Particles platelike

The slit-shaped model has come into prominence in recent years, as electron microscopy has revealed the prevalence of solids composed of platelike particles the technique, indeed, has now developed to the point where it is possible to identify the presence of slit-shaped pores, and even to measure their width. In the ideal case where the sides of the slit are truly planar and parallel, the hysteresis takes an extreme form since the mean radius of curva-... 

Illite and other 2 1 layer type clay minerals. Platelike particles stacked irregularly... 

Several investigators have used radioactive tracer methods to determine diffusion rates. Bangham et al. (32) and Papahadjopoulos and Watkins (33) studied transport rates of radioactive Na+, K+, and Cl" from small particles or vesicles of lamellar liquid crystal to an aqueous solution in which the particles were dispersed. Liquid crystalline phases of several different phospholipids and phospholipid mixtures were used. Because of uncertainties regarding particle geometry and size distribution, diffusion coefficients could not be calculated. Information was obtained, however, showing that the transport rates of K+ and Cl" in a given liquid crystal could differ by as much as a factor of 100. Moreover, relative transport rates of K+ and Cl" were quite different for different phospholipids. The authors considered that ions had to diffuse across platelike micelles to reach the aqueous phase. 

Most pigments and extenders used in paints are crystalline in nature. Particles may be tetragonal, rhombic, cubic, nodular, rod-like, or platelike. Noncrystalline pigments such as the carbon blacks are also used in the paint industry. As particle shape affects pigment packing, it also affects its hiding power. 

Fig. 11. Classification of adsorption-desorption hysteresis loops. HI are typical for materials containing agglomerates and for materials with cylindrical pore geometry and a high degree of pore size uniformity. The type H2 is characteristic of materials with relatively uniform channel-like pores with the pore connectivity effects. H3 type is attributed to aggregates (loose assemblages) of platelike particles forming slitlike pores. The type H4 loop is proposed to be attributed to large mesopores embedded in a matrix with pores of much smaller size. Reprinted with permission from [76]. Copyright (2001) American Chemical Society...

Unless they are smoothed by abrasion after crushing, comminuted particles resemble polyhedrons with nearly plane faces and sharp edges and corners. The particles may be compact, with length, breadth, and thickness nearly equal, or they may be platelike or needlelike. For compact grains, the largest dimension or... 

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