In-Situ Observation of Coherent Microradiology in Metal Electrodeposits Growth

• Main Authors: Pei-Cheng Hsu, 許倍誠
• Other Authors: Chao-Sung Lin
• Format: Others
• Language: en_US
• Published: 2008
• Online Access: http://ndltd.ncl.edu.tw/handle/67307602968305281631

博士 === 國立臺灣大學 === 材料科學與工程學研究所 === 96 === Metal electrodeposition is one of the oldest and most established technologies. However, there is a substantial margin for improving the electrodeposits by better understanding its basic mechanism. The observation tool is a quite important role for this objective. In this dissertation, the metal electrodeposition is studied by a novel real-time synchrotron X-ray microradiology. Real-time radiography permits continuous inspection of growth structure, which has sufficient time resolution to capture the fast evolution, adequate lateral resolution to relevant microstructure. There are three parts in this study, including the ramified formation in zinc electrodeposition, the ramified formation in copper electrodeposition, and the effect of boric acid in nickel electrodeposition. In the first part, it is showed that the effect of hydrogen bubble evolution on zinc ramified growth and detailed zinc ramified feature under potentiostatic and galvanostatic mode. The degree of hydrogen bubble evolution increases with applied potential and current density. In particular, the zinc ramified electrodeposits transit from dense-branching morphology to fern-like dendrite, it is because that the fern-like dendrite completely forms by constricting of hydrogen bubbles. The end of morphology is entirely different between potentiostatic and galvanostatic mode. In the second part, it is systematically investigated that the ramified structure of deposits plated from various concentrations of copper sulfate and sulfuric acid. In the sulfuric acid-free solution, the copper electrodeposits appear consistent in dense-branching morphology at the applied potential in the vicinity of limiting current density. In particular, the morphology transition from needle-like dendrite to dense-branching is observed at the applied potential far above limiting current density. The detail transition process is discussed in this study. When the sulfuric acid is added to the plating solution, the highly porous ramified structure constructed from thin-branching morphology is created in the deposition. Last part, the effect of boric acid on the growth of nickel deposits from sulfate bath and Watts bath is demonstrated. From boric acid-free of sulfate bath, the nickel deposition accompanied with very strong hydrogen bubble evolution, causing the interior of nickel deposits, crack formation and fracture during deposition. In the Watts bath, the hydrogen bubble evolution became very weak during nickel deposition. The deposition can perform at higher applied potential.