采用机械化学法制备了 Ni/TiO2纳米复合材料,并对制备态样品在100和200℃退火30 min.样品均由六角形结构的金红石 TiO2和面心立方结构的Ni组成.随着退火温度的增加,Ni 和 TiO2的晶粒尺寸都有所增加,与此同时内应力释放使矫顽力减少.退火使TiO2的本征发光峰、自由激子、束缚激子和氧缺陷引起的发光峰都发生蓝移,这被归结为能带结构的畸变.100℃退火样品呈现多重非线性介电共振和强烈的自然共振现象,当样品厚度为1．9 mm 时,在17．5 GHz 处最佳反射损耗(RL)值为-29．6 dB,且在此厚度下,超过-10 dB 的频宽几乎覆盖了 Ku 波段(12．4~18 GHz)；另外,厚度在8~10 mm 范围内,超过-10 dB 的频宽几乎覆盖了整个 X 波段(8~12 GHz).该体系优异的电磁波吸收性能来自于样品中的多重非线性介电共振、自然共振和良好的电磁匹配.
Ni/TiO2 nanocomposites were prepared by the mechanochemical synthesis and then annealed for 30 min at 100 and 200 ℃.The annealed samples were composed of hexagonal-structure rutile TiO2 and face-cen-tered cubic structure Ni.In comparison with the sample annealed at 100 ℃,the sample annealed at 200 ℃ had lager grain sizes of Ni and TiO2 ,and meanwhile the release of the internal strain led to a decrease of the coerciv-ity.The intrinsic,free exciton,bound exciton and oxygen-defect emission peaks of TiO2 exhibited a blue shift, which was ascribed to the distortion of the band structure.The nonlinear dielectric resonance and natural reso-nant behavior were observed in the sample annealed at 100 ℃.A maximum of reflection loss (RL)as large as-29.6 dB at 17.5 GHz with RL values exceeding -10 dB in almost whole Ku-band(12.4-18 GHz)was obtained for a layer of 1.9 mm thickness.In particular,A RL exceeding -10 dB was calculated in the whole X-band (8-12 GHz)for an absorber thickness of 8-10 mm with the optimal RL of -23 dB.The great improvement of mi-crowave-absorption properties for the Ni/TiO2 nanocomposite annealed at 100 ℃ could be ascribed to nonline dielectric resonance,natural resonant and an excellent match of magnetic and dielectric loss.
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