Attempting to make a ferrofluid

You forgot me again in the credits. :(

Bryan Boettcher

This has me excited. I’ve already ordered Ferric Chloride and Oleic Acid from eBay. :) A preparation method referenced by another YouTube video has no drying step. After heating to ‘near boiling’ until the ammonia smell goes away, they allow the solution to cool and add kerosene. The coated particles, being insoluble in water but soluble in kerosene, ‘migrate into the kerosene layer’. The web page with the procedure is defunct but Archive.org has it in The Wayback Machine. <a href="http://www.sci-spot.com/Chemistry/liqimag.htm" rel="nofollow noopener" target="_blank">http://www.sci-spot.com/Chemistry/liqimag.htm</a>

This is going to be odd, but it's still chemistry, so please bare with me. My significant other is a master at making the colloidal suspension we call Mayonnaise. I've never seen her's separate even after weeks in the refrigerator, and it is better than anything I've ever had store bought. So we compared notes between what you did and what she does. While Mayonnaise requires a phobic molecule (mustard powder in the case of Mayonnaise) attached to an oil in a protein solution, how you get the oil molecule wrapped in the phobic molecule is the critical step - not the molecules themselves. Her suggestion is that you not mix the Oleic acid into the magnetite solution, but slow, very slowly, like a drop every two to three seconds, add the magnetite to the Oleic acid while beating it vigorously (as in a blender,) not just stirring it. This will do two things: 1) it will keep the magnetite from clumping allowing the Oleic acid to more uniformly coat all sides of the magnetite particles, and 2) by beating rather than stirring it will promote a faster, more even diffusion of the magnetite throughout the oliec acid and that will become ridiculously necessary to prevent clumping (larger particles in other words) as the amount of magnetite you add increases. The real down sides of this is perhaps the amount of both ingredients you'll need to do this. Using more of each will be more expensive and take longer because the rate of addition must remain the same, but it will be easier to beat appropriately, if that makes sense. As she put it, "Making a colloidal suspension is delicate work, but it is not fragile. Beat the crap out of it more than if you were making whipped cream." It is certainly a different way of looking at the needed process, which she points out is more physical than chemical at that point in the preparation.

Mark Bryant

Have you thought about using an electric pH device? I was using pH paper for a long time, but bought a pool pH tester for about 15€ and it shows the pH more reliable (with .0 digits) and faster than the pH paper.

Never heard of that before, but i am considering getting one

Nile Red

I second that

Nile Red

Not ignorant at all! To clean it, i just wipe it down with a paper towel and then wash with really strong dish soap.

Nile Red

Oh, okay, cool!

Nile Red

Yes please.

Michael Aichlmayr

Not related to this post, but got to thinking of this when making coffee. For filtration of smaller volumes, where you want to avoid vacuum, for example hot filtrations. Have you ever attempted to use an aeropress? This nifty coffee-maker should speed up filtration considerably compared to normal gravity filtration. <a href="https://www.amazon.com/AeroPress-Coffee-and-Espresso-Maker/dp/B0047BIWSK" rel="nofollow noopener" target="_blank">https://www.amazon.com/AeroPress-Coffee-and-Espresso-Maker/dp/B0047BIWSK</a>

I should probably mention that I'm not just trying to make graphene (which can be made hydrothermally from several sugars), but trying to convert a specific starting material. When I have some definitive results I'll share.

Michael Aichlmayr

Would Iron ammonia chloride or Iron ammonia citrate work better it would not oxidize as much.

Daniel Blake Shoemaker

Very cool. Maybe you need a proper device to make the Iron iron particles fine as properly made. Maybe the Oleic acid got oxidized and that may be why it failed. Maybe invest into something that can make magniate.

Daniel Blake Shoemaker

A few years ago a group of my genchem students made a ferrofluid for their project, and it was successful. I should look up which prep they used.

Andy Aspaas

With the commercial ferro fluid has anyone who's worked with it noticed a particular scent? It's almost like... An alien BBQ? 👾 I have gotten a couple of very small containers of it for artistic purposes and it's really fun to play withm Theres a bolt kit on Amazon thats pretty cool too which the thumbnail for the video reminded me of though I have regrettably not used it as a subject as I had planned to yet. That's ok I'm getting my ferro fluid fix from Nile anyway 😊 Anyway, what's the best method to clean it up? I usually have some kind of accident where it gets all over me and the house. It's wily stuff, good luck if you get it on the magnet lol Maybe kerosene cleans out up, would gas work? Not that I want to or think it'd be great to clean up with gasoline but it could it work if I had a disaster? I'm not a chemist, nor have I ever taken even a chemistry class but I find it fascinating even if I can't do any experiments myself, so please pardon my ignorance.

It might be brand specific.

Michael Aichlmayr

I don't believe I've made graphene yet, but I'm pretty sure I've managed carbon nanoparticles. I've made some that when suspended, fluoresce under UV. I was kind of excited, but a quick search reveals it's not new. 🙁 Still cool though, and I'm not finished, just sidetracked. I have a bunch more things to try.

Michael Aichlmayr

I don't think stirring alone will provide enough shear strength to break up clumps, especially since they may have a tendency to stick back together. But getting an ultrasonic bath should be easy, they use those all the time in electronics, jewelry and sometimes machining, to clean up PCBs and parts. Many people have those in their garages, and you can find them on ebay for ~$100. Another thing that may affect the "clumping" is pH : as you go to high pH, your particles acquire a negative charge from hydroxyl ions sticking to their surface (while the less coordinating cations available stay away). Conversely, at lower pH, they get positively charged. In-between is the isoelectric point, where they have no charge. That's where they'll stick together the most, so you'll want to be as far from it as possible. Unfortunately, it scarcely has a well defined pH value, and finding how to best adjust the pH would take some toying around (especially since you can hardly change it without changing the ionic strength of the solution, which would affect the aggregation too). And by "crystallize", I mean "go from an amorphous phase to a crystalline one". Essentially, what you get out of the precipitation is poorly organized FeII and FeIII ions haphazardly bound by O and possibly OH ligands, in no particularly well defined structure. It may occasionally adopt the magnetite unit cell locally, but most of it will be random. Needless to say, amorphous phases have quite variable and hardly predictable behaviors. By heating up for long enough, you allow those ions to reorganize themselves into the nice, more thermodynamically stable, repetitive pattern we call a crystal.

Gabriel J.

Also, when you say "crystallize" what exactly do you mean? I read it in several papers but i wasnt able to get an answer i liked about its definition. It just refers to the formation of the nanoparticle?

Nile Red

that looks pretty cool. Also, were you successful making graphene? Any cool results?

Nile Red

I am very much thinking that it might be. I will look into it.

Nile Red

Thanks for that! I will fix it in the final video :)

Nile Red

interesting. For the "purity" the reason I thought PCB etchant would be better, was because it would allow me to easily and accurately make the solutions in a 2:1 ratio. I also read in the comments of that guy i mentioned in the video, that he used PCB etchant with good results. So i have faith, but we will see. Also, your point about oxidized oleic acid is very true. That could very well be causing a big issue. I just finished another run with different condition and the results seemed very promising. All the way until the drying step. After that, the particles seemed to have issues going back into solution. They were completely "dissolved" in a soapy ammonium oleate solution though.

Nile Red

Thanks for your input! And yeah, i think sonication is definitely the proper way to go. However, i believe that it is possible to do it without any "specialized" equipment. Your point about breaking up the clumps before coating is a very good point. I kind of just suspended in ammonia solution and put in the oleic acid right away. Maybe stirring it for a while would be useful.

Nile Red

I can attest to the PCB enchant not being very pure.

Michael Aichlmayr

I was hoping Nessy on Twitter would elaborate on the procedure used. I swear someone mentioned some other surfactants, but can't find it now. If oleic acid oxidizes so easily, maybe that's part of the problem?

Michael Aichlmayr

I wonder if one of these hydrothermal reactors would be useful. I bought this one for making graphene. Much cheaper than an autoclave! <a href="https://www.amazon.com/Hydrothermal-Synthesis-Autoclave-High-pressure-Customizable/dp/B00JTE3UQY/" rel="nofollow noopener" target="_blank">https://www.amazon.com/Hydrothermal-Synthesis-Autoclave-High-pressure-Customizable/dp/B00JTE3UQY/</a>

Michael Aichlmayr

Interesting video. I did notice a slight typo at time 6:17. It looks like you mistakenly listed ammonium chloride rather than ammonium sulfate as a product of the reaction of ammonia, water, and ferrous sulfate. Keep up the good work!

I think another major problem might be because you used Oleic acid from ebay. Oleic acid is pretty easily oxidized by atmospheric oxygen and it can even start to crosslink (it is a semi-drying oil). The yellowness of the oleic acid also doesn't inspire a lot of confidence about the starting purity, before it sat for who knows how long in who knows what kind of storage conditions. Your drying steps in the air could also very easily start to oxidize the oleic acid. One more thing; commercial PCB etchant is normally not very pure at all, especially since it will become contaminated with other metals the moment when it first gets used. I would expect a couple of 1000s of ppm Copper, Nickel, Tin and Aluminium at least (assuming that it isn't reprocessed from industrial suppliers, who frequently recycle their etching bath solutions and hence accept much greater levels of impurities in their etchant baths).

"Do you think that sounds reasonable? Or you really think the 24h treatment is necessary?" Without XRD, it's impossible to tell for sure. But off the top of my head, it sounds both cold and short. (I did get rutile to crystallize at 60°C though, but that was in an acidic solution for at least 12 hours). As to the coating step, I spend most of my life painstakingly trying to do the exact opposite (make and keep the oxide surfaces molecularly clean), so I don't have much firsthand experience. But from what I've read in the litterature, amines (like oleylamine or dodecylamine) and sulfonates (like dodecylsulfonate) also stick quite well to metal oxide nanoparticles. An other thing that *might* help a little is sonication, to break up the clumps and help get the particles evenly coated. (Do so before and during the oleic acid addition. Sonication doesn't do much once the particles are in a high vapor pressure fluid.) That reminds me the old days in my undergrad, 7 years ago or so, when I too tried to make my own ferrofluid. Instead of oleic acid, I used whatever fatty acids I got by acidifying commercial soap (mostly palmitic I guess?) and instead of magnetite, I used "pyrophoric iron", which is what you get from thermal decomposition of Iron (II) oxalate. At the time, I thought it'd be small particles of metallic iron, but it turns out it's mostly FeO. Still ferromagnetic though. Needless to say, it didn't work. The particles never remotely got into suspension.

Gabriel J.

Awesome.

Im glad you liked it! I am hoping the next month or so, to have a good working procedure. We will see how that goes though

Nile Red

huh interesting. I found some preps that said it was possible at room temperature, so that was what i tried. What you are saying makes a lot of sense though. I recently tried it again, at 50C and then heated it for another hour at 50C. And the particles definitely seemed to be better. The paper that i got that prep from, also reported they were all close to 10-15nm. Do you think that sounds reasonable? Or you really think the 24h treatment is necessary? You dont have any experience with the coating step do you?

Nile Red

Where did you get your magnetite synthesis from? Looking at your process, I'm almost certain you mostly made amorphous iron (II,III) oxyhydroxide. I really don't think you can get proper, crystalline magnetite nanoparticles without some form of hydrothermal treatment after the initial precipitation. (I work on titanium dioxide nanoparticles and all syntheses require hydrothermal or solvothermal treatment to get anything reasonably crystalline. I very much suspect it's the same for the vast majority of metal oxides. The metal ions need to be able to move around to crystallize, and at room temperature in a liquid where they have no measurable solubility, it simply isn't going to happen.) I suggest you try heating your initial "magnetite" suspension however high you can go without the ammonia evaporation being too much of a problem, and leaving it stirring like that with a lid for 24h or so. (If you do so, maybe try it on a small scale first...) Ideally, you'd want a lab autoclave with a teflon skirt, but those are horribly expensive...

Gabriel J.

I've always wanted to make my own ferrofluid, and I thought I knew a lot about it, but already I've learned a lot more. I'm really looking forward to seeing your continued progress!

Michael Aichlmayr