| Summary: | 碩士 === 國立臺北科技大學 === 材料科學與工程研究所 === 104 === In this research, we using thermal spray technique to fabricate a coating which is multifunction composite with sound absorption and corrosion resistibility in underwater ambience, the Zn-Al coating were protected against corrosion because of the sacrificial anode protection mechanisms of the Zn, and Al created a stable oxide on the coating surface and protects the substrate, as well as, the polymer material which chemical inert not only decreasing inner metal oxidation, but also viscoelasticity cause acoustic absorption etc. characteristic, we can start to spraying and fabricate the coating, where spraying order, first is spraying Zinc-Aluminum alloys as a corrosion coating, and second is, spraying polymer materials as a sealing coating. After spraying the samples will go to impedance tube measurement the properties of acoustic absorption, and using salt spray test to acceleration the Zinc-Aluminum coating corrosion rate, that can evaluation the coating corrosion resistibility, X-ray diffraction to ensure the crystal structure and component of coating, Computed Tomography (CT) to determine the porous structure of three-dimension, using Scanning Electron Microscopy (SEM) to observe the surface topography of coating and cross-sectional microstructure how to influence the properties of acoustic absorption, and after salt spraying coating surface topography.
The results shown, spraying Zn-Al onto the substrate, the thickness is about 300 um, after 5 days salt spray test, we can also see the thickness has not obvious change, However, the thickness has not obvious change, it still has some changes of the microstructure, the micro-cracks were occurring near the surface layer, it means zinc has been considerable sacrificial, which makes the zinc doesn’t as a sacrificial role to protection and make the cracks occur.
The results shown, spraying Zn-Al onto the substrate, the thickness is about 300 um, after 5 days salt spray test, we can also see the thickness has not obvious change, However, the thickness has not obvious change, it still has some changes of the microstructure, the micro-cracks were occurring near the surface layer, it means zinc has been considerable sacrificial, which makes the zinc doesn’t as a sacrificial role to protection and make the cracks occur. Sealing layer part, add different proportion expansion of graphite into the polymer materials to as sealing layer, which can create porous structure, Where, using epoxy containing 20 volume percent expansion of graphite have a good performance on porosity and thickness. Furthermore, add different proportion Micro-spherical glass shell into the polymer materials to as sealing layer, its distribution was non-uniform and morphology was incomplete. The results of acoustic analysis part show that acoustic absorption was between 0.4 to 0.7, while the acoustic absorption decreasing with the hydrostatic pressure increasing , the reasons is mechanical compression on the specimen causing the density change to increase, that caused the acoustic absorption coefficient decreasing.
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