Testing center ask me fine powder only.
Reviwer give the command like "The BET surface area measurements are also very good. The authors claim several times about the change in the hydrophilicity degree of the fibers (in introduction section) by several methods, but there is not experimental data to support this idea in experimental section. I recommend nitrogen adsorption-desorption experiments (BET) in order to evaluate the change in the C constant value." kindly help me to clear this command
You can put whatever fits in sample cell. Standard diameters are up to 2 cm. Two other things:
- You have to degas the sample at some temperature. Usually vacuum at around 200 ºC for carbon materials. However you need to be careful that your sample does not decompose, so your temperature might be lower.
- To make a meaningful measurement, the surface area of sample inside the cell should be around 10 m2. Lower than this the error will be large. Then, you need to put an appropriate amount of sample.
On the other side, I do not think that you will get any meaningful result from the C values of BET, since it is extremely sensitive to the fitting conditions.
If you want to study hydrophilicity, then water adsorption of water angle contact are much better choices.
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And be careful not to have condensed drops of water around the vessels' neck in the end of degassing! Some aluminum foil may help you to heat the necks as well.
Such fibers are likely to be of low SSA and thus Kr or Xe physisorption is probably required and not nitrogen.
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