Metal deposition rate

Fig. 2. A plot of the absorbances of typical lines attributed to Vj, relative to that of a V resonance absorption as a function of the V metal deposition rate at constant Ar deposition rate (108).

Fig. 5. Correlation of the UV-visible spectra of Co atoms and Coj molecules isolated in Ar, Kr, and Xe matrices under identical conditions of temperature and gas and metal deposition rates (49, 154).

The additional reaction intermediates in the Ni-tetra(3-methylphenyl)-porphyrin network coupled with slower rates of metal deposition result in deeper penetration of the internal maxima and higher concentration of metals in the pellets center compared to Ni-etioporphyrin. Likewise, the selective enhancement in the metal deposition rates of Ni-T3MPP on the sulfided catalyst is apparent by the steeper profiles in Fig. 28 relative to the results in Fig. 27 on the oxide form of CoMo/A1203. ... 

The nature of the current density dependence of particle codeposition is the most disputed aspect in the mechanism of composite plating (Section IV). In the simplest case the particle deposition rate is not affected by the current density, either because of particle mass transfer limitations or a current density independent particle-electrode interaction. Since the metal deposition rate increases with current density, this results in a continuously decreasing particle composite content. In other cases the particle-electrode interaction has to be current density dependent. An unambiguous explanation for this dependence has not yet been found, but it is apparent that the metal deposition behavior is involved. 

Similar to Guglielmi s model the metal deposition rate Fwis defined as ... 

The TSM resonator was originally used in vacuo to measure metal deposition rates [1]. More recently, the TSM resonator has been shown to operate in contact with liquids [2,3], enabling its use as a solution-phase microbalance. The device is typically incorporated in an oscillator circuit, where the oscillation frequency tracks the crystal resonance and indicates mass accumulation on the device surface. This microbalance capability has facilitated a number of gas- and liquid-phase sensor applications that will be discussed in Chapter 5. 

The metal deposition rate from aqueous solutions can be expressed as a current density (A m-2 of electrode surface) as the rate is linked to the current density by Faraday s law (1). In modern copper electrorefining and electrowinning, the current density is 300-350 Am-2, while in zinc operations it is greater, 450-500Am-2 or more. According to Faraday s law, enormous amounts of electricity are needed for the tens or hundreds of kilotons of metal produced in a typical electrolysis plant per year. 

A reference vanadium deposition experiment is carried out in order to assess the influence of quinoline and HjS. Quinoline showed to decrease the rate of metal removal, the amount of vanadium deposited is lower as compared to the reference experiment. The shape of the vanadium deposition profiles is similar in both cases. A deposition maximum is observed in the centre of the pellet, indicating that the vanadium deposition process is not diffusion limited and that a sequential reaction mechanism applies for VO-TPP HDM. Low H2S partial pressure resulted in different vanadium deposition profiles as a function of the axial position in the reactor. At the inlet of the reactor, similar shaped profiles as the reference experiment were found, however, at the outlet of the reactor a shift towards M-shaped profiles was found indicating a diffusion limited vanadium deposition proeess. This shift in vanadium deposition profiles is explained by the build-up of the last intermediate resulting in a higher metal deposition rate. 

VO-TPiB. Apparently, in the last two trays the concentration of VO-TPiB becomes so high, that the metal deposition rate overrules the diffiision rate into the catalyst pellet which causes metal deposition in the outer shell. 

The vanadium deposition process showed profiles with deposition maxima in the centre of the pellet indicating the absence of diffusion limitations and supporting a sequential reaction mechanism for VO-TPP HDM. Quinoline addition showed to have an decreasing effect on the rate of metal removal and showed similar shaped deposition profiles. The low HjS partial pressure caused a change of the vanadium deposition profiles into M-shaped profiles due to the build-up of the last intermediate and an increasing metal deposition rate. 

A variety of consumption rate laws have been proposed. One of the simplest, and perhaps most intuitive, is that adsorbate consumption is proportional to coverage, 0y, and metal deposition rate, i, according to [139] ... 

In one limiting case the inhibiting molecule is immobilized upon adsorption and subsequently buried as an inclusion during metal deposition. In this instance the rate constant, fcino is simply related to the neighboring metal deposition rate to obtain [140] ... 

For dilute additive solutions, consumption can easily become limited by diffusion of the adsorbate to the interface. A particularly tractable situation occurs at the dilute limit of the Langmuir isotherm where C(- is proportional to the surface coverage, and in the limit of diffusion controlled adsorption CsoHd is directly proportional to the additive flux and thus the bulk electrolyte concentration. Such transport limited incorporation was reported in some radiotracer studies of thiourea incorporation in nickel and copper plating in the 1950-1960s [1-4, 17, 130, 131, 141-146], Consistently, a common observation was that the additive concentration in the solid was proportional to the additive concentration at the interface and inversely proportional to metal deposition rate, i, [1-4, 130, 131, 141, 142] such that ... 

The addition of inhibitors to Ni, Cu, Sn, Pb,. .. plating electrolytes results in a decrease in the metal deposition rate at fixed potential or, equivalently, an increase in electrode polarization for a fixed applied current density as indicated in Figure 2.10... 

In all simulations, interface motion is related to the metal deposition rate through the requirement that the time-derivative of the local surface position, S, namely the local growth velocity, v,... 

Tab. 11.2 Measurement of dust and metal deposition rates in children s homes in Germany, from two studies using the same sampling and analytical techniques (described in text)...

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