Deposit growth dynamics

For each experiment, a new sample of the same membrane was used and the initial permeability was measured with pure water. Results reveal a good reproducibility concerning the mean deposit thickness value and the deposit growth dynamics with regard to the quantity of filtrated matter. The maximum percentage deviation of the data for the three replication runs from the average value is 8%, which is reasonable. 

These parameters should not therefore be interpreted as constant, intrinsic physical properties of the soot cake, but rather as dynamic properties that depend on the deposit growth mechanism and its history. 

Several studies have recently appeared which combine UPD and SHG on single crystal Ag, Cu (Section 5.2.3) and Au (Section 5.3.3). Ideally, one would like to be able to characterize the physical structure, the electronic properties and the growth dynamics of the interfacial region by SHG as deposition occurs. On the more fundamental side, one would like to gain further insight into the nonlinear polarizability at metal surfaces by taking advantage of the unique alterations in the surface properties that can be done easily by UPD. All of these issues have been addressed in the studies described below. 

Because of its sensitivity to surface features and the gentleness of its interaction with the surface, HAS is an ideal probe for studies of interfaces, including the structures formed by adsorbate deposition, the dynamics of the interactions of adsorbates with substrates, and the dynamics of the formation of overlayers and films. In the Florida State University (FSU) laboratory we have focused on ionic insulator growth and more recently on organic films. 

The comparison between measured and calculated values shows good agreement. The measured order of magnitude and cake growth dynamics seem to be correct. Nonetheless, the evolution of the measured thickness with the deposited mass is nonlinear. This is due to the modification of the deposit structure with time which is not taken into account in the model. The limitation of the model is... 

SECM was employed not only to induce the deposition of Ag particles at the ITIES but also to monitor their nucleation and growth dynamics at the nanoscale. In this approach, a 25 pm-diameter Ag tip was oxidized to generate Ag , which was reduced by decamethylferrocene at the DCE/ water interface (Fig. 16a). The tip current based on Ag oxidation depends on the rate of Ag" reduction at the ITIES, thereby enabling the kinetic study of Ag deposition. The phase boundary potential of the macroscopic ITIES was controlled by changing the aqueous and organic concentrations of a common ion, CIO4, to enable the modulation of the driving force. 

Chemical vapor deposition processes are complex. Chemical thermodynamics, mass transfer, reaction kinetics and crystal growth all play important roles. Equilibrium thermodynamic analysis is the first step in understanding any CVD process. Thermodynamic calculations are useful in predicting limiting deposition rates and condensed phases in the systems which can deposit under the limiting equilibrium state. These calculations are made for CVD of titanium - - and tantalum diborides, but in dynamic CVD systems equilibrium is rarely achieved and kinetic factors often govern the deposition rate behavior. 

As has been shown above, oscillatory electrodeposition is interesting from the point of view of the production of micro- and nanostructured materials. However, in situ observation of the dynamic change of the deposits had been limited to the micrometer scale by use of an optical microscope. Inspections on the nanometer scale were achieved only by ex situ experiments. Thus, information vdth regard to dynamic nanostructural changes of deposits in the course of the oscillatory growth was insufHcient, although it is very important to understand how the macroscopic ordered structures are formed with their molecular- or nano-components in a self-organized manner. 

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