Preparation Of Passion Fruit Like Fe₃O₄@C Nanoparticles And Their Magnetorheological And Anti-impact & Electromagnetic Shielding Properties

Magnetic particles can exhibit unique properties under an external magnetic field,making them play a unique role in magnetorheological fluids,electromagnetic shielding and other fields.However,due to the easy agglomeration of pure magnetic particles in the base fluid,the magnetorheological fluid exhibits poor dispersion stability,which affects its application in the engineering field.Therefore,it is very important to improve the dispersion stability of magnetorheological fluids.In addition,in the military field,with the deepening of the concept of modern warfare,the form of intelligent warfare based on science and technology has emerged,in which intelligent missiles are very easy to fail under electromagnetic interference and strong impact.Therefore,there is an urgent need for protective materials that have both buffer performance and electromagnetic shielding performance to protect equipment operating under similar conditions.The main contents include the following parts:（1）The Fe₃O₄ nanosphere particles were prepared by coprecipitation method and C@Fe₃O₄,Fe₃O₄@C,and Fe₃O₄@DC nanosphere particles were prepared by hydrothermal method,and the morphology,element distribution,crystal structure,specific surface area,density and magnetic properties of the prepared particles were characterized and analyzed,and samples are soft magnetic materials.（2）Select Fe₃O₄and Fe₃O₄@C nanoparticles,silicone oil,and mineral oil to explore the wettability of the particles and the base fluid and analyze the reasons.At the same time,the rheological effect of the two magnetorheological fluids was characterized,and it was confirmed that the passion fruit-like Fe₃O₄@C based magnetorheological fluid has better stability than the pure Fe₃O₄ based magnetorheological fluid.（3）Porous polyvinylidene fluoride-hexafluoropropylene（PVDF-HFP）thin films were prepared,and on this basis,lithium bistrifluoromethanesulfonimide（Li TFSI）or carbon nanotubes（CNT）or both of them were used as conductive fillers,and three kinds of conductive composite films were prepared.At the same time,the magnetic conductive films were prepared with Fe3O4@C as the magnetic conductive fillers,and the sample films were characterized and analyzed,the electrical properties of the films doped with Li TFSI and CNT are the best,and the films have good flexibility.（4）Because the layered structure has adjustable mechanical properties and can provide more interfaces,the conductive film and the magnetic conductive film are made into a layered structure,which improving the mechanical properties and electromagnetic shielding performance of the material,its total shielding value reaches a maximum of33 d B,which meets general commercial needs;at the same time,under continuous impact,the sample has 24.92%and 20.21%buffer coefficients,which are better than commercial rubber and foamed copper,the sample has both shock-resistant cushioning performance and electromagnetic shielding performance.