Activation by Displacement Deposition

Silicon can be made catalytic for the electroless deposition of Ni by replacing the surface Si atoms with Ni atoms [59] 

This reaction is called displacement deposition since the nickel ions in solution simply displace the silicon at the surface. The substrate, Si, acts here as a reducing agent as will be discussed in Sect. 3.4. Copper may be deposited on Si from HF acid solutions [60]. In the presence of HF, Si is oxidized into [SiF6]2.  

Similarly, aluminum substrates can be activated by a displacement reaction [1] 

---

Activation by Thermal Decomposition of Metallic Oxides. The surface of alumina, AI2O3, may be activated by employing laser or ultraviolet irradiation to decompose AI2O3 (68). Decomposition of AI2O3 results in the generation of aluminum particles that are catalytic for electroless deposition of Cu (the first reaction probably is displacement deposition). 

The kinetics and mechanisms of the displacement deposition of Cu on a Zn substrate in alkaline media was studied by Massee and Piron (5). They determined that at the beginning of the deposition process, the rate is controlled by activation. The activation control mechanism changes to diffusion control when the copper covers enough of the Zn surface to facilitate further deposition of copper. This double mechanism can explain the kinetic behavior of the deposition process. 

Out of the hundreds of proteins that our plasma contains, we must expect that for a random choice of most pairs, the dissolved species of protein facing a surface completely occupied with the preadsorbed species of protein, can only be deposited by displacing the preadsorbed species. Many experiments have been published to show how one protein can "inhibit surface activation of a clotting factor such as high molecular weight kininogen or factor XII, while in fact the surface is merely blocked nonspecifically by preadsorption of a protein that is not easily displaced. 

By the definition, the galvanic displacement deposition is a heterogeneous process in which the noble metal is deposited at the surface of an active metal [1]. The consequence is that the less noble (or active) metal is oxidized or dissolved in the appropriate solution. As a result, the ions of a more noble metal present in the solution are reduced leading to the deposition of the more noble metal. This situation can be described using the electrochemical half reactions in the following way. 

The characteristics and bending performance of the novel electroactive polymer blend P(3HB)/cellulose in terms of free bending displacement output, electrical power consumption and lifetime were studied by Zhijiang et al. Cellulose is a potential smart material which responds to an ith electric field. Electro-active polymer (EAP) was prepared by dissolving cellulose and P(3HB) in trifluoroacetic acid. The solution was cast to form a film followed by the deposition of a thin gold electrode on both sides of the film. 

C20-0109. In Zn purification by electrochemistry, ZnO is dissolved in sulfuric acid. Before deposition, zinc powder is added to displace less active metals, such as cadmium. Use E ° values and balanced equations to show how this is accomplished. 

In ion exchange equipment, cations or anions from the fluid deposit in the solid and displace equivalent amounts of other ions from the solid. Suitable solids are not necessarily porous the ions are able to diffuse through the solid material. A typical exchange is that of H + or OH ions from the solid for some undesirable ions in the solution, such as Ca++or SOa. Eventually all of the ions in the solid are replaced, but the activity is restored by contacting the exhausted solid with a high concentration of the desired ion. for example, a strong acid to replace lost hydrogen ions. 

---