Submicron Calcined alumina powder

[Southbound]

I have a sample of very fine abrasive powder from a company, and I am trying to figure out how to suspend it and disperse it onto my substrate. I have a probe sonicator, for agitating, but I can't find out what the appropriate liquids would be . I have tried ethanol, but when it dries it agglomerates again. I am not wanting it totally wet in a slurry, but I want it to stay 'somewhat' tacky/intact were I spray it.

 

Based on my reading this type of Calcined alumina works in a acid environment, of about 3.5 - 4.  I tried an ethanol 80% to 20% glycerin and it seemed to be the most effective, but how do I go about lowering the ph of my solution, ethanol is somewhat alkaline? I only mix a 0.5 oz at a time to spray disperse on my substrate. 

I also thought about silicone lubricant/oil? Not sure what the ph is in these types..

 

Edit: I am just experimenting. I just poured a cup of distilled water and got it almost boiling then I added 10% glycerin I added/dissolved 1/8 tsp of citric acid. I don't have anything to measure ph yet,but based on what I have read that should be about ph of 3.5. I then poured 0.5 oz of liquid in a container, added 0.30/1/8 tsp.abrasive powder, then probe/sonicated the mixture them I added to my 0.5 oz spray bottle then I sprayed in my substrate.

Edited January 4, 2021 by Southbound
I updated my experiments results

[Bufofrog]

Have you tried an aqueous solution?  I have worked with aqueous colloidal silica and pH is vital to keep the particles from clumping (floccing).  You can order pH papers from Amazon.  I would use NaOH and HCl to control the pH.

[Southbound]

Hi,

Not sure what a aqueous solution exactly is, but does it involve distilled water and an acid? Can I make my own aqueous solution? Sorry but I am not very familiar with chemistry, but I am interested..

Roughly do you think I got my pH to about 3-3.5 using 1/8 tsp of citric acid in a cup of distilled water?

 

 

51 minutes ago, Bufofrog said:

Have you tried an aqueous solution?  I have worked with aqueous colloidal silica and pH is vital to keep the particles from clumping (floccing).  You can order pH papers from Amazon.  I would use NaOH and HCl to control the pH.

So hydrochloric acid will dissolve the Calcined alumina?

 

[Bufofrog]

1 hour ago, Southbound said:

Not sure what a aqueous solution exactly is, but does it involve distilled water and an acid? Can I make my own aqueous solution? Sorry but I am not very familiar with chemistry, but I am interested..

Sorry for any confusion, aqueous just means water.

1 hour ago, Southbound said:

Roughly do you think I got my pH to about 3-3.5 using 1/8 tsp of citric acid in a cup of distilled water?

Sounds like that is too little. Around 8 grams per cup should be close to a pH of 3.  I would use a strong acid or base instead of a weak acid like citric.

1 hour ago, Southbound said:

So hydrochloric acid will dissolve the Calcined alumina?

No, the acid will cause the particles to become charged so that they will repel each other and remain in suspension.

I believe this all accurate information but I am a chemical engineer, which means I am definitely NOT a chemist, one of the chemist on the site will join in if I am leading down the wrong path.

Edited January 4, 2021 by Bufofrog

[Southbound]

1 minute ago, Bufofrog said:

Sorry for any confusion, aqueous just means water.

Sounds like that is too little. Around 8 grams per cup should be close to a pH of 3.  I would use a strong acid or base instead of a weak and like citric.

No, the acid will cause the particles to become charged so that they will repel each other and remain in suspension.

Thanks for helping, but you must be patient with me I am no chemist. So straight muriatic or hydrochloric acid will dissolve calcined alumina, so what you are saying a aqueous solution which is diluted will no harm the particles, but put a charge or barrier and keeping them de-agglomerated? So what about muriatic acid? If so how much per cup of distilled water? I am only using 1/8 tsp of calcined alumina per 0.34 oz, so does that sound like too much?

 

Above I mentioned using a very small amount glycerin in the solution to help keep the abrasive from drying on my substrate, I so would a substance like glycerin work with a strong acid? 

 

The sonicator does really make a milky solution, but I really don't need them to stay agglomerated for long periods of time, (because I only mix this when I need to reload my strops/substrates) but my question I don't guess this acid doesn't have any effect on helping the particles stay deagglomerated after they are sprayed on the substrate - They only keep the agglomeration at bay while the particles are in my bottle before I spray? Or will this charge you are taking about make a big difference on how they are dispersed on my substrate?

 

[Southbound]

1 hour ago, Bufofrog said:

Sorry for any confusion, aqueous just means water.

Sounds like that is too little. Around 8 grams per cup should be close to a pH of 3.  I would use a strong acid or base instead of a weak acid like citric.

No, the acid will cause the particles to become charged so that they will repel each other and remain in suspension.

I believe this all accurate information but I am a chemical engineer, which means I am definitely NOT a chemist, one of the chemist on the site will join in if I am leading down the wrong path.

I trust your data... Glad I joined! I definitely work with muractic acid, because I am a mason by trade and we have to use it to an our bricks, I know muractic acid and hydrochloric acid are close to the same but muractic may have some impurities.  I just was wandering , if muractic acid would be good enough for my experiment? 

I was reading up and it definitely works better at a ph of 4. So if I am mixing small amounts,  so we will go with 300ml/1 1/4cup of distilled water (I assume distilled water is ph 7??) and how many ml's of muractic acid to add to 300ml of water to get a ph of 4. So after I get the liquid solution to the ph of 4, could I then transfer 0.5 0z of the fluid to my plastic mixing bottle then add the 0.30g of calcined alumina to agitate/sonicate?

Can I incorporate maybe 5-10% glycerin?  If so do I do this after I lower the ph of the water or before?

So this will also aid in keeping the particles from agglomeration after I spray on my substrate?  Or only in the bottle,  prior to spraying?

 

Thanks, 

 

Mike