The Preparation And Properity Study Of Magnetic Nanoparticles Wrapped In Carbon Nanohorns Microspheres Microwave Absorbers

With the rapid development of wireless communication technology and intelligent electronic devices,increasing amounts of electromagnetic radiation and interference are being generated,which seriously pollute the environment and affect human health or operation of equipment.Designing unique structures and morphologies of magnetic metal/carbon by using the multiple loss mechanism is a feasible direction to further enhance the EMW absorption performance.At the same time,using economic and environmentally friendly preparation process to obtain excellent performance of electromagnetic wave absorbing materials is of great importance in practical applications.N-doped carbon nanohorns are characterized by high porosity,high specific surface area.The defects of CNHs can produce dielectric losses.Thus,CNHs are promising EMW-absorbing candidates.Herein,three carbon nanohorn-based/magnetic nanoparticle composites with different morphological systems were prepared by changing the types metal during the arc discharge.Magnetic nanoparticles with different wrapping content can be obtained by changing the number of metal wires.The microwave absorption performance of the three morphological composites and wrapping content is different.In addition,the mechanism of electromagnetic wave absorption is further illuminated.The details of the study are as follow:Herein,Fe nanoparticles wrapped in carbon nanohorn microspheres enriched with N（Fe@NCNHs）were produced by arc discharge method.The total pore volume for CNHs was calculated to be 0.38 cm³·g^-1,corresponding to its naturally inherited micropore and mesopore-dominate porosity.In addition,the N-doping content reached up to 9.3 at.%.When Fe nanoparticles with uniform size are well wrapped in CNHs,exhibiting excellent electromagnetic wave absorption property with a minimum reflection loss(RL_min)of-44.52 d B at 10.86 GHz matching an extremely low thickness of 1.6 mm.Fe@NCNHs are promising microwave-absorbing materials,which is attributed to the multiple reflections induced by the hollow structure of CNHs,interfacial polarization between the CNHs and Fe nanoparticles,dipole polarization induced by N-doping,and pentagonal and heptagon defects on CNHs.The RL_min of Fe@NCNHs is located in X-band.Changing other metals to explore the absorbing performance.By using the arc discharge method,1-4 Co wires sequentially inserted inside the anode carbon rods.Co@carbon nanohorns and Co@graphene microspheres（Co@CNHs/G）with N enrichment were synthesized.As a result,Co@CNHs/G exhibited excellent electromagnetic wave absorption performance at C-band.The RL_min values is-44.72 d B with the thicknesses of 2.9 mm.Additionally,the maximum effective absorption bandwidthwas 5.7 GHz（12.3-18 GHz）at 1.4 mm.More importantly,the distribution of metal nanoparticles into CNHs and graphene microspheres were adjusted by forming the Co Fe alloy embedded into CNHs and graphene microspheres during arc discharge process.Consequently,the frequency of RL_min was in X band.The corresponding thickness for the RL_min was 1.8 mm.The microwave absorption property is tunable by changing different types of magnetic metal nanoparticles and their distribution in the carbon matrix.The metal particles were wrapped in CNHs or carbon microsphere when metal wires inside the anode such as Fe,Co,Ni.In addition the microwave absorption performance in the low frequency need to be improved.Mo₃C₂ encapsulated by CNHs and carbon microspheres（Mo₃C₂@NC）is synthesized by using Mo wires.So the EMW performance of the products after the arc discharge of 1-5 Mo wires inserted into the anode carbon rods were investigated.The microstructure of 1-and 2-Mo₃C₂@NC is lemon-like.The microstructure of 3-,4-and 5-Mo₃C₂@NC is fig-like.The excellent performance of 1-,2-,3-,4-,5-Mo₃C₂@NC exhibited in S-,C-,X-,Ku-band.1-Mo₃C₂@NC exhibited excellent microwave absorption in the low frequency.For1-Mo₃C₂@NC,the RL_min value reached 45.60 d B at 3.97 GHz（S-band）.For4-Mo₃C₂@NC,the MEAB is 6.3 GHz（11.7-18 GHz）at the thin thickness of 1.5 mm,covering all of the Ku band.