Equivalent monolayer

Some direct comparisons of the present model with the published results of Fleer and Scheutjens (13) are given in Figures 2 and 3. In the comparison of the adsorption isotherms, shown in Figure 2, the amount adsorbed is represented by the number of equivalent monolayers g (total number of segments in molecules bound to the surface) defined by... 

Fig. 5. The total and incremental amount, in equivalent monolayers, of volatile material desorbed from an untreated AU carbon fiber and a surface treated AS carbon fiber as a function of increasing temperature. From Drzal341...

The total coverage 0 = 2 0(z) may well exceed one (or even several) equivalent monolayers. For physisorbed layers of a homopol5nmer (as in fig. 3.18c), the treiin layer of segments in contact with the air gives the leading contribution to r, as we shall show below. However, for brushes (fig. 3.18d) the contribution of the entire layer must be considered we shall discuss brushes in subsec. 3.4j. 

Well-ordered AI2O3 films have been prepared using an A1 deposition rate of 0.5 MLE.min (equivalent monolayer, calibrated on an Mo(llO) substrate using AES and TPD), at a background O2 pressure of 7 x 10 Torr, and an Mo(llO) substrate temperature at 300 K [58]. Following deposition, the films were annealed to 1200 K in O2 to improve the film order. Figure 1 shows representative AES spectra of alumina films at two different thicknesses [58]. An AES spectrum of a 2.0-nm film has a predominant Al (LVV) transition at 45 eV and an O (KLL) transition at 500 eV. The absence of a peak at 68 eV, characteristic of Al°, indicates that the film is fully oxidized. Features attributable to the Mo(llO) substrate can be seen in the 100-250-eV region. The thickness of the oxide films was calculated from the attenuation of the AES intensity ratio of the Al (LVV) feature relative to the Mo(MNN) feature. 

Figure 20 The integrated TPD area (P2 state) plotted as a function of the Cu coverage in equivalent monolayers. The average sizes of the Cu clusters are also indicated. (From Ref. 58.)...

Figure 6.5 shows typical adsorption isotherms plotted as surface coverage (in equivalent monolayers) versus polymer volume fraction 0 in bulk solution (( was taken to vary between 0 and 10 which is the normal experimental range). The results in Figure 6.6 show the effect of increasing the chain length r and effect of solvency (athermal solvent with = 0 and theta solvent with = 0.5). The... 

The open circuit potential after the first scan, where approximately 20 equivalent monolayers gold are present on the surface, is linear with the concentration ratio with a slope of 59 mV per decade, and is close to the gold redox potential. This indicates that after gold deposition, the open circuit potential is determined by the equilibrium of the Au(CN)2 / Au couple. Note that the reaction is not expected to be reversible since the gold is only connected to the external circuit via the silicon wafer. 

Figure 5. Schematic diagram of the porphyrinic sensor for measurement of nickel (a), pH deperKlence of demetalation of polymeric (TMHPP)Ni" (b), Film thickness, 20 equivalent monolayers time, 60 s and Ni(ll)...

Plot B in Figure 3 shows the AFM force-distance curves obtained when a PEG 2 kDa covalently bound to the tip compresses against a freshly cleaved mica sample in the presence of 0.1 M KNO3. A small attractive force just prior to the linear portion of the force-distance plot is observed. This implies that the steric exclusion force at this position is weaker than the van der Waals attractive force. This is not unexpected, since such a small molecular weight PEG is bound to the surface. With a 2 kDa PEG polymer attached, the is 1.7 nm and the steric exclusion force should commence at about 4 nm (2.5 Rg). cS)mputer modelling by GOLIAD indicated that a force of 5.2 nN (5.7 minus 0.5 nN) can be expected at a 0.6 nm separation distance when one equivalent monolayer of PEG segments was present on the surface of the probe. Such a force is detectable by the AFM. One possibility why a repulsive force does not appear in this experiment is that a lesser amount of PEG 2 IdDa than one equivalent monolayer is bound to the surface. 

Results are often converted to an equivalent monolayer coverage for direct comparison with field emission gun scanning transmission electron microscopy (FEGSTEM) EDX measurements of grain boundary segregation. The calculation is straightforward for binary systems, but the complexity rapidly increases as the number of elements increases. The equivalent monolayer coverages (O) for P and C in Fe are summarised in Table 92 ... 

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