Thickness deposited

Mineral matter content or ash yield varies widely, from <6% in thick deposits as found in AustraUa and Germany, to >40% in deposits in Turkey. 

On-site inspection of regions near the emergency service water intake structures revealed loss of up to 40% of the nominal pipe-wall thickness. Deposits were dried, ignited, and analyzed. A 1% solution of dried ash had... 

Pt electrodeposits may also be produced from molten salt electrolytes. Such a high-temperature process has the advantage that the deposits are diffusion bonded to the titanium substrate and thus have good adhesion, and, if necessary, thick deposits can be produced. However, they have the disadvantage that because of the complexity of the process there is a limitation on the size and shape of the object to be plated, and the resultant deposits are softer and less wear resistant than those from aqueous solutions... 

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. 

Deposits from all-chloride solution Nickel deposits from a solution of nickel chloride and boric acid are harder, stronger and have a finer grain size than deposits from Watts solution. Lower tank voltage is required for a given current density and the deposit is more uniformly distributed over a cathode of complex shape than in Watts solution, but the deposits are dark coloured and have such high, tensile, internal stress that spontaneous cracking may occur in thick deposits. There is therefore little industrial use of all-chloride solutions. 

In addition, the extreme hardness of the metal, its low coefficient of friction and its non-galling property, combined with its corrosion resistance, make it particularly valuable as a coating where resistance to wear and abrasion are important. Thick deposits applied for this purpose are referred to as hard chromium to distinguish them from the thin decorative deposits. 

The voltage used is 4-8 V, current density 9-22 A/dm, and temperature 38-43°C. Higher current densities, up to 55 A/dm, are used for thick deposits. A considerable amount of heat is generated during electrodeposition and provision must be made for cooling of the electrolyte during operation. 

More often than not, a deposited structure will include two and sometimes all three types. This usually happens in thick deposits where a uniform structure is more difficult to obtain. 

Fig. 3.6 XRD patterns (CuKa source) of equally thick deposits prepared on Ti at-1.2 V/SSEfromaO.5 x 10-3 M Se02, 0.2 M ZnS04, pH 2.5 solution at various temperatures (25-85 °C). Increase of bath temperature promotes the formation of zinc blende ZnSe crystallites, exhibiting a random orientation. The semimetallic, hexagonal phase of Se unavoidably forms together with the selenide compound. (With kind permission from Springer Science+Business Media [105])...

Electroless CoNiMnP and CoNiP were examined as underlayers for electroless CoP by Matsubara et al. [82], The CoNiMnP has a c-axis orientation normal to the film plane, whereas the CoMnP has a low degree of orientation. The CoP was found to deposit with a microstructure resembling that of the underlayer. Very thick deposits (> 0.5 fim) resume the intrinsic structure of CoP (with a low degree of PO). These composite structures have been tested as vertical recording media. 

Judge et al. [78] examined other magnetic properties of CoP. The saturation moments crs were 100 and 116 emu/g for deposits from solutions A and B, respectively. Although the P content of the deposits varied with pH, the as values were essentially independent of pH. The squareness ratio of the M-H loop showed no significant dependence on any quantity other than film thickness it ranged from 0.5 for thin films to 0.8 for thick deposits. 

The term monolayer (ML) must be defined clearly. In the work presented here, two definitions are used for surface studies, one ML indicates one adsorbate for each surface atom. For studies of compound formation, a monolayer is a slice of the compound s crystal structure, composed of one atomic layer of each of the constituent atoms. This does not necessarily mean a one unit-cell thick deposit is formed, as most compounds have larger unit cells from the point of view of crystallography, dependent on the orientation (Figure 8). 

Until quite recently the very initial stages of metal deposition were difficult to characterize in detail by structure- and morphology-sensitive techniques. As a consequence and for practical purposes - multilayers were more useful for applications than monolayers - the main interest was focussed onto thick deposits. Optical and electron microscopy, ellipsometry and specular or diffuse reflectance spectroscopy were the classic tools, by which the emerging shape of the deposit was monitored [4-7],... 

Figure 1. Photocurrent-photovoltage characteristics of the cell n-Si (Pt silicide coated)/1.0 M FeClg, 0.1 M FeCU, 1 M HCl/Pt at 65 nW/cm2 illumination. Pt thickness deposited 40 A and annealing temperature 400 °C at 10 6 torr for 10 min. Key a, before long-term stability test and b, after long-term stability test.

Fig. 4 X-ray photoelectron spectra of Alq3 core levels before and after 2, 4, 6, 12, and 24 A thick deposition of Co. Taken from [35] with permission...

Films (between 0.4 and 2.5 p,m thick) deposited from selenosulphate solution were characterized by optical spectroscopy and (photo)conductivity [63]. 

---