Surface thermodynamic properties

Tab. 8.5 Apparent surface thermodynamic properties for goethite and hematite at 298.15K (see Diakonov et al. 1994)...

Using the same procedure, spherical nanosize particles of hematite were coated with yttrium basic carbonate and showed that various surface thermodynamic properties of these systems were essentially those of yttria (37). 

To calculate the surface thermodynamic properties from equations (12.33) to (12.41), we must know how 7 changes with T. Equation (12.42) is a semi-empirical equation that has been used to relate 7 and T. It is given by... 

Inverse gas chromatography (IGC) is another technique that can be used to measure the specific surface area of a particulate material, as well as to measure a number of surface thermodynamic properties of powders. Such instrumentation operates on a different principle than traditional nitrogen/krypton adsorption using the BET isotherm. 

As stated previously, IGC can also be used to measure the specific surface area of a given powder. The adsorbate gas is not restricted to N2 and Kr rather, the same probes that are used to characterize the surface thermodynamic properties of the powder can be used as probe to measure its specific surface area. Table 13.2 contains a comparison of specific surface area measurements via traditional N2/Kr adsorption vs IGC. 

Giese R. F., Jr. and van Oss C. J. (1993) The surface thermodynamic properties of silicates and their interactions with biological materials. In Health Effects of Mineral Dusts, Rev. Min. 28 (eds. G. D. Guthrie and B. T. Mossman). Mineralogical Society of America, Washington, DC, pp. 327-346. 

Colloidal dispersions and other related systems are present in many applications, e.g., in paints and coatings and detergents. Here, phase equilibrium and surface phenomena are equally important. A unified representation of such phenomena, e.g., of adhesion phenomena and liquid-liquid equilibria with the same model/concepts is of interest. Thermodynamic models can be used to calculate certain surface properties such as surface tension. hi addition, properties such as the solubility parameters can be equally well employed for bulk and surface thermodynamic properties. ... 

SURFACE THERMODYNAMIC PROPERTIES OF ALCOHOLS AND RELATED COMPOUNDS. 

SURFACE THERMODYNAMIC PROPERTIES OF N-LONG-CHAIN ALCOHOLS, ALKOXY ETHANOLS, PROPANOLS, AND BUTANOLS. 

In summary, IGC is a simple, relatively inexpensive approach using standard GC instrumentation to obtain the surface thermodynamic properties of solids. The theoretical interpretation of the experimental resnlts is now well established, and the deduction of acid-base properties of materials can now be regarded as being routine. IGC provides a complementary method to the nse of wetting Uqnids, insomuch as it probes the microscopic properties of the solid surface, (as the probe molecules are invariably small and in the gaseous phase, and are at infinite dilntion, i.e. there is no interaction between adjacent probe molecules on the solid snrface or in the gas phase), while the use of liquids in techniques such as dynamic contact angle analysis probes the macroscopic properties. 

Simultaneous representation of bulk and surface thermodynamic properties ... 

These are the materials which humans frequently encotmter. If one restricts the discussion, as in this book, to those common materials which occur either naturally or as the result of manufacturing processes as colloids, the list becomes very much shorter. Even with this shorter list, there are relatively few minerals whose surface thermodynamic properties have been determined. This reflects the fact that the underlying theory of surface thermodynamic components is relatively new and there are presently few researchers active in studying the properties of minerals as opposed to polymers and biological materials, for example. 

In this section, the minerals whose surface thermodynamic properties have been measured are described in terms of their structure, diemistry and, where possible, the atomic arrangement of the external surfaces of finely divided particles. Since this chapter is not meant to be a detailed description of the structures of these materials, much of the normal information such as unit cell p irameters, space group and atomic positional and thermal parameters are not listed. These data are easily located in the literature using the references provided. Good general accounts of these minerals are provided by Klein and Hurlbut (1993) and, in more detail, by Putnis (1992). 

Organic material can be positioned on a clay mineral surface in two ways either by the excheinge of the native inorganic cations by an organic cation (e.g., a quaternary ammonium cation) or by surface adsorption of a neutral organic molecule (e.g., an amine) on the external sinface of the clay peirticles. Tables 9.2 and 9.3 illustrate the changes in surface thermodynamic properties as the coverage of the clay surfaces varies. It is clear that modest amounts... 

A generalized density gradient theory of interfaces has been combined with a compressible lattice theory of polymers. This yields a unified theory of bulk and surface thermodynamic properties. A unique feature of this theory is that it is parameterless. The only parameters required to calculate a surface tension are obtained from pure component thermodynamic properties. Since the theory is a mean field theory, it is only applicable to non-polar and slightly polar liquids. For such systems, surface tensions can be accurately calculated. 

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