Papers by Keyword: Microwave Absorption Properties

Abstract: Porous Co/C composite nanofibers were fabricated by combination of electrospinning method and polymer blend. The phase composition, microstructure and electromagnetic characteristics of them were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM) and vector network analyzer (VNA), and their microwave absorption performances were studied. The results indicate that nanofibers were composited by amorphous carbon and face-centered cubic structured Co nanoparticle after sintering. The addition of PMMA is a key factor of nanofibers morphology and the aperture was improved with the increase of PMMA. When the thickness is 2.0 mm, the samples exhibit the best microwave absorption performance. Their effective absorpt ion bandwidths (RL < 10 dB) are 6.3 GHz, 6.2 GHz and 6.1 GHz, and it’s obviously superior to ordinary morphology nanofibers.

Abstract: Magnetite (Fe₃O₄)-graphene nanohybrids having three different weight ratios of magnetite to graphene were synthesized by a facile in-situ deposition method. The combination of dielectric properties of graphene and magnetic properties of magnetite makes the nanohybrids an ideal choice of material for microwave absorption applications. In regards to that, the electromagnetic properties and microwave absorbing characteristics were investigated in a frequency range of 1-18 GHz. The reflection loss (RL) reaches a minimum of-40.44 dB at 6.84 GHz with a thickness of 7 mm for the sample containing 73 wt·% of Fe₃O₄. The bandwidth corresponding to the RL below-10 dB is 7.05 GHz. The as-prepared Fe₃O₄-graphene nanohybrids showed good microwave absorption ability in the low frequency band (C-band) which can be ascribed to improved impedance matching characteristics, enhanced interfacial polarizations as well as the magnetic loss contributions. Moreover, the frequency related to minimum RL could be tuned by varying the weight ratios of magnetite to graphene.

Abstract: The paper provides an overview of surface modification and application of fly ash cenospheres. The state of the art research and development of electromagnetic wave absorption materials based on surface treated fly ash cenospheres are summarized.

Abstract: A novel titanium dioxide （TiO2） nanoparticles coated carbon nanotubes (CNTs) composites were prepared by sol-gel method as microwave absorbing materials in this paper. SEM and XRD researches show that sol-gel method can realize uniform coating of CNTs with TiO2. Among them, with the weight fraction of TiO2/ CNTs composites was 10%, microwave absorption characteristics with a minimum RL value of -34 dB at 6.2 GHz on a coating with a matching thickness of 4mm and <−10 dB was obtained in the frequency range of 4.5-18 GHz with the thickness of 1.5-5.0mm.

Abstract: In order to improve microwave absorption properties of hollow ceramic microspheres (HCMs) and possess the better characteristics of “thinness、width、lightness、strongness”, used Al+Cr₂O₃ as the main reaction system, hollow ceramic microspheres were prepared by SHS flame quenching technology. Microwave absorption properties of HCMs were studied when the additive is Fe. The results show that microwave absorption properties of HCMs depend on the dielectric property of product, such as SiC、mullite, when there is no additive. However, when Fe is used as additive, the microwave absorption properties of HCMs are better. SHS reaction of agglomerate powders is happened in the flame field and SiC、Fe₂O₃、Al₃Fe₅O₁₂、Cr_1.3Fe_0.7O₃、(Fe_0.6Cr_0.4)₂O₃ are synthesized. Except the dielectric property of SiC, magnetic property of HCMs is possessed due to the ferruginous materials are synthesized. So its microwave absorption properties are stronger. Keywords: additive; hollow ceramic microspheres; microwave absorption properties

Abstract: CNTs/HAp thermo-seed material were prepared by a simple and effective coprecipitation and hydrothermal treatment method. The phase structure, composition and morphology of CNTs/HAp composites were examined by X-ray diffraction (XRD), transmission electron microscope (TEM). The results showed that When CNTs content was 10wt%, after hydrothermal treatment, a certain high degree of crystallinity, pure component single HAp layer was obtained on the surface of CNTs successfully. The electromagnetic parameters of CNTs/HAp composites were measured in the range from 0 GHz to 5.0 GHz. The results showed that CNTs/HAp composite had better absorbing properties in the 0-5.0 GHz range. With increasing of CNTs content, the microwave absorbing capacity of CNTs/HAp composite had been gradually strengthened, the absorption peak moved towards high frequency, the bandwidth was increased. When CNTs content was 8wt%, a maximum reflection loss value of -26 dB had been obtained at 3.0 GHz. Therefore, CNTs/HAp composite material is expected as thermo-seed material for tumor hyperthermia.