Magnesia carbon

Goap" is the name given to the crude intermediate product obtd in the manuf of magnesium at the Henry Kaiser plant. It consists of a mixt of ultrafine particles of Mg, Mg carbide, magnesia, carbon, naphtha asphalt, all in the form of thick paste. The material proved to be a suitable source of Mg in prepn of incendiary compns for bombs. The most successful of such mixtures was known during WWlI asPyrogel or PT-1... 

Carbonate of magnesia, Carbonate of potassa, Carbonate of sods, ... 

Catalytic reductions have been carried out under an extremely wide range of reaction conditions. Temperatures of 20 C to over 300 C have been described. Pressures from atmospheric to several thousand pounds have been used. Catal3rsts have included nickel, copper, cobalt, chromium, iron, tin, silver, platinum, palladium, rhodium, molybdenum, tungsten, titanium and many others. They have been used as free metals, in finely divided form for enhanced activity, or as compounds (such as oxides or sulfides). Catalysts have been used singly and in combination, also on carriers, such as alumina, magnesia, carbon, silica, pumice, clays, earths, barium sulfate, etc., or in unsupported form. Reactions have been carried out with organic solvents, without solvents, and in water dispersion. Finally, various additives, such as sodium acetate, sodium hydroxide, sulfuric acid, ammonia, carbon monoxide, and others, have been used for special purposes. It is obvious that conditions must be varied from case to case to obtain optimum economics, yield, and quality. 

Antidotes.—Carbonate of lime (chalk or whiting) magnesia carbonate of magnesia demulcent drinks large draughts of water. 

Industrial applications and uses. Major industrial applications for borides include, but are not restricted to, machining and cutting tools abrasives for grinding, lapping, or polishing heat-resistant shields in aerospace appHcations fiber reinforcement of composites (e.g., MMCs, CMCs) shields and bulletproof shields for military appHcations antioxidant additives in alumina or magnesia-carbon bricks neutron shields in nuclear reactors and nozzles. 

Dead burned magnesia with chromite Fused magnesia Magnesia-carbon bricks... 

One further point about the need to keep the iron oxide content of MgO grains low. In the presence of carbon in magnesia-carbon refractories, iron oxide reacts with carbon therefore, this carbon oxidation-iron oxide reduction reaction contributes to the loss of carbon from the refractory, an undesirable effect that is explored in a later section. 

Carbon, in any form, plays a vital role in minimizing the penetration of steelmaking slags into the microstructure of magnesia-carbon refractories at the same time, MgO becomes incompatible with carbon at these same steel-making temperatures. This incongruity is discussed below. 

The thermodynamics of these magnesia-carbon-metal reactions are thoroughly discussed by Rymon-Lypinski (43,44). 

Some examples of post-treatments are (1) burned magnesia brick may be subsequently pitch-impregnated prior to use (2) brick for cement kilns may have cardboard spacers glued on one or two brick faces and (3) resin-bonded magnesia-carbon brick may be subjected to a heating cycle and then pitch-impregnated. 

Table 11 Selected Properties of Some Widely Used Magnesia-Carbon Brick...

As seen from the many applications just described, refractory manufacturers produce a wide range of magnesia products with a spectrum of chemical and physical properties. Table 11 (67) depicts selected properties for several widely used magnesia-carbon brick types, while Table 12 (68) shows selected properties for an assortment of other popular magnesia refractory bricks. 

As an example, Figure 10.11 shows a stress-deformation experimental curve of a magnesia carbon refractory. 

ROB 98] ROBIN J.M., BERTHAUD Y., SCHMITT N., POIRIER J., THEMINES D., Thermomechanical behaviour of magnesia-carbon refractories , British Ceramic Transactions, vol. 97, no. 1,1998. 

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