Kaolin Chemical composition

Talc [14807-96-6], a naturally occurring mineral of the general chemical composition Mg2Si40 Q(0H)2, is a crystalline hydrous magnesium siUc ate belonging to the general mineral family of the layered siUcates. Other layered siUcates are kaolin, mica, and pyrophyUite (1). 

Attention will be focused on two clay mineral groups kaolin and montmorillonite. Both groups have layered structures consisting of parallel sheets of oxide and hydroxide ions coordinated to Si4+ and Al3+ ions (233). Differences in the arrangement of the sheets and in their chemical composition give rise to the division into two groups. Within each group are several minerals of similar structure and composition. 

North Carolina kaolin has the following chemical composition silicon dioxide, Si02,46.18% aluminum oxide, A1203, 38.38% water, H20, 13.28% sodium oxide, Na20, 1.22% iron oxide, Fe203,. 57% and magnesium oxide, MgO,. 42%. 

Table 1. Chemical composition, weight %, of the parent kaolin and leached samples from MK-600 series.

The SEM micrographs of the kaolin and metakaolins show plate shape particles for both types of solids (Figure 3a). Calcination of the kaolin produces its dehydroxylation but does not destroy its platy shape. For samples treated under reflux conditions the plates are dissolved and the micrographs (Fig 3b,c) show amorphous particles that coexist with the metakaolin plates. There are not many differences between the samples activated at different times, although the chemical composition indicated that the amount of Al removed by activation for 24 h was higher than during activation for 6 h. 

Because several spatial stacking arrangements are possible there are several kaolin minerals, each with the same chemical composition, namely Al2Si205(0H)4, but with different properties. Nacrite, dickite, kaolinite, halloysite, and livesite are well recognized species. No positive evidence has so far been published linking other trivalent cations with a single layer lattice structure, but it has been suggested that iron(iii) can replace aluminium in part in the kaolin lattice. 

Porcelains are classified according to their chemical composition as well as on the basis of their firing temperatures. The hard porcelain, favored in Mid-Europe for the manufacture of utensils and technical articles, is produced from classical mixtures consisting of 50% kaolin, 25% feldspar and 25% quartz and are fired at 1380 to 1460°C. The thermal shock resistance, particularly required for chemical apparatus porcelains and cooking utensils, can be increased by reducing the quartz content, but at the expense of transparency. 

In contrast with pure aluminum oxide ceramics, the raw materials used in the manufacture of alumina-rich refractory products are, for economic reasons, natural products. The choice of aluminum silicates cyanite, andalusite or sillimanite (chemical composition Al203-Si02) or low iron bauxite with an AbOj-content > 85% and a Si02-content < 10%, depends upon the aluminum oxide content required. Natural mixtures of alumina hydrates (bauxite) and kaolin with Al203-contents of 48 to 70% are fired to so-called mullite chamottes. To obtain still higher AbO -contents, industrially produced corundum has to be added. 

Conceptually, the next simplest clay mineral is pyrophyllite, which is produced by attaching tetrahedral sheets above and below an octahedral layer (Fig. 6), compared with just one octahedral sheet for kaolin [15]. The resulting chemical composition of pyrophyllite is AI2Si4Ol0(OH)2, which is equivalent to the mineral formula Al20 4Si02-II20. The structure and properties of pyrophyllite are summarized in Table 2. 

Since LSX and A zeolite have the same overall chemical composition and both are constructed by linking sodallte cages, we postulated that preformed metakaolln could be converted directly to LSX. Several reports show that kaolin-type clays can be transformed to X- or Y-type zeolites having S1/A1 ratios exceeding 1.2 by either adding silica to or removing alumina from the metakaolln.(7-9) In each case, without addition of silica or deletion of alumina, only A zeolite 1s formed. 

Bonds with plastics, 142 Calcium carbonate in, 112, 141 Cellulose in, 112 Chemical composition, 112 Cost of, 112 Granules, 141 Ingredients, 141 Kaolin clay in, 112 Mold shrinkage, effect on, 142 Oil absorption, 141 Porosity, 141 Shape of particles, 142 Speciflc gravity, 142 Tensile modulus, effect on, 142, 143 Thermal expansion-contraction coefficient, 142 Biodegradable plastics, 79 Biodegradable wood-plastic composites, 91 Bioresistance, 42 Biotite, 146 Black Algae, 426 Black mold, 29, 31, 424, 429 Black panel temperature, 41, 132 Black panel thermometer, 612 Black panel, 41, 132 Bleached cellulose, 11, 14, 180 Cost, 14... 

Abrasion resistance, effect on, 146 Chemical composition, 146 Density, 146 Kaoilinite, 146 Mohs hardness, 146 Moisture content, 146 Montmorillolinite, 146 Oil absorption, 146 Specific gravity, 146 Surface area, 146 Vermiculite, 146 Kaolin, 80, 125, 128, 129, 133 Kaolinite, 146... 

The identification of polymers by FTIR is often complicated by the presence of fillers. However for kaolin clay, an FTIR analysis should be able to identify the filler and predict its concentration using a standard curve. The resulting percentage is more reliable than a simple ash, which may change the chemical composition of the filler. 

Clays are classified on the basis of their crystal structure and the amount and locations of elelectric charge (defidt or excess) per unit cell. Crystalline days range from kaolins, which are relatively uniform in chemical composition, to smectites, which vary in their composition, cation exchange p>rop>erties, and ability to expand. The most commonly employed smectite clay for the preparation of polymeric nanocomposites is bentonite, whose main mineral component is montmorillonite (Utracki, 2004). 

Typical chemical compositions of hydrous and calcined kaolins are shown in Table 13.1 [8]. The major effeds of the removal of water of hydration are an increase in refradive index, a moderate increase in the otherwise low Mohs hardness, a decrease or increase in spedfic gravity depending on the extent of caldnation, and a decrease in dieledric constant (Table 13.2) [8]. The calcined materials, due to their higher void structure, are capable of considerably higher oil absorption, as indicated in Table 13.3, which also includes comparisons of additional properties of various... 

Table 13.1 Typical chemical composition %) of water-washed hydrous and calcined kaolin [8].

Clay, mainly Kaolin is used in pigment to form it as a paste like material, by increasing its density. The important features of kaolin elay are its purity, high brightness, easy dispersion, accurate chemical composition and capacity to withstand high temperature. 

Keywords filler, aspect ratio, particle shape, calcium carbonate, talc, platelets, reinforcement, glass fiber, kaolin, particle size, particle size distribution, chemical composition, adhesion, interface, aggregation, specific surface area, flow-induced orientation, hardness, surface free energy, surface tension, surface treatment, mechanical properties, thermal properties. 

The paste used to manufacture stonewares tiles generally consists of a mixture of plastic clays, kaolin, feldspathic sand, sodium or potassium feldspar and small quantities of talc, dolomite and/or chlorite. The overall chemical composition of the... 

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