Qin Lou’s research while affiliated with University of Shanghai for Science and Technology and other places

Efficiently capturing the three-dimensional spatiotemporal distributions of temperature is of great significance for alleviating hotspot issues in 3D FinFETs. However, most previous thermal simulations mainly focused on the steady-state problem with continuous heating. Few studies are conducted for the transient thermal conduction in 3D FinFETs with non-continuous heating, which is actually closer to the reality. To investigate the effects of heating strategies on the transient micro/nano scale thermal conduction in 3D FinFETs, three heating strategies are considered, including `Continuous', `Intermittent' and `Alternating' heating. A comparison is made between the phonon BTE solutions and the data predicted by the macroscopic diffusion equation, where the effect of boundary scattering on phonon transport is added into the effective thermal conductivity. Numerical results show that it is not easy to accurately capture the heat conduction in 3D FinFETs by the macroscopic diffusion equation, especially near the hotspot areas where ballistic phonon transport dominates and the temperature diffusion is no longer valid. Different heating strategies have great influence on the peak temperature rise and transient thermal dissipation process. Compared to `Intermittent' or `Continuous' heating, the temperature variance of `Alternating' heating is smaller.

A synthetic iterative scheme is developed for thermal applications in hotspot systems with large temperature variance. Different from previous work with linearized equilibrium state and small temperature difference assumption, the phonon equilibrium distribution shows a nonlinear relationship with temperature and mean free path changes with the spatial temperature when the temperature difference of system is large, so that the same phonon mode may suffer different transport processes in different geometric regions. In order to efficiently capture nonlinear and multiscale thermal behaviors, the Newton method is used and a macroscopic iteration is introduced for preprocessing based on the iterative solutions of the stationary phonon BTE. Macroscopic and mesoscopic physical evolution processes are connected by the heat flux, which is no longer calculated by classical Fourier's law but obtained by taking the moment of phonon distribution function. These two processes exchange information from different scales, such that the present scheme could efficiently deal with heat conduction problems from ballistic to diffusive regime. Numerical tests show that the present scheme could efficiently capture the multiscale heat conduction in hotspot systems with large temperature variances. In addition, a comparison is made between the solutions of the present scheme and effective Fourier's law by several heat dissipations problems under different sizes or selective phonon excitation. Numerical results show that compared to the classical Fourier's law, the results of the effective Fourier's law could be closer to the BTE solutions by adjusting effective coefficients. However, it is still difficult to capture some local nonlinear phenomena in complex geometries.

KIT-6 silica with well-ordered three–dimensional (3D) mesopores has been synthesized as a support for nickel-based catalysts. Transmission Electron Microscopy (TEM) and low-angle X-ray Diffraction (XRD) analysis are used to ensure that the ordered 3D mesostructure is stable after NiO incorporation. In this study, the catalytic activities of the NiO/KIT-6 samples are investigated. Additionally, the results show that a 10 wt% NiO/KIT-6 catalyst exhibits high catalytic performance in methane combustion, with T10, T50 and T90 being only 386 °C, 456 °C and 507 °C, respectively. Hydrogen Temperature Programmed Reduction (H2-TPR) studies have shown that the interaction between NiO and KIT-6 in the 10 wt% NiO/KIT-6 catalyst is weak. Methane Temperature programmed Surface Reaction (CH4-TPSR) results show that the surface oxygen of the NiO/KIT-6 catalyst allows it to exhibit a high catalytic performance. NiO/KIT-6 catalysts exhibit superior activities to SBA-15, MCF and SiO2 support catalysts because KIT-6 has a higher surface area and ordered 3D mesopore connectivity, which is favorable for better NiO dispersion and peculiar diffusion for reactant and products. Furthermore, the used catalyst maintained an ordered mesostructure and reduction property.

Rising bubble systems in porous media exist in a variety of industrial processes. However, the flow characteristics of the issue are not well understood. In this work, the rising of bubble/bubbles through two types of porous structures, namely, in-line structured pore and staggered structured pore, are studied using a large density ratio lattice Boltzmann model. The effects of Eötvös number, pore shape, viscosity ratio, initial bubble number, and arrangement manner of the initial bubbles on the bubble deformation, bubble rising velocity, residual bubble mass, bubble perimeter, and the number of bubble breakups are investigated. It is found that as the Eötvös number increases, the bubbles are more easily broken during the process of passing through the porous media, the shapes of the sub-bubbles deviate from the original ones more and more, the bubble perimeter increases, and the difference between the bubble dynamics obtained by the in-line and staggered porous media decreases. Compared to the results of circular and rectangular pores, the bubble rising through the diamondoid pore has a more considerable deformation, which causes a slower rising speed. Furthermore, in the case that two bubbles are originally placed under the porous medium, the bubble deformation is greater and the bubble fracture times increase if the initial bubbles are aligned vertically. The findings of this work can contribute to the understanding of gas–liquid two-phase flow in porous media.