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Rapid and accurate determination of the surface area of three kaolinite clay standards, taking into account the complex microtopography of the particles, was achieved using atomic force microscopy images and computerized image analysis. All surface areas were determined to within 3%. Edge surface area is 18.2-30.0% of the total surface area depending on the particular kaolinite standard. Specific surface areas agree to within 4% of published values determined by the BET method. The approach can be applied to clay and nanoparticle samples too small in quantity for BET analysis, since it requires ~11 orders of magnitude less material.

The electronic structure and energies of Au atoms adsorbed on an atomic cluster of kaolinite were calculated using the self-consistent-field Discrete Variational (DV) method. A hexagonal ring of Si[O.sub.4] tetrahedra and three Al[O.sub.2][(OH).sub.4] octahedra, comprising 38 atoms, was used to model the kaolinite crystal flake. An Au atom was used to model the submicrometer Au. Calculations were performed with Au atoms adsorbed at different sites. The systems with lower total energy are those with Au adsorbed on the edge surfaces. The adsorption of Au atoms on the edges is more stable than Au atoms adsorbed on the basal plane. Bond order calculations suggest that significant shifting of atomic charge and overlap of electron clouds between Au and the surface atoms of kaolinite takes place in the systems with Au adsorbed on the edges, especially at sites near Al octahedra.

The theoretical infrared spectrum of kaolinite [A[l.sub.2]S[i.sub.2][O.sub.5][(OH).sub.4], triclinic] was computed using ab initio quantum mechanical calculations. Calculations were performed using the Density Functional Theory and the generalized gradient approximation. The low-frequency dielectric tensor of kaolinite was determined as a function of the light frequency using linear response theory. The IR spectrum was then calculated using a model that takes into account the shape and size of kaolinite particles. A remarkable agreement was obtained between theory and experiment, especially on the position of the stretching bands of OH groups. This agreement provides a firm basis for the interpretation of the IR spectrum of kaolinite in terms of structural parameters.

Intercalation of an ordered kaolinite with potassium acetate (KC[H.sub.3]COO) under a pressure of 20 bars and 220 [degrees] C, induced new Raman bands at 3590, 3603, and 3609 [cm.sup.-l] in addition to the normal kaolinite bands. These bands are attributed to the inner surface hydroxyls hydrogen bonded to the acetate. It is proposed that the intercalation under 20 bars pressure at 220 [degrees] C caused the differentiation of the inner surface hydroxyl groups, resulting in the appearance of these additional bands. Diffuse reflectance infrared spectra of the potassium acetate intercalated kaolinite that was formed at 20 bars and at 220 [degrees] C showed new bands at 3595 and 3605 [cm.sup.-1]. Upon formation of the intercalate at 2 bars and at 120 [degrees] C additional infrared (IR) bands were found at 3592, 3600, and 3606 [cm.sup.-1]. These IR bands correspond well with the observed Raman spectra. It is proposed that the effect of intercalation of the highly ordered kaolinite under pressure caused the kaolinite to become disordered and this disordering was dependent on the temperature of intercalation. It is suggested that when pressure is applied to the kaolinite crystal in the presence of an intercalating agent, the hydrogen bonds between adjacent layers are broken to create space for the intercalating agent between the layers. A direct result is that the order of the kaolinite crystals shows a decrease resulting in more defect structures. This is evidenced by the additional spectroscopic bands in both the Raman and IR spectra.

Intercalation of an ordered kaolinite with potassium acetate (KC[H.sub.3]COO) under a pressure of 20 bars and 220 [degrees] C, induced new Raman bands at 3590, 3603, and 3609 [cm.sup.-l] in addition to the normal kaolinite bands. These bands are attributed to the inner surface hydroxyls hydrogen bonded to the acetate. It is proposed that the intercalation under 20 bars pressure at 220 [degrees] C caused the differentiation of the inner surface hydroxyl groups, resulting in the appearance of these additional bands. Diffuse reflectance infrared spectra of the potassium acetate intercalated kaolinite that was formed at 20 bars and at 220 [degrees] C showed new bands at 3595 and 3605 [cm.sup.-1]. Upon formation of the intercalate at 2 bars and at 120 [degrees] C additional infrared (IR) bands were found at 3592, 3600, and 3606 [cm.sup.-1]. These IR bands correspond well with the observed Raman spectra. It is proposed that the effect of intercalation of the highly ordered kaolinite under pressure caused the kaolinite to become disordered and this disordering was dependent on the temperature of intercalation. It is suggested that when pressure is applied to the kaolinite crystal in the presence of an intercalating agent, the hydrogen bonds between adjacent layers are broken to create space for the intercalating agent between the layers. A direct result is that the order of the kaolinite crystals shows a decrease resulting in more defect structures. This is evidenced by the additional spectroscopic bands in both the Raman and IR spectra.

The presence of multiphase region under shock effects near 30 giga Pascals is revealed by the XRD, TEM, thermoponderal and infrared spectra of aluminous smectite and postshock kaolinite. A fraction of the crystalline water of the clays is transferred to a new glass phase. Under certain conditions, some of the completely nonalkali composition are capable of forming glass, which does not devitrify when subjected to postshock conditions. The thermal stability of clays at atmospheric and low pressure conditions causes the continuous stability of shock events.

Six kaolinite [[Al.sub.2][Si.sub.2][O.sub.5][(OH).sub.4]] samples were synthesized under different conditions of temperature, pressure, and pH from two different starting materials. Chemical composition and properties of the samples were characterized using classical methods (electron microprobe, atomic absorption spectrometry, X-ray diffraction, differential and thermal analyses, and Fourier transform infrared spectrometry). All synthetic kaolinite samples contained various amounts of a boehmite impurity. The defect density was different for each kaolinite, ranging from high to low. The enthalpy of formation of these kaolinites at 25 [degrees] C was investigated by drop solution calorimetry into molten lead borate at 700 [degrees] C. All data were corrected for impurities. Whatever the synthesis conditions and the kaolinite properties, the enthalpy of kaolinite dissolution into molten lead borate at 700 [degrees] C and the standard enthalpy of kaolinite formation from the oxides and from the elements at 25 [degrees] C are constant: 372.3 [+ or -] 1.0 kJ/mol, -46.6 [+ or -] 2.6 kJ/mol, and -4115.3 [+ or -] 4.1 kJ/mol respectively. Using entropy data from the literature, the standard Gibbs free energy of kaolinite formation from the elements at 25 [degrees] C is -3793.9 [+ or -] 4.1 kJ/mol. This value is in excellent agreement with most of the literature data obtained for natural kaolinites. Furthermore, the standard Gibbs free energy of kaolinite formation at 25 [degrees] C and 1 atm is very close to that obtained using the same method for the San Juanito dickite, which is commonly used as a standard mineral, the value for kaolinite being slightly more negative than the value for dickite. This trend is also true for all the temperature and pressure range of kaolin minerals occurrences. Thus, dickite is a metastable phase relative to kaolinite, and kaolinite seems to be thermodynamically more stable than dickite, as already proposed by DeLigny and Navrotsky (1999) and Anovitz et al. (1991). The natural occurrence of dickite must result from specific reaction paths and be controlled by kinetic factors.

Solid products from hydrothermal experiments conducted at 250 [degrees] C and [P.sub.v,soln] were characterized by powder X-ray diffraction (XRD) and ATEM/HRTEM. Experiments were conducted with muscovite, kaolinite, and quartz or amorphous silica in 2M KC1 solutions for 43 to 176 d. Post-experiment solution compositions lie either within the illite(0.88 K) stability field or on the illite(0.88 K)-kaolinite or illite(0.88 K)-diaspore univariant boundaries in log [Mathematical Expression Omitted] vs. log [a.sub.[H.sub.4]Si[O.sub.4]] activity space. Transmission electron microscopy (TEM) observations of muscovite grain edges reveal the neoformation of illite crystals with a range of compositions (ATEM) from 0.31 to 0.89 K/[O.sub.10][(OH).sub.2]. The range of K-contents appears to narrow toward 0.88 K/[O.sub.10][(OH).sub.2] with increased experiment duration. HRTEM suggests the presence of 2 to 11 layer fundamental particles composed of illitic layers with 10 A periodicity. Fundamental particle thicknesses increase toward an average of 8 layers/particle with increased experiment duration. In the longer duration experiments, fundamental particle thicknesses were normally distributed about thicknesses of 4 and 8 layers, whereas fundamental particles with thicknesses [less than] 4 layers were common in a shorter duration experiment. The compositions and structure of the illites are consistent with the multiphase model, which states that the smectite-to-illite transition occurs through the step-wise formation of solubility-controlling phases consisting of fundamental particles with thicknesses of 1, 2, 4, and [greater than or equal to]8 layers. The increase in K-content and fundamental particle thickness with the extent of reaction suggests that the illite crystals underwent a prograde reaction culminating in the formation of end-member illite [0.88 K/[O.sub.10][(OH).sub.2]]. This reaction, in conjunction with the previously observed, retrograde reaction from muscovite to end-member illite, demonstrates the stability of end-member illite in the system [K.sub.2]O-[Al.sub.2][O.sub.3]-Si[O.sub.2]-[H.sub.2]O at 250 [degrees] C.

Solid products from hydrothermal experiments conducted at 250 [degrees] C and [P.sub.v,soln] were characterized by powder X-ray diffraction (XRD) and ATEM/HRTEM. Experiments were conducted with muscovite, kaolinite, and quartz or amorphous silica in 2M KC1 solutions for 43 to 176 d. Post-experiment solution compositions lie either within the illite(0.88 K) stability field or on the illite(0.88 K)-kaolinite or illite(0.88 K)-diaspore univariant boundaries in log [Mathematical Expression Omitted] vs. log [a.sub.[H.sub.4]Si[O.sub.4]] activity space. Transmission electron microscopy (TEM) observations of muscovite grain edges reveal the neoformation of illite crystals with a range of compositions (ATEM) from 0.31 to 0.89 K/[O.sub.10][(OH).sub.2]. The range of K-contents appears to narrow toward 0.88 K/[O.sub.10][(OH).sub.2] with increased experiment duration. HRTEM suggests the presence of 2 to 11 layer fundamental particles composed of illitic layers with 10 A periodicity. Fundamental particle thicknesses increase toward an average of 8 layers/particle with increased experiment duration. In the longer duration experiments, fundamental particle thicknesses were normally distributed about thicknesses of 4 and 8 layers, whereas fundamental particles with thicknesses [less than] 4 layers were common in a shorter duration experiment. The compositions and structure of the illites are consistent with the multiphase model, which states that the smectite-to-illite transition occurs through the step-wise formation of solubility-controlling phases consisting of fundamental particles with thicknesses of 1, 2, 4, and [greater than or equal to]8 layers. The increase in K-content and fundamental particle thickness with the extent of reaction suggests that the illite crystals underwent a prograde reaction culminating in the formation of end-member illite [0.88 K/[O.sub.10][(OH).sub.2]]. This reaction, in conjunction with the previously observed, retrograde reaction from muscovite to end-member illite, demonstrates the stability of end-member illite in the system [K.sub.2]O-[Al.sub.2][O.sub.3]-Si[O.sub.2]-[H.sub.2]O at 250 [degrees] C.