Calcium-magnesium-alumina-silicate

There were certain hopes on calcium and magnesium alumina silicate as possible barrier layers, preventing interactions of refractories with electrolyte [194-197]. These minerals are a little more expensive than alumina silica refractories, but the cost is not sufficiently bigger. The basis for these hopes was the fact that the products of interactions of anortite (CaAl2SiOg), forsterite (MgSi04), and ohvinite with sodium fluoride will have the freezing points above 900 °C, and the melts will crystallize [194,195]. 

The most commonly employed fillers in plasticized PVC are the precipitated forms of calcium carbonate (CaCOy) and related minerals such as dolomite (calcium magnesium carbonate). CaCOj fillers are diroated with fatty acids to improve physical properties of PVC, particularly flex life and elongation at break. The effect of calcium carbonate fillers on fusion properties of PVC is reviewed (47). Other fillers include china clay, calcined clay, asbestos, barytas, talc, alumina and kieselguhr and silicates. Micaceous-talc fillers in PVC which are polyblended with acrylonitrile rubber shows an extraordinary effect. Small amounts improve elongation and energy to break. 

X-ray Diffraction Analysis. The inorganic components of paper are the most suitable ones for quantitative X-ray diffraction analysis. Most of these compounds are minerals and are present as fillers, coatings and pigments (often whiteners) which are added to improve the properties of the paper. Examples of compounds commonly added to paper are alumina, aluminum silicate, barium sulfate, calcium carbonate, calcium sulfate, calcium sul-foaluminate, iron oxide, magnesium silicate, silica, titanium dioxide, zinc oxide, and zinc sulfide (28). Some of these, e.g., calcium carbonate and titanium dioxide, may be present in any of... 

The crystallites in alumina ceramics are mainly oc-A1203, mineralogically known as corundum (a synonym for sapphire). Corundum is 9 on the Mohs scale of hardness, i.e. it is next hardest to diamond, at 10. Examples of the micro structures of a high-purity alumina and a debased alumina are shown in Figs 5.20(a) and 5.20(b) respectively. The latter consists of a-Al203 crystallites embedded in a glass-crystalline matrix usually composed of calcium and magnesium silicates. 

Silica gel and silicic acid are also generally useful adsorbents and are comparable to alumina in their adsorptive power. Silica gel is particularly useful for partition chromatography, described on page 164. Magnesium oxide, calcium carbonate, and similar compounds are less effective adsorbents and are useful for compounds which are too strongly adsorbed by the previously mentioned adsorbents. 

The hydrated lime then reacts with the reactive silica and alumina to produce hydrated calcium and magnesium silicates and aluminates. The cement also hydrates completely. 

Impurities of major significance in alkali silicates are iron, alumina, calcium and magnesium, chloride, sulfate, carbonate and titania. They may originate as impurities in raw materials, be added from the manufacturing equipment, or be absorbed from the atmosphere. The degradation of product quality may be manifested as undesirable color, turbidity in solution, corrosiveness, loss of alkalinity or altered reactivity of products made from the silicate (e.g., iron or sulfate may poison a silica-based catalyst manufactured from a silicate solution). 

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