Black phosphorus is not stable when it is exposed to air. When covered or terminated by single layer carbon atoms, such as graphene/carbon nanotube, it is more strongly protected in the rapid degradation than the bare black phosphorus. What's more, due to weak interaction between phosphorus atoms in black phosphorene, the nanotube obtained by curling single-layer black phosphorus is not as stable as a carbon nanotube (CNT) at finite temperature. In present work, we recommend a new 1D material, i.e., composite double-wall nanotubes (DWNTs) from a black phosphorus nanotube (BPNT) with a CNT. The dynamic response of the composite DWNTs is simulated using molecular dynamics approach. The effects of such factors as temperature, slenderness and configurations of DWNTs are discussed. Comparing with a single-wall BPNT, the composite DWNTs under uniaxial compression shows some peculiar properties. When the BPNT is embedded in a CNT, the system will not collapse rapidly even if the BPNT has been damaged seriously.

Many factors can have a significant influence on the output power of a thermally driven rotary nanomotor made of carbon nanotubes (CNTs). Making use of a computational molecular dynamics approach, we evaluate for the first time the output power of a nanomotor, considering some of the main factors including temperature, the diameter of the rotor and the number of IRD atoms (N) on the stator. When applying extra-resistant torque to the rotor to let the stable value of the rotational frequency of the rotor fluctuate near zero, the value of the resistant torque can be considered as the output power of the rotor. The effects of these factors on the output power of a motor are roughly predicted via a fitting approach. Using stepwise regression analysis, we discover that N has the greatest influence on the output power. The second and the third main factors that affect the output power of a nanomotor are the diameter of the rotor, and the interaction between N and the diameter, respectively. To improve the output power of a nanomotor, one can place more IRD atoms in the system and/or employ CNTs with larger diameters.

For a resonator-based nano-balance, the capability of capturing a nanoparticle is essential for it to measure the mass of the particle. In the present study, a clamped-clamped nanobeam from a Boron-Nitride and Carbon (BNC) nanotube acts as the nano-balance, and a fullerene, e.g., C60, is chosen as the particle, and the capturing capability is quantitatively estimated by the minimal escape velocity (MEV) of the fullerene from the nanobeam after collision. When centrally colliding with the nanobeam, the escape of fullerene depends on both incidence of fullerene and temperature of the system. When the colliding in the Boron-Nitride (BN) area of the beam surface, the nanoball escapes easier than that at the carbon area. The MEV of the nanoball is lower at higher temperature. As the nanoball sometimes slides for a few pica-seconds on the beam surface before being bounced out, the nanoball can escape only when the beam surface can provide the nanoball enough kinetic energy to overcome the van der Waals interaction between them. The capturing capability of the nano-balance can, thus, be improved by reducing the initial kinetic energy of the system.

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High speed power chucks are important function units in high speed turning. The gripping force loss is the primary factor limiting the rotational speed of high-speed power chucks. This paper proposes a piecewise model considering the difference of wedge transmission's radial deformation between low-speed stage and medium-to-high-speed stage, the friction forces of chuck transmission, and the compressibility of hydraulic oil in rotary hydraulic cylinders. A corrected model of gripping force loss is also established for power chucks with asymmetric stiffness. The model is verified by experiment results. It is helpful to use the piecewise model to explain the experimental phenomenon that the overall loss coefficient of gripping force increases with the rotational speed increasing at medium and high speed stages. Besides, the loss coefficients of gripping force at each stage during speeding up and the critical rotational speed between two adjacent stages are discussed. For wedge power chucks with small wedge angel (α<20°) and ordinary lubrication (μ 0 >0.06), the local loss coefficient of gripping force at the low speed stage is about 70% of that at the medium to high speed stage. For wedge power chucks with larger wedge angel (α>20°) or low friction coefficient (μ 0 <0.06), the wedge transmissions cannot self-lock at high speed stage, and the gripping force loss at the high speed stage is related to the hydraulic lock and hydraulic oil in the rotary hydraulic cylinder; the local loss coefficients of gripping force at the third stage is about 1.75 to 2.13 times that at the second stage. This work is helpful to understand the mechanism of the gripping force loss thoroughly and to optimize power chucks. high speed turning, power chuck, gripping force loss, rotary hydraulic cylinder, model, experiment Citation: Zhou C, Yang H Y, Yang L K, et al. Piecewise model and experiment of power chuck's gripping force loss during high speed turning. Sci China Tech Sci, 2011, 54: 972−982,