couche concentrique

OBS: «couche» : Ensemble des états électroniques d'un atome caractérisés par un même nombre quantique principal.
OBS: «concentrique» : Qui a un même centre (en parlant de courbes, de cercles coplanaires, de sphères). [...] «Mouvement concentrique» : qui tend à se rapprocher du centre.
OBS: Voir aussi «couche» et «orbitale».

CONT: The idea of carbon nanotube based gears comes from recent progress in fullerene science and technology. Multi-walled and single-walled nanotubes have been successfully prepared and rapid advance has been made in controlling tube diameter, length, chirality and the number of concentric shells.
OBS: In physical chemistry, the term shell refers to any of the several electrons' paths or orbits as they resolve around the atom's nucleus.
OBS: ""concentric"": having a common center (as circles one within another).