In this paper, the thermal properties of graphene oxide (GO) with vacancy defects were studied using a non-equilibrium molecular dynamics method. The results showed that the thermal conductivity of GO increases with the model length. A linear relationship of the inverse length and inverse thermal conductivity was observed. The thermal conductivity of GO decreased monotonically with an increase in the degree of oxidation. When the degree of oxidation was 10%, the thermal conductivity of GO decreased by ~90% and this was almost independent of chiral direction. The effect of vacancy defect on the thermal conductivity of GO was also considered. The size effect of thermal conductivity gradually decreases with increasing defect concentration. When the vacancy defect ratio was beyond 2%, the thermal conductivity did not show significant change with the degree of oxidation. The effect of vacancy defect on thermal conductivity is greater than that of oxide group concentration. Our results can provide effective guidance for the designed GO microstructures in thermal management and thermoelectric applications.

As a derivative material of graphene, graphene oxide films hold great promise in thermal management devices. Based on the theory of Fourier formula, we deduce the analytical formula of the thermal conductivity of graphene oxide films. The interlaminar thermal property of graphene oxide films is studied using molecular dynamics simulation. The effect of vacancy defect on the thermal conductance of the interface is considered. The interfacial heat transfer efficiency of graphene oxide films strengthens with the increasing ratio of the vacancy defect. Based on the theoretical model and simulation results, we put forward an optimization model of the graphene oxide film. The optimal structure has the minimum overlap length and the maximum thermal conductivity. An estimated optimal overlap length for the GO (graphene-oxide) films with degree of oxidation 10% and density of vacancy defect 2% is 0.33 μm. Our results can provide effective guidance to the rationally designed defective microstructures on engineering thermal transport processes.

The finger seal has an important influence on the performance of the aero-engine, and the effect of complex working states on the performance of the finger seal, which is located in the aero-engine, is also prominent. But so far, the finger seal performance under complex working states, which include the incline of the rotor, assembly condition, temperature effect, and impact effect, has not been investigated yet. Based on this, an equivalent dynamic model of finger seal is presented under complex working states, and the dynamic performance analysis of the finger seal is carried out by the model. The results show that the complex working states have larger influence on the finger seal performance. Meanwhile, an experimental research is carried out and the results are compared with the theoretical results. And then the validity of the equivalent dynamic model of the finger seal under complex working states is proved. The present work is conducive to improve the theoretical research system of finger seal, and promote the dynamic analysis technology to engineering application as well.

A leak element based on graphene oxide (GO) membranes is developed using vacuum filtration and the modified Hummer's method. He, Ne, Ar, and Kr leak rates (LRs) through the element are measured using a quadrupole mass spectrometer. The various gases undergo molecular flow through the leak element at pressures of up to 500 kPa with the nanoporous structures of GO. The LRs of various gases at particular pressures can be predicted given the LR of one gas at a specific pressure. When the membrane is less than 600 nm thick, the main gas-permeation pathways are aligned defects through the GO membrane and the LR decreases exponentially as the membrane thickness increases. By contrast, when the membrane is more than 600 nm thick, the main gas-permeation pathways are spaces between the layers and the LR is inversely proportional to the membrane thickness.