Inquiry

language

联系我们
如果您有任何疑问,请立即联系!

News

Graphene nanoribbons grown in hBN stacks for high-performance electronics

2024-03-28

Graphene nanoribbons grown in hBN stacks for high-performance electronics

2023-10-15

Twist-Dependent Anisotropic Thermal Conductivity in Homogeneous MoS2 Stacks

Thermal transport property of homogeneous twisted molybdenum disulfide (MoS2) is investigated using non-equilibrium molecular dynamics simulations with the state-of-art force fields. The simulation results demonstrate that the cross-plane thermal conductivity strongly depends on the interfacial twist angle, while it has only a minor effect on the in-plane thermal conductivity, exhibiting a highly anisotropic nature. A frequency-decomposed phonon analysis showed that the cross-plane and in-plane thermal conductivity of MoS2 are dominated by the phonons with frequencies below 12.5 THz and 7.5 THz, respectively. As the interfacial twist angle increases, these low-frequency phonons significantly attenuate the phonon transport across the interface, leading to impeded cross-plane thermal transport. However, the in-plane phonon transport is almost unaffected, which allows for maintaining high in-plane thermal conductivity. Furthermore, our study revealed a strong size dependence for both cross-plane and in-plane thermal conductivities due to the influence of low-frequency phonons in MoS2. The maximum thermal conductivity anisotropy ratio is estimated as ∼400 for twisted MoS2 from our simulation, which is in the same order of magnitude as recent experimental results (∼900). Our study highlights the potential of twist engineering as a tool for tailoring the thermal transport properties of layered materials.

2022-06-18

Microscopic Mechanisms of Frictional Aging

Frictional aging is observed at a wide range of length- and time-scales, and plays a crucial role in functioning of micro- and nanomachines, as well as in the nucleation and recurrence of earthquakes. Here, we developed an analytical model for description of frictional aging mediated by dynamical formation and rupture of microscopic interfacial contacts. The model accounts for the presence of various types of contacts at the frictional interface and exhibits three different aging regimes: (i) linear aging at short hold times, (ii) logarithmic (or logarithmic-like) aging for intermediate time scales and (iii) levelling off in the static friction for long hold times. It is demonstrated that the linear aging regime is a universal feature of frictional aging for the interfaces including various types of contacts, and the slope of variation of the static friction with the hold time depends on a distribution of energy barriers for contact formation. The conditions for the existence of a pronounced logarithmic aging regime, covering a long-time interval, have been established. Frictional aging has been found to manifest itself not only in slide-hold-slide measurements, but also in sliding experiments exhibiting stick-slip mode of motion, and a relationship has been established between these two regimes of aging. The predicted dependencies of frictional aging on the normal load and temperature are in good agreement with the experimental observations. Our work shows that experimental studies of load and temperature dependencies of aging, carried out over a wide range of time scales, offer promising opportunities for understanding the microscopic mechanisms of frictional aging and revealing the physical meaning of state variables that determine temporal evolution of friction described by phenomenological rate and state laws.

Research Interests

Publications

More
加入我们

Join Us

Our research group regularly recruits master's and doctoral students, as well as postdoctoral fellows. If you are interested, please contact the PI.
w.g.ouyang@whu.edu.cn

More