ZirconiUM is an element, shiny metal, burns with a bright white light, high melting point, used to make tubes in which uranium oxide pellets are loaded for fuel rods in nuclear reactors. ZirconiA is zirconium OXIDE, a compound of zirconium and oxygen, off-white non-metallic ceramic, very hard and used as an abrasive. Two very very different things.

Best,
Terry

 

[G_T]

Zirconium is a machining issue as the chips can easily ignite in atmosphere. Zirconium Dioxide is rather hard. But I've had no issues cutting or grinding it with diamond tooling. Copiously lubricated, of course.

Gerald

 

[HyperSonic]

Here are a few pics of PePe sporting his new look. Who said 904 doesn't sand. Maybe because I thinned it a little. It is not easy and goes through sand paper quick, but it will remove some material. Wish PePe only had 3 fins. One down, and 3 more to go.

 

[HyperSonic]

Some more pics of PePe showing off his new look









This will be my last post here on this thread since the 904 part of the build is done. I'll continue PePe's progress in the thread CF Fin attachment. I doubt if anybody will be doing this any time soon, so I'll leave the how I did this part out. The why is simple, to protect my leading edges from delamination when traveling at extreme speeds. What is all black with a white stripe?.............PePe La Pew. Pepé Le Pew is a character from the Warner Bros. Looney Tunes and Merrie Melodies series of cartoons, first introduced in 1945. Depicted as a French striped skunk, Pepé is constantly in search of love and appreciation. However, his offensive skunk odor and his aggressive pursuit of romance typically cause other characters to run from him. I didn't know at the time that there was already some one using the name on this forum. (sorry about that) So I shortened the name to just PePe.

I think he looks good with the white edges. Maybe I'll continue them up the airframe to meet up with the white nosecone. ( not with the 904, just white paint) I need some skunkworks stuff going on! Maybe by using the 904, that qualify's as skunkworks material! I will not be using any odor on him.

 

[Greg Furtman]

Hyper, this company has a wide ranging variety of ceramic adhesives. Take a look. MAybe something there for your future builds.

https://www.aremco.com/

 

[HyperSonic]

Thanks Greg, I will check them out. The 904 is hard to work with, pricey, short shelf life, and probably overkill as some people have pointed out. I just wanted something different instead of just copying some one else. Thus the 904 leading edges were born. PePe seems to like them, as It makes him feel invincible!

 

[Rob702Martinez]

Might be a dumb question but, can you color this stuff with pigment like you would rocketpoxy or other epoxies?

 

[Greg Furtman]

Might be a dumb question but, can you color this stuff with pigment like you would rocketpoxy or other epoxies?

No clue. You'd have to contact the manufacturer.

 

[HyperSonic]

Might be a dumb question but, can you color this stuff with pigment like you would rocketpoxy or other epoxies?

This is not a dumb question. I have thought about it myself. I've never done it before and don't know if there would be any chemical reaction going on. White is a good color to tint. If I had some pigment laying around, I would try it. I also thought about mixing some epoxy with it to try and improve it's gripping strength. When it dries it is hard and brittle. If you just painted it on a CF fin, some of it would chip off when sanding. (you will hate sanding this stuff) By thinning it out a little so it can penetrate into the fibers of fiberglass cloth tape, then draping it over the leading edges and keeping an eye on it so it wont lift up (it will try) off the fin, within 10 minutes or so the outside will start to cure enough to keep it in place. I totally understand why this stuff is not used much if at all in the aerospace industry. Maybe a variation of it. When I went to the website Greg told me about above, they have a selection of ceramic adhesives and high temp epoxy's. Some even come in different colors.

I'm willing to send you some 904 and some thinner for you to play with if you like. I am done with it for now, and it has a 6 month shelf life (like most things cotronics sells) that is only 2 month old right now. Why am I doing all this? Because I want to become a member of the "Stupid Fast Club" The main requirement for joining is to hit or exceed Mach 3. I think PePe can do it!!!! Of course you must also have a safe recovery. No lawn darts allowed.

 

[Charles_McG]

Choroplantinic acid on zirconia (tetragonal, not cubic, nor monoclinic) yields a nice salmony color.

Probably not useful for this application.

 

[Rob702Martinez]

This is not a dumb question. I have thought about it myself. I've never done it before and don't know if there would be any chemical reaction going on. White is a good color to tint. If I had some pigment laying around, I would try it. I also thought about mixing some epoxy with it to try and improve it's gripping strength. When it dries it is hard and brittle. If you just painted it on a CF fin, some of it would chip off when sanding. (you will hate sanding this stuff) By thinning it out a little so it can penetrate into the fibers of fiberglass cloth tape, then draping it over the leading edges and keeping an eye on it so it wont lift up (it will try) off the fin, within 10 minutes or so the outside will start to cure enough to keep it in place. I totally understand why this stuff is not used much if at all in the aerospace industry. Maybe a variation of it. When I went to the website Greg told me about above, they have a selection of ceramic adhesives and high temp epoxy's. Some even come in different colors.

I'm willing to send you some 904 and some thinner for you to play with if you like. I am done with it for now, and it has a 6 month shelf life (like most things cotronics sells) that is only 2 month old right now. Why am I doing all this? Because I want to become a member of the "Stupid Fast Club" The main requirement for joining is to hit or exceed Mach 3. I think PePe can do it!!!! Of course you must also have a safe recovery. No lawn darts allowed.

That would be awesome! I can definitely test that out as I have many different colors. Thank you!

 

[G_T]

I'd recommend being careful about thinning... General rule of thumb: Epoxy type materials lose perhaps 40% of their cured mechanical properties from 5% thinnning. Going by memory. Thinning is quite bad for them unless the right thinner is used, and even then it is only bad. Thinning percentages need to be extremely small. For this particular product, I don't know. I'm just stating the general case.

If your pigment for instance breaks down at a lower temperature than your ceramic coating, or has a higher thermal conductivity, or is chemically reactive at high temperatures, or has a different coefficient of thermal expansion, or interferes with the coating process, alters the cured mechanical properties, alters the ability to radiate heat, or interferes with the surface bonding... Get the picture? If you want a technical coating, don't mess with it. Not without research and/or testing. 0.02c. It is up to you whether you are looking for show or for go.

Gerald

 

[HyperSonic]

I'd recommend being careful about thinning... General rule of thumb: Epoxy type materials lose perhaps 40% of their cured mechanical properties from 5% thinnning. Going by memory. Thinning is quite bad for them unless the right thinner is used, and even then it is only bad. Thinning percentages need to be extremely small. For this particular product, I don't know. I'm just stating the general case.

If your pigment for instance breaks down at a lower temperature than your ceramic coating, or has a higher thermal conductivity, or is chemically reactive at high temperatures, or has a different coefficient of thermal expansion, or interferes with the coating process, alters the cured mechanical properties, alters the ability to radiate heat, or interferes with the surface bonding... Get the picture? If you want a technical coating, don't mess with it. Not without research and/or testing. 0.02c. It is up to you whether you are looking for show or for go.

Gerald

Excellent advise as always Gerald. IMHO the 904 even if it was not thinned at all, would not have what it takes to hang on to the leading edges when traveling at extreme speeds. It needs help. It is good at protecting from friction and heat, but any air gets underneath it, and it will be gone. To give the 904 a helping hand on PePe, there are 3 coats of high temp epoxy covering the entire fin can including the 904 leading edges. My thinking is the epoxy will act as an ablative and take the brunt of the force protecting the 904 underneath for a short period of time. After that it's up to the 904 to carry the load. Should the 904 get ripped off, there is still more high temp epoxy under that. This 3 layer approach is geared to buy me the valuable time needed to get back under say Mach 2, where nothing is needed because it will be at altitude by then. This is all theory, and I have never done this before. The 904 on PePe is all about the GO, and not so much the show.

I want to share something with you Gerald, while I have you here. When I vac bagged the first section of PePe's fin can when doing the tip to tip, It came out with a bunch of wrinkles and air bubbles. Then I found your thread (sticky) on fiberglass techniques and read it. On the next section (I did one section at a time) I only coated the airframe with epoxy, and not the CF that was going over the airframe. It came out much better than the first section that I coated both the airframe and the CF, trapping air between them. Of course the 3rd and 4th section got better and better. Not perfect, but much better than the first, and I have you to thank for it! Thank's for sharing your knowledge with all of us!

One more thing before I go. What epoxy do you use to make your threads so sticky? I am just kidding with you. We all here know the answer to that one!!!!!

 

[rocket_troy]

My thinking is the epoxy will act as an ablative and take the brunt of the force protecting the 904 underneath for a short period of time

I'm no expert on epoxies so feel free to correct me, but I was under the impression that most epoxies are of a thermoplastic chemistry rather than thermoset ie. they soften then melt beyond temperature thresholds rather than stay solid then ablate. High temp epoxies might differentiate themselves on this very point - i have no experience with them.
Did you ever consider making the entire fins from a ceramic composite so the bonding issue is less of a concern?

TP

 

[HyperSonic]

I'm no expert on epoxies so feel free to correct me, but I was under the impression that most epoxies are of a thermoplastic chemistry rather than thermoset ie. they soften then melt beyond temperature thresholds rather than stay solid then ablate. High temp epoxies might differentiate themselves on this very point - i have no experience with them.
Did you ever consider making the entire fins from a ceramic composite so the bonding issue is less of a concern?

TP

I probably used the wrong word. Lets exchange the word ablate with the word melt. The Tg on this epoxy is 600 F. After that, It's the 904's turn. It's good for 4000 F. Since it is thinned, It might drop down to 2000 F. Then were back to the epoxy again. I have never gone fast enough to melt anything before, so this is just wishful thinking. I will surely post some pics after the flight, and then we will see exactly what melted, and what didn't.

If my fins were all ceramic, (I can only speak for the 904, as I have no experience with any others) they would be very heavy, and brittle. I'm not sure what I would use to attach them to the airframe that would handle extreme speeds. With to much weight, there would be no extreme speeds without using more thrust. This flight is all about speed and staying light as possible. Not record breaking speed, but fast enough to shred if things get even a little out of control.

 

[rocket_troy]

Good points. Yeah, an all ceramic fin would definitely be too brittle.

TP

 

[G_T]

Ceramics, are a rather broad range of materials. Do you know that some gears are made of ceramic materials? Personally, I'd also classify the nozzles of the SRBs as somewhere between a ceramic and a composite. C-SiC composite in a carbon matrix. Not that they were necessarily made this way, but make a carbon fiber layup with silicon metal powder in phenolic as the matrix. Cure, then bake at progressively higher temperatures, to remove high temp volatiles and promote silicone carbide whisker growth. Vacuum or at least inert atmosphere required. It should work for a nozzle, so should probably work for a fin.

You could consider a Niobium leading edge strip https://www.reactivemetals.com/niobium Pricy but can take some temperature, and doesn't have high thermal conductivity. Carefully fold and find some way to attach. Sorry, just throwing something OT and out of the box out there . I'm bad that way!

Gerald

 

[Wallace]

Have you considered something along these lines? The key would be getting the rods set at the correct angle? A jig maybe? I have a small (think pencil sharpener sized) handheld version and it works "pretty" well on ceramic kitchen knives.https://www.homedepot.com/pep/Kitch...b-6hjG6fIBGhrtE0bkhoCRaQQAvD_BwE&gclsrc=aw.ds

 

[HyperSonic]

Ceramics, are a rather broad range of materials. Do you know that some gears are made of ceramic materials? Personally, I'd also classify the nozzles of the SRBs as somewhere between a ceramic and a composite. C-SiC composite in a carbon matrix. Not that they were necessarily made this way, but make a carbon fiber layup with silicon metal powder in phenolic as the matrix. Cure, then bake at progressively higher temperatures, to remove high temp volatiles and promote silicone carbide whisker growth. Vacuum or at least inert atmosphere required. It should work for a nozzle, so should probably work for a fin.

You could consider a Niobium leading edge strip https://www.reactivemetals.com/niobium Pricy but can take some temperature, and doesn't have high thermal conductivity. Carefully fold and find some way to attach. Sorry, just throwing something OT and out of the box out there . I'm bad that way!

Gerald

At work we have gears made from brass. The reason for this is to create a weak link in the chain so the brass gear will strip out first, thus protecting the components farther down. Much easier and less expensive to repair should something get jammed up. I will keep your ideas in mind when it comes time to build another fin can. I've put so much into this one (PePe) that I'm fin caned out. I'm just glad to be done with this one and can move on to more funner parts of the build. Stop by any time your in the neighborhood, as your 2 cents will always be welcome here!

 

[HyperSonic]

Have you considered something along these lines? The key would be getting the rods set at the correct angle? A jig maybe? I have a small (think pencil sharpener sized) handheld version and it works "pretty" well on ceramic kitchen knives.https://www.homedepot.com/pep/Kitch...b-6hjG6fIBGhrtE0bkhoCRaQQAvD_BwE&gclsrc=aw.ds

I have to be careful not to sand thru the 904 and into the fiberglass. This will create a hole where air can get underneath the 904 and rip it off when travelling at extreme speeds. If they were solid ceramic like rocket_troy was talking about above, then I could see using this sharpener on them. Wouldn't that be something to see, sharpening your fins right before you launch your rocket.

 

[Wallace]

So it probably wouldn't work well as an afterthought?

 

[HyperSonic]

So it probably wouldn't work well as an afterthought?

I am not sure what you mean when you say "Have you considered something along these lines? The key would be getting the rods set at the correct angle? A jig maybe? " I took this as you were saying to sharpen the leading edges with a sharpener. Is that what you meant? If not, could you explain further?

 

[Wallace]

Sounds like Ya got the idea. What you're apparently saying is unless the underlying shape is perfect then even if the sharpener rods did work, they'd "burn through" in at least some areas. Is that correct? If so, that was my intent, would not work well as an afterthought. But...Not that it would be easy (or even possible) say if you pre-profiled the bevels with a tool with the same angle then applied ceramic, the tool should give uniform/contestant thickness. Point being, it's too late in the game for your existing fins.....

 

[HyperSonic]

Sounds like Ya got the idea. What you're apparently saying is unless the underlying shape is perfect then even if the sharpener rods did work, they'd "burn through" in at least some areas. Is that correct? If so, that was my intent, would not work well as an afterthought. But...Not that it would be easy (or even possible) say if you pre-profiled the bevels with a tool with the same angle then applied ceramic, the tool should give uniform/contestant thickness. Point being, it's too late in the game for your existing fins.....

Ok, I understand now what you mean. The bevels started out very consistent from top to bottom in the beginning, before adding one layer of the tip to tip, more epoxy, then the 904 coated fiberglass tape over that. Tried to squeegee it with my fingers the best I could to remove excess 904 from the fiberglass tape. After all that there is some waviness now since all this was done by hand. Not that bad, but would cut more in some areas than in others. When sanding the 904 before applying more epoxy, I sanded through in a few places. I touched it up with more 904, then added more epoxy on top. That is where I'm at now. The bevels started out with a .070 inch round diameter. Now they are much wider, still rounded. I will take some more pics of the fins after I get done sanding them. I'm up to 320 grit and they are smooth as silk, but scratchy looking. I want to put one more thin coat of epoxy, wiped on with my fingers to bring back the beauty of the CF. If I were to sand it one last time, and went up to say 1000 grit (maybe wet sand) would the beauty of the CF return? I'm after the see thru look.