In carbon nano tubes, single wall, double wall and multi wall carbon nanotubes are possible. In case of multiwall carbon nanotubes, maximum how many number of walls are possible.
as far as I remember from a meeting at the Max-Planck Institute of colloids and interfaces - Golm - Germany, the imperfectionness increases with the increase of the number of walls, but they didn't mentionned the maximum possible number of attained walls. Regards
Actually, the number of walls can affect your specimen preparation process. I recommend you to apply CNT with minimum accessible number of walls because in case of many walls, particles cannot bring the suitable achievements.