| Electronic devices and equipments have brought electromagnetic pollution issue as well as convenience, which has a negative impact on operation of equipment and human health. Microwave-absorbing material can solve the problem. It is reported that 85%Fe-9.5%-Si-5.5%Al alloy is expected to become remarkable wave-absorbing material due to its high initial magnetic permeability and resistivity. However, Fe-Si-Al alloy can not be directly pressed into microwave-absorbing materials due to its brittle and hardness character. The traditional preparation of the absorbing material is compression moulding,that is binder such as resin or rubber, need to be added as the carrier, then pressed into microwave-absorbing coating or patch, but the binder affects the microwave-absorbing properties. Magnetron sputtering method adopted in this research can get directly nano-sized、micron-sized Fe-Si-Al microwave-absorbing materials without adding binder, which overcomes the effect of binder on microwave-absorbing ability and further improves its applied range.Firstly, Fe-Si-Al target has an effect of electromagnetic shielding because of its ferromagnetism, it is necessary to solve this problem. Secondly, designing a Fe-Si-Al alloy target with reasonable size, structure and composition according to the target characteristics and specific sputtering yield of each element on the target, comparing sputtering method of Fe-Si-Al target with Fe target and Si-Al target, and improving the target ingredients. The result shows that the sputtering cathode with strong magnetic field can meet the need of magnetron sputtering of the ferromagnetic target after improvement. Moreover, Fe-Si-Al target has higher sputtering rate than the pattern of Fe target and Al-Si target. The Fe-Si-Al thin film which is close to Sendust component will be obtained after optimizing target composition.There are some findings in the process of exploring the preparation of Fe-Si-Al thin film:the Ar gas flow rate has a negative correlation with sputtering voltage. Fe-Si-Al thin film has a fine crystalline or amorphous transition state structure when substrate temperature is under 50°C, and has a uniform diffraction peak in 150°C, however, a strong peak appears on a certain crystal face when substrate temperature is more than 200°C. The thickness is not enough to measure the permeability if sputtering time is less than 3 h, but the utilization efficiency of the target is low when it is more than 3 h. Film thickness increases with increasing of sputtering voltage, and the Fe-Si-Al thin films which are close to Sendust component can be obtained when sputtering voltage is in range of 550V-565 V. Therefore, the optimal parameters of preparing Fe-Si-Al thin film are: 20 sccm Ar gas flow rate, 150°C substrate temperature, 550 V sputtering voltage, 0.9 A sputtering current and 3h sputtering time.Finally, analyzing the surface microstructure, phase structure, ingredients ratio, permeability, resistivity of thin film,and exploring its mechanism with different characterization methods, such as high resolution SEM, X-ray diffraction analyzer, Energy dispersive X-ray spectrom, X-ray fluorescence spectrum analyzers, RF impedance analyzer/materials, Four point probe resistance measuring instrument. The result indicates that the grain of Fe-Si-Al thin film which is close to Sendust component is large, similar to oval shape and columnar growth form. The phase structures of these samples are the same steady α-Fe(Si,Al) substitutional solid solution, its resistivity increases with the increase of silicon content increases. And its u ’and u " values are bigger than those of company products. |
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