Synthesis Of Sheet-like Molybdenum Disulfide-based Composites And Their Microwave Absorption Properties

With the increasing use of electronic devices and equipment in our life,the problem of electromagnetic wave pollution cannot be ignored.Microwave absorbing materials are one kind of material which dissipates incident electromagnetic wave and converts electromagnetic wave into other forms of energy.This mechanism greatly attenuates reflected wave energy and reduces electromagnetic pollution.We think that microwave absorbing materials need to have the advantages of lightweight,low thickness,high physicochemical stability,broad absorption bandwidths and strong absorption.Graphene and MoS₂ are two-dimensional layered materials with good chemical stability and high specific surface area.Their unique properties offer a lot of promise for dielectric microwave absorbing materials.When graphene or MoS₂ are singly used as an absorbing material,they easily stack and have a single loss mechanism leading to poor performance.However,the synergistic effect can be improved by combing layered two-dimensional materials with other substances.At present,the research on MoS₂ as a microwave absorbing material is still in its initial stage.In this paper,sheet-like materials were prepared by combining with other substances,and their microwave absorption properties were studied.The main research contents are as follows:1.Firstly,we employed a simple two step hydrothermal method to prepare core and shell-interchangeable Fe₃O₄@MoS₂ and MoS₂@Fe₃O₄ nanocomposites.By controlling the hydrothermal temperature,different MoS₂morphologies and contents of Fe₃O₄@MoS₂ NCs were produced,which displayed the optimal RL values(?-50 d B),AB_-10 values(?5 GHz)and high chemical stabilities.With the synthesis temperature increasing from 170 to 200?,their outstanding microwave absorption capabilities moved towards the high frequency region and thin matching thickness.Impressively,the Fe₃O₄@MoS₂ obtained at 200?presented a minimum RL value of-50.75 d B with the thickness of 2.90 mm and an absorption bandwidth of 5.0 GHz corresponding to a thickness of 1.71 mm.Additionally,the excellent microwave absorption capabilities(RL values<-30 d B)with the low matching thickness(<2 mm)could be observed in the frequency range of X and Ku bands.When compared to the reverse structure MoS₂@Fe₃O₄,the core@shell structure Fe₃O₄@MoS₂ exhibited evidently superior microwave absorption comprehensive properties in terms of low optimal RL value,broad absorption bandwidth and high chemical stability,which could be ascribed to the improved impedance matching and microwave attenuation characteristics.2.We proposed a simple water-assisted chemical vapor deposition process to synthesize carbon nanotubes(CNTs)/Ni and chain-like carbon nanospheres(CCNSs)/Ni nanocomposites in high yield by controlling the decomposition temperature.The ultrahigh yield of CCNSs could be achieved when C₂H₂ was catalytically decomposed at 515?,which was up to ca.211.0.The results suggested that microwave absorption properties of the as-prepared samples were highly dependent on their microstructures and composition parameters,which could be regulated by the introduction of water vapor and decomposition temperature.It was worth mentioning that the obtained CCNSs/Ni nanocomposites could simultaneously present an optimal reflection loss of-28.32 d B with a matching thickness of 1.68 mm,and an effective frequency bandwidth of 4.60 GHz with the matching thickness of 1.71 mm.Our results provided an effective and facile strategy to produce CCNSs/Ni in high yield,which provided a new idea for the designing and synthesis of lightweight and excellent microwave absorbing materials.3.A simple CVD and hydrothermal method was proposed to prepare lightweight GOF and RGOF/MoS₂ nanosheets with three-dimensional skeleton structure.The values of minimum reflection loss and effective frequency bandwidth for the as-prepared RGOF/MoS₂ sample could reach up to-62.92 d B at 11.84 GHz with the matching thickness of 2.27 mm and 4.48 GHz with the matching thickness of 2.12 mm.Further research shows that the electromagnetic parameters of RGOF/MoS₂ composites have wider adjustment space and are expected to become microwave absorbing materials with excellent performance.