Octahedral Fe3O4 nanoparticles with high crystallinity and uniform size were synthesized by simple oxidation precipitation method. The phase structures, morphology, particle size and magnetic property of the products were characterized by X-ray diffraction(XRD), transmission electron microscopy(TEM) and vibrating sample magnetometer (VSM), respectively. The products with an average size of 43nm exhibits room-temperature ferromagnetic behavior, and specific saturation magnetization of 74.2 A·m2/kg and coercive of 7.4 kA/m. The electromagnetic parameters of composites of octahedral Fe3O4 nanoparticles and paraffin wax were measured using vector network analyzer in the frequency range of 0.5 to 18 GHz, and the microwave absorbing properties of composites were investigated. It was found that the composites have excellent microwave absorption properties. The reflection loss (RL) peak shifts to a lower frequency with increasing thickness, the peak value and number also change with the thickness. For sample with matching thickness of 2.8 mm, the minimal reflection loss reaches -22.5 dB at 10.8 GHz.%利用简便的氧化沉淀法制备出了结晶度高、粒径均一的八面体Fe3O4纳米颗粒.通过X射线衍射(XRD)、透射电子显微镜( TEM)和振动样品磁强计(VSM)对产物的结构、形貌、粒径及磁性能进行了表征.制备的八面体Fe3O4纳米颗粒平均粒径为43nm,在室温下表现出铁磁性,比饱和磁化强度和矫顽力分别为74.2 A.m2/kg和7.4 kA/m.利用矢量网络分析仪对Fe3O4纳米颗粒-石蜡复合样品在0.5～18GHz频率范围内的电磁参数进行了测量,研究了复合样品的微波吸收性能.结果表明,复合样品具有良好的微波吸收,吸收峰位随着样品厚度的增加向低频移动,峰值和吸收峰数目也随样品厚度而变化,当匹配厚度为2.8mm时,在10.8 GHz反射损失最小值达到了-22.5dB.
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