| Summary: | 碩士 === 國立臺北科技大學 === 材料科學與工程研究所 === 106 === This study is to prepare a multifunctional coating with acoustic absorption and anti-corrosion by thermal spray. In the marine environment, the problem of corrosion resistance is particularly important. Spray zinc-aluminum alloy as an anti-corrosion coating, aluminum can form a passivation film on the surface as a barrier protection, zinc as a sacrificial anode to protect the internal steel, and then spray polymer materials as a sealing layer to increase the anti-corrosion effect. In addition, the polymer materials had the characteristics of viscoelastic damping and can absorb incident sound waves. In this study, expanded graphite and aluminum powder were added to the polyethylene sealing layer to improve the sound absorption performance. In addition, the multi-layer composite structure is formed by changing the composition of the coating to improve the acoustic absorption performance. Solve the question that high-loss material causes strong reflection due to acoustic impedance mismatch and low-loss materials cannot effectively attenuate sound energy.
The experimental results showed that the Zinc-Aluminum layer didnt change the composition and phase after thermal spraying; Added expanded graphite in to PE as a sealing layer, the SEM surface morphology and cross section showed that the porous structure could be formed. Added aluminum powde in to PE as a sealing layer, no obvious holes were observed. Compared with the sealing layer that added expanded graphite, the sealing layer that added aluminum powder has higher density; From the slices obtained from computed tomography scans, the coating with gradient acoustic impedance can be observed that the content of the added fillers shows a gradient change, and the multi-layered composite sealing layer can be observed that the types of fillers added to each layer and the distribution of the fillers; The results of the acoustic data show that the sound absorption coefficient of the sealing layer of expanded graphite decreases with the increase of the amount of expanded graphite. Adding aluminum powder to the sealing layer does not effectively improve the sound absorption coefficient, because the acoustic impedance mismatch, causing a lot of reflections. The two are structurally designed to form an impedance-graded sealing layer, which has the best sound absorption coefficient in a wider frequency range.
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