Synthesis And Electromagnetic Properties Of Mono-disperse Iron Microflakes/molybdenum Disulfide Composite Materials

Generally, the electromagnetic shielding performance of metal magnetic powder with a nearly spherical morphology decreases due to the drastic reduction of saturation magnetization and permeability in high frequency caused by the limiting of Snoek’s limit law. Nevertheless, the downward trends of permeability decrease effectively through the transformation of the morphology of magnetic powder from spherical to flake. In this study, we prepared mono-disperse Fe microflakes/Mo S2 composites with high electromagnetic shielding performance via two-step hydrothermal methods and hydrogen heating reduction method. The research contents are as follows:1. The synthetic conditions of mono-disperse Fe microflakes prepared by hydrothermal and hydrogen heating reduction methods have been discussed. Firstly, the micron sized mono-disperse Fe2O3 microflakes were synthesized by hydrothermal method. Meanwhile, we investigate the effects of Ba(NO3)2 and PEG-400 concentration on the morphology and structure of mono-disperse Fe2O3 microflakes. Then the mono-disperse Fe microflakes were obtained from Fe2O3 through hydrogen heating reduction method. The effects of different reduction temperatures on the structure, morphology and electromagnetic parameter of Fe microflakes were studied. The results show that surface defects such as holes and collapse emerge with the increasing of reduction temperatures. In addition, the minimum reflection loss of mono-disperse Fe microflakes can reaches-30 d B. In the frequency range of 8.2-12.1 GHz, the absorbing area was deeper than-10 d B(means that 90% of the attenuation according to equations that mentioned above) with the thickness of 2 mm.2. Mono-disperse Fe2O3/Mo S2 composites were primarily prepared through introduction of Mo S2 to combine with mono-disperse Fe2O3 microflakes in hydrothermal method. Afterwards, the composites were dealt with hydrogen heating reduction to obtain mono-disperse porous Fe microflakes/Mo S2 composites. We discussed the effects of surfactants(PEG-400 and SDBS) on the structure and electromagnetic property of flake porous Fe microflakes/Mo S2 composites, respectively. The results show that SDBS-assisted porous flake Fe microflakes/Mo S2 composites possess more uniform morphology and better electromagnetic performance. Structure characterization results show that Mo S2 nanosheets grow on the surface of mono-disperse porous flake Fe microflakes uniformly. The results of electromagnetic parameter tests show that, composite materials possess better electromagnetic performance than mono-disperse porous Fe microflakes. The absorbing area was deeper than-10 d B in the frequency range of 9.0-13.1 GHz. The minimum reflectivity can reaches-34 d B with matching thickness of 2.5 mm.3. Mono-disperse Fe microflakes/Mo S2 composites with excellent structure retention w ere obtained through hydrogen heating reduction at low temperature. As-synthesized composites treated by low temperature hydrogen heating reduction possess great structure retention. Mo S2 sheets grow on the mono-disperse Fe microflakes uniformly. With the increasing addition of Na2 Mo O4, Mo S2 sheets turn to floccules and mono-disperse Fe microflakes agglomerate with Mo S2 floccules. Meanwhile, compared to pure mono-disperse Fe microflakes, the introduction of Mo S2 could efficient improve its electromagnetic performance. For mono-disperse Fe microflakes/Mo S2 composites with the optimum addition of 0.2 g Na2 Mo O4, the effective absorption bandwidth could cover 11.2~16 GHz with the thickness of 2 mm. The minimum reflection loss can reaches-37 d B.In this work, we first time prepared mono-disperse Fe microflakes/Mo S2 composites with excellent electromagnetic performance by growth of Mo S2 on the surface of mono-disperse Fe microflakes. Therefore, as-prepared composites provide a reference for the light weight and high-efficient electromagnetic shielding materials.