球形钴颗粒的制备及吸波性能研究（英文）

Preparation and Microwave Absorption Properties of Spherical Cobalt Particles

以CoSO_4·7H_2O为钴源,C_4H_4KNaO_6·4H_2O为络合剂,N_2H_4·4H_2O为还原剂,NaOH为pH调节剂,CTAB为形貌控制剂,通过液相还原法成功制备出了具有特殊形貌的球形钴颗粒。采用扫描电子显微镜(SEM),X-射线衍射仪(XRD),振动样品磁强计(VSM)以及矢量网络分析仪对钴颗粒形貌、晶体结构、静磁性能以及微波频段内的电磁参数进行表征。研究表明钴颗粒的比饱和磁化强度为123(A·m^2)/kg,矫顽力为176×79.6 A·m^(-1)。钴颗粒在9.8、15 GHz时出现明显介电损耗峰。钴颗粒复磁导率实部随着频率增加逐渐降低,显示了良好的频散特性,而虚部在微波频段内呈现宽化的共振峰,经分析为自然共振和交换共振共同作用所致。根据传输线原理计算反射损耗,发现当厚度为5.5 mm时在12.4 GHz处得到最大反射损耗13.2 dB,此时有效损耗频宽(≤10 dB)为1.6 GHz,表明实验制备的钴颗粒具有良好的吸波特性。

Spherical cobalt particles with special morphology were prepared on a large scale through a simple and low-cost liquid reduction method. The morphology, crystal structure, static magnetic properties and electromagnetic behavior of the cobalt particles were measured by SEM, XRD, VSM and vector network analyzer, respectively. The results show that saturation magnetization of the Co particles is 123（A·m^2）/kg, less than that of hcp-Co single crystals, and the coercivity is 176 ×79.6 A·m^-1, larger than that of bulk cobalt crystals. Furthermore, dual-nonlinear dielectric resonances appear at 9.8 and 15 GHz. The real part of permeability decreases with the frequency increasing, presenting an excellent frequency dispersion property. Meanwhile, the imaginary part of permeability reveals a wide resonance peak over the microwave frequency range. According to the transmit-line theory, the reflection loss（RL） was predicted through the permittivity and permeability for a given frequency and absorber thickness. A maximum reflection loss of-13.2 dB is achieved at 12.4 GHz with a thickness of 5.5 mm, and the effective absorption bandwidth-10 dB） is 1.6 GHz, indicating the as-prepared cobalt particles have potential applications as a candidate for microwave absorption.