Dear Salam,

The defect formed (if any) by the sonication on the walls of CNT can be studied using Raman Spectroscopy. It will show different D/G ratios for CNT without defect and CNT with defects. For good quality samples without defects and amorphous carbon, the D/G ratio is low and this ratio increases as the defects on the CNT increases. So, Raman can provide qualitative  information about formation of defects. 

The dispersion of CNT depends directly both on energy and time of sonication. For better dispersion without affecting CNT structure, they should not be too high. And too low can lead to insufficient dispersion. As mentioned above some of the reading articles will give you a good idea for your system. As well as some trials are required because the energy or time also depends on sonicator's capacity.

Hope this helps.

Dear Salam,

first thing to consider that the process of mechanical dispersion (by whatever means of dispersing action) proceeds with simultaneous agglomeration or in case of emulsions also coalescence. That is a key to successful dispersion is suitable stabilization. For processes with fast break-up of agglomerates fast kinetics of stabilization are required.

Therefore depending on your dispersion process and stabilization agglomeration or deagglomeration may dominate. Destruction of nanotubes may further complicate the process.

Dear Abderrahmane ,

Many thanks for your answer, indeed am doing my experiments in the same way you described (but I fixed the energy at 100 watt and am playing with the time and amplitude,pulse of the sonictor), the volume and and the concentration  are also constant with the same values for all the experiments. I have asked just to make sure that is the correct way in the optimizing  facile dispersion method. am doing to exam the result virtually, by Uvi-vis spectroscopy and from now i will use the laser  Raman spectrum to study the defect cased by the sonicator, then analysis the results might i will reach  the desired dispersion level with minimum defect on CNTs walls.

Regards 

Dear Titus, 

thanks a lot for your answer, Polycarboxylate ether superplasticizer I've used with the dispersion experiments( with constant ration 1:4 as its advised in many previous studies) as a stabilization agents, theirs is another surfactants could give a fast break up of the agglomeration CNTs but its not suitable with the cement matrix. In next experiments I will put in my mind your advice to look for the best susfictant which could limit the soincation time with the same or best dispersion efficiency.

Best Regards 

Dear Salam,

I'd like to refer a research article to you  that addresses the dispersibility and stability of CNT dispersion using either bath sonication or probe sonication. There are many good references cited in that article, too.

Generation of toxic degradation products by sonication of Pluronic® dispersants: implications for nanotoxicity testing

Nanotoxicology November 2013, Vol. 7, No. 7 , Pages 1272-1281 (doi:10.3109/17435390.2012.736547)

Major concerns, in addition to sonication power, time, and temperature, are

1) the type of dispersant used -- whether it is stable structurally to withstand the sonolytic damage and preserve its function as a dispersant, preventing dispersed individual CNT particles from agglomeration during/post sonication.

2) the concentration of dispersant used relative to the concentration of CNTs -- insufficient dispersant results in lower level of CNT dispersion and less stability.

Good Luck!

Dear Salam,

I think you should make sure some things below, before you consider that sonicator power and time are the main focus.

1. you choose the right surfactant

2. you use the surfactant and all dispersing procedure under very similar condition with other researchers on some previous studies (temperature, solvent)

3.the type of CNT (SW or MW or functionalization)

4. the ratio between CNT and surfactant.

5. the correlation between the optimum ratio CNT:surfactant with sonication time or power.

Best Regards

Dear Salam,

Before starting the experiments, keep in mind some of the points

1. Don't increase the sonication energy more

2. Don't increase the time for long period, it increases the temperature of sonicator.             Increase in time also give good dispersion but you can give 5 - 10 minutes rest time         for sonicator and continue for long period (so many hours). Remember one thing, long     period of sonication leads to defects in CNTs.

3. Select the appropriate surfactant and solvent, otherwise it will give solubility of CNTs       instead of dispersion

4. For better dispersion stability use probe sonicator instead of bath sonicator

Dont increase time or energy the CNT will break. You better try 3 Roll mill. It works

Dear Mohana,

Many thnaks for your comments, Indeed all of your points are in my mind and am trying to avoid the long time ( in hours) sonicator because of the side effects which you stated in your answer. I  am still  wondering whether the desired dispersion level  could be  happened in the early few sonication minutes or not? 

Best regards  

Dear Alisa, 

please let me know  if you have any study about dispersion CNTs with the 3 Roll mill machine.

Dear Salam,

CNTs dispersion within few minutes also takes place, but increasing in sonication time will effect on dispersion. Lot of literature available on CNTs dispersion. I am giving some of useful links......

http://www.sciencedirect.com/science/article/pii/S1359835X10002009

http://www.sciencedirect.com/science/article/pii/S0950061813004984

http://www.sciencedirect.com/science/article/pii/S0272884213006858

http://www.sciencedirect.com/science/article/pii/S0950061814000026

http://www.sciencedirect.com/science/article/pii/S0001868606002065

http://www.hielscher.com/nano_03.htm

https://www.google.co.in/url?sa=t&rct=j&q=&esrc=s&source=web&cd=2&cad=rja&uact=8&ved=0CCkQFjAB&url=http%3A%2F%2Fwww.mdpi.com%2F2073-4360%2F4%2F1%2F275%2Fpdf&ei=wOYwVNLuM5SUuATJx4G4CQ&usg=AFQjCNF7yhA7H0Hi2cEX9sSir61gHk4YTQ&bvm=bv.76802529,d.c2E

 I hope you can understand from previous reports...please read

Dear Salam,

The defect formed (if any) by the sonication on the walls of CNT can be studied using Raman Spectroscopy. It will show different D/G ratios for CNT without defect and CNT with defects. For good quality samples without defects and amorphous carbon, the D/G ratio is low and this ratio increases as the defects on the CNT increases. So, Raman can provide qualitative  information about formation of defects. 

The dispersion of CNT depends directly both on energy and time of sonication. For better dispersion without affecting CNT structure, they should not be too high. And too low can lead to insufficient dispersion. As mentioned above some of the reading articles will give you a good idea for your system. As well as some trials are required because the energy or time also depends on sonicator's capacity.

Hope this helps.

Addition to the mentioned literature above my advice is to using high frequency can be more safe way because it will lower the effect of the cavitation which will reduce your the deflections on the walls but the if you are able to use pulsed equipment it also can be helpful with the proper duration times or may be multiple frequency usage with without duration. Any way without experiment and the knowledge of your system that is my point of view. Good luck :)