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.

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.

Graphene containing intrinsic pores with molecular dimensions is a highly promising material for standard leak elements because of its minimal and stable gas flow. However, the etching of polymethyl methacrylate (PMMA) during the typical graphene transfer process can cause the rupture of graphene on the porous substrate due to the surface tension as the etchant solution dries out. In this article, we simplified the typical graphene transfer process that enabled the transfer of a PMMA/graphene composite membrane onto a macroporous Cu gasket as the leak element and tested the leak rate, time stability, and response time of the composite membrane. The membrane permeation area depends on the pore size of the Cu substrate, which can be controlled by laser ablation or computer numerical control milling. To ensure the accuracy of time stability, the entire test lasted 60 days. The conductance results for two devices with a permeation size of 50 and 500 μm were about 10−17 and 10−14 m3 s−1, and the maximum variation of conductance in 60 days was 14% and 2.6%, respectively. Accordingly, the permeance of the composite membrane for helium can be calculated as 4.17 × 10−12–1.09 × 10−11 Pa m3 (cm2 s Pa)−1. Moreover, the composite membrane has been proven to have a rapid response of about 2 s to the upstream pressure.

The special test technology of the assembly, integration and test (AIT) of large satellites was studied, which accurately determine the leakage, alignment and mass property of large satellites, and ensure the reliable operation of large satellites in orbit. The local and total leakage testing technique was developed which based on quadrupole mass spectrometer and helium mass spectrometer. To meet large satellite quality and high precision, the satellite mass property testing equipment of large load bearing based on three coordinate conversion machine has been set up. A laser tracker uniting theodolite measure system with high positional precision and high angle measurement accuracy has been developed. Several large satellites have been tested in the process of AIT with these testing equipment. The quality of the large satellite has been effectively guaranteed.