Preparation And Microwave Absorption Performance Of Nickel Zinc Ferrite And Its Composites

As a kind of soft magnetic material, nickel zinc ferrite(NixZn1-xFe2O4) has been widely used in the field of microwave absorption, owing to its excellent properties sunch as high permeability, resonant frequency and excellent dielectric loss properties. We can meet actual demand by adjusting nickel zinc ratio and technological parameters, because the mole ratio of nickel and zinc in NixZn1-xFe2O4 and the parameters(such as the kinds of surfactants, calcination temperature, p H value, dosage of surface active agent, etc.) in the preparation process all have a great influence on the morphology and electromagnetic properties of the samples. As a kind of wave-absorbing material, single ferrite shows poor stability in high temperature and density. In order to improve them and extend the scope of ferrite’s application in the field of light absorbing, this paper prepared NixZn1-xFe2O4 composites with conductive polymer polyaniline PANI and multi-walled carbon nanotubes MWCNTS, respectively, employing modern analysis methods(such as XRD, SEM, FT-IR, VSM and vector network analyzer, etc.) to further exploring the change role of nickel zinc ferrite composites’ morphology and its magnetic properties. The main contents of the research are as follows:1、Studied the change of morphology and the performance of ferrite NixZn1-xFe2O4 sample using co-precipitation method with different proportion of nickel and zinc. The ratio of nickel and zinc in NixZn1-xFe2O4 sample have a great influence on the magnetic property of the sample, when x=0 the as-prepared sample showed weak magnetism; then with the increase of x, namely the increase of nickel content in the NixZn1-xFe2O4, the saturation magnetization also increase gradually, and when x=0.6, NixZn1-xFe2O4 reached the highest saturation magnetization Ms=64.9 emu/g; but the x value continued increasing, the saturation magnetization of the sample had slightly reduces.2、The experimental conditions(such as surfactant kinds/dosage, temperature, p H, etc.) systematically studied for the preparation of Ni0.6Zn0.4Fe2O4 and its influence on sample’s morphology and performance. Results showed that the as-prepared sample with adding surfactant cetyltrimethyl ammonium bromide(CTAB) not only dispersed uniformity particles but also showed the best performance in the wave absorption under different coating thickness. And the peak maximum-20.37 d B of reflection loss at 6.04 GHz were abtained under the coating thickness 5 mm; Under the calcination temperature condition of 1100℃, the as-prepared sample showed uniformly particle size, complete crystal shape and outstanding absorbing performance. Furthermore, the maximum reflection loss reached to-10 d B with coating thickness only 2 mm, and when the thickness were 4 mm and 5 mm, the biggest reflection loss can reach to-19.08 d B and-39.33 d B, respectively. The conditions of different p H and the amount of surfactant had little effect on the the morphology of samples, but some differences existed in the wave absorption performance. When p H=11.51, the maximum reflection loss value of as-prepared sample’s reached-46.76 d B under the coating thickness for 5 mm; And with the proportion of n(Ni0.6Zn0.4Fe2O4):n(CTAB)=2:1 in preparation of the sample, when the layer thickness was 5 mm, the sample gained maximum reflection loss-54.60 d B, and the effective width was 5.56 GHz(3.2 GHz to 3.2 GHz).3、Study composites of different proportion of PANI/Ni0.6Zn0.4Fe2O4 by in situ polymerization method, the test method of XRD, FT-IR, TGA and SEM have been proved the existence of various components in the composite and the change of the morphology. The changes of as-obtained composite happenedin wave absorption performance by calculating the vector network analyzer tested data. It can be seen that with the different proportion in composites, its performance happened great changes, composite sample with ratio of n(Ani):n(Ni0.6Zn0.4Fe2O4)=1:2 showed better absorbing performance in whole. When coating thickness was 2.6 mm, samples obtained the biggest reflection loss at 12.79 GHz with maximum 40.20 d B, and the effective width reached to 4.98 GHz(10.57 GHz to 10.57 GHz).4、Study composites MWCNTS/Ni0.6Zn0.4Fe2O4 with different content of MWCNTS by situ hydrothermal method. With the increase content of MWCNTS in the composite, some changes of the composite materials’ morphology as well as the performance had been taken place. Ni0.6Zn0.4Fe2O4 nanoparticles distributed evenly with 20-30 nm as globular grains by hydrothermal synthesis. And clearly seeing that carbon nanotube surface loaded with the nano Ni0.6Zn0.4Fe2O4 particles decreased with increasing amount of carbon nanotubes in the composites, which was consistent with design of experimental results. Because of the nanometer material Ni0.6Zn0.4Fe2O4 showed reunion phenomenon in composite materials that led the uneven distribution of magnetic nanoparticles on the carbon nanotube surface and part of them were gathering together. The absorbing performance of the composite also showed different with the changing content of MWCNTS in composite materials. The composite with adding 50 mg MWCNTS reached a maximum-38.00 d B at 15.04 GHz with the coating thickness of only 1.5 mm; and when adding 100 mg MWCNTS, the samples reached the maximum reflection loss to-14.92 d B at 14.92 GHz with coating thickness of 1.4 mm and its effective frequency band width was 4.08 GHz(13.36 GHz to 13.36 GHz). Adding appropriate amount of MWCNTS, composite samples will show excellent absorbing performance. So we can adjust the adding ratio of the components in the sample according to the actual need of specific production.