Phononic Origins of Friction in Carbon Nanotube Oscillators

Abstract

Phononic coupling can have a significant role in friction between nanoscale surfaces. We find frictional dissipation per atom in carbon nanotube (CNT) oscillators to depend significantly on interface features such as contact area, commensurability, and by end-capping of the inner core. We perform large-scale phonon wavepacket MD simulations to study phonon coupling between a 250 nm long (10,10) outer tube and inner cores of four different geometries. Five different phonon polarizations known to have dominant roles in thermal transport are selected, and transmission coefficient plots for a range of phonon energies along with phonon scattering dynamics at specific energies are obtained. We find that the length of interface affects friction only through LA phonon scattering and has a significant nonlinear effect on total frictional force. Incommensurate contact does not always give rise to superlubricity: the net effect of two competing interaction mechanisms shown by longitudinal and transverse phonons decides the role of commensurability. Capping of the core has no effect on acoustic phonons but destroys the coherence of transverse optical phonons and creates diffusive scattering. In contrast, the twisting and radial breathing phonon modes have perfect transmission at all energies and can be deemed as the enablers of ultralow friction in CNT oscillators. Our work suggests that tuning of interface geometries can give rise to desirable friction properties in nanoscale devices.

Nanomaterials in Superlubricity

“…As one of the many forms of 1D‐nanostructured materials, carbon nanotubes (CNTs) comprising of coaxial cylindrical graphene with various layers have been explored for their superlubric behaviors, which originate from their intrinsic structural characteristics that readily enable relative motion between concentric nanotubes along the concentric axis . Theoretical modeling and predictions have indicated an ultralow shear strength between inner and outer layers of double‐walled CNTs .…”

Термофорез Одноатомных Частиц В Открытых Нанотрубках

“…Тепловой поток вдоль нанотрубок может вызывать движение внутри нанотрубок наночастиц золота [6,7], нанокапель воды [8][9][10][11][12][13], вложенных нанотрубок [14][15][16] и молекул фуллерена C 60 [17,18]. Движение частиц внутри нанотрубок вызывается их взаимодействием с тепловыми фононами и происходит против градиента температуры: от теплого конца нанотрубки к холодному.…”

Термофорез углеродных наночастиц (нанолент и нанотрубок) на плоской многослойной подложке гексагонального нитрида бора (h-BN)

“…Явление термофореза также активно моделировалось для наночастиц, находящихся внутри углеродных нанотрубок: для отдельных атомов [12], кластеров ато- мов [13,14], нанокапель воды [15][16][17][18][19][20], вложенных нанотрубок [21][22][23] и молекул фуллерена C 60 [24,25]. Взаимодействие этих наночастиц с потоком тепловых фонов всегда приводит к их направленному движению от теплого конца нанотрубки к холодному.…”