Study On The Dynamic Performance Of Rotating Carbon Nanomotor In Argon

With the development of nanotechnology,research on carbon nanotube(CNT)-based nanomaterials and nanodevices attracts much attention.CNTs have intertube superlubrication and intratube superhigh modulus and strength.Therefore,CNTs play ideal materials for manufacturing nanodevices such as nanomotors,nano-bearings,and nano-oscillators.Up to now,limited by the experimental techniques and equipment,the main method for research and development of CNT-based dynamic nanodevices is molecular dynamics simulation.In this thesis,dynamics behaviors of CNT-based nanomtor and carbon nanoring-based nanomotor in argon were studied,and following results were obtained for developing the related nanodevices:(1)We compared the dynamics behaviors of the CNT-based nanomotor in vaccum and argon.In the double-walled CNTs-based nanomotor,the outer tubes act as stators,and the inner tube acts as rotor.At finite temperature,thermal vibration of atoms on the rotor leads to collision between the rotor and the motor.During collision,the stators provide a unidirectional repulsion onto the rotor along its circumferential direction.Under the repulsion,the rotor is accelerated to rotating and obtains a stable rotational frequency(SRF)when the friction force from the same stator balances the driven force.The effects of temperature,density of argon,sizes of simulation box and the sizes of rotor on the value of SRF were studied.It is found that in a specific model,SRF exponentially decreases with increasing of density of argon.At 100 K,the rotor can keep rotating at fluidic argon.At room temperature(e.g.,300 K),SRF slightly depends on the density of argon which is less than200 kg/m~3.During rotating,some argon atoms are attracted on the inner and outer surfaces of the rotor and rotate synchronously with the rotor.For the same nanomotor in different sized simulation boxes with the same density of argon,the value of SRF is lower in a larger box due to more argon atoms attracted on the rotor.In the same simulation box,the value of SRF of the rotor with length>5 nm slightly depends on the lengths when density of rotor is low.(2)A tyre-shaped nanoring is formed by curving a CNT and bonded its both ends.Four short outer CNTs are adopted to confine the nanoring.Based on the same mechanism,the nanoring is driven to rotate by the stators.The dynamics behaviors of the nanoring in vaccum and argon were compared with consideration of such factors as density of argon,temperature,and length of stators.The nanoring cannot rotate at 100 K,but can rotate at 300K or higher,and the value of SRF increases with temperature.In argon environment at low temperature,argon atoms form into one or more clusters at the interface between the stators and the ring.If temperature is not too low,the clusters can be separated by the rotating ring gradually.Simultaneously,the rotational frequency of ring varies periodically.We also found that the ring can be stopped by reducing the temperature of the system.The reason is that the clusters become stronger at lower temperature,and provide stronger friction on the ring.Hence,this phenomenon can be used for design of an argon-based nano on-off to control the value of SRF of the nanoring.Above results provide potential application for guiding experiment and fabrication of rotary carbon nanomotors.Especially,argon can play a media to control the rotational speed of rotor.