退火对Ni/TiO_2纳米复合材料吸波性能的影响

Influence of annealing treatment on Microstructure and Waves Absorption of Ni/TiO_2 Nanocomposites

采用机械化学法制备了Ni/TiO2纳米复合材料,制备态样品由六角形结构的金红石TiO2和面心立方结构的Ni组成。退火使样品晶格缺陷和内应力减少,Ni晶粒尺寸和饱和磁化强度明显增大。退火后,TiO2的本征发光峰、自由激子及束缚激子引起的发光峰都发生红移,其原因是能带结构的畸变。制备态样品在15 GHz产生强烈的非线性介电共振,并呈现明显的Cole-Cole半圆。当吸收厚度为8 mm时,在14-16 GHz范围内的反射损耗值(RL)都超过了-10 dB,且在15 GHz处出现最优RL值-32 dB。退火使制备态样品在2.8和5.2 GHz处的自然共振明显加强,2-6 GHz范围的吸波能显著提高。

Ni/TiO2nanocomposite was prepared by mechano- chemical synthesis. The as- milled nanocomposite consists of hexagonal-structure rutile TiO2and face-centered cubic structure Ni. Annealing treatment decreases both the lattice defects and the internal stress, while remarkably increases the grain size of metal Ni and the saturation magnetization. After annealing treatment the intrinsic emission, free exciton emission and bound exciton emission peaks of TiO2exhibit a red shift, for which the reason may be the distortion of the band structure. For the as-milled nanocomposite an intense nonlinear dielectric resonance occurs at 15 GHz and a clear Cole-Cole semicircle was observed. Meanwhile, a reflection loss(RL) exceeding-10 dB in a frequency range of 14-16 GHz and a maximum value of RL as large as-32 dB are obtained for an 8 mm thick absorber. After annealing treatment the intensity of the natural resonances at 2.8 and 5.2 GHz has been significantly strengthened, leading to a remarkable improvement of microwave-absorption properties in the frequency range 2-6 GHz.