Clay particles, characterization

Primary clay is also known as residual clay, indicating that they are either the in situ residue of one type of weathered rock or the transported residue of many types of rocks most primary clay deposits occur, however, in situ, at the location where the clay particles were formed. The clay is usually quite pure and colorless or white, but very small relative amounts of minerals mixed with the clay, such as quartz and/or iron oxides, may impart to it a yellow, brown, or green color. Primary clay is also characterized by the extreme fineness of its particles, which usually measure below 2 micrometers (0.002 mm) in diameter. The more than 20 different types of primary clay minerals can be distinguished by their chemical composition, which varies widely, and by their physical properties. Primary clays that have been used for making ceramic objects are listed in Table 55. 

By comparison with many other silicate minerals, isotope studies of natural clays are complicated by a number of special problems related to their small particle size and, hence, much larger specific surface area and the presence of interlayer water in certain clays. Surfaces of clays are characterized by 1 or 2 layers of adsorbed water. Savin and Epstein (1970a) demonstrated that adsorbed and interlayer water can exchange its isotopes with atmospheric water vapor in hours. Complete removal of interlayer water for analysis with the total absence of isotopic exchange between it and the hydroxyl group, may not be possible in all instances (Lawrence and Taylor 1971). 

Suspensions and colloidal dispersions differ from true solutions in that they are systems with more than one phase. This means that the substances present do not mix very well. The system is said to be heterogeneous and is characterized by interfaces between the phases, for instance between the water and a clay particle in muddy water. However, true solutions are one-phase systems and as a result homogeneous. In addition, they differ because in suspensions and dispersions the solid phase can be separated by means of filtration. 

N. Yan and J. H. Masliyah, Characterization and demulsification of solids-stabilized oil-in-water emulsions. Part 1. Partitioning of clay particles and preparation of emulsions, Colloids Surf. A 96, 229-242 (1995). 

Electrokinetic phenomena are generally characterized by the tangential motion of liquid with respect to an adjacent charged surface. In the above example the surface was that of a negatively charged clay particle the particle moved with respect to the stationary liquid. The surface may also be that of a droplet as in emulsions. Alternatively, the particles may be stationary with the liquid moving, as for Instance in electro-osmosis. For sand this phenomenon was also discovered by Reuss I... 

The climatic conditions and episodic flooding that characterized the depositional setting of the Lunde enhanced the infiltration of suspended clay particles and the formation of coatings around framework grains in the sandstones. Clay minerals formed by weathering processes in the hinterlaixl under arid to semi-arid climatic conditions would be expected to... 

Pd-hexadecylammonium montmorillonite (Pd-HDAM) catalysts have been prepared by a novel synthetic route. Sample characterization including XRD and TEM measurements confirmed the existence of interlayer Pd nanocrystallites which occupy clay particle defect sites. The catalytic activities of Pd-HDAM samples were tested by hydrogenation of 1-octene and styrene in the liquid phase. The reaction of styrene was found to be less dependent on the dispersion of Pd than that of 1-octene. The highest activities were observed for samples of low and medium Pd content. The application of various solvents made it pos le to establish a correlation between the activities and the basal spacings dL of Pd-HDAM samples. When the value of dL exceeded 3 ran, interlamellar active sites became more accessible for reactants. 

Eventually, the average masses N(t) and 5(0 depend on the mass value affected to each aggregate constituent. For monosized latex particles the mass 1 is attributed to single particles. When, as for oxides and clays, the original colloid is polydisperse in mass and size, the mass 1 is attributed either to particles of diameter d, of the smallest constituent (as for aluminum oxide) or to particles characterized by the average diameter dn given by the counter (as for the kaolinite clay). This choice only affects the absolute values of 5(f) or N(t) but does not modify the exponents of the power laws used to express fragmentation and breakup rates. 

Table 2 presents the PSD of the binary models obtained by reaction of clay or polyphenol with Al- or Fe- polymers. Both Al- and Fe- were able to cement clay particles with initial size < 2 pm, into small packets with particle size prevailingly ranging from 5 to 15 pm. However, the C-Al packets are characterized by a noticeable dimensional homogeneity, since most of particles (70.5%) lies in the size range of 5-10 pm. Differently, the size of the C-Fe packets is more widely distributed between 5 (50.1%) and 15 (41.6%) pm. 

However, there are few reports on chitosan/bentonite nanocomposites (Yang Chen, 2007 Zhang et al., 2009 Wan Ngah et al., 2010). The physical properties and biological response of chitosan strongly depend on the starting materials and nanocomposite preparation conditions. In the present study chitosan/day nanocomposites were prepared using two kinds of clay and different chitosan/day ratios, to evaluate how these variables affect the dispersion of clay particles into the chitosan matrix. The samples obtained were characterized by infrared spectroscopy, x-ray diffraction, and mechanical (tensile) properties. 

The high-resolution characterization of the various rectorite samples was performed at 200 and 400 Kv in a Jeol-2000 electron microscope. The analytical microscopy was performed in a Jeol-lOOCX machine fitted with a Tracor Northern 5500 x-ray detector. Samples were embedded in resin (6, 7) and microtomed in the direction perpendicular to the basal planes (8). The parent rectorite was intercalated with tetrapropylammonium bromide solutions (TPA-Br) to improve the clay stability in the microscope column. The pillared rectorite was instead dispersed in isopropyl alcohol the clay particles were then separated by ultrasonification and deposited onto copper grids. 

Furthermore, the results helped to characterize how nucleic acid molecules are adsorbed on clay minerals including kaolinite [28, 29], For example, double stranded DNA molecules that differ in their guanine-cytosine content were adsorbed in equal amounts by clays including kaolinite [49]. Linear DNA was revealed to be adsorbed on illite and kaoUnite to a greater extent than on montmorillonite [60]. This emphasizes the influence that positive charges of the lattice edges and the microorganization of clay particles have on the mechanism of DNA adsorption. 

The solvent-removal technique will also influence the mutual orientation of the aniso-metric clay particles (either single layers or thin tactoids). Precipitation in a non-solvent, or freeze drying, will expectedly yield composites with randomly oriented clay platelets. On the other hand, the composites prepared by film casting, or multilayer film casting [22,23], will be characterized by the preferred orientation of such platelets parallel to the film surface. This particular morphology can be of interest, e.g., in view of the production of films with enhanced barrier properties. 

To favor MAO fixation on the clay particles and to minimize the deactivation effects by the OH groups of the silicate surface on zirconocene catalyst activity in the subsequent polymerization step, the layered filler C15A was first stirred in toluene and then reacted with MAO for different contact times (C15A/MAO). The intermediates were isolated by filtration and characterized. 

The result of microbiological activity is characterized by the increase of microorganisms cells number and products of their metabolism of protein and non-protein nature. These microorganisms and its products due to their minor sizes (comparable with the size of clay particles), as well as due to the fact, that the cell is charged, are actively sorbed by mineral particles of soils, thus, creating biofilms. 

Characterization of Nanocomposite Microstructure. Mixing clay with a polymer does not necessarily lead to a nanocomposite. Elaboration strategies are aimed at monitoring dispersion of the inorganic compound at the nanometer level, that is down to the elementary clay platelet. Figure 2 provides a schematic illustration of the various microstructures readily achievable, namely a conventional fllled polymer with clay particles in the micrometer range, an... 

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