Research On The Structure Analysis And Microwave Absorption Properties Of Nickel And Cobalt Mineral Materials

Nickel and cobalt are listed as strategic materials for their excellent corrosion resistance,high melting point and strong magnetism.With the discovery and exploitation of large nickel and cobalt deposits in China,China's nickel and cobalt industry has been established and developed vigorously.The research and development of synthetic and natural nickel and cobalt mineral materials is an important way to increase the added value of nickel and cobalt,and also the need of developing strategic emerging industries.Nickel and cobalt mineral materials are widely used in the field of microwave absorption due to their excellent physicochemical properties.Studies have shown that differences in crystal structure can lead to large differences in absorbing properties.Therefore,Ni/derived heterostructures were prepared by hydrothermal method,core-shell Co@CoO microrods were fabricated by solvothermal method,and nickel and cobalt mineral materials fabricated at different temperatures were characterized by XRD,XPS and SEM,etc.And those magnetic and electromagnetic parameters were measured,simultaneously the effects of actual ore on the microwave absorption properties of nickel and cobalt mineral materials were investigated.The details are as follows:?1?In this study,we successfully synthesized porous 2D sponge-like Ni/derivative heterostructures composed of Ni,NiO and Ni?OH?₂ through a controllable hydrogen reduction method.Thanks to higher grain size of Ni/derivative heterostructure prepared at 600oC?Ni-600?under the hydrogen flow,the higher magnetic properties and magnetic loss could be obtained,which is beneficial for the enhancement of microwave absorption properties.For 50wt%Ni-600samples,the minimal reflection loss?RL?is-37.3 dB at 7.1 GHz and the effective bandwidth?RL<-10 dB,90%microwave dissipation?could be tuned in the range of 4.5–18.0 GHz with the thickness of 1.5-4.5 mm.High anttenuation ability containning dielectric loss and magnetic loss,and good impedance match are the responsibilities for the excellent microwave absorption properties.In addition,the porous 2D heterostructure flakes also significantly contribute to microwave absorption.Multiple reflections and scattering caused by porous flakes,interfacial polarizations in the hererostructures,tunable impedance match in porous structure,strong natural resonance induced by 2D flakes and plentiful micro-capacitors in the separate flakes account for the enhanced microwave absorption performances.This study opens up a fresh exploration of designing novel electromagnetic wave absorbing materials.?2?In this work,we fabricated unique fluffy Co/CoO micro-rod composites with various weight ratio between Co and CoO.The microwave absorption properties of Co/CoO micro-rod composites were significantly affected by the Co contents.With increasing Co contents,due to the high conductive loss,the microwave absorption properties was improved,correspondingly.The fluffy Co/CoO micro-rod composite?Co57?prepared at 700oC exhibited outstanding microwave absorption properties.The optimal reflection loss?RL?was-21.7 dB with a thickness of 2.3 mm and the effective absorption bandwidth?RL is lower than-10 dB?can reach more than 6.1 GHz.In addition,the microwave absorption properties of paraffin/Co57 composites with different Co57amounts were also investigated,and the paraffin-based composite containing 40 wt%Co57 reveals the excellent microwave absorption properties.Furthermore,the density functional theory?DFT?calculations were used to evaluate of the electronic structure of different Co/CoO composite to describe the microwave absorption variation.When the Co amount is gradually increased,the electrical conductivity is enhanced,affecting the dielectric properties of the products.Thus,the difference of the microwave absorbing properties of the experimentally obtained sample was explained from the viewpoint of the electronic structure.We paved a new avenue to use the electronic structure of absorbers to forecast the microwave absorption performance.?3?Adding nickel concentrate and cobalt concentrate in Ni?NiO?and Co?CoO?at a ratio of1:4.The microwave absorption properties of nickel?cobalt?concentrate and its combined with nickel and cobalt high purity were studied.The results show that the microwave absorption properties of nickel?cobalt?concentrate are poor.When the grade and purity of nickel?cobalt?concentrate in nickel?cobalt?concentrate and nickel?cobalt?high-purity composite samples increase,the microwave absorption performance is gradually enhanced.It can be judged that the microwave absorption performance of the sample is closely related to the grade of the actual concentrate or the purity of the species,and it is necessary to re-select or purify the actual concentrate.