Preparation And Properties Of Spinel Ferrite Nanocomposites

In today's society,the development of science and technology not only brings convenience to life,but also brings some disadvantages,For example:the harm of electromagnetic waves.However,good electromagnetic absorbing materials can reduce the harm of electromagnetic waves.In recent years,ferrite nanomaterials,especially spinel-type ferrites,have provided a major research direction of electromagnetic absorbing materials because of their unique electromagnetic properties and easy adjustment of their properties.Therefore,this thesis focuses on the preparation of spinel ferrite nanocomposites and the study of electromagnetic properties,using sol-gel method to prepare Li Fe O₂-Zn Fe₂O₄?Co_xNi_1-xFe₂O₄(x=0?0.2?0.4?0.6?0.8?1)?Co Fe₂O₄@Ni Fe₂O₄?Ni Fe₂O₄@Co Fe₂O₄ composite nanomaterials.Li Fe O₂-Zn Fe₂O₄ ferrite materials were prepared by sol-gel method.The ferrite with different crystal structure could be doped,and the microwave absorption performance of Li Fe O₂-Zn Fe₂O₄ was studied.The results show that for the composite with a thickness of 16.7 mm,the minimum reflection loss at 17.7 GHz is 10.4 d B.An interesting feature of the results is that,compared with the reflection curves of single-component Zn Fe₂O₄ reported in other literature,the reflection curves have several strong absorption peaks in the range of 2-18 GHz.In general,the method described in this thesis has a significant effect on the regulation of electromagnetic parameters,and the prepared Li Fe O₂-Zn Fe₂O₄ composite material can be used as a candidate material for the practical application of electromagnetic compatibility and stealth technology.Co_xNi_1-xFe₂O₄(x=0,0.2,0.4,0.6,0.8,1),core-shell composite nanomaterials Ni Fe₂O₄@Co Fe₂O₄ and Co Fe₂O₄@Ni Fe₂O₄ were prepared by sol-gel method.The structure and properties of ferrite materials were analyzed.The results of structural analysis show that the crystal structure of the prepared ferrite composites is spinel type ferrite.The grain size of the material is between 50 nm and 94 nm.SEM analysis shows that the sample has agglomeration phenomenon,and TEM analysis shows that the core-shell composite has good core-shell structure.The microwave absorption properties of the composite were characterized.The results show that:(1)The minimum reflection loss of the composite Ni_0.4Co_0.6Fe₂O₄ is-35.0d B at 16.88GHz under the condition of thickness of 10 mm.It has several strong absorption peaks in the range of 2-18 GHz,and the attenuation constant(?)increases with the frequency.It is a good absorbing material.(2)Ni Fe₂O₄@Co Fe₂O₄(2:3)composite material with a thickness of 6 mm has a minimum reflection loss of-37.6d B at high frequency of 16.48 GHz.The attenuation constant(?)increases with the increase of frequency.It can be seen that Ni Fe₂O₄@Co Fe₂O₄composite material is a good high frequency absorbing material.(3)Minimum reflection loss of the composite at a low frequency of 5.6 GHz of Co Fe₂O₄@Ni Fe₂O₄(4:1)is-24.4 d B and at a thickness of 8 mm.Co Fe₂O₄@Ni Fe₂O₄(3:2)at a thickness of 8 mm,and the minimum reflection loss of the composite at low frequency 7.12 GHz is-30.4 d B.When the thickness is 12mm,the minimum reflection loss of the composite is-32 d B at 14.5 GHz.And the attenuation constant(?)of Co Fe₂O₄@Ni Fe₂O₄ composite increases with the decrease of frequency.It can be seen that the composite is a good low frequency absorbing material.In general,the prepared Co-Ni composites have a significant effect on the adjustment of electromagnetic parameters,have good microwave absorption performance,and have the potential as candidates for practical application of electromagnetic compatibility and stealth technology.A simple preliminary study on the photocatalytic performance of Co-Ni composites shows that all the prepared Co-Ni composites have photocatalytic performance.The core shell nanoparticles Co Fe₂O₄@Ni Fe₂O₄(2:3)degradation performance is best.After the catalysis,the sample was simply recovered,and the recovery rate of the sample reached 98%,showing good environmental performance.