Study On Electroless Deposition Of Platinum On Titanium Substrates In Alkaline Bath

The platinum-plated titanium is already widely applied in aviation, corrosion-resistance material, electrolytic industry, ship negative electrode protection and so on. However, the technology about platinum plating on titanium gives first place to electroplating, and reports about electroless plating are very few. However, there many disadvantages which don't exist in electroless plating in electroplating. For example , electric field line is not distributed symmetrically, and the capability of uniform and deep depositing is not enough. So it is very necessary to develop electroless plating platinum. In this dissertation, a kind of alkaline bath is applied in electroless plating platinum on titanium panel and porous panel. Based upon numerous experiments, various technical aspects are studied, such as the pretreatment of the titanium base, the concentration proportion among the bath components, the inductive process of electroless deposition and the heat treatment after deposition. Finally, adherent and uniform layer of platinum is deposited on titanium substrate successfully.There are four parts in the dissertation:In chapter 1, the application of platinum-plated titanium material and the significance of the electroless plating platinum on titanium are introduced. Some methods of platinum deposition on metal substrates, national electroplating platinum on titanium and some methods of electroless plating platinum on titanium substrate in foreign patents are evaluated. The innovation and primary coverage are showed.In chapter 2, the study methods and experimental instruments which are involved are introduced.In chapter 3, the electroless plating platinum bath in this dissertation is showed.,using p salt[Pt(NO2)2(NH3)2] as main deposition metal salt and hydrazine as primary reducing agent. The pretreatment method of titanium substrates is studied, and the result shows that the method which is adapted to the alkaline bath is as follow: titanium substrate is etched in HCl-H2SO4 solutions to enhance the roughness and then dipped in the palladium chloride (0.1g/L) for activation. Mixed potential method is used to study the induction process, and the effect the working temperature and the concentration proportion among the bath components on the deposition rate are discussed, so the optimum technological conditions is: the bath consisted of Pt(NO2)2(NH3)2 (0.5g/L), hydrazine (12g/L), hydroxylamine hydrochloride (5g/L), and the working temperature is 45~50℃. The method of electroless deposition platinum on porous titanium substrates is explored, and the ultrasonic cleaning method is suggested. The result of experiments show that the technological conditions in this dissertation could realize electroless deposition platinum on the surface of micropore in Ti substrate, so that it can ensure the over-all covering.In the chapter 4, The influence of heat treatment on the morphology , structure, composition distribution of the platinum deposits and plating adhesion are demonstrated. The platinum deposition is extensively studied by various electrochemical methods and modern surface analytical techniques, such as scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and cyclic voltammetry (CV). The result shows that heat treatment plays a very important role in enhancing plating adhesion. The plating adhesion of annealed deposit is better than as-plated deposit. When the electrochemical catalytic activity is regarded, the platinum-plated titanium panel is better than pure platinum electrode, and the platinum-plated titanium porous panel is better than platinum-plated titanium panel. It can be conclude that the platinum-plated titanium porous panel is more suitable to used in electrochemical instrument. However, if higher electrochemical catalytic activity is desired, heat treatment is unnecessary.The innovation of the study is as follows:1. technological process of electroless deposition of platinum on titanium substrates in alkaline bath, using p salt[Pt(NO2)2(NH3)2] as main deposition metal salt and hydrazine as primary reducing agent, is presented. Adherent and uniform layer of platinum is obtained on titanium substrate.2. The effect of bath composition on induction process and deposition rate of electroless plating platinum on Ti substrate is demonstrated.3. The electrochemical catalytic activity of the platinum-plated Ti panel and porous panel is explored.