Magnesia graphite

Typically, Be-containing alloys and intermetallic phases have been prepared in beryllia or alumina crucibles Mg-containing products have been synthesized in graphite, magnesia or alumina crucibles. Alloys and compounds containing Ca, Sr and Ba have been synthesized in alumina , boron nitride, zircon, molybdenum, iron , or steel crucibles. Both zircon and molybdenum are satisfactory only for alloys with low group-IIA metal content and are replaced by boron nitride and iron, respectively, for group-IIA metal-rich systems . Crucibles are sealed in silica, quartz, iron or steel vessels, usually under either vacuum or purified inert cover gas in a few cases, the samples were melted under a halide flux . 

Metal-support interactions can be defined as being weak, medium or strong.28 Non-reducible metal oxides such as silica, alumina, and magnesia as well as carbon or graphite are considered to exert only a weak influence on the metal and, thus, exhibit only a weak metal-support interaction (WMSI). Zeolites (Chapters 10 and 13) exert a medium metal-support interaction (MMS1)28 while metals supported on reducible oxides when reduced at high temperatures exhibit a strong metal-support interaction (SMSI).27-32... 

Fig. 1.18. Cell for three-layer refining 1-cathode bus bar, 2-cathode hanger, 3-graphite cathode, 4-refininged metal, 5-electrolyte, 6-anode alloy, 7-forewell, 8-refractory lining (magnesia), 9-refractory lining (chamotte), 10-steel shell, 11-adode connection, 12-anode buss bar, 13-C bottom (ref]...

Chemical composition silica-based and silica-alumina-based materials, chrome, magnesia, chrome-magnesia, spinel, SiC, materials containing carbon (more than 1% carbon or graphite), and special materials (containing other oxides or materials such as zircon, zirconia, Si3N4, etc.)... 

Bone and Coward 21 found float the rate of decomposition of methane in the presence of porcelain was very low at temperatures below 700° C. Large surface exposure promoted the reaction, which apparently was reversible. Using as a basis the amount of dissociation in an empty tube Slater 82 found that silica, magnesia, alumina and baryta did not accelerate the reaction, and that copper, carborundum, graphite, charcoal, and iron did. The temperatures were between 900° and 1000° C., rather high for good comparison of catalytic surfaces. 

Friction modifiers inelude inorganie fiietion modifiers such as alumina, silica, magnesia, zireonia, chrome oxide, or quartz and organic fiietion modifiers sueh as synthetie rubber or eashew dust. Graphite, or molybdenum disulfide serve as solid lubrieants. Copper fiber increases the thermal conductivity of the formulation. 

The cell which holds the molten salt and metal can be made of a variety of materials, such as iron, graphite, fire brick, alumina, magnesia, molybdenum or tantalum. The cathode is usually molybdenum, tantalum or tungsten and sometimes iron, cobalt or nickel. The choice of the cell and cathode materials will depend on the product desired. Graphite is almost always the choice for the anode because it is relatively inert to the halide gases (F2 or CI2) or oxygen liberated at this electrode. 

Refractories. Aluminosilicates, silica and aluminous material, basic materials such as magnesite, chrome-bearing materials such as magnesia-chrome bricks, zirconia-bearing materials, and silicon carbide. There are also raw materials such as fireclay, ferrosilicon, and graphite. 

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