Compact metal deposit

The different interactions between a substrate and 3D compact metallic deposit determine the physical, mechanical and chemical properties of compound materials which are of great importance in modern electronic devices [6.133]. The aim of these investigations is to produce deposits with predesignable, variable, and controllable composition for the realization of custom-tailored materials. 

Different ways of the structural classification of deposits exist. In one system, the following structures are distinguished arbitrarily (1) fine-crystalline deposits lacking orientation, (2) coarse-crystalline deposits poorly oriented, (3) compact textured deposits oriented in field direction (prismatic deposits), and (4) isolated crystals with a predominant orientation in the field direction (friable deposits, dendrites). The structure of metal deposits depends on a large number of factors solution composition, the impurities present in the solntion, the current density, surface pretreatment, and so on. 

A very general rnle can be formnlated In metal deposition, higher activation polarization will favor the formation of fine-crystalline, compact deposits. Friable, coarse-crystalline deposits are formed in the deposition of poorly polarizable metals in solutions of simple salts, bnt relatively compact, fine-crystalline deposits are formed in the deposition of metals having high polarizability. A strong increase in polarization, and hence the formation of fine-crystalline deposits, will resnlt when... 

Partial dissolution of an active mass often leads to poor cyclability by compaction and loss of the double percolation, electronic and ionic conductivity, necessary for a successful operation. This is especially true for PbS04, in diluted H2S04 (discharged battery). Metallic deposition in the separator of a dissolved metal may cause short circuits, accelerated self-discharge, and may prevent subsequent charging. 

Another example of the analytical utility of the sample compaction methodology for GD-MS is work by Wayne [44] that used a Kratos double-focusing analyzer for the analysis of precious metals deposited on cordierite supports (i.e., automotive catalysts). Spectral interferences from TaO species on the target palladium, rhodium, and platinum analytes made aluminum a better choice as the matrix element. Because the Kratos instrument does not have cryogenic cooling... 

Figure 3 A schematic view of formation of multilayer surface films on active metals exposed fresh to solution phase. Stage I Fresh surface-nonselective reactions Stage II Initial layer is formed, more selective surface film formation continues Stage III Formation of multilayer surface films Stage IV Highly selective surface reactions at specific points partial dissolution of surface species Stage V Further reduction of the surface species close to the active metal, deposition-dissolution of surface species at steady state the surface film is comprised of a multilayer inner compact part and an outer porous part.

Texture and morphology of compact 3D Me deposits determine their physical, mechanical, and chemical properties. 3D Me phase formation includes the formation of isolated 3D crystallites, their further growth and overlapping, and the final formation of the compact 3D metal deposit. 

Figure 6.1 Different types of compact 3D metal deposits according to Fischer [6.8]. (a) Field-oriented isolation type (FI) of an Ag deposit (b) field-oriented texture type (FT). Cross section of Cu deposit from acid CUSO4 solution with addition of /5-naphthaquinoline (c) base-oriented reproduction type (BR). Cross section of Cu deposit (d) randomly-oriented dispersion type (RD). Cross section of Cu deposit from acid CuSO solution with addition of naphthaquinoline.

The transition from the initial nucleation stages of metal deposition to 3D compact bulk deposits is described in the sixth part. Nanoscale structuring and modification of solid state surfaces by in situ STM and AFM are also considered. 

The sound from your new compact disc (CD) is so clear and crisp that it seems as if the musicians are in the same room. The clarity of the sound is possible thanks to the chemical process of metallic depositing and electroplating used in the manufacturing of CDs. 

Another example of a galvanic cell reaction is provided by open circuit corrosion of the metal deposit. Freshly deposited (and particularly finely-divided) metals are more active than their bulk, compact counter parts. Corrosion of the mixed electrode deposit may ensue if the cathode surface is left under open circuit conditions metal dissolution is balanced via reduction of species such as dissolved oxygen, protons or higher oxidation states of transition metal ions. Illustrative (simplified) examples of such oxidising agents include the following ... 

In this study we summarize the recent developments in catalyst development in which nano-porous catalytic sites are accessible through a network of arterial micro-pores. These catalysts are obtained through a solution deposition of metals on a micro-porous polymeric template which is subsequently heat-treated to obtain porous metallic structures where the size of the pores ranged from tens of micrometers to tens of nanometers thus eliminating the problems of accessibility and rapid pore fouling and closure. The technique differs fundamentally from the compression-based systems where the porosity is reduced as a result of compaction. It also differs from the well-known wash-coating or chemical vapor deposition techniques. Furthermore, the mechanisms of metal deposition within micro-pores and nano-structure formation are novel. The importance and current fabrication techniques of porous metallic systems can be found in Refs. l... 

Silver Silver is one of the oldest metal deposits used for corrosion protection of less noble metals. Because of the very high deposition rate, compact and bright deposits can only be obtained if the free silver ion concentration is controlled by complexing agents. The most widely used bath is a cyanide bath. Cyanide-free electrolytes have also been developed. A typical cyanide bath for bright silver deposits is given in Table 11. 

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. 

The classification of electrode film systems is proposed based on the above ideas, and main qualitative regularities of the electrolytic processes in the film systems of different kind are envisaged in Chap. 4. In particular, the mechanism of formation of cathode deposits is considered. It is shown that the deposition of metal-salt carrots or compact metal layers depends on the properties of the cathode film system (prevailing type and ratio of the electronic and ionic conductivity of the film). The nature of crisis phenomena at the electrodes is also analysed (anode effect in fluoride melts, complications at the electrolytic production of Al-Si alloys in industrial-scale electrolytic cells), the mechanisms are elaborated and the means to escape the crises situations are developed. 

The cross sections of the copper and cadmium deposits obtained at //i < // < tjc, and // > //c are shown in Fig. 2.15a, b, respectively. It can be seen that there is no dendrite formation when t] < t, both compact and dendritic deposits are formed when rjidendritic metal is deposited when rj > This is in perfect agreement with findings of Calusaru [44] for the morphology of deposits of the same metals deposited at overpotentials corresponding to full diffusion control. 

Hence, the increasing nucleation density is also due to the decreasing zero nucleation zone radii. This effect leads to an increased coverage of the foreign substrate by the same quantity of deposited metal and to a decreased porosity, a surface resistance and an increased density of a deposit. Also, it can be expected that increase in compactness of a deposit is associated with a decrease in internal stresses and increased ductility and hardness of metal deposits [7]. 

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