Surface phase diagram of water

The critical temperatures of the first layering transitions are shown by squares in Fig. 36. With strengthening water-wall interaction, the critical temperature of layering transition approaches as expected. It is important that the critical temperatures of layering transition on the surfaces of various hydrophilicity and 2D critical temperature are noticeably above the bulk freezing temperature Therefore, we may expect the effect of 2D critical point on various properties of hydration water at ambient temperatures. 

---

With increasing humidity, growth of the amount of water adsorbed may occur in a continuous way or via the surface phase transitions, such as layering and prewetting, described in Section 2.1. Obviously, the presence of water clusters, water layer(s), or macroscopic water film on the surface essentially modifies the system properties. To predict water behavior near various surfaces, it is, therefore, important to analyze in a systematic way all possible scenarios of water adsorption and to relate them with the thermodynamic conditions and with the properties of a surface. Analysis of the surface phase transitions of water at hydrophilic surfaces (this section) and at hydrophobic surfaces (Section 2.3) will be finalized by constructing the surface phase diagram of water in Section 2.4. 

Figure 35 Surface phase diagram of water. Solid lines indicate drying and wetting transitions. Horizontal dashed lines indicate liquid-vapor critical temperature Tc and freezing temperature respectively. Insets show arrangement of molecules in the coexisting phases of water in cylindrical pores (i p = 25 A, r = 300K) to the left (C/o =-3.08 kcal/mol) and to the right Uo = -0.77 kcal/mol) from the inclined line of the wetting transitions.

Figure 36 Surface phase diagram of water. Solid inclined line indicates wetting transitions. Horizontal lines indicate Uquid-vapor critical temperature freezing temperature and critical temperature of 2D water. Closed and open circles indicate the critical temperatures of the prewetting transitions and the temperatures of the vapor-film-hquid triple points, respectively. Qosed squares indicate the critical temperatures of the first layering transitions, which approach when Uo -oo. Asterisks indicate the critical temperatures of the second layering transitions.

Fig. 12-1. Surface temperatures expected on the three planets Venus, Earth, and Mars as a function of the water vapor pressure. An increase in the vapor pressure increases the retention of infrared radiation in the atmosphere, raising the temperature via the greenhouse effect. Overlaid is the phase diagram of water. On Earth and Mars the starting (radiation equilibrium) temperatures are low enough for water to condense out when the temperature intersects the condensation curve. On Venus, the temperature rises more rapidly and runs away. [Adapted from Walker (1977), originally modeled by Rasool and DeBergh (1970).]...

Koga, K., and Tanaka, H. 2005. J. Chem. Phys. Phase diagram of water between hydrophobie surfaces. 122 104711. 

Figure 6.2. Phase diagram of water/sodium dodecyl sulfate/manganese(II) dodecyl sulfate system. 5, mixed CMC surface. (Reproduced with permission of Academic Press.)...

Drastic changes in the phase diagram of water occur when the water-surface interaction weakens by just 1 kcal/mol (from —3.08 to... 

Another way of ensuring that a glass surface is free of water or hydroxyl groups is to cover it with a film of sodium. This method was used when the melting point phase diagram for the system isobutene + titanium tetrachloride was determined (Longworth, Plesch and Rutherford, 1959 Plesch, 1972), but it cannot be used on silane-treated glass as the sodium will not spread on the waxy surface. 

The enormous variety of possible surface reactions still reveals many open questions regarding exact reaction pathways, kinetics, and/or structural iirformation. The seemingly simple water formation reaction from H2 and O2 over a Pt-catalyst already shows many different reaction pathways. Regarding this reaction, we have performed periodic DFT calculations and thermodynamic considerations to evaluate the corresponding (a,7 ,A(zi)-surface phase diagram for Pt(lll) on contact with an aqueous electrolyte. Our work determined that below 0.95 V no stable and ordered oxygen overlayer forms, and that between 0.95 and 1.20 V the... 

In addition to giving information about the shape and internal structure of colloidal aggregates, SANS studies can also be used profitably to determine the thickness and conformation of polymer layers adsorbed onto the surface of colloidal particles such as latex nanoparticles, and in some special cases, the surface of emulsion droplets. ° In such studies, the particles on which the polymer is adsorbed must generally be very accurately contrast matched to the solvent so as to allow information to be obtained only about the adsorbed layer. SANS studies have also been recently used in combination with differential scanning calorimetry and visual inspection of the solutions, to draw up a (simplified) partial phase diagram of the aggregation behavior of a polymeric surfactant in water.t ... 

---