Surface Modification And Metallization Of Aluminum And Rare Earth By Dopamine Oxide Polymerization And Eletroless Plating

Inspired by mussel adhesive proteins excreted by marine mussels, it has been reported that the main ingredient-3,4-dihydroxyppheylalanine(DOPA) has great ability to form strong adhesive interaction with all types of inorganic, organic and metal surfaces through oxidative polymerization. We used dopamine self-polymerization to modify the surface of materials and used the functional groups to produce new functional layer, including self-assembled monolayers through deposition of long-chain molecular building blocks, metal films by electroless metallization, and bioinert and bioactive surfaces via grafting of macromolecules.In this study, surface modification of aluminum microspheres(Al) and gadolinium hydroxide(Gd(OH)3) were carried out by utilizing dopamine self-polymerization and deposition. Electroless plating of silver on the as-prepared surfaces was performed to prepare conductive surfaces. The details of the work are as follows:(1) A novel method for the preparation of highly conductive silver-plated aluminum microspheres (Al) was demonstrated. The surface of the aluminum microspheres was functionalized by a bio-inspired polydopamine (PDA) coating. Electroless plating of silver was then carried out on the functionalized aluminum microspheres. An aqueous solution of silver nitrate is used as silver precursor and glucose is used as reducing reagent. The overall procedure is fast, simple, nontoxic, as well as controllable. The surface compositions and the crystalline structure of the modified aluminum microspheres were studied by X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD), respectively. XPS results show that the Al-PDA surfaces were successfully deposited with polydopamine and were ready for electroless deposition of silver. Scanning electron microscopy (SEM) was used to study the morphology of the Al-Ag bimetallic particles. SEM results show that the silver-plated aluminum core-shell microspheres have a continuous, uniform, and compacted silver layer. The as-prepared Ag/Al particles possess high electrical conductivity.(2) Polydopamine was deposited on the surface of gadolinium hydroxide, and dopamine was used as the mid-layer so as to introduce the catechol compounds and amino groups. In the process of electroless plating, the Gd(OH)3-PDA was dipped into the silver ammonia solution, and glucose was used as reducing agent. We can obtain silver plated gadolinium hydroxide with different thickness and density of silver. We studied the influence of the pH, concentration and reaction time of dopamine on the deposition of polydopamine and the influence of the concentration of silver nitrate on the conductivity of silver plated gadolinium hydroxide. The results showed that the optimum conditions of the polydopamine deposition were as follows:pH=8.5, concentration= 2g·L-1, time=20 h. The conductivity of silver plated gadolinium hydroxide was various with different concentration of silver nitrate. The conductivity was best when the concentration of silver nitrate was 10g·L-We can get by controlling the reaction conditions. The method used in our study is simple and cheap. The technology can be applied in surface metallization of other materials and provide a new idea for surface metallization.