EuPhO 2018, Експеримент — Задача 4. Coda

• 6 nm

  Official value d = 6.0 ± 0.5 nm; the solution adds that SEM images show an average channel diameter of about 15 nm.

In this part, we can determine diameter of pores, using results, obtained in previous parts:

In part A we derived the equation

It yields

Where $v$ is thermal velocity of $CO_2$ ($T \simeq 300K$, more accuracy isn't needed):

$V$ is volume of the cylindrical vessel, it can be measured ruler:

Numerical answer is:

Here you can see the surface image of the membrane studied in this experimental problem. This image was obtained with scanning electron microscope (SEM). Average diameter of channels is about $15\ nm$. The reason of difference between these experimental results is that diffusion inside pores is not the only limiting stage even with two fans are turned on. Moreover, some fraction of channels is branched and terminated (A.A. Noyan et al. / Electrochimica Acta 226 (2017) 60–68).

This problem was developed and designed by Alexey Noyan, Alexander Kiselev and Fedor Tsybrov. Samples of anodic aluminum oxide were fabricated in MSU by Kirill Napolskii, Alexey Leontiev, Ilya Roslyakov and Sergey Kushnir.

If you have any questions about this experimental problem, please don't hesitate to contact the author noyan@phystech.edu.