Compared with conventional materials,bio-carbon has emerged as a new class for microwave absorption studies in the past decades.Over the years,with the gradual expansion of the research on biocarbon materials,their naturally inherited morphology,as well as controllable structural characteristics,led to a wide range of potential applications in the fields of gas adsorption,energy storage,electromagnetic shielding and stealth technology.Furthermore,biomass serves as an ideal source to yield highly porous carbon and related composites with a large surface area,controllable pore size,and unique structures regarding their source.During the recent years,the researchers focused on the diverse carbonization approaches and potential applications in this rapidly developing field.In this dissertation,the precursors used to prepare biocarbon samples were obtained from different raw waste materials and the iron oxide component came from industrial waste.The composition,morphology and their application in microwave adsorption have been studied.The biomass materials are taken from different biological wastes such as:wheat straw,cotton fiber,tree leaves,orange peel,peanut shells,etc.The effect of changing morphology,composite with magnetic material and effect of carbon dimensionality on the microwave absorption performance have been investigated.The research results show that the unique morphology,interface polarization,multireflection mechanism and intrinsic properties of the prepared magnetic-biomass composite materials have an important influence on its microwave absorption performance.Following are the main contents of this thesis:1)Bio-derived dielectrics have drawn extensive attention for microwave wave absorption and shielding because of renewability and environmental friendliness.In this work,foam-like bio-carbon has been obtained from wheat straw waste and its microwave absorption performance has been studied.By controlling the precursor ratio of KOH,the optimized morphology of bio-carbon has been realized.The 3D carbon foam obtained at 600℃ with KOH and biomass ratio 1:1（AC-600（1:1）,presents decent microwave reflection loss.Especially,with a low absorber ratio（10 wt%）,the effective absorption bandwidth（RL＜-10dB）can reach 8.8 GHz（7.2-16 GHz）at a matching thickness of 2.5mm.3D porous network,interface effect,defects in carbon network,and dipolar relaxation make a good contribution towards broadband and excellent reflection loss.The eco-friendly,lightweight,and low-cost bio-carbon foam has great application prospects of microwave absorption.2）Biocarbon has emerged as a potential source for carbon-based microwave absorber owing to its low cost,easy manufacturing and low density.Here,we report a simple two step fabrication technique for biocarbon ferrite composite material by using wheat straw waste and industrial waste ZnFe2O4（ZFO）.The micro sized ferrite particles imbedded on carbon surface significantly construct interfaces and provide magnetic loss when electromagnetic wave strike the surface.WS/ZFO composite exhibits reflection loss of-21 dB with an effective absorption bandwidth of 2GHz.The defective surface and synergy between ZFO and biocarbon contribute to impedance matching and better absorption compared with bare biocarbon sample.Meanwhile,the Debye relaxation and interfacial polarization stimulate the attenuation capability of the microwaves.The improvement of attenuation capability and synergetic effect collectively result in enhanced microwave absorption performance.3)In addition to composition,structural design is effective and important for the microwave absorption（MA）property manipulation of ferrite/carbon composites.Here,by carefully designing the dimensionality of the bio-carbon materials,the interfacial geometries as well as MA properties of ferrite/bio-carbon composites have been manipulated effectively.The one-dimensional（1D）,two-dimensional（2D）,and threedimensional（3D）biomass-based carbon materials decorated with ZnFe2O4（ZFO）particles were obtained respectively from carbon fibers（1D）,wheat straw（2D）,tree leaves（2D）,peanut shell（3D）and orange peel（3D）by a simple two-step synthesis method.With increasing of the dimensionality of the bio-carbon from 1D,2D to 3D,the MA properties of the ferrite/carbon composite are promoted and the minimum reflection loss are enhanced from-9,-20 up to-45 dB.By changing the ZFO/3D-bio-carbon samples’thickness,a wide absorption range from 4 to 18 GHz can be covered.Moreover,the effective absorption bandwidth for ZFO/3D-bio-carbon can be modified up to 7.1 GHz,which covers whole Ku band.These observations not only identified the important roles played by the ferrite/carbon interface and dimensionality of carbon materials,but also provide an effective and low-cost route to design microwave absorption materials based on biomass-industrial waste composites.