对比研究了2种内应变水平和晶粒大小不同的Fe粉在微加工过程中的形貌演变和微波电磁性能的变化规律. 结果表明, 与羰基Fe粉相比, 表面粗糙度和内应变水平较大, 晶粒较小的自制Fe粉在形状控制剂的协助下, 经10 h的微加工就能得到大而薄的片状Fe粉; 延长微加工时间($t$)至12 h, 存在的高内应变使片状结构破碎, 宽度减小; 进一步延长至t=24 h, Fe粉继续变薄, 制备出宽厚比较大、宽度较小的片状Fe粉. 该片状Fe粉同时具有高的磁导率和较低的介电常数, 用其组成的环氧树脂基复合材料在体积分数为20%, 厚度为1.5 mm时反射率小于-10 dB的带宽为8.2 GHz, 最低反射率为-14.6 dB.
The micro–fabricating process and electromagnetic properties of two kinds of Fe powders with different grain sizes and internal strains were studied. The results show that the homemade Fe powders with smaller grain size, larger internal strain and surface roughness than the carbonyl Fe powders, evolve into big and thin Fe flakes by micro–fabricating for 10 h with the help of the process control agent (PCA). When micro–fabrication for t=12 h, these Fe flakes will fracture and their average width will reduce due to strong internal strain. When t is further prolonged to 24 h, these Fe flakes become thinner, finally, those with larger aspect ratio and smaller width can be obtained, which show high permeability and low permittivity. The epoxy resin-based microwave absorbing materials containing such Fe flakes of 20% (volume fraction) exhibit a reflection loss less than −10 dB in the 9.4—17.9 GHz frequency range with a minimal peak of −14.6 dB, whose average thickness is 1.5 mm.
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