Creating a colloidal suspension with MOS2/hBN ?

[Mixologist]

Hi guys, I'm wondering what it takes to create a good colloidal suspension with MOS2 and/or hBN. Obviously the smaller the MOS2/hBN the better but at what size does one start to see MOS2/hBN fall out of solution. Is it as simple as simply adding the dry MOS2/hBN to a base oil or do you need a catalyst (heat/binder/etc.) in order to maintain the suspension in a homogeneous/mostly-homogeneous state?

Has anyone ever tired running an oil + DI pack through a centrifuge? If not I'll do it when school starts up again next month.

I tried searching for this as I'm sure it's been covered already but I couldn't find anything.

 

[JHZR2]

If you have to ask this, youre not qualified to make such a thing.

Harsh but seriously, a LOT can go wrong when working with colloidal samples. Surface energy optimization to create stable particles is of key importance.

Id suggest starting by reading up on DLVO theory, not that motor oil is really an ionic liquid, but because it is a good start on things that might be considered. Then start reading up on surfactants and how they work. Surface chemistry is key here.

 

[Mixologist]

Originally Posted By: JHZR2
If you have to ask this, youre not qualified to make such a thing.


I understand what you're saying but anyone willing to humor me a bit? I do understand van der Waals forces and ionic bonds and the like as I am in the last few days of getting a masters degree in mechanical engineering so it's not like I'm clueless, just not as chemically smart as some of you may be. My specialty is turbine engine systems.

 

[JHZR2]

The problem is that it is a VERY complex situation. It has to do with particle size, density as well as density, surface tension and viscosity of the dispersion medium.

But the chemical interactions, the physical surface chemistry is key. The major role is the energetic factors related to the interaction of the additive, the lube oil base, oxidized/degraded bulk lubricant and any other surface active things that may come in... such as water especially. Surface acidity is critical to understanding how the materials interact, as the micellar actions that occur from surfactant interactions and the hydrophobicity/hydrophilicity detrmines how well the chemistry will stay stabilized.

A lot of experimentation on the surfactant stabiity will be necessary. Also, sometimes small particles are too smal and will re-agglomerate to larger particles while in suspension.

The attached document will be good reading:
http://chentserver.uwaterloo.ca/aelkamel...-engine-oil.pdf

 

[Mixologist]

OK I just made it though all 17 pages (thanks for the info) and what I'm getting from that when boiled down is that I would need a a surfactant which makes sense and some sort of dispersant to keep the individual particles from reforming and in-effect flocking out of suspension/getting caught by a filter.

So just for the sake of argument do you think the existing DI pack in your run of the mill motor oil has in excess enough surfactant/dispersant to accommodate say a 1% (by total volume, say 5 quarts) increase in hBN/MOS2 or do yo think that in order to attain that 1% increase one would have to supply more dispersant/surfactant?

If there were polar attractions between the particles but they were based in a non-polar medium like engine oil what could you use to negate that attraction until the hBN/MOS2 had a change to bond with the substrate i.e. steel/FE engine part?

How would or does the oxidation state of the oil come into play in say a simple 1% increase in hBN/MOS2? I'm not sure how that would be a factor.. but if it was could you simply add an antioxidant?

 

[JHZR2]

One would have to think that an HDEO, for example, which has the ability to disperse up to 4wt% soot, should have excess capacity. But, are those dispersants different? How does your particle surface chemistry vary compared to pyrolyzed carbon, asphaltines, and the like that forms in the oil?

Oxidation state isnt what I was implying. It was how oxidized the oil is. Presence of oxiation could effect the chemistry of the molecules in there and effect how they interact with the polar functional groups and the particle surfaces.

Dealing with polar (surface charged) particles in a nonpolar medium would require something with the right surfactant capability to have a miscible functional group combined with a polar/opposite charged head.

 

[Mixologist]

Originally Posted By: JHZR2
One would have to think that an HDEO, for example, which has the ability to disperse up to 4wt% soot, should have excess capacity. But, are those dispersants different? How does your particle surface chemistry vary compared to pyrolyzed carbon, asphaltines, and the like that forms in the oil?

Oxidation state isnt what I was implying. It was how oxidized the oil is. Presence of oxiation could effect the chemistry of the molecules in there and effect how they interact with the polar functional groups and the particle surfaces.

Dealing with polar (surface charged) particles in a nonpolar medium would require something with the right surfactant capability to have a miscible functional group combined with a polar/opposite charged head.


JHZR2, thanks for all the feedback. I've worked on it quite a bit since my first post the other day. I'll report back.

Thanks again!

 

[MolaKule]

Quote:
So just for the sake of argument do you think the existing DI pack in your run of the mill motor oil has in excess enough surfactant/dispersant to accommodate say a 1% (by total volume, say 5 quarts) increase in hBN/MOS2 or do yo think that in order to attain that 1% increase one would have to supply more dispersant/surfactant?



I know from my experiments that current formulations DO NOT have the reserve dispersant/surfactant capability to maintain any greater suspension capabilities than what they were originally designed for.

 

[Mixologist]

Originally Posted By: MolaKule
Quote:
So just for the sake of argument do you think the existing DI pack in your run of the mill motor oil has in excess enough surfactant/dispersant to accommodate say a 1% (by total volume, say 5 quarts) increase in hBN/MOS2 or do yo think that in order to attain that 1% increase one would have to supply more dispersant/surfactant?



I know from my experiments that current formulations DO NOT have the reserve dispersant/surfactant capability to maintain any greater suspension capabilities than what they were originally designed for.


Molakule/JNZR2 that makes since, why would they add unnecessary additives. Would diesel oil maybe be the exception to that?

Thanks for the feedback. Do you think one would need some sort of binder to create a colloidal suspension in a high percentage alcohol medium for example sub-mirco hBN in methanol/ethanol? Or perhaps a non-organic light weight oil bound to hBN in a solvent?