Preparation And Microwave Absorption Properties Of Ni（CoZnCu）Fe₂O₄/SiO₂@SiC/CNTs Composites

Problem of making aircrafts and new weapons less detectable and microwave less leaked in military affair and civil area affect the development of a country’s national power and national health. But currently, the absorbing streng of some used single absorbing material are is not enough as absorbing coatings, and the band width is also not enough too, so looking for microwave absorbing material of being extensive sources, low price, has high intensity of microwave absorption and wide band width is extremely urgent. papers have shown that microwave absorbing performance of the spinel ferrite is good, it is a commonly used absorbing material as its easy synthesis; CNTs and SiC are good microwave absorbing material.Magnetic loss of the spinel ferrite Ni（Co ZnCu）Fe₂O₄, dielectric loss of the shell-core SiO₂@SiC and carbon nanotubes, the structural characteristic of SiO₂@SiC, as well as the physical and chemical properties of materials itself are considered and used in this paper. sol-gel method was adopted to make SiO₂ coating on the surface of SiC and composite powders were prepared with spinel ferrite and CNTs. Phase structure and morphology of the materials were characterized by XRD, SEM, TEM, XPS and polarizing microscope, and absorbing properties of them were tested by using vector network analyzer, in the end, the pH, ratio of components, synthetic rule and ferrite types have a huge effect on their absorbing properties. The main results were as follows:First of all, a series of composite powders SiO₂@SiC present a structural features of Si O₂ coated SiC type and when V（ethanol/water）=2:1, pH=8.44, m（SiC/SiO₂）=7:3, the absorbing properties of the composite powders are the optimal: the composite materials have the strongest absorption peak when the frequency is 8.24 GHz, intensity value is-27.28 dB, the frequency of the sample is from 3.76 GHz to 15.04 GHz with a bandwidth of 12.28 GHz（R<-10 dB）.Secondly, a series of shell-core SiO₂@SiC/Ni（CoZnCu）Fe₂O₄ compound powders have the optimal absorbing properties when m（NiFe₂O₄/SiO₂@SiC）=50%, synthesis rule is 800℃/2h, and the ferrite type is NiFe₂O₄: the composite powders have the strongest absorption peak when the frequency is 6.01 GHz, intensity value is-32.61 dB, the frequency of the sample is from 5.28 GHz to 7.2 GHz with a bandwidth of 2.08 GHz（R<-10 dB）.Finally, a series of Ni（CoZnCu）Fe₂O₄/shell-core SiO₂@SiC/CNTs composite powders have the optimal absorbing properties when the sample was made concluding 50% wt. SiO₂@SiC and 7% wt. CNTs, the composite powders have the strongest absorption peak when the frequency is 13.85 GHz, intensity value if-15.93 d B, the frequency of the sample is from 3.68 GHz to 4.24 GHz and from 13.52 GHz to 14.08 GHz with a bandwidth of 0.56 GHz（R<-10 dB）; at low frequency, ZnFe₂O₄ ferrite type composite powders have the optimal absorbing performance, at high frequency, NiFe₂O₄ ferrite type composite powders have the optimal absorbing performance.