u can take TEM images at very high magnification.. and then by using TEM software u can calculate the diameter of walls....

Thank u Shivani, That I have done. But what I meant is that if I can take an average diameter, of a number of MWCNTs. In TEM, normally I do not get more than 3/4 CNTs in a frame and in SEM , I get many CNTs but I can not get any diameter distribution out of it. Since, this is not SWCNT so there is no RBM to help me in Raman spectra. Is there any other available way ?

In nanoparticle research, XRD peak width can be used to deduce average particle sizes. Whether this is possible for the MWCNT, I am not sure, because the chirality may differ between the different nanotubes. Just contact a XRD specialist for help.

Thank u Elisabeth.

Rightly said, XRD width will provide average diameter, TEM visuals and scale of magnification will provide individual tube diameter. Raman could have provided had you seen RBM which is normally difficult in MWNT. But the story does not end here, there will also be a length distribution. Again whether XRD gives you a peak based on lenth or dia will be a question. May be if there is large difference between average dia and average length, you get both averages in XRD. Otherwise you rely on multiple TEM measurement data.

The most accurate way is possibly TEM micrograph analysis. I suggest optimising your TEM sample prep to get around ~20 MWCNTs per micrograph (increase the concentration of MWCNs in your suspension). Then you should use an automated image analyser. If you measure ~200 MWCNT (~10 micrographs) you will have a good idea of the average diameter of your batch.

Another way is to measure the diameter of your catalyst particles which dictate the diameter of MWCNTs.

Hi Seyyed, Thanks for the answer. Actually I produce CNTs on Inconel 600 without external catalyst. I have got some TEM images but they have maximum 3-4 CNTs per frame.

I seem to produce TEM samples in very bad manner. Can you guide me on this issue ?

Preparation of CNT samples for TEM depends on the quantity and quality of CNTs. The most important part of preparation is making the master suspension. You should make and sonicate a suspension which is thick enough to look like black ink. Then you need to drop cast on a TEM grid. If it is too concentrated, you will end up with large agglomerates and bundles of MWCNTs which is not good. If it is too diluted, you will have the problem you are facing now. I don't know the yield of your synthesis, but you should have at least 100 mg to be able to make a thick-enough suspension.

Dear Rajib,

First of all you have to keep in mind that if you have a batch of production lets say about 10g of CNTs, you can't have an accurate estimation of the distribution because imagine the quantity of nanotubes that you are looking in the SEM or TEM. If you measure 10, 20, 100 or even 1000 individual nanotubes, do you think that it would be correct to say that based on those nanotubes the average of the 10 grams will be the same? Nevertheless i think that the best way to measure the diameters in CNTs is by AFM.

I hope this was helpful and i look forward for your feedback.

Cheers

If you have SEM and TEM data just measure the diameter on screen of the single MWCNT. You do not need a better method. Yes you can average over the distribution of measurement of large data in many fields of view.

Only TEM give you the soluation other wise no instrument can not give this information ...even raman also