Deposition ratio

The exposure concentration was adjusted for intermittent exposure (6 hours/24 hours, 5 days/7 days). A regional deposition ratio of 0.9714 for the pulmonary region for particle size 2.5 pm and sigma 2.4 was used to extrapolate from particle deposition in rats to deposition in humans... 

Diameter (p.m) Cumulative deposition Ratio diffusion settling... 

The amount of amphiphile that can be deposited on a glass slide depends on several factors (2). The deposition ratio is defined as where... 

The actual deposition process can be visualised as taking place in the manner shown in Figure 4.1. Here it is supposed that, on the upward stroke, hydrophilic interaction is responsible for adhesion and that, on the downward stroke, hydrophobic interaction is responsible for adhesion. The deposition ratio is defined as the ratio of the area of film deposited to the change in area at the air/water interface corresponding to this deposition. If the deposition is very near unity, it is assumed that perfect deposition has taken place. If the deposition ratio is near unity for both upward and downward strokes, the material is said to be deposited in the Y mode. If this ratio is near unity on the up stroke and near zero on the down stroke, the deposition is said to be in the Z mode and the converse situation is said to lead to deposition in the X mode. A simplistic interpretation of Z and X deposition would lead one to suppose that such deposition would lead to a non-centrosymmetric structure. In some cases this is indeed true but, in many cases, there appears to be some kind of rearrangement after deposition so that apparent X or Z deposition leads to a structure similar to that which one would achieve with Y deposition and a structure of regular bilayers is produced. 

It is an unfortunate fact that, whereas many hundreds of materials have been used to form LB films, in the majority of cases no serious effort has been to characterise the film structure or even to show that a regular layer structure has been achieved. The example of amphiphilic porphyrins discussed above is sufficient to emphasise the need for proper characterisation. It will be recalled that mesoporphyrin IX dimethyl ester and the equivalent diol can, when complexed with a large variety of divalent metals, form excellent apparent Y layers with a deposition ratio very near unity on both up and down strokes. However, it is quite impossible to demonstrate the existence of a regular layer structure using X-ray diffraction techniques. Analogous situations involving two kinds of molecule will be discussed in Chapter S. 

In this support-film arrangement, the porphyrin rings were positioned next to the SnO surface. Coated slides were stored in separate glass containers in the dark before use. Deposition ratios were routinely measured and used as a criterion to assess the quality of the coatings. 

D. Delivery Systems, Deposition Ratio, and Regional Lung Deposition... 

Table 8 Comparisons of Country Emission deposition ratio...

Details of the CEE method applied here to Step I-B to recover and purify RMFP obtained from Step 1A were discussed elsewhere [7]. In principle, Pd (or Fc ) would accelerate electro-deposition of the other ions as a promoter (i.e., Pd, ,.,.,.) at the electrode surface or as a mediator in the bulk solution. As for a typical example of CEE of RMFP from simulated HLLW, the galvanostatic electrolysis resulted in the quantitative deposition, where metal ions with E >0.7V tended to deposit on the cathode, and the deposition ratio seemed to be proportional to the order of the redox potential Pd>Te>Se>Rh>Ru>Re. Molybdenum and Zr can be recovered as co-precipitation at H <1.5 mol/dm . 

The quantity and the quality of the deposited monolayer on a solid substrate is measured by a so-called transfer ratio or deposition ratio, T,... 

Figure 1.5.10 Schematic drawing of a Pockels trough used to form compact molecular monolayers on a water surface. The deposition takes place on the downward stroke if hydrophobic interaction is responsible for deposition (hydrophobic surface) and on the upward stroke if hydrophihc surface-monolayer interactions are more important. If the deposition area is equal to the loss of the monolayer on the air/water interface (deposition ratio equal to 1), it is assumed that perfect deposition has taken place. If the ratio is near unity in both upward and downward strokes, the material is deposited in the Y mode, which is the most stable multilayer structure (b). If the deposition ratio is near unity in the down stroke and zero on the up stroke, the deposition is in the X mode (a). The surface is hydrophobic and am-phiphiles are bound in the A orientation. The converse situation leads to Z-mode multilayers (c B orientation). X- and Z-types often rearrange to Y-type multilayers.

A simple way of assessing the effects of the equilibration processes on wet or dry deposition is to compare the predictions of the full models described above with those of the corresponding models, where the equilibration processes are neglected. To facilitate this comparison we define the deposition ratio at the time /, DR(t), as the ratio of the total species mass that has been deposited since t = 0 in gas and aerosol forms, when the equilibration processes are taken into account, to the same quantity when the equilibration processes have been neglected. Values of the deposition ratio close to unity mean that the equilibration processes do not affect significantly the deposition of species. Values of the deposition ratio larger than one correspond to deposition enhancement by the equilibration processes while values smaller than one represent deposition suppression. 

Using the above definition for the deposition ratio one obtains, for the two cases presented above. 

The deposition ratio is a function of time, and, due to the initial assumed equilibrium state in all the above three cases, DR(0) = 1. This can easily be shown because the mass transfer terms in all the differential equations vanish at / = 0 and the equations for both approaches to the deposition problem are the same. The behavior of DR as r -> oo depends on whether emissions of material are occurring. If no emissions of material enter the system it is clear that for both approaches all the initially present material will eventually be deposited on the ground and therefore DR(oo) = 1. The cases with vapor emissions present will be examined independently below. 

The first case discussed is for rapid mass transfer between the gas and aerosol phases, a — 1000. The deposition ratios are presented in Figure 19.8 as a function of and y. When no source of the organic species A is present (8 =0), and because the system starts from equilibrium, the gas-phase concentration of A cannot exceed its saturation value. Therefore in this case A does not condense at any time to the aerosol phase and the particles evaporate in an attempt to maintain equilibrium. This nonsymmetry in the system is depicted in Figure 19.8a, and for / > 1 (deposition velocity of the particles exceeds the deposition velocity of the vapor) the equilibration process does not significantly affect the deposition. The material in the aerosol phase is preferentially deposited... 

FIGURE 19.8 Deposition ratio DR (t ) (total deposition with equilibration processes over deposition without) as a function of the initial species distribution fi and the ratio of the deposition velocities y for rapid mass transfer (a = 1000) and two production/emission rates of A(g). (a) 5 = 0, no emission (b) 8 — 10, strong emission source. 

The main focus of this study was to assess the relationship between the horizontal and vertical deposition rates for these different deposition systems. Figure 15 is a plot of the horizontal/vertical deposition ratio as a function of the deposition temperature. At about 900°C this ratio becomes 1.0, whereas at 400°C the value is as high as 1.6. Variation and optimization of the growth conditions at each of the temperatures would tend to change the reported aspect ratio to some degree. However, the data clearly indicate the contouring efficiency of... 

Honig E.P. 1973. Langmuir-Blodgett deposition ratios, J. CoUoid Interface Sci., 45, 92-102. 

Our group initially reported that the average deposition ratio of 7(A) (down stroke) was about 0.5 to 0.7, and the average transfer ratio of 8(B) (up stroke) was about 0.9 to 1.5 (70). Recently, it was found that if the Langmuir films are replaced after only about 50% is consumed in the dipping process (compared to about 90% in the first case), transfer ratios were always between 0.95 and 1.0. Work is presently underway to characterize the optical properties of new bilayer films prepared with transfer ratios close to unity. 

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