Clay mass

FIGURE 51 Drying clay. The illustration shows a schematic, highly magnified cross section of a mass of wet clay at three different levels of water contents. Initially, all the space around the clay particles is filled with water (a). As the wet mass dries up, water is lost from between the particles, which gradually come nearer to each other (b), and the clay mass shrinks in size. When all the water has evaporated, the particles are in contact with each other and the mass cannot shrink any further (c). From this point onward the bulk volume of the clay mass does not change. 

A clay mass is a mixture of clay and additives for a specific ceramic (processing) technique. The clay provides the plastic properties. Possible additives are a flux and a filler. Some examples of fluxes are potassium feldspar, bone meal, volcanic ashes and ground glass, all of which serve to affect the density and decrease the melting range. Fillers reduce the shrinkage as well as the sticky character of the clay. 

In the extrusion process the plastic clay mass is forced through a die by a screw mechanism (figure 9.12). 

For the synthesis of insulation materials organic substances are added to the clay mass. During the firing the combustion products from those substances are responsible for the formation of cavities in the material. 

A stamping press is used in the manufacture of roof tiles. This is a machine which compresses a plastic clay mass between two moulds to obtain the desired shape. This compression technique is only rarely applied in coarse ceramics. 

The differences in sorptive behavior of Th, Pu, U, and Np are evident by examining Table II. Plutonium and thorium isotopes at tracer concentrations (parts per billion, element mass/clay mass) were equilibrated for 24 hours with the < 2-pm fraction (clay) of a silt loam soil. The pH of the equilibration solutions was 6.5 and the aqueous phase contained Ca at a concentration of 5 mM. Both tetravalent actinides failed to remain 1n solution. Whether this is a direct function of sorption mechanisms or simply related to the solubility of the ions in solution is not distinguished by the results. Uranyl ion was not removed to the same extent as the tetravalent species. Neptunium(V) sorbed very poorly. It should be noted that while Np(V) is a mono-charged cation, Np02+ does not sorb like Na+. 

The Rh (III)/ clay dispersion modified with pillaring agent was centrifuged and washed six times with distilled water and air dried at 80°C. The catalyst precursor namely Rh (phen)3 in the form of dry clay mass, was then crushed into a powder and calcined at 450°C for 4 hours in air. This was subsequently reduced at 350°C under a flow of hydrogen for 8 hours. A known amount of catalyst was digested in aqua regia for 16 hours and filtered. The filtrate was quantitatively made up to a known volume. The Rh content in this solution was measured by Atomic Absorption Spectroscopy (GBC Model 932). The value so obtained (1.5 %) matched with the theoretical value. 

From studies of granitic sites, the dominant role of fractures and fissures in the transport of fluids has been convincingly demonstrated. Thus any model of water in a granitic site must include both advection which is dominant in the fractures and fissures, and diffusion which is important in regions of highly altered rocks ("alteration rims"). In clays, mass... 

Composition Mass (%) Ball Clay Mass (%) Glasses... 

The new class of polymer materials, organic- inorganic (clay) nanocomposites, was also reported as an excellent FR composition [234]. Nylon-6 clay nanocomposites, first developed by Toyota Central Research and Development Laboratories, are materials with unique properties. The nylon- 6 clay nanocomposites (clay mass fraction from 2%-70%) are synthesized by ring - opening polymerization of e-caprolactam in the presence of cation exchanged montmorillonite clay [235]. 

This process creates a polymer-layered silicate nanocomposite with the either a delaminated hybrid structure or an intercalated one. The intercalated structure, which forms when the mass fraction of clay is greater than 20%, is characterized by a well ordered multilayer with spacing between the silicate layers of only a few nanometers. The delaminated hybrid structure, which forms when the mass fraction of clay is less than 20%, contains the silicate layers individually dispersed in the polymer matrix. The thermal, mechanical and FR properties of nylon-6 clay nanocomposite with only 5% of clay fraction show excellent improvements over nylon 6. In the paper by Gilman it was pointed out that cone calorimeter data show the reduction of RHR (max.) by 63% in a nylon,6/clay nanocomposite containing a clay mass fraction of only 5% [233]. This nanocomposite has the same heat of combustion as the pure nylon-6. 

Run no. Initial clay loading (g) Polymerization time (h) Activity (kgpE/ molv h atm) Clay mass fraction (wt%) Extracted in decalin (%) Temperature for 5 wl% loss (°C) Temperature for 10 wt% loss (°C)... 

Geomembrane mass 9.39 tons Clay mass 20,000 tons... 

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