Study On Orientation Control Of Graphite NaNo-platelet Under Magnetic Field And Gas Barrier Properties Of Composites

No-liner Design could effectively improve the structure efficiency of compositepressure vessel and reduce its weight, but it will cause the decrease of its gasimpermeability. This gas leakage seriously limited the research and development ofno-liner composite pressure vessel. Based on the shell’s structure, The paper hasprepared ordered composite, which has the similar structure of shell, throughmagnetic field inducing alignment of the magnetically modified graphitenano-platelet, and revealed its gas barrier mechanism, so as to provide technicalsupport for the development of the no-liner composite pressure vessel.First, The paper prepared graphite nano-platelet through the Modified HummerMethod, using natural flake graphite as raw material. By using SEM, Fouriertransform infrared spectroscopy （FTIR） and XRD tracing the process of thepreparation, we find the graphite nano-platelet we prepared has the thickness of30-80nm, diameter of0.5-20μm and an aspect ratio of100-500. More importantly,the graphite nano-plateltet still maintained the layered structure of graphite andthere were no oxygen containing groups existing on its surface. In order to realizethe magnetic modification of the graphite nano-plateltet, we prepared the Fe3O4nanoparticles on the surface of the graphite nano-platelet by using the chemicalco-precipitation method. By analyzing product by means of SEM, Fourier transforminfrared spectroscopy （FTIR） and XRD, we find that under the condition ofcrystallization temperature30℃, n(Fe²⁺/Fe³⁺)=1:2, ammonia concentration0.76%,speed1000rpm and N₂protection, the prepared Fe3O4nanoparticles deposited on thesurface of graphite nano-platelet was single phase-Fe₃O₄nanoparticles and itsdiameter was approximately30nm. The VSM analysis result of the product showsthat magnetically modified graphite nano-platelet has good magneticresponsiveness.Second，after the force and motion analysis of the representative element ofmagnetic flake particles in magnetic field, and substituting relevant parameters ofmagnetically modified graphite nano-platelet, we use Boltzmann statistics tocalculate the theoretical magnetic field H required by the alignment of magneticallymodified graphite nano-platelet. The graphite nano-platelet was dispersed in theepoxy resin matrix by using the method of solution mixing, the mixed system wasplaced in a static magnetic field and rotated to prepared ordered graphitenano-platelte reinforced epoxy resin composite. The SEM and XRD analysis results showed that the graphite nano-platelets were arranged parallel to the horizontaldirection in the resin matrix.At last， several disordered graphite nano-plateltes reinforced epoxy resincomposites with different graphite nano-platelet contents were tested with regard tohelium leak rate. The results showed that with the increase of the content of graphitenano-platelets, helium leak rate was gradually decreased. But the decrease of heliumleak rate caused by unit graphite nano-plateltes content reduced gradually.Orderedgraphite nano-plateltes reinforced epoxy resin composites were tested with regard tohelium leak rate. The results showed that the arrangement of the graphitenano-plateltes along the he direction perpendicular to the gas diffusion direction caneffectively decrease the helium leak rate of nanocomposites.