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Preparation And Electromagnetic Characteristics Of Co-based Magnetic Microwave Absorption Material

Posted on:2017-02-26Degree:MasterType:Thesis
Country:ChinaCandidate:H X GuFull Text:PDF
GTID:2271330491450308Subject:Electronic and communication engineering
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Co-based magnetic material has very important significance in the absorbing material fields because of high Curie temperature, high saturation magnetization and low anisotropy. In this thesis, Co-based magnetic materials with platy structure were fabricated. The platy Co-based magnetic materials can restrain skin effect effectively, break the limit of Snoek and has high permeability. So they have good absorbing properties.Co-based magnetic materials were prepared by three different methods. The phase structure, morphology, electromagnetic parameters were analyzed by X-ray diffraction(XRD), scanning electron microscope(SEM) and vector network analyzer. According to the simulation calculation of transmission line theory, the absorbing properties were calculated by electromagnetic parameters. The main researches as follows:(1) Via electroless plating first and ball-milling later, the carbonyl iron/Co composite materials with different loadage of carbonyl iron had been prepared. The effect of loadage of carbonyl iron on the absorbing properties at the frequency of 1-18 GHz had been studied. Results showed that the morphology of untreated carbonyl iron is globular and the morphology of treated carbonyl iron is platy. α-Fe appeared in the samples. The electromagnetic parameters changed as the loadage of carbonyl iron varied. The characteristic impedance match and microwave absorption performances could be tuned by changing the loadage of carbonyl iron. With the increasing of the loadage of carbonyl iron, the minimum reflection loss(RL) value of samples decreased, and the matching frequencies were around 4GHz. As the loadage was 20g/L,the sample showed the best absorption performance. The minimum reflection loss value was-8.5d B at 4GHz with a matching thickness of 1mm. And the absorption band(RL<-5d B) was 4.46 GHz.(2) Via ball-milling first and electroless plating later, the carbonyl iron/Co composite materials with different loadage of carbonyl iron had been prepared. The influence of loadage of carbonyl iron on the absorbing properties also had been studied. Results showed that the sample also had the platy morphology. And α-Fe also appeared in the composite materials. The complex permittivity and permeability changed as the loadage varied. The absorbing properties also can be tuned. With the increasing of loadage of carbonyl iron, the minimum reflection loss value decreased slightly. The matching frequency moved to higher frequency. The frequency width of less than-5d B became wider. With a matching thickness of 1mm, as the loadage was 10g/L, the minimum reflection loss value of-8d B was obtained at 2.5GHz, and the absorption band(RL<-5d B) was 3.23GHz; as the loadage was 15g/L, the minimum reflection loss value of-8.5d B was obtained at 4.5GHz, and the absorption band(RL<-5d B) was 5.4GHz; as the loadage was 20g/L, the minimum reflection loss value of-8.5d B was obtained at 6GHz, and the absorption band(RL<-5d B) was 6.8 GHz.(3) Mixing carbonyl iron and Co and ball milling the mixed materials for 30 hours, carbonyl iron-Co alloy materials were prepared by mechanical alloying. The effect of Co content on the absorbing properties had been studied. Results showed that the samples had the platy morphology and the size was in several micrometer range.(Fe, Co) solid solution appeared in the samples. And with the increasing of Co content, the intensity of the diffraction peak decreased. Firstly, with the increasing of Co content, the minimum reflection loss value decreased, and the matching frequency moved to higher frequency. The absorption band(RL<-10 d B) became wider. When Co content was increased to 7%, as the Co content increased, the minimum reflection loss value increased, and the matching frequency moved to lower frequency. The absorption band(RL<-10 d B) became more narrow. As Co content was 9%, the minimum reflection loss value was-20.05 d B at 1.81 GHz with a matching thickness of 2.5mm. And the absorption band(RL<10d B) was 0.89 GHz.
Keywords/Search Tags:carbonyl iron, Co, electroless plating, mechanical alloying, absorbing properties
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