Influence Of Process Parameters Of Stirred Milling On Structure And Microwave Electromagnetic Properties Of Flaky Iron

As a kind of magnetic loss absorbing agent, carbonyl iron with high saturation magnetization, high temperature stability and low prices is one of main subjects in the areas of microwave-absorbing materials. Compared to spherical carbonyl iron, flaky carbonyl iron with high shape anisotropy has higher permeability and better microwave-absorbing properties. To prepare flaky carbonyl iron, this paper focus on preparing flaky carbonyl iron by stirred milling.The influence of process parameters of stirred milling on structure and microwave electromagnetic properties of prepared flaky iron was studied.First, we studied the influence of milling ball on structure and microwave electromagnetic properties of flaky iron fabricated by stirred milling. The results show that samples obtained by stirred milling with different milling ball have different structure. Samples obtained by stirred milling with ZrO2 milling ball of diameter 1.5 mm are irregular with rough surface, not flaky. Samples obtained by stirred milling with steel milling ball of diameter 6 mm are breaking and irregular, not flaky. Samples obtained by stirred milling with ZrO2 milling ball of diameter 6 mm are flaky. Electromagnetic parameters show that the flaky carbonyl iron has higher permeability and permittivity than the spherical carbonyl iron.Then, we studied the influence of ball/power ratio and power/liqiud ratio on the micro-fabricating process of flaky iron and the influence of liqiud medium on structure and microwave electromagnetic properties of flaky iron fabricated by stirred milling. The results show that the ball/power ratio is higher, the micro-fabricating process is faster; the power/liqiud ratio ratio is higher, the micro-fabricating process is slower. The micro-structure of flaky carbonyl Fe can be controlled by liquid medium. The micro-fabricating process by stirred milling with PEG400 as liqiud medium is slower than the micro-fabricating process with ethanol as liqiud medium. It is due to that PEG400 has higher viscosity to prevent the moving of milling ball. It can weaken the micro-fabricating of particles. The flaky carbonyl Fe fabricated by stirred milling with low polar cyclohexane has more perfect flaky structure and less breaking than the flaky carbonyl Fe fabricated with ethanol as liquid medium. When stirred milling for 24 h, the flaky carbonyl Fe fabricated with cyclohexane has same permeability and lower permittivity than the flaky carbonyl Fe fabricated with ethanol. The epoxy resin-based microwave absorbing materials containing this Fe flakes exhibit reflection loss of less than-15 dB in 12.6～17.4 GHz frequency range with a peak of-33 dB when the thickness is 2 mm and the volume ratio of Fe flakes in the materials is 8%.Finally, we controlled the technology of stirred mill to prepare a ultrathin flaky carbonyl iron. Carbonyl iron is first dealed with by stirred milling with ZrO2 milling ball of diameter 6 mm for 24 h, and brokened by planetary mill for 1 h, and then is dealed with by stirred milling with ZrO2 milling ball of diameter 1.5 mm for 24 h. At last, The prepared flaky sample is 0.2μm in thickness.