Electroplating, of metals

Numerous metal and alloy coatings can be prepared by electrodeposition and are suitable for nano-plating technologies, including Ag, Au, Cd, Co, Cr, Cu, Fe, Ni, Pt, Sn, Zn, and most alloys of the listed metals [7], Either a fairly inert counter electrode, such as a Pt mesh, a carbon rod, or a plate of the metal to be plated are used. In the latter case, the zero valent metal of the anode is oxidized and dissolved at the same rate as metal ions are reduced a the working electrode. In this manner, the cations concentration of the electrolyte bath is continuously replenished. In industrial applications usually a galvanostatic is favored over a potentiostatic deposition technique. 

Unlike the metal oxide or hydroxide electrodeposition, metal plating typically only involves a simple Faradaic reaction with the direct reduction of the metal cations at the cathode to yield the desired deposit in the metallic, zero valence state. 

This reaction mechanism which proceeds without any intermediate reactions involving other species generally favors a compact deposit and closely obeys Faraday s law, see Eq.(5.1), making a precise control over the deposition rate and thickness possible. Furthermore, the metal deposit is much more stable than the corresponding metal oxides that might be hydrated and readily redissolve. Since the metal electroplating is not considered to be a precipitation process, as in the case of various metal oxide depositions, the inclusion of impurities from the electrolyte are less likely. 

Compared to the electrodeposition of the metal oxides, electroplating of the corresponding metal can have several other advantages when attempting the template-assisted nanopatterning. Metallic nickel plating, for example, is considerably faster than the deposition of nickel oxide, see Sect. 5.3.1.1. Metal plating elec- 

While the thermal oxidation of a compact metal surface is usually limited to the growth of an oxide layer with a thickness of a few of nanometers, bulk metal nanostmctures can be fully converted into the corresponding oxide or chalcogenide. Again the relative diffusion rate of metal atoms and the oxidation agent in the oxide determine the oxidation kinetics and structure formation. A topographic transformation to a metal oxide nanostructure is observed when the mobility of the oxidation agent exceeds the one of the metal atoms. When this is not the case, the so-called nanoscale Kirkendall effect (NKE) responsible for the formation of sophisticated hollow nanostructures, such as nanospheres, nanotubes, and nanopeapods, proceeds [2-5]. 

---

HBF4 (aq) and metal fluoroborates electroplating of metals, catalysts, fluxing in metal processing and surface treatment. HzSiF6 and its salts fluoridation of water, glass and ceramics manufacture, metal-ore treatment. 

The major use of sodium cyanamide is in the production of sodium cyanide, a compound that is used extensively in preparing solutions for the electroplating of metals. Another use for NaCN is in extraction processes employed to separate gold and silver from ores as a result of their forming complexes with CN . Sodium cyanide, an extremely toxic compound, is also used in the process known as case-hardening of steel. In this process, the object to be hardened is heated and allowed to react with the cyanide to form a layer of metal carbide on the surface. 

Electroplating of metal matrix composites by codeposition of suspended particles, a process that has improved physical and electrochemical properties. 

Having identified the main features of electrochemistry, the remainder of this chapter will focus on the use of electrolytic cells and will use as examples the electrodeposition (or electroplating) of metals such as copper, zinc, iron, chromium, nickel and silver. The chapter will also consider the electrochemistry of some organic molecules. Electroanalysis will not be considered since a full description is not within the scope of this chapter. Eor those interested readers, there is a review on the topic [2],... 

In 1800. William Nicholson and Anthony Carlisle decomposed water into hydrogen and oxygen by an electric current supplied by a voltaic pile. Whereas Volta had pruduced electricity from chemical action these experimenters reversed the process and utilized electricity to produce chemical changes. In 1807. Sir Humphry Davy discovered two new elements, potassium and sodium, by the electrolysis of ihe respective solid hydroxides, utilizing a voltaic pile as the source of electric power. These electrolytic processes were the forerunners of the many industrial electrolytic processes used today to obtain aluminum, chlorine, hydrogen, or oxygen, for example, or in die electroplating of metals such as silver or chromium. 

Electrolysis is used in the manufacture of many important chemicals and in numerous processes for purification and electroplating of metals. Let s look at some examples. 

Direct electroplating of metals on water-sensitive substrate materials such as Al, Mg and light alloys with good adherence should be possible using ionic liquids. 

Electroplating of Metal Matrix Composites by Codeposition of Suspended Particles... 

Finally, in chapter 6, another direction of applied electrochemistry is treated by Hovestad and Janssen Electroplating of Metal Matrix Composites by Codeposition of Suspended Particles. This is another area of metals materials-science where electroplating of a given metal is conducted in the presence of suspended particles, e.g. of A1203, BN, WC, SiC or TiC, which become electrodeposited as firmly bound occlusions. Such composite deposits have improved physical and electrochemical properties. Process parameters, and mechanisms and models of the codeposition processes are described in relation to bath... 

The electroplating of metals invariably involves gas generation at one or other of the electrodes and the physical presence of the gas acts as a barrier to efficient passage of current (discharge of ions). One of the ways in which ultrasound can improve electroplating—and indeed general electrochemical processes—is by the removal of this gas barrier [76]. 

---