Dear  Vipin

In the Two-step method, one of the important matters is the energy/density. This related to how much nanofluid you need to prepare. For example, if 30 minutes sonication with exact amplitude and frequency is enough for preparing 50 ml of a nanofluid. You cannot just multiply it by 40 for 2 liters! Each sonication device can support up to a maximum volume limitation. Following papers can help in this regard as well;

1-      Investigation on Ultrasonicaton Energy Density Effect on Size Distribution of Zinc Oxide (ZnO) Nanoparticles by Using Zeta-Sizer

2-      The effect of sonication energy and time on thermal conductivity of Glycerol base nanofluids

3-      Combined Influence of Size and Sonication on Constant Shear Viscosity of MgO-Ethylene Glycol Nanofluids

Concerning the longer sonication, the other problem is; more sonication than enough may cause breaking down the larger nanoparticles. I mean if you are working with the particles of 80 nm or larger, they may break to smaller particles with over-sonication.

Good Luck and Regards,

Mohsen

Thank you Dr Samy.

I will go through the above mentioned link. Thank you once again.

Please read the note given in below link

http://www.hielscher.com/power-ultrasound-for-particle-treatment-application-notes.htm 

Thank you.!

Are you personally using this particular ultrasonic processor?

You could take a look at Bandelin. We were happy with their product. 

Thank you Prof. Ifigeneia.

i will surely have a look at it.

I think using time for monitoring ultrasonication may be counterproductive because it is not a standard form of presenting the result. This is because there are different settings for different ultrasonic vibrator. However, the best way is use the energy impacted per unit volume of the nanofluids, in this way the experiment can at least be repeated using the exact energy/volume for the nanofluid prep.

In my Lab we use QSonica Q700 which can display the total energy density impacted in the nanofluids.

Mr. Adio, you are totally right. Time, energy levels and intervals can make a big difference. 

Thank you Mr. saheed..your help is greatly appreciated. 

So you believe that longer duration of ultrasonication may not necessarily result in a more stable nanofluid solution?

Yes I do believe that. In most cases for nanoparticle dispersion, extended ultrasonication period usually leads to reagglomeration (forming weak agglomerates) in which case the base fluid will fill the interstices of the particles. This will lead to unnecessary increase in viscosity, and will also affect stability.

There are publications that have discussed this. and I have experience same in one of my experiments, see

http://0-www.sciencedirect.com.innopac.up.ac.za/science/article/pii/S0735193315001992

Regards

Saheed.

Dear  Vipin

In the Two-step method, one of the important matters is the energy/density. This related to how much nanofluid you need to prepare. For example, if 30 minutes sonication with exact amplitude and frequency is enough for preparing 50 ml of a nanofluid. You cannot just multiply it by 40 for 2 liters! Each sonication device can support up to a maximum volume limitation. Following papers can help in this regard as well;

1-      Investigation on Ultrasonicaton Energy Density Effect on Size Distribution of Zinc Oxide (ZnO) Nanoparticles by Using Zeta-Sizer

2-      The effect of sonication energy and time on thermal conductivity of Glycerol base nanofluids

3-      Combined Influence of Size and Sonication on Constant Shear Viscosity of MgO-Ethylene Glycol Nanofluids

Concerning the longer sonication, the other problem is; more sonication than enough may cause breaking down the larger nanoparticles. I mean if you are working with the particles of 80 nm or larger, they may break to smaller particles with over-sonication.

Good Luck and Regards,

Mohsen

Thank you Mr. saheed but the link given by you is actually leading me to University of Pretoria website...Can you please share the article name?

Thank you

Thank you Prof. Mohsen for your elaborate reply. I will surely go through the articles suggested by you.

But Prof., i have one doubt.You said that longer sonication will lead to breaking down of larger nanoparticles into smaller fragments. Don't you believe that its actually a favourable situation since smaller nanoparticles lead to higher effective thermal conductivity of the nanofluid.

Dear Vipin

What you mentioned is correct (smaller nanoparticles provide more thermal conductivity for nanofluids), however, we must not forget what we are looking for? Let me offer you an example; I am a researcher and when I would like to investigate the effect of size on specific nanofluid (20 nm, 50nm and 80nm), therefore, if I over-sonicate the 80nm and some parts break down to smaller parts, therefore, they are not 80 nm anymore, and I cannot release the data as 80nm.

Regards,

Mohsen

Thank you Prof. Mohsen.

Now i understand what you are trying to say.Thanks once again.

Hello  Vipin,

The title of the article is " Experimental investigation and model development for effective viscosity of Al2O3–glycerol nanofluids by using dimensional analysis and GMDH-NN methods"

Regards

The purpose of sonification is to ensure nanoparticle suspension stability

in fluids which in turn reduces agglutination and agglomeration tendencies. Stability of suspended nanoparticles are however checked by absorbance or transmittance index obtain through spectroscopic analysis obtained from an adequate UV spectrometer (preferably a double beam type).

In conclusion, sonification time monitored through obtained transmittance or absorbance index is the simplest approach for obtaining homogeneous nanofluid mixture.

This is because most sonicator are designed with enough dispersion energy.