Temperature adsorbed layer thickness

Table I. Adsorbed Layer Thickness of Soluble Calf Skin Collagen on Glass as a Function of pH and Temperature, (thicknesses a7.7°C and a15°C are given in A)...

Fig. 4 Thickness of the adsorbed /i-propanol layer measured with QCM as a function of n-propanol partial pressure. It should be noted that the QCM measures the thickness on a gold surface. The 100% saturation data point contains large error because a slight fluctuation in the substrate temperature causes a large change in the condensed layer thickness. The saturation vapor pressure on n-propanol is 21.2 Torr at room temperature. The inset shows the adsorbed layer thickness of different alcohols at partial pressures 90 10% to the saturation. (View this art in color at www.dekker.com.)...

Fundamental investigation of the system at the molecular level. This requires investigations of the structure of the solid/liquid interface, namely the structure of the electrical double layer (for charge-stabiUsed suspensions), adsorption of surfactants, polymers and polyelectrolytes and conformation of the adsorbed layers (e.g., the adsorbed layer thickness). It is important to know how each of these parameters changes with the conditions, such as temperature, solvency of the medium for the adsorbed layers, and the effect of addition of electrolytes. 

Other important factors include cation type (K, Na, Ca. ..), clay specie charge deficiency, temperature, and so on. For example, increased kinetic energy at high temperatures overcomes bonding forces and reduces adsorbed layer thickness, leading to additional shale compaction under high T (thermal consolidation). 

Cosgrove et al. (1990) used small-angle neutron scattering on a polystyrene latex in water to obtain the adsorbed layer thickness of polyethylene oxide at three different temperatures. At higher temperatures a greater adsorbed amount was observed, which was consistent with water becoming a poorer solvent for the polyethylene oxide, but in all cases the layer thickness was about 20-30 A, an order of magnitude less than the hydrodynamic layer thickness. Neutron... 

Column — 67 m X 0.33 mm, adsorbent — molecuiar sieves 5A, adsorbent layer thickness — 30 urn, temperature — 22.3 °C, carrier gas — hydrogen (1.4 bar), thermal conductivity detector. 

As mentioned above, the contribution from the van der Waals attraction at separations corresponding to twice the adsorbed layer thickness is insignificant and, therefore, Es Gs- Thus, r jcan be theoretically calculated from a knowledge of G5 and application of equation (6). Indeed, Neville and Hunter [15] attempted to interpret their versus temperature plots for sterically stabilised dispersions of PMMA particles in the presence of MgS04, using the above simple theory. However, in order to calculate Gs under flocculating conditions, it is necessary to know... 

The systems flocculate below the 0-temperature of the free molecules (Fig. 9.15), the complex nature of the adsorption of the molecule at the surface may be one way to explain this behaviour. The molecules are highly folded at the air-water interface and also are likely to be so at a solid interface [36,37]. An estimate of the adsorbed layer thickness of poloxamers and nonyl phenyl... 

With this electric potential Poisson equation (A

el = net charge density) to eventually obtain the concentration of electrons at the film surface (A ). It further follows that Ne(A ) varies with the film layer thickness as A -2. If we now assume that the (catalyzed) rate of dissociation of the adsorbed X2 molecules is proportional to the surface concentration of electrons, and that this dissociation process is rate determining, a cubic rate law for the film growth can be expected (A — At 2 At - t in). In fact, during the oxidation of Ni at temperatures between 250 and 400 °C, an approximately cubic rate law has been experimentally observed. We emphasize, however, that the observed cubic oxidation rate does not prove the validity of the proposed reaction mechanism. Different models and assumptions concerning the atomic reaction mechanism may lead to the same or similar dependences of the growth rate on thickness. 

Before 1916, adsorption theories postulated either a condensed liquid film or a compressed gaseous layer which decreases in density as the distance from the surface increases. Langmuir (1916) was of the opinion that, because of the rapidity with which intermolecular forces fall off with distance, adsorbed layers are not likely to be more than one molecular layer in thickness. This view is generally accepted for chemisorption and for physical adsorption at low pressures and moderately high temperatures. 

Here we discuss the application of low energy photoelectron transmission spectroscopy (LEPS) as a means for investigating the electronic properties of OOTF. In a typical experiment photoelectrons are ejected from the conductive substrate and after being transmitted through the adsorbed layer, the energy (and or angle) dependent electrons flux is measured as a function of incident photon energy, molecular film thickness, adsorbate and substrate types and temperature. 

Table 43—Adsorption Capacities of Different Soils and Vapors and the Thickness of Adsorbed Layer. (Temperature 28 Deg C)...

In order to apply the above procedure to determine the conditions of phase separation, we have chosen the system of polyisobutene-stabilized silica particles with polystyrene as the free polymer dissolved in cyclohexane. The system temperature is chosen to be the 8 temperature for the polystyrene-cyclohexane system (34.5°C), corresponding to the experimental conditions of deHek and Vrij (1). The pertinent parameters required for the calculation of the contribution of the adsorbed layers to the total interaction potential are a = 48 nm, u, =0.18 nm3, 5 = 5 nm, Xi = 0.47(32), X2 = 0.10(32), v = 0.10, and up = 2.36 nm3. It can be seen from Fig. 2 that these forces are repulsive, with very large positive values for the potential energy at small distances of separation and falling off to zero at separation distances of the order of 25, where 6 is the thickness of the adsorbed layer. At the distance of separation 5, the expressions for the interpenetration domain and the interpenetration plus compression domain give the same value for the free energy, indicating a continuous transition from one domain to the other. 

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