Properties of deposits

Chemical properties of deposited monolayers have been studied in various ways. The degree of ionization of a substituted coumarin film deposited on quartz was determined as a function of the pH of a solution in contact with the film, from which comparison with Gouy-Chapman theory (see Section V-2) could be made [151]. Several studies have been made of the UV-induced polymerization of monolayers (as well as of multilayers) of diacetylene amphiphiles (see Refs. 168, 169). Excitation energy transfer has been observed in a mixed monolayer of donor and acceptor molecules in stearic acid [170]. Electrical properties have been of interest, particularly the possibility that a suitably asymmetric film might be a unidirectional conductor, that is, a rectifier (see Refs. 171, 172). Optical properties of interest include the ability to make planar optical waveguides of thick LB films [173, 174]. 

Properties of deposits These deposits invariably possess an appreciable number of discontinuities, which diminish their protective value. At such discontinuities there is an inherent susceptibility to corrosion because of the galvanic relationship that necessarily exists between A/, and. Corrosion resistance may, however, sometimes be improved by sealing (cf. anodising) or by chromate passivation. 

Properties of deposits Deposits can be produced that are adherent, coherent and finely crystalline. Addition agents, e.g. organic sulphonamides can improve the deposit structure so that thick coatings can be produced free of nodules and blisters. The production of very smooth thick deposits of copper has been reported Thin deposits tend to reproduce the substrate topography, but some cases of levelling have been reported. The brightness tends to fall with increasing thickness. 

Properties of deposits Deposits are often more adherent, coherent and temperature-stable than those produced by alternative coating methods. Adhesion can be adversely affected by spurious reactions between the metal-gas and impurities in (e.g. as observed during the deposition of molybdenum on steel ) and also where the thermal coefficients of expansion of A/, and differ widely. The purity of reactants can affect that of A/,. crystal size is reduced by raising the reactant concentrations, or by lowering the plating temperature. 

Properties of deposits These are usually adherent and coherent. A/, is pure provided that all adverse chemically reactive gases are removed prior to sputtering nitrogen, for example, can form a nitride with copper, and oxygen can form oxides with most metals. 

Deposits from Watts-type solutions Most coatings of nickel for engineering applications are electro deposited from a Watts-type bath Typical mechanical properties of deposits from Watts and sulphamate solutions are compared with those of wrought nickel in Table 13.15. 

The coevolution of H2 gas in electroless deposition processes is a phenomenon that needs to be understood not only to elucidate the mechanism of deposition, but also since it impacts the properties of deposits by H inclusion. Van den Meerakker [51] first proposed a correlation between simultaneous hydrogen evolution in electroless deposition and the heat of adsorption of hydrogen. In this useful endeavor, however, he has been criticized for erroneously calculating the heats of adsorption of H at Cu by Gottesfeld et al. [52], and Group I (or SP type) metals in general by Bindra and Tweedie [53]. 

Structure and properties of deposits. These can be understood and interpreted on the basis of a variety of surface and bulk analytic techniques and methods that reveal electrical, magnetic, and physical properties of metals and alloys. 

The properties of deposits may be controlled by changing the kinetics of the deposition and the mechanism of crystallization. One way to achieve this is by complexing the depositing ions, as stated above. 

Chapters 10 and 11). Current distribution during deposition and both in situ and ex situ deposit characterization are the focus of Chapters 12-14. Electronic design (mathematical modeling) is the subject of Chapter 15, followed by the issues of structure, properties of deposits, multilayers, and interdiffusion (Chapters 16-18). 

In summary, the importance of ion-induced secondary-electron emission in plasma environments is demonstrated by, among other things, the fact that it produces a substantial fraction of the ions, generates significant heating of surrounding surfaces, and modifies the properties of deposited films. 

Studies of the formation, chemical composition, and properties of deposits have shown that they consist of partially oxidized organic material, including more or less nitrogen, sulfur, and phosphorus. Compounds of iron, silicon, calcium, and other metals are present in small quantity, together with substantial amounts of lead oxides, sulfates, and halides from combustion of the antiknock fluid. The effects of these deposits are both physical and chemical in nature they may physically interfere with lubrication, heat transfer, gas flow, operation of valves and spark plugs chemically, they may bring about corrosion and oxidation. 

To understand the above peculiarities of the electrocatalytic activity of metal nanophase in dark oxidation processes on the Ti02 electrodes, one should take into account the differences in the inherent electrocatalytic properties of deposited metals, on the one hand, and the data on the electronic states formed by the nanoparticles of these metals in a band gap of Ti02 electrode, on the other hand. A peculiar shape of i,V-curves obtained for... 

Thus the key parameters influencing the corrosion rate under deposits will be the deposit porosity, which determines the available surface area of material for corrosion, and the deposit tortuosity, which along with porosity will modify the fluxes of diffusing species within pores. Readers interested in a more extensive discussion are referred to other sources (17). Here we concentrate on a brief discussion of electrochemical methods of investigating the properties of deposits as a basis for eventual modeling. 

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