Preparation And Microwave Absorption Properties Of Ni And Co Sulfide Nanomaterials

In recent years,the widespread use of electronic devices and the rapid development of electromagnetic wave-related technology have brought about unparalleled convenience to human life.However,these advancements have also led to a series of electromagnetic pollution problems that pose a threat to both electronic devices and human health.Thus,it is imperative to find a new material that can effectively combat electromagnetic pollution.Microwave absorbing materials have emerged as a promising solution as they can effectively absorb radiated electromagnetic waves from electronic devices.Consequently,the development of microwave absorbing materials with superior absorption performance has become a focal point of research in the field of materials.In general,wave-absorbing materials aim to possess the characteristics of being lightweight,easily prepared,non-polluting,having a wide effective bandwidth,and strong reflection loss capabilities.However,traditional microwave absorbing materials often fail to meet all of these performance requirements.As a result,enhancing the electromagnetic wave loss ability of absorbing materials has become a hot research topic within the field of wave absorption.Previous research has focused on the preparation of multi-component composite absorbers,which utilize the synergistic effect of multiple materials to improve the microscopic morphology and microwave absorption properties of absorbing nanomaterials.However,such multicomponent absorbers tend to be heavy and thick,with complicated preparation processes and difficult-to-analyze direct synergistic mechanisms,ultimately resulting in a limited application range.Therefore,improving the microwave absorption performance of single-component materials still holds significant research value.Transition metal sulfides have demonstrated a wide range of applications in wave absorbers due to their high dielectric loss and excellent chemical stability.In this thesis,transition metal sulfide nanomaterials are prepared using a hydrothermal method.The microwave absorption performance of single-component transition metal sulfide absorbers is improved by controlling the reaction temperature,thereby enhancing the microscopic morphology and crystalline phase.The specific studies conducted in this thesis are as follows:(1)A simple hydrothermal method was used to prepare two-dimensional heterogeneous cobalt sulfide nanosphere wave-absorbing materials with petal-like microscopic morphology.The best microwave absorption capacity of the cobalt sulfide samples was achieved by adjusting the hydrothermal reaction temperature.As the hydrothermal reaction temperature increased,the petallike surface structure of the cobalt sulfide gradually disappeared,and the decrease in specific surface area had a negative effect on the microwave absorption capacity of the absorber.By adjusting the hydrothermal reaction temperature to 200°C,a 50% filled cobalt sulfide sample achieved a minimum reflection loss of-48.4 d B at 16.8 GHz band,while the effective absorption bandwidth at Ku band was 4.3 GHz with a matching thickness of only 1.5 mm.By adjusting the sample matching thickness from 1.5 mm to 5.0 mm,the maximum effective absorption bandwidth could cover almost the entire frequency range.These results demonstrate that the cobalt sulfide absorbing material prepared by adjusting the hydrothermal reaction temperature possesses strong electromagnetic wave attenuation ability,is lightweight,has a thin matching thickness,and is simple to synthesize.It is a singlecomponent absorbing material with practical application prospects.(2)A two-dimensional layered heterogeneous nickel sulfide nanosphere material with outstanding absorbing properties was prepared using a simple hydrothermal method.By adjusting the hydrothermal reaction temperature,the best absorbing properties of nickel sulfide samples at different temperatures were obtained.At a reaction temperature of 210℃,the nickel sulfide sample with a 50% filling rate achieved a minimum reflection loss of-25.41 d B in the 15.04 GHz band.The sample had a matching thickness of only 1.5 mm,and the effective absorption bandwidth reached4.24 GHz.As the hydrothermal reaction temperature increased,the overall particle size of the nickel sulfide nanoparticles tended to increase,and the specific surface area decreased,ultimately affecting the microwave absorption capacity of the sample.The results demonstrate that the nickel sulfide absorbing material possesses excellent electromagnetic wave attenuation ability and good impedance matching.It is a single-component absorbing material with promising application prospects.