Preparation Of Hexagonal Boron Nitride(h-BN)composites And Research On Their Properties

With the development of industrial technology,people are constantly looking for materials with various excellent properties.Hexagonal boron nitride(h-BN)has received more attention in recent years due to its special structure and excellent performance.Some pure h-BN is directly used as raw materials to prepare optical or electronic devices,and more are modified to prepare composite materials to improve the properties of materials,such as thermal conductivity.Thermally conductive polymer composite materials are widely used in the electronic packaging industry due to their good processability,but the thermal conductivity of the polymer is very low,so people increase the thermal conductivity by adding different fillers.h-BN has very excellent thermal conductivity,and the few-layer Boron nitride nanosheets(BNNS)obtained after peeling can maximize the utilization efficiency of the materials.Here in,h-BN was exfoliated by high pressure homogenization method.The BNNS obtained by high pressure homogenization method were complete and had active sites that could continue the reaction.PVP is used as stabilizer and dispersant.h-BN aqueous solution is uniformly dispersed after being homogenized at high pressure.After centrifugation at high speed,few layers BNNS could be obtained at the supernatant.The obtained BNNS was immediately reduced by Fe Cl₃·6H₂O to get BNNS@Fe₃O₄,the synthesized product was characterized to verify the structure and morphology of it.The method of preparing BNNS@Fe₃O₄ can also be used to prepare other Fe₃O₄ modified two-dimensional materials.Vertically oriented high thermal conductivity PI/BNNS@Fe₃O₄ composite material been prepared since the BNNS been modified by Fe₃O₄ can be oriented under the action of external magnetic field.The 25wt%filler loaded PI/BNNS@Fe₃O₄(25wt%)exhibited a through-plane thermal conductivity of 4.07W/(m·K),which is 9.04 times that of the pure PI.We also uses in-situ construction of PS microspheres and h-BN to obtain a 3D thermal network with a certain degree of orientation besides constructing a polymer-filler 3D thermal network through a magnetic field.The gap between PS microspheres and h-BN is filled with nylon 6 micropowder,which have the effect of toughening and connection.After mixing evenly,the alloy-like plastic with good mechanical properties is formed by hot-pressing.Meanwhile,the 3D structure of the composites were obtained.The 40wt%BN filler loaded exhibited a through-plane thermal conductivity of 3.28W/(m·K).All the thermal conductivity in this paper refers to the through-plane thermal conductivity(the normal direction of the atomic plane).Finally,the adsorption performance of BNNS@Fe₃O₄ on Congo red dyes was studied because BNNS has a large specific surface area.BNNS@Fe₃O₄composite can be used as an excellent adsorbent,and the adsorption performance does not decrease significantly after four cycles of use,and the adsorbent is easy to be recovered.